Write any records in the queue before ending session.

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

@@ -12,6 +12,7 @@ import android.content.IntentFilter;
 import org.briarproject.bramble.api.io.TimeoutMonitor;
 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.PluginException;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
@@ -30,7 +31,6 @@ 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;
@@ -66,7 +66,6 @@ class AndroidBluetoothPlugin extends BluetoothPlugin<BluetoothServerSocket> {
 
 	private static final int MAX_DISCOVERY_MS = 10_000;
 
-	private final ScheduledExecutorService scheduler;
 	private final AndroidExecutor androidExecutor;
 	private final Context appContext;
 	private final Clock clock;
@@ -79,13 +78,11 @@ class AndroidBluetoothPlugin extends BluetoothPlugin<BluetoothServerSocket> {
 
 	AndroidBluetoothPlugin(BluetoothConnectionLimiter connectionLimiter,
 			TimeoutMonitor timeoutMonitor, Executor ioExecutor,
-			SecureRandom secureRandom, ScheduledExecutorService scheduler,
-			AndroidExecutor androidExecutor, Context appContext, Clock clock,
-			PluginCallback callback, int maxLatency, int maxIdleTime,
-			int pollingInterval) {
+			SecureRandom secureRandom, AndroidExecutor androidExecutor,
+			Context appContext, Clock clock, Backoff backoff,
+			PluginCallback callback, int maxLatency, int maxIdleTime) {
 		super(connectionLimiter, timeoutMonitor, ioExecutor, secureRandom,
-				callback, maxLatency, maxIdleTime, pollingInterval);
-		this.scheduler = scheduler;
+				backoff, callback, maxLatency, maxIdleTime);
 		this.androidExecutor = androidExecutor;
 		this.appContext = appContext;
 		this.clock = clock;
@@ -153,12 +150,6 @@ class AndroidBluetoothPlugin extends BluetoothPlugin<BluetoothServerSocket> {
 		wasEnabledByUs = true;
 	}
 
-	@Override
-	void onAdapterDisabled() {
-		super.onAdapterDisabled();
-		wasEnabledByUs = false;
-	}
-
 	@Override
 	@Nullable
 	String getBluetoothAddress() {
@@ -186,7 +177,7 @@ class AndroidBluetoothPlugin extends BluetoothPlugin<BluetoothServerSocket> {
 	private DuplexTransportConnection wrapSocket(BluetoothSocket s)
 			throws IOException {
 		return new AndroidBluetoothTransportConnection(this, connectionLimiter,
-				timeoutMonitor, appContext, scheduler, s);
+				timeoutMonitor, s);
 	}
 
 	@Override

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

@@ -5,6 +5,8 @@ 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 +16,42 @@ 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_IDLE_TIME = (int) SECONDS.toMillis(30);
-	private static final int POLLING_INTERVAL = (int) MINUTES.toMillis(2);
+	private static final int MAX_LATENCY = 30 * 1000; // 30 seconds
+	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
+	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) {
+			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 +67,13 @@ 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,
-				scheduler, androidExecutor, appContext, clock, callback,
-				MAX_LATENCY, MAX_IDLE_TIME, POLLING_INTERVAL);
+				androidExecutor, appContext, clock, backoff,
+				callback, MAX_LATENCY, MAX_IDLE_TIME);
 		eventBus.addListener(plugin);
 		return plugin;
 	}

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

@@ -1,26 +1,17 @@
 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
@@ -28,26 +19,18 @@ class AndroidBluetoothTransportConnection
 		extends AbstractDuplexTransportConnection {
 
 	private final BluetoothConnectionLimiter connectionLimiter;
-	private final RenewableWakeLock wakeLock;
 	private final BluetoothSocket socket;
 	private final InputStream in;
 
 	AndroidBluetoothTransportConnection(Plugin plugin,
 			BluetoothConnectionLimiter connectionLimiter,
-			TimeoutMonitor timeoutMonitor, Context appContext,
-			ScheduledExecutorService scheduler, BluetoothSocket socket)
+			TimeoutMonitor timeoutMonitor, BluetoothSocket socket)
 			throws IOException {
 		super(plugin);
 		this.connectionLimiter = connectionLimiter;
 		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);
 	}
@@ -67,7 +50,6 @@ class AndroidBluetoothTransportConnection
 		try {
 			socket.close();
 		} finally {
-			wakeLock.release();
 			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.event.EventListener;
 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;
@@ -34,21 +28,14 @@ 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 {
+class AndroidLanTcpPlugin extends LanTcpPlugin implements EventListener {
 
 	private static final Logger LOG =
 			getLogger(AndroidLanTcpPlugin.class.getName());
@@ -61,9 +48,9 @@ class AndroidLanTcpPlugin extends LanTcpPlugin {
 	private volatile SocketFactory socketFactory;
 
 	AndroidLanTcpPlugin(Executor ioExecutor, Context appContext,
-			PluginCallback callback, int maxLatency, int maxIdleTime,
-			int pollingInterval, int connectionTimeout) {
-		super(ioExecutor, callback, maxLatency, maxIdleTime, pollingInterval,
+			Backoff backoff, PluginCallback callback, int maxLatency,
+			int maxIdleTime, int connectionTimeout) {
+		super(ioExecutor, backoff, callback, maxLatency, maxIdleTime,
 				connectionTimeout);
 		// Don't execute more than one connection status check at a time
 		connectionStatusExecutor =
@@ -81,137 +68,37 @@ class AndroidLanTcpPlugin extends LanTcpPlugin {
 	public void start() {
 		if (used.getAndSet(true)) throw new IllegalStateException();
 		initialisePortProperty();
-		Settings settings = callback.getSettings();
-		state.setStarted(settings.getBoolean(PREF_PLUGIN_ENABLE,
-				DEFAULT_PREF_PLUGIN_ENABLE));
+		running = true;
 		updateConnectionStatus();
 	}
 
+	@Override
+	public void stop() {
+		running = false;
+		tryToClose(socket);
+	}
+
 	@Override
 	protected Socket createSocket() throws IOException {
 		return socketFactory.createSocket();
 	}
 
 	@Override
-	protected List<InetAddress> getUsableLocalInetAddresses(boolean ipv4) {
-		InetAddress addr = getWifiAddress(ipv4);
-		return addr == null ? emptyList() : singletonList(addr);
-	}
-
-	@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;
+	protected List<InetAddress> getUsableLocalInetAddresses() {
+		// If the device doesn't have wifi, don't open any sockets
+		if (wifiManager == null) return emptyList();
 		// 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 providing a normal access point, return its address
-		for (InterfaceAddress ifAddr : ifAddrs) {
-			if (isAndroidWifiApAddress(ifAddr)) {
-				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;
+		// If we're running an access point, return its address
+		for (InetAddress addr : getLocalInetAddresses()) {
+			if (addr.equals(WIFI_AP_ADDRESS)) return singletonList(addr);
+			if (addr.equals(WIFI_DIRECT_AP_ADDRESS)) return singletonList(addr);
 		}
+		// No suitable addresses
+		return emptyList();
 	}
 
 	private InetAddress intToInetAddress(int ip) {
@@ -233,11 +120,9 @@ class AndroidLanTcpPlugin extends LanTcpPlugin {
 	private SocketFactory getSocketFactory() {
 		if (SDK_INT < 21) return SocketFactory.getDefault();
 		for (Network net : connectivityManager.getAllNetworks()) {
-			NetworkCapabilities caps =
-					connectivityManager.getNetworkCapabilities(net);
-			if (caps != null && caps.hasTransport(TRANSPORT_WIFI)) {
+			NetworkInfo info = connectivityManager.getNetworkInfo(net);
+			if (info != null && info.getType() == TYPE_WIFI)
 				return net.getSocketFactory();
-			}
 		}
 		LOG.warning("Could not find suitable socket factory");
 		return SocketFactory.getDefault();
@@ -245,59 +130,31 @@ class AndroidLanTcpPlugin extends LanTcpPlugin {
 
 	@Override
 	public void eventOccurred(Event e) {
-		super.eventOccurred(e);
 		if (e instanceof NetworkStatusEvent) updateConnectionStatus();
 	}
 
 	private void updateConnectionStatus() {
 		connectionStatusExecutor.execute(() -> {
-			State s = getState();
-			if (s != ACTIVE && s != INACTIVE) return;
-			Pair<InetAddress, Boolean> wifi = getPreferredWifiAddress();
-			if (wifi == null) {
-				LOG.info("Not connected to wifi");
-				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()) {
+			if (!running) return;
+			List<InetAddress> addrs = getUsableLocalInetAddresses();
+			if (addrs.contains(WIFI_AP_ADDRESS)
+					|| addrs.contains(WIFI_DIRECT_AP_ADDRESS)) {
 				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
 				// make outgoing connections on API 21+ if another network
 				// has internet access
 				socketFactory = SocketFactory.getDefault();
-				if (s == INACTIVE) bind();
+				if (socket == null || socket.isClosed()) bind();
+			} else if (addrs.isEmpty()) {
+				LOG.info("Not connected to wifi");
+				socketFactory = SocketFactory.getDefault();
+				tryToClose(socket);
 			} else {
 				LOG.info("Connected to wifi");
 				socketFactory = getSocketFactory();
-				if (s == INACTIVE) bind();
+				if (socket == null || socket.isClosed()) bind();
 			}
 		});
 	}
-
-	/**
-	 * 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_IDLE_TIME = (int) SECONDS.toMillis(30);
-	private static final int POLLING_INTERVAL = (int) MINUTES.toMillis(1);
-	private static final int CONNECTION_TIMEOUT = (int) SECONDS.toMillis(3);
+	private static final int MAX_LATENCY = 30_000; // 30 seconds
+	private static final int MAX_IDLE_TIME = 30_000; // 30 seconds
+	private static final int CONNECTION_TIMEOUT = 3_000; // 3 seconds
+	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,
-				POLLING_INTERVAL, CONNECTION_TIMEOUT);
+				appContext, backoff, callback, MAX_LATENCY, MAX_IDLE_TIME,
+				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 stablePollingInterval) {
+			int maxIdleTime) {
 		super(ioExecutor, networkManager, locationUtils, torSocketFactory,
 				clock, resourceProvider, circumventionProvider, batteryManager,
-				torRendezvousCrypto, callback, architecture, maxLatency,
-				maxIdleTime, initialPollingInterval, stablePollingInterval,
+				backoff, torRendezvousCrypto, callback, architecture, maxLatency, maxIdleTime,
 				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
@@ -76,6 +74,7 @@ class AndroidTorPlugin extends TorPlugin {
 
 	@Override
 	protected void enableNetwork(boolean enable) throws IOException {
+		if (!running) return;
 		if (enable) wakeLock.acquire();
 		super.enableNetwork(enable);
 		if (!enable) wakeLock.release();
@@ -86,4 +85,17 @@ 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_IDLE_TIME = (int) SECONDS.toMillis(30);
-
-	/**
-	 * How often to poll before our hidden service becomes reachable.
-	 */
-	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 static final int MAX_LATENCY = 30 * 1000; // 30 seconds
+	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
+	private static final double BACKOFF_BASE = 1.2;
 
 	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,
-				MAX_IDLE_TIME, INITIAL_POLLING_INTERVAL,
-				STABLE_POLLING_INTERVAL);
+				backoff, torRendezvousCrypto, callback, architecture,
+				MAX_LATENCY, MAX_IDLE_TIME);
 		eventBus.addListener(plugin);
 		return plugin;
 	}

bramble-android/src/main/java/org/briarproject/bramble/system/AndroidLocationUtils.java

@@ -61,12 +61,12 @@ class AndroidLocationUtils implements LocationUtils {
 	private String getCountryFromPhoneNetwork() {
 		Object o = appContext.getSystemService(TELEPHONY_SERVICE);
 		TelephonyManager tm = (TelephonyManager) o;
-		return tm == null ? "" : tm.getNetworkCountryIso();
+		return tm.getNetworkCountryIso();
 	}
 
 	private String getCountryFromSimCard() {
 		Object o = appContext.getSystemService(TELEPHONY_SERVICE);
 		TelephonyManager tm = (TelephonyManager) o;
-		return tm == null ? "" : tm.getSimCountryIso();
+		return tm.getSimCountryIso();
 	}
 }

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

@@ -22,42 +22,14 @@ import java.util.Collection;
 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.
+	 * Registers a connection with the given contact over the given transport.
 	 * <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);
+	void registerConnection(ContactId c, TransportId t,
+			InterruptibleConnection conn, boolean incoming);
 
 	/**
 	 * Unregisters a connection with the given contact over the given transport.
@@ -71,8 +43,8 @@ public interface ConnectionRegistry {
 
 	/**
 	 * Sets the {@link Priority priority} of a connection that was previously
-	 * registered via {@link #registerIncomingConnection(ContactId, TransportId,
-	 * InterruptibleConnection)}.
+	 * registered via {@link #registerConnection(ContactId, TransportId,
+	 * InterruptibleConnection, boolean)}.
 	 * <p>
 	 * If the registry has any "better" connections with the given contact, the
 	 * given connection will be interrupted. If the registry has any "worse"

bramble-api/src/main/java/org/briarproject/bramble/api/event/EventBus.java

@@ -18,8 +18,6 @@ public interface EventBus {
 	/**
 	 * Asynchronously notifies all listeners of an event. Listeners are
 	 * notified on the {@link EventExecutor}.
-	 * <p>
-	 * This method can safely be called while holding a lock.
 	 */
 	void broadcast(Event e);
 }

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 +6,8 @@ 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;
+	String PREF_BT_ENABLE = "enable";
 }

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

@@ -3,55 +3,12 @@ package org.briarproject.bramble.api.plugin;
 import org.briarproject.bramble.api.Pair;
 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;
 
 @NotNullByDefault
 public interface Plugin {
 
-	enum State {
-
-		/**
-		 * The plugin has not finished starting or has been stopped.
-		 */
-		STARTING_STOPPING,
-
-		/**
-		 * The plugin is disabled by settings. Use {@link #getReasonsDisabled()}
-		 * to find out which settings are responsible.
-		 */
-		DISABLED,
-
-		/**
-		 * The plugin is being enabled and can't yet make or receive
-		 * connections.
-		 */
-		ENABLING,
-
-		/**
-		 * The plugin is enabled and can make or receive connections.
-		 */
-		ACTIVE,
-
-		/**
-		 * The plugin is enabled but can't make or receive connections
-		 */
-		INACTIVE
-	}
-
-	/**
-	 * The string for the boolean preference
-	 * to use with the {@link SettingsManager} to enable or disable the plugin.
-	 */
-	String PREF_PLUGIN_ENABLE = "enable";
-
-	/**
-	 * Reason flag returned by {@link #getReasonsDisabled()} to indicate that
-	 * the plugin has been disabled by the user.
-	 */
-	int REASON_USER = 1;
-
 	/**
 	 * Returns the plugin's transport identifier.
 	 */
@@ -78,18 +35,9 @@ public interface Plugin {
 	void stop() throws PluginException;
 
 	/**
-	 * Returns the current state of the plugin.
+	 * Returns true if the plugin is running.
 	 */
-	State getState();
-
-	/**
-	 * Returns a set of flags indicating why the plugin is
-	 * {@link State#DISABLED disabled}, or 0 if the plugin is not disabled.
-	 * <p>
-	 * The flags used are plugin-specific, except the generic flag
-	 * {@link #REASON_USER}, which may be used by any plugin.
-	 */
-	int getReasonsDisabled();
+	boolean isRunning();
 
 	/**
 	 * Returns true if the plugin should be polled periodically to attempt to

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

@@ -1,10 +1,6 @@
 package org.briarproject.bramble.api.plugin;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.plugin.Plugin.State;
-import org.briarproject.bramble.api.plugin.event.TransportActiveEvent;
-import org.briarproject.bramble.api.plugin.event.TransportInactiveEvent;
-import org.briarproject.bramble.api.plugin.event.TransportStateEvent;
 import org.briarproject.bramble.api.properties.TransportProperties;
 import org.briarproject.bramble.api.settings.Settings;
 
@@ -36,17 +32,12 @@ public interface PluginCallback extends ConnectionHandler {
 	void mergeLocalProperties(TransportProperties p);
 
 	/**
-	 * Informs the callback of the plugin's current state.
-	 * <p>
-	 * If the current state is different from the previous state, the callback
-	 * will broadcast a {@link TransportStateEvent}. If the current state is
-	 * {@link State#ACTIVE} and the previous state was not
-	 * {@link State#ACTIVE}, the callback will broadcast a
-	 * {@link TransportActiveEvent}. If the current state is not
-	 * {@link State#ACTIVE} and the previous state was {@link State#ACTIVE},
-	 * the callback will broadcast a {@link TransportInactiveEvent}.
-	 * <p>
-	 * This method can safely be called while holding a lock.
+	 * Signals that the transport is enabled.
 	 */
-	void pluginStateChanged(State state);
+	void transportEnabled();
+
+	/**
+	 * Signals that the transport is disabled.
+	 */
+	void transportDisabled();
 }

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

@@ -41,17 +41,4 @@ public interface PluginManager {
 	 * Returns any duplex plugins that support rendezvous.
 	 */
 	Collection<DuplexPlugin> getRendezvousPlugins();
-
-	/**
-	 * Enables or disables the plugin
-	 * identified by the given {@link TransportId}.
-	 * <p>
-	 * Note that this applies the change asynchronously
-	 * and there are no order guarantees.
-	 * <p>
-	 * If no plugin with the given {@link TransportId} is registered,
-	 * this is a no-op.
-	 */
-	void setPluginEnabled(TransportId t, boolean enabled);
-
 }

