DO NOT MERGE: Add hacky poller method for testing discovery.

Discovery finishes quickly on some devices if called at the wrong time.

bramble-android/build.gradle

@@ -38,7 +38,7 @@ configurations {
 
 dependencies {
 	implementation project(path: ':bramble-core', configuration: 'default')
-	tor 'org.briarproject:tor-android:0.3.5.10@zip'
+	tor 'org.briarproject:tor-android:0.3.5.9@zip'
 	tor 'org.briarproject:obfs4proxy-android:0.0.11-2@zip'
 
 	annotationProcessor 'com.google.dagger:dagger-compiler:2.24'

bramble-android/src/main/java/org/briarproject/bramble/plugin/bluetooth/AndroidBluetoothPlugin.java

@@ -8,29 +8,39 @@ import android.content.BroadcastReceiver;
 import android.content.Context;
 import android.content.Intent;
 import android.content.IntentFilter;
+import android.os.ParcelUuid;
+import android.os.Parcelable;
 
-import org.briarproject.bramble.api.io.TimeoutMonitor;
+import org.briarproject.bramble.api.Pair;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
+import org.briarproject.bramble.api.plugin.Backoff;
+import org.briarproject.bramble.api.plugin.DiscoveryHandler;
 import org.briarproject.bramble.api.plugin.PluginCallback;
 import org.briarproject.bramble.api.plugin.PluginException;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
+import org.briarproject.bramble.api.properties.TransportProperties;
 import org.briarproject.bramble.api.system.AndroidExecutor;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.util.AndroidUtils;
 import org.briarproject.bramble.util.IoUtils;
 
 import java.io.IOException;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.nio.ByteBuffer;
 import java.security.SecureRandom;
 import java.util.ArrayList;
-import java.util.Collection;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.TreeSet;
 import java.util.UUID;
 import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.Executor;
 import java.util.concurrent.LinkedBlockingQueue;
-import java.util.concurrent.ScheduledExecutorService;
 import java.util.logging.Logger;
 
 import javax.annotation.Nullable;
@@ -47,15 +57,25 @@ import static android.bluetooth.BluetoothAdapter.SCAN_MODE_NONE;
 import static android.bluetooth.BluetoothAdapter.STATE_OFF;
 import static android.bluetooth.BluetoothAdapter.STATE_ON;
 import static android.bluetooth.BluetoothDevice.ACTION_FOUND;
+import static android.bluetooth.BluetoothDevice.ACTION_UUID;
 import static android.bluetooth.BluetoothDevice.DEVICE_TYPE_LE;
 import static android.bluetooth.BluetoothDevice.EXTRA_DEVICE;
+import static android.bluetooth.BluetoothDevice.EXTRA_UUID;
 import static android.os.Build.VERSION.SDK_INT;
+import static java.nio.ByteOrder.LITTLE_ENDIAN;
+import static java.util.Arrays.asList;
+import static java.util.Collections.emptyList;
 import static java.util.Collections.shuffle;
 import static java.util.concurrent.TimeUnit.MILLISECONDS;
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
+import static org.briarproject.bramble.api.nullsafety.NullSafety.requireNonNull;
+import static org.briarproject.bramble.api.plugin.BluetoothConstants.PROP_ADDRESS;
+import static org.briarproject.bramble.api.plugin.BluetoothConstants.PROP_UUID;
+import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.bramble.util.PrivacyUtils.scrubMacAddress;
+import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
@@ -64,9 +84,10 @@ class AndroidBluetoothPlugin extends BluetoothPlugin<BluetoothServerSocket> {
 	private static final Logger LOG =
 			getLogger(AndroidBluetoothPlugin.class.getName());
 
-	private static final int MAX_DISCOVERY_MS = 10_000;
+	private static final int MIN_DEVICE_DISCOVERY_MS = 2_000;
+	private static final int MAX_DEVICE_DISCOVERY_MS = 30_000;
+	private static final int MAX_SERVICE_DISCOVERY_MS = 15_000;
 
-	private final ScheduledExecutorService scheduler;
 	private final AndroidExecutor androidExecutor;
 	private final Context appContext;
 	private final Clock clock;
@@ -78,14 +99,11 @@ class AndroidBluetoothPlugin extends BluetoothPlugin<BluetoothServerSocket> {
 	private volatile BluetoothAdapter adapter = null;
 
 	AndroidBluetoothPlugin(BluetoothConnectionLimiter connectionLimiter,
-			TimeoutMonitor timeoutMonitor, Executor ioExecutor,
+			Executor ioExecutor, AndroidExecutor androidExecutor,
-			SecureRandom secureRandom, ScheduledExecutorService scheduler,
+			Context appContext, SecureRandom secureRandom, Clock clock,
-			AndroidExecutor androidExecutor, Context appContext, Clock clock,
+			Backoff backoff, PluginCallback callback, int maxLatency) {
-			PluginCallback callback, int maxLatency, int maxIdleTime,
+		super(connectionLimiter, ioExecutor, secureRandom, backoff, callback,
-			int pollingInterval) {
+				maxLatency);
-		super(connectionLimiter, timeoutMonitor, ioExecutor, secureRandom,
-				callback, maxLatency, maxIdleTime, pollingInterval);
-		this.scheduler = scheduler;
 		this.androidExecutor = androidExecutor;
 		this.appContext = appContext;
 		this.clock = clock;
@@ -142,12 +160,31 @@ class AndroidBluetoothPlugin extends BluetoothPlugin<BluetoothServerSocket> {
 	@Override
 	void disableAdapterIfEnabledByUs() {
 		if (isAdapterEnabled() && wasEnabledByUs) {
+			cancelDiscoverability();
 			if (adapter.disable()) LOG.info("Disabling Bluetooth");
 			else LOG.info("Could not disable Bluetooth");
 			wasEnabledByUs = false;
 		}
 	}
 
+	private void cancelDiscoverability() {
+		if (adapter.getScanMode() == SCAN_MODE_CONNECTABLE_DISCOVERABLE) {
+			try {
+				Method setDiscoverableTimeout = BluetoothAdapter.class
+						.getDeclaredMethod("setDiscoverableTimeout", int.class);
+				setDiscoverableTimeout.setAccessible(true);
+				setDiscoverableTimeout.invoke(adapter, 1);
+				LOG.info("Cancelled discoverability");
+			} catch (NoSuchMethodException e) {
+				logException(LOG, WARNING, e);
+			} catch (IllegalAccessException e) {
+				logException(LOG, WARNING, e);
+			} catch (InvocationTargetException e) {
+				logException(LOG, WARNING, e);
+			}
+		}
+	}
+
 	@Override
 	void setEnabledByUs() {
 		wasEnabledByUs = true;
@@ -183,10 +220,9 @@ class AndroidBluetoothPlugin extends BluetoothPlugin<BluetoothServerSocket> {
 		return wrapSocket(ss.accept());
 	}
 
-	private DuplexTransportConnection wrapSocket(BluetoothSocket s)
+	private DuplexTransportConnection wrapSocket(BluetoothSocket s) {
-			throws IOException {
+		return new AndroidBluetoothTransportConnection(this,
-		return new AndroidBluetoothTransportConnection(this, connectionLimiter,
+				connectionLimiter, s);
-				timeoutMonitor, appContext, scheduler, s);
 	}
 
 	@Override
@@ -214,7 +250,8 @@ class AndroidBluetoothPlugin extends BluetoothPlugin<BluetoothServerSocket> {
 	@Nullable
 	DuplexTransportConnection discoverAndConnect(String uuid) {
 		if (adapter == null) return null;
-		for (String address : discoverDevices()) {
+		for (BluetoothDevice d : discoverDevices()) {
+			String address = d.getAddress();
 			try {
 				if (LOG.isLoggable(INFO))
 					LOG.info("Connecting to " + scrubMacAddress(address));
@@ -230,10 +267,184 @@ class AndroidBluetoothPlugin extends BluetoothPlugin<BluetoothServerSocket> {
 		return null;
 	}
 
-	private Collection<String> discoverDevices() {
+	@Override
-		List<String> addresses = new ArrayList<>();
+	public boolean supportsDiscovery() {
+		return true;
+	}
+
+	@Override
+	public void discoverPeers(
+			List<Pair<TransportProperties, DiscoveryHandler>> properties) {
+		// Discover all nearby devices
+		List<BluetoothDevice> devices = discoverDevices();
+		if (devices.isEmpty()) {
+			LOG.info("No devices discovered");
+			return;
+		}
+
+		List<Pair<TransportProperties, DiscoveryHandler>> discovered =
+				new ArrayList<>();
+		Map<String, Pair<TransportProperties, DiscoveryHandler>> byUuid =
+				new HashMap<>();
+		Map<String, Pair<TransportProperties, DiscoveryHandler>> byAddress =
+				new HashMap<>();
+		for (Pair<TransportProperties, DiscoveryHandler> pair : properties) {
+			TransportProperties p = pair.getFirst();
+			String uuid = p.get(PROP_UUID);
+			if (!isNullOrEmpty(uuid)) {
+				byUuid.put(uuid, pair);
+				String address = p.get(PROP_ADDRESS);
+				if (!isNullOrEmpty(address)) byAddress.put(address, pair);
+			}
+		}
+
+		List<BluetoothDevice> unknown = new ArrayList<>(devices);
+		for (BluetoothDevice d : devices) {
+			Pair<TransportProperties, DiscoveryHandler> pair =
+					byAddress.remove(d.getAddress());
+			if (pair == null) {
+				// Try cached UUIDs
+				for (String uuid : getUuids(d)) {
+					pair = byUuid.remove(uuid);
+					if (pair != null) {
+						if (LOG.isLoggable(INFO)) {
+							LOG.info("Matched "
+									+ scrubMacAddress(d.getAddress())
+									+ " by cached UUID");
+						}
+						TransportProperties p =
+								new TransportProperties(pair.getFirst());
+						p.put(PROP_ADDRESS, d.getAddress());
+						discovered.add(new Pair<>(p, pair.getSecond()));
+						unknown.remove(d);
+						break;
+					}
+				}
+			} else {
+				if (LOG.isLoggable(INFO)) {
+					LOG.info("Matched " + scrubMacAddress(d.getAddress())
+							+ " by address");
+				}
+				discovered.add(pair);
+				unknown.remove(d);
+			}
+		}
+		if (unknown.isEmpty()) {
+			LOG.info("All discovered devices are known, not fetching UUIDs");
+			return;
+		}
+		// Fetch up-to-date UUIDs
+		if (LOG.isLoggable(INFO))
+			LOG.info("Fetching UUIDs for " + unknown.size() + " devices");
 		BlockingQueue<Intent> intents = new LinkedBlockingQueue<>();
-		DiscoveryReceiver receiver = new DiscoveryReceiver(intents);
+		QueueingReceiver receiver = new QueueingReceiver(intents);
+		IntentFilter filter = new IntentFilter();
+		filter.addAction(ACTION_UUID);
+		appContext.registerReceiver(receiver, filter);
+		try {
+			List<BluetoothDevice> pending = new ArrayList<>();
+			for (BluetoothDevice d : unknown) {
+				if (d.fetchUuidsWithSdp()) {
+					if (LOG.isLoggable(INFO)) {
+						LOG.info("Fetching UUIDs for "
+								+ scrubMacAddress(d.getAddress()));
+					}
+					pending.add(d);
+				} else {
+					if (LOG.isLoggable(INFO)) {
+						LOG.info("Failed to fetch UUIDs for "
+								+ scrubMacAddress(d.getAddress()));
+					}
+				}
+			}
+			long now = clock.currentTimeMillis();
+			long end = now + MAX_SERVICE_DISCOVERY_MS;
+			while (now < end && !pending.isEmpty()) {
+				Intent i = intents.poll(end - now, MILLISECONDS);
+				if (i == null) break;
+				BluetoothDevice d = requireNonNull(
+						i.getParcelableExtra(EXTRA_DEVICE));
+				if (LOG.isLoggable(INFO)) {
+					LOG.info("Fetched UUIDs for "
+							+ scrubMacAddress(d.getAddress()));
+				}
+				Set<String> uuids = getUuids(d);
+				Parcelable[] extra = i.getParcelableArrayExtra(EXTRA_UUID);
+				if (extra != null) {
+					for (Parcelable p : extra) {
+						uuids.addAll(getUuidStrings((ParcelUuid) p));
+					}
+				}
+				for (String uuid : uuids) {
+					Pair<TransportProperties, DiscoveryHandler> pair =
+							byUuid.remove(uuid);
+					if (pair != null) {
+						if (LOG.isLoggable(INFO)) {
+							LOG.info("Matched "
+									+ scrubMacAddress(d.getAddress())
+									+ " by fetched UUID");
+						}
+						TransportProperties p =
+								new TransportProperties(pair.getFirst());
+						p.put(PROP_ADDRESS, d.getAddress());
+						discovered.add(new Pair<>(p, pair.getSecond()));
+						break;
+					}
+				}
+				pending.remove(d);
+				now = clock.currentTimeMillis();
+			}
+			if (LOG.isLoggable(INFO)) {
+				if (pending.isEmpty()) {
+					LOG.info("Finished fetching UUIDs");
+				} else {
+					LOG.info("Failed to fetch UUIDs for " + pending.size()
+							+ " devices");
+				}
+			}
+		} catch (InterruptedException e) {
+			LOG.info("Interrupted while fetching UUIDs");
+			Thread.currentThread().interrupt();
+		} finally {
+			appContext.unregisterReceiver(receiver);
+		}
+
+		if (LOG.isLoggable(INFO)) {
+			LOG.info("Discovered " + discovered.size() + " contacts");
+		}
+		for (Pair<TransportProperties, DiscoveryHandler> pair : discovered) {
+			pair.getSecond().handleDevice(pair.getFirst());
+		}
+	}
+
+	private Set<String> getUuids(BluetoothDevice d) {
+		Set<String> strings = new TreeSet<>();
+		ParcelUuid[] uuids = d.getUuids();
+		if (uuids == null) return strings;
+		for (ParcelUuid u : uuids) strings.addAll(getUuidStrings(u));
+		return strings;
+	}
+
+	// Workaround for https://code.google.com/p/android/issues/detail?id=197341
+	private List<String> getUuidStrings(ParcelUuid u) {
+		UUID forwards = u.getUuid();
+		ByteBuffer buf = ByteBuffer.allocate(16);
+		buf.putLong(forwards.getLeastSignificantBits());
+		buf.putLong(forwards.getMostSignificantBits());
+		buf.rewind();
+		buf.order(LITTLE_ENDIAN);
+		UUID backwards = new UUID(buf.getLong(), buf.getLong());
+		return asList(forwards.toString(), backwards.toString());
+	}
+
+	private List<BluetoothDevice> discoverDevices() {
+		if (adapter.isDiscovering()) {
+			LOG.info("Already discovering");
+			return emptyList();
+		}
+		List<BluetoothDevice> devices = new ArrayList<>();
+		BlockingQueue<Intent> intents = new LinkedBlockingQueue<>();
+		QueueingReceiver receiver = new QueueingReceiver(intents);
 		IntentFilter filter = new IntentFilter();
 		filter.addAction(ACTION_DISCOVERY_STARTED);
 		filter.addAction(ACTION_DISCOVERY_FINISHED);
@@ -241,8 +452,9 @@ class AndroidBluetoothPlugin extends BluetoothPlugin<BluetoothServerSocket> {
 		appContext.registerReceiver(receiver, filter);
 		try {
 			if (adapter.startDiscovery()) {
-				long now = clock.currentTimeMillis();
+				long start = clock.currentTimeMillis();
-				long end = now + MAX_DISCOVERY_MS;
+				long end = start + MAX_DEVICE_DISCOVERY_MS;
+				long now = start;
 				while (now < end) {
 					Intent i = intents.poll(end - now, MILLISECONDS);
 					if (i == null) break;
@@ -251,17 +463,26 @@ class AndroidBluetoothPlugin extends BluetoothPlugin<BluetoothServerSocket> {
 						LOG.info("Discovery started");
 					} else if (ACTION_DISCOVERY_FINISHED.equals(action)) {
 						LOG.info("Discovery finished");
-						break;
+						now = clock.currentTimeMillis();
+						if (now - start < MIN_DEVICE_DISCOVERY_MS) {
+							LOG.info("Discovery finished quickly, retrying");
+							if (!adapter.startDiscovery()) {
+								LOG.info("Could not restart discovery");
+								break;
+							}
+						} else {
+							break;
+						}
 					} else if (ACTION_FOUND.equals(action)) {
-						BluetoothDevice d = i.getParcelableExtra(EXTRA_DEVICE);
+						BluetoothDevice d = requireNonNull(
+								i.getParcelableExtra(EXTRA_DEVICE));
 						// Ignore Bluetooth LE devices
 						if (SDK_INT < 18 || d.getType() != DEVICE_TYPE_LE) {
-							String address = d.getAddress();
+							if (LOG.isLoggable(INFO)) {
-							if (LOG.isLoggable(INFO))
+								LOG.info("Discovered "
-								LOG.info("Discovered " +
+										+ scrubMacAddress(d.getAddress()));
-										scrubMacAddress(address));
+							}
-							if (!addresses.contains(address))
+							if (!devices.contains(d)) devices.add(d);
-								addresses.add(address);
 						}
 					}
 					now = clock.currentTimeMillis();
@@ -277,9 +498,9 @@ class AndroidBluetoothPlugin extends BluetoothPlugin<BluetoothServerSocket> {
 			adapter.cancelDiscovery();
 			appContext.unregisterReceiver(receiver);
 		}
-		// Shuffle the addresses so we don't always try the same one first
+		// Shuffle the devices so we don't always try the same one first
-		shuffle(addresses);
+		shuffle(devices);
-		return addresses;
+		return devices;
 	}
 
 	private class BluetoothStateReceiver extends BroadcastReceiver {
@@ -300,11 +521,11 @@ class AndroidBluetoothPlugin extends BluetoothPlugin<BluetoothServerSocket> {
 		}
 	}
 
-	private static class DiscoveryReceiver extends BroadcastReceiver {
+	private static class QueueingReceiver extends BroadcastReceiver {
 
 		private final BlockingQueue<Intent> intents;
 
-		private DiscoveryReceiver(BlockingQueue<Intent> intents) {
+		private QueueingReceiver(BlockingQueue<Intent> intents) {
 			this.intents = intents;
 		}
 

bramble-android/src/main/java/org/briarproject/bramble/plugin/bluetooth/AndroidBluetoothPluginFactory.java

@@ -3,8 +3,9 @@ package org.briarproject.bramble.plugin.bluetooth;
 import android.content.Context;
 
 import org.briarproject.bramble.api.event.EventBus;
-import org.briarproject.bramble.api.io.TimeoutMonitor;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.Backoff;
+import org.briarproject.bramble.api.plugin.BackoffFactory;
 import org.briarproject.bramble.api.plugin.PluginCallback;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
@@ -14,44 +15,39 @@ import org.briarproject.bramble.api.system.Clock;
 
 import java.security.SecureRandom;
 import java.util.concurrent.Executor;
-import java.util.concurrent.ScheduledExecutorService;
 
 import javax.annotation.concurrent.Immutable;
 
-import static java.util.concurrent.TimeUnit.MINUTES;
-import static java.util.concurrent.TimeUnit.SECONDS;
 import static org.briarproject.bramble.api.plugin.BluetoothConstants.ID;
 
 @Immutable
 @NotNullByDefault
 public class AndroidBluetoothPluginFactory implements DuplexPluginFactory {
 
-	private static final int MAX_LATENCY = (int) SECONDS.toMillis(30);
+	private static final int MAX_LATENCY = 30 * 1000; // 30 seconds
-	private static final int MAX_IDLE_TIME = (int) SECONDS.toMillis(30);
+	private static final int MIN_POLLING_INTERVAL = 60 * 1000; // 1 minute
-	private static final int POLLING_INTERVAL = (int) MINUTES.toMillis(2);
+	private static final int MAX_POLLING_INTERVAL = 10 * 60 * 1000; // 10 mins
+	private static final double BACKOFF_BASE = 1.2;
 
 	private final Executor ioExecutor;
-	private final ScheduledExecutorService scheduler;
 	private final AndroidExecutor androidExecutor;
 	private final Context appContext;
 	private final SecureRandom secureRandom;
 	private final EventBus eventBus;
 	private final Clock clock;
-	private final TimeoutMonitor timeoutMonitor;
+	private final BackoffFactory backoffFactory;
 
 	public AndroidBluetoothPluginFactory(Executor ioExecutor,
-			ScheduledExecutorService scheduler,
 			AndroidExecutor androidExecutor, Context appContext,
 			SecureRandom secureRandom, EventBus eventBus, Clock clock,
-			TimeoutMonitor timeoutMonitor) {
+			BackoffFactory backoffFactory) {
 		this.ioExecutor = ioExecutor;
-		this.scheduler = scheduler;
 		this.androidExecutor = androidExecutor;
 		this.appContext = appContext;
 		this.secureRandom = secureRandom;
 		this.eventBus = eventBus;
 		this.clock = clock;
-		this.timeoutMonitor = timeoutMonitor;
+		this.backoffFactory = backoffFactory;
 	}
 
 	@Override
@@ -67,11 +63,12 @@ public class AndroidBluetoothPluginFactory implements DuplexPluginFactory {
 	@Override
 	public DuplexPlugin createPlugin(PluginCallback callback) {
 		BluetoothConnectionLimiter connectionLimiter =
-				new BluetoothConnectionLimiterImpl(eventBus);
+				new BluetoothConnectionLimiterImpl();
+		Backoff backoff = backoffFactory.createBackoff(MIN_POLLING_INTERVAL,
+				MAX_POLLING_INTERVAL, BACKOFF_BASE);
 		AndroidBluetoothPlugin plugin = new AndroidBluetoothPlugin(
-				connectionLimiter, timeoutMonitor, ioExecutor, secureRandom,
+				connectionLimiter, ioExecutor, androidExecutor, appContext,
-				scheduler, androidExecutor, appContext, clock, callback,
+				secureRandom, clock, backoff, callback, MAX_LATENCY);
-				MAX_LATENCY, MAX_IDLE_TIME, POLLING_INTERVAL);
 		eventBus.addListener(plugin);
 		return plugin;
 	}

bramble-android/src/main/java/org/briarproject/bramble/plugin/bluetooth/AndroidBluetoothTransportConnection.java

@@ -1,60 +1,33 @@
 package org.briarproject.bramble.plugin.bluetooth;
 
 import android.bluetooth.BluetoothSocket;
-import android.content.Context;
-import android.os.PowerManager;
 
-import org.briarproject.bramble.api.io.TimeoutMonitor;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.Plugin;
 import org.briarproject.bramble.api.plugin.duplex.AbstractDuplexTransportConnection;
-import org.briarproject.bramble.util.RenewableWakeLock;
 
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
-import java.util.concurrent.ScheduledExecutorService;
-
-import static android.content.Context.POWER_SERVICE;
-import static android.os.PowerManager.PARTIAL_WAKE_LOCK;
-import static java.util.concurrent.TimeUnit.MINUTES;
-import static org.briarproject.bramble.api.nullsafety.NullSafety.requireNonNull;
-import static org.briarproject.bramble.api.plugin.BluetoothConstants.PROP_ADDRESS;
-import static org.briarproject.bramble.util.AndroidUtils.getWakeLockTag;
-import static org.briarproject.bramble.util.AndroidUtils.isValidBluetoothAddress;
 
 @NotNullByDefault
 class AndroidBluetoothTransportConnection
 		extends AbstractDuplexTransportConnection {
 
-	private final BluetoothConnectionLimiter connectionLimiter;
+	private final BluetoothConnectionLimiter connectionManager;
-	private final RenewableWakeLock wakeLock;
 	private final BluetoothSocket socket;
-	private final InputStream in;
 
 	AndroidBluetoothTransportConnection(Plugin plugin,
-			BluetoothConnectionLimiter connectionLimiter,
+			BluetoothConnectionLimiter connectionManager,
-			TimeoutMonitor timeoutMonitor, Context appContext,
+			BluetoothSocket socket) {
-			ScheduledExecutorService scheduler, BluetoothSocket socket)
-			throws IOException {
 		super(plugin);
-		this.connectionLimiter = connectionLimiter;
+		this.connectionManager = connectionManager;
 		this.socket = socket;
-		in = timeoutMonitor.createTimeoutInputStream(
-				socket.getInputStream(), plugin.getMaxIdleTime() * 2);
-		PowerManager powerManager = (PowerManager)
-				requireNonNull(appContext.getSystemService(POWER_SERVICE));
-		String tag = getWakeLockTag(appContext);
-		wakeLock = new RenewableWakeLock(powerManager, scheduler,
-				PARTIAL_WAKE_LOCK, tag, 1, MINUTES);
-		wakeLock.acquire();
-		String address = socket.getRemoteDevice().getAddress();
-		if (isValidBluetoothAddress(address)) remote.put(PROP_ADDRESS, address);
 	}
 
 	@Override
-	protected InputStream getInputStream() {
+	protected InputStream getInputStream() throws IOException {
-		return in;
+		return socket.getInputStream();
 	}
 
 	@Override
@@ -67,8 +40,7 @@ class AndroidBluetoothTransportConnection
 		try {
 			socket.close();
 		} finally {
-			wakeLock.release();
+			connectionManager.connectionClosed(this);
-			connectionLimiter.connectionClosed(this);
 		}
 	}
 }

bramble-android/src/main/java/org/briarproject/bramble/plugin/tcp/AndroidLanTcpPlugin.java

@@ -1,29 +1,23 @@
 package org.briarproject.bramble.plugin.tcp;
 
-import android.annotation.TargetApi;
 import android.content.Context;
 import android.net.ConnectivityManager;
-import android.net.LinkAddress;
-import android.net.LinkProperties;
 import android.net.Network;
-import android.net.NetworkCapabilities;
+import android.net.NetworkInfo;
 import android.net.wifi.WifiInfo;
 import android.net.wifi.WifiManager;
 
 import org.briarproject.bramble.PoliteExecutor;
-import org.briarproject.bramble.api.Pair;
 import org.briarproject.bramble.api.event.Event;
 import org.briarproject.bramble.api.network.event.NetworkStatusEvent;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.Backoff;
 import org.briarproject.bramble.api.plugin.PluginCallback;
 import org.briarproject.bramble.api.settings.Settings;
 
 import java.io.IOException;
 import java.net.InetAddress;
-import java.net.InterfaceAddress;
-import java.net.NetworkInterface;
 import java.net.Socket;
-import java.net.SocketException;
 import java.net.UnknownHostException;
 import java.util.List;
 import java.util.concurrent.Executor;
@@ -34,18 +28,15 @@ import javax.net.SocketFactory;
 
 import static android.content.Context.CONNECTIVITY_SERVICE;
 import static android.content.Context.WIFI_SERVICE;
-import static android.net.NetworkCapabilities.TRANSPORT_WIFI;
+import static android.net.ConnectivityManager.TYPE_WIFI;
 import static android.os.Build.VERSION.SDK_INT;
 import static java.util.Collections.emptyList;
-import static java.util.Collections.list;
 import static java.util.Collections.singletonList;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
-import static org.briarproject.bramble.api.plugin.LanTcpConstants.DEFAULT_PREF_PLUGIN_ENABLE;
 import static org.briarproject.bramble.api.plugin.Plugin.State.ACTIVE;
 import static org.briarproject.bramble.api.plugin.Plugin.State.INACTIVE;
 import static org.briarproject.bramble.util.IoUtils.tryToClose;
-import static org.briarproject.bramble.util.LogUtils.logException;
 
 @NotNullByDefault
 class AndroidLanTcpPlugin extends LanTcpPlugin {
@@ -61,9 +52,9 @@ class AndroidLanTcpPlugin extends LanTcpPlugin {
 	private volatile SocketFactory socketFactory;
 
 	AndroidLanTcpPlugin(Executor ioExecutor, Context appContext,
-			PluginCallback callback, int maxLatency, int maxIdleTime,
+			Backoff backoff, PluginCallback callback, int maxLatency,
-			int pollingInterval, int connectionTimeout) {
+			int maxIdleTime, int connectionTimeout) {
-		super(ioExecutor, callback, maxLatency, maxIdleTime, pollingInterval,
+		super(ioExecutor, backoff, callback, maxLatency, maxIdleTime,
 				connectionTimeout);
 		// Don't execute more than one connection status check at a time
 		connectionStatusExecutor =
@@ -82,8 +73,7 @@ class AndroidLanTcpPlugin extends LanTcpPlugin {
 		if (used.getAndSet(true)) throw new IllegalStateException();
 		initialisePortProperty();
 		Settings settings = callback.getSettings();
-		state.setStarted(settings.getBoolean(PREF_PLUGIN_ENABLE,
+		state.setStarted(settings.getBoolean(PREF_PLUGIN_ENABLE, false));
-				DEFAULT_PREF_PLUGIN_ENABLE));
 		updateConnectionStatus();
 	}
 
@@ -93,125 +83,21 @@ class AndroidLanTcpPlugin extends LanTcpPlugin {
 	}
 
 	@Override
-	protected List<InetAddress> getUsableLocalInetAddresses(boolean ipv4) {
+	protected List<InetAddress> getUsableLocalInetAddresses() {
-		InetAddress addr = getWifiAddress(ipv4);
+		// If the device doesn't have wifi, don't open any sockets
-		return addr == null ? emptyList() : singletonList(addr);
+		if (wifiManager == null) return emptyList();
-	}
-
-	@Nullable
-	private InetAddress getWifiAddress(boolean ipv4) {
-		Pair<InetAddress, Boolean> wifi = getWifiIpv4Address();
-		if (ipv4) return wifi == null ? null : wifi.getFirst();
-		// If there's no wifi IPv4 address, we might be a client on an
-		// IPv6-only wifi network. We can only detect this on API 21+
-		if (wifi == null) {
-			return SDK_INT >= 21 ? getWifiClientIpv6Address() : null;
-		}
-		// Use the wifi IPv4 address to determine which interface's IPv6
-		// address we should return (if the interface has a suitable address)
-		return getIpv6AddressForInterface(wifi.getFirst());
-	}
-
-	/**
-	 * Returns a {@link Pair} where the first element is the IPv4 address of
-	 * the wifi interface and the second element is true if this device is
-	 * providing an access point, or false if this device is a client. Returns
-	 * null if this device isn't connected to wifi as an access point or client.
-	 */
-	@Nullable
-	private Pair<InetAddress, Boolean> getWifiIpv4Address() {
-		if (wifiManager == null) return null;
 		// If we're connected to a wifi network, return its address
 		WifiInfo info = wifiManager.getConnectionInfo();
 		if (info != null && info.getIpAddress() != 0) {
-			return new Pair<>(intToInetAddress(info.getIpAddress()), false);
+			return singletonList(intToInetAddress(info.getIpAddress()));
 		}
-		List<InterfaceAddress> ifAddrs = getLocalInterfaceAddresses();
+		// If we're running an access point, return its address
-		// If we're providing a normal access point, return its address
+		for (InetAddress addr : getLocalInetAddresses()) {
-		for (InterfaceAddress ifAddr : ifAddrs) {
+			if (addr.equals(WIFI_AP_ADDRESS)) return singletonList(addr);
-			if (isAndroidWifiApAddress(ifAddr)) {
+			if (addr.equals(WIFI_DIRECT_AP_ADDRESS)) return singletonList(addr);
-				return new Pair<>(ifAddr.getAddress(), true);
-			}
-		}
-		// If we're providing a wifi direct access point, return its address
-		for (InterfaceAddress ifAddr : ifAddrs) {
-			if (isAndroidWifiDirectApAddress(ifAddr)) {
-				return new Pair<>(ifAddr.getAddress(), true);
-			}
-		}
-		// Not connected to wifi
-		return null;
-	}
-
-	/**
-	 * Returns true if the given address belongs to a network provided by an
-	 * Android access point (including the access point's own address).
-	 * <p>
-	 * The access point's address is usually 192.168.43.1, but at least one
-	 * device (Honor 8A) may use other addresses in the range 192.168.43.0/24.
-	 */
-	private boolean isAndroidWifiApAddress(InterfaceAddress ifAddr) {
-		if (ifAddr.getNetworkPrefixLength() != 24) return false;
-		byte[] ip = ifAddr.getAddress().getAddress();
-		return ip.length == 4
-				&& ip[0] == (byte) 192
-				&& ip[1] == (byte) 168
-				&& ip[2] == (byte) 43;
-	}
-
-	/**
-	 * Returns true if the given address belongs to a network provided by an
-	 * Android wifi direct legacy mode access point (including the access
-	 * point's own address).
-	 */
-	private boolean isAndroidWifiDirectApAddress(InterfaceAddress ifAddr) {
-		if (ifAddr.getNetworkPrefixLength() != 24) return false;
-		byte[] ip = ifAddr.getAddress().getAddress();
-		return ip.length == 4
-				&& ip[0] == (byte) 192
-				&& ip[1] == (byte) 168
-				&& ip[2] == (byte) 49;
-	}
-
-	/**
-	 * Returns a link-local IPv6 address for the wifi client interface, or null
-	 * if there's no such interface or it doesn't have a suitable address.
-	 */
-	@TargetApi(21)
-	@Nullable
-	private InetAddress getWifiClientIpv6Address() {
-		for (Network net : connectivityManager.getAllNetworks()) {
-			NetworkCapabilities caps =
-					connectivityManager.getNetworkCapabilities(net);
-			if (caps == null || !caps.hasTransport(TRANSPORT_WIFI)) continue;
-			LinkProperties props = connectivityManager.getLinkProperties(net);
-			if (props == null) continue;
-			for (LinkAddress linkAddress : props.getLinkAddresses()) {
-				InetAddress addr = linkAddress.getAddress();
-				if (isIpv6LinkLocalAddress(addr)) return addr;
-			}
-		}
-		return null;
-	}
-
-	/**
-	 * Returns a link-local IPv6 address for the interface with the given IPv4
-	 * address, or null if the interface doesn't have a suitable address.
-	 */
-	@Nullable
-	private InetAddress getIpv6AddressForInterface(InetAddress ipv4) {
-		try {
-			NetworkInterface iface = NetworkInterface.getByInetAddress(ipv4);
-			if (iface == null) return null;
-			for (InetAddress addr : list(iface.getInetAddresses())) {
-				if (isIpv6LinkLocalAddress(addr)) return addr;
-			}
-			// No suitable address
-			return null;
-		} catch (SocketException e) {
-			logException(LOG, WARNING, e);
-			return null;
 		}
+		// No suitable addresses
+		return emptyList();
 	}
 
 	private InetAddress intToInetAddress(int ip) {
@@ -233,11 +119,9 @@ class AndroidLanTcpPlugin extends LanTcpPlugin {
 	private SocketFactory getSocketFactory() {
 		if (SDK_INT < 21) return SocketFactory.getDefault();
 		for (Network net : connectivityManager.getAllNetworks()) {
-			NetworkCapabilities caps =
+			NetworkInfo info = connectivityManager.getNetworkInfo(net);
-					connectivityManager.getNetworkCapabilities(net);
+			if (info != null && info.getType() == TYPE_WIFI)
-			if (caps != null && caps.hasTransport(TRANSPORT_WIFI)) {
 				return net.getSocketFactory();
-			}
 		}
 		LOG.warning("Could not find suitable socket factory");
 		return SocketFactory.getDefault();
@@ -253,20 +137,9 @@ class AndroidLanTcpPlugin extends LanTcpPlugin {
 		connectionStatusExecutor.execute(() -> {
 			State s = getState();
 			if (s != ACTIVE && s != INACTIVE) return;
-			Pair<InetAddress, Boolean> wifi = getPreferredWifiAddress();
+			List<InetAddress> addrs = getLocalInetAddresses();
-			if (wifi == null) {
+			if (addrs.contains(WIFI_AP_ADDRESS)
-				LOG.info("Not connected to wifi");
+					|| addrs.contains(WIFI_DIRECT_AP_ADDRESS)) {
-				socketFactory = SocketFactory.getDefault();
-				// Server sockets may not have been closed automatically when
-				// interface was taken down. If any sockets are open, closing
-				// them here will cause the sockets to be cleared and the state
-				// to be updated in acceptContactConnections()
-				if (s == ACTIVE) {
-					LOG.info("Closing server sockets");
-					tryToClose(state.getServerSocket(true), LOG, WARNING);
-					tryToClose(state.getServerSocket(false), LOG, WARNING);
-				}
-			} else if (wifi.getSecond()) {
 				LOG.info("Providing wifi hotspot");
 				// There's no corresponding Network object and thus no way
 				// to get a suitable socket factory, so we won't be able to
@@ -274,6 +147,16 @@ class AndroidLanTcpPlugin extends LanTcpPlugin {
 				// has internet access
 				socketFactory = SocketFactory.getDefault();
 				if (s == INACTIVE) bind();
+			} else if (addrs.isEmpty()) {
+				LOG.info("Not connected to wifi");
+				socketFactory = SocketFactory.getDefault();
+				// Server socket may not have been closed automatically when
+				// interface was taken down. Socket will be cleared and state
+				// updated in acceptContactConnections()
+				if (s == ACTIVE) {
+					LOG.info("Closing server socket");
+					tryToClose(state.getServerSocket(), LOG, WARNING);
+				}
 			} else {
 				LOG.info("Connected to wifi");
 				socketFactory = getSocketFactory();
@@ -281,23 +164,4 @@ class AndroidLanTcpPlugin extends LanTcpPlugin {
 			}
 		});
 	}
-
-	/**
-	 * Returns a {@link Pair} where the first element is an IP address (IPv4 if
-	 * available, otherwise IPv6) of the wifi interface and the second element
-	 * is true if this device is providing an access point, or false if this
-	 * device is a client. Returns null if this device isn't connected to wifi
-	 * as an access point or client.
-	 */
-	@Nullable
-	private Pair<InetAddress, Boolean> getPreferredWifiAddress() {
-		Pair<InetAddress, Boolean> wifi = getWifiIpv4Address();
-		// If there's no wifi IPv4 address, we might be a client on an
-		// IPv6-only wifi network. We can only detect this on API 21+
-		if (wifi == null && SDK_INT >= 21) {
-			InetAddress ipv6 = getWifiClientIpv6Address();
-			if (ipv6 != null) return new Pair<>(ipv6, false);
-		}
-		return wifi;
-	}
 }

bramble-android/src/main/java/org/briarproject/bramble/plugin/tcp/AndroidLanTcpPluginFactory.java

@@ -4,6 +4,8 @@ import android.content.Context;
 
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.Backoff;
+import org.briarproject.bramble.api.plugin.BackoffFactory;
 import org.briarproject.bramble.api.plugin.PluginCallback;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
@@ -13,27 +15,29 @@ import java.util.concurrent.Executor;
 
 import javax.annotation.concurrent.Immutable;
 
-import static java.util.concurrent.TimeUnit.MINUTES;
-import static java.util.concurrent.TimeUnit.SECONDS;
 import static org.briarproject.bramble.api.plugin.LanTcpConstants.ID;
 
 @Immutable
 @NotNullByDefault
 public class AndroidLanTcpPluginFactory implements DuplexPluginFactory {
 
-	private static final int MAX_LATENCY = (int) SECONDS.toMillis(30);
+	private static final int MAX_LATENCY = 30_000; // 30 seconds
-	private static final int MAX_IDLE_TIME = (int) SECONDS.toMillis(30);
+	private static final int MAX_IDLE_TIME = 30_000; // 30 seconds
-	private static final int POLLING_INTERVAL = (int) MINUTES.toMillis(1);
+	private static final int CONNECTION_TIMEOUT = 3_000; // 3 seconds
-	private static final int CONNECTION_TIMEOUT = (int) SECONDS.toMillis(3);
+	private static final int MIN_POLLING_INTERVAL = 60_000; // 1 minute
+	private static final int MAX_POLLING_INTERVAL = 600_000; // 10 mins
+	private static final double BACKOFF_BASE = 1.2;
 
 	private final Executor ioExecutor;
 	private final EventBus eventBus;
+	private final BackoffFactory backoffFactory;
 	private final Context appContext;
 
 	public AndroidLanTcpPluginFactory(Executor ioExecutor, EventBus eventBus,
-			Context appContext) {
+			BackoffFactory backoffFactory, Context appContext) {
 		this.ioExecutor = ioExecutor;
 		this.eventBus = eventBus;
+		this.backoffFactory = backoffFactory;
 		this.appContext = appContext;
 	}
 
@@ -49,9 +53,11 @@ public class AndroidLanTcpPluginFactory implements DuplexPluginFactory {
 
 	@Override
 	public DuplexPlugin createPlugin(PluginCallback callback) {
+		Backoff backoff = backoffFactory.createBackoff(MIN_POLLING_INTERVAL,
+				MAX_POLLING_INTERVAL, BACKOFF_BASE);
 		AndroidLanTcpPlugin plugin = new AndroidLanTcpPlugin(ioExecutor,
-				appContext, callback, MAX_LATENCY, MAX_IDLE_TIME,
+				appContext, backoff, callback, MAX_LATENCY, MAX_IDLE_TIME,
-				POLLING_INTERVAL, CONNECTION_TIMEOUT);
+				CONNECTION_TIMEOUT);
 		eventBus.addListener(plugin);
 		return plugin;
 	}

bramble-android/src/main/java/org/briarproject/bramble/plugin/tor/AndroidTorPlugin.java

@@ -10,6 +10,7 @@ import org.briarproject.bramble.api.battery.BatteryManager;
 import org.briarproject.bramble.api.network.NetworkManager;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
+import org.briarproject.bramble.api.plugin.Backoff;
 import org.briarproject.bramble.api.plugin.PluginCallback;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.api.system.LocationUtils;
@@ -26,7 +27,6 @@ import static android.content.Context.MODE_PRIVATE;
 import static android.content.Context.POWER_SERVICE;
 import static android.os.PowerManager.PARTIAL_WAKE_LOCK;
 import static java.util.concurrent.TimeUnit.MINUTES;
-import static org.briarproject.bramble.util.AndroidUtils.getWakeLockTag;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
@@ -40,22 +40,20 @@ class AndroidTorPlugin extends TorPlugin {
 			LocationUtils locationUtils, SocketFactory torSocketFactory,
 			Clock clock, ResourceProvider resourceProvider,
 			CircumventionProvider circumventionProvider,
-			BatteryManager batteryManager,
+			BatteryManager batteryManager, Backoff backoff,
 			TorRendezvousCrypto torRendezvousCrypto,
 			PluginCallback callback, String architecture, int maxLatency,
-			int maxIdleTime, int initialPollingInterval,
+			int maxIdleTime) {
-			int stablePollingInterval) {
 		super(ioExecutor, networkManager, locationUtils, torSocketFactory,
 				clock, resourceProvider, circumventionProvider, batteryManager,
-				torRendezvousCrypto, callback, architecture, maxLatency,
+				backoff, torRendezvousCrypto, callback, architecture, maxLatency, maxIdleTime,
-				maxIdleTime, initialPollingInterval, stablePollingInterval,
 				appContext.getDir("tor", MODE_PRIVATE));
 		this.appContext = appContext;
 		PowerManager pm = (PowerManager)
 				appContext.getSystemService(POWER_SERVICE);
 		if (pm == null) throw new AssertionError();
 		wakeLock = new RenewableWakeLock(pm, scheduler, PARTIAL_WAKE_LOCK,
-				getWakeLockTag(appContext), 1, MINUTES);
+				getWakeLockTag(), 1, MINUTES);
 	}
 
 	@Override
@@ -86,4 +84,17 @@ class AndroidTorPlugin extends TorPlugin {
 		super.stop();
 		wakeLock.release();
 	}
+
+	private String getWakeLockTag() {
+		PackageManager pm = appContext.getPackageManager();
+		for (PackageInfo info : pm.getInstalledPackages(0)) {
+			String name = info.packageName.toLowerCase();
+			if (name.startsWith("com.huawei.powergenie")) {
+				return "LocationManagerService";
+			} else if (name.startsWith("com.evenwell.powermonitor")) {
+				return "AudioIn";
+			}
+		}
+		return getClass().getSimpleName();
+	}
 }

bramble-android/src/main/java/org/briarproject/bramble/plugin/tor/AndroidTorPluginFactory.java

@@ -6,6 +6,8 @@ import org.briarproject.bramble.api.battery.BatteryManager;
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.network.NetworkManager;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.Backoff;
+import org.briarproject.bramble.api.plugin.BackoffFactory;
 import org.briarproject.bramble.api.plugin.PluginCallback;
 import org.briarproject.bramble.api.plugin.TorConstants;
 import org.briarproject.bramble.api.plugin.TransportId;
@@ -23,33 +25,18 @@ import java.util.logging.Logger;
 import javax.annotation.concurrent.Immutable;
 import javax.net.SocketFactory;
 
-import static java.util.concurrent.TimeUnit.MINUTES;
-import static java.util.concurrent.TimeUnit.SECONDS;
-import static java.util.logging.Logger.getLogger;
-
 @Immutable
 @NotNullByDefault
 public class AndroidTorPluginFactory implements DuplexPluginFactory {
 
 	private static final Logger LOG =
-			getLogger(AndroidTorPluginFactory.class.getName());
+			Logger.getLogger(AndroidTorPluginFactory.class.getName());
 