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";
 
@@ -16,45 +13,14 @@ 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()}.
-	 */
-	int REASON_BATTERY = 2;
-
-	/**
-	 * Reason flag returned by {@link Plugin#getReasonsDisabled()}.
-	 */
-	int REASON_MOBILE_DATA = 4;
-
-	/**
-	 * Reason flag returned by {@link Plugin#getReasonsDisabled()}.
-	 */
-	int REASON_COUNTRY_BLOCKED = 8;
 }

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/event/TransportDisabledEvent.java

@@ -2,22 +2,20 @@ package org.briarproject.bramble.api.plugin.event;
 
 import org.briarproject.bramble.api.event.Event;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.plugin.Plugin.State;
 import org.briarproject.bramble.api.plugin.TransportId;
 
 import javax.annotation.concurrent.Immutable;
 
 /**
- * An event that is broadcast when a plugin enters the {@link State#ACTIVE}
- * state.
+ * An event that is broadcast when a transport is disabled.
  */
 @Immutable
 @NotNullByDefault
-public class TransportActiveEvent extends Event {
+public class TransportDisabledEvent extends Event {
 
 	private final TransportId transportId;
 
-	public TransportActiveEvent(TransportId transportId) {
+	public TransportDisabledEvent(TransportId transportId) {
 		this.transportId = transportId;
 	}
 

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

@@ -2,22 +2,20 @@ package org.briarproject.bramble.api.plugin.event;
 
 import org.briarproject.bramble.api.event.Event;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.plugin.Plugin.State;
 import org.briarproject.bramble.api.plugin.TransportId;
 
 import javax.annotation.concurrent.Immutable;
 
 /**
- * An event that is broadcast when a plugin leaves the {@link State#ACTIVE}
- * state.
+ * An event that is broadcast when a transport is enabled.
  */
 @Immutable
 @NotNullByDefault
-public class TransportInactiveEvent extends Event {
+public class TransportEnabledEvent extends Event {
 
 	private final TransportId transportId;
 
-	public TransportInactiveEvent(TransportId transportId) {
+	public TransportEnabledEvent(TransportId transportId) {
 		this.transportId = transportId;
 	}
 

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

@@ -1,32 +0,0 @@
-package org.briarproject.bramble.api.plugin.event;
-
-import org.briarproject.bramble.api.event.Event;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.plugin.Plugin.State;
-import org.briarproject.bramble.api.plugin.TransportId;
-
-import javax.annotation.concurrent.Immutable;
-
-/**
- * An event that is broadcast when the {@link State state} of a plugin changes.
- */
-@Immutable
-@NotNullByDefault
-public class TransportStateEvent extends Event {
-
-	private final TransportId transportId;
-	private final State state;
-
-	public TransportStateEvent(TransportId transportId, State state) {
-		this.transportId = transportId;
-		this.state = state;
-	}
-
-	public TransportId getTransportId() {
-		return transportId;
-	}
-
-	public State getState() {
-		return state;
-	}
-}

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

@@ -2,7 +2,6 @@ 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;
@@ -15,10 +14,10 @@ public interface SyncSessionFactory {
 	SyncSession createIncomingSession(ContactId c, InputStream in,
 			PriorityHandler handler);
 
-	SyncSession createSimplexOutgoingSession(ContactId c, TransportId t,
-			int maxLatency, StreamWriter streamWriter);
+	SyncSession createSimplexOutgoingSession(ContactId c, int maxLatency,
+			StreamWriter streamWriter);
 
-	SyncSession createDuplexOutgoingSession(ContactId c, TransportId t,
-			int maxLatency, int maxIdleTime, StreamWriter streamWriter,
+	SyncSession createDuplexOutgoingSession(ContactId c, int maxLatency,
+			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/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 local IPv4 addresses
-			if (address.isLoopbackAddress() || address.isLinkLocalAddress() ||
-					address.isSiteLocalAddress()) {
-				return address.getHostAddress();
-			}
-			// Keep first and last octet of non-local IPv4 addresses
-			return scrubIpv4Address(address.getAddress());
-		} else {
-			// Keep first and last octet of IPv6 addresses
-			return scrubIpv6Address(address.getAddress());
-		}
+		// don't scrub link and site local addresses
+		if (address.isLinkLocalAddress() || address.isSiteLocalAddress())
+			return address.toString();
+		// completely scrub IPv6 addresses
+		if (address instanceof Inet6Address) return "[scrubbed]";
+		// keep first and last octet of IPv4 addresses
+		return scrubInetAddress(address.toString());
 	}
 
-	private static String scrubIpv4Address(byte[] ipv4) {
-		return (ipv4[0] & 0xFF) + ".[scrubbed]." + (ipv4[3] & 0xFF);
-	}
-
-	private static String scrubIpv6Address(byte[] ipv6) {
-		String hex = toHexString(ipv6).toLowerCase();
-		return hex.substring(0, 2) + "[scrubbed]" + hex.substring(30);
+	@Nullable
+	public static String scrubInetAddress(@Nullable String address) {
+		if (address == null) return null;
+
+		int firstDot = address.indexOf(".");
+		if (firstDot == -1) return "[scrubbed]";
+		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/connection/ConnectionRegistryImpl.java

@@ -61,19 +61,7 @@ class ConnectionRegistryImpl implements ConnectionRegistry {
 	}
 
 	@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,
+	public void registerConnection(ContactId c, TransportId t,
 			InterruptibleConnection conn, boolean incoming) {
 		if (LOG.isLoggable(INFO)) {
 			if (incoming) LOG.info("Incoming connection registered: " + t);
@@ -226,8 +214,7 @@ class ConnectionRegistryImpl implements ConnectionRegistry {
 	@Override
 	public boolean isConnected(ContactId c) {
 		synchronized (lock) {
-			List<ConnectionRecord> recs = contactConnections.get(c);
-			return recs != null && !recs.isEmpty();
+			return contactConnections.containsKey(c);
 		}
 	}
 

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

@@ -47,24 +47,20 @@ abstract class DuplexSyncConnection extends SyncConnection
 
 	@Override
 	public void interruptOutgoingSession() {
-		SyncSession out = null;
 		synchronized (interruptLock) {
 			if (outgoingSession == null) interruptWaiting = true;
-			else out = outgoingSession;
+			else outgoingSession.interrupt();
 		}
-		if (out != null) out.interrupt();
 	}
 
 	void setOutgoingSession(SyncSession outgoingSession) {
-		boolean interruptWasWaiting = false;
 		synchronized (interruptLock) {
 			this.outgoingSession = outgoingSession;
 			if (interruptWaiting) {
-				interruptWasWaiting = true;
+				outgoingSession.interrupt();
 				interruptWaiting = false;
 			}
 		}
-		if (interruptWasWaiting) outgoingSession.interrupt();
 	}
 
 	DuplexSyncConnection(KeyManager keyManager,
@@ -103,7 +99,6 @@ abstract class DuplexSyncConnection extends SyncConnection
 				w.getOutputStream(), ctx);
 		ContactId c = requireNonNull(ctx.getContactId());
 		return syncSessionFactory.createDuplexOutgoingSession(c,
-				ctx.getTransportId(), w.getMaxLatency(), w.getMaxIdleTime(),
-				streamWriter, priority);
+				w.getMaxLatency(), w.getMaxIdleTime(), streamWriter, priority);
 	}
 }

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

@@ -59,8 +59,8 @@ class IncomingDuplexSyncConnection extends DuplexSyncConnection
 			onReadError(true);
 			return;
 		}
-		connectionRegistry.registerIncomingConnection(contactId, transportId,
-				this);
+		connectionRegistry.registerConnection(contactId, transportId,
+				this, true);
 		// Start the outgoing session on another thread
 		ioExecutor.execute(() -> runOutgoingSession(contactId));
 		try {

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

@@ -104,8 +104,9 @@ class OutgoingDuplexSyncConnection extends DuplexSyncConnection
 			onReadError();
 			return;
 		}
-		connectionRegistry.registerOutgoingConnection(contactId, transportId,
-				this, priority);
+		connectionRegistry.registerConnection(contactId, transportId,
+				this, false);
+		connectionRegistry.setPriority(contactId, transportId, this, priority);
 		try {
 			// Store any transport properties discovered from the connection
 			transportPropertyManager.addRemotePropertiesFromConnection(

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

@@ -72,7 +72,7 @@ class OutgoingSimplexSyncConnection extends SyncConnection implements Runnable {
 				w.getOutputStream(), ctx);
 		ContactId c = requireNonNull(ctx.getContactId());
 		return syncSessionFactory.createSimplexOutgoingSession(c,
-				ctx.getTransportId(), w.getMaxLatency(), streamWriter);
+				w.getMaxLatency(), streamWriter);
 	}
 }
 

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/PluginManagerImpl.java

@@ -8,7 +8,6 @@ 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.Plugin;
-import org.briarproject.bramble.api.plugin.Plugin.State;
 import org.briarproject.bramble.api.plugin.PluginCallback;
 import org.briarproject.bramble.api.plugin.PluginConfig;
 import org.briarproject.bramble.api.plugin.PluginException;
@@ -19,9 +18,8 @@ import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPluginFactory;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
-import org.briarproject.bramble.api.plugin.event.TransportActiveEvent;
-import org.briarproject.bramble.api.plugin.event.TransportInactiveEvent;
-import org.briarproject.bramble.api.plugin.event.TransportStateEvent;
+import org.briarproject.bramble.api.plugin.event.TransportDisabledEvent;
+import org.briarproject.bramble.api.plugin.event.TransportEnabledEvent;
 import org.briarproject.bramble.api.plugin.simplex.SimplexPlugin;
 import org.briarproject.bramble.api.plugin.simplex.SimplexPluginFactory;
 import org.briarproject.bramble.api.properties.TransportProperties;
@@ -38,7 +36,6 @@ import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.Executor;
 import java.util.concurrent.atomic.AtomicBoolean;
-import java.util.concurrent.atomic.AtomicReference;
 import java.util.logging.Logger;
 
 import javax.annotation.concurrent.ThreadSafe;
@@ -48,9 +45,6 @@ import static java.util.logging.Level.FINE;
 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.plugin.Plugin.PREF_PLUGIN_ENABLE;
-import static org.briarproject.bramble.api.plugin.Plugin.State.ACTIVE;
-import static org.briarproject.bramble.api.plugin.Plugin.State.STARTING_STOPPING;
 import static org.briarproject.bramble.util.LogUtils.logDuration;
 import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.bramble.util.LogUtils.now;
@@ -183,26 +177,6 @@ class PluginManagerImpl implements PluginManager, Service {
 		return supported;
 	}
 
-	@Override
-	public void setPluginEnabled(TransportId t, boolean enabled) {
-		Plugin plugin = plugins.get(t);
-		if (plugin == null) return;
-
-		Settings s = new Settings();
-		s.putBoolean(PREF_PLUGIN_ENABLE, enabled);
-		ioExecutor.execute(() -> mergeSettings(s, t.getString()));
-	}
-
-	private void mergeSettings(Settings s, String namespace) {
-		try {
-			long start = now();
-			settingsManager.mergeSettings(s, namespace);
-			logDuration(LOG, "Merging settings", start);
-		} catch (DbException e) {
-			logException(LOG, WARNING, e);
-		}
-	}
-
 	private class PluginStarter implements Runnable {
 
 		private final Plugin plugin;
@@ -276,8 +250,7 @@ class PluginManagerImpl implements PluginManager, Service {
 	private class Callback implements PluginCallback {
 
 		private final TransportId id;
-		private final AtomicReference<State> state =
-				new AtomicReference<>(STARTING_STOPPING);
+		private final AtomicBoolean enabled = new AtomicBoolean(false);
 
 		private Callback(TransportId id) {
 			this.id = id;
@@ -305,7 +278,11 @@ class PluginManagerImpl implements PluginManager, Service {
 
 		@Override
 		public void mergeSettings(Settings s) {
-			PluginManagerImpl.this.mergeSettings(s, id.getString());
+			try {
+				settingsManager.mergeSettings(s, id.getString());
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+			}
 		}
 
 		@Override
@@ -318,20 +295,15 @@ class PluginManagerImpl implements PluginManager, Service {
 		}
 
 		@Override
-		public void pluginStateChanged(State newState) {
-			State oldState = state.getAndSet(newState);
-			if (newState != oldState) {
-				if (LOG.isLoggable(INFO)) {
-					LOG.info(id + " changed from state " + oldState
-							+ " to " + newState);
-				}
-				eventBus.broadcast(new TransportStateEvent(id, newState));
-				if (newState == ACTIVE) {
-					eventBus.broadcast(new TransportActiveEvent(id));
-				} else if (oldState == ACTIVE) {
-					eventBus.broadcast(new TransportInactiveEvent(id));
-				}
-			}
+		public void transportEnabled() {
+			if (!enabled.getAndSet(true))
+				eventBus.broadcast(new TransportEnabledEvent(id));
+		}
+
+		@Override
+		public void transportDisabled() {
+			if (enabled.getAndSet(false))
+				eventBus.broadcast(new TransportDisabledEvent(id));
 		}
 
 		@Override

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

@@ -2,6 +2,7 @@ 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.PluginConfig;
 import org.briarproject.bramble.api.plugin.PluginManager;
 
@@ -21,6 +22,11 @@ public class PluginModule {
 		Poller poller;
 	}
 
+	@Provides
+	BackoffFactory provideBackoffFactory() {
+		return new BackoffFactoryImpl();
+	}
+
 	@Provides
 	@Singleton
 	PluginManager providePluginManager(LifecycleManager lifecycleManager,

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

@@ -19,8 +19,9 @@ 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.TransportActiveEvent;
-import org.briarproject.bramble.api.plugin.event.TransportInactiveEvent;
+import org.briarproject.bramble.api.plugin.event.ConnectionOpenedEvent;
+import org.briarproject.bramble.api.plugin.event.TransportDisabledEvent;
+import org.briarproject.bramble.api.plugin.event.TransportEnabledEvent;
 import org.briarproject.bramble.api.plugin.simplex.SimplexPlugin;
 import org.briarproject.bramble.api.properties.TransportProperties;
 import org.briarproject.bramble.api.properties.TransportPropertyManager;
@@ -95,17 +96,23 @@ class PollerImpl implements Poller, EventListener {
 			connectToContact(c.getContactId());
 		} else if (e instanceof ConnectionClosedEvent) {
 			ConnectionClosedEvent c = (ConnectionClosedEvent) e;
+			// Reschedule polling, the polling interval may have decreased
+			reschedule(c.getTransportId());
 			// If an outgoing connection failed, try to reconnect
 			if (!c.isIncoming() && c.isException()) {
 				connectToContact(c.getContactId(), c.getTransportId());
 			}
-		} else if (e instanceof TransportActiveEvent) {
-			TransportActiveEvent t = (TransportActiveEvent) e;
-			// Poll the newly activated transport
+		} else if (e instanceof ConnectionOpenedEvent) {
+			ConnectionOpenedEvent c = (ConnectionOpenedEvent) e;
+			// Reschedule polling, the polling interval may have decreased
+			reschedule(c.getTransportId());
+		} else if (e instanceof TransportEnabledEvent) {
+			TransportEnabledEvent t = (TransportEnabledEvent) e;
+			// Poll the newly enabled transport
 			pollNow(t.getTransportId());
-		} else if (e instanceof TransportInactiveEvent) {
-			TransportInactiveEvent t = (TransportInactiveEvent) e;
-			// Cancel polling for the deactivated transport
+		} else if (e instanceof TransportDisabledEvent) {
+			TransportDisabledEvent t = (TransportDisabledEvent) e;
+			// Cancel polling for the disabled transport
 			cancel(t.getTransportId());
 		}
 	}
@@ -157,6 +164,12 @@ 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

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 org.briarproject.bramble.api.plugin.BluetoothConstants.ID;
+import static java.util.logging.Level.WARNING;
+import static org.briarproject.bramble.util.LogUtils.logException;
 
 @NotNullByDefault
 @ThreadSafe
 class BluetoothConnectionLimiterImpl implements BluetoothConnectionLimiter {
 
 	private static final Logger LOG =
-			getLogger(BluetoothConnectionLimiterImpl.class.getName());
-
-	private final EventBus eventBus;
+			Logger.getLogger(BluetoothConnectionLimiterImpl.class.getName());
 
 	private final Object lock = new Object();
-	@GuardedBy("lock")
-	private final List<DuplexTransportConnection> connections =
+	// The following are locking: lock
+	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");
-		eventBus.broadcast(new CloseSyncConnectionsEvent(ID));
+		if (LOG.isLoggable(INFO)) {
+			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 (LOG.isLoggable(INFO)) {
-				LOG.info("Connection opened, " + connections.size() + " open");
+			if (keyAgreementInProgress) {
+				LOG.info("Refusing contact connection during key agreement");
+				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

@@ -10,10 +10,9 @@ import org.briarproject.bramble.api.keyagreement.KeyAgreementConnection;
 import org.briarproject.bramble.api.keyagreement.KeyAgreementListener;
 import org.briarproject.bramble.api.keyagreement.event.KeyAgreementListeningEvent;
 import org.briarproject.bramble.api.keyagreement.event.KeyAgreementStoppedListeningEvent;
-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.PluginCallback;
 import org.briarproject.bramble.api.plugin.PluginException;
@@ -38,22 +37,16 @@ import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.logging.Logger;
 
 import javax.annotation.Nullable;
-import javax.annotation.concurrent.GuardedBy;
-import javax.annotation.concurrent.ThreadSafe;
 
 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.PREF_BT_ENABLE;
 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.api.plugin.BluetoothConstants.UUID_BYTES;
-import static org.briarproject.bramble.api.plugin.Plugin.State.ACTIVE;
-import static org.briarproject.bramble.api.plugin.Plugin.State.DISABLED;
-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.util.LogUtils.logException;
 import static org.briarproject.bramble.util.PrivacyUtils.scrubMacAddress;
 import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
@@ -72,13 +65,14 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 
 	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, maxIdleTime;
 	private final AtomicBoolean used = new AtomicBoolean(false);
 
-	protected final PluginState state = new PluginState();
-
+	private volatile boolean running = false, contactConnections = false;
 	private volatile String contactConnectionsUuid = null;
+	private volatile SS socket = null;
 
 	abstract void initialiseAdapter() throws IOException;
 
@@ -114,34 +108,30 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 
 	BluetoothPlugin(BluetoothConnectionLimiter connectionLimiter,
 			TimeoutMonitor timeoutMonitor, Executor ioExecutor,
-			SecureRandom secureRandom, PluginCallback callback, int maxLatency, int maxIdleTime,
-			int pollingInterval) {
+			SecureRandom secureRandom, Backoff backoff,
+			PluginCallback callback, int maxLatency, int maxIdleTime) {
 		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() {
 		LOG.info("Bluetooth enabled");
 		// We may not have been able to get the local address before
 		ioExecutor.execute(this::updateProperties);
-		if (getState() == INACTIVE) bind();
+		if (shouldAllowContactConnections()) bind();
 	}
 
 	void onAdapterDisabled() {
 		LOG.info("Bluetooth disabled");
+		tryToClose(socket);
 		connectionLimiter.allConnectionsClosed();
-		// The server socket may not have been closed automatically
-		SS ss = state.clearServerSocket();
-		if (ss != null) {
-			LOG.info("Closing server socket");
-			tryToClose(ss);
-		}
+		callback.transportDisabled();
 	}
 
 	@Override
@@ -162,25 +152,31 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 	@Override
 	public void start() throws PluginException {
 		if (used.getAndSet(true)) throw new IllegalStateException();
-		Settings settings = callback.getSettings();
-		boolean enabledByUser = settings.getBoolean(PREF_PLUGIN_ENABLE,
-				DEFAULT_PREF_PLUGIN_ENABLE);
-		state.setStarted(enabledByUser);
 		try {
 			initialiseAdapter();
 		} catch (IOException e) {
 			throw new PluginException(e);
 		}
 		updateProperties();
-		if (enabledByUser) {
+		running = true;
+		loadSettings(callback.getSettings());
+		if (shouldAllowContactConnections()) {
 			if (isAdapterEnabled()) bind();
 			else enableAdapter();
 		}
 	}
 
+	private void loadSettings(Settings settings) {
+		contactConnections = settings.getBoolean(PREF_BT_ENABLE, false);
+	}
+
+	private boolean shouldAllowContactConnections() {
+		return contactConnections;
+	}
+
 	private void bind() {
 		ioExecutor.execute(() -> {
-			if (getState() != INACTIVE) return;
+			if (!isRunning() || !shouldAllowContactConnections()) return;
 			// Bind a server socket to accept connections from contacts
 			SS ss;
 			try {
@@ -189,12 +185,14 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 				logException(LOG, WARNING, e);
 				return;
 			}
-			if (!state.setServerSocket(ss)) {
-				LOG.info("Closing redundant server socket");
+			if (!isRunning() || !shouldAllowContactConnections()) {
 				tryToClose(ss);
 				return;
 			}
-			acceptContactConnections(ss);
+			socket = ss;
+			backoff.reset();
+			callback.transportEnabled();
+			acceptContactConnections();
 		});
 	}
 
@@ -223,38 +221,36 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 		if (changed) callback.mergeLocalProperties(p);
 	}
 
-	private void acceptContactConnections(SS ss) {
+	private void acceptContactConnections() {
 		while (true) {
 			DuplexTransportConnection conn;
 			try {
-				conn = acceptConnection(ss);
+				conn = acceptConnection(socket);
 			} catch (IOException e) {
-				// This is expected when the server socket is closed
-				LOG.info("Server socket closed");
-				state.clearServerSocket();
+				// This is expected when the socket is closed
+				if (LOG.isLoggable(INFO)) LOG.info(e.toString());
 				return;
 			}
 			LOG.info("Connection received");
-			connectionLimiter.connectionOpened(conn);
-			callback.handleConnection(conn);
+			if (connectionLimiter.contactConnectionOpened(conn)) {
+				backoff.reset();
+				callback.handleConnection(conn);
+			}
+			if (!running) return;
 		}
 	}
 
 	@Override
 	public void stop() {
-		SS ss = state.setStopped();
-		tryToClose(ss);
+		running = false;
+		tryToClose(socket);
+		callback.transportDisabled();
 		disableAdapterIfEnabledByUs();
 	}
 
 	@Override
-	public State getState() {
-		return state.getState();
-	}
-
-	@Override
-	public int getReasonsDisabled() {
-		return state.getReasonsDisabled();
+	public boolean isRunning() {
+		return running && isAdapterEnabled();
 	}
 
 	@Override
@@ -264,13 +260,14 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 
 	@Override
 	public int getPollingInterval() {
-		return pollingInterval;
+		return backoff.getPollingInterval();
 	}
 
 	@Override
 	public void poll(Collection<Pair<TransportProperties, ConnectionHandler>>
 			properties) {
-		if (getState() != ACTIVE) return;
+		if (!isRunning() || !shouldAllowContactConnections()) return;
+		backoff.increment();
 		for (Pair<TransportProperties, ConnectionHandler> p : properties) {
 			connect(p.getFirst(), p.getSecond());
 		}
@@ -283,7 +280,10 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 		if (isNullOrEmpty(uuid)) return;
 		ioExecutor.execute(() -> {
 			DuplexTransportConnection d = createConnection(p);
-			if (d != null) h.handleConnection(d);
+			if (d != null) {
+				backoff.reset();
+				h.handleConnection(d);
+			}
 		});
 	}
 
@@ -320,15 +320,15 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 
 	@Override
 	public DuplexTransportConnection createConnection(TransportProperties p) {
-		if (getState() != ACTIVE) return null;
+		if (!isRunning() || !shouldAllowContactConnections()) return null;
 		if (!connectionLimiter.canOpenContactConnection()) return null;
 		String address = p.get(PROP_ADDRESS);
 		if (isNullOrEmpty(address)) return null;
 		String uuid = p.get(PROP_UUID);
 		if (isNullOrEmpty(uuid)) return null;
 		DuplexTransportConnection conn = connect(address, uuid);
-		if (conn != null) connectionLimiter.connectionOpened(conn);
-		return conn;
+		if (conn == null) return null;
+		return connectionLimiter.contactConnectionOpened(conn) ? conn : null;
 	}
 
 	@Override
@@ -338,7 +338,7 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 
 	@Override
 	public KeyAgreementListener createKeyAgreementListener(byte[] commitment) {
-		if (getState() != ACTIVE) return null;
+		if (!isRunning()) return null;
 		// No truncation necessary because COMMIT_LENGTH = 16
 		String uuid = UUID.nameUUIDFromBytes(commitment).toString();
 		if (LOG.isLoggable(INFO)) LOG.info("Key agreement UUID " + uuid);
@@ -350,7 +350,7 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 			logException(LOG, WARNING, e);
 			return null;
 		}
-		if (getState() != ACTIVE) {
+		if (!isRunning()) {
 			tryToClose(ss);
 			return null;
 		}
@@ -364,7 +364,7 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 	@Override
 	public DuplexTransportConnection createKeyAgreementConnection(
 			byte[] commitment, BdfList descriptor) {
-		if (getState() != ACTIVE) return null;
+		if (!isRunning()) return null;
 		// No truncation necessary because COMMIT_LENGTH = 16
 		String uuid = UUID.nameUUIDFromBytes(commitment).toString();
 		DuplexTransportConnection conn;
@@ -384,7 +384,7 @@ 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;
 	}
 
@@ -424,18 +424,17 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 		}
 	}
 
-	@IoExecutor
 	private void onSettingsUpdated(Settings settings) {
-		boolean enabledByUser = settings.getBoolean(PREF_PLUGIN_ENABLE,
-				DEFAULT_PREF_PLUGIN_ENABLE);
-		SS ss = state.setEnabledByUser(enabledByUser);
-		State s = getState();
-		if (ss != null) {
-			LOG.info("Disabled by user, closing server socket");
-			tryToClose(ss);
+		boolean wasAllowed = shouldAllowContactConnections();
+		loadSettings(settings);
+		boolean isAllowed = shouldAllowContactConnections();
+		if (wasAllowed && !isAllowed) {
+			LOG.info("Contact connections disabled");
+			tryToClose(socket);
+			callback.transportDisabled();
 			disableAdapterIfEnabledByUs();
-		} else if (s == INACTIVE) {
-			LOG.info("Enabled by user, opening server socket");
+		} else if (!wasAllowed && isAllowed) {
+			LOG.info("Contact connections enabled");
 			if (isAdapterEnabled()) bind();
 			else enableAdapter();
 		}
@@ -454,7 +453,7 @@ 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);
 		}
 
@@ -463,70 +462,4 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 			tryToClose(ss);
 		}
 	}
-
-	@ThreadSafe
-	@NotNullByDefault
-	protected class PluginState {
-
-		@GuardedBy("this")
-		private boolean started = false,
-				stopped = false,
-				enabledByUser = false;
-
-		@GuardedBy("this")
-		@Nullable
-		private SS serverSocket = null;
-
-		synchronized void setStarted(boolean enabledByUser) {
-			started = true;
-			this.enabledByUser = enabledByUser;
-			callback.pluginStateChanged(getState());
-		}
-
-		@Nullable
-		synchronized SS setStopped() {
-			stopped = true;
-			SS ss = serverSocket;
-			serverSocket = null;
-			callback.pluginStateChanged(getState());
-			return ss;
-		}
-
-		@Nullable
-		synchronized SS setEnabledByUser(boolean enabledByUser) {
-			this.enabledByUser = enabledByUser;
-			SS ss = null;
-			if (!enabledByUser) {
-				ss = serverSocket;
-				serverSocket = null;
-			}
-			callback.pluginStateChanged(getState());
-			return ss;
-		}
-
-		synchronized boolean setServerSocket(SS ss) {
-			if (stopped || serverSocket != null) return false;
-			serverSocket = ss;
-			callback.pluginStateChanged(getState());
-			return true;
-		}
-
-		@Nullable
-		synchronized SS clearServerSocket() {
-			SS ss = serverSocket;
-			serverSocket = null;
-			callback.pluginStateChanged(getState());
-			return ss;
-		}
-
-		synchronized State getState() {
-			if (!started || stopped) return STARTING_STOPPING;
-			if (!enabledByUser) return DISABLED;
-			return serverSocket == null ? INACTIVE : ACTIVE;
-		}
-
-		synchronized int getReasonsDisabled() {
-			return getState() == DISABLED ? REASON_USER : 0;
-		}
-	}
 }

bramble-core/src/main/java/org/briarproject/bramble/plugin/file/FilePlugin.java

@@ -16,7 +16,6 @@ import java.util.logging.Logger;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.api.plugin.FileConstants.PROP_PATH;
-import static org.briarproject.bramble.api.plugin.Plugin.State.ACTIVE;
 import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
 
@@ -46,7 +45,7 @@ abstract class FilePlugin implements SimplexPlugin {
 
 	@Override
 	public TransportConnectionReader createReader(TransportProperties p) {
-		if (getState() != ACTIVE) return null;
+		if (!isRunning()) return null;
 		String path = p.get(PROP_PATH);
 		if (isNullOrEmpty(path)) return null;
 		try {
@@ -61,7 +60,7 @@ abstract class FilePlugin implements SimplexPlugin {
 
 	@Override
 	public TransportConnectionWriter createWriter(TransportProperties p) {
-		if (getState() != ACTIVE) return null;
+		if (!isRunning()) return null;
 		String path = p.get(PROP_PATH);
 		if (isNullOrEmpty(path)) return null;
 		try {

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

@@ -5,15 +5,16 @@ 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;
 import org.briarproject.bramble.api.properties.TransportProperties;
 import org.briarproject.bramble.api.settings.Settings;
+import org.briarproject.bramble.util.IoUtils;
 
 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 +22,8 @@ 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 +31,38 @@ 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,
-			int maxIdleTime, int pollingInterval, int connectionTimeout) {
-		super(ioExecutor, callback, maxLatency, maxIdleTime, pollingInterval,
+	LanTcpPlugin(Executor ioExecutor, Backoff backoff, PluginCallback callback,
+			int maxLatency, int maxIdleTime, int connectionTimeout) {
+		super(ioExecutor, backoff, callback, maxLatency, maxIdleTime,
 				connectionTimeout);
 	}
 
@@ -102,36 +91,29 @@ class LanTcpPlugin extends TcpPlugin {
 	public void start() {
 		if (used.getAndSet(true)) throw new IllegalStateException();
 		initialisePortProperty();
-		Settings settings = callback.getSettings();
-		state.setStarted(settings.getBoolean(PREF_PLUGIN_ENABLE,
-				DEFAULT_PREF_PLUGIN_ENABLE));
+		running = true;
 		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() {
-		return DEFAULT_PREF_PLUGIN_ENABLE;
-	}
-
-	@Override
-	protected List<InetSocketAddress> getLocalSocketAddresses(boolean ipv4) {
+	protected List<InetSocketAddress> getLocalSocketAddresses() {
 		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 +139,17 @@ 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 +158,50 @@ 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) {
-		if (ipv4) setLocalIpv4SocketAddress(a);
-		else setLocalIpv6SocketAddress(a);
-	}
-
-	private void setLocalIpv4SocketAddress(InetSocketAddress a) {
+	protected void setLocalSocketAddress(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);
-		Deque<String> recent = new LinkedList<>();
-		if (!isNullOrEmpty(setting)) {
+		String setting = callback.getSettings().get(PREF_LAN_IP_PORTS);
+		List<String> recent = new ArrayList<>();
+		if (!isNullOrEmpty(setting))
 			addAll(recent, setting.split(SEPARATOR));
-		}
-		if (recent.remove(item)) {
-			// Move the item to the start of the list
-			recent.addFirst(item);
+		// Is the address already in the list?
+		if (recent.remove(ipPort)) {
+			// Move the address to the start of the list
+			recent.add(0, ipPort);
 			setting = join(recent, SEPARATOR);
 		} else {
-			// Add the item to the start of the list
-			recent.addFirst(item);
-			// Drop items from the end of the list if it's too long to encode
+			// Add the address to the start of the list
+			recent.add(0, ipPort);
+			// 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 +216,20 @@ class LanTcpPlugin extends TcpPlugin {
 		return remotes;
 	}
 
-	private List<InetSocketAddress> getRemoteIpv6SocketAddresses(
-			TransportProperties p) {
-		List<InetAddress> addrs = parseIpv6Addresses(p.get(PROP_IPV6));
-		int port = parsePortProperty(p.get(PROP_PORT));
-		if (addrs.isEmpty() || port == 0) return emptyList();
-		List<InetSocketAddress> remotes = new ArrayList<>();
-		for (InetAddress addr : addrs) {
-			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);
-		}
+	private boolean isAcceptableAddress(InetAddress a) {
+		// Accept link-local and site-local IPv4 addresses
+		boolean ipv4 = a instanceof Inet4Address;
+		boolean loop = a.isLoopbackAddress();
+		boolean link = a.isLinkLocalAddress();
+		boolean site = a.isSiteLocalAddress();
+		return ipv4 && !loop && (link || site);
 	}
 
 	@Override
 	protected boolean isConnectable(InterfaceAddress local,
 			InetSocketAddress remote) {
 		if (remote.getPort() == 0) return false;
-		InetAddress remoteAddress = remote.getAddress();
-		boolean ipv4 = local.getAddress() instanceof Inet4Address;
-		if (!isAcceptableAddress(remoteAddress, ipv4)) return false;
+		if (!isAcceptableAddress(remote.getAddress())) 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();
@@ -345,10 +271,10 @@ class LanTcpPlugin extends TcpPlugin {
 			} catch (IOException e) {
 				if (LOG.isLoggable(INFO))
 					LOG.info("Failed to bind " + scrubSocketAddress(addr));
-				tryToClose(ss, LOG, WARNING);
+				tryToClose(ss);
 			}
 		}
-		if (ss == null) {
+		if (ss == null || !ss.isBound()) {
 			LOG.info("Could not bind server socket for key agreement");
 			return null;
 		}
@@ -361,18 +287,11 @@ 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);
-		if (ss == null) return null;
+		if (!isRunning()) return null;
+		ServerSocket ss = socket;
 		InterfaceAddress local = getLocalInterfaceAddress(ss.getInetAddress());
 		if (local == null) {
 			LOG.warning("No interface for key agreement server socket");
@@ -444,7 +363,7 @@ class LanTcpPlugin extends TcpPlugin {
 