-	private static final int MAX_LATENCY = (int) SECONDS.toMillis(30);
+	private static final int MAX_LATENCY = 30 * 1000; // 30 seconds
-	private static final int MAX_IDLE_TIME = (int) SECONDS.toMillis(30);
+	private static final int MAX_IDLE_TIME = 30 * 1000; // 30 seconds
-
+	private static final int MIN_POLLING_INTERVAL = 60 * 1000; // 1 minute
-	/**
+	private static final int MAX_POLLING_INTERVAL = 10 * 60 * 1000; // 10 mins
-	 * How often to poll before our hidden service becomes reachable.
+	private static final double BACKOFF_BASE = 1.2;
-	 */
-	private static final int INITIAL_POLLING_INTERVAL =
-			(int) MINUTES.toMillis(1);
-
-	/**
-	 * How often to poll when our hidden service is reachable. Our contacts
-	 * will poll when they come online, so our polling is just a fallback in
-	 * case of repeated connection failures.
-	 */
-	private static final int STABLE_POLLING_INTERVAL =
-			(int) MINUTES.toMillis(15);
 
 	private final Executor ioExecutor;
 	private final ScheduledExecutorService scheduler;
@@ -58,6 +45,7 @@ public class AndroidTorPluginFactory implements DuplexPluginFactory {
 	private final LocationUtils locationUtils;
 	private final EventBus eventBus;
 	private final SocketFactory torSocketFactory;
+	private final BackoffFactory backoffFactory;
 	private final ResourceProvider resourceProvider;
 	private final CircumventionProvider circumventionProvider;
 	private final BatteryManager batteryManager;
@@ -67,7 +55,7 @@ public class AndroidTorPluginFactory implements DuplexPluginFactory {
 			ScheduledExecutorService scheduler, Context appContext,
 			NetworkManager networkManager, LocationUtils locationUtils,
 			EventBus eventBus, SocketFactory torSocketFactory,
-			ResourceProvider resourceProvider,
+			BackoffFactory backoffFactory, ResourceProvider resourceProvider,
 			CircumventionProvider circumventionProvider,
 			BatteryManager batteryManager, Clock clock) {
 		this.ioExecutor = ioExecutor;
@@ -77,6 +65,7 @@ public class AndroidTorPluginFactory implements DuplexPluginFactory {
 		this.locationUtils = locationUtils;
 		this.eventBus = eventBus;
 		this.torSocketFactory = torSocketFactory;
+		this.backoffFactory = backoffFactory;
 		this.resourceProvider = resourceProvider;
 		this.circumventionProvider = circumventionProvider;
 		this.batteryManager = batteryManager;
@@ -120,13 +109,14 @@ public class AndroidTorPluginFactory implements DuplexPluginFactory {
 		// Use position-independent executable
 		architecture += "_pie";
 
+		Backoff backoff = backoffFactory.createBackoff(MIN_POLLING_INTERVAL,
+				MAX_POLLING_INTERVAL, BACKOFF_BASE);
 		TorRendezvousCrypto torRendezvousCrypto = new TorRendezvousCryptoImpl();
 		AndroidTorPlugin plugin = new AndroidTorPlugin(ioExecutor, scheduler,
 				appContext, networkManager, locationUtils, torSocketFactory,
 				clock, resourceProvider, circumventionProvider, batteryManager,
-				torRendezvousCrypto, callback, architecture, MAX_LATENCY,
+				backoff, torRendezvousCrypto, callback, architecture,
-				MAX_IDLE_TIME, INITIAL_POLLING_INTERVAL,
+				MAX_LATENCY, MAX_IDLE_TIME);
-				STABLE_POLLING_INTERVAL);
 		eventBus.addListener(plugin);
 		return plugin;
 	}

bramble-android/src/main/java/org/briarproject/bramble/util/AndroidUtils.java

@@ -3,8 +3,6 @@ package org.briarproject.bramble.util;
 import android.annotation.SuppressLint;
 import android.bluetooth.BluetoothAdapter;
 import android.content.Context;
-import android.content.pm.PackageInfo;
-import android.content.pm.PackageManager;
 import android.os.Build;
 import android.provider.Settings;
 
@@ -73,7 +71,7 @@ public class AndroidUtils {
 		return new Pair<>("", "");
 	}
 
-	public static boolean isValidBluetoothAddress(@Nullable String address) {
+	private static boolean isValidBluetoothAddress(@Nullable String address) {
 		return !StringUtils.isNullOrEmpty(address)
 				&& BluetoothAdapter.checkBluetoothAddress(address)
 				&& !address.equals(FAKE_BLUETOOTH_ADDRESS);
@@ -119,17 +117,4 @@ public class AndroidUtils {
 		if (SDK_INT < 24) return new String[] {"image/jpeg", "image/png"};
 		else return new String[] {"image/jpeg", "image/png", "image/gif"};
 	}
-
-	public static String getWakeLockTag(Context ctx) {
-		PackageManager pm = ctx.getPackageManager();
-		for (PackageInfo info : pm.getInstalledPackages(0)) {
-			String name = info.packageName.toLowerCase();
-			if (name.startsWith("com.huawei.powergenie")) {
-				return "LocationManagerService";
-			} else if (name.startsWith("com.evenwell.powermonitor")) {
-				return "AudioIn";
-			}
-		}
-		return ctx.getPackageName();
-	}
 }

bramble-android/witness.gradle

@@ -70,7 +70,7 @@ dependencyVerification {
         'org.bouncycastle:bcpkix-jdk15on:1.56:bcpkix-jdk15on-1.56.jar:7043dee4e9e7175e93e0b36f45b1ec1ecb893c5f755667e8b916eb8dd201c6ca',
         'org.bouncycastle:bcprov-jdk15on:1.56:bcprov-jdk15on-1.56.jar:963e1ee14f808ffb99897d848ddcdb28fa91ddda867eb18d303e82728f878349',
         'org.briarproject:obfs4proxy-android:0.0.11-2:obfs4proxy-android-0.0.11-2.zip:57e55cbe87aa2aac210fdbb6cd8cdeafe15f825406a08ebf77a8b787aa2c6a8a',
-        'org.briarproject:tor-android:0.3.5.10:tor-android-0.3.5.10.zip:edd83bf557fcff2105eaa0bdb3f607a6852ebe7360920929ae3039dd5f4774c5',
+        'org.briarproject:tor-android:0.3.5.9:tor-android-0.3.5.9.zip:853b0440feccd6904bd03e6b2de53a62ebcde1d58068beeadc447a7dff950bc8',
         'org.checkerframework:checker-compat-qual:2.5.3:checker-compat-qual-2.5.3.jar:d76b9afea61c7c082908023f0cbc1427fab9abd2df915c8b8a3e7a509bccbc6d',
         'org.checkerframework:checker-qual:2.5.2:checker-qual-2.5.2.jar:64b02691c8b9d4e7700f8ee2e742dce7ea2c6e81e662b7522c9ee3bf568c040a',
         'org.codehaus.groovy:groovy-all:2.4.15:groovy-all-2.4.15.jar:51d6c4e71782e85674239189499854359d380fb75e1a703756e3aaa5b98a5af0',

bramble-api/src/main/java/org/briarproject/bramble/api/account/AccountManager.java

@@ -1,6 +1,5 @@
 package org.briarproject.bramble.api.account;
 
-import org.briarproject.bramble.api.crypto.DecryptionException;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.identity.IdentityManager;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
@@ -14,8 +13,7 @@ public interface AccountManager {
 	 * Returns true if the manager has the database key. This will be false
 	 * before {@link #createAccount(String, String)} or {@link #signIn(String)}
 	 * has been called, and true after {@link #createAccount(String, String)}
-	 * or {@link #signIn(String)} has returned true, until
+	 * or {@link #signIn(String)} has returned true, until the process exits.
-	 * {@link #deleteAccount()} is called or the process exits.
 	 */
 	boolean hasDatabaseKey();
 
@@ -24,22 +22,25 @@ public interface AccountManager {
 	 * before {@link #createAccount(String, String)} or {@link #signIn(String)}
 	 * has been called, and non-null after
 	 * {@link #createAccount(String, String)} or {@link #signIn(String)} has
-	 * returned true, until {@link #deleteAccount()} is called or the process
+	 * returned true, until the process exits.
-	 * exits.
 	 */
 	@Nullable
 	SecretKey getDatabaseKey();
 
 	/**
-	 * Returns true if the encrypted database key can be loaded from disk.
+	 * Returns true if the encrypted database key can be loaded from disk, and
+	 * the database directory exists and is a directory.
 	 */
 	boolean accountExists();
 
 	/**
 	 * Creates an identity with the given name and registers it with the
 	 * {@link IdentityManager}. Creates a database key, encrypts it with the
-	 * given password and stores it on disk. {@link #accountExists()} will
+	 * given password and stores it on disk.
-	 * return true after this method returns true.
+	 * <p/>
+	 * This method does not create the database directory, so
+	 * {@link #accountExists()} will continue to return false until the
+	 * database directory is created.
 	 */
 	boolean createAccount(String name, String password);
 
@@ -53,19 +54,17 @@ public interface AccountManager {
 	 * Loads the encrypted database key from disk and decrypts it with the
 	 * given password.
 	 *
-	 * @throws DecryptionException If the database key could not be loaded and
+	 * @return true if the database key was successfully loaded and decrypted.
-	 * decrypted.
 	 */
-	void signIn(String password) throws DecryptionException;
+	boolean signIn(String password);
 
 	/**
 	 * Loads the encrypted database key from disk, decrypts it with the old
 	 * password, encrypts it with the new password, and stores it on disk,
 	 * replacing the old key.
 	 *
-	 * @throws DecryptionException If the database key could not be loaded and
+	 * @return true if the database key was successfully loaded, re-encrypted
-	 * decrypted.
+	 * and stored.
 	 */
-	void changePassword(String oldPassword, String newPassword)
+	boolean changePassword(String oldPassword, String newPassword);
-			throws DecryptionException;
 }

bramble-api/src/main/java/org/briarproject/bramble/api/connection/ConnectionRegistry.java

@@ -1,130 +0,0 @@
-package org.briarproject.bramble.api.connection;
-
-import org.briarproject.bramble.api.contact.ContactId;
-import org.briarproject.bramble.api.contact.PendingContactId;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.plugin.PluginConfig;
-import org.briarproject.bramble.api.plugin.TransportId;
-import org.briarproject.bramble.api.plugin.event.ConnectionClosedEvent;
-import org.briarproject.bramble.api.plugin.event.ConnectionOpenedEvent;
-import org.briarproject.bramble.api.plugin.event.ContactConnectedEvent;
-import org.briarproject.bramble.api.plugin.event.ContactDisconnectedEvent;
-import org.briarproject.bramble.api.rendezvous.event.RendezvousConnectionClosedEvent;
-import org.briarproject.bramble.api.rendezvous.event.RendezvousConnectionOpenedEvent;
-import org.briarproject.bramble.api.sync.Priority;
-
-import java.util.Collection;
-
-/**
- * Keeps track of which contacts are currently connected by which transports.
- */
-@NotNullByDefault
-public interface ConnectionRegistry {
-
-	/**
-	 * Registers an incoming connection from the given contact over the given
-	 * transport. The connection's {@link Priority priority} can be set later
-	 * via {@link #setPriority(ContactId, TransportId, InterruptibleConnection,
-	 * Priority)} if a priority record is received from the contact.
-	 * <p>
-	 * Broadcasts {@link ConnectionOpenedEvent}. Also broadcasts
-	 * {@link ContactConnectedEvent} if this is the only connection with the
-	 * contact.
-	 */
-	void registerIncomingConnection(ContactId c, TransportId t,
-			InterruptibleConnection conn);
-
-	/**
-	 * Registers an outgoing connection to the given contact over the given
-	 * transport.
-	 * <p>
-	 * Broadcasts {@link ConnectionOpenedEvent}. Also broadcasts
-	 * {@link ContactConnectedEvent} if this is the only connection with the
-	 * contact.
-	 * <p>
-	 * If the registry has any "better" connections with the given contact, the
-	 * given connection will be interrupted. If the registry has any "worse"
-	 * connections with the given contact, those connections will be
-	 * interrupted.
-	 * <p>
-	 * Connection A is considered "better" than connection B if both
-	 * connections have had their priorities set, and either A's transport is
-	 * {@link PluginConfig#getTransportPreferences() preferred} to B's, or
-	 * they use the same transport and A has higher {@link Priority priority}
-	 * than B.
-	 * <p>
-	 * For backward compatibility, connections without priorities are not
-	 * considered better or worse than other connections.
-	 */
-	void registerOutgoingConnection(ContactId c, TransportId t,
-			InterruptibleConnection conn, Priority priority);
-
-	/**
-	 * Unregisters a connection with the given contact over the given transport.
-	 * <p>
-	 * Broadcasts {@link ConnectionClosedEvent}. Also broadcasts
-	 * {@link ContactDisconnectedEvent} if this is the only connection with
-	 * the contact.
-	 */
-	void unregisterConnection(ContactId c, TransportId t,
-			InterruptibleConnection conn, boolean incoming, boolean exception);
-
-	/**
-	 * Sets the {@link Priority priority} of a connection that was previously
-	 * registered via {@link #registerIncomingConnection(ContactId, TransportId,
-	 * InterruptibleConnection)}.
-	 * <p>
-	 * If the registry has any "better" connections with the given contact, the
-	 * given connection will be interrupted. If the registry has any "worse"
-	 * connections with the given contact, those connections will be
-	 * interrupted.
-	 * <p>
-	 * Connection A is considered "better" than connection B if both
-	 * connections have had their priorities set, and either A's transport is
-	 * {@link PluginConfig#getTransportPreferences() preferred} to B's, or
-	 * they use the same transport and A has higher {@link Priority priority}
-	 * than B.
-	 * <p>
-	 * For backward compatibility, connections without priorities are not
-	 * considered better or worse than other connections.
-	 */
-	void setPriority(ContactId c, TransportId t, InterruptibleConnection conn,
-			Priority priority);
-
-	/**
-	 * Returns any contacts that are connected via the given transport.
-	 */
-	Collection<ContactId> getConnectedContacts(TransportId t);
-
-	/**
-	 * Returns any contacts that are connected via the given transport or any
-	 * {@link PluginConfig#getTransportPreferences() better} transport.
-	 */
-	Collection<ContactId> getConnectedOrBetterContacts(TransportId t);
-
-	/**
-	 * Returns true if the given contact is connected via the given transport.
-	 */
-	boolean isConnected(ContactId c, TransportId t);
-
-	/**
-	 * Returns true if the given contact is connected via any transport.
-	 */
-	boolean isConnected(ContactId c);
-
-	/**
-	 * Registers a connection with the given pending contact. Broadcasts
-	 * {@link RendezvousConnectionOpenedEvent} if this is the only connection
-	 * with the pending contact.
-	 *
-	 * @return True if this is the only connection with the pending contact,
-	 * false if it is redundant and should be closed
-	 */
-	boolean registerConnection(PendingContactId p);
-
-	/**
-	 * Unregisters a connection with the given pending contact. Broadcasts
-	 * {@link RendezvousConnectionClosedEvent}.
-	 */
-	void unregisterConnection(PendingContactId p, boolean success);
-}

bramble-api/src/main/java/org/briarproject/bramble/api/connection/InterruptibleConnection.java

@@ -1,19 +0,0 @@
-package org.briarproject.bramble.api.connection;
-
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-
-/**
- * A duplex sync connection that can be closed by interrupting its outgoing
- * sync session.
- */
-@NotNullByDefault
-public interface InterruptibleConnection {
-
-	/**
-	 * Interrupts the connection's outgoing sync session. If the underlying
-	 * transport connection is alive and the remote peer is cooperative, this
-	 * should result in both sync sessions ending and the connection being
-	 * cleanly closed.
-	 */
-	void interruptOutgoingSession();
-}

bramble-api/src/main/java/org/briarproject/bramble/api/crypto/CryptoComponent.java

@@ -142,17 +142,16 @@ public interface CryptoComponent {
 	/**
 	 * Decrypts and authenticates the given ciphertext that has been read from
 	 * storage. The encryption and authentication keys are derived from the
-	 * given password.
+	 * given password. Returns null if the ciphertext cannot be decrypted and
+	 * authenticated (for example, if the password is wrong).
 	 *
 	 * @param keyStrengthener Used to strengthen the password-based key. If
 	 * null, or if strengthening was not used when encrypting the ciphertext,
 	 * the password-based key will not be strengthened
-	 * @throws DecryptionException If the ciphertext cannot be decrypted and
-	 * authenticated (for example, if the password is wrong).
 	 */
+	@Nullable
 	byte[] decryptWithPassword(byte[] ciphertext, String password,
-			@Nullable KeyStrengthener keyStrengthener)
+			@Nullable KeyStrengthener keyStrengthener);
-			throws DecryptionException;
 
 	/**
 	 * Returns true if the given ciphertext was encrypted using a strengthened

bramble-api/src/main/java/org/briarproject/bramble/api/crypto/DecryptionException.java

@@ -1,17 +0,0 @@
-package org.briarproject.bramble.api.crypto;
-
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-
-@NotNullByDefault
-public class DecryptionException extends Exception {
-
-	private final DecryptionResult result;
-
-	public DecryptionException(DecryptionResult result) {
-		this.result = result;
-	}
-
-	public DecryptionResult getDecryptionResult() {
-		return result;
-	}
-}

bramble-api/src/main/java/org/briarproject/bramble/api/crypto/DecryptionResult.java

@@ -1,29 +0,0 @@
-package org.briarproject.bramble.api.crypto;
-
-/**
- * The result of a password-based decryption operation.
- */
-public enum DecryptionResult {
-
-	/**
-	 * Decryption succeeded.
-	 */
-	SUCCESS,
-
-	/**
-	 * Decryption failed because the format of the ciphertext was invalid.
-	 */
-	INVALID_CIPHERTEXT,
-
-	/**
-	 * Decryption failed because the {@link KeyStrengthener} used for
-	 * encryption was not available for decryption.
-	 */
-	KEY_STRENGTHENER_ERROR,
-
-	/**
-	 * Decryption failed because the password used for decryption did not match
-	 * the password used for encryption.
-	 */
-	INVALID_PASSWORD
-}

bramble-api/src/main/java/org/briarproject/bramble/api/io/TimeoutMonitor.java

@@ -1,15 +0,0 @@
-package org.briarproject.bramble.api.io;
-
-import java.io.InputStream;
-
-public interface TimeoutMonitor {
-
-	/**
-	 * Returns an {@link InputStream} that wraps the given stream and allows
-	 * read timeouts to be detected.
-	 *
-	 * @param timeoutMs The read timeout in milliseconds. Timeouts will be
-	 * detected eventually but are not guaranteed to be detected immediately.
-	 */
-	InputStream createTimeoutInputStream(InputStream in, long timeoutMs);
-}

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/Backoff.java

@@ -0,0 +1,22 @@
+package org.briarproject.bramble.api.plugin;
+
+/**
+ * Calculates polling intervals for transport plugins that use backoff.
+ */
+public interface Backoff {
+
+	/**
+	 * Returns the current polling interval.
+	 */
+	int getPollingInterval();
+
+	/**
+	 * Increments the backoff counter.
+	 */
+	void increment();
+
+	/**
+	 * Resets the backoff counter.
+	 */
+	void reset();
+}

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/BackoffFactory.java

@@ -0,0 +1,7 @@
+package org.briarproject.bramble.api.plugin;
+
+public interface BackoffFactory {
+
+	Backoff createBackoff(int minInterval, int maxInterval,
+			double base);
+}

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/BluetoothConstants.java

@@ -6,10 +6,6 @@ public interface BluetoothConstants {
 
 	int UUID_BYTES = 16;
 
-	// Transport properties
 	String PROP_ADDRESS = "address";
 	String PROP_UUID = "uuid";
-
-	// Default value for PREF_PLUGIN_ENABLE
-	boolean DEFAULT_PREF_PLUGIN_ENABLE = false;
 }

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/ConnectionManager.java

@@ -1,11 +1,8 @@
-package org.briarproject.bramble.api.connection;
+package org.briarproject.bramble.api.plugin;
 
 import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.contact.PendingContactId;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.plugin.TransportConnectionReader;
-import org.briarproject.bramble.api.plugin.TransportConnectionWriter;
-import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
 
 @NotNullByDefault

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/ConnectionRegistry.java

@@ -0,0 +1,67 @@
+package org.briarproject.bramble.api.plugin;
+
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.contact.PendingContactId;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.event.ConnectionClosedEvent;
+import org.briarproject.bramble.api.plugin.event.ConnectionOpenedEvent;
+import org.briarproject.bramble.api.plugin.event.ContactConnectedEvent;
+import org.briarproject.bramble.api.plugin.event.ContactDisconnectedEvent;
+import org.briarproject.bramble.api.rendezvous.event.RendezvousConnectionClosedEvent;
+import org.briarproject.bramble.api.rendezvous.event.RendezvousConnectionOpenedEvent;
+
+import java.util.Collection;
+
+/**
+ * Keeps track of which contacts are currently connected by which transports.
+ */
+@NotNullByDefault
+public interface ConnectionRegistry {
+
+	/**
+	 * Registers a connection with the given contact over the given transport.
+	 * Broadcasts {@link ConnectionOpenedEvent}. Also broadcasts
+	 * {@link ContactConnectedEvent} if this is the only connection with the
+	 * contact.
+	 */
+	void registerConnection(ContactId c, TransportId t, boolean incoming);
+
+	/**
+	 * Unregisters a connection with the given contact over the given transport.
+	 * Broadcasts {@link ConnectionClosedEvent}. Also broadcasts
+	 * {@link ContactDisconnectedEvent} if this is the only connection with
+	 * the contact.
+	 */
+	void unregisterConnection(ContactId c, TransportId t, boolean incoming);
+
+	/**
+	 * Returns any contacts that are connected via the given transport.
+	 */
+	Collection<ContactId> getConnectedContacts(TransportId t);
+
+	/**
+	 * Returns true if the given contact is connected via the given transport.
+	 */
+	boolean isConnected(ContactId c, TransportId t);
+
+	/**
+	 * Returns true if the given contact is connected via any transport.
+	 */
+	boolean isConnected(ContactId c);
+
+	/**
+	 * Registers a connection with the given pending contact. Broadcasts
+	 * {@link RendezvousConnectionOpenedEvent} if this is the only connection
+	 * with the pending contact.
+	 *
+	 * @return True if this is the only connection with the pending contact,
+	 * false if it is redundant and should be closed
+	 */
+	boolean registerConnection(PendingContactId p);
+
+	/**
+	 * Unregisters a connection with the given pending contact. Broadcasts
+	 * {@link RendezvousConnectionClosedEvent}.
+	 */
+	void unregisterConnection(PendingContactId p, boolean success);
+}

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/DiscoveryHandler.java

@@ -0,0 +1,18 @@
+package org.briarproject.bramble.api.plugin;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.properties.TransportProperties;
+
+/**
+ * An interface for handling peers discovered by transport plugins.
+ */
+@NotNullByDefault
+public interface DiscoveryHandler {
+
+	/**
+	 * Handles a peer discovered by a transport plugin.
+	 *
+	 * @param p A set of properties describing the discovered peer.
+	 */
+	void handleDevice(TransportProperties p);
+}

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/LanTcpConstants.java

@@ -7,12 +7,7 @@ public interface LanTcpConstants {
 	// Transport properties (shared with contacts)
 	String PROP_IP_PORTS = "ipPorts";
 	String PROP_PORT = "port";
-	String PROP_IPV6 = "ipv6";
 
-	// Local settings (not shared with contacts)
+	// A local setting
 	String PREF_LAN_IP_PORTS = "ipPorts";
-	String PREF_IPV6 = "ipv6";
-
-	// Default value for PREF_PLUGIN_ENABLE
-	boolean DEFAULT_PREF_PLUGIN_ENABLE = true;
 }

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/Plugin.java

@@ -5,7 +5,7 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.properties.TransportProperties;
 import org.briarproject.bramble.api.settings.SettingsManager;
 
-import java.util.Collection;
+import java.util.List;
 
 @NotNullByDefault
 public interface Plugin {
@@ -106,6 +106,5 @@ public interface Plugin {
 	 * Attempts to create connections using the given transport properties,
 	 * passing any created connections to the corresponding handlers.
 	 */
-	void poll(Collection<Pair<TransportProperties, ConnectionHandler>>
+	void poll(List<Pair<TransportProperties, ConnectionHandler>> properties);
-			properties);
 }

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/PluginConfig.java

@@ -5,8 +5,6 @@ import org.briarproject.bramble.api.plugin.duplex.DuplexPluginFactory;
 import org.briarproject.bramble.api.plugin.simplex.SimplexPluginFactory;
 
 import java.util.Collection;
-import java.util.List;
-import java.util.Map;
 
 @NotNullByDefault
 public interface PluginConfig {
@@ -16,11 +14,4 @@ public interface PluginConfig {
 	Collection<SimplexPluginFactory> getSimplexFactories();
 
 	boolean shouldPoll();
-
-	/**
-	 * Returns a map representing transport preferences. For each entry in the
-	 * map, connections via the transports identified by the value are
-	 * preferred to connections via the transport identified by the key.
-	 */
-	Map<TransportId, List<TransportId>> getTransportPreferences();
 }

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/TorConstants.java

@@ -1,12 +1,9 @@
 package org.briarproject.bramble.api.plugin;
 
-import static java.util.concurrent.TimeUnit.DAYS;
-
 public interface TorConstants {
 
 	TransportId ID = new TransportId("org.briarproject.bramble.tor");
 
-	// Transport properties
 	String PROP_ONION_V2 = "onion";
 	String PROP_ONION_V3 = "onion3";
 
@@ -16,33 +13,17 @@ public interface TorConstants {
 	int CONNECT_TO_PROXY_TIMEOUT = 5000; // Milliseconds
 	int EXTRA_SOCKET_TIMEOUT = 30000; // Milliseconds
 
-	// Local settings (not shared with contacts)
 	String PREF_TOR_NETWORK = "network2";
 	String PREF_TOR_PORT = "port";
 	String PREF_TOR_MOBILE = "useMobileData";
 	String PREF_TOR_ONLY_WHEN_CHARGING = "onlyWhenCharging";
-	String HS_PRIVATE_KEY_V2 = "onionPrivKey";
-	String HS_PRIVATE_KEY_V3 = "onionPrivKey3";
-	String HS_V3_CREATED = "onionPrivKey3Created";
 
-	/**
-	 * How long to publish a v3 hidden service before retiring the v2 service.
-	 */
-	long V3_MIGRATION_PERIOD_MS = DAYS.toMillis(180);
-
-	// Values for PREF_TOR_NETWORK
 	int PREF_TOR_NETWORK_AUTOMATIC = 0;
 	int PREF_TOR_NETWORK_WITHOUT_BRIDGES = 1;
 	int PREF_TOR_NETWORK_WITH_BRIDGES = 2;
 	// TODO: Remove when settings migration code is removed
 	int PREF_TOR_NETWORK_NEVER = 3;
 
-	// Default values for local settings
-	boolean DEFAULT_PREF_PLUGIN_ENABLE = true;
-	int DEFAULT_PREF_TOR_NETWORK = PREF_TOR_NETWORK_AUTOMATIC;
-	boolean DEFAULT_PREF_TOR_MOBILE = true;
-	boolean DEFAULT_PREF_TOR_ONLY_WHEN_CHARGING = false;
-
 	/**
 	 * Reason flag returned by {@link Plugin#getReasonsDisabled()}.
 	 */

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/WanTcpConstants.java

@@ -4,7 +4,4 @@ public interface WanTcpConstants {
 
 	TransportId ID = new TransportId("org.briarproject.bramble.wan");
 
-	// Default value for PREF_PLUGIN_ENABLE
-	boolean DEFAULT_PREF_PLUGIN_ENABLE = false;
 }
-

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/duplex/AbstractDuplexTransportConnection.java

@@ -4,7 +4,6 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.Plugin;
 import org.briarproject.bramble.api.plugin.TransportConnectionReader;
 import org.briarproject.bramble.api.plugin.TransportConnectionWriter;
-import org.briarproject.bramble.api.properties.TransportProperties;
 
 import java.io.IOException;
 import java.io.InputStream;
@@ -15,8 +14,6 @@ import java.util.concurrent.atomic.AtomicBoolean;
 public abstract class AbstractDuplexTransportConnection
 		implements DuplexTransportConnection {
 
-	protected final TransportProperties remote = new TransportProperties();
-
 	private final Plugin plugin;
 	private final Reader reader;
 	private final Writer writer;
@@ -47,11 +44,6 @@ public abstract class AbstractDuplexTransportConnection
 		return writer;
 	}
 
-	@Override
-	public TransportProperties getRemoteProperties() {
-		return remote;
-	}
-
 	private class Reader implements TransportConnectionReader {
 
 		@Override

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/duplex/DuplexPlugin.java

@@ -1,14 +1,18 @@
 package org.briarproject.bramble.api.plugin.duplex;
 
+import org.briarproject.bramble.api.Pair;
 import org.briarproject.bramble.api.data.BdfList;
 import org.briarproject.bramble.api.keyagreement.KeyAgreementListener;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.ConnectionHandler;
+import org.briarproject.bramble.api.plugin.DiscoveryHandler;
 import org.briarproject.bramble.api.plugin.Plugin;
 import org.briarproject.bramble.api.properties.TransportProperties;
 import org.briarproject.bramble.api.rendezvous.KeyMaterialSource;
 import org.briarproject.bramble.api.rendezvous.RendezvousEndpoint;
 
+import java.util.List;
+
 import javax.annotation.Nullable;
 
 /**
@@ -58,4 +62,16 @@ public interface DuplexPlugin extends Plugin {
 	@Nullable
 	RendezvousEndpoint createRendezvousEndpoint(KeyMaterialSource k,
 			boolean alice, ConnectionHandler incoming);
+
+	/**
+	 * Returns true if the plugin supports peer discovery.
+	 */
+	boolean supportsDiscovery();
+
+	/**
+	 * Attempts to discover peers using the given transport properties, passing
+	 * any discovered peers to the corresponding handlers.
+	 */
+	void discoverPeers(List<Pair<TransportProperties, DiscoveryHandler>>
+			properties);
 }

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/duplex/DuplexTransportConnection.java

@@ -3,7 +3,6 @@ package org.briarproject.bramble.api.plugin.duplex;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.TransportConnectionReader;
 import org.briarproject.bramble.api.plugin.TransportConnectionWriter;
-import org.briarproject.bramble.api.properties.TransportProperties;
 
 /**
  * An interface for reading and writing data over a duplex transport. The
@@ -24,10 +23,4 @@ public interface DuplexTransportConnection {
 	 * for writing to the connection.
 	 */
 	TransportConnectionWriter getWriter();
-
-	/**
-	 * Returns a possibly empty set of {@link TransportProperties} describing
-	 * the remote peer.
-	 */
-	TransportProperties getRemoteProperties();
 }

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/event/ConnectionClosedEvent.java

@@ -13,14 +13,13 @@ public class ConnectionClosedEvent extends Event {
 
 	private final ContactId contactId;
 	private final TransportId transportId;
-	private final boolean incoming, exception;
+	private final boolean incoming;
 
 	public ConnectionClosedEvent(ContactId contactId, TransportId transportId,
-			boolean incoming, boolean exception) {
+			boolean incoming) {
 		this.contactId = contactId;
 		this.transportId = transportId;
 		this.incoming = incoming;
-		this.exception = exception;
 	}
 
 	public ContactId getContactId() {
@@ -34,8 +33,4 @@ public class ConnectionClosedEvent extends Event {
 	public boolean isIncoming() {
 		return incoming;
 	}
-
-	public boolean isException() {
-		return exception;
-	}
 }

bramble-api/src/main/java/org/briarproject/bramble/api/properties/TransportPropertyConstants.java

@@ -11,28 +11,4 @@ public interface TransportPropertyConstants {
 	 * The maximum length of a property's key or value in UTF-8 bytes.
 	 */
 	int MAX_PROPERTY_LENGTH = 100;
-
-	/**
-	 * Message metadata key for the transport ID of a local or remote update,
-	 * as a BDF string.
-	 */
-	String MSG_KEY_TRANSPORT_ID = "transportId";
-
-	/**
-	 * Message metadata key for the version number of a local or remote update,
-	 * as a BDF long.
-	 */
-	String MSG_KEY_VERSION = "version";
-
-	/**
-	 * Message metadata key for whether an update is local or remote, as a BDF
-	 * boolean.
-	 */
-	String MSG_KEY_LOCAL = "local";
-
-	/**
-	 * Group metadata key for any discovered transport properties of the
-	 * contact, as a BDF dictionary.
-	 */
-	String GROUP_KEY_DISCOVERED = "discovered";
 }

bramble-api/src/main/java/org/briarproject/bramble/api/properties/TransportPropertyManager.java

@@ -34,14 +34,6 @@ public interface TransportPropertyManager {
 	void addRemoteProperties(Transaction txn, ContactId c,
 			Map<TransportId, TransportProperties> props) throws DbException;
 
-	/**
-	 * Stores the given properties discovered from an incoming transport
-	 * connection. They will be overridden by any properties received while
-	 * adding the contact or synced from the contact.
-	 */
-	void addRemotePropertiesFromConnection(ContactId c, TransportId t,
-			TransportProperties props) throws DbException;
-
 	/**
 	 * Returns the local transport properties for all transports.
 	 */

bramble-api/src/main/java/org/briarproject/bramble/api/sync/Priority.java

@@ -1,23 +0,0 @@
-package org.briarproject.bramble.api.sync;
-
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-
-import javax.annotation.concurrent.Immutable;
-
-/**
- * A record containing a nonce for choosing between redundant sessions.
- */
-@Immutable
-@NotNullByDefault
-public class Priority {
-
-	private final byte[] nonce;
-
-	public Priority(byte[] nonce) {
-		this.nonce = nonce;
-	}
-
-	public byte[] getNonce() {
-		return nonce;
-	}
-}

bramble-api/src/main/java/org/briarproject/bramble/api/sync/PriorityHandler.java

@@ -1,13 +0,0 @@
-package org.briarproject.bramble.api.sync;
-
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-
-/**
- * An interface for handling a {@link Priority} record received by an
- * incoming {@link SyncSession}.
- */
-@NotNullByDefault
-public interface PriorityHandler {
-
-	void handle(Priority p);
-}

bramble-api/src/main/java/org/briarproject/bramble/api/sync/RecordTypes.java

@@ -10,5 +10,4 @@ public interface RecordTypes {
 	byte OFFER = 2;
 	byte REQUEST = 3;
 	byte VERSIONS = 4;
-	byte PRIORITY = 5;
 }

bramble-api/src/main/java/org/briarproject/bramble/api/sync/SyncConstants.java

@@ -49,10 +49,4 @@ public interface SyncConstants {
 	 * simultaneously.
 	 */
 	int MAX_SUPPORTED_VERSIONS = 10;
-
-	/**
-	 * The length of the priority nonce used for choosing between redundant
-	 * connections.
-	 */
-	int PRIORITY_NONCE_BYTES = 16;
 }

bramble-api/src/main/java/org/briarproject/bramble/api/sync/SyncRecordReader.java

@@ -28,8 +28,4 @@ public interface SyncRecordReader {
 	boolean hasVersions() throws IOException;
 
 	Versions readVersions() throws IOException;
-
-	boolean hasPriority() throws IOException;
-
-	Priority readPriority() throws IOException;
 }

bramble-api/src/main/java/org/briarproject/bramble/api/sync/SyncRecordWriter.java

@@ -17,7 +17,5 @@ public interface SyncRecordWriter {
 
 	void writeVersions(Versions v) throws IOException;
 
-	void writePriority(Priority p) throws IOException;
-
 	void flush() throws IOException;
 }

bramble-api/src/main/java/org/briarproject/bramble/api/sync/SyncSessionFactory.java

@@ -2,23 +2,18 @@ package org.briarproject.bramble.api.sync;
 
 import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.transport.StreamWriter;
 
 import java.io.InputStream;
 
-import javax.annotation.Nullable;
-
 @NotNullByDefault
 public interface SyncSessionFactory {
 
-	SyncSession createIncomingSession(ContactId c, InputStream in,
+	SyncSession createIncomingSession(ContactId c, InputStream in);
-			PriorityHandler handler);
 
-	SyncSession createSimplexOutgoingSession(ContactId c, TransportId t,
+	SyncSession createSimplexOutgoingSession(ContactId c, int maxLatency,
-			int maxLatency, StreamWriter streamWriter);
+			StreamWriter streamWriter);
 
-	SyncSession createDuplexOutgoingSession(ContactId c, TransportId t,
+	SyncSession createDuplexOutgoingSession(ContactId c, int maxLatency,
-			int maxLatency, int maxIdleTime, StreamWriter streamWriter,
+			int maxIdleTime, StreamWriter streamWriter);
-			@Nullable Priority priority);
 }

bramble-api/src/main/java/org/briarproject/bramble/api/sync/event/CloseSyncConnectionsEvent.java

@@ -1,26 +0,0 @@
-package org.briarproject.bramble.api.sync.event;
-
-import org.briarproject.bramble.api.event.Event;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.plugin.TransportId;
-
-import javax.annotation.concurrent.Immutable;
-
-/**
- * An event that is broadcast when all sync connections using a given
- * transport should be closed.
- */
-@Immutable
-@NotNullByDefault
-public class CloseSyncConnectionsEvent extends Event {
-
-	private final TransportId transportId;
-
-	public CloseSyncConnectionsEvent(TransportId transportId) {
-		this.transportId = transportId;
-	}
-
-	public TransportId getTransportId() {
-		return transportId;
-	}
-}

bramble-api/src/main/java/org/briarproject/bramble/util/IoUtils.java

@@ -117,10 +117,4 @@ public class IoUtils {
 			throw new IOException(e);
 		}
 	}
-
-	public static boolean isNonEmptyDirectory(File f) {
-		if (!f.isDirectory()) return false;
-		File[] children = f.listFiles();
-		return children != null && children.length > 0;
-	}
 }

bramble-api/src/main/java/org/briarproject/bramble/util/PrivacyUtils.java

@@ -2,17 +2,13 @@ package org.briarproject.bramble.util;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 
-import java.net.Inet4Address;
+import java.net.Inet6Address;
 import java.net.InetAddress;
 import java.net.InetSocketAddress;
 import java.net.SocketAddress;
 
 import javax.annotation.Nullable;
 
-import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
-import static org.briarproject.bramble.util.StringUtils.isValidMac;
-import static org.briarproject.bramble.util.StringUtils.toHexString;
-
 @NotNullByDefault
 public class PrivacyUtils {
 
@@ -23,7 +19,7 @@ public class PrivacyUtils {
 
 	@Nullable
 	public static String scrubMacAddress(@Nullable String address) {
-		if (isNullOrEmpty(address) || !isValidMac(address)) return address;
+		if (address == null || address.length() == 0) return null;
 		// this is a fake address we need to know about
 		if (address.equals("02:00:00:00:00:00")) return address;
 		// keep first and last octet of MAC address
@@ -31,37 +27,39 @@ public class PrivacyUtils {
 				+ address.substring(14, 17);
 	}
 
+	@Nullable
 	public static String scrubInetAddress(InetAddress address) {
-		if (address instanceof Inet4Address) {
+		// don't scrub link and site local addresses
-			// Don't scrub local IPv4 addresses
+		if (address.isLinkLocalAddress() || address.isSiteLocalAddress())
-			if (address.isLoopbackAddress() || address.isLinkLocalAddress() ||
+			return address.toString();
-					address.isSiteLocalAddress()) {
+		// completely scrub IPv6 addresses
-				return address.getHostAddress();
+		if (address instanceof Inet6Address) return "[scrubbed]";
-			}
+		// keep first and last octet of IPv4 addresses
-			// Keep first and last octet of non-local IPv4 addresses
+		return scrubInetAddress(address.toString());
-			return scrubIpv4Address(address.getAddress());
-		} else {
-			// Keep first and last octet of IPv6 addresses
-			return scrubIpv6Address(address.getAddress());
-		}
 	}
 
-	private static String scrubIpv4Address(byte[] ipv4) {
+	@Nullable
-		return (ipv4[0] & 0xFF) + ".[scrubbed]." + (ipv4[3] & 0xFF);
+	public static String scrubInetAddress(@Nullable String address) {
-	}
+		if (address == null) return null;
-
+
-	private static String scrubIpv6Address(byte[] ipv6) {
+		int firstDot = address.indexOf(".");
-		String hex = toHexString(ipv6).toLowerCase();
+		if (firstDot == -1) return "[scrubbed]";
-		return hex.substring(0, 2) + "[scrubbed]" + hex.substring(30);
+		String prefix = address.substring(0, firstDot + 1);
+		int lastDot = address.lastIndexOf(".");
+		String suffix = address.substring(lastDot, address.length());
+		return prefix + "[scrubbed]" + suffix;
 	}
 
+	@Nullable
 	public static String scrubSocketAddress(InetSocketAddress address) {
-		return scrubInetAddress(address.getAddress());
+		InetAddress inetAddress = address.getAddress();
+		return scrubInetAddress(inetAddress);
 	}
 
+	@Nullable
 	public static String scrubSocketAddress(SocketAddress address) {
 		if (address instanceof InetSocketAddress)
 			return scrubSocketAddress((InetSocketAddress) address);
-		return "[scrubbed]";
+		return scrubInetAddress(address.toString());
 	}
 }

bramble-core/src/main/java/org/briarproject/bramble/BrambleCoreModule.java

@@ -1,7 +1,6 @@
 package org.briarproject.bramble;
 
 import org.briarproject.bramble.client.ClientModule;
-import org.briarproject.bramble.connection.ConnectionModule;
 import org.briarproject.bramble.contact.ContactModule;
 import org.briarproject.bramble.crypto.CryptoExecutorModule;
 import org.briarproject.bramble.crypto.CryptoModule;
@@ -10,7 +9,6 @@ import org.briarproject.bramble.db.DatabaseExecutorModule;
 import org.briarproject.bramble.db.DatabaseModule;
 import org.briarproject.bramble.event.EventModule;
 import org.briarproject.bramble.identity.IdentityModule;
-import org.briarproject.bramble.io.IoModule;
 import org.briarproject.bramble.keyagreement.KeyAgreementModule;
 import org.briarproject.bramble.lifecycle.LifecycleModule;
 import org.briarproject.bramble.plugin.PluginModule;
@@ -29,7 +27,6 @@ import dagger.Module;
 
 @Module(includes = {
 		ClientModule.class,
-		ConnectionModule.class,
 		ContactModule.class,
 		CryptoModule.class,
 		CryptoExecutorModule.class,
@@ -38,7 +35,6 @@ import dagger.Module;
 		DatabaseExecutorModule.class,
 		EventModule.class,
 		IdentityModule.class,
-		IoModule.class,
 		KeyAgreementModule.class,
 		LifecycleModule.class,
 		PluginModule.class,

bramble-core/src/main/java/org/briarproject/bramble/account/AccountManagerImpl.java

@@ -2,7 +2,6 @@ package org.briarproject.bramble.account;
 
 import org.briarproject.bramble.api.account.AccountManager;
 import org.briarproject.bramble.api.crypto.CryptoComponent;
-import org.briarproject.bramble.api.crypto.DecryptionException;
 import org.briarproject.bramble.api.crypto.KeyStrengthener;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.db.DatabaseConfig;
@@ -18,7 +17,6 @@ import java.io.FileInputStream;
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.InputStreamReader;
-import java.nio.charset.Charset;
 import java.util.logging.Logger;
 
 import javax.annotation.Nullable;
@@ -26,7 +24,6 @@ import javax.annotation.concurrent.GuardedBy;
 import javax.inject.Inject;
 
 import static java.util.logging.Level.WARNING;
-import static org.briarproject.bramble.api.crypto.DecryptionResult.INVALID_CIPHERTEXT;
 import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.bramble.util.StringUtils.fromHexString;
 import static org.briarproject.bramble.util.StringUtils.toHexString;
@@ -98,7 +95,7 @@ class AccountManagerImpl implements AccountManager {
 		}
 		try {
 			BufferedReader reader = new BufferedReader(new InputStreamReader(
-					new FileInputStream(f), Charset.forName("UTF-8")));
+					new FileInputStream(f), "UTF-8"));
 			String key = reader.readLine();
 			reader.close();
 			return key;
@@ -150,7 +147,7 @@ class AccountManagerImpl implements AccountManager {
 	@GuardedBy("stateChangeLock")
 	private void writeDbKeyToFile(String key, File f) throws IOException {
 		FileOutputStream out = new FileOutputStream(f);
-		out.write(key.getBytes(Charset.forName("UTF-8")));
+		out.write(key.getBytes("UTF-8"));
 		out.flush();
 		out.close();
 	}
@@ -158,7 +155,8 @@ class AccountManagerImpl implements AccountManager {
 	@Override
 	public boolean accountExists() {
 		synchronized (stateChangeLock) {
-			return loadEncryptedDatabaseKey() != null;
+			return loadEncryptedDatabaseKey() != null
+					&& databaseConfig.getDatabaseDirectory().isDirectory();
 		}
 	}
 
@@ -195,24 +193,31 @@ class AccountManagerImpl implements AccountManager {
 	}
 
 	@Override
-	public void signIn(String password) throws DecryptionException {
+	public boolean signIn(String password) {
 		synchronized (stateChangeLock) {
-			databaseKey = loadAndDecryptDatabaseKey(password);
+			SecretKey key = loadAndDecryptDatabaseKey(password);
+			if (key == null) return false;
+			databaseKey = key;
+			return true;
 		}
 	}
 
 	@GuardedBy("stateChangeLock")
-	private SecretKey loadAndDecryptDatabaseKey(String password)
+	@Nullable
-			throws DecryptionException {
+	private SecretKey loadAndDecryptDatabaseKey(String password) {
 		String hex = loadEncryptedDatabaseKey();
 		if (hex == null) {
 			LOG.warning("Failed to load encrypted database key");
-			throw new DecryptionException(INVALID_CIPHERTEXT);
+			return null;
 		}
 		byte[] ciphertext = fromHexString(hex);
 		KeyStrengthener keyStrengthener = databaseConfig.getKeyStrengthener();
 		byte[] plaintext = crypto.decryptWithPassword(ciphertext, password,
 				keyStrengthener);
+		if (plaintext == null) {
+			LOG.info("Failed to decrypt database key");
+			return null;
+		}
 		SecretKey key = new SecretKey(plaintext);
 		// If the DB key was encrypted with a weak key and a key strengthener
 		// is now available, re-encrypt the DB key with a strengthened key
@@ -225,11 +230,10 @@ class AccountManagerImpl implements AccountManager {
 	}
 
 	@Override
-	public void changePassword(String oldPassword, String newPassword)
+	public boolean changePassword(String oldPassword, String newPassword) {
-			throws DecryptionException {
 		synchronized (stateChangeLock) {
 			SecretKey key = loadAndDecryptDatabaseKey(oldPassword);
-			encryptAndStoreDatabaseKey(key, newPassword);
+			return key != null && encryptAndStoreDatabaseKey(key, newPassword);
 		}
 	}
 }

bramble-core/src/main/java/org/briarproject/bramble/connection/Connection.java

@@ -1,79 +0,0 @@
-package org.briarproject.bramble.connection;
-
-import org.briarproject.bramble.api.connection.ConnectionRegistry;
-import org.briarproject.bramble.api.db.DbException;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.plugin.TransportConnectionReader;
-import org.briarproject.bramble.api.plugin.TransportConnectionWriter;
-import org.briarproject.bramble.api.plugin.TransportId;
-import org.briarproject.bramble.api.transport.KeyManager;
-import org.briarproject.bramble.api.transport.StreamContext;
-import org.briarproject.bramble.api.transport.StreamReaderFactory;
-import org.briarproject.bramble.api.transport.StreamWriterFactory;
-
-import java.io.IOException;
-import java.io.InputStream;
-import java.util.logging.Logger;
-
-import javax.annotation.Nullable;
-
-import static java.util.logging.Level.WARNING;
-import static java.util.logging.Logger.getLogger;
-import static org.briarproject.bramble.api.transport.TransportConstants.TAG_LENGTH;
-import static org.briarproject.bramble.util.IoUtils.read;
-import static org.briarproject.bramble.util.LogUtils.logException;
-
-@NotNullByDefault
-abstract class Connection {
-
-	protected static final Logger LOG = getLogger(Connection.class.getName());
-
-	final KeyManager keyManager;
-	final ConnectionRegistry connectionRegistry;
-	final StreamReaderFactory streamReaderFactory;
-	final StreamWriterFactory streamWriterFactory;
-
-	Connection(KeyManager keyManager, ConnectionRegistry connectionRegistry,
-			StreamReaderFactory streamReaderFactory,
-			StreamWriterFactory streamWriterFactory) {
-		this.keyManager = keyManager;
-		this.connectionRegistry = connectionRegistry;
-		this.streamReaderFactory = streamReaderFactory;
-		this.streamWriterFactory = streamWriterFactory;
-	}
-
-	@Nullable
-	StreamContext recogniseTag(TransportConnectionReader reader,
-			TransportId transportId) {
-		StreamContext ctx;
-		try {
-			byte[] tag = readTag(reader.getInputStream());
-			return keyManager.getStreamContext(transportId, tag);
-		} catch (IOException | DbException e) {
-			logException(LOG, WARNING, e);
-			return null;
-		}
-	}
-
-	private byte[] readTag(InputStream in) throws IOException {
-		byte[] tag = new byte[TAG_LENGTH];
-		read(in, tag);
-		return tag;
-	}
-
-	void disposeOnError(TransportConnectionReader reader, boolean recognised) {
-		try {
-			reader.dispose(true, recognised);
-		} catch (IOException e) {
-			logException(LOG, WARNING, e);
-		}
-	}
-
-	void disposeOnError(TransportConnectionWriter writer) {
-		try {
-			writer.dispose(true);
-		} catch (IOException e) {
-			logException(LOG, WARNING, e);
-		}
-	}
-}

bramble-core/src/main/java/org/briarproject/bramble/connection/ConnectionManagerImpl.java

@@ -1,114 +0,0 @@
-package org.briarproject.bramble.connection;
-
-import org.briarproject.bramble.api.connection.ConnectionManager;
-import org.briarproject.bramble.api.connection.ConnectionRegistry;
-import org.briarproject.bramble.api.contact.ContactExchangeManager;
-import org.briarproject.bramble.api.contact.ContactId;
-import org.briarproject.bramble.api.contact.HandshakeManager;
-import org.briarproject.bramble.api.contact.PendingContactId;
-import org.briarproject.bramble.api.lifecycle.IoExecutor;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.plugin.TransportConnectionReader;
-import org.briarproject.bramble.api.plugin.TransportConnectionWriter;
-import org.briarproject.bramble.api.plugin.TransportId;
-import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
-import org.briarproject.bramble.api.properties.TransportPropertyManager;
-import org.briarproject.bramble.api.sync.SyncSessionFactory;
-import org.briarproject.bramble.api.transport.KeyManager;
-import org.briarproject.bramble.api.transport.StreamReaderFactory;
-import org.briarproject.bramble.api.transport.StreamWriterFactory;
-
-import java.security.SecureRandom;
-import java.util.concurrent.Executor;
-
-import javax.annotation.concurrent.Immutable;
-import javax.inject.Inject;
-
-@Immutable
-@NotNullByDefault
-class ConnectionManagerImpl implements ConnectionManager {
-
-	private final Executor ioExecutor;
-	private final KeyManager keyManager;
-	private final StreamReaderFactory streamReaderFactory;
-	private final StreamWriterFactory streamWriterFactory;
-	private final SyncSessionFactory syncSessionFactory;
-	private final HandshakeManager handshakeManager;
-	private final ContactExchangeManager contactExchangeManager;
-	private final ConnectionRegistry connectionRegistry;
-	private final TransportPropertyManager transportPropertyManager;
-	private final SecureRandom secureRandom;
-
-	@Inject
-	ConnectionManagerImpl(@IoExecutor Executor ioExecutor,
-			KeyManager keyManager, StreamReaderFactory streamReaderFactory,
-			StreamWriterFactory streamWriterFactory,
-			SyncSessionFactory syncSessionFactory,
-			HandshakeManager handshakeManager,
-			ContactExchangeManager contactExchangeManager,
-			ConnectionRegistry connectionRegistry,
-			TransportPropertyManager transportPropertyManager,
-			SecureRandom secureRandom) {
-		this.ioExecutor = ioExecutor;
-		this.keyManager = keyManager;
-		this.streamReaderFactory = streamReaderFactory;
-		this.streamWriterFactory = streamWriterFactory;
-		this.syncSessionFactory = syncSessionFactory;
-		this.handshakeManager = handshakeManager;
-		this.contactExchangeManager = contactExchangeManager;
-		this.connectionRegistry = connectionRegistry;
-		this.transportPropertyManager = transportPropertyManager;
-		this.secureRandom = secureRandom;
-	}
-
-
-	@Override
-	public void manageIncomingConnection(TransportId t,
-			TransportConnectionReader r) {
-		ioExecutor.execute(new IncomingSimplexSyncConnection(keyManager,
-				connectionRegistry, streamReaderFactory, streamWriterFactory,
-				syncSessionFactory, transportPropertyManager, t, r));
-	}
-
-	@Override
-	public void manageIncomingConnection(TransportId t,
-			DuplexTransportConnection d) {
-		ioExecutor.execute(new IncomingDuplexSyncConnection(keyManager,
-				connectionRegistry, streamReaderFactory, streamWriterFactory,
-				syncSessionFactory, transportPropertyManager, ioExecutor,
-				t, d));
-	}
-
-	@Override
-	public void manageIncomingConnection(PendingContactId p, TransportId t,
-			DuplexTransportConnection d) {
-		ioExecutor.execute(new IncomingHandshakeConnection(keyManager,
-				connectionRegistry, streamReaderFactory, streamWriterFactory,
-				handshakeManager, contactExchangeManager, this, p, t, d));
-	}
-
-	@Override
-	public void manageOutgoingConnection(ContactId c, TransportId t,
-			TransportConnectionWriter w) {
-		ioExecutor.execute(new OutgoingSimplexSyncConnection(keyManager,
-				connectionRegistry, streamReaderFactory, streamWriterFactory,
-				syncSessionFactory, transportPropertyManager, c, t, w));
-	}
-
-	@Override
-	public void manageOutgoingConnection(ContactId c, TransportId t,
-			DuplexTransportConnection d) {
-		ioExecutor.execute(new OutgoingDuplexSyncConnection(keyManager,
-				connectionRegistry, streamReaderFactory, streamWriterFactory,
-				syncSessionFactory, transportPropertyManager, ioExecutor,
-				secureRandom, c, t, d));
-	}
-
-	@Override
-	public void manageOutgoingConnection(PendingContactId p, TransportId t,
-			DuplexTransportConnection d) {
-		ioExecutor.execute(new OutgoingHandshakeConnection(keyManager,
-				connectionRegistry, streamReaderFactory, streamWriterFactory,
-				handshakeManager, contactExchangeManager, this, p, t, d));
-	}
-}

bramble-core/src/main/java/org/briarproject/bramble/connection/ConnectionModule.java

@@ -1,26 +0,0 @@
-package org.briarproject.bramble.connection;
-
-import org.briarproject.bramble.api.connection.ConnectionManager;
-import org.briarproject.bramble.api.connection.ConnectionRegistry;
-
-import javax.inject.Singleton;
-
-import dagger.Module;
-import dagger.Provides;
-
-@Module
-public class ConnectionModule {
-
-	@Provides
-	ConnectionManager provideConnectionManager(
-			ConnectionManagerImpl connectionManager) {
-		return connectionManager;
-	}
-
-	@Provides
-	@Singleton
-	ConnectionRegistry provideConnectionRegistry(
-			ConnectionRegistryImpl connectionRegistry) {
-		return connectionRegistry;
-	}
-}

bramble-core/src/main/java/org/briarproject/bramble/connection/ConnectionRegistryImpl.java

@@ -1,283 +0,0 @@
-package org.briarproject.bramble.connection;
-
-import org.briarproject.bramble.api.Bytes;
-import org.briarproject.bramble.api.connection.ConnectionRegistry;
-import org.briarproject.bramble.api.connection.InterruptibleConnection;
-import org.briarproject.bramble.api.contact.ContactId;
-import org.briarproject.bramble.api.contact.PendingContactId;
-import org.briarproject.bramble.api.event.EventBus;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.plugin.PluginConfig;
-import org.briarproject.bramble.api.plugin.TransportId;
-import org.briarproject.bramble.api.plugin.event.ConnectionClosedEvent;
-import org.briarproject.bramble.api.plugin.event.ConnectionOpenedEvent;
-import org.briarproject.bramble.api.plugin.event.ContactConnectedEvent;
-import org.briarproject.bramble.api.plugin.event.ContactDisconnectedEvent;
-import org.briarproject.bramble.api.rendezvous.event.RendezvousConnectionClosedEvent;
-import org.briarproject.bramble.api.rendezvous.event.RendezvousConnectionOpenedEvent;
-import org.briarproject.bramble.api.sync.Priority;
-
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.HashMap;
-import java.util.HashSet;
-import java.util.List;
-import java.util.Map;
-import java.util.Map.Entry;
-import java.util.Set;
-import java.util.logging.Logger;
-
-import javax.annotation.Nullable;
-import javax.annotation.concurrent.GuardedBy;
-import javax.annotation.concurrent.ThreadSafe;
-import javax.inject.Inject;
-
-import static java.util.Collections.emptyList;
-import static java.util.logging.Level.INFO;
-import static java.util.logging.Logger.getLogger;
-
-@ThreadSafe
-@NotNullByDefault
-class ConnectionRegistryImpl implements ConnectionRegistry {
-
-	private static final Logger LOG =
-			getLogger(ConnectionRegistryImpl.class.getName());
-
-	private final EventBus eventBus;
-	private final Map<TransportId, List<TransportId>> transportPrefs;
-
-	private final Object lock = new Object();
-	@GuardedBy("lock")
-	private final Map<ContactId, List<ConnectionRecord>> contactConnections;
-	@GuardedBy("lock")
-	private final Set<PendingContactId> connectedPendingContacts;
-
-	@Inject
-	ConnectionRegistryImpl(EventBus eventBus, PluginConfig pluginConfig) {
-		this.eventBus = eventBus;
-		transportPrefs = pluginConfig.getTransportPreferences();
-		contactConnections = new HashMap<>();
-		connectedPendingContacts = new HashSet<>();
-	}
-
-	@Override
-	public void registerIncomingConnection(ContactId c, TransportId t,
-			InterruptibleConnection conn) {
-		registerConnection(c, t, conn, true);
-	}
-
-	@Override
-	public void registerOutgoingConnection(ContactId c, TransportId t,
-			InterruptibleConnection conn, Priority priority) {
-		registerConnection(c, t, conn, false);
-		setPriority(c, t, conn, priority);
-	}
-
-	private void registerConnection(ContactId c, TransportId t,
-			InterruptibleConnection conn, boolean incoming) {
-		if (LOG.isLoggable(INFO)) {
-			if (incoming) LOG.info("Incoming connection registered: " + t);
-			else LOG.info("Outgoing connection registered: " + t);
-		}
-		boolean firstConnection;
-		synchronized (lock) {
-			List<ConnectionRecord> recs = contactConnections.get(c);
-			if (recs == null) {
-				recs = new ArrayList<>();
-				contactConnections.put(c, recs);
-			}
-			firstConnection = recs.isEmpty();
-			recs.add(new ConnectionRecord(t, conn));
-		}
-		eventBus.broadcast(new ConnectionOpenedEvent(c, t, incoming));
-		if (firstConnection) {
-			LOG.info("Contact connected");
-			eventBus.broadcast(new ContactConnectedEvent(c));
-		}
-	}
-
-	@Override
-	public void setPriority(ContactId c, TransportId t,
-			InterruptibleConnection conn, Priority priority) {
-		if (LOG.isLoggable(INFO)) LOG.info("Setting connection priority: " + t);
-		List<InterruptibleConnection> toInterrupt;
-		boolean interruptNewConnection = false;
-		synchronized (lock) {
-			List<ConnectionRecord> recs = contactConnections.get(c);
-			if (recs == null) throw new IllegalArgumentException();
-			toInterrupt = new ArrayList<>(recs.size());
-			for (ConnectionRecord rec : recs) {
-				if (rec.conn == conn) {
-					// Store the priority of this connection
-					rec.priority = priority;
-				} else if (rec.priority != null) {
-					int compare = compareConnections(t, priority,
-							rec.transportId, rec.priority);
-					if (compare == -1) {
-						// The old connection is better than the new one
-						interruptNewConnection = true;
-					} else if (compare == 1 && !rec.interrupted) {
-						// The new connection is better than the old one
-						toInterrupt.add(rec.conn);
-						rec.interrupted = true;
-					}
-				}
-			}
-		}
-		if (interruptNewConnection) {
-			LOG.info("Interrupting new connection");
-			conn.interruptOutgoingSession();
-		}
-		for (InterruptibleConnection old : toInterrupt) {
-			LOG.info("Interrupting old connection");
-			old.interruptOutgoingSession();
-		}
-	}
-
-	private int compareConnections(TransportId tA, Priority pA, TransportId tB,
-			Priority pB) {
-		if (getBetterTransports(tA).contains(tB)) return -1;
-		if (getBetterTransports(tB).contains(tA)) return 1;
-		return tA.equals(tB) ? Bytes.compare(pA.getNonce(), pB.getNonce()) : 0;
-	}
-
-	private List<TransportId> getBetterTransports(TransportId t) {
-		List<TransportId> better = transportPrefs.get(t);
-		return better == null ? emptyList() : better;
-	}
-
-	@Override
-	public void unregisterConnection(ContactId c, TransportId t,
-			InterruptibleConnection conn, boolean incoming, boolean exception) {
-		if (LOG.isLoggable(INFO)) {
-			if (incoming) LOG.info("Incoming connection unregistered: " + t);
-			else LOG.info("Outgoing connection unregistered: " + t);
-		}
-		boolean lastConnection;
-		synchronized (lock) {
-			List<ConnectionRecord> recs = contactConnections.get(c);
-			if (recs == null || !recs.remove(new ConnectionRecord(t, conn)))
-				throw new IllegalArgumentException();
-			lastConnection = recs.isEmpty();
-		}
-		eventBus.broadcast(
-				new ConnectionClosedEvent(c, t, incoming, exception));
-		if (lastConnection) {
-			LOG.info("Contact disconnected");
-			eventBus.broadcast(new ContactDisconnectedEvent(c));
-		}
-	}
-
-	@Override
-	public Collection<ContactId> getConnectedContacts(TransportId t) {
-		synchronized (lock) {
-			List<ContactId> contactIds = new ArrayList<>();
-			for (Entry<ContactId, List<ConnectionRecord>> e :
-					contactConnections.entrySet()) {
-				for (ConnectionRecord rec : e.getValue()) {
-					if (rec.transportId.equals(t)) {
-						contactIds.add(e.getKey());
-						break;
-					}
-				}
-			}
-			if (LOG.isLoggable(INFO)) {
-				LOG.info(contactIds.size() + " contacts connected: " + t);
-			}
-			return contactIds;
-		}
-	}
-
-	@Override
-	public Collection<ContactId> getConnectedOrBetterContacts(TransportId t) {
-		synchronized (lock) {
-			List<TransportId> better = getBetterTransports(t);
-			List<ContactId> contactIds = new ArrayList<>();
-			for (Entry<ContactId, List<ConnectionRecord>> e :
-					contactConnections.entrySet()) {
-				for (ConnectionRecord rec : e.getValue()) {
-					if (rec.transportId.equals(t) ||
-							better.contains(rec.transportId)) {
-						contactIds.add(e.getKey());
-						break;
-					}
-				}
-			}
-			if (LOG.isLoggable(INFO)) {
-				LOG.info(contactIds.size()
-						+ " contacts connected or better: " + t);
-			}
-			return contactIds;
-		}
-	}
-
-	@Override
-	public boolean isConnected(ContactId c, TransportId t) {
-		synchronized (lock) {
-			List<ConnectionRecord> recs = contactConnections.get(c);
-			if (recs == null) return false;
-			for (ConnectionRecord rec : recs) {
-				if (rec.transportId.equals(t)) return true;
-			}
-			return false;
-		}
-	}
-
-	@Override
-	public boolean isConnected(ContactId c) {
-		synchronized (lock) {
-			List<ConnectionRecord> recs = contactConnections.get(c);
-			return recs != null && !recs.isEmpty();
-		}
-	}
-
-	@Override
-	public boolean registerConnection(PendingContactId p) {
-		boolean added;
-		synchronized (lock) {
-			added = connectedPendingContacts.add(p);
-		}
-		if (added) eventBus.broadcast(new RendezvousConnectionOpenedEvent(p));
-		return added;
-	}
-
-	@Override
-	public void unregisterConnection(PendingContactId p, boolean success) {
-		synchronized (lock) {
-			if (!connectedPendingContacts.remove(p))
-				throw new IllegalArgumentException();
-		}
-		eventBus.broadcast(new RendezvousConnectionClosedEvent(p, success));
-	}
-
-	private static class ConnectionRecord {
-
-		private final TransportId transportId;
-		private final InterruptibleConnection conn;
-		@GuardedBy("lock")
-		@Nullable
-		private Priority priority = null;
-		@GuardedBy("lock")
-		private boolean interrupted = false;
-
-		private ConnectionRecord(TransportId transportId,
-				InterruptibleConnection conn) {
-			this.transportId = transportId;
-			this.conn = conn;
-		}
-
-		@Override
-		public boolean equals(Object o) {
-			if (o instanceof ConnectionRecord) {
-				return conn == ((ConnectionRecord) o).conn;
-			} else {
-				return false;
-			}
-		}
-
-		@Override
-		public int hashCode() {
-			return conn.hashCode();
-		}
-	}
-}

bramble-core/src/main/java/org/briarproject/bramble/connection/DuplexSyncConnection.java

@@ -1,109 +0,0 @@
-package org.briarproject.bramble.connection;
-
-import org.briarproject.bramble.api.connection.ConnectionRegistry;
-import org.briarproject.bramble.api.connection.InterruptibleConnection;
-import org.briarproject.bramble.api.contact.ContactId;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.plugin.TransportConnectionReader;
-import org.briarproject.bramble.api.plugin.TransportConnectionWriter;
-import org.briarproject.bramble.api.plugin.TransportId;
-import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
-import org.briarproject.bramble.api.properties.TransportProperties;
-import org.briarproject.bramble.api.properties.TransportPropertyManager;
-import org.briarproject.bramble.api.sync.Priority;
-import org.briarproject.bramble.api.sync.SyncSession;
-import org.briarproject.bramble.api.sync.SyncSessionFactory;
-import org.briarproject.bramble.api.transport.KeyManager;
-import org.briarproject.bramble.api.transport.StreamContext;
-import org.briarproject.bramble.api.transport.StreamReaderFactory;
-import org.briarproject.bramble.api.transport.StreamWriter;
-import org.briarproject.bramble.api.transport.StreamWriterFactory;
-
-import java.io.IOException;
-import java.util.concurrent.Executor;
-
-import javax.annotation.Nullable;
-import javax.annotation.concurrent.GuardedBy;
-
-import static org.briarproject.bramble.api.nullsafety.NullSafety.requireNonNull;
-
-@NotNullByDefault
-abstract class DuplexSyncConnection extends SyncConnection
-		implements InterruptibleConnection {
-
-	final Executor ioExecutor;
-	final TransportId transportId;
-	final TransportConnectionReader reader;
-	final TransportConnectionWriter writer;
-	final TransportProperties remote;
-
-	private final Object interruptLock = new Object();
-
-	@GuardedBy("interruptLock")
-	@Nullable
-	private SyncSession outgoingSession = null;
-	@GuardedBy("interruptLock")
-	private boolean interruptWaiting = false;
-
-	@Override
-	public void interruptOutgoingSession() {
-		SyncSession out = null;
-		synchronized (interruptLock) {
-			if (outgoingSession == null) interruptWaiting = true;
-			else out = outgoingSession;
-		}
-		if (out != null) out.interrupt();
-	}
-
-	void setOutgoingSession(SyncSession outgoingSession) {
-		boolean interruptWasWaiting = false;
-		synchronized (interruptLock) {
-			this.outgoingSession = outgoingSession;
-			if (interruptWaiting) {
-				interruptWasWaiting = true;
-				interruptWaiting = false;
-			}
-		}
-		if (interruptWasWaiting) outgoingSession.interrupt();
-	}
-
-	DuplexSyncConnection(KeyManager keyManager,
-			ConnectionRegistry connectionRegistry,
-			StreamReaderFactory streamReaderFactory,
-			StreamWriterFactory streamWriterFactory,
-			SyncSessionFactory syncSessionFactory,
-			TransportPropertyManager transportPropertyManager,
-			Executor ioExecutor, TransportId transportId,
-			DuplexTransportConnection connection) {
-		super(keyManager, connectionRegistry, streamReaderFactory,
-				streamWriterFactory, syncSessionFactory,
-				transportPropertyManager);
-		this.ioExecutor = ioExecutor;
-		this.transportId = transportId;
-		reader = connection.getReader();
-		writer = connection.getWriter();
-		remote = connection.getRemoteProperties();
-	}
-
-	void onReadError(boolean recognised) {
-		disposeOnError(reader, recognised);
-		disposeOnError(writer);
-		interruptOutgoingSession();
-	}
-
-	void onWriteError() {
-		disposeOnError(reader, true);
-		disposeOnError(writer);
-	}
-
-	SyncSession createDuplexOutgoingSession(StreamContext ctx,
-			TransportConnectionWriter w, @Nullable Priority priority)
-			throws IOException {
-		StreamWriter streamWriter = streamWriterFactory.createStreamWriter(
-				w.getOutputStream(), ctx);
-		ContactId c = requireNonNull(ctx.getContactId());
-		return syncSessionFactory.createDuplexOutgoingSession(c,
-				ctx.getTransportId(), w.getMaxLatency(), w.getMaxIdleTime(),
-				streamWriter, priority);
-	}
-}

bramble-core/src/main/java/org/briarproject/bramble/connection/HandshakeConnection.java

@@ -1,72 +0,0 @@
-package org.briarproject.bramble.connection;
-
-import org.briarproject.bramble.api.connection.ConnectionManager;
-import org.briarproject.bramble.api.connection.ConnectionRegistry;
-import org.briarproject.bramble.api.contact.ContactExchangeManager;
-import org.briarproject.bramble.api.contact.HandshakeManager;
-import org.briarproject.bramble.api.contact.PendingContactId;
-import org.briarproject.bramble.api.db.DbException;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.plugin.TransportConnectionReader;
-import org.briarproject.bramble.api.plugin.TransportConnectionWriter;
-import org.briarproject.bramble.api.plugin.TransportId;
-import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
-import org.briarproject.bramble.api.transport.KeyManager;
-import org.briarproject.bramble.api.transport.StreamContext;
-import org.briarproject.bramble.api.transport.StreamReaderFactory;
-import org.briarproject.bramble.api.transport.StreamWriterFactory;
-
-import javax.annotation.Nullable;
-
-import static java.util.logging.Level.WARNING;
-import static org.briarproject.bramble.util.LogUtils.logException;
-
-@NotNullByDefault
-abstract class HandshakeConnection extends Connection {
-
-	final HandshakeManager handshakeManager;
-	final ContactExchangeManager contactExchangeManager;
-	final ConnectionManager connectionManager;
-	final PendingContactId pendingContactId;
-	final TransportId transportId;
-	final DuplexTransportConnection connection;
-	final TransportConnectionReader reader;
-	final TransportConnectionWriter writer;
-
-	HandshakeConnection(KeyManager keyManager,
-			ConnectionRegistry connectionRegistry,
-			StreamReaderFactory streamReaderFactory,
-			StreamWriterFactory streamWriterFactory,
-			HandshakeManager handshakeManager,
-			ContactExchangeManager contactExchangeManager,
-			ConnectionManager connectionManager,
-			PendingContactId pendingContactId,
-			TransportId transportId, DuplexTransportConnection connection) {
-		super(keyManager, connectionRegistry, streamReaderFactory,
-				streamWriterFactory);
-		this.handshakeManager = handshakeManager;
-		this.contactExchangeManager = contactExchangeManager;
-		this.connectionManager = connectionManager;
-		this.pendingContactId = pendingContactId;
-		this.transportId = transportId;
-		this.connection = connection;
-		reader = connection.getReader();
-		writer = connection.getWriter();
-	}
-
-	@Nullable
-	StreamContext allocateStreamContext(PendingContactId pendingContactId,
-			TransportId transportId) {
-		try {
-			return keyManager.getStreamContext(pendingContactId, transportId);
-		} catch (DbException e) {
-			logException(LOG, WARNING, e);
-			return null;
-		}
-	}
-
-	void onError(boolean recognised) {
-		disposeOnError(reader, recognised);
-		disposeOnError(writer);
-	}
-}

bramble-core/src/main/java/org/briarproject/bramble/connection/IncomingDuplexSyncConnection.java

@@ -1,107 +0,0 @@
-package org.briarproject.bramble.connection;
-
-import org.briarproject.bramble.api.connection.ConnectionRegistry;
-import org.briarproject.bramble.api.contact.ContactId;
-import org.briarproject.bramble.api.db.DbException;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.plugin.TransportId;
-import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
-import org.briarproject.bramble.api.properties.TransportPropertyManager;
-import org.briarproject.bramble.api.sync.PriorityHandler;
-import org.briarproject.bramble.api.sync.SyncSession;
-import org.briarproject.bramble.api.sync.SyncSessionFactory;
-import org.briarproject.bramble.api.transport.KeyManager;
-import org.briarproject.bramble.api.transport.StreamContext;
-import org.briarproject.bramble.api.transport.StreamReaderFactory;
-import org.briarproject.bramble.api.transport.StreamWriterFactory;
-
-import java.io.IOException;
-import java.util.concurrent.Executor;
-
-import static java.util.logging.Level.WARNING;
-import static org.briarproject.bramble.util.LogUtils.logException;
-
-@NotNullByDefault
-class IncomingDuplexSyncConnection extends DuplexSyncConnection
-		implements Runnable {
-
-	IncomingDuplexSyncConnection(KeyManager keyManager,
-			ConnectionRegistry connectionRegistry,
-			StreamReaderFactory streamReaderFactory,
-			StreamWriterFactory streamWriterFactory,
-			SyncSessionFactory syncSessionFactory,
-			TransportPropertyManager transportPropertyManager,
-			Executor ioExecutor, TransportId transportId,
-			DuplexTransportConnection connection) {
-		super(keyManager, connectionRegistry, streamReaderFactory,
-				streamWriterFactory, syncSessionFactory,
-				transportPropertyManager, ioExecutor, transportId, connection);
-	}
-
-	@Override
-	public void run() {
-		// Read and recognise the tag
-		StreamContext ctx = recogniseTag(reader, transportId);
-		if (ctx == null) {
-			LOG.info("Unrecognised tag");
-			onReadError(false);
-			return;
-		}
-		ContactId contactId = ctx.getContactId();
-		if (contactId == null) {
-			LOG.warning("Expected contact tag, got rendezvous tag");
-			onReadError(true);
-			return;
-		}
-		if (ctx.isHandshakeMode()) {
-			// TODO: Support handshake mode for contacts
-			LOG.warning("Received handshake tag, expected rotation mode");
-			onReadError(true);
-			return;
-		}
-		connectionRegistry.registerIncomingConnection(contactId, transportId,
-				this);
-		// Start the outgoing session on another thread
-		ioExecutor.execute(() -> runOutgoingSession(contactId));
-		try {
-			// Store any transport properties discovered from the connection
-			transportPropertyManager.addRemotePropertiesFromConnection(
-					contactId, transportId, remote);
-			// Update the connection registry when we receive our priority
-			PriorityHandler handler = p -> connectionRegistry.setPriority(
-					contactId, transportId, this, p);
-			// Create and run the incoming session
-			createIncomingSession(ctx, reader, handler).run();
-			reader.dispose(false, true);
-			interruptOutgoingSession();
-			connectionRegistry.unregisterConnection(contactId, transportId,
-					this, true, false);
-		} catch (DbException | IOException e) {
-			logException(LOG, WARNING, e);
-			onReadError(true);
-			connectionRegistry.unregisterConnection(contactId, transportId,
-					this, true, true);
-		}
-	}
-
-	private void runOutgoingSession(ContactId contactId) {
-		// Allocate a stream context
-		StreamContext ctx = allocateStreamContext(contactId, transportId);
-		if (ctx == null) {
-			LOG.warning("Could not allocate stream context");
-			onWriteError();
-			return;
-		}
-		try {
-			// Create and run the outgoing session
-			SyncSession out = createDuplexOutgoingSession(ctx, writer, null);
-			setOutgoingSession(out);
-			out.run();
-			writer.dispose(false);
-		} catch (IOException e) {
-			logException(LOG, WARNING, e);
-			onWriteError();
-		}
-	}
-}
-

bramble-core/src/main/java/org/briarproject/bramble/connection/IncomingHandshakeConnection.java

@@ -1,93 +0,0 @@
-package org.briarproject.bramble.connection;
-
-import org.briarproject.bramble.api.connection.ConnectionManager;
-import org.briarproject.bramble.api.connection.ConnectionRegistry;
-import org.briarproject.bramble.api.contact.ContactExchangeManager;
-import org.briarproject.bramble.api.contact.HandshakeManager;
-import org.briarproject.bramble.api.contact.HandshakeManager.HandshakeResult;
-import org.briarproject.bramble.api.contact.PendingContactId;
-import org.briarproject.bramble.api.db.DbException;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.plugin.TransportId;
-import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
-import org.briarproject.bramble.api.transport.KeyManager;
-import org.briarproject.bramble.api.transport.StreamContext;
-import org.briarproject.bramble.api.transport.StreamReaderFactory;
-import org.briarproject.bramble.api.transport.StreamWriter;
-import org.briarproject.bramble.api.transport.StreamWriterFactory;
-
-import java.io.IOException;
-import java.io.InputStream;
-
-import static java.util.logging.Level.WARNING;
-import static org.briarproject.bramble.util.LogUtils.logException;
-
-@NotNullByDefault
-class IncomingHandshakeConnection extends HandshakeConnection
-		implements Runnable {
-
-	IncomingHandshakeConnection(KeyManager keyManager,
-			ConnectionRegistry connectionRegistry,
-			StreamReaderFactory streamReaderFactory,
-			StreamWriterFactory streamWriterFactory,
-			HandshakeManager handshakeManager,
-			ContactExchangeManager contactExchangeManager,
-			ConnectionManager connectionManager,
-			PendingContactId pendingContactId,
-			TransportId transportId, DuplexTransportConnection connection) {
-		super(keyManager, connectionRegistry, streamReaderFactory,
-				streamWriterFactory, handshakeManager, contactExchangeManager,
-				connectionManager, pendingContactId, transportId, connection);
-	}
-
-	@Override
-	public void run() {
-		// Read and recognise the tag
-		StreamContext ctxIn = recogniseTag(reader, transportId);
-		if (ctxIn == null) {
-			LOG.info("Unrecognised tag");
-			onError(false);
-			return;
-		}
-		PendingContactId inPendingContactId = ctxIn.getPendingContactId();
-		if (inPendingContactId == null) {
-			LOG.warning("Expected rendezvous tag, got contact tag");
-			onError(true);
-			return;
-		}
-		// Allocate the outgoing stream context
-		StreamContext ctxOut =
-				allocateStreamContext(pendingContactId, transportId);
-		if (ctxOut == null) {
-			LOG.warning("Could not allocate stream context");
-			onError(true);
-			return;
-		}
-		// Close the connection if it's redundant
-		if (!connectionRegistry.registerConnection(pendingContactId)) {
-			LOG.info("Redundant rendezvous connection");
-			onError(true);
-			return;
-		}
-		// Handshake and exchange contacts
-		try {
-			InputStream in = streamReaderFactory.createStreamReader(
-					reader.getInputStream(), ctxIn);
-			// Flush the output stream to send the outgoing stream header
-			StreamWriter out = streamWriterFactory.createStreamWriter(
-					writer.getOutputStream(), ctxOut);
-			out.getOutputStream().flush();
-			HandshakeResult result =
-					handshakeManager.handshake(pendingContactId, in, out);
-			contactExchangeManager.exchangeContacts(pendingContactId,
-					connection, result.getMasterKey(), result.isAlice(), false);
-			connectionRegistry.unregisterConnection(pendingContactId, true);
-			// Reuse the connection as a transport connection
-			connectionManager.manageIncomingConnection(transportId, connection);
-		} catch (IOException | DbException e) {
-			logException(LOG, WARNING, e);
-			onError(true);
-			connectionRegistry.unregisterConnection(pendingContactId, false);
-		}
-	}
-}

bramble-core/src/main/java/org/briarproject/bramble/connection/IncomingSimplexSyncConnection.java

@@ -1,79 +0,0 @@
-package org.briarproject.bramble.connection;
-
-import org.briarproject.bramble.api.connection.ConnectionRegistry;
-import org.briarproject.bramble.api.contact.ContactId;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.plugin.TransportConnectionReader;
-import org.briarproject.bramble.api.plugin.TransportId;
-import org.briarproject.bramble.api.properties.TransportPropertyManager;
-import org.briarproject.bramble.api.sync.PriorityHandler;
-import org.briarproject.bramble.api.sync.SyncSessionFactory;
-import org.briarproject.bramble.api.transport.KeyManager;
-import org.briarproject.bramble.api.transport.StreamContext;
-import org.briarproject.bramble.api.transport.StreamReaderFactory;
-import org.briarproject.bramble.api.transport.StreamWriterFactory;
-
-import java.io.IOException;
-
-import static java.util.logging.Level.WARNING;
-import static org.briarproject.bramble.util.LogUtils.logException;
-
-@NotNullByDefault
-class IncomingSimplexSyncConnection extends SyncConnection implements Runnable {
-
-	private final TransportId transportId;
-	private final TransportConnectionReader reader;
-
-	IncomingSimplexSyncConnection(KeyManager keyManager,
-			ConnectionRegistry connectionRegistry,
-			StreamReaderFactory streamReaderFactory,
-			StreamWriterFactory streamWriterFactory,
-			SyncSessionFactory syncSessionFactory,
-			TransportPropertyManager transportPropertyManager,
-			TransportId transportId, TransportConnectionReader reader) {
-		super(keyManager, connectionRegistry, streamReaderFactory,
-				streamWriterFactory, syncSessionFactory,
-				transportPropertyManager);
-		this.transportId = transportId;
-		this.reader = reader;
-	}
-
-	@Override
-	public void run() {
-		// Read and recognise the tag
-		StreamContext ctx = recogniseTag(reader, transportId);
-		if (ctx == null) {
-			LOG.info("Unrecognised tag");
-			onError(false);
-			return;
-		}
-		ContactId contactId = ctx.getContactId();
-		if (contactId == null) {
-			LOG.warning("Received rendezvous stream, expected contact");
-			onError(true);
-			return;
-		}
-		if (ctx.isHandshakeMode()) {
-			// TODO: Support handshake mode for contacts
-			LOG.warning("Received handshake tag, expected rotation mode");
-			onError(true);
-			return;
-		}
-		try {
-			// We don't expect to receive a priority for this connection
-			PriorityHandler handler = p ->
-					LOG.info("Ignoring priority for simplex connection");
-			// Create and run the incoming session
-			createIncomingSession(ctx, reader, handler).run();
-			reader.dispose(false, true);
-		} catch (IOException e) {
-			logException(LOG, WARNING, e);
-			onError(true);
-		}
-	}
-
-	private void onError(boolean recognised) {
-		disposeOnError(reader, recognised);
-	}
-}
-

bramble-core/src/main/java/org/briarproject/bramble/connection/OutgoingDuplexSyncConnection.java

@@ -1,140 +0,0 @@
-package org.briarproject.bramble.connection;
-
-import org.briarproject.bramble.api.connection.ConnectionRegistry;
-import org.briarproject.bramble.api.contact.ContactId;
-import org.briarproject.bramble.api.db.DbException;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.plugin.TransportId;
-import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
-import org.briarproject.bramble.api.properties.TransportPropertyManager;
-import org.briarproject.bramble.api.sync.Priority;
-import org.briarproject.bramble.api.sync.PriorityHandler;
-import org.briarproject.bramble.api.sync.SyncSession;
-import org.briarproject.bramble.api.sync.SyncSessionFactory;
-import org.briarproject.bramble.api.transport.KeyManager;
-import org.briarproject.bramble.api.transport.StreamContext;
-import org.briarproject.bramble.api.transport.StreamReaderFactory;
-import org.briarproject.bramble.api.transport.StreamWriterFactory;
-
-import java.io.IOException;
-import java.security.SecureRandom;
-import java.util.concurrent.Executor;
-
-import static java.util.logging.Level.WARNING;
-import static org.briarproject.bramble.api.sync.SyncConstants.PRIORITY_NONCE_BYTES;
-import static org.briarproject.bramble.util.LogUtils.logException;
-
-@NotNullByDefault
-class OutgoingDuplexSyncConnection extends DuplexSyncConnection
-		implements Runnable {
-
-	private final SecureRandom secureRandom;
-	private final ContactId contactId;
-
-	OutgoingDuplexSyncConnection(KeyManager keyManager,
-			ConnectionRegistry connectionRegistry,
-			StreamReaderFactory streamReaderFactory,
-			StreamWriterFactory streamWriterFactory,
-			SyncSessionFactory syncSessionFactory,
-			TransportPropertyManager transportPropertyManager,
-			Executor ioExecutor, SecureRandom secureRandom, ContactId contactId,
-			TransportId transportId, DuplexTransportConnection connection) {
-		super(keyManager, connectionRegistry, streamReaderFactory,
-				streamWriterFactory, syncSessionFactory,
-				transportPropertyManager, ioExecutor, transportId, connection);
-		this.secureRandom = secureRandom;
-		this.contactId = contactId;
-	}
-
-	@Override
-	public void run() {
-		// Allocate a stream context
-		StreamContext ctx = allocateStreamContext(contactId, transportId);
-		if (ctx == null) {
-			LOG.warning("Could not allocate stream context");
-			onWriteError();
-			return;
-		}
-		if (ctx.isHandshakeMode()) {
-			// TODO: Support handshake mode for contacts
-			LOG.warning("Cannot use handshake mode stream context");
-			onWriteError();
-			return;
-		}
-		// Start the incoming session on another thread
-		Priority priority = generatePriority();
-		ioExecutor.execute(() -> runIncomingSession(priority));
-		try {
-			// Create and run the outgoing session
-			SyncSession out =
-					createDuplexOutgoingSession(ctx, writer, priority);
-			setOutgoingSession(out);
-			out.run();
-			writer.dispose(false);
-		} catch (IOException e) {
-			logException(LOG, WARNING, e);
-			onWriteError();
-		}
-	}
-
-	private void runIncomingSession(Priority priority) {
-		// Read and recognise the tag
-		StreamContext ctx = recogniseTag(reader, transportId);
-		// Unrecognised tags are suspicious in this case
-		if (ctx == null) {
-			LOG.warning("Unrecognised tag for returning stream");
-			onReadError();
-			return;
-		}
-		// Check that the stream comes from the expected contact
-		ContactId inContactId = ctx.getContactId();
-		if (inContactId == null) {
-			LOG.warning("Expected contact tag, got rendezvous tag");
-			onReadError();
-			return;
-		}
-		if (!contactId.equals(inContactId)) {
-			LOG.warning("Wrong contact ID for returning stream");
-			onReadError();
-			return;
-		}
-		if (ctx.isHandshakeMode()) {
-			// TODO: Support handshake mode for contacts
-			LOG.warning("Received handshake tag, expected rotation mode");
-			onReadError();
-			return;
-		}
-		connectionRegistry.registerOutgoingConnection(contactId, transportId,
-				this, priority);
-		try {
-			// Store any transport properties discovered from the connection
-			transportPropertyManager.addRemotePropertiesFromConnection(
-					contactId, transportId, remote);
-			// We don't expect to receive a priority for this connection
-			PriorityHandler handler = p ->
-					LOG.info("Ignoring priority for outgoing connection");
-			// Create and run the incoming session
-			createIncomingSession(ctx, reader, handler).run();
-			reader.dispose(false, true);
-			interruptOutgoingSession();
-			connectionRegistry.unregisterConnection(contactId, transportId,
-					this, false, false);
-		} catch (DbException | IOException e) {
-			logException(LOG, WARNING, e);
-			onReadError();
-			connectionRegistry.unregisterConnection(contactId, transportId,
-					this, false, true);
-		}
-	}
-
-	private void onReadError() {
-		// 'Recognised' is always true for outgoing connections
-		onReadError(true);
-	}
-
-	private Priority generatePriority() {
-		byte[] nonce = new byte[PRIORITY_NONCE_BYTES];
-		secureRandom.nextBytes(nonce);
-		return new Priority(nonce);
-	}
-}

bramble-core/src/main/java/org/briarproject/bramble/connection/OutgoingHandshakeConnection.java

@@ -1,115 +0,0 @@
-package org.briarproject.bramble.connection;
-
-import org.briarproject.bramble.api.connection.ConnectionManager;
-import org.briarproject.bramble.api.connection.ConnectionRegistry;
-import org.briarproject.bramble.api.contact.Contact;
-import org.briarproject.bramble.api.contact.ContactExchangeManager;
-import org.briarproject.bramble.api.contact.HandshakeManager;
-import org.briarproject.bramble.api.contact.HandshakeManager.HandshakeResult;
-import org.briarproject.bramble.api.contact.PendingContactId;
-import org.briarproject.bramble.api.db.DbException;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.plugin.TransportId;
-import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
-import org.briarproject.bramble.api.transport.KeyManager;
-import org.briarproject.bramble.api.transport.StreamContext;
-import org.briarproject.bramble.api.transport.StreamReaderFactory;
-import org.briarproject.bramble.api.transport.StreamWriter;
-import org.briarproject.bramble.api.transport.StreamWriterFactory;
-
-import java.io.IOException;
-import java.io.InputStream;
-
-import static java.util.logging.Level.WARNING;
-import static org.briarproject.bramble.util.LogUtils.logException;
-
-@NotNullByDefault
-class OutgoingHandshakeConnection extends HandshakeConnection
-		implements Runnable {
-
-	OutgoingHandshakeConnection(KeyManager keyManager,
-			ConnectionRegistry connectionRegistry,
-			StreamReaderFactory streamReaderFactory,
-			StreamWriterFactory streamWriterFactory,
-			HandshakeManager handshakeManager,
-			ContactExchangeManager contactExchangeManager,
-			ConnectionManager connectionManager,
-			PendingContactId pendingContactId,
-			TransportId transportId, DuplexTransportConnection connection) {
-		super(keyManager, connectionRegistry, streamReaderFactory,
-				streamWriterFactory, handshakeManager, contactExchangeManager,
-				connectionManager, pendingContactId, transportId, connection);
-	}
-
-	@Override
-	public void run() {
-		// Allocate the outgoing stream context
-		StreamContext ctxOut =
-				allocateStreamContext(pendingContactId, transportId);
-		if (ctxOut == null) {
-			LOG.warning("Could not allocate stream context");
-			onError();
-			return;
-		}
-		// Flush the output stream to send the outgoing stream header
-		StreamWriter out;
-		try {
-			out = streamWriterFactory.createStreamWriter(
-					writer.getOutputStream(), ctxOut);
-			out.getOutputStream().flush();
-		} catch (IOException e) {
-			logException(LOG, WARNING, e);
-			onError();
-			return;
-		}
-		// Read and recognise the tag
-		StreamContext ctxIn = recogniseTag(reader, transportId);
-		// Unrecognised tags are suspicious in this case
-		if (ctxIn == null) {
-			LOG.warning("Unrecognised tag for returning stream");
-			onError();
-			return;
-		}
-		// Check that the stream comes from the expected pending contact
-		PendingContactId inPendingContactId = ctxIn.getPendingContactId();
-		if (inPendingContactId == null) {
-			LOG.warning("Expected rendezvous tag, got contact tag");
-			onError();
-			return;
-		}
-		if (!inPendingContactId.equals(pendingContactId)) {
-			LOG.warning("Wrong pending contact ID for returning stream");
-			onError();
-			return;
-		}
-		// Close the connection if it's redundant
-		if (!connectionRegistry.registerConnection(pendingContactId)) {
-			LOG.info("Redundant rendezvous connection");
-			onError();
-			return;
-		}
-		// Handshake and exchange contacts
-		try {
-			InputStream in = streamReaderFactory.createStreamReader(
-					reader.getInputStream(), ctxIn);
-			HandshakeResult result =
-					handshakeManager.handshake(pendingContactId, in, out);
-			Contact contact = contactExchangeManager.exchangeContacts(
-					pendingContactId, connection, result.getMasterKey(),
-					result.isAlice(), false);
-			connectionRegistry.unregisterConnection(pendingContactId, true);
-			// Reuse the connection as a transport connection
-			connectionManager.manageOutgoingConnection(contact.getId(),
-					transportId, connection);
-		} catch (IOException | DbException e) {
-			logException(LOG, WARNING, e);
-			onError();
-			connectionRegistry.unregisterConnection(pendingContactId, false);
-		}
-	}
-
-	private void onError() {
-		// 'Recognised' is always true for outgoing connections
-		onError(true);
-	}
-}

bramble-core/src/main/java/org/briarproject/bramble/connection/OutgoingSimplexSyncConnection.java