 		@Override
 		public void close() {
-			tryToClose(ss, LOG, WARNING);
+			IoUtils.tryToClose(ss, LOG, WARNING);
 		}
 	}
 }

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

@@ -1,7 +1,8 @@
 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 +12,26 @@ 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_IDLE_TIME = (int) SECONDS.toMillis(30);
-	private static final int POLLING_INTERVAL = (int) MINUTES.toMillis(1);
-	private static final int CONNECTION_TIMEOUT = (int) SECONDS.toMillis(3);
+	private static final int MAX_LATENCY = 30_000; // 30 seconds
+	private static final int MAX_IDLE_TIME = 30_000; // 30 seconds
+	private static final int CONNECTION_TIMEOUT = 3_000; // 3 seconds
+	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,
+			BackoffFactory backoffFactory) {
 		this.ioExecutor = ioExecutor;
-		this.eventBus = eventBus;
+		this.backoffFactory = backoffFactory;
 	}
 
 	@Override
@@ -44,10 +46,9 @@ public class LanTcpPluginFactory implements DuplexPluginFactory {
 
 	@Override
 	public DuplexPlugin createPlugin(PluginCallback callback) {
-		LanTcpPlugin plugin = new LanTcpPlugin(ioExecutor, callback,
-				MAX_LATENCY, MAX_IDLE_TIME, POLLING_INTERVAL,
-				CONNECTION_TIMEOUT);
-		eventBus.addListener(plugin);
-		return plugin;
+		Backoff backoff = backoffFactory.createBackoff(MIN_POLLING_INTERVAL,
+				MAX_POLLING_INTERVAL, BACKOFF_BASE);
+		return new LanTcpPlugin(ioExecutor, backoff, callback, MAX_LATENCY,
+				MAX_IDLE_TIME, CONNECTION_TIMEOUT);
 	}
 }

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) {
-				LOG.info("External address not available");
-			} else {
+			if (LOG.isLoggable(INFO))
+				LOG.info(
+						"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

@@ -3,13 +3,10 @@ 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.PluginCallback;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
@@ -17,8 +14,7 @@ import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
 import org.briarproject.bramble.api.properties.TransportProperties;
 import org.briarproject.bramble.api.rendezvous.KeyMaterialSource;
 import org.briarproject.bramble.api.rendezvous.RendezvousEndpoint;
-import org.briarproject.bramble.api.settings.Settings;
-import org.briarproject.bramble.api.settings.event.SettingsUpdatedEvent;
+import org.briarproject.bramble.util.IoUtils;
 
 import java.io.IOException;
 import java.net.InetAddress;
@@ -39,26 +35,19 @@ import java.util.logging.Logger;
 import java.util.regex.Pattern;
 
 import javax.annotation.Nullable;
-import javax.annotation.concurrent.GuardedBy;
-import javax.annotation.concurrent.ThreadSafe;
 
 import static java.util.Collections.emptyList;
 import static java.util.Collections.list;
 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.plugin.Plugin.State.ACTIVE;
-import static org.briarproject.bramble.api.plugin.Plugin.State.DISABLED;
-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.util.IoUtils.tryToClose;
 import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.bramble.util.PrivacyUtils.scrubSocketAddress;
 import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
-abstract class TcpPlugin implements DuplexPlugin, EventListener {
+abstract class TcpPlugin implements DuplexPlugin {
 
 	private static final Logger LOG = getLogger(TcpPlugin.class.getName());
 
@@ -66,32 +55,33 @@ 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();
+
+	protected volatile boolean running = false;
+	protected volatile ServerSocket socket = null;
 
 	/**
 	 * 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(
-			boolean ipv4);
+	protected abstract List<InetSocketAddress> getLocalSocketAddresses();
 
 	/**
 	 * Adds the address on which the plugin is listening to the transport
 	 * properties.
 	 */
-	protected abstract void setLocalSocketAddress(InetSocketAddress a,
-			boolean ipv4);
+	protected abstract void setLocalSocketAddress(InetSocketAddress a);
 
 	/**
 	 * 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 +90,13 @@ abstract class TcpPlugin implements DuplexPlugin, EventListener {
 	protected abstract boolean isConnectable(InterfaceAddress local,
 			InetSocketAddress remote);
 
-	/**
-	 * Returns true if the plugin is enabled by default.
-	 */
-	protected abstract boolean isEnabledByDefault();
-
-	TcpPlugin(Executor ioExecutor, PluginCallback callback, int maxLatency,
-			int maxIdleTime, int pollingInterval, int connectionTimeout) {
+	TcpPlugin(Executor ioExecutor, Backoff backoff, PluginCallback callback,
+			int maxLatency, int maxIdleTime, 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;
@@ -133,49 +118,49 @@ abstract class TcpPlugin implements DuplexPlugin, EventListener {
 	@Override
 	public void start() {
 		if (used.getAndSet(true)) throw new IllegalStateException();
-		Settings settings = callback.getSettings();
-		state.setStarted(
-				settings.getBoolean(PREF_PLUGIN_ENABLE, isEnabledByDefault()));
+		running = true;
 		bind();
 	}
 
 	protected void bind() {
 		bindExecutor.execute(() -> {
-			if (getState() != INACTIVE) return;
-			bind(true);
-			bind(false);
+			if (!running) return;
+			if (socket != null && !socket.isClosed()) return;
+			ServerSocket ss = null;
+			for (InetSocketAddress addr : getLocalSocketAddresses()) {
+				try {
+					ss = new ServerSocket();
+					ss.bind(addr);
+					break;
+				} catch (IOException e) {
+					if (LOG.isLoggable(INFO))
+						LOG.info("Failed to bind " + scrubSocketAddress(addr));
+					tryToClose(ss);
+				}
+			}
+			if (ss == null || !ss.isBound()) {
+				LOG.info("Could not bind server socket");
+				return;
+			}
+			if (!running) {
+				tryToClose(ss);
+				return;
+			}
+			socket = ss;
+			backoff.reset();
+			InetSocketAddress local =
+					(InetSocketAddress) ss.getLocalSocketAddress();
+			setLocalSocketAddress(local);
+			if (LOG.isLoggable(INFO))
+				LOG.info("Listening on " + scrubSocketAddress(local));
+			callback.transportEnabled();
+			acceptContactConnections();
 		});
 	}
 
-	private void bind(boolean ipv4) {
-		ServerSocket ss = null;
-		for (InetSocketAddress addr : getLocalSocketAddresses(ipv4)) {
-			try {
-				ss = new ServerSocket();
-				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) {
-			LOG.info("Could not bind server socket");
-			return;
-		}
-		if (!state.setServerSocket(ss, ipv4)) {
-			LOG.info("Closing redundant server socket");
-			tryToClose(ss, LOG, WARNING);
-			return;
-		}
-		InetSocketAddress local =
-				(InetSocketAddress) ss.getLocalSocketAddress();
-		setLocalSocketAddress(local, ipv4);
-		if (LOG.isLoggable(INFO))
-			LOG.info("Listening on " + scrubSocketAddress(local));
-		ServerSocket finalSocket = ss;
-		ioExecutor.execute(() -> acceptContactConnections(finalSocket, ipv4));
+	protected void tryToClose(@Nullable ServerSocket ss) {
+		IoUtils.tryToClose(ss, LOG, WARNING);
+		callback.transportDisabled();
 	}
 
 	String getIpPortString(InetSocketAddress a) {
@@ -185,39 +170,34 @@ abstract class TcpPlugin implements DuplexPlugin, EventListener {
 		return addr + ":" + a.getPort();
 	}
 
-	private void acceptContactConnections(ServerSocket ss, boolean ipv4) {
-		while (true) {
+	private void acceptContactConnections() {
+		while (isRunning()) {
 			Socket s;
 			try {
-				s = ss.accept();
+				s = socket.accept();
 				s.setSoTimeout(socketTimeout);
 			} catch (IOException e) {
-				// This is expected when the server socket is closed
-				LOG.info("Server socket closed");
-				state.clearServerSocket(ss, ipv4);
+				// This is expected when the socket is closed
+				if (LOG.isLoggable(INFO)) LOG.info(e.toString());
 				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);
+		running = false;
+		tryToClose(socket);
 	}
 
 	@Override
-	public State getState() {
-		return state.getState();
-	}
-
-	@Override
-	public int getReasonsDisabled() {
-		return state.getReasonsDisabled();
+	public boolean isRunning() {
+		return running && socket != null && !socket.isClosed();
 	}
 
 	@Override
@@ -227,13 +207,14 @@ abstract class TcpPlugin implements DuplexPlugin, EventListener {
 
 	@Override
 	public int getPollingInterval() {
-		return pollingInterval;
+		return backoff.getPollingInterval();
 	}
 
 	@Override
 	public void poll(Collection<Pair<TransportProperties, ConnectionHandler>>
 			properties) {
-		if (getState() != ACTIVE) return;
+		if (!isRunning()) return;
+		backoff.increment();
 		for (Pair<TransportProperties, ConnectionHandler> p : properties) {
 			connect(p.getFirst(), p.getSecond());
 		}
@@ -242,28 +223,23 @@ 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);
-		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;
+		if (!isRunning()) return null;
+		ServerSocket ss = socket;
 		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 +264,9 @@ 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 +289,8 @@ 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;
@@ -330,7 +301,14 @@ 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;
 		}
 	}
@@ -388,114 +366,4 @@ abstract class TcpPlugin implements DuplexPlugin, EventListener {
 			return emptyList();
 		}
 	}
-
-	@Override
-	public void eventOccurred(Event e) {
-		if (e instanceof SettingsUpdatedEvent) {
-			SettingsUpdatedEvent s = (SettingsUpdatedEvent) e;
-			if (s.getNamespace().equals(getId().getString()))
-				ioExecutor.execute(() -> onSettingsUpdated(s.getSettings()));
-		}
-	}
-
-	@IoExecutor
-	private void onSettingsUpdated(Settings settings) {
-		boolean enabledByUser =
-				settings.getBoolean(PREF_PLUGIN_ENABLE, isEnabledByDefault());
-		List<ServerSocket> toClose = state.setEnabledByUser(enabledByUser);
-		State s = getState();
-		if (!toClose.isEmpty()) {
-			LOG.info("Disabled by user, closing server sockets");
-			for (ServerSocket ss : toClose) tryToClose(ss, LOG, WARNING);
-		} else if (s == INACTIVE) {
-			LOG.info("Enabled by user, opening server sockets");
-			bind();
-		}
-	}
-
-	@ThreadSafe
-	@NotNullByDefault
-	protected class PluginState {
-
-		@GuardedBy("this")
-		private boolean started = false, stopped = false, enabledByUser = false;
-
-		@GuardedBy("this")
-		@Nullable
-		private ServerSocket serverSocketV4 = null, serverSocketV6 = null;
-
-		synchronized void setStarted(boolean enabledByUser) {
-			started = true;
-			this.enabledByUser = enabledByUser;
-			callback.pluginStateChanged(getState());
-		}
-
-		synchronized List<ServerSocket> setStopped() {
-			stopped = true;
-			List<ServerSocket> toClose = clearServerSockets();
-			callback.pluginStateChanged(getState());
-			return toClose;
-		}
-
-		@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) {
-			return ipv4 ? serverSocketV4 : serverSocketV6;
-		}
-
-		synchronized boolean setServerSocket(ServerSocket ss, boolean ipv4) {
-			if (stopped) return false;
-			if (ipv4) {
-				if (serverSocketV4 != null) return false;
-				serverSocketV4 = ss;
-			} else {
-				if (serverSocketV6 != null) return false;
-				serverSocketV6 = ss;
-			}
-			callback.pluginStateChanged(getState());
-			return true;
-		}
-
-		synchronized void clearServerSocket(ServerSocket ss, boolean ipv4) {
-			if (ipv4) {
-				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 INACTIVE;
-		}
-
-		synchronized int getReasonsDisabled() {
-			return getState() == DISABLED ? REASON_USER : 0;
-		}
-	}
 }

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

@@ -2,6 +2,7 @@ package org.briarproject.bramble.plugin.tcp;
 
 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.properties.TransportProperties;
@@ -16,7 +17,6 @@ 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 +29,10 @@ 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) {
-		super(ioExecutor, callback, maxLatency, maxIdleTime, pollingInterval,
+			int connectionTimeout) {
+		super(ioExecutor, backoff, callback, maxLatency, maxIdleTime,
 				connectionTimeout);
 		this.portMapper = portMapper;
 	}
@@ -43,16 +43,10 @@ class WanTcpPlugin extends TcpPlugin {
 	}
 
 	@Override
-	protected boolean isEnabledByDefault() {
-		return DEFAULT_PREF_PLUGIN_ENABLE;
-	}
-
-	@Override
-	protected List<InetSocketAddress> getLocalSocketAddresses(boolean ipv4) {
-		if (!ipv4) return emptyList();
+	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 +76,14 @@ 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) {
-		if (!ipv4) return emptyList();
-		InetSocketAddress parsed = parseIpv4SocketAddress(p.get(PROP_IP_PORT));
+			TransportProperties p) {
+		InetSocketAddress parsed = parseSocketAddress(p.get(PROP_IP_PORT));
 		if (parsed == null) return emptyList();
 		return singletonList(parsed);
 	}
@@ -99,8 +96,7 @@ class WanTcpPlugin extends TcpPlugin {
 	}
 
 	@Override
-	protected void setLocalSocketAddress(InetSocketAddress a, boolean ipv4) {
-		if (!ipv4) throw new AssertionError();
+	protected void setLocalSocketAddress(InetSocketAddress a) {
 		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

@@ -1,8 +1,9 @@
 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 +13,27 @@ 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_IDLE_TIME = (int) SECONDS.toMillis(30);
-	private static final int POLLING_INTERVAL = (int) MINUTES.toMillis(1);
-	private static final int CONNECTION_TIMEOUT = (int) SECONDS.toMillis(30);
+	private static final int MAX_LATENCY = 30_000; // 30 seconds
+	private static final int MAX_IDLE_TIME = 30_000; // 30 seconds
+	private static final int CONNECTION_TIMEOUT = 30_000; // 30 seconds
+	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) {
+	public WanTcpPluginFactory(Executor ioExecutor,
+			BackoffFactory backoffFactory, ShutdownManager shutdownManager) {
 		this.ioExecutor = ioExecutor;
-		this.eventBus = eventBus;
+		this.backoffFactory = backoffFactory;
 		this.shutdownManager = shutdownManager;
 	}
 
@@ -48,10 +49,10 @@ 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);
+		return new WanTcpPlugin(ioExecutor, backoff,
 				new PortMapperImpl(shutdownManager), callback, MAX_LATENCY,
-				MAX_IDLE_TIME, POLLING_INTERVAL, CONNECTION_TIMEOUT);
-		eventBus.addListener(plugin);
-		return plugin;
+				MAX_IDLE_TIME, CONNECTION_TIMEOUT);
 	}
 }

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

@@ -17,7 +17,7 @@ public interface CircumventionProvider {
 	String[] BLOCKED = {"CN", "IR", "EG", "BY", "TR", "SY", "VE"};
 
 	/**
-	 * Countries where obfs4 or meek bridge connections are likely to work.
+	 * Countries where obfs4 bridge connection are likely to work.
 	 * Should be a subset of {@link #BLOCKED}.
 	 */
 	String[] BRIDGES = { "CN", "IR", "EG", "BY", "TR", "SY", "VE" };

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

@@ -15,8 +15,8 @@ import org.briarproject.bramble.api.network.NetworkManager;
 import org.briarproject.bramble.api.network.NetworkStatus;
 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.PluginCallback;
 import org.briarproject.bramble.api.plugin.PluginException;
@@ -45,20 +45,15 @@ 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;
 import java.util.regex.Pattern;
 import java.util.zip.ZipInputStream;
 
-import javax.annotation.Nullable;
-import javax.annotation.concurrent.GuardedBy;
-import javax.annotation.concurrent.ThreadSafe;
 import javax.net.SocketFactory;
 
 import static java.util.Arrays.asList;
@@ -70,19 +65,7 @@ import static java.util.logging.Logger.getLogger;
 import static net.freehaven.tor.control.TorControlCommands.HS_ADDRESS;
 import static net.freehaven.tor.control.TorControlCommands.HS_PRIVKEY;
 import static org.briarproject.bramble.api.nullsafety.NullSafety.requireNonNull;
-import static org.briarproject.bramble.api.plugin.Plugin.State.ACTIVE;
-import static org.briarproject.bramble.api.plugin.Plugin.State.DISABLED;
-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;
@@ -93,10 +76,6 @@ import static org.briarproject.bramble.api.plugin.TorConstants.PREF_TOR_ONLY_WHE
 import static org.briarproject.bramble.api.plugin.TorConstants.PREF_TOR_PORT;
 import static org.briarproject.bramble.api.plugin.TorConstants.PROP_ONION_V2;
 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;
@@ -110,69 +89,40 @@ 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 ConnectionStatus connectionStatus;
 	private final AtomicBoolean used = new AtomicBoolean(false);
 
-	protected final PluginState state = new PluginState();
-
+	private volatile ServerSocket socket = null;
 	private volatile Socket controlSocket = null;
 	private volatile TorControlConnection controlConnection = null;
 	private volatile Settings settings = null;
 