@@ -1,78 +0,0 @@
-package org.briarproject.bramble.connection;
-
-import org.briarproject.bramble.api.connection.ConnectionRegistry;
-import org.briarproject.bramble.api.contact.ContactId;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.plugin.TransportConnectionWriter;
-import org.briarproject.bramble.api.plugin.TransportId;
-import org.briarproject.bramble.api.properties.TransportPropertyManager;
-import org.briarproject.bramble.api.sync.SyncSession;
-import org.briarproject.bramble.api.sync.SyncSessionFactory;
-import org.briarproject.bramble.api.transport.KeyManager;
-import org.briarproject.bramble.api.transport.StreamContext;
-import org.briarproject.bramble.api.transport.StreamReaderFactory;
-import org.briarproject.bramble.api.transport.StreamWriter;
-import org.briarproject.bramble.api.transport.StreamWriterFactory;
-
-import java.io.IOException;
-
-import static java.util.logging.Level.WARNING;
-import static org.briarproject.bramble.api.nullsafety.NullSafety.requireNonNull;
-import static org.briarproject.bramble.util.LogUtils.logException;
-
-@NotNullByDefault
-class OutgoingSimplexSyncConnection extends SyncConnection implements Runnable {
-
-	private final ContactId contactId;
-	private final TransportId transportId;
-	private final TransportConnectionWriter writer;
-
-	OutgoingSimplexSyncConnection(KeyManager keyManager,
-			ConnectionRegistry connectionRegistry,
-			StreamReaderFactory streamReaderFactory,
-			StreamWriterFactory streamWriterFactory,
-			SyncSessionFactory syncSessionFactory,
-			TransportPropertyManager transportPropertyManager,
-			ContactId contactId, TransportId transportId,
-			TransportConnectionWriter writer) {
-		super(keyManager, connectionRegistry, streamReaderFactory,
-				streamWriterFactory, syncSessionFactory,
-				transportPropertyManager);
-		this.contactId = contactId;
-		this.transportId = transportId;
-		this.writer = writer;
-	}
-
-	@Override
-	public void run() {
-		// Allocate a stream context
-		StreamContext ctx = allocateStreamContext(contactId, transportId);
-		if (ctx == null) {
-			LOG.warning("Could not allocate stream context");
-			onError();
-			return;
-		}
-		try {
-			// Create and run the outgoing session
-			createSimplexOutgoingSession(ctx, writer).run();
-			writer.dispose(false);
-		} catch (IOException e) {
-			logException(LOG, WARNING, e);
-			onError();
-		}
-	}
-
-	private void onError() {
-		disposeOnError(writer);
-	}
-
-	private SyncSession createSimplexOutgoingSession(StreamContext ctx,
-			TransportConnectionWriter w) throws IOException {
-		StreamWriter streamWriter = streamWriterFactory.createStreamWriter(
-				w.getOutputStream(), ctx);
-		ContactId c = requireNonNull(ctx.getContactId());
-		return syncSessionFactory.createSimplexOutgoingSession(c,
-				ctx.getTransportId(), w.getMaxLatency(), streamWriter);
-	}
-}
-

bramble-core/src/main/java/org/briarproject/bramble/connection/SyncConnection.java

@@ -1,64 +0,0 @@
-package org.briarproject.bramble.connection;
-
-import org.briarproject.bramble.api.connection.ConnectionRegistry;
-import org.briarproject.bramble.api.contact.ContactId;
-import org.briarproject.bramble.api.db.DbException;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.plugin.TransportConnectionReader;
-import org.briarproject.bramble.api.plugin.TransportId;
-import org.briarproject.bramble.api.properties.TransportPropertyManager;
-import org.briarproject.bramble.api.sync.PriorityHandler;
-import org.briarproject.bramble.api.sync.SyncSession;
-import org.briarproject.bramble.api.sync.SyncSessionFactory;
-import org.briarproject.bramble.api.transport.KeyManager;
-import org.briarproject.bramble.api.transport.StreamContext;
-import org.briarproject.bramble.api.transport.StreamReaderFactory;
-import org.briarproject.bramble.api.transport.StreamWriterFactory;
-
-import java.io.IOException;
-import java.io.InputStream;
-
-import javax.annotation.Nullable;
-
-import static java.util.logging.Level.WARNING;
-import static org.briarproject.bramble.api.nullsafety.NullSafety.requireNonNull;
-import static org.briarproject.bramble.util.LogUtils.logException;
-
-@NotNullByDefault
-class SyncConnection extends Connection {
-
-	final SyncSessionFactory syncSessionFactory;
-	final TransportPropertyManager transportPropertyManager;
-
-	SyncConnection(KeyManager keyManager, ConnectionRegistry connectionRegistry,
-			StreamReaderFactory streamReaderFactory,
-			StreamWriterFactory streamWriterFactory,
-			SyncSessionFactory syncSessionFactory,
-			TransportPropertyManager transportPropertyManager) {
-		super(keyManager, connectionRegistry, streamReaderFactory,
-				streamWriterFactory);
-		this.syncSessionFactory = syncSessionFactory;
-		this.transportPropertyManager = transportPropertyManager;
-	}
-
-	@Nullable
-	StreamContext allocateStreamContext(ContactId contactId,
-			TransportId transportId) {
-		try {
-			return keyManager.getStreamContext(contactId, transportId);
-		} catch (DbException e) {
-			logException(LOG, WARNING, e);
-			return null;
-		}
-	}
-
-	SyncSession createIncomingSession(StreamContext ctx,
-			TransportConnectionReader r, PriorityHandler handler)
-			throws IOException {
-		InputStream streamReader = streamReaderFactory.createStreamReader(
-				r.getInputStream(), ctx);
-		ContactId c = requireNonNull(ctx.getContactId());
-		return syncSessionFactory
-				.createIncomingSession(c, streamReader, handler);
-	}
-}

bramble-core/src/main/java/org/briarproject/bramble/crypto/CryptoComponentImpl.java

@@ -7,7 +7,6 @@ import net.i2p.crypto.eddsa.KeyPairGenerator;
 import org.briarproject.bramble.api.crypto.AgreementPrivateKey;
 import org.briarproject.bramble.api.crypto.AgreementPublicKey;
 import org.briarproject.bramble.api.crypto.CryptoComponent;
-import org.briarproject.bramble.api.crypto.DecryptionException;
 import org.briarproject.bramble.api.crypto.KeyPair;
 import org.briarproject.bramble.api.crypto.KeyParser;
 import org.briarproject.bramble.api.crypto.KeyStrengthener;
@@ -40,9 +39,6 @@ import static java.lang.System.arraycopy;
 import static java.util.logging.Level.INFO;
 import static org.briarproject.bramble.api.crypto.CryptoConstants.KEY_TYPE_AGREEMENT;
 import static org.briarproject.bramble.api.crypto.CryptoConstants.KEY_TYPE_SIGNATURE;
-import static org.briarproject.bramble.api.crypto.DecryptionResult.INVALID_CIPHERTEXT;
-import static org.briarproject.bramble.api.crypto.DecryptionResult.INVALID_PASSWORD;
-import static org.briarproject.bramble.api.crypto.DecryptionResult.KEY_STRENGTHENER_ERROR;
 import static org.briarproject.bramble.util.ByteUtils.INT_32_BYTES;
 import static org.briarproject.bramble.util.LogUtils.logDuration;
 import static org.briarproject.bramble.util.LogUtils.now;
@@ -363,17 +359,16 @@ class CryptoComponentImpl implements CryptoComponent {
 	}
 
 	@Override
+	@Nullable
 	public byte[] decryptWithPassword(byte[] input, String password,
-			@Nullable KeyStrengthener keyStrengthener)
+			@Nullable KeyStrengthener keyStrengthener) {
-			throws DecryptionException {
 		AuthenticatedCipher cipher = new XSalsa20Poly1305AuthenticatedCipher();
 		int macBytes = cipher.getMacBytes();
 		// The input contains the format version, salt, cost parameter, IV,
 		// ciphertext and MAC
 		if (input.length < 1 + PBKDF_SALT_BYTES + INT_32_BYTES
-				+ STORAGE_IV_BYTES + macBytes) {
+				+ STORAGE_IV_BYTES + macBytes)
-			throw new DecryptionException(INVALID_CIPHERTEXT);
+			return null; // Invalid input
-		}
 		int inputOff = 0;
 		// Format version
 		byte formatVersion = input[inputOff];
@@ -381,7 +376,7 @@ class CryptoComponentImpl implements CryptoComponent {
 		// Check whether we support this format version
 		if (formatVersion != PBKDF_FORMAT_SCRYPT &&
 				formatVersion != PBKDF_FORMAT_SCRYPT_STRENGTHENED) {
-			throw new DecryptionException(INVALID_CIPHERTEXT);
+			return null;
 		}
 		// Salt
 		byte[] salt = new byte[PBKDF_SALT_BYTES];
@@ -390,9 +385,8 @@ class CryptoComponentImpl implements CryptoComponent {
 		// Cost parameter
 		long cost = ByteUtils.readUint32(input, inputOff);
 		inputOff += INT_32_BYTES;
-		if (cost < 2 || cost > Integer.MAX_VALUE) {
+		if (cost < 2 || cost > Integer.MAX_VALUE)
-			throw new DecryptionException(INVALID_CIPHERTEXT);
+			return null; // Invalid cost parameter
-		}
 		// IV
 		byte[] iv = new byte[STORAGE_IV_BYTES];
 		arraycopy(input, inputOff, iv, 0, iv.length);
@@ -400,10 +394,8 @@ class CryptoComponentImpl implements CryptoComponent {
 		// Derive the decryption key from the password
 		SecretKey key = passwordBasedKdf.deriveKey(password, salt, (int) cost);
 		if (formatVersion == PBKDF_FORMAT_SCRYPT_STRENGTHENED) {
-			if (keyStrengthener == null || !keyStrengthener.isInitialised()) {
+			if (keyStrengthener == null || !keyStrengthener.isInitialised())
-				// Can't derive the same strengthened key
+				return null; // Can't derive the same strengthened key
-				throw new DecryptionException(KEY_STRENGTHENER_ERROR);
-			}
 			key = keyStrengthener.strengthenKey(key);
 		}
 		// Initialise the cipher
@@ -419,7 +411,7 @@ class CryptoComponentImpl implements CryptoComponent {
 			cipher.process(input, inputOff, inputLen, output, 0);
 			return output;
 		} catch (GeneralSecurityException e) {
-			throw new DecryptionException(INVALID_PASSWORD);
+			return null; // Invalid ciphertext
 		}
 	}
 

bramble-core/src/main/java/org/briarproject/bramble/db/H2Database.java

@@ -25,7 +25,6 @@ import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.db.JdbcUtils.tryToClose;
-import static org.briarproject.bramble.util.IoUtils.isNonEmptyDirectory;
 import static org.briarproject.bramble.util.LogUtils.logFileOrDir;
 
 /**
@@ -70,9 +69,8 @@ class H2Database extends JdbcDatabase {
 			LOG.info("Contents of account directory before opening DB:");
 			logFileOrDir(LOG, INFO, dir.getParentFile());
 		}
-		boolean reopen = isNonEmptyDirectory(dir);
+		boolean reopen = !dir.mkdirs();
 		if (LOG.isLoggable(INFO)) LOG.info("Reopening DB: " + reopen);
-		if (!reopen && dir.mkdirs()) LOG.info("Created database directory");
 		super.open("org.h2.Driver", reopen, key, listener);
 		if (LOG.isLoggable(INFO)) {
 			LOG.info("Contents of account directory after opening DB:");

bramble-core/src/main/java/org/briarproject/bramble/db/HyperSqlDatabase.java

@@ -20,11 +20,9 @@ import java.util.logging.Logger;
 import javax.annotation.Nullable;
 import javax.inject.Inject;
 
-import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.db.JdbcUtils.tryToClose;
-import static org.briarproject.bramble.util.IoUtils.isNonEmptyDirectory;
 
 /**
  * Contains all the HSQLDB-specific code for the database.
@@ -66,10 +64,7 @@ class HyperSqlDatabase extends JdbcDatabase {
 	public boolean open(SecretKey key, @Nullable MigrationListener listener)
 			throws DbException {
 		this.key = key;
-		File dir = config.getDatabaseDirectory();
+		boolean reopen = !config.getDatabaseDirectory().mkdirs();
-		boolean reopen = isNonEmptyDirectory(dir);
-		if (LOG.isLoggable(INFO)) LOG.info("Reopening DB: " + reopen);
-		if (!reopen && dir.mkdirs()) LOG.info("Created database directory");
 		super.open("org.hsqldb.jdbc.JDBCDriver", reopen, key, listener);
 		return reopen;
 	}

bramble-core/src/main/java/org/briarproject/bramble/io/IoModule.java

@@ -1,18 +0,0 @@
-package org.briarproject.bramble.io;
-
-import org.briarproject.bramble.api.io.TimeoutMonitor;
-
-import javax.inject.Singleton;
-
-import dagger.Module;
-import dagger.Provides;
-
-@Module
-public class IoModule {
-
-	@Provides
-	@Singleton
-	TimeoutMonitor provideTimeoutMonitor(TimeoutMonitorImpl timeoutMonitor) {
-		return timeoutMonitor;
-	}
-}

bramble-core/src/main/java/org/briarproject/bramble/io/TimeoutInputStream.java

@@ -1,104 +0,0 @@
-package org.briarproject.bramble.io;
-
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.system.Clock;
-
-import java.io.IOException;
-import java.io.InputStream;
-
-import javax.annotation.concurrent.GuardedBy;
-
-@NotNullByDefault
-class TimeoutInputStream extends InputStream {
-
-	private final Clock clock;
-	private final InputStream in;
-	private final long timeoutMs;
-	private final CloseListener listener;
-	private final Object lock = new Object();
-	@GuardedBy("lock")
-	private long readStartedMs = -1;
-
-	TimeoutInputStream(Clock clock, InputStream in, long timeoutMs,
-			CloseListener listener) {
-		this.clock = clock;
-		this.in = in;
-		this.timeoutMs = timeoutMs;
-		this.listener = listener;
-	}
-
-	@Override
-	public int read() throws IOException {
-		synchronized (lock) {
-			readStartedMs = clock.currentTimeMillis();
-		}
-		int input = in.read();
-		synchronized (lock) {
-			readStartedMs = -1;
-		}
-		return input;
-	}
-
-	@Override
-	public int read(byte[] b) throws IOException {
-		return read(b, 0, b.length);
-	}
-
-	@Override
-	public int read(byte[] b, int off, int len) throws IOException {
-		synchronized (lock) {
-			readStartedMs = clock.currentTimeMillis();
-		}
-		int read = in.read(b, off, len);
-		synchronized (lock) {
-			readStartedMs = -1;
-		}
-		return read;
-	}
-
-	@Override
-	public void close() throws IOException {
-		try {
-			in.close();
-		} finally {
-			listener.onClose(this);
-		}
-	}
-
-	@Override
-	public int available() throws IOException {
-		return in.available();
-	}
-
-	@Override
-	public void mark(int readlimit) {
-		in.mark(readlimit);
-	}
-
-	@Override
-	public boolean markSupported() {
-		return in.markSupported();
-	}
-
-	@Override
-	public void reset() throws IOException {
-		in.reset();
-	}
-
-	@Override
-	public long skip(long n) throws IOException {
-		return in.skip(n);
-	}
-
-	boolean hasTimedOut() {
-		synchronized (lock) {
-			return readStartedMs != -1 &&
-					clock.currentTimeMillis() - readStartedMs > timeoutMs;
-		}
-	}
-
-	interface CloseListener {
-
-		void onClose(TimeoutInputStream closed);
-	}
-}

bramble-core/src/main/java/org/briarproject/bramble/io/TimeoutMonitorImpl.java

@@ -1,96 +0,0 @@
-package org.briarproject.bramble.io;
-
-import org.briarproject.bramble.api.io.TimeoutMonitor;
-import org.briarproject.bramble.api.lifecycle.IoExecutor;
-import org.briarproject.bramble.api.system.Clock;
-import org.briarproject.bramble.api.system.Scheduler;
-
-import java.io.IOException;
-import java.io.InputStream;
-import java.util.ArrayList;
-import java.util.List;
-import java.util.concurrent.Executor;
-import java.util.concurrent.Future;
-import java.util.concurrent.ScheduledExecutorService;
-import java.util.logging.Logger;
-
-import javax.annotation.concurrent.GuardedBy;
-import javax.inject.Inject;
-
-import static java.util.concurrent.TimeUnit.MILLISECONDS;
-import static java.util.concurrent.TimeUnit.SECONDS;
-import static java.util.logging.Level.INFO;
-import static java.util.logging.Logger.getLogger;
-import static org.briarproject.bramble.util.LogUtils.logException;
-
-class TimeoutMonitorImpl implements TimeoutMonitor {
-
-	private static final Logger LOG =
-			getLogger(TimeoutMonitorImpl.class.getName());
-
-	private static final long CHECK_INTERVAL_MS = SECONDS.toMillis(10);
-
-	private final ScheduledExecutorService scheduler;
-	private final Executor ioExecutor;
-	private final Clock clock;
-	private final Object lock = new Object();
-	@GuardedBy("lock")
-	private final List<TimeoutInputStream> streams = new ArrayList<>();
-
-	@GuardedBy("lock")
-	private Future<?> task = null;
-
-	@Inject
-	TimeoutMonitorImpl(@Scheduler ScheduledExecutorService scheduler,
-			@IoExecutor Executor ioExecutor, Clock clock) {
-		this.scheduler = scheduler;
-		this.ioExecutor = ioExecutor;
-		this.clock = clock;
-	}
-
-	@Override
-	public InputStream createTimeoutInputStream(InputStream in,
-			long timeoutMs) {
-		TimeoutInputStream stream = new TimeoutInputStream(clock, in,
-				timeoutMs, this::removeStream);
-		synchronized (lock) {
-			if (streams.isEmpty()) {
-				task = scheduler.scheduleWithFixedDelay(this::checkTimeouts,
-						CHECK_INTERVAL_MS, CHECK_INTERVAL_MS, MILLISECONDS);
-			}
-			streams.add(stream);
-		}
-		return stream;
-	}
-
-	private void removeStream(TimeoutInputStream stream) {
-		Future<?> toCancel = null;
-		synchronized (lock) {
-			if (streams.remove(stream) && streams.isEmpty()) {
-				toCancel = task;
-				task = null;
-			}
-		}
-		if (toCancel != null) toCancel.cancel(false);
-	}
-
-	@Scheduler
-	private void checkTimeouts() {
-		ioExecutor.execute(() -> {
-			List<TimeoutInputStream> snapshot;
-			synchronized (lock) {
-				snapshot = new ArrayList<>(streams);
-			}
-			for (TimeoutInputStream stream : snapshot) {
-				if (stream.hasTimedOut()) {
-					LOG.info("Input stream has timed out");
-					try {
-						stream.close();
-					} catch (IOException e) {
-						logException(LOG, INFO, e);
-					}
-				}
-			}
-		});
-	}
-}

bramble-core/src/main/java/org/briarproject/bramble/plugin/BackoffFactoryImpl.java

@@ -0,0 +1,18 @@
+package org.briarproject.bramble.plugin;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.Backoff;
+import org.briarproject.bramble.api.plugin.BackoffFactory;
+
+import javax.annotation.concurrent.Immutable;
+
+@Immutable
+@NotNullByDefault
+class BackoffFactoryImpl implements BackoffFactory {
+
+	@Override
+	public Backoff createBackoff(int minInterval, int maxInterval,
+			double base) {
+		return new BackoffImpl(minInterval, maxInterval, base);
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/plugin/BackoffImpl.java

@@ -0,0 +1,42 @@
+package org.briarproject.bramble.plugin;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.Backoff;
+
+import java.util.concurrent.atomic.AtomicInteger;
+
+import javax.annotation.concurrent.ThreadSafe;
+
+@ThreadSafe
+@NotNullByDefault
+class BackoffImpl implements Backoff {
+
+	private final int minInterval, maxInterval;
+	private final double base;
+	private final AtomicInteger backoff;
+
+	BackoffImpl(int minInterval, int maxInterval, double base) {
+		this.minInterval = minInterval;
+		this.maxInterval = maxInterval;
+		this.base = base;
+		backoff = new AtomicInteger(0);
+	}
+
+	@Override
+	public int getPollingInterval() {
+		double multiplier = Math.pow(base, backoff.get());
+		// Large or infinite values will be rounded to Integer.MAX_VALUE
+		int interval = (int) (minInterval * multiplier);
+		return Math.min(interval, maxInterval);
+	}
+
+	@Override
+	public void increment() {
+		backoff.incrementAndGet();
+	}
+
+	@Override
+	public void reset() {
+		backoff.set(0);
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/plugin/ConnectionManagerImpl.java

@@ -0,0 +1,694 @@
+package org.briarproject.bramble.plugin;
+
+import org.briarproject.bramble.api.contact.Contact;
+import org.briarproject.bramble.api.contact.ContactExchangeManager;
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.contact.HandshakeManager;
+import org.briarproject.bramble.api.contact.HandshakeManager.HandshakeResult;
+import org.briarproject.bramble.api.contact.PendingContactId;
+import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.bramble.api.lifecycle.IoExecutor;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.ConnectionManager;
+import org.briarproject.bramble.api.plugin.ConnectionRegistry;
+import org.briarproject.bramble.api.plugin.TransportConnectionReader;
+import org.briarproject.bramble.api.plugin.TransportConnectionWriter;
+import org.briarproject.bramble.api.plugin.TransportId;
+import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
+import org.briarproject.bramble.api.sync.SyncSession;
+import org.briarproject.bramble.api.sync.SyncSessionFactory;
+import org.briarproject.bramble.api.transport.KeyManager;
+import org.briarproject.bramble.api.transport.StreamContext;
+import org.briarproject.bramble.api.transport.StreamReaderFactory;
+import org.briarproject.bramble.api.transport.StreamWriter;
+import org.briarproject.bramble.api.transport.StreamWriterFactory;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.concurrent.Executor;
+import java.util.logging.Logger;
+
+import javax.annotation.Nullable;
+import javax.inject.Inject;
+
+import static java.util.logging.Level.WARNING;
+import static java.util.logging.Logger.getLogger;
+import static org.briarproject.bramble.api.nullsafety.NullSafety.requireNonNull;
+import static org.briarproject.bramble.api.transport.TransportConstants.TAG_LENGTH;
+import static org.briarproject.bramble.util.IoUtils.read;
+import static org.briarproject.bramble.util.LogUtils.logException;
+
+@NotNullByDefault
+class ConnectionManagerImpl implements ConnectionManager {
+
+	private static final Logger LOG =
+			getLogger(ConnectionManagerImpl.class.getName());
+
+	private final Executor ioExecutor;
+	private final KeyManager keyManager;
+	private final StreamReaderFactory streamReaderFactory;
+	private final StreamWriterFactory streamWriterFactory;
+	private final SyncSessionFactory syncSessionFactory;
+	private final HandshakeManager handshakeManager;
+	private final ContactExchangeManager contactExchangeManager;
+	private final ConnectionRegistry connectionRegistry;
+
+	@Inject
+	ConnectionManagerImpl(@IoExecutor Executor ioExecutor,
+			KeyManager keyManager, StreamReaderFactory streamReaderFactory,
+			StreamWriterFactory streamWriterFactory,
+			SyncSessionFactory syncSessionFactory,
+			HandshakeManager handshakeManager,
+			ContactExchangeManager contactExchangeManager,
+			ConnectionRegistry connectionRegistry) {
+		this.ioExecutor = ioExecutor;
+		this.keyManager = keyManager;
+		this.streamReaderFactory = streamReaderFactory;
+		this.streamWriterFactory = streamWriterFactory;
+		this.syncSessionFactory = syncSessionFactory;
+		this.handshakeManager = handshakeManager;
+		this.contactExchangeManager = contactExchangeManager;
+		this.connectionRegistry = connectionRegistry;
+	}
+
+	@Override
+	public void manageIncomingConnection(TransportId t,
+			TransportConnectionReader r) {
+		ioExecutor.execute(new ManageIncomingSimplexConnection(t, r));
+	}
+
+	@Override
+	public void manageIncomingConnection(TransportId t,
+			DuplexTransportConnection d) {
+		ioExecutor.execute(new ManageIncomingDuplexConnection(t, d));
+	}
+
+	@Override
+	public void manageIncomingConnection(PendingContactId p, TransportId t,
+			DuplexTransportConnection d) {
+		ioExecutor.execute(new ManageIncomingHandshakeConnection(p, t, d));
+	}
+
+	@Override
+	public void manageOutgoingConnection(ContactId c, TransportId t,
+			TransportConnectionWriter w) {
+		ioExecutor.execute(new ManageOutgoingSimplexConnection(c, t, w));
+	}
+
+	@Override
+	public void manageOutgoingConnection(ContactId c, TransportId t,
+			DuplexTransportConnection d) {
+		ioExecutor.execute(new ManageOutgoingDuplexConnection(c, t, d));
+	}
+
+	@Override
+	public void manageOutgoingConnection(PendingContactId p, TransportId t,
+			DuplexTransportConnection d) {
+		ioExecutor.execute(new ManageOutgoingHandshakeConnection(p, t, d));
+	}
+
+	private byte[] readTag(InputStream in) throws IOException {
+		byte[] tag = new byte[TAG_LENGTH];
+		read(in, tag);
+		return tag;
+	}
+
+	private SyncSession createIncomingSession(StreamContext ctx,
+			TransportConnectionReader r) throws IOException {
+		InputStream streamReader = streamReaderFactory.createStreamReader(
+				r.getInputStream(), ctx);
+		ContactId c = requireNonNull(ctx.getContactId());
+		return syncSessionFactory.createIncomingSession(c, streamReader);
+	}
+
+	private SyncSession createSimplexOutgoingSession(StreamContext ctx,
+			TransportConnectionWriter w) throws IOException {
+		StreamWriter streamWriter = streamWriterFactory.createStreamWriter(
+				w.getOutputStream(), ctx);
+		ContactId c = requireNonNull(ctx.getContactId());
+		return syncSessionFactory.createSimplexOutgoingSession(c,
+				w.getMaxLatency(), streamWriter);
+	}
+
+	private SyncSession createDuplexOutgoingSession(StreamContext ctx,
+			TransportConnectionWriter w) throws IOException {
+		StreamWriter streamWriter = streamWriterFactory.createStreamWriter(
+				w.getOutputStream(), ctx);
+		ContactId c = requireNonNull(ctx.getContactId());
+		return syncSessionFactory.createDuplexOutgoingSession(c,
+				w.getMaxLatency(), w.getMaxIdleTime(), streamWriter);
+	}
+
+	private void disposeOnError(TransportConnectionReader reader,
+			boolean recognised) {
+		try {
+			reader.dispose(true, recognised);
+		} catch (IOException e) {
+			logException(LOG, WARNING, e);
+		}
+	}
+
+	private void disposeOnError(TransportConnectionWriter writer) {
+		try {
+			writer.dispose(true);
+		} catch (IOException e) {
+			logException(LOG, WARNING, e);
+		}
+	}
+
+	private class ManageIncomingSimplexConnection implements Runnable {
+
+		private final TransportId transportId;
+		private final TransportConnectionReader reader;
+
+		private ManageIncomingSimplexConnection(TransportId transportId,
+				TransportConnectionReader reader) {
+			this.transportId = transportId;
+			this.reader = reader;
+		}
+
+		@Override
+		public void run() {
+			// Read and recognise the tag
+			StreamContext ctx;
+			try {
+				byte[] tag = readTag(reader.getInputStream());
+				ctx = keyManager.getStreamContext(transportId, tag);
+			} catch (IOException | DbException e) {
+				logException(LOG, WARNING, e);
+				onError(false);
+				return;
+			}
+			if (ctx == null) {
+				LOG.info("Unrecognised tag");
+				onError(false);
+				return;
+			}
+			ContactId contactId = ctx.getContactId();
+			if (contactId == null) {
+				LOG.warning("Received rendezvous stream, expected contact");
+				onError(true);
+				return;
+			}
+			if (ctx.isHandshakeMode()) {
+				// TODO: Support handshake mode for contacts
+				LOG.warning("Received handshake tag, expected rotation mode");
+				onError(true);
+				return;
+			}
+			connectionRegistry.registerConnection(contactId, transportId, true);
+			try {
+				// Create and run the incoming session
+				createIncomingSession(ctx, reader).run();
+				reader.dispose(false, true);
+			} catch (IOException e) {
+				logException(LOG, WARNING, e);
+				onError(true);
+			} finally {
+				connectionRegistry.unregisterConnection(contactId, transportId,
+						true);
+			}
+		}
+
+		private void onError(boolean recognised) {
+			disposeOnError(reader, recognised);
+		}
+	}
+
+	private class ManageOutgoingSimplexConnection implements Runnable {
+
+		private final ContactId contactId;
+		private final TransportId transportId;
+		private final TransportConnectionWriter writer;
+
+		private ManageOutgoingSimplexConnection(ContactId contactId,
+				TransportId transportId, TransportConnectionWriter writer) {
+			this.contactId = contactId;
+			this.transportId = transportId;
+			this.writer = writer;
+		}
+
+		@Override
+		public void run() {
+			// Allocate a stream context
+			StreamContext ctx;
+			try {
+				ctx = keyManager.getStreamContext(contactId, transportId);
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+				onError();
+				return;
+			}
+			if (ctx == null) {
+				LOG.warning("Could not allocate stream context");
+				onError();
+				return;
+			}
+			connectionRegistry.registerConnection(contactId, transportId,
+					false);
+			try {
+				// Create and run the outgoing session
+				createSimplexOutgoingSession(ctx, writer).run();
+				writer.dispose(false);
+			} catch (IOException e) {
+				logException(LOG, WARNING, e);
+				onError();
+			} finally {
+				connectionRegistry.unregisterConnection(contactId, transportId,
+						false);
+			}
+		}
+
+		private void onError() {
+			disposeOnError(writer);
+		}
+	}
+
+	private class ManageIncomingDuplexConnection implements Runnable {
+
+		private final TransportId transportId;
+		private final TransportConnectionReader reader;
+		private final TransportConnectionWriter writer;
+
+		@Nullable
+		private volatile SyncSession outgoingSession = null;
+
+		private ManageIncomingDuplexConnection(TransportId transportId,
+				DuplexTransportConnection connection) {
+			this.transportId = transportId;
+			reader = connection.getReader();
+			writer = connection.getWriter();
+		}
+
+		@Override
+		public void run() {
+			// Read and recognise the tag
+			StreamContext ctx;
+			try {
+				byte[] tag = readTag(reader.getInputStream());
+				ctx = keyManager.getStreamContext(transportId, tag);
+			} catch (IOException | DbException e) {
+				logException(LOG, WARNING, e);
+				onReadError(false);
+				return;
+			}
+			if (ctx == null) {
+				LOG.info("Unrecognised tag");
+				onReadError(false);
+				return;
+			}
+			ContactId contactId = ctx.getContactId();
+			if (contactId == null) {
+				LOG.warning("Expected contact tag, got rendezvous tag");
+				onReadError(true);
+				return;
+			}
+			if (ctx.isHandshakeMode()) {
+				// TODO: Support handshake mode for contacts
+				LOG.warning("Received handshake tag, expected rotation mode");
+				onReadError(true);
+				return;
+			}
+			connectionRegistry.registerConnection(contactId, transportId, true);
+			// Start the outgoing session on another thread
+			ioExecutor.execute(() -> runOutgoingSession(contactId));
+			try {
+				// Create and run the incoming session
+				createIncomingSession(ctx, reader).run();
+				reader.dispose(false, true);
+				// Interrupt the outgoing session so it finishes cleanly
+				SyncSession out = outgoingSession;
+				if (out != null) out.interrupt();
+			} catch (IOException e) {
+				logException(LOG, WARNING, e);
+				onReadError(true);
+			} finally {
+				connectionRegistry.unregisterConnection(contactId, transportId,
+						true);
+			}
+		}
+
+		private void runOutgoingSession(ContactId contactId) {
+			// Allocate a stream context
+			StreamContext ctx;
+			try {
+				ctx = keyManager.getStreamContext(contactId, transportId);
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+				onWriteError();
+				return;
+			}
+			if (ctx == null) {
+				LOG.warning("Could not allocate stream context");
+				onWriteError();
+				return;
+			}
+			try {
+				// Create and run the outgoing session
+				SyncSession out = createDuplexOutgoingSession(ctx, writer);
+				outgoingSession = out;
+				out.run();
+				writer.dispose(false);
+			} catch (IOException e) {
+				logException(LOG, WARNING, e);
+				onWriteError();
+			}
+		}
+
+		private void onReadError(boolean recognised) {
+			disposeOnError(reader, recognised);
+			disposeOnError(writer);
+			// Interrupt the outgoing session so it finishes
+			SyncSession out = outgoingSession;
+			if (out != null) out.interrupt();
+		}
+
+		private void onWriteError() {
+			disposeOnError(reader, true);
+			disposeOnError(writer);
+		}
+	}
+
+	private class ManageOutgoingDuplexConnection implements Runnable {
+
+		private final ContactId contactId;
+		private final TransportId transportId;
+		private final TransportConnectionReader reader;
+		private final TransportConnectionWriter writer;
+
+		@Nullable
+		private volatile SyncSession outgoingSession = null;
+
+		private ManageOutgoingDuplexConnection(ContactId contactId,
+				TransportId transportId, DuplexTransportConnection connection) {
+			this.contactId = contactId;
+			this.transportId = transportId;
+			reader = connection.getReader();
+			writer = connection.getWriter();
+		}
+
+		@Override
+		public void run() {
+			// Allocate a stream context
+			StreamContext ctx;
+			try {
+				ctx = keyManager.getStreamContext(contactId, transportId);
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+				onWriteError();
+				return;
+			}
+			if (ctx == null) {
+				LOG.warning("Could not allocate stream context");
+				onWriteError();
+				return;
+			}
+			if (ctx.isHandshakeMode()) {
+				// TODO: Support handshake mode for contacts
+				LOG.warning("Cannot use handshake mode stream context");
+				onWriteError();
+				return;
+			}
+			// Start the incoming session on another thread
+			ioExecutor.execute(this::runIncomingSession);
+			try {
+				// Create and run the outgoing session
+				SyncSession out = createDuplexOutgoingSession(ctx, writer);
+				outgoingSession = out;
+				out.run();
+				writer.dispose(false);
+			} catch (IOException e) {
+				logException(LOG, WARNING, e);
+				onWriteError();
+			}
+		}
+
+		private void runIncomingSession() {
+			// Read and recognise the tag
+			StreamContext ctx;
+			try {
+				byte[] tag = readTag(reader.getInputStream());
+				ctx = keyManager.getStreamContext(transportId, tag);
+			} catch (IOException | DbException e) {
+				logException(LOG, WARNING, e);
+				onReadError();
+				return;
+			}
+			// Unrecognised tags are suspicious in this case
+			if (ctx == null) {
+				LOG.warning("Unrecognised tag for returning stream");
+				onReadError();
+				return;
+			}
+			// Check that the stream comes from the expected contact
+			ContactId inContactId = ctx.getContactId();
+			if (inContactId == null) {
+				LOG.warning("Expected contact tag, got rendezvous tag");
+				onReadError();
+				return;
+			}
+			if (!contactId.equals(inContactId)) {
+				LOG.warning("Wrong contact ID for returning stream");
+				onReadError();
+				return;
+			}
+			if (ctx.isHandshakeMode()) {
+				// TODO: Support handshake mode for contacts
+				LOG.warning("Received handshake tag, expected rotation mode");
+				onReadError();
+				return;
+			}
+			connectionRegistry.registerConnection(contactId, transportId,
+					false);
+			try {
+				// Create and run the incoming session
+				createIncomingSession(ctx, reader).run();
+				reader.dispose(false, true);
+				// Interrupt the outgoing session so it finishes cleanly
+				SyncSession out = outgoingSession;
+				if (out != null) out.interrupt();
+			} catch (IOException e) {
+				logException(LOG, WARNING, e);
+				onReadError();
+			} finally {
+				connectionRegistry.unregisterConnection(contactId, transportId,
+						false);
+			}
+		}
+
+		private void onReadError() {
+			// 'Recognised' is always true for outgoing connections
+			disposeOnError(reader, true);
+			disposeOnError(writer);
+			// Interrupt the outgoing session so it finishes
+			SyncSession out = outgoingSession;
+			if (out != null) out.interrupt();
+		}
+
+		private void onWriteError() {
+			disposeOnError(reader, true);
+			disposeOnError(writer);
+		}
+	}
+
+	private class ManageIncomingHandshakeConnection implements Runnable {
+
+		private final PendingContactId pendingContactId;
+		private final TransportId transportId;
+		private final DuplexTransportConnection connection;
+		private final TransportConnectionReader reader;
+		private final TransportConnectionWriter writer;
+
+		private ManageIncomingHandshakeConnection(
+				PendingContactId pendingContactId, TransportId transportId,
+				DuplexTransportConnection connection) {
+			this.pendingContactId = pendingContactId;
+			this.transportId = transportId;
+			this.connection = connection;
+			reader = connection.getReader();
+			writer = connection.getWriter();
+		}
+
+		@Override
+		public void run() {
+			// Read and recognise the tag
+			StreamContext ctxIn;
+			try {
+				byte[] tag = readTag(reader.getInputStream());
+				ctxIn = keyManager.getStreamContext(transportId, tag);
+			} catch (IOException | DbException e) {
+				logException(LOG, WARNING, e);
+				onError(false);
+				return;
+			}
+			if (ctxIn == null) {
+				LOG.info("Unrecognised tag");
+				onError(false);
+				return;
+			}
+			PendingContactId inPendingContactId = ctxIn.getPendingContactId();
+			if (inPendingContactId == null) {
+				LOG.warning("Expected rendezvous tag, got contact tag");
+				onError(true);
+				return;
+			}
+			// Allocate the outgoing stream context
+			StreamContext ctxOut;
+			try {
+				ctxOut = keyManager.getStreamContext(pendingContactId,
+						transportId);
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+				onError(true);
+				return;
+			}
+			if (ctxOut == null) {
+				LOG.warning("Could not allocate stream context");
+				onError(true);
+				return;
+			}
+			// Close the connection if it's redundant
+			if (!connectionRegistry.registerConnection(pendingContactId)) {
+				LOG.info("Redundant rendezvous connection");
+				onError(true);
+				return;
+			}
+			// Handshake and exchange contacts
+			try {
+				InputStream in = streamReaderFactory.createStreamReader(
+						reader.getInputStream(), ctxIn);
+				// Flush the output stream to send the outgoing stream header
+				StreamWriter out = streamWriterFactory.createStreamWriter(
+						writer.getOutputStream(), ctxOut);
+				out.getOutputStream().flush();
+				HandshakeResult result = handshakeManager.handshake(
+						pendingContactId, in, out);
+				Contact contact = contactExchangeManager.exchangeContacts(
+						pendingContactId, connection, result.getMasterKey(),
+						result.isAlice(), false);
+				connectionRegistry.unregisterConnection(pendingContactId, true);
+				// Reuse the connection as a transport connection
+				manageOutgoingConnection(contact.getId(), transportId,
+						connection);
+			} catch (IOException | DbException e) {
+				logException(LOG, WARNING, e);
+				onError(true);
+				connectionRegistry.unregisterConnection(pendingContactId,
+						false);
+			}
+		}
+
+		private void onError(boolean recognised) {
+			disposeOnError(reader, recognised);
+			disposeOnError(writer);
+		}
+	}
+
+	private class ManageOutgoingHandshakeConnection implements Runnable {
+
+		private final PendingContactId pendingContactId;
+		private final TransportId transportId;
+		private final DuplexTransportConnection connection;
+		private final TransportConnectionReader reader;
+		private final TransportConnectionWriter writer;
+
+		private ManageOutgoingHandshakeConnection(
+				PendingContactId pendingContactId, TransportId transportId,
+				DuplexTransportConnection connection) {
+			this.pendingContactId = pendingContactId;
+			this.transportId = transportId;
+			this.connection = connection;
+			reader = connection.getReader();
+			writer = connection.getWriter();
+		}
+
+		@Override
+		public void run() {
+			// Allocate the outgoing stream context
+			StreamContext ctxOut;
+			try {
+				ctxOut = keyManager.getStreamContext(pendingContactId,
+						transportId);
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+				onError();
+				return;
+			}
+			if (ctxOut == null) {
+				LOG.warning("Could not allocate stream context");
+				onError();
+				return;
+			}
+			// Flush the output stream to send the outgoing stream header
+			StreamWriter out;
+			try {
+				out = streamWriterFactory.createStreamWriter(
+						writer.getOutputStream(), ctxOut);
+				out.getOutputStream().flush();
+			} catch (IOException e) {
+				logException(LOG, WARNING, e);
+				onError();
+				return;
+			}
+			// Read and recognise the tag
+			StreamContext ctxIn;
+			try {
+				byte[] tag = readTag(reader.getInputStream());
+				ctxIn = keyManager.getStreamContext(transportId, tag);
+			} catch (IOException | DbException e) {
+				logException(LOG, WARNING, e);
+				onError();
+				return;
+			}
+			// Unrecognised tags are suspicious in this case
+			if (ctxIn == null) {
+				LOG.warning("Unrecognised tag for returning stream");
+				onError();
+				return;
+			}
+			// Check that the stream comes from the expected pending contact
+			PendingContactId inPendingContactId = ctxIn.getPendingContactId();
+			if (inPendingContactId == null) {
+				LOG.warning("Expected rendezvous tag, got contact tag");
+				onError();
+				return;
+			}
+			if (!inPendingContactId.equals(pendingContactId)) {
+				LOG.warning("Wrong pending contact ID for returning stream");
+				onError();
+				return;
+			}
+			// Close the connection if it's redundant
+			if (!connectionRegistry.registerConnection(pendingContactId)) {
+				LOG.info("Redundant rendezvous connection");
+				onError();
+				return;
+			}
+			// Handshake and exchange contacts
+			try {
+				InputStream in = streamReaderFactory.createStreamReader(
+						reader.getInputStream(), ctxIn);
+				HandshakeResult result = handshakeManager.handshake(
+						pendingContactId, in, out);
+				Contact contact = contactExchangeManager.exchangeContacts(
+						pendingContactId, connection, result.getMasterKey(),
+						result.isAlice(), false);
+				connectionRegistry.unregisterConnection(pendingContactId, true);
+				// Reuse the connection as a transport connection
+				manageOutgoingConnection(contact.getId(), transportId,
+						connection);
+			} catch (IOException | DbException e) {
+				logException(LOG, WARNING, e);
+				onError();
+				connectionRegistry.unregisterConnection(pendingContactId,
+						false);
+			}
+		}
+
+		private void onError() {
+			// 'Recognised' is always true for outgoing connections
+			disposeOnError(reader, true);
+			disposeOnError(writer);
+		}
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/plugin/ConnectionRegistryImpl.java

@@ -0,0 +1,150 @@
+package org.briarproject.bramble.plugin;
+
+import org.briarproject.bramble.api.Multiset;
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.contact.PendingContactId;
+import org.briarproject.bramble.api.event.EventBus;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.ConnectionRegistry;
+import org.briarproject.bramble.api.plugin.TransportId;
+import org.briarproject.bramble.api.plugin.event.ConnectionClosedEvent;
+import org.briarproject.bramble.api.plugin.event.ConnectionOpenedEvent;
+import org.briarproject.bramble.api.plugin.event.ContactConnectedEvent;
+import org.briarproject.bramble.api.plugin.event.ContactDisconnectedEvent;
+import org.briarproject.bramble.api.rendezvous.event.RendezvousConnectionClosedEvent;
+import org.briarproject.bramble.api.rendezvous.event.RendezvousConnectionOpenedEvent;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.logging.Logger;
+
+import javax.annotation.concurrent.GuardedBy;
+import javax.annotation.concurrent.ThreadSafe;
+import javax.inject.Inject;
+
+import static java.util.logging.Level.INFO;
+import static java.util.logging.Logger.getLogger;
+
+@ThreadSafe
+@NotNullByDefault
+class ConnectionRegistryImpl implements ConnectionRegistry {
+
+	private static final Logger LOG =
+			getLogger(ConnectionRegistryImpl.class.getName());
+
+	private final EventBus eventBus;
+
+	private final Object lock = new Object();
+	@GuardedBy("lock")
+	private final Map<TransportId, Multiset<ContactId>> contactConnections;
+	@GuardedBy("lock")
+	private final Multiset<ContactId> contactCounts;
+	@GuardedBy("lock")
+	private final Set<PendingContactId> connectedPendingContacts;
+
+	@Inject
+	ConnectionRegistryImpl(EventBus eventBus) {
+		this.eventBus = eventBus;
+		contactConnections = new HashMap<>();
+		contactCounts = new Multiset<>();
+		connectedPendingContacts = new HashSet<>();
+	}
+
+	@Override
+	public void registerConnection(ContactId c, TransportId t,
+			boolean incoming) {
+		if (LOG.isLoggable(INFO)) {
+			if (incoming) LOG.info("Incoming connection registered: " + t);
+			else LOG.info("Outgoing connection registered: " + t);
+		}
+		boolean firstConnection = false;
+		synchronized (lock) {
+			Multiset<ContactId> m = contactConnections.get(t);
+			if (m == null) {
+				m = new Multiset<>();
+				contactConnections.put(t, m);
+			}
+			m.add(c);
+			if (contactCounts.add(c) == 1) firstConnection = true;
+		}
+		eventBus.broadcast(new ConnectionOpenedEvent(c, t, incoming));
+		if (firstConnection) {
+			LOG.info("Contact connected");
+			eventBus.broadcast(new ContactConnectedEvent(c));
+		}
+	}
+
+	@Override
+	public void unregisterConnection(ContactId c, TransportId t,
+			boolean incoming) {
+		if (LOG.isLoggable(INFO)) {
+			if (incoming) LOG.info("Incoming connection unregistered: " + t);
+			else LOG.info("Outgoing connection unregistered: " + t);
+		}
+		boolean lastConnection = false;
+		synchronized (lock) {
+			Multiset<ContactId> m = contactConnections.get(t);
+			if (m == null || !m.contains(c))
+				throw new IllegalArgumentException();
+			m.remove(c);
+			if (contactCounts.remove(c) == 0) lastConnection = true;
+		}
+		eventBus.broadcast(new ConnectionClosedEvent(c, t, incoming));
+		if (lastConnection) {
+			LOG.info("Contact disconnected");
+			eventBus.broadcast(new ContactDisconnectedEvent(c));
+		}
+	}
+
+	@Override
+	public Collection<ContactId> getConnectedContacts(TransportId t) {
+		synchronized (lock) {
+			Multiset<ContactId> m = contactConnections.get(t);
+			if (m == null) return Collections.emptyList();
+			List<ContactId> ids = new ArrayList<>(m.keySet());
+			if (LOG.isLoggable(INFO))
+				LOG.info(ids.size() + " contacts connected: " + t);
+			return ids;
+		}
+	}
+
+	@Override
+	public boolean isConnected(ContactId c, TransportId t) {
+		synchronized (lock) {
+			Multiset<ContactId> m = contactConnections.get(t);
+			return m != null && m.contains(c);
+		}
+	}
+
+	@Override
+	public boolean isConnected(ContactId c) {
+		synchronized (lock) {
+			return contactCounts.contains(c);
+		}
+	}
+
+	@Override
+	public boolean registerConnection(PendingContactId p) {
+		boolean added;
+		synchronized (lock) {
+			added = connectedPendingContacts.add(p);
+		}
+		if (added) eventBus.broadcast(new RendezvousConnectionOpenedEvent(p));
+		return added;
+	}
+
+	@Override
+	public void unregisterConnection(PendingContactId p, boolean success) {
+		synchronized (lock) {
+			if (!connectedPendingContacts.remove(p))
+				throw new IllegalArgumentException();
+		}
+		eventBus.broadcast(new RendezvousConnectionClosedEvent(p, success));
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/plugin/PluginManagerImpl.java

@@ -1,12 +1,12 @@
 package org.briarproject.bramble.plugin;
 
-import org.briarproject.bramble.api.connection.ConnectionManager;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.lifecycle.IoExecutor;
 import org.briarproject.bramble.api.lifecycle.Service;
 import org.briarproject.bramble.api.lifecycle.ServiceException;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.ConnectionManager;
 import org.briarproject.bramble.api.plugin.Plugin;
 import org.briarproject.bramble.api.plugin.Plugin.State;
 import org.briarproject.bramble.api.plugin.PluginCallback;

bramble-core/src/main/java/org/briarproject/bramble/plugin/PluginModule.java

@@ -2,6 +2,9 @@ package org.briarproject.bramble.plugin;
 
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.lifecycle.LifecycleManager;
+import org.briarproject.bramble.api.plugin.BackoffFactory;
+import org.briarproject.bramble.api.plugin.ConnectionManager;
+import org.briarproject.bramble.api.plugin.ConnectionRegistry;
 import org.briarproject.bramble.api.plugin.PluginConfig;
 import org.briarproject.bramble.api.plugin.PluginManager;
 
@@ -21,6 +24,25 @@ public class PluginModule {
 		Poller poller;
 	}
 
+	@Provides
+	BackoffFactory provideBackoffFactory() {
+		return new BackoffFactoryImpl();
+	}
+
+	@Provides
+	@Singleton
+	ConnectionManager provideConnectionManager(
+			ConnectionManagerImpl connectionManager) {
+		return connectionManager;
+	}
+
+	@Provides
+	@Singleton
+	ConnectionRegistry provideConnectionRegistry(
+			ConnectionRegistryImpl connectionRegistry) {
+		return connectionRegistry;
+	}
+
 	@Provides
 	@Singleton
 	PluginManager providePluginManager(LifecycleManager lifecycleManager,

bramble-core/src/main/java/org/briarproject/bramble/plugin/PollerImpl.java

@@ -1,8 +1,6 @@
 package org.briarproject.bramble.plugin;
 
 import org.briarproject.bramble.api.Pair;
-import org.briarproject.bramble.api.connection.ConnectionManager;
-import org.briarproject.bramble.api.connection.ConnectionRegistry;
 import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.contact.event.ContactAddedEvent;
 import org.briarproject.bramble.api.db.DbException;
@@ -11,6 +9,9 @@ import org.briarproject.bramble.api.event.EventListener;
 import org.briarproject.bramble.api.lifecycle.IoExecutor;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.ConnectionHandler;
+import org.briarproject.bramble.api.plugin.ConnectionManager;
+import org.briarproject.bramble.api.plugin.ConnectionRegistry;
+import org.briarproject.bramble.api.plugin.DiscoveryHandler;
 import org.briarproject.bramble.api.plugin.Plugin;
 import org.briarproject.bramble.api.plugin.PluginManager;
 import org.briarproject.bramble.api.plugin.TransportConnectionReader;
@@ -19,6 +20,7 @@ import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
 import org.briarproject.bramble.api.plugin.event.ConnectionClosedEvent;
+import org.briarproject.bramble.api.plugin.event.ConnectionOpenedEvent;
 import org.briarproject.bramble.api.plugin.event.TransportActiveEvent;
 import org.briarproject.bramble.api.plugin.event.TransportInactiveEvent;
 import org.briarproject.bramble.api.plugin.simplex.SimplexPlugin;
@@ -31,6 +33,7 @@ import java.security.SecureRandom;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.concurrent.Executor;
@@ -95,10 +98,16 @@ class PollerImpl implements Poller, EventListener {
 			connectToContact(c.getContactId());
 		} else if (e instanceof ConnectionClosedEvent) {
 			ConnectionClosedEvent c = (ConnectionClosedEvent) e;
-			// If an outgoing connection failed, try to reconnect
+			// Reschedule polling, the polling interval may have decreased
-			if (!c.isIncoming() && c.isException()) {
+			reschedule(c.getTransportId());
+			if (!c.isIncoming()) {
+				// Connect to the disconnected contact
 				connectToContact(c.getContactId(), c.getTransportId());
 			}
+		} else if (e instanceof ConnectionOpenedEvent) {
+			ConnectionOpenedEvent c = (ConnectionOpenedEvent) e;
+			// Reschedule polling, the polling interval may have decreased
+			reschedule(c.getTransportId());
 		} else if (e instanceof TransportActiveEvent) {
 			TransportActiveEvent t = (TransportActiveEvent) e;
 			// Poll the newly activated transport
@@ -157,6 +166,12 @@ class PollerImpl implements Poller, EventListener {
 		});
 	}
 
+	private void reschedule(TransportId t) {
+		Plugin p = pluginManager.getPlugin(t);
+		if (p != null && p.shouldPoll())
+			schedule(p, p.getPollingInterval(), false);
+	}
+
 	private void pollNow(TransportId t) {
 		Plugin p = pluginManager.getPlugin(t);
 		// Randomise next polling interval
@@ -197,18 +212,20 @@ class PollerImpl implements Poller, EventListener {
 	@IoExecutor
 	private void poll(Plugin p) {
 		TransportId t = p.getId();
-		if (LOG.isLoggable(INFO)) LOG.info("Polling plugin " + t);
+		if (LOG.isLoggable(INFO)) LOG.info("Polling " + t);
 		try {
 			Map<ContactId, TransportProperties> remote =
 					transportPropertyManager.getRemoteProperties(t);
 			Collection<ContactId> connected =
-					connectionRegistry.getConnectedOrBetterContacts(t);
+					connectionRegistry.getConnectedContacts(t);
-			Collection<Pair<TransportProperties, ConnectionHandler>>
+			List<Pair<TransportProperties, ConnectionHandler>> properties =
-					properties = new ArrayList<>();
+					new ArrayList<>();
 			for (Entry<ContactId, TransportProperties> e : remote.entrySet()) {
 				ContactId c = e.getKey();
-				if (!connected.contains(c))
+				if (!connected.contains(c)) {
-					properties.add(new Pair<>(e.getValue(), new Handler(c, t)));
+					ConnHandler handler = new ConnHandler(c, t);
+					properties.add(new Pair<>(e.getValue(), handler));
+				}
 			}
 			if (!properties.isEmpty()) p.poll(properties);
 		} catch (DbException e) {
@@ -216,6 +233,30 @@ class PollerImpl implements Poller, EventListener {
 		}
 	}
 
+	@IoExecutor
+	private void discover(DuplexPlugin p) {
+		TransportId t = p.getId();
+		if (LOG.isLoggable(INFO)) LOG.info("Discovering peers for " + t);
+		try {
+			Map<ContactId, TransportProperties> remote =
+					transportPropertyManager.getRemoteProperties(t);
+			Collection<ContactId> connected =
+					connectionRegistry.getConnectedContacts(t);
+			List<Pair<TransportProperties, DiscoveryHandler>> properties =
+					new ArrayList<>();
+			for (Entry<ContactId, TransportProperties> e : remote.entrySet()) {
+				ContactId c = e.getKey();
+				if (!connected.contains(c)) {
+					DiscoHandler handler = new DiscoHandler(c, p);
+					properties.add(new Pair<>(e.getValue(), handler));
+				}
+			}
+			if (!properties.isEmpty()) p.discoverPeers(properties);
+		} catch (DbException e) {
+			logException(LOG, WARNING, e);
+		}
+	}
+
 	private class ScheduledPollTask {
 
 		private final PollTask task;
@@ -255,16 +296,23 @@ class PollerImpl implements Poller, EventListener {
 			int delay = plugin.getPollingInterval();
 			if (randomiseNext) delay = (int) (delay * random.nextDouble());
 			schedule(plugin, delay, false);
-			poll(plugin);
+			// FIXME: Revert
+			if (plugin instanceof DuplexPlugin) {
+				DuplexPlugin d = (DuplexPlugin) plugin;
+				if (d.supportsDiscovery()) discover(d);
+				else poll(d);
+			} else {
+				poll(plugin);
+			}
 		}
 	}
 
-	private class Handler implements ConnectionHandler {
+	private class ConnHandler implements ConnectionHandler {
 
 		private final ContactId contactId;
 		private final TransportId transportId;
 
-		private Handler(ContactId contactId, TransportId transportId) {
+		private ConnHandler(ContactId contactId, TransportId transportId) {
 			this.contactId = contactId;
 			this.transportId = transportId;
 		}
@@ -287,4 +335,27 @@ class PollerImpl implements Poller, EventListener {
 					transportId, w);
 		}
 	}
+
+	private class DiscoHandler implements DiscoveryHandler {
+
+		private final ContactId contactId;
+		private final DuplexPlugin plugin;
+
+		private DiscoHandler(ContactId contactId, DuplexPlugin plugin) {
+			this.contactId = contactId;
+			this.plugin = plugin;
+		}
+
+		@Override
+		public void handleDevice(TransportProperties p) {
+			LOG.info("Discovered contact via " + plugin.getId());
+			ioExecutor.execute(() -> {
+				DuplexTransportConnection c = plugin.createConnection(p);
+				if (c != null) {
+					connectionManager.manageOutgoingConnection(contactId,
+							plugin.getId(), c);
+				}
+			});
+		}
+	}
 }

bramble-core/src/main/java/org/briarproject/bramble/plugin/bluetooth/BluetoothConnectionLimiter.java

@@ -23,9 +23,17 @@ interface BluetoothConnectionLimiter {
 	boolean canOpenContactConnection();
 
 	/**
-	 * Informs the limiter that the given connection has been opened.
+	 * Informs the limiter that a contact connection has been opened. The
+	 * limiter may close the new connection if key agreement is in progress.
+	 * <p/>
+	 * Returns false if the limiter has closed the new connection.
 	 */
-	void connectionOpened(DuplexTransportConnection conn);
+	boolean contactConnectionOpened(DuplexTransportConnection conn);
+
+	/**
+	 * Informs the limiter that a key agreement connection has been opened.
+	 */
+	void keyAgreementConnectionOpened(DuplexTransportConnection conn);
 
 	/**
 	 * Informs the limiter that the given connection has been closed.

bramble-core/src/main/java/org/briarproject/bramble/plugin/bluetooth/BluetoothConnectionLimiterImpl.java

@@ -1,48 +1,46 @@
 package org.briarproject.bramble.plugin.bluetooth;
 
-import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
-import org.briarproject.bramble.api.sync.event.CloseSyncConnectionsEvent;
 
+import java.io.IOException;
+import java.util.ArrayList;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.logging.Logger;
 
-import javax.annotation.concurrent.GuardedBy;
 import javax.annotation.concurrent.ThreadSafe;
 
 import static java.util.logging.Level.INFO;
-import static java.util.logging.Logger.getLogger;
+import static java.util.logging.Level.WARNING;
-import static org.briarproject.bramble.api.plugin.BluetoothConstants.ID;
+import static org.briarproject.bramble.util.LogUtils.logException;
 
 @NotNullByDefault
 @ThreadSafe
 class BluetoothConnectionLimiterImpl implements BluetoothConnectionLimiter {
 
 	private static final Logger LOG =
-			getLogger(BluetoothConnectionLimiterImpl.class.getName());
+			Logger.getLogger(BluetoothConnectionLimiterImpl.class.getName());
-
-	private final EventBus eventBus;
 
 	private final Object lock = new Object();
-	@GuardedBy("lock")
+	// The following are locking: lock
-	private final List<DuplexTransportConnection> connections =
+	private final LinkedList<DuplexTransportConnection> connections =
 			new LinkedList<>();
-	@GuardedBy("lock")
 	private boolean keyAgreementInProgress = false;
 
-	BluetoothConnectionLimiterImpl(EventBus eventBus) {
-		this.eventBus = eventBus;
-	}
-
 	@Override
 	public void keyAgreementStarted() {
+		List<DuplexTransportConnection> close;
 		synchronized (lock) {
 			keyAgreementInProgress = true;
+			close = new ArrayList<>(connections);
+			connections.clear();
 		}
-		LOG.info("Key agreement started");
+		if (LOG.isLoggable(INFO)) {
-		eventBus.broadcast(new CloseSyncConnectionsEvent(ID));
+			LOG.info("Key agreement started, closing " + close.size() +
+					" connections");
+		}
+		for (DuplexTransportConnection conn : close) tryToClose(conn);
 	}
 
 	@Override
@@ -67,22 +65,44 @@ class BluetoothConnectionLimiterImpl implements BluetoothConnectionLimiter {
 	}
 
 	@Override
-	public void connectionOpened(DuplexTransportConnection conn) {
+	public boolean contactConnectionOpened(DuplexTransportConnection conn) {
+		boolean accept = true;
 		synchronized (lock) {
-			connections.add(conn);
+			if (keyAgreementInProgress) {
-			if (LOG.isLoggable(INFO)) {
+				LOG.info("Refusing contact connection during key agreement");
-				LOG.info("Connection opened, " + connections.size() + " open");
+				accept = false;
+			} else {
+				LOG.info("Accepting contact connection");
+				connections.add(conn);
 			}
 		}
+		if (!accept) tryToClose(conn);
+		return accept;
+	}
+
+	@Override
+	public void keyAgreementConnectionOpened(DuplexTransportConnection conn) {
+		synchronized (lock) {
+			LOG.info("Accepting key agreement connection");
+			connections.add(conn);
+		}
+	}
+
+	private void tryToClose(DuplexTransportConnection conn) {
+		try {
+			conn.getWriter().dispose(false);
+			conn.getReader().dispose(false, false);
+		} catch (IOException e) {
+			logException(LOG, WARNING, e);
+		}
 	}
 
 	@Override
 	public void connectionClosed(DuplexTransportConnection conn) {
 		synchronized (lock) {
 			connections.remove(conn);
-			if (LOG.isLoggable(INFO)) {
+			if (LOG.isLoggable(INFO))
 				LOG.info("Connection closed, " + connections.size() + " open");
-			}
 		}
 	}
 

bramble-core/src/main/java/org/briarproject/bramble/plugin/bluetooth/BluetoothPlugin.java

@@ -5,7 +5,6 @@ import org.briarproject.bramble.api.Pair;
 import org.briarproject.bramble.api.data.BdfList;
 import org.briarproject.bramble.api.event.Event;
 import org.briarproject.bramble.api.event.EventListener;
-import org.briarproject.bramble.api.io.TimeoutMonitor;
 import org.briarproject.bramble.api.keyagreement.KeyAgreementConnection;
 import org.briarproject.bramble.api.keyagreement.KeyAgreementListener;
 import org.briarproject.bramble.api.keyagreement.event.KeyAgreementListeningEvent;
@@ -14,7 +13,9 @@ import org.briarproject.bramble.api.lifecycle.IoExecutor;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
+import org.briarproject.bramble.api.plugin.Backoff;
 import org.briarproject.bramble.api.plugin.ConnectionHandler;
+import org.briarproject.bramble.api.plugin.DiscoveryHandler;
 import org.briarproject.bramble.api.plugin.PluginCallback;
 import org.briarproject.bramble.api.plugin.PluginException;
 import org.briarproject.bramble.api.plugin.TransportId;
@@ -31,7 +32,7 @@ import org.briarproject.bramble.api.settings.event.SettingsUpdatedEvent;
 
 import java.io.IOException;
 import java.security.SecureRandom;
-import java.util.Collection;
+import java.util.List;
 import java.util.UUID;
 import java.util.concurrent.Executor;
 import java.util.concurrent.atomic.AtomicBoolean;
@@ -45,7 +46,6 @@ import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.TRANSPORT_ID_BLUETOOTH;
-import static org.briarproject.bramble.api.plugin.BluetoothConstants.DEFAULT_PREF_PLUGIN_ENABLE;
 import static org.briarproject.bramble.api.plugin.BluetoothConstants.ID;
 import static org.briarproject.bramble.api.plugin.BluetoothConstants.PROP_ADDRESS;
 import static org.briarproject.bramble.api.plugin.BluetoothConstants.PROP_UUID;
@@ -68,12 +68,12 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 			getLogger(BluetoothPlugin.class.getName());
 
 	final BluetoothConnectionLimiter connectionLimiter;
-	final TimeoutMonitor timeoutMonitor;
 
 	private final Executor ioExecutor;
 	private final SecureRandom secureRandom;
+	private final Backoff backoff;
 	private final PluginCallback callback;
-	private final int maxLatency, maxIdleTime, pollingInterval;
+	private final int maxLatency;
 	private final AtomicBoolean used = new AtomicBoolean(false);
 
 	protected final PluginState state = new PluginState();
@@ -113,17 +113,14 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 	abstract DuplexTransportConnection discoverAndConnect(String uuid);
 
 	BluetoothPlugin(BluetoothConnectionLimiter connectionLimiter,
-			TimeoutMonitor timeoutMonitor, Executor ioExecutor,
+			Executor ioExecutor, SecureRandom secureRandom,
-			SecureRandom secureRandom, PluginCallback callback, int maxLatency, int maxIdleTime,
+			Backoff backoff, PluginCallback callback, int maxLatency) {
-			int pollingInterval) {
 		this.connectionLimiter = connectionLimiter;
-		this.timeoutMonitor = timeoutMonitor;
 		this.ioExecutor = ioExecutor;
 		this.secureRandom = secureRandom;
+		this.backoff = backoff;
 		this.callback = callback;
 		this.maxLatency = maxLatency;
-		this.maxIdleTime = maxIdleTime;
-		this.pollingInterval = pollingInterval;
 	}
 
 	void onAdapterEnabled() {
@@ -156,15 +153,15 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 
 	@Override
 	public int getMaxIdleTime() {
-		return maxIdleTime;
+		// Bluetooth detects dead connections so we don't need keepalives
+		return Integer.MAX_VALUE;
 	}
 
 	@Override
 	public void start() throws PluginException {
 		if (used.getAndSet(true)) throw new IllegalStateException();
 		Settings settings = callback.getSettings();
-		boolean enabledByUser = settings.getBoolean(PREF_PLUGIN_ENABLE,
+		boolean enabledByUser = settings.getBoolean(PREF_PLUGIN_ENABLE, false);
-				DEFAULT_PREF_PLUGIN_ENABLE);
 		state.setStarted(enabledByUser);
 		try {
 			initialiseAdapter();
@@ -194,6 +191,7 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 				tryToClose(ss);
 				return;
 			}
+			backoff.reset();
 			acceptContactConnections(ss);
 		});
 	}
@@ -235,8 +233,9 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 				return;
 			}
 			LOG.info("Connection received");
-			connectionLimiter.connectionOpened(conn);
+			backoff.reset();
-			callback.handleConnection(conn);
+			if (connectionLimiter.contactConnectionOpened(conn))
+				callback.handleConnection(conn);
 		}
 	}
 
@@ -264,13 +263,14 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 
 	@Override
 	public int getPollingInterval() {
-		return pollingInterval;
+		return backoff.getPollingInterval();
 	}
 
 	@Override
-	public void poll(Collection<Pair<TransportProperties, ConnectionHandler>>
+	public void poll(
-			properties) {
+			List<Pair<TransportProperties, ConnectionHandler>> properties) {
 		if (getState() != ACTIVE) return;
+		backoff.increment();
 		for (Pair<TransportProperties, ConnectionHandler> p : properties) {
 			connect(p.getFirst(), p.getSecond());
 		}
@@ -282,8 +282,14 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 		String uuid = p.get(PROP_UUID);
 		if (isNullOrEmpty(uuid)) return;
 		ioExecutor.execute(() -> {
+			if (getState() != ACTIVE) return;
+			if (!connectionLimiter.canOpenContactConnection()) return;
 			DuplexTransportConnection d = createConnection(p);
-			if (d != null) h.handleConnection(d);
+			if (d != null) {
+				backoff.reset();
+				if (connectionLimiter.contactConnectionOpened(d))
+					h.handleConnection(d);
+			}
 		});
 	}
 
@@ -327,8 +333,9 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 		String uuid = p.get(PROP_UUID);
 		if (isNullOrEmpty(uuid)) return null;
 		DuplexTransportConnection conn = connect(address, uuid);
-		if (conn != null) connectionLimiter.connectionOpened(conn);
+		if (conn == null) return null;
-		return conn;
+		// TODO: Why don't we reset the backoff here?
+		return connectionLimiter.contactConnectionOpened(conn) ? conn : null;
 	}
 
 	@Override
@@ -384,7 +391,7 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 				LOG.info("Connecting to key agreement UUID " + uuid);
 			conn = connect(address, uuid);
 		}
-		if (conn != null) connectionLimiter.connectionOpened(conn);
+		if (conn != null) connectionLimiter.keyAgreementConnectionOpened(conn);
 		return conn;
 	}
 
@@ -405,6 +412,17 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 		throw new UnsupportedOperationException();
 	}
 
+	@Override
+	public boolean supportsDiscovery() {
+		return false;
+	}
+
+	@Override
+	public void discoverPeers(
+			List<Pair<TransportProperties, DiscoveryHandler>> properties) {
+		throw new UnsupportedOperationException();
+	}
+
 	@Override
 	public void eventOccurred(Event e) {
 		if (e instanceof EnableBluetoothEvent) {
@@ -426,8 +444,7 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 
 	@IoExecutor
 	private void onSettingsUpdated(Settings settings) {
-		boolean enabledByUser = settings.getBoolean(PREF_PLUGIN_ENABLE,
+		boolean enabledByUser = settings.getBoolean(PREF_PLUGIN_ENABLE, false);
-				DEFAULT_PREF_PLUGIN_ENABLE);
 		SS ss = state.setEnabledByUser(enabledByUser);
 		State s = getState();
 		if (ss != null) {
@@ -454,7 +471,7 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 		public KeyAgreementConnection accept() throws IOException {
 			DuplexTransportConnection conn = acceptConnection(ss);
 			if (LOG.isLoggable(INFO)) LOG.info(ID + ": Incoming connection");
-			connectionLimiter.connectionOpened(conn);
+			connectionLimiter.keyAgreementConnectionOpened(conn);
 			return new KeyAgreementConnection(conn, ID);
 		}
 

bramble-core/src/main/java/org/briarproject/bramble/plugin/tcp/LanTcpPlugin.java

@@ -5,6 +5,7 @@ import org.briarproject.bramble.api.data.BdfList;
 import org.briarproject.bramble.api.keyagreement.KeyAgreementConnection;
 import org.briarproject.bramble.api.keyagreement.KeyAgreementListener;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.Backoff;
 import org.briarproject.bramble.api.plugin.PluginCallback;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
@@ -13,7 +14,6 @@ import org.briarproject.bramble.api.settings.Settings;
 
 import java.io.IOException;
 import java.net.Inet4Address;
-import java.net.Inet6Address;
 import java.net.InetAddress;
 import java.net.InetSocketAddress;
 import java.net.InterfaceAddress;
@@ -21,9 +21,8 @@ import java.net.ServerSocket;
 import java.net.Socket;
 import java.net.UnknownHostException;
 import java.util.ArrayList;
-import java.util.Deque;
-import java.util.LinkedList;
 import java.util.List;
+import java.util.Random;
 import java.util.concurrent.Executor;
 import java.util.logging.Logger;
 
@@ -31,49 +30,39 @@ import javax.annotation.Nullable;
 
 import static java.lang.Integer.parseInt;
 import static java.util.Collections.addAll;
-import static java.util.Collections.emptyList;
 import static java.util.Collections.sort;
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.TRANSPORT_ID_LAN;
-import static org.briarproject.bramble.api.plugin.LanTcpConstants.DEFAULT_PREF_PLUGIN_ENABLE;
 import static org.briarproject.bramble.api.plugin.LanTcpConstants.ID;
-import static org.briarproject.bramble.api.plugin.LanTcpConstants.PREF_IPV6;
 import static org.briarproject.bramble.api.plugin.LanTcpConstants.PREF_LAN_IP_PORTS;
-import static org.briarproject.bramble.api.plugin.LanTcpConstants.PROP_IPV6;
 import static org.briarproject.bramble.api.plugin.LanTcpConstants.PROP_IP_PORTS;
 import static org.briarproject.bramble.api.plugin.LanTcpConstants.PROP_PORT;
-import static org.briarproject.bramble.api.properties.TransportPropertyConstants.MAX_PROPERTY_LENGTH;
 import static org.briarproject.bramble.util.ByteUtils.MAX_16_BIT_UNSIGNED;
 import static org.briarproject.bramble.util.IoUtils.tryToClose;
 import static org.briarproject.bramble.util.PrivacyUtils.scrubSocketAddress;
-import static org.briarproject.bramble.util.StringUtils.fromHexString;
 import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
 import static org.briarproject.bramble.util.StringUtils.join;
-import static org.briarproject.bramble.util.StringUtils.toHexString;
-import static org.briarproject.bramble.util.StringUtils.utf8IsTooLong;
 
 @NotNullByDefault
 class LanTcpPlugin extends TcpPlugin {
 
 	private static final Logger LOG = getLogger(LanTcpPlugin.class.getName());
 
+	private static final int MAX_ADDRESSES = 4;
 	private static final String SEPARATOR = ",";
 
 	/**
 	 * The IP address of an Android device providing a wifi access point.
-	 * <p>
-	 * Most devices use this address, but at least one device (Honor 8A) may
-	 * use other addresses in the range 192.168.43.0/24.
 	 */
-	private static final InetAddress WIFI_AP_ADDRESS;
+	protected static final InetAddress WIFI_AP_ADDRESS;
 
 	/**
 	 * The IP address of an Android device providing a wifi direct
 	 * legacy mode access point.
 	 */
-	private static final InetAddress WIFI_DIRECT_AP_ADDRESS;
+	protected static final InetAddress WIFI_DIRECT_AP_ADDRESS;
 
 	static {
 		try {
@@ -87,9 +76,9 @@ class LanTcpPlugin extends TcpPlugin {
 		}
 	}
 
-	LanTcpPlugin(Executor ioExecutor, PluginCallback callback, int maxLatency,
+	LanTcpPlugin(Executor ioExecutor, Backoff backoff, PluginCallback callback,
-			int maxIdleTime, int pollingInterval, int connectionTimeout) {
+			int maxLatency, int maxIdleTime, int connectionTimeout) {
-		super(ioExecutor, callback, maxLatency, maxIdleTime, pollingInterval,
+		super(ioExecutor, backoff, callback, maxLatency, maxIdleTime,
 				connectionTimeout);
 	}
 
@@ -103,35 +92,29 @@ class LanTcpPlugin extends TcpPlugin {
 		if (used.getAndSet(true)) throw new IllegalStateException();
 		initialisePortProperty();
 		Settings settings = callback.getSettings();
-		state.setStarted(settings.getBoolean(PREF_PLUGIN_ENABLE,
+		state.setStarted(settings.getBoolean(PREF_PLUGIN_ENABLE, false));
-				DEFAULT_PREF_PLUGIN_ENABLE));
 		bind();
 	}
 
 	protected void initialisePortProperty() {
 		TransportProperties p = callback.getLocalProperties();
 		if (isNullOrEmpty(p.get(PROP_PORT))) {
-			int port = chooseEphemeralPort();
+			int port = new Random().nextInt(32768) + 32768;
 			p.put(PROP_PORT, String.valueOf(port));
 			callback.mergeLocalProperties(p);
 		}
 	}
 
 	@Override
-	protected boolean isEnabledByDefault() {
+	protected List<InetSocketAddress> getLocalSocketAddresses() {
-		return DEFAULT_PREF_PLUGIN_ENABLE;
-	}
-
-	@Override
-	protected List<InetSocketAddress> getLocalSocketAddresses(boolean ipv4) {
 		TransportProperties p = callback.getLocalProperties();
 		int preferredPort = parsePortProperty(p.get(PROP_PORT));
 		String oldIpPorts = p.get(PROP_IP_PORTS);
-		List<InetSocketAddress> olds = parseIpv4SocketAddresses(oldIpPorts);
+		List<InetSocketAddress> olds = parseSocketAddresses(oldIpPorts);
 
 		List<InetSocketAddress> locals = new ArrayList<>();
 		List<InetSocketAddress> fallbacks = new ArrayList<>();
-		for (InetAddress local : getUsableLocalInetAddresses(ipv4)) {
+		for (InetAddress local : getUsableLocalInetAddresses()) {
 			// If we've used this address before, try to use the same port
 			int port = preferredPort;
 			for (InetSocketAddress old : olds) {
@@ -157,17 +140,17 @@ class LanTcpPlugin extends TcpPlugin {
 		}
 	}
 
-	private List<InetSocketAddress> parseIpv4SocketAddresses(String ipPorts) {
+	private List<InetSocketAddress> parseSocketAddresses(String ipPorts) {
 		List<InetSocketAddress> addresses = new ArrayList<>();
 		if (isNullOrEmpty(ipPorts)) return addresses;
 		for (String ipPort : ipPorts.split(SEPARATOR)) {
-			InetSocketAddress a = parseIpv4SocketAddress(ipPort);
+			InetSocketAddress a = parseSocketAddress(ipPort);
 			if (a != null) addresses.add(a);
 		}
 		return addresses;
 	}
 
-	protected List<InetAddress> getUsableLocalInetAddresses(boolean ipv4) {
+	protected List<InetAddress> getUsableLocalInetAddresses() {
 		List<InterfaceAddress> ifAddrs =
 				new ArrayList<>(getLocalInterfaceAddresses());
 		// Prefer longer network prefixes
@@ -176,74 +159,50 @@ class LanTcpPlugin extends TcpPlugin {
 		List<InetAddress> addrs = new ArrayList<>();
 		for (InterfaceAddress ifAddr : ifAddrs) {
 			InetAddress addr = ifAddr.getAddress();
-			if (isAcceptableAddress(addr, ipv4)) addrs.add(addr);
+			if (isAcceptableAddress(addr)) addrs.add(addr);
 		}
 		return addrs;
 	}
 
 	@Override
-	protected void setLocalSocketAddress(InetSocketAddress a, boolean ipv4) {
+	protected void setLocalSocketAddress(InetSocketAddress a) {
-		if (ipv4) setLocalIpv4SocketAddress(a);
-		else setLocalIpv6SocketAddress(a);
-	}
-
-	private void setLocalIpv4SocketAddress(InetSocketAddress a) {
 		String ipPort = getIpPortString(a);
-		updateRecentAddresses(PREF_LAN_IP_PORTS, PROP_IP_PORTS, ipPort);
-	}
-
-	private void setLocalIpv6SocketAddress(InetSocketAddress a) {
-		String hex = toHexString(a.getAddress().getAddress());
-		updateRecentAddresses(PREF_IPV6, PROP_IPV6, hex);
-	}
-
-	private void updateRecentAddresses(String settingKey, String propertyKey,
-			String item) {
 		// Get the list of recently used addresses
-		String setting = callback.getSettings().get(settingKey);
+		String setting = callback.getSettings().get(PREF_LAN_IP_PORTS);
-		Deque<String> recent = new LinkedList<>();
+		List<String> recent = new ArrayList<>();
-		if (!isNullOrEmpty(setting)) {
+		if (!isNullOrEmpty(setting))
 			addAll(recent, setting.split(SEPARATOR));
-		}
+		// Is the address already in the list?
-		if (recent.remove(item)) {
+		if (recent.remove(ipPort)) {
-			// Move the item to the start of the list
+			// Move the address to the start of the list
-			recent.addFirst(item);
+			recent.add(0, ipPort);
 			setting = join(recent, SEPARATOR);
 		} else {
-			// Add the item to the start of the list
+			// Add the address to the start of the list
-			recent.addFirst(item);
+			recent.add(0, ipPort);
-			// Drop items from the end of the list if it's too long to encode
+			// Drop the least recently used address if the list is full
+			if (recent.size() > MAX_ADDRESSES)
+				recent = recent.subList(0, MAX_ADDRESSES);
 			setting = join(recent, SEPARATOR);
-			while (utf8IsTooLong(setting, MAX_PROPERTY_LENGTH)) {
-				recent.removeLast();
-				setting = join(recent, SEPARATOR);
-			}
 			// Update the list of addresses shared with contacts
+			List<String> shared = new ArrayList<>(recent);
+			sort(shared);
+			String property = join(shared, SEPARATOR);
 			TransportProperties properties = new TransportProperties();
-			properties.put(propertyKey, setting);
+			properties.put(PROP_IP_PORTS, property);
 			callback.mergeLocalProperties(properties);
 		}
 		// Save the setting
 		Settings settings = new Settings();
-		settings.put(settingKey, setting);
+		settings.put(PREF_LAN_IP_PORTS, setting);
 		callback.mergeSettings(settings);
 	}
 
-	protected boolean isIpv6LinkLocalAddress(InetAddress a) {
-		return a instanceof Inet6Address && a.isLinkLocalAddress();
-	}
-
 	@Override
 	protected List<InetSocketAddress> getRemoteSocketAddresses(
-			TransportProperties p, boolean ipv4) {
-		if (ipv4) return getRemoteIpv4SocketAddresses(p);
-		else return getRemoteIpv6SocketAddresses(p);
-	}
-
-	private List<InetSocketAddress> getRemoteIpv4SocketAddresses(
 			TransportProperties p) {
 		String ipPorts = p.get(PROP_IP_PORTS);
-		List<InetSocketAddress> remotes = parseIpv4SocketAddresses(ipPorts);
+		List<InetSocketAddress> remotes = parseSocketAddresses(ipPorts);
 		int port = parsePortProperty(p.get(PROP_PORT));
 		// If the contact has a preferred port, we can guess their IP:port when
 		// they're providing a wifi access point
@@ -258,52 +217,20 @@ class LanTcpPlugin extends TcpPlugin {
 		return remotes;
 	}
 
-	private List<InetSocketAddress> getRemoteIpv6SocketAddresses(
+	private boolean isAcceptableAddress(InetAddress a) {
-			TransportProperties p) {
+		// Accept link-local and site-local IPv4 addresses
-		List<InetAddress> addrs = parseIpv6Addresses(p.get(PROP_IPV6));
+		boolean ipv4 = a instanceof Inet4Address;
-		int port = parsePortProperty(p.get(PROP_PORT));
+		boolean loop = a.isLoopbackAddress();
-		if (addrs.isEmpty() || port == 0) return emptyList();
+		boolean link = a.isLinkLocalAddress();
-		List<InetSocketAddress> remotes = new ArrayList<>();
+		boolean site = a.isSiteLocalAddress();
-		for (InetAddress addr : addrs) {
+		return ipv4 && !loop && (link || site);
-			remotes.add(new InetSocketAddress(addr, port));
-		}
-		return remotes;
-	}
-
-	private List<InetAddress> parseIpv6Addresses(String property) {
-		if (isNullOrEmpty(property)) return emptyList();
-		try {
-			List<InetAddress> addrs = new ArrayList<>();
-			for (String hex : property.split(SEPARATOR)) {
-				byte[] ip = fromHexString(hex);
-				if (ip.length == 16) addrs.add(InetAddress.getByAddress(ip));
-			}
-			return addrs;
-		} catch (IllegalArgumentException | UnknownHostException e) {
-			return emptyList();
-		}
-	}
-
-	private boolean isAcceptableAddress(InetAddress a, boolean ipv4) {
-		if (ipv4) {
-			// Accept link-local and site-local IPv4 addresses
-			boolean isIpv4 = a instanceof Inet4Address;
-			boolean link = a.isLinkLocalAddress();
-			boolean site = a.isSiteLocalAddress();
-			return isIpv4 && (link || site);
-		} else {
-			// Accept link-local IPv6 addresses
-			return isIpv6LinkLocalAddress(a);
-		}
 	}
 
 	@Override
 	protected boolean isConnectable(InterfaceAddress local,
 			InetSocketAddress remote) {
 		if (remote.getPort() == 0) return false;
-		InetAddress remoteAddress = remote.getAddress();
+		if (!isAcceptableAddress(remote.getAddress())) return false;
-		boolean ipv4 = local.getAddress() instanceof Inet4Address;
-		if (!isAcceptableAddress(remoteAddress, ipv4)) return false;
 		// Try to determine whether the address is on the same LAN as us
 		byte[] localIp = local.getAddress().getAddress();
 		byte[] remoteIp = remote.getAddress().getAddress();
@@ -361,17 +288,10 @@ class LanTcpPlugin extends TcpPlugin {
 		return new LanKeyAgreementListener(descriptor, ss);
 	}
 
-	private List<InetSocketAddress> getLocalSocketAddresses() {
-		List<InetSocketAddress> addrs = new ArrayList<>();
-		addrs.addAll(getLocalSocketAddresses(true));
-		addrs.addAll(getLocalSocketAddresses(false));
-		return addrs;
-	}
-
 	@Override
 	public DuplexTransportConnection createKeyAgreementConnection(
 			byte[] commitment, BdfList descriptor) {
-		ServerSocket ss = state.getServerSocket(true);
+		ServerSocket ss = state.getServerSocket();
 		if (ss == null) return null;
 		InterfaceAddress local = getLocalInterfaceAddress(ss.getInetAddress());
 		if (local == null) {

bramble-core/src/main/java/org/briarproject/bramble/plugin/tcp/LanTcpPluginFactory.java

@@ -2,6 +2,8 @@ package org.briarproject.bramble.plugin.tcp;
 
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.Backoff;
+import org.briarproject.bramble.api.plugin.BackoffFactory;
 import org.briarproject.bramble.api.plugin.PluginCallback;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
@@ -11,25 +13,28 @@ import java.util.concurrent.Executor;
 
 import javax.annotation.concurrent.Immutable;
 
-import static java.util.concurrent.TimeUnit.MINUTES;
-import static java.util.concurrent.TimeUnit.SECONDS;
 import static org.briarproject.bramble.api.plugin.LanTcpConstants.ID;
 
 @Immutable
 @NotNullByDefault
 public class LanTcpPluginFactory implements DuplexPluginFactory {
 
-	private static final int MAX_LATENCY = (int) SECONDS.toMillis(30);
+	private static final int MAX_LATENCY = 30_000; // 30 seconds
-	private static final int MAX_IDLE_TIME = (int) SECONDS.toMillis(30);
+	private static final int MAX_IDLE_TIME = 30_000; // 30 seconds
-	private static final int POLLING_INTERVAL = (int) MINUTES.toMillis(1);
+	private static final int CONNECTION_TIMEOUT = 3_000; // 3 seconds
-	private static final int CONNECTION_TIMEOUT = (int) SECONDS.toMillis(3);
+	private static final int MIN_POLLING_INTERVAL = 60_000; // 1 minute
+	private static final int MAX_POLLING_INTERVAL = 600_000; // 10 mins
+	private static final double BACKOFF_BASE = 1.2;
 
 	private final Executor ioExecutor;
 	private final EventBus eventBus;
+	private final BackoffFactory backoffFactory;
 
-	public LanTcpPluginFactory(Executor ioExecutor, EventBus eventBus) {
+	public LanTcpPluginFactory(Executor ioExecutor, EventBus eventBus,
+			BackoffFactory backoffFactory) {
 		this.ioExecutor = ioExecutor;
 		this.eventBus = eventBus;
+		this.backoffFactory = backoffFactory;
 	}
 
 	@Override
@@ -44,9 +49,10 @@ public class LanTcpPluginFactory implements DuplexPluginFactory {
 
 	@Override
 	public DuplexPlugin createPlugin(PluginCallback callback) {
-		LanTcpPlugin plugin = new LanTcpPlugin(ioExecutor, callback,
+		Backoff backoff = backoffFactory.createBackoff(MIN_POLLING_INTERVAL,
-				MAX_LATENCY, MAX_IDLE_TIME, POLLING_INTERVAL,
+				MAX_POLLING_INTERVAL, BACKOFF_BASE);
-				CONNECTION_TIMEOUT);
+		LanTcpPlugin plugin =  new LanTcpPlugin(ioExecutor, backoff, callback, MAX_LATENCY,
+				MAX_IDLE_TIME, CONNECTION_TIMEOUT);
 		eventBus.addListener(plugin);
 		return plugin;
 	}

bramble-core/src/main/java/org/briarproject/bramble/plugin/tcp/PortMapperImpl.java

@@ -54,13 +54,11 @@ class PortMapperImpl implements PortMapper {
 				shutdownManager.addShutdownHook(() -> deleteMapping(port));
 			}
 			String externalString = gateway.getExternalIPAddress();
-			if (externalString == null) {
+			if (LOG.isLoggable(INFO))
-				LOG.info("External address not available");
+				LOG.info(
-			} else {
+						"External address " + scrubInetAddress(externalString));
+			if (externalString != null)
 				external = InetAddress.getByName(externalString);
-				if (LOG.isLoggable(INFO))
-					LOG.info("External address " + scrubInetAddress(external));
-			}
 		} catch (IOException | SAXException e) {
 			logException(LOG, WARNING, e);
 		}

bramble-core/src/main/java/org/briarproject/bramble/plugin/tcp/TcpPlugin.java

@@ -2,15 +2,15 @@ package org.briarproject.bramble.plugin.tcp;
 
 import org.briarproject.bramble.PoliteExecutor;
 import org.briarproject.bramble.api.Pair;
-import org.briarproject.bramble.api.data.BdfList;
 import org.briarproject.bramble.api.event.Event;
 import org.briarproject.bramble.api.event.EventListener;
-import org.briarproject.bramble.api.keyagreement.KeyAgreementListener;
 import org.briarproject.bramble.api.lifecycle.IoExecutor;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
+import org.briarproject.bramble.api.plugin.Backoff;
 import org.briarproject.bramble.api.plugin.ConnectionHandler;
+import org.briarproject.bramble.api.plugin.DiscoveryHandler;
 import org.briarproject.bramble.api.plugin.PluginCallback;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
@@ -66,8 +66,9 @@ abstract class TcpPlugin implements DuplexPlugin, EventListener {
 			Pattern.compile("^\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}$");
 
 	protected final Executor ioExecutor, bindExecutor;
+	protected final Backoff backoff;
 	protected final PluginCallback callback;
-	protected final int maxLatency, maxIdleTime, pollingInterval;
+	protected final int maxLatency, maxIdleTime;
 	protected final int connectionTimeout, socketTimeout;
 	protected final AtomicBoolean used = new AtomicBoolean(false);
 	protected final PluginState state = new PluginState();
@@ -76,22 +77,20 @@ abstract class TcpPlugin implements DuplexPlugin, EventListener {
 	 * Returns zero or more socket addresses on which the plugin should listen,
 	 * in order of preference. At most one of the addresses will be bound.
 	 */
-	protected abstract List<InetSocketAddress> getLocalSocketAddresses(
+	protected abstract List<InetSocketAddress> getLocalSocketAddresses();
-			boolean ipv4);
 
 	/**
 	 * Adds the address on which the plugin is listening to the transport
 	 * properties.
 	 */
-	protected abstract void setLocalSocketAddress(InetSocketAddress a,
+	protected abstract void setLocalSocketAddress(InetSocketAddress a);
-			boolean ipv4);
 