+	protected volatile boolean running = false;
+
 	protected abstract int getProcessId();
 
 	protected abstract long getLastUpdateTime();
@@ -181,11 +131,10 @@ 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 stablePollingInterval, File torDirectory) {
+			int maxIdleTime, File torDirectory) {
 		this.ioExecutor = ioExecutor;
 		this.networkManager = networkManager;
 		this.locationUtils = locationUtils;
@@ -194,6 +143,7 @@ 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 +152,6 @@ 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");
@@ -211,6 +159,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		configFile = new File(torDirectory, "torrc");
 		doneFile = new File(torDirectory, "done");
 		cookieFile = new File(torDirectory, ".tor/control_auth_cookie");
+		connectionStatus = new ConnectionStatus();
 		// Don't execute more than one connection status check at a time
 		connectionStatusExecutor =
 				new PoliteExecutor("TorPlugin", ioExecutor, 1);
@@ -241,7 +190,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			}
 		}
 		// Load the settings
-		settings = migrateSettings(callback.getSettings());
+		settings = callback.getSettings();
 		// Install or update the assets if necessary
 		if (!assetsAreUpToDate()) installAssets();
 		if (cookieFile.exists() && !cookieFile.delete())
@@ -309,6 +258,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			// Tell Tor to exit when the control connection is closed
 			controlConnection.takeOwnership();
 			controlConnection.resetConf(singletonList(OWNER));
+			running = true;
 			// Register to receive events from the Tor process
 			controlConnection.setEventHandler(this);
 			controlConnection.setEvents(asList(EVENTS));
@@ -316,12 +266,11 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			String phase = controlConnection.getInfo("status/bootstrap-phase");
 			if (phase != null && phase.contains("PROGRESS=100")) {
 				LOG.info("Tor has already bootstrapped");
-				state.setBootstrapped();
+				connectionStatus.setBootstrapped();
 			}
 		} catch (IOException e) {
 			throw new PluginException(e);
 		}
-		state.setStarted();
 		// Check whether we're online
 		updateConnectionStatus(networkManager.getNetworkStatus(),
 				batteryManager.isCharging());
@@ -329,18 +278,6 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		bind();
 	}
 
-	// TODO: Remove after a reasonable migration period (added 2020-06-25)
-	private Settings migrateSettings(Settings settings) {
-		int network = settings.getInt(PREF_TOR_NETWORK,
-				DEFAULT_PREF_TOR_NETWORK);
-		if (network == PREF_TOR_NETWORK_NEVER) {
-			settings.putInt(PREF_TOR_NETWORK, DEFAULT_PREF_TOR_NETWORK);
-			settings.putBoolean(PREF_PLUGIN_ENABLE, false);
-			callback.mergeSettings(settings);
-		}
-		return settings;
-	}
-
 	private boolean assetsAreUpToDate() {
 		return doneFile.lastModified() > getLastUpdateTime();
 	}
@@ -456,11 +393,11 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 				tryToClose(ss, LOG, WARNING);
 				return;
 			}
-			if (!state.setServerSocket(ss)) {
-				LOG.info("Closing redundant server socket");
+			if (!running) {
 				tryToClose(ss, LOG, WARNING);
 				return;
 			}
+			socket = ss;
 			// Store the port number
 			String localPort = String.valueOf(ss.getLocalPort());
 			Settings s = new Settings();
@@ -468,73 +405,23 @@ 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);
 		});
 	}
 
 	private void publishHiddenService(String port) {
-		if (!state.isTorRunning()) return;
-		// TODO: Remove support for v2 hidden services after a reasonable
-		// migration period (migration started 2020-06-30)
-		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");
+		if (!running) return;
+		LOG.info("Creating hidden service");
+		String privKey = settings.get(HS_PRIVKEY);
 		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) {
-				response = controlConnection.addOnion("NEW:ED25519-V3",
-						portLines, null);
-			} else {
-				response = controlConnection.addOnion(privKey, portLines);
-			}
+			if (privKey == null)
+				response = controlConnection.addOnion(portLines);
+			else response = controlConnection.addOnion(privKey, portLines);
 		} catch (IOException e) {
 			logException(LOG, WARNING, e);
 			return;
@@ -548,42 +435,42 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			return;
 		}
 		// Publish the hidden service's onion hostname in transport properties
-		String onion3 = response.get(HS_ADDRESS);
-		if (LOG.isLoggable(INFO)) {
-			LOG.info("V3 hidden service " + scrubOnion(onion3));
-		}
+		String onion2 = response.get(HS_ADDRESS);
+		if (LOG.isLoggable(INFO))
+			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_V3_CREATED, String.valueOf(clock.currentTimeMillis()));
+			s.put(HS_PRIVKEY, response.get(HS_PRIVKEY));
 			callback.mergeSettings(s);
 		}
 	}
 
 	private void acceptContactConnections(ServerSocket ss) {
-		while (true) {
+		while (running) {
 			Socket s;
 			try {
 				s = ss.accept();
 				s.setSoTimeout(socketTimeout);
 			} catch (IOException e) {
-				// This is expected when the server socket is closed
-				LOG.info("Server socket closed");
-				state.clearServerSocket(ss);
+				// This is expected when the socket is closed
+				if (LOG.isLoggable(INFO)) LOG.info(e.toString());
 				return;
 			}
 			LOG.info("Connection received");
+			backoff.reset();
 			callback.handleConnection(new TorTransportConnection(this, s));
 		}
 	}
 
 	protected void enableNetwork(boolean enable) throws IOException {
-		state.enableNetwork(enable);
+		if (!running) return;
+		connectionStatus.enableNetwork(enable);
 		controlConnection.setConf("DisableNetwork", enable ? "0" : "1");
+		if (!enable) callback.transportDisabled();
 	}
 
 	private void enableBridges(boolean enable, boolean needsMeek)
@@ -607,8 +494,9 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 
 	@Override
 	public void stop() {
-		ServerSocket ss = state.setStopped();
-		tryToClose(ss, LOG, WARNING);
+		running = false;
+		tryToClose(socket, LOG, WARNING);
+		callback.transportDisabled();
 		if (controlSocket != null && controlConnection != null) {
 			try {
 				LOG.info("Stopping Tor");
@@ -622,13 +510,8 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	}
 
 	@Override
-	public State getState() {
-		return state.getState();
-	}
-
-	@Override
-	public int getReasonsDisabled() {
-		return state.getReasonsDisabled();
+	public boolean isRunning() {
+		return running && connectionStatus.isConnected();
 	}
 
 	@Override
@@ -638,19 +521,14 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 
 	@Override
 	public int getPollingInterval() {
-		if (state.isDescriptorPublished()) {
-			LOG.info("Using stable polling interval");
-			return stablePollingInterval;
-		} else {
-			LOG.info("Using initial polling interval");
-			return initialPollingInterval;
-		}
+		return backoff.getPollingInterval();
 	}
 
 	@Override
 	public void poll(Collection<Pair<TransportProperties, ConnectionHandler>>
 			properties) {
-		if (getState() != ACTIVE) return;
+		if (!isRunning()) return;
+		backoff.increment();
 		for (Pair<TransportProperties, ConnectionHandler> p : properties) {
 			connect(p.getFirst(), p.getSecond());
 		}
@@ -659,22 +537,22 @@ 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
-		// migration period (migration started 2020-06-30)
-		String bestOnion = null, version = null;
+		if (!isRunning()) return null;
+		String bestOnion = 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 +562,6 @@ 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 +571,17 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		if (bestOnion == null) return null;
 		Socket s = null;
 		try {
-			if (LOG.isLoggable(INFO)) {
-				LOG.info("Connecting to " + version + " "
-						+ scrubOnion(bestOnion));
-			}
+			if (LOG.isLoggable(INFO))
+				LOG.info("Connecting to " + scrubOnion(bestOnion));
 			s = torSocketFactory.createSocket(bestOnion + ".onion", 80);
 			s.setSoTimeout(socketTimeout);
-			if (LOG.isLoggable(INFO)) {
-				LOG.info("Connected to " + version + " "
-						+ scrubOnion(bestOnion));
-			}
+			if (LOG.isLoggable(INFO))
+				LOG.info("Connected to " + scrubOnion(bestOnion));
 			return new TorTransportConnection(this, s);
 		} catch (IOException e) {
 			if (LOG.isLoggable(INFO)) {
-				LOG.info("Could not connect to " + version + " "
-						+ scrubOnion(bestOnion) + ": " + e.toString());
+				LOG.info("Could not connect to " + scrubOnion(bestOnion)
+						+ ": " + e.toString());
 			}
 			tryToClose(s, LOG, WARNING);
 			return null;
@@ -761,8 +634,8 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 								new TorTransportConnection(this, s));
 					}
 				} catch (IOException e) {
-					// This is expected when the server socket is closed
-					LOG.info("Rendezvous server socket closed");
+					// This is expected when the socket is closed
+					if (LOG.isLoggable(INFO)) LOG.info(e.toString());
 				}
 			});
 			Map<Integer, String> portLines =
@@ -789,8 +662,11 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 
 	@Override
 	public void circuitStatus(String status, String id, String path) {
-		if (status.equals("BUILT") && state.getAndSetCircuitBuilt()) {
+		if (status.equals("BUILT") &&
+				connectionStatus.getAndSetCircuitBuilt()) {
 			LOG.info("First circuit built");
+			backoff.reset();
+			if (isRunning()) callback.transportEnabled();
 		}
 	}
 
@@ -800,8 +676,8 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 
 	@Override
 	public void orConnStatus(String status, String orName) {
-		if (LOG.isLoggable(INFO)) LOG.info("OR connection " + status);
-		state.setOrConnectionStatus(orName, status);
+		if (LOG.isLoggable(INFO))
+			LOG.info("OR connection " + status + " " + orName);
 		if (status.equals("CLOSED") || status.equals("FAILED")) {
 			// Check whether we've lost connectivity
 			updateConnectionStatus(networkManager.getNetworkStatus(),
@@ -821,21 +697,16 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	public void message(String severity, String msg) {
 		if (LOG.isLoggable(INFO)) LOG.info(severity + " " + msg);
 		if (severity.equals("NOTICE") && msg.startsWith("Bootstrapped 100%")) {
-			state.setBootstrapped();
+			connectionStatus.setBootstrapped();
+			backoff.reset();
+			if (isRunning()) callback.transportEnabled();
 		}
 	}
 
 	@Override
 	public void unrecognized(String type, String msg) {
-		if (type.equals("HS_DESC") && msg.startsWith("UPLOADED")) {
-			String[] words = msg.split(" ");
-			if (words.length > 1 && ONION_V3.matcher(words[1]).matches()) {
-				LOG.info("V3 descriptor uploaded");
-				state.descriptorUploaded();
-			} else {
-				LOG.info("V2 descriptor uploaded");
-			}
-		}
+		if (type.equals("HS_DESC") && msg.startsWith("UPLOADED"))
+			LOG.info("Descriptor uploaded");
 	}
 
 	@Override
@@ -865,7 +736,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	private void disableNetwork() {
 		connectionStatusExecutor.execute(() -> {
 			try {
-				if (state.isTorRunning()) enableNetwork(false);
+				enableNetwork(false);
 			} catch (IOException ex) {
 				logException(LOG, WARNING, ex);
 			}
@@ -875,90 +746,63 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	private void updateConnectionStatus(NetworkStatus status,
 			boolean charging) {
 		connectionStatusExecutor.execute(() -> {
-			if (!state.isTorRunning()) return;
+			if (!running) return;
 			boolean online = status.isConnected();
 			boolean wifi = status.isWifi();
 			String country = locationUtils.getCurrentCountry();
 			boolean blocked =
 					circumventionProvider.isTorProbablyBlocked(country);
-			boolean enabledByUser = settings.getBoolean(PREF_PLUGIN_ENABLE,
-					DEFAULT_PREF_PLUGIN_ENABLE);
 			int network = settings.getInt(PREF_TOR_NETWORK,
-					DEFAULT_PREF_TOR_NETWORK);
-			boolean useMobile = settings.getBoolean(PREF_TOR_MOBILE,
-					DEFAULT_PREF_TOR_MOBILE);
+					PREF_TOR_NETWORK_AUTOMATIC);
+			boolean useMobile = settings.getBoolean(PREF_TOR_MOBILE, true);
 			boolean onlyWhenCharging =
-					settings.getBoolean(PREF_TOR_ONLY_WHEN_CHARGING,
-							DEFAULT_PREF_TOR_ONLY_WHEN_CHARGING);
+					settings.getBoolean(PREF_TOR_ONLY_WHEN_CHARGING, false);
 			boolean bridgesWork = circumventionProvider.doBridgesWork(country);
 			boolean automatic = network == PREF_TOR_NETWORK_AUTOMATIC;
 
 			if (LOG.isLoggable(INFO)) {
 				LOG.info("Online: " + online + ", wifi: " + wifi);
-				if (country.isEmpty()) LOG.info("Country code unknown");
+				if ("".equals(country)) LOG.info("Country code unknown");
 				else LOG.info("Country code: " + country);
 				LOG.info("Charging: " + charging);
 			}
 
-			int reasonsDisabled = 0;
-			boolean enableNetwork = false, enableBridges = false;
-			boolean useMeek = false, enableConnectionPadding = false;
-
-			if (!online) {
-				LOG.info("Disabling network, device is offline");
-			} else {
-				if (!enabledByUser) {
-					LOG.info("User has disabled Tor");
-					reasonsDisabled |= REASON_USER;
-				}
-				if (!charging && onlyWhenCharging) {
-					LOG.info("Configured not to use battery");
-					reasonsDisabled |= REASON_BATTERY;
-				}
-				if (!useMobile && !wifi) {
-					LOG.info("Configured not to use mobile data");
-					reasonsDisabled |= REASON_MOBILE_DATA;
-				}
-				if (automatic && blocked && !bridgesWork) {
-					LOG.info("Country is blocked");
-					reasonsDisabled |= REASON_COUNTRY_BLOCKED;
-				}
-
-				if (reasonsDisabled != 0) {
-					LOG.info("Disabling network due to settings");
-				} else {
-					LOG.info("Enabling network");
-					enableNetwork = true;
-					if (network == PREF_TOR_NETWORK_WITH_BRIDGES ||
-							(automatic && bridgesWork)) {
-						if (circumventionProvider.needsMeek(country)) {
-							LOG.info("Using meek bridges");
-							enableBridges = true;
-							useMeek = true;
-						} else {
-							LOG.info("Using obfs4 bridges");
-							enableBridges = true;
-						}
-					} else {
-						LOG.info("Not using bridges");
-					}
-					if (wifi && charging) {
-						LOG.info("Enabling connection padding");
-						enableConnectionPadding = true;
-					} else {
-						LOG.info("Disabling connection padding");
-					}
-				}
-			}
-
-			state.setReasonsDisabled(reasonsDisabled);
-
 			try {
-				if (enableNetwork) {
-					enableBridges(enableBridges, useMeek);
-					enableConnectionPadding(enableConnectionPadding);
+				if (!online) {
+					LOG.info("Disabling network, device is offline");
+					enableNetwork(false);
+				} else if (!charging && onlyWhenCharging) {
+					LOG.info("Disabling network, device is on battery");
+					enableNetwork(false);
+				} else if (network == PREF_TOR_NETWORK_NEVER ||
+						(!useMobile && !wifi)) {
+					LOG.info("Disabling network, device is using mobile data");
+					enableNetwork(false);
+				} else if (automatic && blocked && !bridgesWork) {
+					LOG.info("Disabling network, country is blocked");
+					enableNetwork(false);
+				} else if (network == PREF_TOR_NETWORK_WITH_BRIDGES ||
+						(automatic && bridgesWork)) {
+					if (circumventionProvider.needsMeek(country)) {
+						LOG.info("Enabling network, using meek bridges");
+						enableBridges(true, true);
+					} else {
+						LOG.info("Enabling network, using obfs4 bridges");
+						enableBridges(true, false);
+					}
+					enableNetwork(true);
+				} else {
+					LOG.info("Enabling network, not using bridges");
+					enableBridges(false, false);
+					enableNetwork(true);
+				}
+				if (online && wifi && charging) {
+					LOG.info("Enabling connection padding");
+					enableConnectionPadding(true);
+				} else {
+					LOG.info("Disabling connection padding");
+					enableConnectionPadding(false);
 				}
-				enableNetwork(enableNetwork);
 			} catch (IOException e) {
 				logException(LOG, WARNING, e);
 			}
@@ -966,134 +810,33 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	}
 
 	private void enableConnectionPadding(boolean enable) throws IOException {
+		if (!running) return;
 		controlConnection.setConf("ConnectionPadding", enable ? "1" : "0");
 	}
 
-	@ThreadSafe
-	@NotNullByDefault
-	protected class PluginState {
+	private static class ConnectionStatus {
 
-		@GuardedBy("this")
-		private boolean started = false,
-				stopped = false,
-				networkInitialised = false,
-				networkEnabled = false,
-				bootstrapped = false,
-				circuitBuilt = false,
-				settingsChecked = false;
+		// All of the following are locking: this
+		private boolean networkEnabled = false;
+		private boolean bootstrapped = false, circuitBuilt = false;
 