 	/**
 	 * Returns zero or more socket addresses for connecting to a contact with
 	 * the given transport properties.
 	 */
 	protected abstract List<InetSocketAddress> getRemoteSocketAddresses(
-			TransportProperties p, boolean ipv4);
+			TransportProperties p);
 
 	/**
 	 * Returns true if connections to the given address can be attempted.
@@ -100,18 +99,13 @@ abstract class TcpPlugin implements DuplexPlugin, EventListener {
 	protected abstract boolean isConnectable(InterfaceAddress local,
 			InetSocketAddress remote);
 
-	/**
+	TcpPlugin(Executor ioExecutor, Backoff backoff, PluginCallback callback,
-	 * Returns true if the plugin is enabled by default.
+			int maxLatency, int maxIdleTime, int connectionTimeout) {
-	 */
-	protected abstract boolean isEnabledByDefault();
-
-	TcpPlugin(Executor ioExecutor, PluginCallback callback, int maxLatency,
-			int maxIdleTime, int pollingInterval, int connectionTimeout) {
 		this.ioExecutor = ioExecutor;
+		this.backoff = backoff;
 		this.callback = callback;
 		this.maxLatency = maxLatency;
 		this.maxIdleTime = maxIdleTime;
-		this.pollingInterval = pollingInterval;
 		this.connectionTimeout = connectionTimeout;
 		if (maxIdleTime > Integer.MAX_VALUE / 2)
 			socketTimeout = Integer.MAX_VALUE;
@@ -134,48 +128,42 @@ abstract class TcpPlugin implements DuplexPlugin, EventListener {
 	public void start() {
 		if (used.getAndSet(true)) throw new IllegalStateException();
 		Settings settings = callback.getSettings();
-		state.setStarted(
+		state.setStarted(settings.getBoolean(PREF_PLUGIN_ENABLE, false));
-				settings.getBoolean(PREF_PLUGIN_ENABLE, isEnabledByDefault()));
 		bind();
 	}
 
 	protected void bind() {
 		bindExecutor.execute(() -> {
 			if (getState() != INACTIVE) return;
-			bind(true);
+			ServerSocket ss = null;
-			bind(false);
+			for (InetSocketAddress addr : getLocalSocketAddresses()) {
-		});
+				try {
-	}
+					ss = new ServerSocket();
-
+					ss.bind(addr);
-	private void bind(boolean ipv4) {
+					break;
-		ServerSocket ss = null;
+				} catch (IOException e) {
-		for (InetSocketAddress addr : getLocalSocketAddresses(ipv4)) {
+					if (LOG.isLoggable(INFO))
-			try {
+						LOG.info("Failed to bind " + scrubSocketAddress(addr));
-				ss = new ServerSocket();
+					tryToClose(ss, LOG, WARNING);
-				ss.bind(addr);
+				}
-				break;
-			} catch (IOException e) {
-				if (LOG.isLoggable(INFO))
-					LOG.info("Failed to bind " + scrubSocketAddress(addr));
-				tryToClose(ss, LOG, WARNING);
 			}
-		}
+			if (ss == null) {
-		if (ss == null) {
+				LOG.info("Could not bind server socket");
-			LOG.info("Could not bind server socket");
+				return;
-			return;
+			}
-		}
+			if (!state.setServerSocket(ss)) {
-		if (!state.setServerSocket(ss, ipv4)) {
+				LOG.info("Closing redundant server socket");
-			LOG.info("Closing redundant server socket");
+				tryToClose(ss, LOG, WARNING);
-			tryToClose(ss, LOG, WARNING);
+				return;
-			return;
+			}
-		}
+			backoff.reset();
-		InetSocketAddress local =
+			InetSocketAddress local =
-				(InetSocketAddress) ss.getLocalSocketAddress();
+					(InetSocketAddress) ss.getLocalSocketAddress();
-		setLocalSocketAddress(local, ipv4);
+			setLocalSocketAddress(local);
-		if (LOG.isLoggable(INFO))
+			if (LOG.isLoggable(INFO))
-			LOG.info("Listening on " + scrubSocketAddress(local));
+				LOG.info("Listening on " + scrubSocketAddress(local));
-		ServerSocket finalSocket = ss;
+			acceptContactConnections(ss);
-		ioExecutor.execute(() -> acceptContactConnections(finalSocket, ipv4));
+		});
 	}
 
 	String getIpPortString(InetSocketAddress a) {
@@ -185,7 +173,7 @@ abstract class TcpPlugin implements DuplexPlugin, EventListener {
 		return addr + ":" + a.getPort();
 	}
 
-	private void acceptContactConnections(ServerSocket ss, boolean ipv4) {
+	private void acceptContactConnections(ServerSocket ss) {
 		while (true) {
 			Socket s;
 			try {
@@ -194,20 +182,21 @@ abstract class TcpPlugin implements DuplexPlugin, EventListener {
 			} catch (IOException e) {
 				// This is expected when the server socket is closed
 				LOG.info("Server socket closed");
-				state.clearServerSocket(ss, ipv4);
+				state.clearServerSocket(ss);
 				return;
 			}
-			if (LOG.isLoggable(INFO)) {
+			if (LOG.isLoggable(INFO))
 				LOG.info("Connection from " +
 						scrubSocketAddress(s.getRemoteSocketAddress()));
-			}
+			backoff.reset();
 			callback.handleConnection(new TcpTransportConnection(this, s));
 		}
 	}
 
 	@Override
 	public void stop() {
-		for (ServerSocket ss : state.setStopped()) tryToClose(ss, LOG, WARNING);
+		ServerSocket ss = state.setStopped();
+		tryToClose(ss, LOG, WARNING);
 	}
 
 	@Override
@@ -227,13 +216,14 @@ abstract class TcpPlugin implements DuplexPlugin, EventListener {
 
 	@Override
 	public int getPollingInterval() {
-		return pollingInterval;
+		return backoff.getPollingInterval();
 	}
 
 	@Override
-	public void poll(Collection<Pair<TransportProperties, ConnectionHandler>>
+	public void poll(
-			properties) {
+			List<Pair<TransportProperties, ConnectionHandler>> properties) {
 		if (getState() != ACTIVE) return;
+		backoff.increment();
 		for (Pair<TransportProperties, ConnectionHandler> p : properties) {
 			connect(p.getFirst(), p.getSecond());
 		}
@@ -242,28 +232,23 @@ abstract class TcpPlugin implements DuplexPlugin, EventListener {
 	private void connect(TransportProperties p, ConnectionHandler h) {
 		ioExecutor.execute(() -> {
 			DuplexTransportConnection d = createConnection(p);
-			if (d != null) h.handleConnection(d);
+			if (d != null) {
+				backoff.reset();
+				h.handleConnection(d);
+			}
 		});
 	}
 
 	@Override
 	public DuplexTransportConnection createConnection(TransportProperties p) {
-		DuplexTransportConnection c = createConnection(p, true);
+		ServerSocket ss = state.getServerSocket();
-		if (c != null) return c;
-		return createConnection(p, false);
-	}
-
-	@Nullable
-	private DuplexTransportConnection createConnection(TransportProperties p,
-			boolean ipv4) {
-		ServerSocket ss = state.getServerSocket(ipv4);
 		if (ss == null) return null;
 		InterfaceAddress local = getLocalInterfaceAddress(ss.getInetAddress());
 		if (local == null) {
 			LOG.warning("No interface for server socket");
 			return null;
 		}
-		for (InetSocketAddress remote : getRemoteSocketAddresses(p, ipv4)) {
+		for (InetSocketAddress remote : getRemoteSocketAddresses(p)) {
 			// Don't try to connect to our own address
 			if (!canConnectToOwnAddress() &&
 					remote.getAddress().equals(ss.getInetAddress())) {
@@ -288,10 +273,9 @@ abstract class TcpPlugin implements DuplexPlugin, EventListener {
 					LOG.info("Connected to " + scrubSocketAddress(remote));
 				return new TcpTransportConnection(this, s);
 			} catch (IOException e) {
-				if (LOG.isLoggable(INFO)) {
+				if (LOG.isLoggable(INFO))
 					LOG.info("Could not connect to " +
 							scrubSocketAddress(remote));
-				}
 			}
 		}
 		return null;
@@ -314,12 +298,8 @@ abstract class TcpPlugin implements DuplexPlugin, EventListener {
 		return new Socket();
 	}
 
-	int chooseEphemeralPort() {
-		return 32768 + (int) (Math.random() * 32768);
-	}
-
 	@Nullable
-	InetSocketAddress parseIpv4SocketAddress(String ipPort) {
+	InetSocketAddress parseSocketAddress(String ipPort) {
 		if (isNullOrEmpty(ipPort)) return null;
 		String[] split = ipPort.split(":");
 		if (split.length != 2) return null;
@@ -330,27 +310,18 @@ abstract class TcpPlugin implements DuplexPlugin, EventListener {
 			InetAddress a = InetAddress.getByName(addr);
 			int p = Integer.parseInt(port);
 			return new InetSocketAddress(a, p);
-		} catch (UnknownHostException | NumberFormatException e) {
+		} catch (UnknownHostException e) {
+			if (LOG.isLoggable(WARNING))
+				// not scrubbing to enable us to find the problem
+				LOG.warning("Invalid address: " + addr);
+			return null;
+		} catch (NumberFormatException e) {
+			if (LOG.isLoggable(WARNING))
+				LOG.warning("Invalid port: " + port);
 			return null;
 		}
 	}
 
-	@Override
-	public boolean supportsKeyAgreement() {
-		return false;
-	}
-
-	@Override
-	public KeyAgreementListener createKeyAgreementListener(byte[] commitment) {
-		throw new UnsupportedOperationException();
-	}
-
-	@Override
-	public DuplexTransportConnection createKeyAgreementConnection(
-			byte[] commitment, BdfList descriptor) {
-		throw new UnsupportedOperationException();
-	}
-
 	@Override
 	public boolean supportsRendezvous() {
 		return false;
@@ -362,6 +333,17 @@ abstract class TcpPlugin implements DuplexPlugin, EventListener {
 		throw new UnsupportedOperationException();
 	}
 
+	@Override
+	public boolean supportsDiscovery() {
+		return false;
+	}
+
+	@Override
+	public void discoverPeers(
+			List<Pair<TransportProperties, DiscoveryHandler>> properties) {
+		throw new UnsupportedOperationException();
+	}
+
 	List<InterfaceAddress> getLocalInterfaceAddresses() {
 		List<InterfaceAddress> addrs = new ArrayList<>();
 		for (NetworkInterface iface : getNetworkInterfaces()) {
@@ -400,15 +382,14 @@ abstract class TcpPlugin implements DuplexPlugin, EventListener {
 
 	@IoExecutor
 	private void onSettingsUpdated(Settings settings) {
-		boolean enabledByUser =
+		boolean enabledByUser = settings.getBoolean(PREF_PLUGIN_ENABLE, false);
-				settings.getBoolean(PREF_PLUGIN_ENABLE, isEnabledByDefault());
+		ServerSocket ss = state.setEnabledByUser(enabledByUser);
-		List<ServerSocket> toClose = state.setEnabledByUser(enabledByUser);
 		State s = getState();
-		if (!toClose.isEmpty()) {
+		if (ss != null) {
-			LOG.info("Disabled by user, closing server sockets");
+			LOG.info("Disabled by user, closing server socket");
-			for (ServerSocket ss : toClose) tryToClose(ss, LOG, WARNING);
+			tryToClose(ss, LOG, WARNING);
 		} else if (s == INACTIVE) {
-			LOG.info("Enabled by user, opening server sockets");
+			LOG.info("Enabled by user, opening server socket");
 			bind();
 		}
 	}
@@ -422,7 +403,7 @@ abstract class TcpPlugin implements DuplexPlugin, EventListener {
 
 		@GuardedBy("this")
 		@Nullable
-		private ServerSocket serverSocketV4 = null, serverSocketV6 = null;
+		private ServerSocket serverSocket = null;
 
 		synchronized void setStarted(boolean enabledByUser) {
 			started = true;
@@ -430,68 +411,48 @@ abstract class TcpPlugin implements DuplexPlugin, EventListener {
 			callback.pluginStateChanged(getState());
 		}
 
-		synchronized List<ServerSocket> setStopped() {
+		@Nullable
+		synchronized ServerSocket setStopped() {
 			stopped = true;
-			List<ServerSocket> toClose = clearServerSockets();
+			ServerSocket ss = serverSocket;
+			serverSocket = null;
 			callback.pluginStateChanged(getState());
-			return toClose;
+			return ss;
-		}
-
-		@GuardedBy("this")
-		private List<ServerSocket> clearServerSockets() {
-			List<ServerSocket> toClose = new ArrayList<>(2);
-			if (serverSocketV4 != null) {
-				toClose.add(serverSocketV4);
-				serverSocketV4 = null;
-			}
-			if (serverSocketV6 != null) {
-				toClose.add(serverSocketV6);
-				serverSocketV6 = null;
-			}
-			return toClose;
-		}
-
-		synchronized List<ServerSocket> setEnabledByUser(
-				boolean enabledByUser) {
-			this.enabledByUser = enabledByUser;
-			List<ServerSocket> toClose = enabledByUser
-					? emptyList() : clearServerSockets();
-			callback.pluginStateChanged(getState());
-			return toClose;
 		}
 
 		@Nullable
-		synchronized ServerSocket getServerSocket(boolean ipv4) {
+		synchronized ServerSocket setEnabledByUser(boolean enabledByUser) {
-			return ipv4 ? serverSocketV4 : serverSocketV6;
+			this.enabledByUser = enabledByUser;
+			ServerSocket ss = null;
+			if (!enabledByUser) {
+				ss = serverSocket;
+				serverSocket = null;
+			}
+			callback.pluginStateChanged(getState());
+			return ss;
 		}
 
-		synchronized boolean setServerSocket(ServerSocket ss, boolean ipv4) {
+		@Nullable
-			if (stopped) return false;
+		synchronized ServerSocket getServerSocket() {
-			if (ipv4) {
+			return serverSocket;
-				if (serverSocketV4 != null) return false;
+		}
-				serverSocketV4 = ss;
+
-			} else {
+		synchronized boolean setServerSocket(ServerSocket ss) {
-				if (serverSocketV6 != null) return false;
+			if (stopped || serverSocket != null) return false;
-				serverSocketV6 = ss;
+			serverSocket = ss;
-			}
 			callback.pluginStateChanged(getState());
 			return true;
 		}
 
-		synchronized void clearServerSocket(ServerSocket ss, boolean ipv4) {
+		synchronized void clearServerSocket(ServerSocket ss) {
-			if (ipv4) {
+			if (serverSocket == ss) serverSocket = null;
-				if (serverSocketV4 == ss) serverSocketV4 = null;
-			} else {
-				if (serverSocketV6 == ss) serverSocketV6 = null;
-			}
 			callback.pluginStateChanged(getState());
 		}
 
 		synchronized State getState() {
 			if (!started || stopped) return STARTING_STOPPING;
 			if (!enabledByUser) return DISABLED;
-			if (serverSocketV4 != null || serverSocketV6 != null) return ACTIVE;
+			return serverSocket == null ? INACTIVE : ACTIVE;
-			return INACTIVE;
 		}
 
 		synchronized int getReasonsDisabled() {

bramble-core/src/main/java/org/briarproject/bramble/plugin/tcp/WanTcpPlugin.java

@@ -1,9 +1,13 @@
 package org.briarproject.bramble.plugin.tcp;
 
+import org.briarproject.bramble.api.data.BdfList;
+import org.briarproject.bramble.api.keyagreement.KeyAgreementListener;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
+import org.briarproject.bramble.api.plugin.Backoff;
 import org.briarproject.bramble.api.plugin.PluginCallback;
 import org.briarproject.bramble.api.plugin.TransportId;
+import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
 import org.briarproject.bramble.api.properties.TransportProperties;
 
 import java.net.Inet4Address;
@@ -16,7 +20,6 @@ import java.util.concurrent.Executor;
 
 import static java.util.Collections.emptyList;
 import static java.util.Collections.singletonList;
-import static org.briarproject.bramble.api.plugin.WanTcpConstants.DEFAULT_PREF_PLUGIN_ENABLE;
 import static org.briarproject.bramble.api.plugin.WanTcpConstants.ID;
 
 @MethodsNotNullByDefault
@@ -29,10 +32,10 @@ class WanTcpPlugin extends TcpPlugin {
 
 	private volatile MappingResult mappingResult;
 
-	WanTcpPlugin(Executor ioExecutor, PortMapper portMapper,
+	WanTcpPlugin(Executor ioExecutor, Backoff backoff, PortMapper portMapper,
 			PluginCallback callback, int maxLatency, int maxIdleTime,
-			int pollingInterval, int connectionTimeout) {
+			int connectionTimeout) {
-		super(ioExecutor, callback, maxLatency, maxIdleTime, pollingInterval,
+		super(ioExecutor, backoff, callback, maxLatency, maxIdleTime,
 				connectionTimeout);
 		this.portMapper = portMapper;
 	}
@@ -43,16 +46,26 @@ class WanTcpPlugin extends TcpPlugin {
 	}
 
 	@Override
-	protected boolean isEnabledByDefault() {
+	public boolean supportsKeyAgreement() {
-		return DEFAULT_PREF_PLUGIN_ENABLE;
+		return false;
 	}
 
 	@Override
-	protected List<InetSocketAddress> getLocalSocketAddresses(boolean ipv4) {
+	public KeyAgreementListener createKeyAgreementListener(byte[] commitment) {
-		if (!ipv4) return emptyList();
+		throw new UnsupportedOperationException();
+	}
+
+	@Override
+	public DuplexTransportConnection createKeyAgreementConnection(
+			byte[] commitment, BdfList descriptor) {
+		throw new UnsupportedOperationException();
+	}
+
+	@Override
+	protected List<InetSocketAddress> getLocalSocketAddresses() {
 		// Use the same address and port as last time if available
 		TransportProperties p = callback.getLocalProperties();
-		InetSocketAddress old = parseIpv4SocketAddress(p.get(PROP_IP_PORT));
+		InetSocketAddress old = parseSocketAddress(p.get(PROP_IP_PORT));
 		List<InetSocketAddress> addrs = new LinkedList<>();
 		for (InetAddress a : getLocalInetAddresses()) {
 			if (isAcceptableAddress(a)) {
@@ -82,11 +95,14 @@ class WanTcpPlugin extends TcpPlugin {
 		return ipv4 && !loop && !link && !site;
 	}
 
+	private int chooseEphemeralPort() {
+		return 32768 + (int) (Math.random() * 32768);
+	}
+
 	@Override
 	protected List<InetSocketAddress> getRemoteSocketAddresses(
-			TransportProperties p, boolean ipv4) {
+			TransportProperties p) {
-		if (!ipv4) return emptyList();
+		InetSocketAddress parsed = parseSocketAddress(p.get(PROP_IP_PORT));
-		InetSocketAddress parsed = parseIpv4SocketAddress(p.get(PROP_IP_PORT));
 		if (parsed == null) return emptyList();
 		return singletonList(parsed);
 	}
@@ -99,8 +115,7 @@ class WanTcpPlugin extends TcpPlugin {
 	}
 
 	@Override
-	protected void setLocalSocketAddress(InetSocketAddress a, boolean ipv4) {
+	protected void setLocalSocketAddress(InetSocketAddress a) {
-		if (!ipv4) throw new AssertionError();
 		if (mappingResult != null && mappingResult.isUsable()) {
 			// Advertise the external address to contacts
 			if (a.equals(mappingResult.getInternal())) {

bramble-core/src/main/java/org/briarproject/bramble/plugin/tcp/WanTcpPluginFactory.java

@@ -3,6 +3,8 @@ package org.briarproject.bramble.plugin.tcp;
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.lifecycle.ShutdownManager;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.Backoff;
+import org.briarproject.bramble.api.plugin.BackoffFactory;
 import org.briarproject.bramble.api.plugin.PluginCallback;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
@@ -12,27 +14,29 @@ import java.util.concurrent.Executor;
 
 import javax.annotation.concurrent.Immutable;
 
-import static java.util.concurrent.TimeUnit.MINUTES;
-import static java.util.concurrent.TimeUnit.SECONDS;
 import static org.briarproject.bramble.api.plugin.WanTcpConstants.ID;
 
 @Immutable
 @NotNullByDefault
 public class WanTcpPluginFactory implements DuplexPluginFactory {
 
-	private static final int MAX_LATENCY = (int) SECONDS.toMillis(30);
+	private static final int MAX_LATENCY = 30_000; // 30 seconds
-	private static final int MAX_IDLE_TIME = (int) SECONDS.toMillis(30);
+	private static final int MAX_IDLE_TIME = 30_000; // 30 seconds
-	private static final int POLLING_INTERVAL = (int) MINUTES.toMillis(1);
+	private static final int CONNECTION_TIMEOUT = 30_000; // 30 seconds
-	private static final int CONNECTION_TIMEOUT = (int) SECONDS.toMillis(30);
+	private static final int MIN_POLLING_INTERVAL = 60_000; // 1 minute
+	private static final int MAX_POLLING_INTERVAL = 600_000; // 10 mins
+	private static final double BACKOFF_BASE = 1.2;
 
 	private final Executor ioExecutor;
 	private final EventBus eventBus;
+	private final BackoffFactory backoffFactory;
 	private final ShutdownManager shutdownManager;
 
 	public WanTcpPluginFactory(Executor ioExecutor, EventBus eventBus,
-			ShutdownManager shutdownManager) {
+			BackoffFactory backoffFactory, ShutdownManager shutdownManager) {
 		this.ioExecutor = ioExecutor;
 		this.eventBus = eventBus;
+		this.backoffFactory = backoffFactory;
 		this.shutdownManager = shutdownManager;
 	}
 
@@ -48,9 +52,11 @@ public class WanTcpPluginFactory implements DuplexPluginFactory {
 
 	@Override
 	public DuplexPlugin createPlugin(PluginCallback callback) {
-		WanTcpPlugin plugin = new WanTcpPlugin(ioExecutor,
+		Backoff backoff = backoffFactory.createBackoff(MIN_POLLING_INTERVAL,
+				MAX_POLLING_INTERVAL, BACKOFF_BASE);
+		WanTcpPlugin plugin = new WanTcpPlugin(ioExecutor, backoff,
 				new PortMapperImpl(shutdownManager), callback, MAX_LATENCY,
-				MAX_IDLE_TIME, POLLING_INTERVAL, CONNECTION_TIMEOUT);
+				MAX_IDLE_TIME, CONNECTION_TIMEOUT);
 		eventBus.addListener(plugin);
 		return plugin;
 	}

bramble-core/src/main/java/org/briarproject/bramble/plugin/tor/TorPlugin.java

@@ -17,7 +17,9 @@ import org.briarproject.bramble.api.network.event.NetworkStatusEvent;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
+import org.briarproject.bramble.api.plugin.Backoff;
 import org.briarproject.bramble.api.plugin.ConnectionHandler;
+import org.briarproject.bramble.api.plugin.DiscoveryHandler;
 import org.briarproject.bramble.api.plugin.PluginCallback;
 import org.briarproject.bramble.api.plugin.PluginException;
 import org.briarproject.bramble.api.plugin.TorConstants;
@@ -45,11 +47,9 @@ import java.net.ServerSocket;
 import java.net.Socket;
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Scanner;
-import java.util.Set;
 import java.util.concurrent.Executor;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.logging.Logger;
@@ -76,13 +76,6 @@ import static org.briarproject.bramble.api.plugin.Plugin.State.ENABLING;
 import static org.briarproject.bramble.api.plugin.Plugin.State.INACTIVE;
 import static org.briarproject.bramble.api.plugin.Plugin.State.STARTING_STOPPING;
 import static org.briarproject.bramble.api.plugin.TorConstants.CONTROL_PORT;
-import static org.briarproject.bramble.api.plugin.TorConstants.DEFAULT_PREF_PLUGIN_ENABLE;
-import static org.briarproject.bramble.api.plugin.TorConstants.DEFAULT_PREF_TOR_MOBILE;
-import static org.briarproject.bramble.api.plugin.TorConstants.DEFAULT_PREF_TOR_NETWORK;
-import static org.briarproject.bramble.api.plugin.TorConstants.DEFAULT_PREF_TOR_ONLY_WHEN_CHARGING;
-import static org.briarproject.bramble.api.plugin.TorConstants.HS_PRIVATE_KEY_V2;
-import static org.briarproject.bramble.api.plugin.TorConstants.HS_PRIVATE_KEY_V3;
-import static org.briarproject.bramble.api.plugin.TorConstants.HS_V3_CREATED;
 import static org.briarproject.bramble.api.plugin.TorConstants.ID;
 import static org.briarproject.bramble.api.plugin.TorConstants.PREF_TOR_MOBILE;
 import static org.briarproject.bramble.api.plugin.TorConstants.PREF_TOR_NETWORK;
@@ -96,7 +89,6 @@ import static org.briarproject.bramble.api.plugin.TorConstants.PROP_ONION_V3;
 import static org.briarproject.bramble.api.plugin.TorConstants.REASON_BATTERY;
 import static org.briarproject.bramble.api.plugin.TorConstants.REASON_COUNTRY_BLOCKED;
 import static org.briarproject.bramble.api.plugin.TorConstants.REASON_MOBILE_DATA;
-import static org.briarproject.bramble.api.plugin.TorConstants.V3_MIGRATION_PERIOD_MS;
 import static org.briarproject.bramble.plugin.tor.TorRendezvousCrypto.SEED_BYTES;
 import static org.briarproject.bramble.util.IoUtils.copyAndClose;
 import static org.briarproject.bramble.util.IoUtils.tryToClose;
@@ -110,59 +102,28 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 
 	private static final Logger LOG = getLogger(TorPlugin.class.getName());
 
-	/**
-	 * Controller events we want to receive.
-	 */
 	private static final String[] EVENTS = {
 			"CIRC", "ORCONN", "HS_DESC", "NOTICE", "WARN", "ERR"
 	};
-
-	/**
-	 * Command-line argument to set our process as Tor's owning controller
-	 * so Tor exits when our process dies.
-	 */
 	private static final String OWNER = "__OwningControllerProcess";
-
-	/**
-	 * How long to wait for the authentication cookie file to be created.
-	 */
 	private static final int COOKIE_TIMEOUT_MS = 3000;
-
-	/**
-	 * How often to check whether the authentication cookie file has been
-	 * created.
-	 */
 	private static final int COOKIE_POLLING_INTERVAL_MS = 200;
-
-	/**
-	 * Regex for matching v2 hidden service names.
-	 */
 	private static final Pattern ONION_V2 = Pattern.compile("[a-z2-7]{16}");
-
-	/**
-	 * Regex for matching v3 hidden service names.
-	 */
 	private static final Pattern ONION_V3 = Pattern.compile("[a-z2-7]{56}");
 
-	/**
-	 * How many copies of our descriptor must be uploaded before we consider
-	 * our hidden service to be reachable and switch to less frequent polling.
-	 */
-	private static final int MIN_DESCRIPTORS_UPLOADED = 5;
-
 	private final Executor ioExecutor, connectionStatusExecutor;
 	private final NetworkManager networkManager;
 	private final LocationUtils locationUtils;
 	private final SocketFactory torSocketFactory;
 	private final Clock clock;
 	private final BatteryManager batteryManager;
+	private final Backoff backoff;
 	private final TorRendezvousCrypto torRendezvousCrypto;
 	private final PluginCallback callback;
 	private final String architecture;
 	private final CircumventionProvider circumventionProvider;
 	private final ResourceProvider resourceProvider;
 	private final int maxLatency, maxIdleTime, socketTimeout;
-	private final int initialPollingInterval, stablePollingInterval;
 	private final File torDirectory, torFile, geoIpFile, obfs4File, configFile;
 	private final File doneFile, cookieFile;
 	private final AtomicBoolean used = new AtomicBoolean(false);
@@ -181,11 +142,10 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			LocationUtils locationUtils, SocketFactory torSocketFactory,
 			Clock clock, ResourceProvider resourceProvider,
 			CircumventionProvider circumventionProvider,
-			BatteryManager batteryManager,
+			BatteryManager batteryManager, Backoff backoff,
 			TorRendezvousCrypto torRendezvousCrypto,
 			PluginCallback callback, String architecture, int maxLatency,
-			int maxIdleTime, int initialPollingInterval,
+			int maxIdleTime, File torDirectory) {
-			int stablePollingInterval, File torDirectory) {
 		this.ioExecutor = ioExecutor;
 		this.networkManager = networkManager;
 		this.locationUtils = locationUtils;
@@ -194,6 +154,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		this.resourceProvider = resourceProvider;
 		this.circumventionProvider = circumventionProvider;
 		this.batteryManager = batteryManager;
+		this.backoff = backoff;
 		this.torRendezvousCrypto = torRendezvousCrypto;
 		this.callback = callback;
 		this.architecture = architecture;
@@ -202,8 +163,6 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		if (maxIdleTime > Integer.MAX_VALUE / 2)
 			socketTimeout = Integer.MAX_VALUE;
 		else socketTimeout = maxIdleTime * 2;
-		this.initialPollingInterval = initialPollingInterval;
-		this.stablePollingInterval = stablePollingInterval;
 		this.torDirectory = torDirectory;
 		torFile = new File(torDirectory, "tor");
 		geoIpFile = new File(torDirectory, "geoip");
@@ -329,12 +288,12 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		bind();
 	}
 
-	// TODO: Remove after a reasonable migration period (added 2020-06-25)
+	// TODO: Remove after a reasonable migration period (added 2020-01-16)
 	private Settings migrateSettings(Settings settings) {
 		int network = settings.getInt(PREF_TOR_NETWORK,
-				DEFAULT_PREF_TOR_NETWORK);
+				PREF_TOR_NETWORK_AUTOMATIC);
 		if (network == PREF_TOR_NETWORK_NEVER) {
-			settings.putInt(PREF_TOR_NETWORK, DEFAULT_PREF_TOR_NETWORK);
+			settings.putInt(PREF_TOR_NETWORK, PREF_TOR_NETWORK_AUTOMATIC);
 			settings.putBoolean(PREF_PLUGIN_ENABLE, false);
 			callback.mergeSettings(settings);
 		}
@@ -468,6 +427,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			callback.mergeSettings(s);
 			// Create a hidden service if necessary
 			ioExecutor.execute(() -> publishHiddenService(localPort));
+			backoff.reset();
 			// Accept incoming hidden service connections from Tor
 			acceptContactConnections(ss);
 		});
@@ -475,66 +435,15 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 
 	private void publishHiddenService(String port) {
 		if (!state.isTorRunning()) return;
-		// TODO: Remove support for v2 hidden services after a reasonable
+		LOG.info("Creating hidden service");
-		// migration period (migration started 2020-06-30)
+		String privKey = settings.get(HS_PRIVKEY);
-		String privKey2 = settings.get(HS_PRIVATE_KEY_V2);
-		String privKey3 = settings.get(HS_PRIVATE_KEY_V3);
-		String v3Created = settings.get(HS_V3_CREATED);
-		// Publish a v2 hidden service if we've already created one, and
-		// either we've never published a v3 hidden service or we're still
-		// in the migration period since first publishing it
-		if (!isNullOrEmpty(privKey2)) {
-			long now = clock.currentTimeMillis();
-			long then = v3Created == null ? now : Long.valueOf(v3Created);
-			if (now - then >= V3_MIGRATION_PERIOD_MS) retireV2HiddenService();
-			else publishV2HiddenService(port, privKey2);
-		}
-		publishV3HiddenService(port, privKey3);
-	}
-
-	private void publishV2HiddenService(String port, String privKey) {
-		LOG.info("Creating v2 hidden service");
-		Map<Integer, String> portLines = singletonMap(80, "127.0.0.1:" + port);
-		Map<String, String> response;
-		try {
-			response = controlConnection.addOnion(privKey, portLines);
-		} catch (IOException e) {
-			logException(LOG, WARNING, e);
-			return;
-		}
-		if (!response.containsKey(HS_ADDRESS)) {
-			LOG.warning("Tor did not return a hidden service address");
-			return;
-		}
-		String onion2 = response.get(HS_ADDRESS);
-		if (LOG.isLoggable(INFO)) {
-			LOG.info("V2 hidden service " + scrubOnion(onion2));
-		}
-		// The hostname has already been published and the private key stored
-	}
-
-	private void retireV2HiddenService() {
-		LOG.info("Retiring v2 hidden service");
-		TransportProperties p = new TransportProperties();
-		p.put(PROP_ONION_V2, "");
-		callback.mergeLocalProperties(p);
-		Settings s = new Settings();
-		s.put(HS_PRIVATE_KEY_V2, "");
-		callback.mergeSettings(s);
-	}
-
-	private void publishV3HiddenService(String port, @Nullable String privKey) {
-		LOG.info("Creating v3 hidden service");
 		Map<Integer, String> portLines = singletonMap(80, "127.0.0.1:" + port);
 		Map<String, String> response;
 		try {
 			// Use the control connection to set up the hidden service
-			if (privKey == null) {
+			if (privKey == null)
-				response = controlConnection.addOnion("NEW:ED25519-V3",
+				response = controlConnection.addOnion(portLines);
-						portLines, null);
+			else response = controlConnection.addOnion(privKey, portLines);
-			} else {
-				response = controlConnection.addOnion(privKey, portLines);
-			}
 		} catch (IOException e) {
 			logException(LOG, WARNING, e);
 			return;
@@ -548,18 +457,16 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			return;
 		}
 		// Publish the hidden service's onion hostname in transport properties
-		String onion3 = response.get(HS_ADDRESS);
+		String onion2 = response.get(HS_ADDRESS);
-		if (LOG.isLoggable(INFO)) {
+		if (LOG.isLoggable(INFO))
-			LOG.info("V3 hidden service " + scrubOnion(onion3));
+			LOG.info("Hidden service " + scrubOnion(onion2));
-		}
 		TransportProperties p = new TransportProperties();
-		p.put(PROP_ONION_V3, onion3);
+		p.put(PROP_ONION_V2, onion2);
 		callback.mergeLocalProperties(p);
 		if (privKey == null) {
 			// Save the hidden service's private key for next time
 			Settings s = new Settings();
-			s.put(HS_PRIVATE_KEY_V3, response.get(HS_PRIVKEY));
+			s.put(HS_PRIVKEY, response.get(HS_PRIVKEY));
-			s.put(HS_V3_CREATED, String.valueOf(clock.currentTimeMillis()));
 			callback.mergeSettings(s);
 		}
 	}
@@ -577,6 +484,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 				return;
 			}
 			LOG.info("Connection received");
+			backoff.reset();
 			callback.handleConnection(new TorTransportConnection(this, s));
 		}
 	}
@@ -638,19 +546,14 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 
 	@Override
 	public int getPollingInterval() {
-		if (state.isDescriptorPublished()) {
+		return backoff.getPollingInterval();
-			LOG.info("Using stable polling interval");
-			return stablePollingInterval;
-		} else {
-			LOG.info("Using initial polling interval");
-			return initialPollingInterval;
-		}
 	}
 
 	@Override
-	public void poll(Collection<Pair<TransportProperties, ConnectionHandler>>
+	public void poll(
-			properties) {
+			List<Pair<TransportProperties, ConnectionHandler>> properties) {
 		if (getState() != ACTIVE) return;
+		backoff.increment();
 		for (Pair<TransportProperties, ConnectionHandler> p : properties) {
 			connect(p.getFirst(), p.getSecond());
 		}
@@ -659,22 +562,22 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	private void connect(TransportProperties p, ConnectionHandler h) {
 		ioExecutor.execute(() -> {
 			DuplexTransportConnection d = createConnection(p);
-			if (d != null) h.handleConnection(d);
+			if (d != null) {
+				backoff.reset();
+				h.handleConnection(d);
+			}
 		});
 	}
 
 	@Override
 	public DuplexTransportConnection createConnection(TransportProperties p) {
 		if (getState() != ACTIVE) return null;
-		// TODO: Remove support for v2 hidden services after a reasonable
+		String bestOnion = null;
-		// migration period (migration started 2020-06-30)
-		String bestOnion = null, version = null;
 		String onion2 = p.get(PROP_ONION_V2);
 		String onion3 = p.get(PROP_ONION_V3);
 		if (!isNullOrEmpty(onion2)) {
 			if (ONION_V2.matcher(onion2).matches()) {
 				bestOnion = onion2;
-				version = "v2";
 			} else {
 				// Don't scrub the address so we can find the problem
 				if (LOG.isLoggable(INFO))
@@ -684,7 +587,6 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		if (!isNullOrEmpty(onion3)) {
 			if (ONION_V3.matcher(onion3).matches()) {
 				bestOnion = onion3;
-				version = "v3";
 			} else {
 				// Don't scrub the address so we can find the problem
 				if (LOG.isLoggable(INFO))
@@ -694,21 +596,17 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		if (bestOnion == null) return null;
 		Socket s = null;
 		try {
-			if (LOG.isLoggable(INFO)) {
+			if (LOG.isLoggable(INFO))
-				LOG.info("Connecting to " + version + " "
+				LOG.info("Connecting to " + scrubOnion(bestOnion));
-						+ scrubOnion(bestOnion));
-			}
 			s = torSocketFactory.createSocket(bestOnion + ".onion", 80);
 			s.setSoTimeout(socketTimeout);
-			if (LOG.isLoggable(INFO)) {
+			if (LOG.isLoggable(INFO))
-				LOG.info("Connected to " + version + " "
+				LOG.info("Connected to " + scrubOnion(bestOnion));
-						+ scrubOnion(bestOnion));
-			}
 			return new TorTransportConnection(this, s);
 		} catch (IOException e) {
 			if (LOG.isLoggable(INFO)) {
-				LOG.info("Could not connect to " + version + " "
+				LOG.info("Could not connect to " + scrubOnion(bestOnion)
-						+ scrubOnion(bestOnion) + ": " + e.toString());
+						+ ": " + e.toString());
 			}
 			tryToClose(s, LOG, WARNING);
 			return null;
@@ -787,10 +685,23 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		}
 	}
 
+	@Override
+	public boolean supportsDiscovery() {
+		return false;
+	}
+
+	@Override
+	public void discoverPeers(
+			List<Pair<TransportProperties, DiscoveryHandler>> properties) {
+		throw new UnsupportedOperationException();
+	}
+
 	@Override
 	public void circuitStatus(String status, String id, String path) {
-		if (status.equals("BUILT") && state.getAndSetCircuitBuilt()) {
+		if (status.equals("BUILT") &&
+				state.getAndSetCircuitBuilt()) {
 			LOG.info("First circuit built");
+			backoff.reset();
 		}
 	}
 
@@ -800,8 +711,8 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 
 	@Override
 	public void orConnStatus(String status, String orName) {
-		if (LOG.isLoggable(INFO)) LOG.info("OR connection " + status);
+		if (LOG.isLoggable(INFO))
-		state.setOrConnectionStatus(orName, status);
+			LOG.info("OR connection " + status + " " + orName);
 		if (status.equals("CLOSED") || status.equals("FAILED")) {
 			// Check whether we've lost connectivity
 			updateConnectionStatus(networkManager.getNetworkStatus(),
@@ -822,20 +733,14 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		if (LOG.isLoggable(INFO)) LOG.info(severity + " " + msg);
 		if (severity.equals("NOTICE") && msg.startsWith("Bootstrapped 100%")) {
 			state.setBootstrapped();
+			backoff.reset();
 		}
 	}
 
 	@Override
 	public void unrecognized(String type, String msg) {
-		if (type.equals("HS_DESC") && msg.startsWith("UPLOADED")) {
+		if (type.equals("HS_DESC") && msg.startsWith("UPLOADED"))
-			String[] words = msg.split(" ");
+			LOG.info("Descriptor uploaded");
-			if (words.length > 1 && ONION_V3.matcher(words[1]).matches()) {
-				LOG.info("V3 descriptor uploaded");
-				state.descriptorUploaded();
-			} else {
-				LOG.info("V2 descriptor uploaded");
-			}
-		}
 	}
 
 	@Override
@@ -881,15 +786,13 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			String country = locationUtils.getCurrentCountry();
 			boolean blocked =
 					circumventionProvider.isTorProbablyBlocked(country);
-			boolean enabledByUser = settings.getBoolean(PREF_PLUGIN_ENABLE,
+			boolean enabledByUser =
-					DEFAULT_PREF_PLUGIN_ENABLE);
+					settings.getBoolean(PREF_PLUGIN_ENABLE, true);
 			int network = settings.getInt(PREF_TOR_NETWORK,
-					DEFAULT_PREF_TOR_NETWORK);
+					PREF_TOR_NETWORK_AUTOMATIC);
-			boolean useMobile = settings.getBoolean(PREF_TOR_MOBILE,
+			boolean useMobile = settings.getBoolean(PREF_TOR_MOBILE, true);
-					DEFAULT_PREF_TOR_MOBILE);
 			boolean onlyWhenCharging =
-					settings.getBoolean(PREF_TOR_ONLY_WHEN_CHARGING,
+					settings.getBoolean(PREF_TOR_ONLY_WHEN_CHARGING, false);
-							DEFAULT_PREF_TOR_ONLY_WHEN_CHARGING);
 			boolean bridgesWork = circumventionProvider.doBridgesWork(country);
 			boolean automatic = network == PREF_TOR_NETWORK_AUTOMATIC;
 
@@ -989,12 +892,6 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		@Nullable
 		private ServerSocket serverSocket = null;
 
-		@GuardedBy("this")
-		private final Set<String> orConnections = new HashSet<>();
-
-		@GuardedBy("this")
-		private int descriptorsUploaded = 0;
-
 		synchronized void setStarted() {
 			started = true;
 			callback.pluginStateChanged(getState());
@@ -1028,10 +925,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		synchronized void enableNetwork(boolean enable) {
 			networkInitialised = true;
 			networkEnabled = enable;
-			if (!enable) {
+			if (!enable) circuitBuilt = false;
-				circuitBuilt = false;
-				descriptorsUploaded = 0;
-			}
 			callback.pluginStateChanged(getState());
 		}
 
@@ -1041,34 +935,6 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			callback.pluginStateChanged(getState());
 		}
 
-		synchronized void setOrConnectionStatus(String orName, String status) {
-			if (status.equals("CONNECTED")) {
-				if (!orConnections.add(orName)) {
-					LOG.warning("Duplicate OR connection");
-				}
-			} else {
-				orConnections.remove(orName);
-				if (orConnections.isEmpty()) descriptorsUploaded = 0;
-			}
-			if (LOG.isLoggable(INFO)) {
-				LOG.info(orConnections.size() + " OR connections");
-			}
-			callback.pluginStateChanged(getState());
-		}
-
-		// Doesn't affect getState()
-		synchronized void descriptorUploaded() {
-			if (networkEnabled && !orConnections.isEmpty()) {
-				descriptorsUploaded++;
-			} else {
-				LOG.warning("Descriptor was uploaded with no OR connection");
-			}
-		}
-
-		synchronized boolean isDescriptorPublished() {
-			return descriptorsUploaded >= MIN_DESCRIPTORS_UPLOADED;
-		}
-
 		// Doesn't affect getState()
 		synchronized boolean setServerSocket(ServerSocket ss) {
 			if (stopped || serverSocket != null) return false;
@@ -1088,8 +954,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			if (reasonsDisabled != 0) return DISABLED;
 			if (!networkInitialised) return ENABLING;
 			if (!networkEnabled) return INACTIVE;
-			return bootstrapped && circuitBuilt && !orConnections.isEmpty()
+			return bootstrapped && circuitBuilt ? ACTIVE : ENABLING;
-					? ACTIVE : ENABLING;
 		}
 
 		synchronized int getReasonsDisabled() {

bramble-core/src/main/java/org/briarproject/bramble/properties/TransportPropertyManagerImpl.java

@@ -30,7 +30,6 @@ import org.briarproject.bramble.api.versioning.ClientVersioningManager;
 import org.briarproject.bramble.api.versioning.ClientVersioningManager.ClientVersioningHook;
 
 import java.util.HashMap;
-import java.util.Iterator;
 import java.util.Map;
 import java.util.Map.Entry;
 
@@ -38,12 +37,6 @@ import javax.annotation.Nullable;
 import javax.annotation.concurrent.Immutable;
 import javax.inject.Inject;
 
-import static org.briarproject.bramble.api.properties.TransportPropertyConstants.GROUP_KEY_DISCOVERED;
-import static org.briarproject.bramble.api.properties.TransportPropertyConstants.MSG_KEY_LOCAL;
-import static org.briarproject.bramble.api.properties.TransportPropertyConstants.MSG_KEY_TRANSPORT_ID;
-import static org.briarproject.bramble.api.properties.TransportPropertyConstants.MSG_KEY_VERSION;
-import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
-
 @Immutable
 @NotNullByDefault
 class TransportPropertyManagerImpl implements TransportPropertyManager,
@@ -118,10 +111,10 @@ class TransportPropertyManagerImpl implements TransportPropertyManager,
 		try {
 			// Find the latest update for this transport, if any
 			BdfDictionary d = metadataParser.parse(meta);
-			TransportId t = new TransportId(d.getString(MSG_KEY_TRANSPORT_ID));
+			TransportId t = new TransportId(d.getString("transportId"));
 			LatestUpdate latest = findLatest(txn, m.getGroupId(), t, false);
 			if (latest != null) {
-				if (d.getLong(MSG_KEY_VERSION) > latest.version) {
+				if (d.getLong("version") > latest.version) {
 					// This update is newer - delete the previous update
 					db.deleteMessage(txn, latest.messageId);
 					db.deleteMessageMetadata(txn, latest.messageId);
@@ -147,27 +140,6 @@ class TransportPropertyManagerImpl implements TransportPropertyManager,
 		}
 	}
 