-		@GuardedBy("this")
-		private int reasonsDisabled = 0;
-
-		@GuardedBy("this")
-		@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());
-		}
-
-		synchronized boolean isTorRunning() {
-			return started && !stopped;
-		}
-
-		@Nullable
-		synchronized ServerSocket setStopped() {
-			stopped = true;
-			ServerSocket ss = serverSocket;
-			serverSocket = null;
-			callback.pluginStateChanged(getState());
-			return ss;
-		}
-
-		synchronized void setBootstrapped() {
+		private synchronized void setBootstrapped() {
 			bootstrapped = true;
-			callback.pluginStateChanged(getState());
 		}
 
-		synchronized boolean getAndSetCircuitBuilt() {
+		private synchronized boolean getAndSetCircuitBuilt() {
 			boolean firstCircuit = !circuitBuilt;
 			circuitBuilt = true;
-			callback.pluginStateChanged(getState());
 			return firstCircuit;
 		}
 
-		synchronized void enableNetwork(boolean enable) {
-			networkInitialised = true;
+		private synchronized void enableNetwork(boolean enable) {
 			networkEnabled = enable;
-			if (!enable) {
-				circuitBuilt = false;
-				descriptorsUploaded = 0;
-			}
-			callback.pluginStateChanged(getState());
+			if (!enable) circuitBuilt = false;
 		}
 
-		synchronized void setReasonsDisabled(int reasonsDisabled) {
-			settingsChecked = true;
-			this.reasonsDisabled = reasonsDisabled;
-			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;
-			serverSocket = ss;
-			return true;
-		}
-
-		// Doesn't affect getState()
-		synchronized void clearServerSocket(ServerSocket ss) {
-			if (serverSocket == ss) serverSocket = null;
-		}
-
-		synchronized State getState() {
-			if (!started || stopped || !settingsChecked) {
-				return STARTING_STOPPING;
-			}
-			if (reasonsDisabled != 0) return DISABLED;
-			if (!networkInitialised) return ENABLING;
-			if (!networkEnabled) return INACTIVE;
-			return bootstrapped && circuitBuilt && !orConnections.isEmpty()
-					? ACTIVE : ENABLING;
-		}
-
-		synchronized int getReasonsDisabled() {
-			return getState() == DISABLED ? reasonsDisabled : 0;
+		private synchronized boolean isConnected() {
+			return networkEnabled && bootstrapped && circuitBuilt;
 		}
 	}
 }

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;
 
@@ -42,7 +41,6 @@ import static org.briarproject.bramble.api.properties.TransportPropertyConstants
 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
@@ -274,22 +272,14 @@ class TransportPropertyManagerImpl implements TransportPropertyManager,
 				LatestUpdate latest = findLatest(txn, localGroup.getId(), t,
 						true);
 				if (latest == null) {
-					merged = new TransportProperties(p);
-					Iterator<String> it = merged.values().iterator();
-					while (it.hasNext()) {
-						if (isNullOrEmpty(it.next())) it.remove();
-					}
+					merged = p;
 					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()) {
-						String key = e.getKey(), value = e.getValue();
-						if (isNullOrEmpty(value)) merged.remove(key);
-						else merged.put(key, value);
-					}
+					merged.putAll(p);
 					changed = !merged.equals(old);
 				}
 				if (changed) {

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

@@ -31,8 +31,8 @@ import org.briarproject.bramble.api.plugin.TransportConnectionWriter;
 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.TransportActiveEvent;
-import org.briarproject.bramble.api.plugin.event.TransportInactiveEvent;
+import org.briarproject.bramble.api.plugin.event.TransportDisabledEvent;
+import org.briarproject.bramble.api.plugin.event.TransportEnabledEvent;
 import org.briarproject.bramble.api.properties.TransportProperties;
 import org.briarproject.bramble.api.rendezvous.KeyMaterialSource;
 import org.briarproject.bramble.api.rendezvous.RendezvousEndpoint;
@@ -269,11 +269,11 @@ class RendezvousPollerImpl implements RendezvousPoller, Service, EventListener {
 		} else if (e instanceof PendingContactRemovedEvent) {
 			PendingContactRemovedEvent p = (PendingContactRemovedEvent) e;
 			removePendingContactAsync(p.getId());
-		} else if (e instanceof TransportActiveEvent) {
-			TransportActiveEvent t = (TransportActiveEvent) e;
+		} else if (e instanceof TransportEnabledEvent) {
+			TransportEnabledEvent t = (TransportEnabledEvent) e;
 			addTransportAsync(t.getTransportId());
-		} else if (e instanceof TransportInactiveEvent) {
-			TransportInactiveEvent t = (TransportInactiveEvent) e;
+		} else if (e instanceof TransportDisabledEvent) {
+			TransportDisabledEvent t = (TransportDisabledEvent) e;
 			removeTransportAsync(t.getTransportId());
 		} else if (e instanceof RendezvousConnectionOpenedEvent) {
 			RendezvousConnectionOpenedEvent r =

bramble-core/src/main/java/org/briarproject/bramble/reporting/DevReporterImpl.java

@@ -6,7 +6,7 @@ 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.TorConstants;
-import org.briarproject.bramble.api.plugin.event.TransportActiveEvent;
+import org.briarproject.bramble.api.plugin.event.TransportEnabledEvent;
 import org.briarproject.bramble.api.reporting.DevConfig;
 import org.briarproject.bramble.api.reporting.DevReporter;
 import org.briarproject.bramble.util.IoUtils;
@@ -92,8 +92,8 @@ class DevReporterImpl implements DevReporter, EventListener {
 
 	@Override
 	public void eventOccurred(Event e) {
-		if (e instanceof TransportActiveEvent) {
-			TransportActiveEvent t = (TransportActiveEvent) e;
+		if (e instanceof TransportEnabledEvent) {
+			TransportEnabledEvent t = (TransportEnabledEvent) e;
 			if (t.getTransportId().equals(TorConstants.ID))
 				ioExecutor.execute(this::sendReports);
 		}

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

@@ -11,8 +11,6 @@ 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;
@@ -21,7 +19,6 @@ 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;
@@ -76,7 +73,6 @@ 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;
@@ -94,16 +90,14 @@ class DuplexOutgoingSession implements SyncSession, EventListener {
 	private volatile boolean interrupted = false;
 
 	DuplexOutgoingSession(DatabaseComponent db, Executor dbExecutor,
-			EventBus eventBus, Clock clock, ContactId contactId,
-			TransportId transportId, int maxLatency, int maxIdleTime,
-			StreamWriter streamWriter, SyncRecordWriter recordWriter,
-			@Nullable Priority priority) {
+			EventBus eventBus, Clock clock, ContactId contactId, int maxLatency,
+			int maxIdleTime, StreamWriter streamWriter,
+			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;
@@ -172,6 +166,9 @@ class DuplexOutgoingSession implements SyncSession, EventListener {
 						dataToFlush = true;
 					}
 				}
+				// Write any records that were already in the queue
+				ThrowingRunnable<IOException> task;
+				while ((task = writerTasks.poll()) != null) task.run();
 				streamWriter.sendEndOfStream();
 			} catch (InterruptedException e) {
 				LOG.info("Interrupted while waiting for a record to write");
@@ -236,12 +233,6 @@ 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/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,
-			int maxLatency, StreamWriter streamWriter,
-			SyncRecordWriter recordWriter) {
+			EventBus eventBus, ContactId contactId, int maxLatency,
+			StreamWriter streamWriter, 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;
@@ -101,6 +95,9 @@ class SimplexOutgoingSession implements SyncSession, EventListener {
 					if (task == CLOSE) break;
 					task.run();
 				}
+				// Write any records that were already in the queue
+				ThrowingRunnable<IOException> task;
+				while ((task = writerTasks.poll()) != null) task.run();
 				streamWriter.sendEndOfStream();
 			} catch (InterruptedException e) {
 				LOG.info("Interrupted while waiting for a record to write");
@@ -129,12 +126,6 @@ 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/SyncSessionFactoryImpl.java

@@ -5,7 +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;
@@ -59,23 +58,23 @@ class SyncSessionFactoryImpl implements SyncSessionFactory {
 	}
 
 	@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,
-			int maxLatency, int maxIdleTime, StreamWriter streamWriter,
+	public SyncSession createDuplexOutgoingSession(ContactId c, int maxLatency,
+			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);
 	}
 }

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

@@ -74,10 +74,6 @@ public class ConnectionRegistryImplTest extends BrambleMockTestCase {
 		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
@@ -85,15 +81,13 @@ public class ConnectionRegistryImplTest extends BrambleMockTestCase {
 			oneOf(eventBus).broadcast(with(any(ConnectionOpenedEvent.class)));
 			oneOf(eventBus).broadcast(with(any(ContactConnectedEvent.class)));
 		}});
-		c.registerIncomingConnection(contactId1, transportId1, conn1);
+		c.registerConnection(contactId1, transportId1, conn1, true);
 		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
@@ -101,15 +95,13 @@ public class ConnectionRegistryImplTest extends BrambleMockTestCase {
 		context.checking(new Expectations() {{
 			oneOf(eventBus).broadcast(with(any(ConnectionOpenedEvent.class)));
 		}});
-		c.registerIncomingConnection(contactId1, transportId1, conn2);
+		c.registerConnection(contactId1, transportId1, conn2, true);
 		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
@@ -123,8 +115,6 @@ public class ConnectionRegistryImplTest extends BrambleMockTestCase {
 				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
@@ -138,8 +128,6 @@ public class ConnectionRegistryImplTest extends BrambleMockTestCase {
 
 		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 {
@@ -170,20 +158,11 @@ public class ConnectionRegistryImplTest extends BrambleMockTestCase {
 			exactly(2).of(eventBus).broadcast(with(any(
 					ContactConnectedEvent.class)));
 		}});
-		c.registerIncomingConnection(contactId1, transportId1, conn1);
-		c.registerIncomingConnection(contactId2, transportId1, conn2);
-		c.registerIncomingConnection(contactId2, transportId2, conn3);
+		c.registerConnection(contactId1, transportId1, conn1, true);
+		c.registerConnection(contactId2, transportId1, conn2, true);
+		c.registerConnection(contactId2, transportId2, conn3, true);
 		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));
@@ -212,12 +191,12 @@ public class ConnectionRegistryImplTest extends BrambleMockTestCase {
 		ConnectionRegistry c =
 				new ConnectionRegistryImpl(eventBus, pluginConfig);
 
-		// Connect via transport 1 (worse than 2) with no priority set
+		// Connect via transport 1 (worse 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.registerIncomingConnection(contactId1, transportId1, conn1);
+		c.registerConnection(contactId1, transportId1, conn1, true);
 		context.assertIsSatisfied();
 
 		assertEquals(singletonList(contactId1),
@@ -234,7 +213,8 @@ public class ConnectionRegistryImplTest extends BrambleMockTestCase {
 		context.checking(new Expectations() {{
 			oneOf(eventBus).broadcast(with(any(ConnectionOpenedEvent.class)));
 		}});
-		c.registerOutgoingConnection(contactId1, transportId2, conn2, high);
+		c.registerConnection(contactId1, transportId2, conn2, true);
+		c.setPriority(contactId1, transportId2, conn2, high);
 		context.assertIsSatisfied();
 
 		assertEquals(singletonList(contactId1),
@@ -252,7 +232,8 @@ public class ConnectionRegistryImplTest extends BrambleMockTestCase {
 		context.checking(new Expectations() {{
 			oneOf(eventBus).broadcast(with(any(ConnectionOpenedEvent.class)));
 		}});
-		c.registerOutgoingConnection(contactId1, transportId3, conn3, high);
+		c.registerConnection(contactId1, transportId3, conn3, true);
+		c.setPriority(contactId1, transportId3, conn3, high);
 		context.assertIsSatisfied();
 
 		assertEquals(singletonList(contactId1),
@@ -288,7 +269,8 @@ public class ConnectionRegistryImplTest extends BrambleMockTestCase {
 			oneOf(eventBus).broadcast(with(any(ConnectionOpenedEvent.class)));
 			oneOf(eventBus).broadcast(with(any(ContactConnectedEvent.class)));
 		}});
-		c.registerOutgoingConnection(contactId1, transportId1, conn1, low);
+		c.registerConnection(contactId1, transportId1, conn1, true);
+		c.setPriority(contactId1, transportId1, conn1, low);
 		context.assertIsSatisfied();
 
 		assertEquals(singletonList(contactId1),
@@ -309,7 +291,8 @@ public class ConnectionRegistryImplTest extends BrambleMockTestCase {
 			oneOf(conn2).interruptOutgoingSession();
 			oneOf(eventBus).broadcast(with(any(ConnectionOpenedEvent.class)));
 		}});
-		c.registerOutgoingConnection(contactId1, transportId2, conn2, high);
+		c.registerConnection(contactId1, transportId2, conn2, true);
+		c.setPriority(contactId1, transportId2, conn2, high);
 		context.assertIsSatisfied();
 
 		assertEquals(singletonList(contactId1),
@@ -327,7 +310,8 @@ public class ConnectionRegistryImplTest extends BrambleMockTestCase {
 		context.checking(new Expectations() {{
 			oneOf(eventBus).broadcast(with(any(ConnectionOpenedEvent.class)));
 		}});
-		c.registerOutgoingConnection(contactId1, transportId3, conn3, low);
+		c.registerConnection(contactId1, transportId3, conn3, true);
+		c.setPriority(contactId1, transportId3, conn3, low);
 		context.assertIsSatisfied();
 
 		assertEquals(singletonList(contactId1),
@@ -386,7 +370,8 @@ public class ConnectionRegistryImplTest extends BrambleMockTestCase {
 			oneOf(eventBus).broadcast(with(any(ConnectionOpenedEvent.class)));
 			oneOf(eventBus).broadcast(with(any(ContactConnectedEvent.class)));
 		}});
-		c.registerOutgoingConnection(contactId1, transportId1, conn1, high);
+		c.registerConnection(contactId1, transportId1, conn1, true);
+		c.setPriority(contactId1, transportId1, conn1, high);
 		context.assertIsSatisfied();
 
 		assertEquals(singletonList(contactId1),
@@ -404,7 +389,8 @@ public class ConnectionRegistryImplTest extends BrambleMockTestCase {
 			oneOf(conn1).interruptOutgoingSession();
 			oneOf(eventBus).broadcast(with(any(ConnectionOpenedEvent.class)));
 		}});
-		c.registerOutgoingConnection(contactId1, transportId2, conn2, low);
+		c.registerConnection(contactId1, transportId2, conn2, true);
+		c.setPriority(contactId1, transportId2, conn2, low);
 		context.assertIsSatisfied();
 
 		assertEquals(singletonList(contactId1),
@@ -422,7 +408,7 @@ public class ConnectionRegistryImplTest extends BrambleMockTestCase {
 		context.checking(new Expectations() {{
 			oneOf(eventBus).broadcast(with(any(ConnectionOpenedEvent.class)));
 		}});
-		c.registerOutgoingConnection(contactId1, transportId3, conn3, high);
+		c.registerConnection(contactId1, transportId3, conn3, true);
 		context.assertIsSatisfied();
 
 		assertEquals(singletonList(contactId1),
@@ -479,7 +465,8 @@ public class ConnectionRegistryImplTest extends BrambleMockTestCase {
 			oneOf(eventBus).broadcast(with(any(ConnectionOpenedEvent.class)));
 			oneOf(eventBus).broadcast(with(any(ContactConnectedEvent.class)));
 		}});
-		c.registerOutgoingConnection(contactId1, transportId1, conn1, high);
+		c.registerConnection(contactId1, transportId1, conn1, true);
+		c.setPriority(contactId1, transportId1, conn1, high);
 		context.assertIsSatisfied();
 
 		assertEquals(singletonList(contactId1),
@@ -491,7 +478,7 @@ public class ConnectionRegistryImplTest extends BrambleMockTestCase {
 		context.checking(new Expectations() {{
 			oneOf(eventBus).broadcast(with(any(ConnectionOpenedEvent.class)));
 		}});
-		c.registerIncomingConnection(contactId1, transportId1, conn2);
+		c.registerConnection(contactId1, transportId1, conn2, true);
 		context.assertIsSatisfied();
 
 		assertEquals(singletonList(contactId1),
@@ -518,7 +505,8 @@ public class ConnectionRegistryImplTest extends BrambleMockTestCase {
 			oneOf(conn3).interruptOutgoingSession();
 			oneOf(eventBus).broadcast(with(any(ConnectionOpenedEvent.class)));
 		}});
-		c.registerOutgoingConnection(contactId1, transportId1, conn3, low);
+		c.registerConnection(contactId1, transportId1, conn3, true);
+		c.setPriority(contactId1, transportId1, conn3, low);
 		context.assertIsSatisfied();
 
 		assertEquals(singletonList(contactId1),
@@ -542,7 +530,8 @@ public class ConnectionRegistryImplTest extends BrambleMockTestCase {
 			oneOf(eventBus).broadcast(with(any(ConnectionOpenedEvent.class)));
 			oneOf(eventBus).broadcast(with(any(ContactConnectedEvent.class)));
 		}});
-		c.registerOutgoingConnection(contactId1, transportId1, conn1, low);
+		c.registerConnection(contactId1, transportId1, conn1, true);
+		c.setPriority(contactId1, transportId1, conn1, low);
 		context.assertIsSatisfied();
 
 		assertEquals(singletonList(contactId1),
@@ -554,7 +543,7 @@ public class ConnectionRegistryImplTest extends BrambleMockTestCase {
 		context.checking(new Expectations() {{
 			oneOf(eventBus).broadcast(with(any(ConnectionOpenedEvent.class)));
 		}});
-		c.registerIncomingConnection(contactId1, transportId1, conn2);
+		c.registerConnection(contactId1, transportId1, conn2, true);
 		context.assertIsSatisfied();
 
 		assertEquals(singletonList(contactId1),

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/PollerImplTest.java

@@ -12,8 +12,9 @@ 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.TransportActiveEvent;
-import org.briarproject.bramble.api.plugin.event.TransportInactiveEvent;
+import org.briarproject.bramble.api.plugin.event.ConnectionOpenedEvent;
+import org.briarproject.bramble.api.plugin.event.TransportDisabledEvent;
+import org.briarproject.bramble.api.plugin.event.TransportEnabledEvent;
 import org.briarproject.bramble.api.plugin.simplex.SimplexPlugin;
 import org.briarproject.bramble.api.properties.TransportProperties;
 import org.briarproject.bramble.api.properties.TransportPropertyManager;
@@ -156,20 +157,22 @@ public class PollerImplTest extends BrambleMockTestCase {
 	}
 
 	@Test
-	public void testDoesNotReconnectOnOutgoingConnectionClosed() {
+	public void testRescheduleOnOutgoingConnectionClosed() {
 		DuplexPlugin plugin = context.mock(DuplexPlugin.class);
 
 		context.checking(new Expectations() {{
 			allowing(plugin).getId();
 			will(returnValue(transportId));
 		}});
+		expectReschedule(plugin);
 
 		poller.eventOccurred(new ConnectionClosedEvent(contactId, transportId,
 				false, false));
 	}
 
 	@Test
-	public void testReconnectsOnOutgoingConnectionFailed() throws Exception {
+	public void testRescheduleAndReconnectOnOutgoingConnectionFailed()
+			throws Exception {
 		DuplexPlugin plugin = context.mock(DuplexPlugin.class);
 		DuplexTransportConnection duplexConnection =
 				context.mock(DuplexTransportConnection.class);
@@ -178,6 +181,7 @@ public class PollerImplTest extends BrambleMockTestCase {
 			allowing(plugin).getId();
 			will(returnValue(transportId));
 		}});
+		expectReschedule(plugin);
 		expectReconnect(plugin, duplexConnection);
 
 		poller.eventOccurred(new ConnectionClosedEvent(contactId, transportId,
@@ -185,33 +189,149 @@ public class PollerImplTest extends BrambleMockTestCase {
 	}
 
 	@Test
-	public void testDoesNotReconnectOnIncomingConnectionClosed() {
+	public void testRescheduleOnIncomingConnectionClosed() {
 		DuplexPlugin plugin = context.mock(DuplexPlugin.class);
 
 		context.checking(new Expectations() {{
 			allowing(plugin).getId();
 			will(returnValue(transportId));
 		}});
+		expectReschedule(plugin);
 
 		poller.eventOccurred(new ConnectionClosedEvent(contactId, transportId,
 				true, false));
 	}
 
 	@Test
-	public void testDoesNotReconnectOnIncomingConnectionFailed() {
+	public void testRescheduleOnIncomingConnectionFailed() {
 		DuplexPlugin plugin = context.mock(DuplexPlugin.class);
 
 		context.checking(new Expectations() {{
 			allowing(plugin).getId();
 			will(returnValue(transportId));
 		}});
+		expectReschedule(plugin);
 
 		poller.eventOccurred(new ConnectionClosedEvent(contactId, transportId,
 				true, false));
 	}
 
 	@Test
-	public void testPollsOnTransportActivated() throws Exception {
+	public void testRescheduleOnConnectionOpened() {
+		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 ConnectionOpenedEvent(contactId, transportId,
+				false));
+	}
+
+	@Test
+	public void testRescheduleDoesNotReplaceEarlierTask() {
+		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 ConnectionOpenedEvent(contactId, transportId,
+				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
+	public void testPollsOnTransportEnabled() throws Exception {
 		DuplexPlugin plugin = context.mock(DuplexPlugin.class);
 
 		context.checking(new Expectations() {{
@@ -250,7 +370,7 @@ public class PollerImplTest extends BrambleMockTestCase {
 					pairOf(equal(properties), any(ConnectionHandler.class)))));
 		}});
 
-		poller.eventOccurred(new TransportActiveEvent(transportId));
+		poller.eventOccurred(new TransportEnabledEvent(transportId));
 	}
 
 	@Test
@@ -291,11 +411,11 @@ public class PollerImplTest extends BrambleMockTestCase {
 			// All contacts are connected, so don't poll the plugin
 		}});
 
-		poller.eventOccurred(new TransportActiveEvent(transportId));
+		poller.eventOccurred(new TransportEnabledEvent(transportId));
 	}
 
 	@Test
-	public void testCancelsPollingOnTransportDeactivated() {
+	public void testCancelsPollingOnTransportDisabled() {
 		Plugin plugin = context.mock(Plugin.class);
 
 		context.checking(new Expectations() {{
@@ -313,12 +433,31 @@ public class PollerImplTest extends BrambleMockTestCase {
 			oneOf(scheduler).schedule(with(any(Runnable.class)), with(0L),
 					with(MILLISECONDS));
 			will(returnValue(future));
-			// The plugin is deactivated before the task runs - cancel the task
+			// The plugin is disabled before the task runs - cancel the task
 			oneOf(future).cancel(false);
 		}});
 
-		poller.eventOccurred(new TransportActiveEvent(transportId));
-		poller.eventOccurred(new TransportInactiveEvent(transportId));
+		poller.eventOccurred(new TransportEnabledEvent(transportId));
+		poller.eventOccurred(new TransportDisabledEvent(transportId));
+	}
+
+	private void expectReschedule(Plugin plugin) {
+		context.checking(new Expectations() {{
+			// 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));
+		}});
 	}
 
 	private void expectReconnect(DuplexPlugin plugin,

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

@@ -3,7 +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.Plugin.State;
+import org.briarproject.bramble.api.plugin.Backoff;
 import org.briarproject.bramble.api.plugin.PluginCallback;
 import org.briarproject.bramble.api.plugin.TransportConnectionReader;
 import org.briarproject.bramble.api.plugin.TransportConnectionWriter;
@@ -31,7 +31,6 @@ import static java.util.concurrent.Executors.newCachedThreadPool;
 import static java.util.concurrent.TimeUnit.SECONDS;
 import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.COMMIT_LENGTH;
 import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.TRANSPORT_ID_LAN;
-import static org.briarproject.bramble.api.plugin.Plugin.PREF_PLUGIN_ENABLE;
 import static org.briarproject.bramble.plugin.tcp.LanTcpPlugin.areAddressesInSameNetwork;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
@@ -41,6 +40,7 @@ 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 +49,7 @@ 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;
@@ -302,15 +302,10 @@ public class LanTcpPluginTest extends BrambleTestCase {
 		private final CountDownLatch propertiesLatch = new CountDownLatch(2);
 		private final CountDownLatch connectionsLatch = new CountDownLatch(1);
 		private final TransportProperties local = new TransportProperties();
-		private final Settings settings = new Settings();
-
-		private Callback() {
-			settings.putBoolean(PREF_PLUGIN_ENABLE, true);
-		}
 
 		@Override
 		public Settings getSettings() {
-			return settings;
+			return new Settings();
 		}
 
 		@Override
@@ -329,7 +324,11 @@ public class LanTcpPluginTest extends BrambleTestCase {
 		}
 
 		@Override
-		public void pluginStateChanged(State newState) {
+		public void transportEnabled() {
+		}
+
+		@Override
+		public void transportDisabled() {
 		}
 
 		@Override
@@ -345,4 +344,20 @@ 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() {
+		}
+	}
 }

bramble-core/src/test/java/org/briarproject/bramble/properties/TransportPropertyManagerImplTest.java

@@ -566,10 +566,6 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 		Contact contact = getContact();
 		Group contactGroup = getGroup(CLIENT_ID, MAJOR_VERSION);
 
-		// Property with an empty value should be discarded
-		TransportProperties properties = new TransportProperties(fooProperties);
-		properties.put("fooKey3", "");
-
 		context.checking(new DbExpectations() {{
 			oneOf(db).transaction(with(false), withDbRunnable(txn));
 			// There are no existing properties to merge with
@@ -593,7 +589,7 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 		}});
 
 		TransportPropertyManagerImpl t = createInstance();
-		t.mergeLocalProperties(new TransportId("foo"), properties);
+		t.mergeLocalProperties(new TransportId("foo"), fooProperties);
 	}
 
 	@Test
@@ -609,24 +605,16 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 		MessageId localGroupUpdateId = new MessageId(getRandomId());
 		Map<MessageId, BdfDictionary> localGroupMessageMetadata =
 				singletonMap(localGroupUpdateId, oldMetadata);
-
 		MessageId contactGroupUpdateId = new MessageId(getRandomId());
 		Map<MessageId, BdfDictionary> contactGroupMessageMetadata =
 				singletonMap(contactGroupUpdateId, oldMetadata);
-
 		TransportProperties oldProperties = new TransportProperties();
 		oldProperties.put("fooKey1", "oldFooValue1");
-		oldProperties.put("fooKey3", "oldFooValue3");
 		BdfDictionary oldPropertiesDict = BdfDictionary.of(
-				new BdfEntry("fooKey1", "oldFooValue1"),
-				new BdfEntry("fooKey3", "oldFooValue3")
+				new BdfEntry("fooKey1", "oldFooValue1")
 		);
 		BdfList oldUpdate = BdfList.of("foo", 1, oldPropertiesDict);
 
-		// Property assigned an empty value should be removed
-		TransportProperties properties = new TransportProperties(fooProperties);
-		properties.put("fooKey3", "");
-
 		context.checking(new DbExpectations() {{
 			oneOf(db).transaction(with(false), withDbRunnable(txn));
 			// Merge the new properties with the existing properties
@@ -659,7 +647,7 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 		}});
 
 		TransportPropertyManagerImpl t = createInstance();
-		t.mergeLocalProperties(new TransportId("foo"), properties);
+		t.mergeLocalProperties(new TransportId("foo"), fooProperties);
 	}
 
 	private void expectGetLocalProperties(Transaction txn) throws Exception {

bramble-core/src/test/java/org/briarproject/bramble/rendezvous/RendezvousPollerImplTest.java

@@ -17,8 +17,8 @@ import org.briarproject.bramble.api.plugin.ConnectionHandler;
 import org.briarproject.bramble.api.plugin.PluginManager;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
-import org.briarproject.bramble.api.plugin.event.TransportActiveEvent;
-import org.briarproject.bramble.api.plugin.event.TransportInactiveEvent;
+import org.briarproject.bramble.api.plugin.event.TransportDisabledEvent;
+import org.briarproject.bramble.api.plugin.event.TransportEnabledEvent;
 import org.briarproject.bramble.api.properties.TransportProperties;
 import org.briarproject.bramble.api.rendezvous.KeyMaterialSource;
 import org.briarproject.bramble.api.rendezvous.RendezvousEndpoint;
@@ -178,10 +178,10 @@ public class RendezvousPollerImplTest extends BrambleMockTestCase {
 		rendezvousPoller.startService();
 		context.assertIsSatisfied();
 
-		// Activate the transport - no endpoints should be created yet
+		// Enable the transport - no endpoints should be created yet
 		expectGetPlugin();
 
-		rendezvousPoller.eventOccurred(new TransportActiveEvent(transportId));
+		rendezvousPoller.eventOccurred(new TransportEnabledEvent(transportId));
 		context.assertIsSatisfied();
 
 		// Add the pending contact - endpoint should be created and polled
@@ -212,8 +212,8 @@ public class RendezvousPollerImplTest extends BrambleMockTestCase {
 				new PendingContactRemovedEvent(pendingContact.getId()));
 		context.assertIsSatisfied();
 
-		// Deactivate the transport - endpoint is already closed
-		rendezvousPoller.eventOccurred(new TransportInactiveEvent(transportId));
+		// Disable the transport - endpoint is already closed
+		rendezvousPoller.eventOccurred(new TransportDisabledEvent(transportId));
 	}
 
 	@Test
@@ -230,10 +230,10 @@ public class RendezvousPollerImplTest extends BrambleMockTestCase {
 		rendezvousPoller.startService();
 		context.assertIsSatisfied();
 
-		// Activate the transport - no endpoints should be created yet
+		// Enable the transport - no endpoints should be created yet
 		expectGetPlugin();
 
-		rendezvousPoller.eventOccurred(new TransportActiveEvent(transportId));
+		rendezvousPoller.eventOccurred(new TransportEnabledEvent(transportId));
 		context.assertIsSatisfied();
 
 		// Add the pending contact - endpoint should be created and polled
@@ -269,12 +269,12 @@ public class RendezvousPollerImplTest extends BrambleMockTestCase {
 				new PendingContactRemovedEvent(pendingContact.getId()));
 		context.assertIsSatisfied();
 
-		// Deactivate the transport - endpoint is already closed
-		rendezvousPoller.eventOccurred(new TransportInactiveEvent(transportId));
+		// Disable the transport - endpoint is already closed
+		rendezvousPoller.eventOccurred(new TransportDisabledEvent(transportId));
 	}
 
 	@Test
-	public void testCreatesAndClosesEndpointsWhenTransportIsActivatedAndDeactivated()
+	public void testCreatesAndClosesEndpointsWhenTransportIsEnabledAndDisabled()
 			throws Exception {
 		long beforeExpiry = pendingContact.getTimestamp();
 
@@ -292,19 +292,19 @@ public class RendezvousPollerImplTest extends BrambleMockTestCase {
 				new PendingContactAddedEvent(pendingContact));
 		context.assertIsSatisfied();
 
-		// Activate the transport - endpoint should be created
+		// Enable the transport - endpoint should be created
 		expectGetPlugin();
 		expectCreateEndpoint();
 		expectStateChangedEvent(WAITING_FOR_CONNECTION);
 
-		rendezvousPoller.eventOccurred(new TransportActiveEvent(transportId));
+		rendezvousPoller.eventOccurred(new TransportEnabledEvent(transportId));
 		context.assertIsSatisfied();
 
-		// Deactivate the transport - endpoint should be closed
+		// Disable the transport - endpoint should be closed
 		expectCloseEndpoint();
 		expectStateChangedEvent(OFFLINE);
 
-		rendezvousPoller.eventOccurred(new TransportInactiveEvent(transportId));
+		rendezvousPoller.eventOccurred(new TransportDisabledEvent(transportId));
 		context.assertIsSatisfied();
 
 		// Remove the pending contact - endpoint is already closed

bramble-core/src/test/java/org/briarproject/bramble/sync/SimplexOutgoingSessionTest.java

@@ -4,7 +4,6 @@ import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.db.DatabaseComponent;
 import org.briarproject.bramble.api.db.Transaction;
 import org.briarproject.bramble.api.event.EventBus;
-import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.sync.Ack;
 import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.Message;
@@ -24,7 +23,6 @@ import static org.briarproject.bramble.api.sync.SyncConstants.MAX_MESSAGE_IDS;
 import static org.briarproject.bramble.test.TestUtils.getContactId;
 import static org.briarproject.bramble.test.TestUtils.getMessage;
 import static org.briarproject.bramble.test.TestUtils.getRandomId;
-import static org.briarproject.bramble.test.TestUtils.getTransportId;
 
 public class SimplexOutgoingSessionTest extends BrambleMockTestCase {
 
@@ -38,15 +36,14 @@ public class SimplexOutgoingSessionTest extends BrambleMockTestCase {
 
 	private final Executor dbExecutor = new ImmediateExecutor();
 	private final ContactId contactId = getContactId();
-	private final TransportId transportId = getTransportId();
 	private final Message message = getMessage(new GroupId(getRandomId()));
 	private final MessageId messageId = message.getId();
 
 	@Test
 	public void testNothingToSend() throws Exception {
 		SimplexOutgoingSession session = new SimplexOutgoingSession(db,
-				dbExecutor, eventBus, contactId, transportId, MAX_LATENCY,
-				streamWriter, recordWriter);
+				dbExecutor, eventBus, contactId, MAX_LATENCY, streamWriter,
+				recordWriter);
 		Transaction noAckTxn = new Transaction(null, false);
 		Transaction noMsgTxn = new Transaction(null, false);
 
@@ -79,8 +76,8 @@ public class SimplexOutgoingSessionTest extends BrambleMockTestCase {
 	public void testSomethingToSend() throws Exception {
 		Ack ack = new Ack(singletonList(messageId));
 		SimplexOutgoingSession session = new SimplexOutgoingSession(db,
-				dbExecutor, eventBus, contactId, transportId, MAX_LATENCY,
-				streamWriter, recordWriter);
+				dbExecutor, eventBus, contactId, MAX_LATENCY, streamWriter,
+				recordWriter);
 		Transaction ackTxn = new Transaction(null, false);
 		Transaction noAckTxn = new Transaction(null, false);
 		Transaction msgTxn = new Transaction(null, false);

bramble-java/src/main/java/org/briarproject/bramble/plugin/DesktopPluginModule.java

@@ -5,6 +5,7 @@ import org.briarproject.bramble.api.io.TimeoutMonitor;
 import org.briarproject.bramble.api.lifecycle.IoExecutor;
 import org.briarproject.bramble.api.lifecycle.ShutdownManager;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.BackoffFactory;
 import org.briarproject.bramble.api.plugin.BluetoothConstants;
 import org.briarproject.bramble.api.plugin.LanTcpConstants;
 import org.briarproject.bramble.api.plugin.PluginConfig;
@@ -36,16 +37,18 @@ public class DesktopPluginModule extends PluginModule {
 