-	@Override
-	public void addRemotePropertiesFromConnection(ContactId c, TransportId t,
-			TransportProperties props) throws DbException {
-		if (props.isEmpty()) return;
-		try {
-			db.transaction(false, txn -> {
-				Group g = getContactGroup(db.getContact(txn, c));
-				BdfDictionary meta = clientHelper.getGroupMetadataAsDictionary(
-						txn, g.getId());
-				BdfDictionary discovered =
-						meta.getOptionalDictionary(GROUP_KEY_DISCOVERED);
-				if (discovered == null) discovered = new BdfDictionary();
-				discovered.putAll(props);
-				meta.put(GROUP_KEY_DISCOVERED, discovered);
-				clientHelper.mergeGroupMetadata(txn, g.getId(), meta);
-			});
-		} catch (FormatException e) {
-			throw new DbException(e);
-		}
-	}
-
 	@Override
 	public Map<TransportId, TransportProperties> getLocalProperties()
 			throws DbException {
@@ -231,26 +203,12 @@ class TransportPropertyManagerImpl implements TransportPropertyManager,
 		Group g = getContactGroup(c);
 		try {
 			// Find the latest remote update
-			TransportProperties remote;
 			LatestUpdate latest = findLatest(txn, g.getId(), t, false);
-			if (latest == null) {
+			if (latest == null) return new TransportProperties();
-				remote = new TransportProperties();
+			// Retrieve and parse the latest remote properties
-			} else {
+			BdfList message =
-				// Retrieve and parse the latest remote properties
+					clientHelper.getMessageAsList(txn, latest.messageId);
-				BdfList message =
+			return parseProperties(message);
-						clientHelper.getMessageAsList(txn, latest.messageId);
-				remote = parseProperties(message);
-			}
-			// Merge in any discovered properties
-			BdfDictionary meta =
-					clientHelper.getGroupMetadataAsDictionary(txn, g.getId());
-			BdfDictionary d = meta.getOptionalDictionary(GROUP_KEY_DISCOVERED);
-			if (d == null) return remote;
-			TransportProperties merged =
-					clientHelper.parseAndValidateTransportProperties(d);
-			// Received properties override discovered properties
-			merged.putAll(remote);
-			return merged;
 		} catch (FormatException e) {
 			throw new DbException(e);
 		}
@@ -274,22 +232,14 @@ class TransportPropertyManagerImpl implements TransportPropertyManager,
 				LatestUpdate latest = findLatest(txn, localGroup.getId(), t,
 						true);
 				if (latest == null) {
-					merged = new TransportProperties(p);
+					merged = p;
-					Iterator<String> it = merged.values().iterator();
-					while (it.hasNext()) {
-						if (isNullOrEmpty(it.next())) it.remove();
-					}
 					changed = true;
 				} else {
 					BdfList message = clientHelper.getMessageAsList(txn,
 							latest.messageId);
 					TransportProperties old = parseProperties(message);
 					merged = new TransportProperties(old);
-					for (Entry<String, String> e : p.entrySet()) {
+					merged.putAll(p);
-						String key = e.getKey(), value = e.getValue();
-						if (isNullOrEmpty(value)) merged.remove(key);
-						else merged.put(key, value);
-					}
 					changed = !merged.equals(old);
 				}
 				if (changed) {
@@ -331,9 +281,9 @@ class TransportPropertyManagerImpl implements TransportPropertyManager,
 			long now = clock.currentTimeMillis();
 			Message m = clientHelper.createMessage(g, now, body);
 			BdfDictionary meta = new BdfDictionary();
-			meta.put(MSG_KEY_TRANSPORT_ID, t.getString());
+			meta.put("transportId", t.getString());
-			meta.put(MSG_KEY_VERSION, version);
+			meta.put("version", version);
-			meta.put(MSG_KEY_LOCAL, local);
+			meta.put("local", local);
 			clientHelper.addLocalMessage(txn, m, meta, shared, false);
 		} catch (FormatException e) {
 			throw new RuntimeException(e);
@@ -352,9 +302,8 @@ class TransportPropertyManagerImpl implements TransportPropertyManager,
 				.getMessageMetadataAsDictionary(txn, localGroup.getId());
 		for (Entry<MessageId, BdfDictionary> e : metadata.entrySet()) {
 			BdfDictionary meta = e.getValue();
-			TransportId t =
+			TransportId t = new TransportId(meta.getString("transportId"));
-					new TransportId(meta.getString(MSG_KEY_TRANSPORT_ID));
+			long version = meta.getLong("version");
-			long version = meta.getLong(MSG_KEY_VERSION);
 			latestUpdates.put(t, new LatestUpdate(e.getKey(), version));
 		}
 		return latestUpdates;
@@ -367,10 +316,9 @@ class TransportPropertyManagerImpl implements TransportPropertyManager,
 				clientHelper.getMessageMetadataAsDictionary(txn, g);
 		for (Entry<MessageId, BdfDictionary> e : metadata.entrySet()) {
 			BdfDictionary meta = e.getValue();
-			if (meta.getString(MSG_KEY_TRANSPORT_ID).equals(t.getString())
+			if (meta.getString("transportId").equals(t.getString())
-					&& meta.getBoolean(MSG_KEY_LOCAL) == local) {
+					&& meta.getBoolean("local") == local) {
-				return new LatestUpdate(e.getKey(),
+				return new LatestUpdate(e.getKey(), meta.getLong("version"));
-						meta.getLong(MSG_KEY_VERSION));
 			}
 		}
 		return null;

bramble-core/src/main/java/org/briarproject/bramble/rendezvous/RendezvousPollerImpl.java

@@ -2,7 +2,6 @@ package org.briarproject.bramble.rendezvous;
 
 import org.briarproject.bramble.PoliteExecutor;
 import org.briarproject.bramble.api.Pair;
-import org.briarproject.bramble.api.connection.ConnectionManager;
 import org.briarproject.bramble.api.contact.PendingContact;
 import org.briarproject.bramble.api.contact.PendingContactId;
 import org.briarproject.bramble.api.contact.PendingContactState;
@@ -24,6 +23,7 @@ import org.briarproject.bramble.api.lifecycle.Service;
 import org.briarproject.bramble.api.lifecycle.ServiceException;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.ConnectionHandler;
+import org.briarproject.bramble.api.plugin.ConnectionManager;
 import org.briarproject.bramble.api.plugin.Plugin;
 import org.briarproject.bramble.api.plugin.PluginManager;
 import org.briarproject.bramble.api.plugin.TransportConnectionReader;

bramble-core/src/main/java/org/briarproject/bramble/sync/DuplexOutgoingSession.java

@@ -11,17 +11,13 @@ import org.briarproject.bramble.api.event.EventListener;
 import org.briarproject.bramble.api.lifecycle.IoExecutor;
 import org.briarproject.bramble.api.lifecycle.event.LifecycleEvent;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.plugin.TransportId;
-import org.briarproject.bramble.api.plugin.event.TransportInactiveEvent;
 import org.briarproject.bramble.api.sync.Ack;
 import org.briarproject.bramble.api.sync.Message;
 import org.briarproject.bramble.api.sync.Offer;
-import org.briarproject.bramble.api.sync.Priority;
 import org.briarproject.bramble.api.sync.Request;
 import org.briarproject.bramble.api.sync.SyncRecordWriter;
 import org.briarproject.bramble.api.sync.SyncSession;
 import org.briarproject.bramble.api.sync.Versions;
-import org.briarproject.bramble.api.sync.event.CloseSyncConnectionsEvent;
 import org.briarproject.bramble.api.sync.event.GroupVisibilityUpdatedEvent;
 import org.briarproject.bramble.api.sync.event.MessageRequestedEvent;
 import org.briarproject.bramble.api.sync.event.MessageSharedEvent;
@@ -39,7 +35,6 @@ import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicLong;
 import java.util.logging.Logger;
 
-import javax.annotation.Nullable;
 import javax.annotation.concurrent.ThreadSafe;
 
 import static java.util.concurrent.TimeUnit.MILLISECONDS;
@@ -76,12 +71,9 @@ class DuplexOutgoingSession implements SyncSession, EventListener {
 	private final EventBus eventBus;
 	private final Clock clock;
 	private final ContactId contactId;
-	private final TransportId transportId;
 	private final int maxLatency, maxIdleTime;
 	private final StreamWriter streamWriter;
 	private final SyncRecordWriter recordWriter;
-	@Nullable
-	private final Priority priority;
 	private final BlockingQueue<ThrowingRunnable<IOException>> writerTasks;
 
 	private final AtomicBoolean generateAckQueued = new AtomicBoolean(false);
@@ -94,21 +86,18 @@ class DuplexOutgoingSession implements SyncSession, EventListener {
 	private volatile boolean interrupted = false;
 
 	DuplexOutgoingSession(DatabaseComponent db, Executor dbExecutor,
-			EventBus eventBus, Clock clock, ContactId contactId,
+			EventBus eventBus, Clock clock, ContactId contactId, int maxLatency,
-			TransportId transportId, int maxLatency, int maxIdleTime,
+			int maxIdleTime, StreamWriter streamWriter,
-			StreamWriter streamWriter, SyncRecordWriter recordWriter,
+			SyncRecordWriter recordWriter) {
-			@Nullable Priority priority) {
 		this.db = db;
 		this.dbExecutor = dbExecutor;
 		this.eventBus = eventBus;
 		this.clock = clock;
 		this.contactId = contactId;
-		this.transportId = transportId;
 		this.maxLatency = maxLatency;
 		this.maxIdleTime = maxIdleTime;
 		this.streamWriter = streamWriter;
 		this.recordWriter = recordWriter;
-		this.priority = priority;
 		writerTasks = new LinkedBlockingQueue<>();
 	}
 
@@ -119,8 +108,6 @@ class DuplexOutgoingSession implements SyncSession, EventListener {
 		try {
 			// Send our supported protocol versions
 			recordWriter.writeVersions(new Versions(SUPPORTED_VERSIONS));
-			// Send our connection priority, if this is an outgoing connection
-			if (priority != null) recordWriter.writePriority(priority);
 			// Start a query for each type of record
 			generateAck();
 			generateBatch();
@@ -236,12 +223,6 @@ class DuplexOutgoingSession implements SyncSession, EventListener {
 		} else if (e instanceof LifecycleEvent) {
 			LifecycleEvent l = (LifecycleEvent) e;
 			if (l.getLifecycleState() == STOPPING) interrupt();
-		} else if (e instanceof CloseSyncConnectionsEvent) {
-			CloseSyncConnectionsEvent c = (CloseSyncConnectionsEvent) e;
-			if (c.getTransportId().equals(transportId)) interrupt();
-		} else if (e instanceof TransportInactiveEvent) {
-			TransportInactiveEvent t = (TransportInactiveEvent) e;
-			if (t.getTransportId().equals(transportId)) interrupt();
 		}
 	}
 

bramble-core/src/main/java/org/briarproject/bramble/sync/IncomingSession.java

@@ -15,8 +15,6 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.Ack;
 import org.briarproject.bramble.api.sync.Message;
 import org.briarproject.bramble.api.sync.Offer;
-import org.briarproject.bramble.api.sync.Priority;
-import org.briarproject.bramble.api.sync.PriorityHandler;
 import org.briarproject.bramble.api.sync.Request;
 import org.briarproject.bramble.api.sync.SyncRecordReader;
 import org.briarproject.bramble.api.sync.SyncSession;
@@ -49,19 +47,17 @@ class IncomingSession implements SyncSession, EventListener {
 	private final EventBus eventBus;
 	private final ContactId contactId;
 	private final SyncRecordReader recordReader;
-	private final PriorityHandler priorityHandler;
 
 	private volatile boolean interrupted = false;
 
 	IncomingSession(DatabaseComponent db, Executor dbExecutor,
 			EventBus eventBus, ContactId contactId,
-			SyncRecordReader recordReader, PriorityHandler priorityHandler) {
+			SyncRecordReader recordReader) {
 		this.db = db;
 		this.dbExecutor = dbExecutor;
 		this.eventBus = eventBus;
 		this.contactId = contactId;
 		this.recordReader = recordReader;
-		this.priorityHandler = priorityHandler;
 	}
 
 	@IoExecutor
@@ -90,9 +86,6 @@ class IncomingSession implements SyncSession, EventListener {
 				} else if (recordReader.hasVersions()) {
 					Versions v = recordReader.readVersions();
 					dbExecutor.execute(new ReceiveVersions(v));
-				} else if (recordReader.hasPriority()) {
-					Priority p = recordReader.readPriority();
-					priorityHandler.handle(p);
 				} else {
 					// unknown records are ignored in RecordReader#eof()
 					throw new FormatException();

bramble-core/src/main/java/org/briarproject/bramble/sync/SimplexOutgoingSession.java

@@ -11,14 +11,11 @@ import org.briarproject.bramble.api.event.EventListener;
 import org.briarproject.bramble.api.lifecycle.IoExecutor;
 import org.briarproject.bramble.api.lifecycle.event.LifecycleEvent;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.plugin.TransportId;
-import org.briarproject.bramble.api.plugin.event.TransportInactiveEvent;
 import org.briarproject.bramble.api.sync.Ack;
 import org.briarproject.bramble.api.sync.Message;
 import org.briarproject.bramble.api.sync.SyncRecordWriter;
 import org.briarproject.bramble.api.sync.SyncSession;
 import org.briarproject.bramble.api.sync.Versions;
-import org.briarproject.bramble.api.sync.event.CloseSyncConnectionsEvent;
 import org.briarproject.bramble.api.transport.StreamWriter;
 
 import java.io.IOException;
@@ -59,7 +56,6 @@ class SimplexOutgoingSession implements SyncSession, EventListener {
 	private final Executor dbExecutor;
 	private final EventBus eventBus;
 	private final ContactId contactId;
-	private final TransportId transportId;
 	private final int maxLatency;
 	private final StreamWriter streamWriter;
 	private final SyncRecordWriter recordWriter;
@@ -69,14 +65,12 @@ class SimplexOutgoingSession implements SyncSession, EventListener {
 	private volatile boolean interrupted = false;
 
 	SimplexOutgoingSession(DatabaseComponent db, Executor dbExecutor,
-			EventBus eventBus, ContactId contactId, TransportId transportId,
+			EventBus eventBus, ContactId contactId, int maxLatency,
-			int maxLatency, StreamWriter streamWriter,
+			StreamWriter streamWriter, SyncRecordWriter recordWriter) {
-			SyncRecordWriter recordWriter) {
 		this.db = db;
 		this.dbExecutor = dbExecutor;
 		this.eventBus = eventBus;
 		this.contactId = contactId;
-		this.transportId = transportId;
 		this.maxLatency = maxLatency;
 		this.streamWriter = streamWriter;
 		this.recordWriter = recordWriter;
@@ -129,12 +123,6 @@ class SimplexOutgoingSession implements SyncSession, EventListener {
 		} else if (e instanceof LifecycleEvent) {
 			LifecycleEvent l = (LifecycleEvent) e;
 			if (l.getLifecycleState() == STOPPING) interrupt();
-		} else if (e instanceof CloseSyncConnectionsEvent) {
-			CloseSyncConnectionsEvent c = (CloseSyncConnectionsEvent) e;
-			if (c.getTransportId().equals(transportId)) interrupt();
-		} else if (e instanceof TransportInactiveEvent) {
-			TransportInactiveEvent t = (TransportInactiveEvent) e;
-			if (t.getTransportId().equals(transportId)) interrupt();
 		}
 	}
 

bramble-core/src/main/java/org/briarproject/bramble/sync/SyncRecordReaderImpl.java

@@ -11,7 +11,6 @@ import org.briarproject.bramble.api.sync.Message;
 import org.briarproject.bramble.api.sync.MessageFactory;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.bramble.api.sync.Offer;
-import org.briarproject.bramble.api.sync.Priority;
 import org.briarproject.bramble.api.sync.Request;
 import org.briarproject.bramble.api.sync.SyncRecordReader;
 import org.briarproject.bramble.api.sync.Versions;
@@ -27,12 +26,10 @@ import javax.annotation.concurrent.NotThreadSafe;
 import static org.briarproject.bramble.api.sync.RecordTypes.ACK;
 import static org.briarproject.bramble.api.sync.RecordTypes.MESSAGE;
 import static org.briarproject.bramble.api.sync.RecordTypes.OFFER;
-import static org.briarproject.bramble.api.sync.RecordTypes.PRIORITY;
 import static org.briarproject.bramble.api.sync.RecordTypes.REQUEST;
 import static org.briarproject.bramble.api.sync.RecordTypes.VERSIONS;
 import static org.briarproject.bramble.api.sync.SyncConstants.MAX_SUPPORTED_VERSIONS;
 import static org.briarproject.bramble.api.sync.SyncConstants.MESSAGE_HEADER_LENGTH;
-import static org.briarproject.bramble.api.sync.SyncConstants.PRIORITY_NONCE_BYTES;
 import static org.briarproject.bramble.api.sync.SyncConstants.PROTOCOL_VERSION;
 
 @NotThreadSafe
@@ -51,7 +48,7 @@ class SyncRecordReaderImpl implements SyncRecordReader {
 
 	private static boolean isKnownRecordType(byte type) {
 		return type == ACK || type == MESSAGE || type == OFFER ||
-				type == REQUEST || type == VERSIONS || type == PRIORITY;
+				type == REQUEST || type == VERSIONS;
 	}
 
 	private final MessageFactory messageFactory;
@@ -177,23 +174,4 @@ class SyncRecordReaderImpl implements SyncRecordReader {
 		nextRecord = null;
 		return supported;
 	}
-
-	@Override
-	public boolean hasPriority() throws IOException {
-		return !eof() && getNextRecordType() == PRIORITY;
-	}
-
-	@Override
-	public Priority readPriority() throws IOException {
-		if (!hasPriority()) throw new FormatException();
-		return new Priority(readNonce());
-	}
-
-	private byte[] readNonce() throws IOException {
-		if (nextRecord == null) throw new AssertionError();
-		byte[] payload = nextRecord.getPayload();
-		if (payload.length != PRIORITY_NONCE_BYTES) throw new FormatException();
-		nextRecord = null;
-		return payload;
-	}
 }

bramble-core/src/main/java/org/briarproject/bramble/sync/SyncRecordWriterImpl.java

@@ -8,7 +8,6 @@ import org.briarproject.bramble.api.sync.Message;
 import org.briarproject.bramble.api.sync.MessageFactory;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.bramble.api.sync.Offer;
-import org.briarproject.bramble.api.sync.Priority;
 import org.briarproject.bramble.api.sync.Request;
 import org.briarproject.bramble.api.sync.SyncRecordWriter;
 import org.briarproject.bramble.api.sync.Versions;
@@ -21,7 +20,6 @@ import javax.annotation.concurrent.NotThreadSafe;
 import static org.briarproject.bramble.api.sync.RecordTypes.ACK;
 import static org.briarproject.bramble.api.sync.RecordTypes.MESSAGE;
 import static org.briarproject.bramble.api.sync.RecordTypes.OFFER;
-import static org.briarproject.bramble.api.sync.RecordTypes.PRIORITY;
 import static org.briarproject.bramble.api.sync.RecordTypes.REQUEST;
 import static org.briarproject.bramble.api.sync.RecordTypes.VERSIONS;
 import static org.briarproject.bramble.api.sync.SyncConstants.PROTOCOL_VERSION;
@@ -75,12 +73,6 @@ class SyncRecordWriterImpl implements SyncRecordWriter {
 		writeRecord(VERSIONS);
 	}
 
-	@Override
-	public void writePriority(Priority p) throws IOException {
-		writer.writeRecord(
-				new Record(PROTOCOL_VERSION, PRIORITY, p.getNonce()));
-	}
-
 	@Override
 	public void flush() throws IOException {
 		writer.flush();

bramble-core/src/main/java/org/briarproject/bramble/sync/SyncSessionFactoryImpl.java

@@ -5,9 +5,6 @@ import org.briarproject.bramble.api.db.DatabaseComponent;
 import org.briarproject.bramble.api.db.DatabaseExecutor;
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.plugin.TransportId;
-import org.briarproject.bramble.api.sync.Priority;
-import org.briarproject.bramble.api.sync.PriorityHandler;
 import org.briarproject.bramble.api.sync.SyncRecordReader;
 import org.briarproject.bramble.api.sync.SyncRecordReaderFactory;
 import org.briarproject.bramble.api.sync.SyncRecordWriter;
@@ -21,7 +18,6 @@ import java.io.InputStream;
 import java.io.OutputStream;
 import java.util.concurrent.Executor;
 
-import javax.annotation.Nullable;
 import javax.annotation.concurrent.Immutable;
 import javax.inject.Inject;
 
@@ -50,32 +46,29 @@ class SyncSessionFactoryImpl implements SyncSessionFactory {
 	}
 
 	@Override
-	public SyncSession createIncomingSession(ContactId c, InputStream in,
+	public SyncSession createIncomingSession(ContactId c, InputStream in) {
-			PriorityHandler handler) {
 		SyncRecordReader recordReader =
 				recordReaderFactory.createRecordReader(in);
-		return new IncomingSession(db, dbExecutor, eventBus, c, recordReader,
+		return new IncomingSession(db, dbExecutor, eventBus, c, recordReader);
-				handler);
 	}
 
 	@Override
-	public SyncSession createSimplexOutgoingSession(ContactId c, TransportId t,
+	public SyncSession createSimplexOutgoingSession(ContactId c,
 			int maxLatency, StreamWriter streamWriter) {
 		OutputStream out = streamWriter.getOutputStream();
 		SyncRecordWriter recordWriter =
 				recordWriterFactory.createRecordWriter(out);
-		return new SimplexOutgoingSession(db, dbExecutor, eventBus, c, t,
+		return new SimplexOutgoingSession(db, dbExecutor, eventBus, c,
 				maxLatency, streamWriter, recordWriter);
 	}
 
 	@Override
-	public SyncSession createDuplexOutgoingSession(ContactId c, TransportId t,
+	public SyncSession createDuplexOutgoingSession(ContactId c, int maxLatency,
-			int maxLatency, int maxIdleTime, StreamWriter streamWriter,
+			int maxIdleTime, StreamWriter streamWriter) {
-			@Nullable Priority priority) {
 		OutputStream out = streamWriter.getOutputStream();
 		SyncRecordWriter recordWriter =
 				recordWriterFactory.createRecordWriter(out);
-		return new DuplexOutgoingSession(db, dbExecutor, eventBus, clock, c, t,
+		return new DuplexOutgoingSession(db, dbExecutor, eventBus, clock, c,
-				maxLatency, maxIdleTime, streamWriter, recordWriter, priority);
+				maxLatency, maxIdleTime, streamWriter, recordWriter);
 	}
 }

bramble-core/src/test/java/org/briarproject/bramble/account/AccountManagerImplTest.java

@@ -1,7 +1,6 @@
 package org.briarproject.bramble.account;
 
 import org.briarproject.bramble.api.crypto.CryptoComponent;
-import org.briarproject.bramble.api.crypto.DecryptionException;
 import org.briarproject.bramble.api.crypto.KeyStrengthener;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.db.DatabaseConfig;
@@ -20,15 +19,12 @@ import java.io.FileInputStream;
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.InputStreamReader;
-import java.nio.charset.Charset;
 
 import javax.annotation.Nullable;
 
 import static junit.framework.Assert.assertFalse;
 import static junit.framework.Assert.assertNull;
 import static junit.framework.Assert.assertTrue;
-import static org.briarproject.bramble.api.crypto.DecryptionResult.INVALID_CIPHERTEXT;
-import static org.briarproject.bramble.api.crypto.DecryptionResult.INVALID_PASSWORD;
 import static org.briarproject.bramble.test.TestUtils.deleteTestDirectory;
 import static org.briarproject.bramble.test.TestUtils.getIdentity;
 import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
@@ -39,7 +35,6 @@ import static org.briarproject.bramble.util.StringUtils.toHexString;
 import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
-import static org.junit.Assert.fail;
 
 public class AccountManagerImplTest extends BrambleMockTestCase {
 
@@ -88,13 +83,8 @@ public class AccountManagerImplTest extends BrambleMockTestCase {
 	}
 
 	@Test
-	public void testSignInThrowsExceptionIfDbKeyCannotBeLoaded() {
+	public void testSignInReturnsFalseIfDbKeyCannotBeLoaded() {
-		try {
+		assertFalse(accountManager.signIn(password));
-			accountManager.signIn(password);
-			fail();
-		} catch (DecryptionException expected) {
-			assertEquals(INVALID_CIPHERTEXT, expected.getDecryptionResult());
-		}
 		assertFalse(accountManager.hasDatabaseKey());
 
 		assertFalse(keyFile.exists());
@@ -102,11 +92,11 @@ public class AccountManagerImplTest extends BrambleMockTestCase {
 	}
 
 	@Test
-	public void testSignInThrowsExceptionIfPasswordIsWrong() throws Exception {
+	public void testSignInReturnsFalseIfPasswordIsWrong() throws Exception {
 		context.checking(new Expectations() {{
 			oneOf(crypto).decryptWithPassword(encryptedKey, password,
 					keyStrengthener);
-			will(throwException(new DecryptionException(INVALID_PASSWORD)));
+			will(returnValue(null));
 		}});
 
 		storeDatabaseKey(keyFile, encryptedKeyHex);
@@ -115,12 +105,7 @@ public class AccountManagerImplTest extends BrambleMockTestCase {
 		assertEquals(encryptedKeyHex, loadDatabaseKey(keyFile));
 		assertEquals(encryptedKeyHex, loadDatabaseKey(keyBackupFile));
 
-		try {
+		assertFalse(accountManager.signIn(password));
-			accountManager.signIn(password);
-			fail();
-		} catch (DecryptionException expected) {
-			assertEquals(INVALID_PASSWORD, expected.getDecryptionResult());
-		}
 		assertFalse(accountManager.hasDatabaseKey());
 
 		assertEquals(encryptedKeyHex, loadDatabaseKey(keyFile));
@@ -143,7 +128,7 @@ public class AccountManagerImplTest extends BrambleMockTestCase {
 		assertEquals(encryptedKeyHex, loadDatabaseKey(keyFile));
 		assertEquals(encryptedKeyHex, loadDatabaseKey(keyBackupFile));
 
-		accountManager.signIn(password);
+		assertTrue(accountManager.signIn(password));
 		assertTrue(accountManager.hasDatabaseKey());
 		SecretKey decrypted = accountManager.getDatabaseKey();
 		assertNotNull(decrypted);
@@ -172,7 +157,7 @@ public class AccountManagerImplTest extends BrambleMockTestCase {
 		assertEquals(encryptedKeyHex, loadDatabaseKey(keyFile));
 		assertEquals(encryptedKeyHex, loadDatabaseKey(keyBackupFile));
 
-		accountManager.signIn(password);
+		assertTrue(accountManager.signIn(password));
 		assertTrue(accountManager.hasDatabaseKey());
 		SecretKey decrypted = accountManager.getDatabaseKey();
 		assertNotNull(decrypted);
@@ -254,6 +239,55 @@ public class AccountManagerImplTest extends BrambleMockTestCase {
 		assertFalse(keyBackupFile.exists());
 	}
 
+	@Test
+	public void testAccountExistsReturnsFalseIfDbDirectoryDoesNotExist()
+			throws Exception {
+		storeDatabaseKey(keyFile, encryptedKeyHex);
+		storeDatabaseKey(keyBackupFile, encryptedKeyHex);
+
+		assertFalse(dbDir.exists());
+
+		assertFalse(accountManager.accountExists());
+
+		assertEquals(encryptedKeyHex, loadDatabaseKey(keyFile));
+		assertEquals(encryptedKeyHex, loadDatabaseKey(keyBackupFile));
+		assertFalse(dbDir.exists());
+	}
+
+	@Test
+	public void testAccountExistsReturnsFalseIfDbDirectoryIsNotDirectory()
+			throws Exception {
+		storeDatabaseKey(keyFile, encryptedKeyHex);
+		storeDatabaseKey(keyBackupFile, encryptedKeyHex);
+
+		assertTrue(dbDir.createNewFile());
+		assertFalse(dbDir.isDirectory());
+
+		assertFalse(accountManager.accountExists());
+
+		assertEquals(encryptedKeyHex, loadDatabaseKey(keyFile));
+		assertEquals(encryptedKeyHex, loadDatabaseKey(keyBackupFile));
+		assertTrue(dbDir.exists());
+		assertFalse(dbDir.isDirectory());
+	}
+
+	@Test
+	public void testAccountExistsReturnsTrueIfDbDirectoryIsDirectory()
+			throws Exception {
+		storeDatabaseKey(keyFile, encryptedKeyHex);
+		storeDatabaseKey(keyBackupFile, encryptedKeyHex);
+
+		assertTrue(dbDir.mkdirs());
+		assertTrue(dbDir.isDirectory());
+
+		assertTrue(accountManager.accountExists());
+
+		assertEquals(encryptedKeyHex, loadDatabaseKey(keyFile));
+		assertEquals(encryptedKeyHex, loadDatabaseKey(keyBackupFile));
+		assertTrue(dbDir.exists());
+		assertTrue(dbDir.isDirectory());
+	}
+
 	@Test
 	public void testCreateAccountStoresDbKey() throws Exception {
 		context.checking(new Expectations() {{
@@ -281,36 +315,26 @@ public class AccountManagerImplTest extends BrambleMockTestCase {
 	}
 
 	@Test
-	public void testChangePasswordThrowsExceptionIfDbKeyCannotBeLoaded() {
+	public void testChangePasswordReturnsFalseIfDbKeyCannotBeLoaded() {
-		try {
+		assertFalse(accountManager.changePassword(password, newPassword));
-			accountManager.changePassword(password, newPassword);
-			fail();
-		} catch (DecryptionException expected) {
-			assertEquals(INVALID_CIPHERTEXT, expected.getDecryptionResult());
-		}
 
 		assertFalse(keyFile.exists());
 		assertFalse(keyBackupFile.exists());
 	}
 
 	@Test
-	public void testChangePasswordThrowsExceptionIfPasswordIsWrong()
+	public void testChangePasswordReturnsFalseIfPasswordIsWrong()
 			throws Exception {
 		context.checking(new Expectations() {{
 			oneOf(crypto).decryptWithPassword(encryptedKey, password,
 					keyStrengthener);
-			will(throwException(new DecryptionException(INVALID_PASSWORD)));
+			will(returnValue(null));
 		}});
 
 		storeDatabaseKey(keyFile, encryptedKeyHex);
 		storeDatabaseKey(keyBackupFile, encryptedKeyHex);
 
-		try {
+		assertFalse(accountManager.changePassword(password, newPassword));
-			accountManager.changePassword(password, newPassword);
-			fail();
-		} catch (DecryptionException expected) {
-			assertEquals(INVALID_PASSWORD, expected.getDecryptionResult());
-		}
 
 		assertEquals(encryptedKeyHex, loadDatabaseKey(keyFile));
 		assertEquals(encryptedKeyHex, loadDatabaseKey(keyBackupFile));
@@ -333,7 +357,7 @@ public class AccountManagerImplTest extends BrambleMockTestCase {
 		storeDatabaseKey(keyFile, encryptedKeyHex);
 		storeDatabaseKey(keyBackupFile, encryptedKeyHex);
 
-		accountManager.changePassword(password, newPassword);
+		assertTrue(accountManager.changePassword(password, newPassword));
 
 		assertEquals(newEncryptedKeyHex, loadDatabaseKey(keyFile));
 		assertEquals(newEncryptedKeyHex, loadDatabaseKey(keyBackupFile));
@@ -342,7 +366,7 @@ public class AccountManagerImplTest extends BrambleMockTestCase {
 	private void storeDatabaseKey(File f, String hex) throws IOException {
 		f.getParentFile().mkdirs();
 		FileOutputStream out = new FileOutputStream(f);
-		out.write(hex.getBytes(Charset.forName("UTF-8")));
+		out.write(hex.getBytes("UTF-8"));
 		out.flush();
 		out.close();
 	}
@@ -350,7 +374,7 @@ public class AccountManagerImplTest extends BrambleMockTestCase {
 	@Nullable
 	private String loadDatabaseKey(File f) throws IOException {
 		BufferedReader reader = new BufferedReader(new InputStreamReader(
-				new FileInputStream(f), Charset.forName("UTF-8")));
+				new FileInputStream(f), "UTF-8"));
 		String hex = reader.readLine();
 		reader.close();
 		return hex;

bramble-core/src/test/java/org/briarproject/bramble/connection/ConnectionRegistryImplTest.java

@@ -1,611 +0,0 @@
-package org.briarproject.bramble.connection;
-
-import org.briarproject.bramble.api.connection.ConnectionRegistry;
-import org.briarproject.bramble.api.connection.InterruptibleConnection;
-import org.briarproject.bramble.api.contact.ContactId;
-import org.briarproject.bramble.api.contact.PendingContactId;
-import org.briarproject.bramble.api.event.EventBus;
-import org.briarproject.bramble.api.plugin.PluginConfig;
-import org.briarproject.bramble.api.plugin.TransportId;
-import org.briarproject.bramble.api.plugin.event.ConnectionClosedEvent;
-import org.briarproject.bramble.api.plugin.event.ConnectionOpenedEvent;
-import org.briarproject.bramble.api.plugin.event.ContactConnectedEvent;
-import org.briarproject.bramble.api.plugin.event.ContactDisconnectedEvent;
-import org.briarproject.bramble.api.rendezvous.event.RendezvousConnectionClosedEvent;
-import org.briarproject.bramble.api.rendezvous.event.RendezvousConnectionOpenedEvent;
-import org.briarproject.bramble.api.sync.Priority;
-import org.briarproject.bramble.test.BrambleMockTestCase;
-import org.jmock.Expectations;
-import org.junit.Test;
-
-import java.util.Collection;
-
-import static java.util.Collections.emptyList;
-import static java.util.Collections.emptyMap;
-import static java.util.Collections.singletonList;
-import static java.util.Collections.singletonMap;
-import static org.briarproject.bramble.test.TestUtils.getContactId;
-import static org.briarproject.bramble.test.TestUtils.getRandomId;
-import static org.briarproject.bramble.test.TestUtils.getTransportId;
-import static org.briarproject.bramble.util.StringUtils.fromHexString;
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertFalse;
-import static org.junit.Assert.assertTrue;
-import static org.junit.Assert.fail;
-
-public class ConnectionRegistryImplTest extends BrambleMockTestCase {
-
-	private final EventBus eventBus = context.mock(EventBus.class);
-	private final PluginConfig pluginConfig = context.mock(PluginConfig.class);
-	private final InterruptibleConnection conn1 =
-			context.mock(InterruptibleConnection.class, "conn1");
-	private final InterruptibleConnection conn2 =
-			context.mock(InterruptibleConnection.class, "conn2");
-	private final InterruptibleConnection conn3 =
-			context.mock(InterruptibleConnection.class, "conn3");
-
-	private final ContactId contactId1 = getContactId();
-	private final ContactId contactId2 = getContactId();
-	private final TransportId transportId1 = getTransportId();
-	private final TransportId transportId2 = getTransportId();
-	private final TransportId transportId3 = getTransportId();
-	private final PendingContactId pendingContactId =
-			new PendingContactId(getRandomId());
-
-	private final Priority low =
-			new Priority(fromHexString("00000000000000000000000000000000"));
-	private final Priority high =
-			new Priority(fromHexString("FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF"));
-
-	@Test
-	public void testRegisterMultipleConnections() {
-		context.checking(new Expectations() {{
-			allowing(pluginConfig).getTransportPreferences();
-			will(returnValue(emptyMap()));
-		}});
-
-		ConnectionRegistry c =
-				new ConnectionRegistryImpl(eventBus, pluginConfig);
-
-		// The registry should be empty
-		assertEquals(emptyList(), c.getConnectedContacts(transportId1));
-		assertEquals(emptyList(), c.getConnectedOrBetterContacts(transportId1));
-		assertEquals(emptyList(), c.getConnectedContacts(transportId2));
-		assertEquals(emptyList(), c.getConnectedOrBetterContacts(transportId2));
-		assertEquals(emptyList(), c.getConnectedContacts(transportId3));
-		assertEquals(emptyList(), c.getConnectedOrBetterContacts(transportId3));
-		assertFalse(c.isConnected(contactId1));
-		assertFalse(c.isConnected(contactId1, transportId1));
-		assertFalse(c.isConnected(contactId1, transportId2));
-		assertFalse(c.isConnected(contactId1, transportId3));
-
-		// Check that a registered connection shows up - this should
-		// broadcast a ConnectionOpenedEvent and a ContactConnectedEvent
-		context.checking(new Expectations() {{
-			oneOf(eventBus).broadcast(with(any(ConnectionOpenedEvent.class)));
-			oneOf(eventBus).broadcast(with(any(ContactConnectedEvent.class)));
-		}});
-		c.registerIncomingConnection(contactId1, transportId1, conn1);
-		context.assertIsSatisfied();
-
-		assertEquals(singletonList(contactId1),
-				c.getConnectedContacts(transportId1));
-		assertEquals(singletonList(contactId1),
-				c.getConnectedOrBetterContacts(transportId1));
-		assertTrue(c.isConnected(contactId1));
-		assertTrue(c.isConnected(contactId1, transportId1));
-
-		// Register another connection with the same contact and transport -
-		// this should broadcast a ConnectionOpenedEvent and lookup should be
-		// unaffected
-		context.checking(new Expectations() {{
-			oneOf(eventBus).broadcast(with(any(ConnectionOpenedEvent.class)));
-		}});
-		c.registerIncomingConnection(contactId1, transportId1, conn2);
-		context.assertIsSatisfied();
-
-		assertEquals(singletonList(contactId1),
-				c.getConnectedContacts(transportId1));
-		assertEquals(singletonList(contactId1),
-				c.getConnectedOrBetterContacts(transportId1));
-		assertTrue(c.isConnected(contactId1));
-		assertTrue(c.isConnected(contactId1, transportId1));
-
-		// Unregister one of the connections - this should broadcast a
-		// ConnectionClosedEvent and lookup should be unaffected
-		context.checking(new Expectations() {{
-			oneOf(eventBus).broadcast(with(any(ConnectionClosedEvent.class)));
-		}});
-		c.unregisterConnection(contactId1, transportId1, conn1, true, false);
-		context.assertIsSatisfied();
-
-		assertEquals(singletonList(contactId1),
-				c.getConnectedContacts(transportId1));
-		assertEquals(singletonList(contactId1),
-				c.getConnectedOrBetterContacts(transportId1));
-		assertTrue(c.isConnected(contactId1));
-		assertTrue(c.isConnected(contactId1, transportId1));
-
-		// Unregister the other connection - this should broadcast a
-		// ConnectionClosedEvent and a ContactDisconnectedEvent
-		context.checking(new Expectations() {{
-			oneOf(eventBus).broadcast(with(any(ConnectionClosedEvent.class)));
-			oneOf(eventBus).broadcast(with(any(
-					ContactDisconnectedEvent.class)));
-		}});
-		c.unregisterConnection(contactId1, transportId1, conn2, true, false);
-		context.assertIsSatisfied();
-
-		assertEquals(emptyList(), c.getConnectedContacts(transportId1));
-		assertEquals(emptyList(), c.getConnectedOrBetterContacts(transportId1));
-		assertFalse(c.isConnected(contactId1));
-		assertFalse(c.isConnected(contactId1, transportId1));
-
-		// Try to unregister the connection again - exception should be thrown
-		try {
-			c.unregisterConnection(contactId1, transportId1, conn2,
-					true, false);
-			fail();
-		} catch (IllegalArgumentException expected) {
-			// Expected
-		}
-	}
-
-	@Test
-	public void testRegisterMultipleContacts() {
-		context.checking(new Expectations() {{
-			allowing(pluginConfig).getTransportPreferences();
-			will(returnValue(emptyMap()));
-		}});
-
-		ConnectionRegistry c =
-				new ConnectionRegistryImpl(eventBus, pluginConfig);
-
-		// Register two contacts with one transport, then one of the contacts
-		// with a second transport - this should broadcast three
-		// ConnectionOpenedEvents and two ContactConnectedEvents
-		context.checking(new Expectations() {{
-			exactly(3).of(eventBus).broadcast(with(any(
-					ConnectionOpenedEvent.class)));
-			exactly(2).of(eventBus).broadcast(with(any(
-					ContactConnectedEvent.class)));
-		}});
-		c.registerIncomingConnection(contactId1, transportId1, conn1);
-		c.registerIncomingConnection(contactId2, transportId1, conn2);
-		c.registerIncomingConnection(contactId2, transportId2, conn3);
-		context.assertIsSatisfied();
-
-		assertTrue(c.isConnected(contactId1));
-		assertTrue(c.isConnected(contactId2));
-
-		assertTrue(c.isConnected(contactId1, transportId1));
-		assertFalse(c.isConnected(contactId1, transportId2));
-
-		assertTrue(c.isConnected(contactId2, transportId1));
-		assertTrue(c.isConnected(contactId2, transportId2));
-
-		Collection<ContactId> connected = c.getConnectedContacts(transportId1);
-		assertEquals(2, connected.size());
-		assertTrue(connected.contains(contactId1));
-		assertTrue(connected.contains(contactId2));
-
-		connected = c.getConnectedOrBetterContacts(transportId1);
-		assertEquals(2, connected.size());
-		assertTrue(connected.contains(contactId1));
-		assertTrue(connected.contains(contactId2));
-
-		assertEquals(singletonList(contactId2),
-				c.getConnectedContacts(transportId2));
-		assertEquals(singletonList(contactId2),
-				c.getConnectedOrBetterContacts(transportId2));
-	}
-
-	@Test
-	public void testConnectionsAreNotInterruptedUnlessPriorityIsSet() {
-		// Prefer transport 2 to transport 1
-		context.checking(new Expectations() {{
-			allowing(pluginConfig).getTransportPreferences();
-			will(returnValue(
-					singletonMap(transportId1, singletonList(transportId2))));
-		}});
-
-		ConnectionRegistry c =
-				new ConnectionRegistryImpl(eventBus, pluginConfig);
-
-		// Connect via transport 1 (worse than 2) with no priority set
-		context.checking(new Expectations() {{
-			oneOf(eventBus).broadcast(with(any(ConnectionOpenedEvent.class)));
-			oneOf(eventBus).broadcast(with(any(ContactConnectedEvent.class)));
-		}});
-		c.registerIncomingConnection(contactId1, transportId1, conn1);
-		context.assertIsSatisfied();
-
-		assertEquals(singletonList(contactId1),
-				c.getConnectedContacts(transportId1));
-		assertEquals(singletonList(contactId1),
-				c.getConnectedOrBetterContacts(transportId1));
-
-		assertEquals(emptyList(), c.getConnectedContacts(transportId2));
-		assertEquals(emptyList(), c.getConnectedOrBetterContacts(transportId2));
-
-		// Connect via transport 2 (better than 1) and set priority to high -
-		// the old connection should not be interrupted, despite using a worse
-		// transport, to remain compatible with old peers
-		context.checking(new Expectations() {{
-			oneOf(eventBus).broadcast(with(any(ConnectionOpenedEvent.class)));
-		}});
-		c.registerOutgoingConnection(contactId1, transportId2, conn2, high);
-		context.assertIsSatisfied();
-
-		assertEquals(singletonList(contactId1),
-				c.getConnectedContacts(transportId1));
-		assertEquals(singletonList(contactId1),
-				c.getConnectedOrBetterContacts(transportId1));
-
-		assertEquals(singletonList(contactId1),
-				c.getConnectedContacts(transportId2));
-		assertEquals(singletonList(contactId1),
-				c.getConnectedOrBetterContacts(transportId2));
-
-		// Connect via transport 3 (no preference) and set priority to high -
-		// again, no interruptions are expected
-		context.checking(new Expectations() {{
-			oneOf(eventBus).broadcast(with(any(ConnectionOpenedEvent.class)));
-		}});
-		c.registerOutgoingConnection(contactId1, transportId3, conn3, high);
-		context.assertIsSatisfied();
-
-		assertEquals(singletonList(contactId1),
-				c.getConnectedContacts(transportId1));
-		assertEquals(singletonList(contactId1),
-				c.getConnectedOrBetterContacts(transportId1));
-
-		assertEquals(singletonList(contactId1),
-				c.getConnectedContacts(transportId2));
-		assertEquals(singletonList(contactId1),
-				c.getConnectedOrBetterContacts(transportId2));
-
-		assertEquals(singletonList(contactId1),
-				c.getConnectedContacts(transportId3));
-		assertEquals(singletonList(contactId1),
-				c.getConnectedOrBetterContacts(transportId3));
-	}
-
-	@Test
-	public void testNewConnectionIsInterruptedIfOldConnectionUsesBetterTransport() {
-		// Prefer transport 1 to transport 2
-		context.checking(new Expectations() {{
-			allowing(pluginConfig).getTransportPreferences();
-			will(returnValue(
-					singletonMap(transportId2, singletonList(transportId1))));
-		}});
-
-		ConnectionRegistry c =
-				new ConnectionRegistryImpl(eventBus, pluginConfig);
-
-		// Connect via transport 1 (better than 2) and set priority to low
-		context.checking(new Expectations() {{
-			oneOf(eventBus).broadcast(with(any(ConnectionOpenedEvent.class)));
-			oneOf(eventBus).broadcast(with(any(ContactConnectedEvent.class)));
-		}});
-		c.registerOutgoingConnection(contactId1, transportId1, conn1, low);
-		context.assertIsSatisfied();
-
-		assertEquals(singletonList(contactId1),
-				c.getConnectedContacts(transportId1));
-		assertEquals(singletonList(contactId1),
-				c.getConnectedOrBetterContacts(transportId1));
-
-		// The contact is not connected via transport 2 but is connected via a
-		// better transport
-		assertEquals(emptyList(), c.getConnectedContacts(transportId2));
-		assertEquals(singletonList(contactId1),
-				c.getConnectedOrBetterContacts(transportId2));
-
-		// Connect via transport 2 (worse than 1) and set priority to high -
-		// the new connection should be interrupted because it uses a worse
-		// transport
-		context.checking(new Expectations() {{
-			oneOf(conn2).interruptOutgoingSession();
-			oneOf(eventBus).broadcast(with(any(ConnectionOpenedEvent.class)));
-		}});
-		c.registerOutgoingConnection(contactId1, transportId2, conn2, high);
-		context.assertIsSatisfied();
-
-		assertEquals(singletonList(contactId1),
-				c.getConnectedContacts(transportId1));
-		assertEquals(singletonList(contactId1),
-				c.getConnectedOrBetterContacts(transportId1));
-
-		assertEquals(singletonList(contactId1),
-				c.getConnectedContacts(transportId2));
-		assertEquals(singletonList(contactId1),
-				c.getConnectedOrBetterContacts(transportId2));
-
-		// Connect via transport 3 (no preference) and set priority to low -
-		// no further interruptions
-		context.checking(new Expectations() {{
-			oneOf(eventBus).broadcast(with(any(ConnectionOpenedEvent.class)));
-		}});
-		c.registerOutgoingConnection(contactId1, transportId3, conn3, low);
-		context.assertIsSatisfied();
-
-		assertEquals(singletonList(contactId1),
-				c.getConnectedContacts(transportId1));
-		assertEquals(singletonList(contactId1),
-				c.getConnectedOrBetterContacts(transportId1));
-
-		assertEquals(singletonList(contactId1),
-				c.getConnectedContacts(transportId2));
-		assertEquals(singletonList(contactId1),
-				c.getConnectedOrBetterContacts(transportId2));
-
-		assertEquals(singletonList(contactId1),
-				c.getConnectedContacts(transportId3));
-		assertEquals(singletonList(contactId1),
-				c.getConnectedOrBetterContacts(transportId3));
-
-		// Unregister the interrupted connection (transport 2)
-		context.checking(new Expectations() {{
-			oneOf(eventBus).broadcast(with(any(ConnectionClosedEvent.class)));
-		}});
-		c.unregisterConnection(contactId1, transportId2, conn2, true, false);
-		context.assertIsSatisfied();
-
-		assertEquals(singletonList(contactId1),
-				c.getConnectedContacts(transportId1));
-		assertEquals(singletonList(contactId1),
-				c.getConnectedOrBetterContacts(transportId1));
-
-		// The contact is not connected via transport 2 but is connected via a
-		// better transport
-		assertEquals(emptyList(), c.getConnectedContacts(transportId2));
-		assertEquals(singletonList(contactId1),
-				c.getConnectedOrBetterContacts(transportId2));
-
-		assertEquals(singletonList(contactId1),
-				c.getConnectedContacts(transportId3));
-		assertEquals(singletonList(contactId1),
-				c.getConnectedOrBetterContacts(transportId3));
-	}
-
-	@Test
-	public void testOldConnectionIsInterruptedIfNewConnectionUsesBetterTransport() {
-		// Prefer transport 2 to transport 1
-		context.checking(new Expectations() {{
-			allowing(pluginConfig).getTransportPreferences();
-			will(returnValue(
-					singletonMap(transportId1, singletonList(transportId2))));
-		}});
-
-		ConnectionRegistry c =
-				new ConnectionRegistryImpl(eventBus, pluginConfig);
-
-		// Connect via transport 1 (worse than 2) and set priority to high
-		context.checking(new Expectations() {{
-			oneOf(eventBus).broadcast(with(any(ConnectionOpenedEvent.class)));
-			oneOf(eventBus).broadcast(with(any(ContactConnectedEvent.class)));
-		}});
-		c.registerOutgoingConnection(contactId1, transportId1, conn1, high);
-		context.assertIsSatisfied();
-
-		assertEquals(singletonList(contactId1),
-				c.getConnectedContacts(transportId1));
-		assertEquals(singletonList(contactId1),
-				c.getConnectedOrBetterContacts(transportId1));
-
-		assertEquals(emptyList(), c.getConnectedContacts(transportId2));
-		assertEquals(emptyList(), c.getConnectedOrBetterContacts(transportId2));
-
-		// Connect via transport 2 (better than 1) and set priority to low -
-		// the old connection should be interrupted because it uses a worse
-		// transport
-		context.checking(new Expectations() {{
-			oneOf(conn1).interruptOutgoingSession();
-			oneOf(eventBus).broadcast(with(any(ConnectionOpenedEvent.class)));
-		}});
-		c.registerOutgoingConnection(contactId1, transportId2, conn2, low);
-		context.assertIsSatisfied();
-
-		assertEquals(singletonList(contactId1),
-				c.getConnectedContacts(transportId1));
-		assertEquals(singletonList(contactId1),
-				c.getConnectedOrBetterContacts(transportId1));
-
-		assertEquals(singletonList(contactId1),
-				c.getConnectedContacts(transportId2));
-		assertEquals(singletonList(contactId1),
-				c.getConnectedOrBetterContacts(transportId2));
-
-		// Connect via transport 3 (no preference) and set priority to high -
-		// no further interruptions
-		context.checking(new Expectations() {{
-			oneOf(eventBus).broadcast(with(any(ConnectionOpenedEvent.class)));
-		}});
-		c.registerOutgoingConnection(contactId1, transportId3, conn3, high);
-		context.assertIsSatisfied();
-
-		assertEquals(singletonList(contactId1),
-				c.getConnectedContacts(transportId1));
-		assertEquals(singletonList(contactId1),
-				c.getConnectedOrBetterContacts(transportId1));
-
-		assertEquals(singletonList(contactId1),
-				c.getConnectedContacts(transportId2));
-		assertEquals(singletonList(contactId1),
-				c.getConnectedOrBetterContacts(transportId2));
-
-		assertEquals(singletonList(contactId1),
-				c.getConnectedContacts(transportId3));
-		assertEquals(singletonList(contactId1),
-				c.getConnectedOrBetterContacts(transportId3));
-
-		// Unregister the interrupted connection (transport 1)
-		context.checking(new Expectations() {{
-			oneOf(eventBus).broadcast(with(any(ConnectionClosedEvent.class)));
-		}});
-		c.unregisterConnection(contactId1, transportId1, conn1, true, false);
-		context.assertIsSatisfied();
-
-		// The contact is not connected via transport 1 but is connected via a
-		// better transport
-		assertEquals(emptyList(), c.getConnectedContacts(transportId1));
-		assertEquals(singletonList(contactId1),
-				c.getConnectedOrBetterContacts(transportId1));
-
-		assertEquals(singletonList(contactId1),
-				c.getConnectedContacts(transportId2));
-		assertEquals(singletonList(contactId1),
-				c.getConnectedOrBetterContacts(transportId2));
-
-		assertEquals(singletonList(contactId1),
-				c.getConnectedContacts(transportId3));
-		assertEquals(singletonList(contactId1),
-				c.getConnectedOrBetterContacts(transportId3));
-	}
-
-	@Test
-	public void testNewConnectionIsInterruptedIfOldConnectionHasHigherPriority() {
-		context.checking(new Expectations() {{
-			allowing(pluginConfig).getTransportPreferences();
-			will(returnValue(emptyMap()));
-		}});
-
-		ConnectionRegistry c =
-				new ConnectionRegistryImpl(eventBus, pluginConfig);
-
-		// Register a connection with high priority
-		context.checking(new Expectations() {{
-			oneOf(eventBus).broadcast(with(any(ConnectionOpenedEvent.class)));
-			oneOf(eventBus).broadcast(with(any(ContactConnectedEvent.class)));
-		}});
-		c.registerOutgoingConnection(contactId1, transportId1, conn1, high);
-		context.assertIsSatisfied();
-
-		assertEquals(singletonList(contactId1),
-				c.getConnectedContacts(transportId1));
-		assertEquals(singletonList(contactId1),
-				c.getConnectedOrBetterContacts(transportId1));
-
-		// Register another connection via the same transport (no priority yet)
-		context.checking(new Expectations() {{
-			oneOf(eventBus).broadcast(with(any(ConnectionOpenedEvent.class)));
-		}});
-		c.registerIncomingConnection(contactId1, transportId1, conn2);
-		context.assertIsSatisfied();
-
-		assertEquals(singletonList(contactId1),
-				c.getConnectedContacts(transportId1));
-		assertEquals(singletonList(contactId1),
-				c.getConnectedOrBetterContacts(transportId1));
-
-		// Set the priority of the second connection to low - the second
-		// connection should be interrupted
-		context.checking(new Expectations() {{
-			oneOf(conn2).interruptOutgoingSession();
-		}});
-		c.setPriority(contactId1, transportId1, conn2, low);
-		context.assertIsSatisfied();
-
-		assertEquals(singletonList(contactId1),
-				c.getConnectedContacts(transportId1));
-		assertEquals(singletonList(contactId1),
-				c.getConnectedOrBetterContacts(transportId1));
-
-		// Register a third connection with low priority - it should also be
-		// interrupted
-		context.checking(new Expectations() {{
-			oneOf(conn3).interruptOutgoingSession();
-			oneOf(eventBus).broadcast(with(any(ConnectionOpenedEvent.class)));
-		}});
-		c.registerOutgoingConnection(contactId1, transportId1, conn3, low);
-		context.assertIsSatisfied();
-
-		assertEquals(singletonList(contactId1),
-				c.getConnectedContacts(transportId1));
-		assertEquals(singletonList(contactId1),
-				c.getConnectedOrBetterContacts(transportId1));
-	}
-
-	@Test
-	public void testOldConnectionIsInterruptedIfNewConnectionHasHigherPriority() {
-		context.checking(new Expectations() {{
-			allowing(pluginConfig).getTransportPreferences();
-			will(returnValue(emptyMap()));
-		}});
-
-		ConnectionRegistry c =
-				new ConnectionRegistryImpl(eventBus, pluginConfig);
-
-		// Register a connection with low priority
-		context.checking(new Expectations() {{
-			oneOf(eventBus).broadcast(with(any(ConnectionOpenedEvent.class)));
-			oneOf(eventBus).broadcast(with(any(ContactConnectedEvent.class)));
-		}});
-		c.registerOutgoingConnection(contactId1, transportId1, conn1, low);
-		context.assertIsSatisfied();
-
-		assertEquals(singletonList(contactId1),
-				c.getConnectedContacts(transportId1));
-		assertEquals(singletonList(contactId1),
-				c.getConnectedOrBetterContacts(transportId1));
-
-		// Register another connection via the same transport (no priority yet)
-		context.checking(new Expectations() {{
-			oneOf(eventBus).broadcast(with(any(ConnectionOpenedEvent.class)));
-		}});
-		c.registerIncomingConnection(contactId1, transportId1, conn2);
-		context.assertIsSatisfied();
-
-		assertEquals(singletonList(contactId1),
-				c.getConnectedContacts(transportId1));
-		assertEquals(singletonList(contactId1),
-				c.getConnectedOrBetterContacts(transportId1));
-
-		// Set the priority of the second connection to high - the first
-		// connection should be interrupted
-		context.checking(new Expectations() {{
-			oneOf(conn1).interruptOutgoingSession();
-		}});
-		c.setPriority(contactId1, transportId1, conn2, high);
-		context.assertIsSatisfied();
-
-		assertEquals(singletonList(contactId1),
-				c.getConnectedContacts(transportId1));
-		assertEquals(singletonList(contactId1),
-				c.getConnectedOrBetterContacts(transportId1));
-	}
-
-	@Test
-	public void testRegisterAndUnregisterPendingContacts() {
-		context.checking(new Expectations() {{
-			allowing(pluginConfig).getTransportPreferences();
-			will(returnValue(emptyMap()));
-		}});
-
-		ConnectionRegistry c =
-				new ConnectionRegistryImpl(eventBus, pluginConfig);
-
-		context.checking(new Expectations() {{
-			oneOf(eventBus).broadcast(with(any(
-					RendezvousConnectionOpenedEvent.class)));
-		}});
-		assertTrue(c.registerConnection(pendingContactId));
-		assertFalse(c.registerConnection(pendingContactId)); // Redundant
-		context.assertIsSatisfied();
-
-		context.checking(new Expectations() {{
-			oneOf(eventBus).broadcast(with(any(
-					RendezvousConnectionClosedEvent.class)));
-		}});
-		c.unregisterConnection(pendingContactId, true);
-		context.assertIsSatisfied();
-
-		try {
-			c.unregisterConnection(pendingContactId, true);
-			fail();
-		} catch (IllegalArgumentException expected) {
-			// Expected
-		}
-	}
-}

bramble-core/src/test/java/org/briarproject/bramble/contact/ContactExchangeIntegrationTestComponent.java

@@ -2,13 +2,13 @@ package org.briarproject.bramble.contact;
 
 import org.briarproject.bramble.BrambleCoreEagerSingletons;
 import org.briarproject.bramble.BrambleCoreModule;
-import org.briarproject.bramble.api.connection.ConnectionManager;
 import org.briarproject.bramble.api.contact.ContactExchangeManager;
 import org.briarproject.bramble.api.contact.ContactManager;
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.identity.IdentityManager;
 import org.briarproject.bramble.api.lifecycle.IoExecutor;
 import org.briarproject.bramble.api.lifecycle.LifecycleManager;
+import org.briarproject.bramble.api.plugin.ConnectionManager;
 import org.briarproject.bramble.test.BrambleCoreIntegrationTestModule;
 
 import java.util.concurrent.Executor;

bramble-core/src/test/java/org/briarproject/bramble/crypto/PasswordBasedEncryptionTest.java

@@ -1,35 +1,25 @@
 package org.briarproject.bramble.crypto;
 
-import org.briarproject.bramble.api.crypto.DecryptionException;
-import org.briarproject.bramble.api.crypto.KeyStrengthener;
-import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.system.SystemClock;
-import org.briarproject.bramble.test.BrambleMockTestCase;
+import org.briarproject.bramble.test.BrambleTestCase;
 import org.briarproject.bramble.test.TestSecureRandomProvider;
-import org.jmock.Expectations;
+import org.briarproject.bramble.test.TestUtils;
 import org.junit.Test;
 
-import static org.briarproject.bramble.api.crypto.DecryptionResult.INVALID_CIPHERTEXT;
+import java.util.Random;
-import static org.briarproject.bramble.api.crypto.DecryptionResult.INVALID_PASSWORD;
+
-import static org.briarproject.bramble.api.crypto.DecryptionResult.KEY_STRENGTHENER_ERROR;
-import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
-import static org.briarproject.bramble.test.TestUtils.getSecretKey;
 import static org.junit.Assert.assertArrayEquals;
-import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
-import static org.junit.Assert.fail;
 
-public class PasswordBasedEncryptionTest extends BrambleMockTestCase {
+public class PasswordBasedEncryptionTest extends BrambleTestCase {
-
-	private final KeyStrengthener keyStrengthener =
-			context.mock(KeyStrengthener.class);
 
 	private final CryptoComponentImpl crypto =
 			new CryptoComponentImpl(new TestSecureRandomProvider(),
 					new ScryptKdf(new SystemClock()));
 
 	@Test
-	public void testEncryptionAndDecryption() throws Exception {
+	public void testEncryptionAndDecryption() {
-		byte[] input = getRandomBytes(1234);
+		byte[] input = TestUtils.getRandomBytes(1234);
 		String password = "password";
 		byte[] ciphertext = crypto.encryptWithPassword(input, password, null);
 		byte[] output = crypto.decryptWithPassword(ciphertext, password, null);
@@ -37,80 +27,14 @@ public class PasswordBasedEncryptionTest extends BrambleMockTestCase {
 	}
 
 	@Test
-	public void testInvalidFormatVersionThrowsException() {
+	public void testInvalidCiphertextReturnsNull() {
-		byte[] input = getRandomBytes(1234);
+		byte[] input = TestUtils.getRandomBytes(1234);
 		String password = "password";
 		byte[] ciphertext = crypto.encryptWithPassword(input, password, null);
-
+		// Modify the ciphertext
-		// Modify the format version
+		int position = new Random().nextInt(ciphertext.length);
-		ciphertext[0] ^= (byte) 0xFF;
+		ciphertext[position] = (byte) (ciphertext[position] ^ 0xFF);
-		try {
+		byte[] output = crypto.decryptWithPassword(ciphertext, password, null);
-			crypto.decryptWithPassword(ciphertext, password, null);
+		assertNull(output);
-			fail();
-		} catch (DecryptionException expected) {
-			assertEquals(INVALID_CIPHERTEXT, expected.getDecryptionResult());
-		}
-	}
-
-	@Test
-	public void testInvalidPasswordThrowsException() {
-		byte[] input = getRandomBytes(1234);
-		byte[] ciphertext = crypto.encryptWithPassword(input, "password", null);
-
-		// Try to decrypt with the wrong password
-		try {
-			crypto.decryptWithPassword(ciphertext, "wrong", null);
-			fail();
-		} catch (DecryptionException expected) {
-			assertEquals(INVALID_PASSWORD, expected.getDecryptionResult());
-		}
-	}
-
-	@Test
-	public void testMissingKeyStrengthenerThrowsException() {
-		SecretKey strengthened = getSecretKey();
-		context.checking(new Expectations() {{
-			oneOf(keyStrengthener).strengthenKey(with(any(SecretKey.class)));
-			will(returnValue(strengthened));
-		}});
-
-		// Use the key strengthener during encryption
-		byte[] input = getRandomBytes(1234);
-		String password = "password";
-		byte[] ciphertext =
-				crypto.encryptWithPassword(input, password, keyStrengthener);
-
-		// The key strengthener is missing during decryption
-		try {
-			crypto.decryptWithPassword(ciphertext, password, null);
-			fail();
-		} catch (DecryptionException expected) {
-			assertEquals(KEY_STRENGTHENER_ERROR, expected.getDecryptionResult());
-		}
-	}
-
-	@Test
-	public void testKeyStrengthenerFailureThrowsException() {
-		SecretKey strengthened = getSecretKey();
-		context.checking(new Expectations() {{
-			oneOf(keyStrengthener).strengthenKey(with(any(SecretKey.class)));
-			will(returnValue(strengthened));
-			oneOf(keyStrengthener).isInitialised();
-			will(returnValue(false));
-		}});
-
-		// Use the key strengthener during encryption
-		byte[] input = getRandomBytes(1234);
-		String password = "password";
-		byte[] ciphertext =
-				crypto.encryptWithPassword(input, password, keyStrengthener);
-
-		// The key strengthener fails during decryption
-		try {
-			crypto.decryptWithPassword(ciphertext, password, keyStrengthener);
-			fail();
-		} catch (DecryptionException expected) {
-			assertEquals(KEY_STRENGTHENER_ERROR, expected.getDecryptionResult());
-		}
 	}
 }

bramble-core/src/test/java/org/briarproject/bramble/io/TimeoutInputStreamTest.java

@@ -1,143 +0,0 @@
-package org.briarproject.bramble.io;
-
-import org.briarproject.bramble.test.BrambleTestCase;
-import org.briarproject.bramble.test.SettableClock;
-import org.junit.Before;
-import org.junit.Test;
-
-import java.io.IOException;
-import java.io.InputStream;
-import java.util.concurrent.CountDownLatch;
-import java.util.concurrent.atomic.AtomicBoolean;
-import java.util.concurrent.atomic.AtomicLong;
-
-import static java.util.concurrent.TimeUnit.MINUTES;
-import static java.util.concurrent.TimeUnit.SECONDS;
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertFalse;
-import static org.junit.Assert.assertTrue;
-import static org.junit.Assert.fail;
-
-public class TimeoutInputStreamTest extends BrambleTestCase {
-
-	private static final long TIMEOUT_MS = MINUTES.toMillis(1);
-
-	private final long now = System.currentTimeMillis();
-
-	private AtomicLong time;
-	private UnresponsiveInputStream in;
-	private AtomicBoolean listenerCalled;
-	private TimeoutInputStream stream;
-	private CountDownLatch readReturned;
-
-	@Before
-	public void setUp() {
-		time = new AtomicLong(now);
-		in = new UnresponsiveInputStream();
-		listenerCalled = new AtomicBoolean(false);
-		stream = new TimeoutInputStream(new SettableClock(time), in,
-				TIMEOUT_MS, stream -> listenerCalled.set(true));
-		readReturned = new CountDownLatch(1);
-	}
-
-	@Test
-	public void testTimeoutIsReportedIfReadDoesNotReturn() throws Exception {
-		startReading();
-		try {
-			// The stream should not report a timeout
-			assertFalse(stream.hasTimedOut());
-
-			// Time passes
-			time.set(now + TIMEOUT_MS);
-
-			// The stream still shouldn't report a timeout
-			assertFalse(stream.hasTimedOut());
-
-			// Time passes
-			time.set(now + TIMEOUT_MS + 1);
-
-			// The stream should report a timeout
-			assertTrue(stream.hasTimedOut());
-
-			// The listener should not have been called yet
-			assertFalse(listenerCalled.get());
-
-			// Close the stream
-			stream.close();
-
-			// The listener should have been called
-			assertTrue(listenerCalled.get());
-		} finally {
-			// Allow the read to return
-			in.readFinished.countDown();
-		}
-	}
-
-	@Test
-	public void testTimeoutIsNotReportedIfReadReturns() throws Exception {
-		startReading();
-		try {
-			// The stream should not report a timeout
-			assertFalse(stream.hasTimedOut());
-
-			// Time passes
-			time.set(now + TIMEOUT_MS);
-
-			// The stream still shouldn't report a timeout
-			assertFalse(stream.hasTimedOut());
-
-			// Allow the read to finish and wait for it to return
-			in.readFinished.countDown();
-			readReturned.await(10, SECONDS);
-
-			// Time passes
-			time.set(now + TIMEOUT_MS + 1);
-
-			// The stream should not report a timeout as the read has returned
-			assertFalse(stream.hasTimedOut());
-
-			// The listener should not have been called yet
-			assertFalse(listenerCalled.get());
-
-			// Close the stream
-			stream.close();
-
-			// The listener should have been called
-			assertTrue(listenerCalled.get());
-		} finally {
-			// Allow the read to return in case an assertion was thrown
-			in.readFinished.countDown();
-		}
-	}
-
-	private void startReading() throws Exception {
-		// Start a background thread to read from the unresponsive stream
-		new Thread(() -> {
-			try {
-				assertEquals(123, stream.read());
-				readReturned.countDown();
-			} catch (IOException e) {
-				fail();
-			}
-		}).start();
-		// Wait for the background thread to start reading
-		assertTrue(in.readStarted.await(10, SECONDS));
-	}
-
-	private class UnresponsiveInputStream extends InputStream {
-
-		private final CountDownLatch readStarted = new CountDownLatch(1);
-		private final CountDownLatch readFinished = new CountDownLatch(1);
-
-		@Override
-		public int read() throws IOException {
-			readStarted.countDown();
-			try {
-				readFinished.await();
-				return 123;
-			} catch (InterruptedException e) {
-				throw new IOException(e);
-			}
-		}
-	}
-}

bramble-core/src/test/java/org/briarproject/bramble/plugin/BackoffImplTest.java

@@ -0,0 +1,63 @@
+package org.briarproject.bramble.plugin;
+
+import org.briarproject.bramble.test.BrambleTestCase;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+public class BackoffImplTest extends BrambleTestCase {
+
+	private static final int MIN_INTERVAL = 60 * 1000;
+	private static final int MAX_INTERVAL = 60 * 60 * 1000;
+	private static final double BASE = 1.2;
+
+	@Test
+	public void testPollingIntervalStartsAtMinimum() {
+		BackoffImpl b = new BackoffImpl(MIN_INTERVAL, MAX_INTERVAL, BASE);
+		assertEquals(MIN_INTERVAL, b.getPollingInterval());
+	}
+
+	@Test
+	public void testIncrementIncreasesPollingInterval() {
+		BackoffImpl b = new BackoffImpl(MIN_INTERVAL, MAX_INTERVAL, BASE);
+		b.increment();
+		assertTrue(b.getPollingInterval() > MIN_INTERVAL);
+	}
+
+	@Test
+	public void testResetResetsPollingInterval() {
+		BackoffImpl b = new BackoffImpl(MIN_INTERVAL, MAX_INTERVAL, BASE);
+		b.increment();
+		b.increment();
+		b.reset();
+		assertEquals(MIN_INTERVAL, b.getPollingInterval());
+	}
+
+	@Test
+	public void testBaseAffectsBackoffSpeed() {
+		BackoffImpl b = new BackoffImpl(MIN_INTERVAL, MAX_INTERVAL, BASE);
+		b.increment();
+		int interval = b.getPollingInterval();
+		BackoffImpl b1 = new BackoffImpl(MIN_INTERVAL, MAX_INTERVAL, BASE * 2);
+		b1.increment();
+		int interval1 = b1.getPollingInterval();
+		assertTrue(interval < interval1);
+	}
+
+	@Test
+	public void testIntervalDoesNotExceedMaxInterval() {
+		BackoffImpl b = new BackoffImpl(MIN_INTERVAL, MAX_INTERVAL, BASE);
+		for (int i = 0; i < 100; i++) b.increment();
+		assertEquals(MAX_INTERVAL, b.getPollingInterval());
+	}
+
+	@Test
+	public void testIntervalDoesNotExceedMaxIntervalWithInfiniteMultiplier() {
+		BackoffImpl b = new BackoffImpl(MIN_INTERVAL, MAX_INTERVAL,
+				Double.POSITIVE_INFINITY);
+		b.increment();
+		assertEquals(MAX_INTERVAL, b.getPollingInterval());
+	}
+}
+

bramble-core/src/test/java/org/briarproject/bramble/plugin/ConnectionRegistryImplTest.java

@@ -0,0 +1,149 @@
+package org.briarproject.bramble.plugin;
+
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.contact.PendingContactId;
+import org.briarproject.bramble.api.event.EventBus;
+import org.briarproject.bramble.api.plugin.ConnectionRegistry;
+import org.briarproject.bramble.api.plugin.TransportId;
+import org.briarproject.bramble.api.plugin.event.ConnectionClosedEvent;
+import org.briarproject.bramble.api.plugin.event.ConnectionOpenedEvent;
+import org.briarproject.bramble.api.plugin.event.ContactConnectedEvent;
+import org.briarproject.bramble.api.plugin.event.ContactDisconnectedEvent;
+import org.briarproject.bramble.api.rendezvous.event.RendezvousConnectionClosedEvent;
+import org.briarproject.bramble.api.rendezvous.event.RendezvousConnectionOpenedEvent;
+import org.briarproject.bramble.test.BrambleMockTestCase;
+import org.jmock.Expectations;
+import org.junit.Test;
+
+import java.util.Collection;
+
+import static java.util.Collections.emptyList;
+import static java.util.Collections.singletonList;
+import static org.briarproject.bramble.test.TestUtils.getContactId;
+import static org.briarproject.bramble.test.TestUtils.getRandomId;
+import static org.briarproject.bramble.test.TestUtils.getTransportId;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
+
+public class ConnectionRegistryImplTest extends BrambleMockTestCase {
+
+	private final EventBus eventBus = context.mock(EventBus.class);
+
+	private final ContactId contactId = getContactId();
+	private final ContactId contactId1 = getContactId();
+	private final TransportId transportId = getTransportId();
+	private final TransportId transportId1 = getTransportId();
+	private final PendingContactId pendingContactId =
+			new PendingContactId(getRandomId());
+
+	@Test
+	public void testRegisterAndUnregister() {
+		ConnectionRegistry c = new ConnectionRegistryImpl(eventBus);
+
+		// The registry should be empty
+		assertEquals(emptyList(), c.getConnectedContacts(transportId));
+		assertEquals(emptyList(), c.getConnectedContacts(transportId1));
+
+		// Check that a registered connection shows up - this should
+		// broadcast a ConnectionOpenedEvent and a ContactConnectedEvent
+		context.checking(new Expectations() {{
+			oneOf(eventBus).broadcast(with(any(ConnectionOpenedEvent.class)));
+			oneOf(eventBus).broadcast(with(any(ContactConnectedEvent.class)));
+		}});
+		c.registerConnection(contactId, transportId, true);
+		assertEquals(singletonList(contactId),
+				c.getConnectedContacts(transportId));
+		assertEquals(emptyList(), c.getConnectedContacts(transportId1));
+		context.assertIsSatisfied();
+
+		// Register an identical connection - this should broadcast a
+		// ConnectionOpenedEvent and lookup should be unaffected
+		context.checking(new Expectations() {{
+			oneOf(eventBus).broadcast(with(any(ConnectionOpenedEvent.class)));
+		}});
+		c.registerConnection(contactId, transportId, true);
+		assertEquals(singletonList(contactId),
+				c.getConnectedContacts(transportId));
+		assertEquals(emptyList(), c.getConnectedContacts(transportId1));
+		context.assertIsSatisfied();
+
+		// Unregister one of the connections - this should broadcast a
+		// ConnectionClosedEvent and lookup should be unaffected
+		context.checking(new Expectations() {{
+			oneOf(eventBus).broadcast(with(any(ConnectionClosedEvent.class)));
+		}});
+		c.unregisterConnection(contactId, transportId, true);
+		assertEquals(singletonList(contactId),
+				c.getConnectedContacts(transportId));
+		assertEquals(emptyList(), c.getConnectedContacts(transportId1));
+		context.assertIsSatisfied();
+
+		// Unregister the other connection - this should broadcast a
+		// ConnectionClosedEvent and a ContactDisconnectedEvent
+		context.checking(new Expectations() {{
+			oneOf(eventBus).broadcast(with(any(ConnectionClosedEvent.class)));
+			oneOf(eventBus).broadcast(with(any(
+					ContactDisconnectedEvent.class)));
+		}});
+		c.unregisterConnection(contactId, transportId, true);
+		assertEquals(emptyList(), c.getConnectedContacts(transportId));
+		assertEquals(emptyList(), c.getConnectedContacts(transportId1));
+		context.assertIsSatisfied();
+
+		// Try to unregister the connection again - exception should be thrown
+		try {
+			c.unregisterConnection(contactId, transportId, true);
+			fail();
+		} catch (IllegalArgumentException expected) {
+			// Expected
+		}
+
+		// Register both contacts with one transport, one contact with both -
+		// this should broadcast three ConnectionOpenedEvents and two
+		// ContactConnectedEvents
+		context.checking(new Expectations() {{
+			exactly(3).of(eventBus).broadcast(with(any(
+					ConnectionOpenedEvent.class)));
+			exactly(2).of(eventBus).broadcast(with(any(
+					ContactConnectedEvent.class)));
+		}});
+		c.registerConnection(contactId, transportId, true);
+		c.registerConnection(contactId1, transportId, true);
+		c.registerConnection(contactId1, transportId1, true);
+		Collection<ContactId> connected = c.getConnectedContacts(transportId);
+		assertEquals(2, connected.size());
+		assertTrue(connected.contains(contactId));
+		assertTrue(connected.contains(contactId1));
+		assertEquals(singletonList(contactId1),
+				c.getConnectedContacts(transportId1));
+	}
+
+	@Test
+	public void testRegisterAndUnregisterPendingContacts() {
+		ConnectionRegistry c = new ConnectionRegistryImpl(eventBus);
+
+		context.checking(new Expectations() {{
+			oneOf(eventBus).broadcast(with(any(
+					RendezvousConnectionOpenedEvent.class)));
+		}});
+		assertTrue(c.registerConnection(pendingContactId));
+		assertFalse(c.registerConnection(pendingContactId)); // Redundant
+		context.assertIsSatisfied();
+
+		context.checking(new Expectations() {{
+			oneOf(eventBus).broadcast(with(any(
+					RendezvousConnectionClosedEvent.class)));
+		}});
+		c.unregisterConnection(pendingContactId, true);
+		context.assertIsSatisfied();
+
+		try {
+			c.unregisterConnection(pendingContactId, true);
+			fail();
+		} catch (IllegalArgumentException expected) {
+			// Expected
+		}
+	}
+}

bramble-core/src/test/java/org/briarproject/bramble/plugin/PluginManagerImplTest.java

@@ -1,7 +1,7 @@
 package org.briarproject.bramble.plugin;
 
-import org.briarproject.bramble.api.connection.ConnectionManager;
 import org.briarproject.bramble.api.event.EventBus;
+import org.briarproject.bramble.api.plugin.ConnectionManager;
 import org.briarproject.bramble.api.plugin.PluginCallback;
 import org.briarproject.bramble.api.plugin.PluginConfig;
 import org.briarproject.bramble.api.plugin.PluginException;

bramble-core/src/test/java/org/briarproject/bramble/plugin/PollerImplTest.java

@@ -1,10 +1,10 @@
 package org.briarproject.bramble.plugin;
 
-import org.briarproject.bramble.api.connection.ConnectionManager;
-import org.briarproject.bramble.api.connection.ConnectionRegistry;
 import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.contact.event.ContactAddedEvent;
 import org.briarproject.bramble.api.plugin.ConnectionHandler;
+import org.briarproject.bramble.api.plugin.ConnectionManager;
+import org.briarproject.bramble.api.plugin.ConnectionRegistry;
 import org.briarproject.bramble.api.plugin.Plugin;
 import org.briarproject.bramble.api.plugin.PluginManager;
 import org.briarproject.bramble.api.plugin.TransportConnectionWriter;
@@ -12,6 +12,7 @@ import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
 import org.briarproject.bramble.api.plugin.event.ConnectionClosedEvent;
+import org.briarproject.bramble.api.plugin.event.ConnectionOpenedEvent;
 import org.briarproject.bramble.api.plugin.event.TransportActiveEvent;
 import org.briarproject.bramble.api.plugin.event.TransportInactiveEvent;
 import org.briarproject.bramble.api.plugin.simplex.SimplexPlugin;
@@ -37,7 +38,7 @@ import static java.util.Collections.emptyList;
 import static java.util.Collections.singletonList;
 import static java.util.Collections.singletonMap;
 import static java.util.concurrent.TimeUnit.MILLISECONDS;
-import static org.briarproject.bramble.test.CollectionMatcher.collectionOf;
+import static org.briarproject.bramble.test.ListMatcher.listOf;
 import static org.briarproject.bramble.test.PairMatcher.pairOf;
 import static org.briarproject.bramble.test.TestUtils.getContactId;
 import static org.briarproject.bramble.test.TestUtils.getTransportId;
@@ -156,20 +157,8 @@ public class PollerImplTest extends BrambleMockTestCase {
 	}
 
 	@Test
-	public void testDoesNotReconnectOnOutgoingConnectionClosed() {
+	public void testRescheduleAndReconnectOnConnectionClosed()
-		DuplexPlugin plugin = context.mock(DuplexPlugin.class);
+			throws Exception {
-
-		context.checking(new Expectations() {{
-			allowing(plugin).getId();
-			will(returnValue(transportId));
-		}});
-
-		poller.eventOccurred(new ConnectionClosedEvent(contactId, transportId,
-				false, false));
-	}
-
-	@Test
-	public void testReconnectsOnOutgoingConnectionFailed() throws Exception {
 		DuplexPlugin plugin = context.mock(DuplexPlugin.class);
 		DuplexTransportConnection duplexConnection =
 				context.mock(DuplexTransportConnection.class);
@@ -177,37 +166,159 @@ public class PollerImplTest extends BrambleMockTestCase {
 		context.checking(new Expectations() {{
 			allowing(plugin).getId();
 			will(returnValue(transportId));
+			// reschedule()
+			// Get the plugin
+			oneOf(pluginManager).getPlugin(transportId);
+			will(returnValue(plugin));
+			// The plugin supports polling
+			oneOf(plugin).shouldPoll();
+			will(returnValue(true));
+			// Get the plugin
+			oneOf(pluginManager).getPlugin(transportId);
+			will(returnValue(plugin));
+			// The plugin supports polling
+			oneOf(plugin).shouldPoll();
+			will(returnValue(true));
+			// Schedule the next poll
+			oneOf(plugin).getPollingInterval();
+			will(returnValue(pollingInterval));
+			oneOf(clock).currentTimeMillis();
+			will(returnValue(now));
+			oneOf(scheduler).schedule(with(any(Runnable.class)),
+					with((long) pollingInterval), with(MILLISECONDS));
+			will(returnValue(future));
+			// connectToContact()
+			// Check whether the contact is already connected
+			oneOf(connectionRegistry).isConnected(contactId, transportId);
+			will(returnValue(false));
+			// Get the transport properties
+			oneOf(transportPropertyManager).getRemoteProperties(contactId,
+					transportId);
+			will(returnValue(properties));
+			// Connect to the contact
+			oneOf(plugin).createConnection(properties);
+			will(returnValue(duplexConnection));
+			// Pass the connection to the connection manager
+			oneOf(connectionManager).manageOutgoingConnection(contactId,
+					transportId, duplexConnection);
 		}});
-		expectReconnect(plugin, duplexConnection);
 
 		poller.eventOccurred(new ConnectionClosedEvent(contactId, transportId,
-				false, true));
+				false));
 	}
 
 	@Test
-	public void testDoesNotReconnectOnIncomingConnectionClosed() {
+	public void testRescheduleOnConnectionOpened() {
-		DuplexPlugin plugin = context.mock(DuplexPlugin.class);
+		Plugin plugin = context.mock(Plugin.class);
 
 		context.checking(new Expectations() {{
 			allowing(plugin).getId();
 			will(returnValue(transportId));
+			// Get the plugin
+			oneOf(pluginManager).getPlugin(transportId);
+			will(returnValue(plugin));
+			// The plugin supports polling
+			oneOf(plugin).shouldPoll();
+			will(returnValue(true));
+			// Schedule the next poll
+			oneOf(plugin).getPollingInterval();
+			will(returnValue(pollingInterval));
+			oneOf(clock).currentTimeMillis();
+			will(returnValue(now));
+			oneOf(scheduler).schedule(with(any(Runnable.class)),
+					with((long) pollingInterval), with(MILLISECONDS));
+			will(returnValue(future));
 		}});
 
-		poller.eventOccurred(new ConnectionClosedEvent(contactId, transportId,
+		poller.eventOccurred(new ConnectionOpenedEvent(contactId, transportId,
-				true, false));
+				false));
 	}
 
 	@Test
-	public void testDoesNotReconnectOnIncomingConnectionFailed() {
+	public void testRescheduleDoesNotReplaceEarlierTask() {
-		DuplexPlugin plugin = context.mock(DuplexPlugin.class);
+		Plugin plugin = context.mock(Plugin.class);
 
 		context.checking(new Expectations() {{
 			allowing(plugin).getId();
 			will(returnValue(transportId));
+			// First event
+			// Get the plugin
+			oneOf(pluginManager).getPlugin(transportId);
+			will(returnValue(plugin));
+			// The plugin supports polling
+			oneOf(plugin).shouldPoll();
+			will(returnValue(true));
+			// Schedule the next poll
+			oneOf(plugin).getPollingInterval();
+			will(returnValue(pollingInterval));
+			oneOf(clock).currentTimeMillis();
+			will(returnValue(now));
+			oneOf(scheduler).schedule(with(any(Runnable.class)),
+					with((long) pollingInterval), with(MILLISECONDS));
+			will(returnValue(future));
+			// Second event
+			// Get the plugin
+			oneOf(pluginManager).getPlugin(transportId);
+			will(returnValue(plugin));
+			// The plugin supports polling
+			oneOf(plugin).shouldPoll();
+			will(returnValue(true));
+			// Don't replace the previously scheduled task, due earlier
+			oneOf(plugin).getPollingInterval();
+			will(returnValue(pollingInterval));
+			oneOf(clock).currentTimeMillis();
+			will(returnValue(now + 1));
 		}});
 
-		poller.eventOccurred(new ConnectionClosedEvent(contactId, transportId,
+		poller.eventOccurred(new ConnectionOpenedEvent(contactId, transportId,
-				true, false));
+				false));
+		poller.eventOccurred(new ConnectionOpenedEvent(contactId, transportId,
+				false));
+	}
+
+	@Test
+	public void testRescheduleReplacesLaterTask() {
+		Plugin plugin = context.mock(Plugin.class);
+
+		context.checking(new Expectations() {{
+			allowing(plugin).getId();
+			will(returnValue(transportId));
+			// First event
+			// Get the plugin
+			oneOf(pluginManager).getPlugin(transportId);
+			will(returnValue(plugin));
+			// The plugin supports polling
+			oneOf(plugin).shouldPoll();
+			will(returnValue(true));
+			// Schedule the next poll
+			oneOf(plugin).getPollingInterval();
+			will(returnValue(pollingInterval));
+			oneOf(clock).currentTimeMillis();
+			will(returnValue(now));
+			oneOf(scheduler).schedule(with(any(Runnable.class)),
+					with((long) pollingInterval), with(MILLISECONDS));
+			will(returnValue(future));
+			// Second event
+			// Get the plugin
+			oneOf(pluginManager).getPlugin(transportId);
+			will(returnValue(plugin));
+			// The plugin supports polling
+			oneOf(plugin).shouldPoll();
+			will(returnValue(true));
+			// Replace the previously scheduled task, due later
+			oneOf(plugin).getPollingInterval();
+			will(returnValue(pollingInterval - 2));
+			oneOf(clock).currentTimeMillis();
+			will(returnValue(now + 1));
+			oneOf(future).cancel(false);
+			oneOf(scheduler).schedule(with(any(Runnable.class)),
+					with((long) pollingInterval - 2), with(MILLISECONDS));
+		}});
+
+		poller.eventOccurred(new ConnectionOpenedEvent(contactId, transportId,
+				false));
+		poller.eventOccurred(new ConnectionOpenedEvent(contactId, transportId,
+				false));
 	}
 
 	@Test
@@ -240,14 +351,17 @@ public class PollerImplTest extends BrambleMockTestCase {
 			oneOf(scheduler).schedule(with(any(Runnable.class)),
 					with((long) (pollingInterval * 0.5)), with(MILLISECONDS));
 			will(returnValue(future));
+			// FIXME: Revert
+			oneOf(plugin).supportsDiscovery();
+			will(returnValue(false));
 			// Get the transport properties and connected contacts
 			oneOf(transportPropertyManager).getRemoteProperties(transportId);
 			will(returnValue(singletonMap(contactId, properties)));
-			oneOf(connectionRegistry).getConnectedOrBetterContacts(transportId);
+			oneOf(connectionRegistry).getConnectedContacts(transportId);
 			will(returnValue(emptyList()));
 			// Poll the plugin
-			oneOf(plugin).poll(with(collectionOf(
+			oneOf(plugin).poll(with(listOf(pairOf(
-					pairOf(equal(properties), any(ConnectionHandler.class)))));
+					equal(properties), any(ConnectionHandler.class)))));
 		}});
 
 		poller.eventOccurred(new TransportActiveEvent(transportId));
@@ -283,10 +397,13 @@ public class PollerImplTest extends BrambleMockTestCase {
 			oneOf(scheduler).schedule(with(any(Runnable.class)),
 					with((long) (pollingInterval * 0.5)), with(MILLISECONDS));
 			will(returnValue(future));
+			// FIXME: Revert
+			oneOf(plugin).supportsDiscovery();
+			will(returnValue(false));
 			// Get the transport properties and connected contacts
 			oneOf(transportPropertyManager).getRemoteProperties(transportId);
 			will(returnValue(singletonMap(contactId, properties)));
-			oneOf(connectionRegistry).getConnectedOrBetterContacts(transportId);
+			oneOf(connectionRegistry).getConnectedContacts(transportId);
 			will(returnValue(singletonList(contactId)));
 			// All contacts are connected, so don't poll the plugin
 		}});
@@ -320,29 +437,4 @@ public class PollerImplTest extends BrambleMockTestCase {
 		poller.eventOccurred(new TransportActiveEvent(transportId));
 		poller.eventOccurred(new TransportInactiveEvent(transportId));
 	}
-
-	private void expectReconnect(DuplexPlugin plugin,
-			DuplexTransportConnection duplexConnection) throws Exception {
-		context.checking(new Expectations() {{
-			// Get the plugin
-			oneOf(pluginManager).getPlugin(transportId);
-			will(returnValue(plugin));
-			// The plugin supports polling
-			oneOf(plugin).shouldPoll();
-			will(returnValue(true));
-			// Check whether the contact is already connected
-			oneOf(connectionRegistry).isConnected(contactId, transportId);
-			will(returnValue(false));
-			// Get the transport properties
-			oneOf(transportPropertyManager).getRemoteProperties(contactId,
-					transportId);
-			will(returnValue(properties));
-			// Connect to the contact
-			oneOf(plugin).createConnection(properties);
-			will(returnValue(duplexConnection));
-			// Pass the connection to the connection manager
-			oneOf(connectionManager).manageOutgoingConnection(contactId,
-					transportId, duplexConnection);
-		}});
-	}
 }

bramble-core/src/test/java/org/briarproject/bramble/plugin/tcp/LanTcpPluginTest.java

@@ -3,6 +3,7 @@ package org.briarproject.bramble.plugin.tcp;
 import org.briarproject.bramble.api.data.BdfList;
 import org.briarproject.bramble.api.keyagreement.KeyAgreementListener;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.Backoff;
 import org.briarproject.bramble.api.plugin.Plugin.State;
 import org.briarproject.bramble.api.plugin.PluginCallback;
 import org.briarproject.bramble.api.plugin.TransportConnectionReader;
@@ -41,6 +42,7 @@ import static org.junit.Assume.assumeTrue;
 
 public class LanTcpPluginTest extends BrambleTestCase {
 
+	private final Backoff backoff = new TestBackoff();
 	private final ExecutorService ioExecutor = newCachedThreadPool();
 
 	private Callback callback = null;
@@ -49,7 +51,7 @@ public class LanTcpPluginTest extends BrambleTestCase {
 	@Before
 	public void setUp() {
 		callback = new Callback();
-		plugin = new LanTcpPlugin(ioExecutor, callback, 0, 0, 0, 1000) {
+		plugin = new LanTcpPlugin(ioExecutor, backoff, callback, 0, 0, 1000) {
 			@Override
 			protected boolean canConnectToOwnAddress() {
 				return true;
@@ -345,4 +347,20 @@ public class LanTcpPluginTest extends BrambleTestCase {
 		public void handleWriter(TransportConnectionWriter w) {
 		}
 	}
+
+	private static class TestBackoff implements Backoff {
+
+		@Override
+		public int getPollingInterval() {
+			return 60 * 1000;
+		}
+
+		@Override
+		public void increment() {
+		}
+
+		@Override
+		public void reset() {
+		}
+	}
 }