 	@Provides
 	PluginConfig getPluginConfig(@IoExecutor Executor ioExecutor,
-			SecureRandom random, ReliabilityLayerFactory reliabilityFactory,
+			SecureRandom random, BackoffFactory backoffFactory,
+			ReliabilityLayerFactory reliabilityFactory,
 			ShutdownManager shutdownManager, EventBus eventBus,
 			TimeoutMonitor timeoutMonitor) {
 		DuplexPluginFactory bluetooth = new JavaBluetoothPluginFactory(
-				ioExecutor, random, eventBus, timeoutMonitor);
+				ioExecutor, random, eventBus, timeoutMonitor, backoffFactory);
 		DuplexPluginFactory modem = new ModemPluginFactory(ioExecutor,
 				reliabilityFactory);
-		DuplexPluginFactory lan = new LanTcpPluginFactory(ioExecutor, eventBus);
-		DuplexPluginFactory wan = new WanTcpPluginFactory(ioExecutor, eventBus,
-				shutdownManager);
+		DuplexPluginFactory lan = new LanTcpPluginFactory(ioExecutor,
+				backoffFactory);
+		DuplexPluginFactory wan = new WanTcpPluginFactory(ioExecutor,
+				backoffFactory, shutdownManager);
 		Collection<DuplexPluginFactory> duplex =
 				asList(bluetooth, modem, lan, wan);
 		@NotNullByDefault

bramble-java/src/main/java/org/briarproject/bramble/plugin/bluetooth/JavaBluetoothPlugin.java

@@ -3,6 +3,7 @@ package org.briarproject.bramble.plugin.bluetooth;
 import org.briarproject.bramble.api.io.TimeoutMonitor;
 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.duplex.DuplexTransportConnection;
 
@@ -35,10 +36,10 @@ class JavaBluetoothPlugin extends BluetoothPlugin<StreamConnectionNotifier> {
 
 	JavaBluetoothPlugin(BluetoothConnectionLimiter connectionManager,
 			TimeoutMonitor timeoutMonitor, Executor ioExecutor,
-			SecureRandom secureRandom, PluginCallback callback, int maxLatency,
-			int maxIdleTime, int pollingInterval) {
+			SecureRandom secureRandom, Backoff backoff,
+			PluginCallback callback, int maxLatency, int maxIdleTime) {
 		super(connectionManager, timeoutMonitor, ioExecutor, secureRandom,
-				callback, maxLatency, maxIdleTime, pollingInterval);
+				backoff, callback, maxLatency, maxIdleTime);
 	}
 
 	@Override

bramble-java/src/main/java/org/briarproject/bramble/plugin/bluetooth/JavaBluetoothPluginFactory.java

@@ -3,6 +3,8 @@ package org.briarproject.bramble.plugin.bluetooth;
 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;
@@ -13,30 +15,32 @@ 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.BluetoothConstants.ID;
 
 @Immutable
 @NotNullByDefault
 public class JavaBluetoothPluginFactory implements DuplexPluginFactory {
 
-	private static final int MAX_LATENCY = (int) SECONDS.toMillis(30);
-	private static final int MAX_IDLE_TIME = (int) SECONDS.toMillis(30);
-	private static final int POLLING_INTERVAL = (int) MINUTES.toMillis(2);
+	private static final int MAX_LATENCY = 30 * 1000; // 30 seconds
+	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
+	private static final double BACKOFF_BASE = 1.2;
 
 	private final Executor ioExecutor;
 	private final SecureRandom secureRandom;
 	private final EventBus eventBus;
 	private final TimeoutMonitor timeoutMonitor;
+	private final BackoffFactory backoffFactory;
 
 	public JavaBluetoothPluginFactory(Executor ioExecutor,
 			SecureRandom secureRandom, EventBus eventBus,
-			TimeoutMonitor timeoutMonitor) {
+			TimeoutMonitor timeoutMonitor, BackoffFactory backoffFactory) {
 		this.ioExecutor = ioExecutor;
 		this.secureRandom = secureRandom;
 		this.eventBus = eventBus;
 		this.timeoutMonitor = timeoutMonitor;
+		this.backoffFactory = backoffFactory;
 	}
 
 	@Override
@@ -52,10 +56,12 @@ public class JavaBluetoothPluginFactory 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);
 		JavaBluetoothPlugin plugin = new JavaBluetoothPlugin(connectionLimiter,
-				timeoutMonitor, ioExecutor, secureRandom, callback, MAX_LATENCY,
-				MAX_IDLE_TIME, POLLING_INTERVAL);
+				timeoutMonitor, ioExecutor, secureRandom, backoff, callback,
+				MAX_LATENCY, MAX_IDLE_TIME);
 		eventBus.addListener(plugin);
 		return plugin;
 	}

bramble-java/src/main/java/org/briarproject/bramble/plugin/modem/ModemPlugin.java

@@ -4,7 +4,6 @@ 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.MethodsNotNullByDefault;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.bramble.api.plugin.ConnectionHandler;
 import org.briarproject.bramble.api.plugin.PluginCallback;
@@ -24,16 +23,9 @@ import java.util.Collection;
 import java.util.concurrent.atomic.AtomicBoolean;
 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.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
-import static org.briarproject.bramble.api.plugin.Plugin.State.ACTIVE;
-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.util.LogUtils.logException;
 import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
 
@@ -52,8 +44,8 @@ class ModemPlugin implements DuplexPlugin, Modem.Callback {
 	private final PluginCallback callback;
 	private final int maxLatency;
 	private final AtomicBoolean used = new AtomicBoolean(false);
-	private final PluginState state = new PluginState();
 
+	private volatile boolean running = false;
 	private volatile Modem modem = null;
 
 	ModemPlugin(ModemFactory modemFactory, SerialPortList serialPortList,
@@ -83,7 +75,6 @@ class ModemPlugin implements DuplexPlugin, Modem.Callback {
 	@Override
 	public void start() throws PluginException {
 		if (used.getAndSet(true)) throw new IllegalStateException();
-		state.setStarted();
 		for (String portName : serialPortList.getPortNames()) {
 			if (LOG.isLoggable(INFO))
 				LOG.info("Trying to initialise modem on " + portName);
@@ -92,20 +83,18 @@ class ModemPlugin implements DuplexPlugin, Modem.Callback {
 				if (!modem.start()) continue;
 				if (LOG.isLoggable(INFO))
 					LOG.info("Initialised modem on " + portName);
-				state.setInitialised();
+				running = true;
 				return;
 			} catch (IOException e) {
 				logException(LOG, WARNING, e);
 			}
 		}
-		LOG.warning("Failed to initialised modem");
-		state.setFailed();
 		throw new PluginException();
 	}
 
 	@Override
 	public void stop() {
-		state.setStopped();
+		running = false;
 		if (modem != null) {
 			try {
 				modem.stop();
@@ -116,13 +105,8 @@ class ModemPlugin implements DuplexPlugin, Modem.Callback {
 	}
 
 	@Override
-	public State getState() {
-		return state.getState();
-	}
-
-	@Override
-	public int getReasonsDisabled() {
-		return 0;
+	public boolean isRunning() {
+		return running;
 	}
 
 	@Override
@@ -141,8 +125,8 @@ class ModemPlugin implements DuplexPlugin, Modem.Callback {
 		throw new UnsupportedOperationException();
 	}
 
-	private void resetModem() {
-		if (getState() != ACTIVE) return;
+	private boolean resetModem() {
+		if (!running) return false;
 		for (String portName : serialPortList.getPortNames()) {
 			if (LOG.isLoggable(INFO))
 				LOG.info("Trying to initialise modem on " + portName);
@@ -151,18 +135,18 @@ class ModemPlugin implements DuplexPlugin, Modem.Callback {
 				if (!modem.start()) continue;
 				if (LOG.isLoggable(INFO))
 					LOG.info("Initialised modem on " + portName);
-				return;
+				return true;
 			} catch (IOException e) {
 				logException(LOG, WARNING, e);
 			}
 		}
-		LOG.warning("Failed to initialise modem");
-		state.setFailed();
+		running = false;
+		return false;
 	}
 
 	@Override
 	public DuplexTransportConnection createConnection(TransportProperties p) {
-		if (getState() != ACTIVE) return null;
+		if (!running) return null;
 		// Get the ISO 3166 code for the caller's country
 		String fromIso = callback.getLocalProperties().get("iso3166");
 		if (isNullOrEmpty(fromIso)) return null;
@@ -248,41 +232,4 @@ class ModemPlugin implements DuplexPlugin, Modem.Callback {
 			if (exception) resetModem();
 		}
 	}
-
-	@ThreadSafe
-	@NotNullByDefault
-	private class PluginState {
-
-		@GuardedBy("this")
-		private boolean started = false,
-				stopped = false,
-				initialised = false,
-				failed = false;
-
-		private synchronized void setStarted() {
-			started = true;
-			callback.pluginStateChanged(getState());
-		}
-
-		private synchronized void setStopped() {
-			stopped = true;
-			callback.pluginStateChanged(getState());
-		}
-
-		private synchronized void setInitialised() {
-			initialised = true;
-			callback.pluginStateChanged(getState());
-		}
-
-		private synchronized void setFailed() {
-			failed = true;
-			callback.pluginStateChanged(getState());
-		}
-
-		private State getState() {
-			if (!started || stopped) return STARTING_STOPPING;
-			if (failed) return INACTIVE;
-			return initialised ? ACTIVE : ENABLING;
-		}
-	}
 }

bramble-java/src/main/java/org/briarproject/bramble/plugin/tor/JavaTorPlugin.java

@@ -3,6 +3,7 @@ package org.briarproject.bramble.plugin.tor;
 import org.briarproject.bramble.api.battery.BatteryManager;
 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.PluginCallback;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.api.system.LocationUtils;
@@ -23,16 +24,14 @@ abstract class JavaTorPlugin 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 stablePollingInterval, File torDirectory) {
+			int maxIdleTime, File torDirectory) {
 		super(ioExecutor, networkManager, locationUtils, torSocketFactory,
 				clock, resourceProvider, circumventionProvider, batteryManager,
-				torRendezvousCrypto, callback, architecture, maxLatency,
-				maxIdleTime, initialPollingInterval, stablePollingInterval,
-				torDirectory);
+				backoff, torRendezvousCrypto, callback, architecture,
+				maxLatency, maxIdleTime, torDirectory);
 	}
 
 	@Override

bramble-java/src/main/java/org/briarproject/bramble/plugin/tor/UnixTorPlugin.java

@@ -6,6 +6,7 @@ import com.sun.jna.Native;
 import org.briarproject.bramble.api.battery.BatteryManager;
 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.PluginCallback;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.api.system.LocationUtils;
@@ -23,16 +24,14 @@ class UnixTorPlugin extends JavaTorPlugin {
 			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 stablePollingInterval, File torDirectory) {
+			int maxIdleTime, File torDirectory) {
 		super(ioExecutor, networkManager, locationUtils, torSocketFactory,
 				clock, resourceProvider, circumventionProvider, batteryManager,
-				torRendezvousCrypto, callback, architecture,
-				maxLatency, maxIdleTime, initialPollingInterval,
-				stablePollingInterval, torDirectory);
+				backoff, torRendezvousCrypto, callback, architecture,
+				maxLatency, maxIdleTime, torDirectory);
 	}
 
 	@Override

bramble-java/src/main/java/org/briarproject/bramble/plugin/tor/UnixTorPluginFactory.java

@@ -4,6 +4,8 @@ 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;
@@ -20,8 +22,6 @@ 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;
 import static org.briarproject.bramble.util.OsUtils.isLinux;
 
@@ -32,28 +32,18 @@ public class UnixTorPluginFactory implements DuplexPluginFactory {
 	private static final Logger LOG =
 			getLogger(UnixTorPluginFactory.class.getName());
 
-	private static final int MAX_LATENCY = (int) SECONDS.toMillis(30);
-	private static final int MAX_IDLE_TIME = (int) SECONDS.toMillis(30);
-
-	/**
-	 * How often to poll before our hidden service becomes reachable.
-	 */
-	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 static final int MAX_LATENCY = 30 * 1000; // 30 seconds
+	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
+	private static final double BACKOFF_BASE = 1.2;
 
 	private final Executor ioExecutor;
 	private final NetworkManager networkManager;
 	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;
@@ -63,7 +53,7 @@ public class UnixTorPluginFactory implements DuplexPluginFactory {
 	public UnixTorPluginFactory(Executor ioExecutor,
 			NetworkManager networkManager, LocationUtils locationUtils,
 			EventBus eventBus, SocketFactory torSocketFactory,
-			ResourceProvider resourceProvider,
+			BackoffFactory backoffFactory, ResourceProvider resourceProvider,
 			CircumventionProvider circumventionProvider,
 			BatteryManager batteryManager, Clock clock, File torDirectory) {
 		this.ioExecutor = ioExecutor;
@@ -71,6 +61,7 @@ public class UnixTorPluginFactory implements DuplexPluginFactory {
 		this.locationUtils = locationUtils;
 		this.eventBus = eventBus;
 		this.torSocketFactory = torSocketFactory;
+		this.backoffFactory = backoffFactory;
 		this.resourceProvider = resourceProvider;
 		this.circumventionProvider = circumventionProvider;
 		this.batteryManager = batteryManager;
@@ -103,13 +94,14 @@ public class UnixTorPluginFactory implements DuplexPluginFactory {
 			return null;
 		}
 
+		Backoff backoff = backoffFactory.createBackoff(MIN_POLLING_INTERVAL,
+				MAX_POLLING_INTERVAL, BACKOFF_BASE);
 		TorRendezvousCrypto torRendezvousCrypto = new TorRendezvousCryptoImpl();
 		UnixTorPlugin plugin = new UnixTorPlugin(ioExecutor, networkManager,
 				locationUtils, torSocketFactory, clock, resourceProvider,
-				circumventionProvider, batteryManager, torRendezvousCrypto,
-				callback, architecture, MAX_LATENCY, MAX_IDLE_TIME,
-				INITIAL_POLLING_INTERVAL, STABLE_POLLING_INTERVAL,
-				torDirectory);
+				circumventionProvider, batteryManager, backoff,
+				torRendezvousCrypto, callback, architecture, MAX_LATENCY,
+				MAX_IDLE_TIME, torDirectory);
 		eventBus.addListener(plugin);
 		return plugin;
 	}

bramble-java/src/test/java/org/briarproject/bramble/plugin/modem/ModemPluginTest.java

@@ -9,8 +9,6 @@ import org.junit.Test;
 
 import java.io.IOException;
 
-import static org.briarproject.bramble.api.plugin.Plugin.State.ACTIVE;
-import static org.briarproject.bramble.api.plugin.Plugin.State.ENABLING;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertNull;
 
@@ -35,7 +33,6 @@ public class ModemPluginTest extends BrambleMockTestCase {
 	@Test
 	public void testModemCreation() throws Exception {
 		context.checking(new Expectations() {{
-			oneOf(callback).pluginStateChanged(ENABLING);
 			oneOf(serialPortList).getPortNames();
 			will(returnValue(new String[] {"foo", "bar", "baz"}));
 			// First call to createModem() returns false
@@ -53,7 +50,6 @@ public class ModemPluginTest extends BrambleMockTestCase {
 			will(returnValue(modem));
 			oneOf(modem).start();
 			will(returnValue(true));
-			oneOf(callback).pluginStateChanged(ACTIVE);
 		}});
 
 		plugin.start();
@@ -69,14 +65,12 @@ public class ModemPluginTest extends BrambleMockTestCase {
 
 		context.checking(new Expectations() {{
 			// start()
-			oneOf(callback).pluginStateChanged(ENABLING);
 			oneOf(serialPortList).getPortNames();
 			will(returnValue(new String[] {"foo"}));
 			oneOf(modemFactory).createModem(plugin, "foo");
 			will(returnValue(modem));
 			oneOf(modem).start();
 			will(returnValue(true));
-			oneOf(callback).pluginStateChanged(ACTIVE);
 			// createConnection()
 			oneOf(callback).getLocalProperties();
 			will(returnValue(local));
@@ -99,14 +93,12 @@ public class ModemPluginTest extends BrambleMockTestCase {
 
 		context.checking(new Expectations() {{
 			// start()
-			oneOf(callback).pluginStateChanged(ENABLING);
 			oneOf(serialPortList).getPortNames();
 			will(returnValue(new String[] {"foo"}));
 			oneOf(modemFactory).createModem(plugin, "foo");
 			will(returnValue(modem));
 			oneOf(modem).start();
 			will(returnValue(true));
-			oneOf(callback).pluginStateChanged(ACTIVE);
 			// createConnection()
 			oneOf(callback).getLocalProperties();
 			will(returnValue(local));
@@ -129,14 +121,12 @@ public class ModemPluginTest extends BrambleMockTestCase {
 
 		context.checking(new Expectations() {{
 			// start()
-			oneOf(callback).pluginStateChanged(ENABLING);
 			oneOf(serialPortList).getPortNames();
 			will(returnValue(new String[] {"foo"}));
 			oneOf(modemFactory).createModem(plugin, "foo");
 			will(returnValue(modem));
 			oneOf(modem).start();
 			will(returnValue(true));
-			oneOf(callback).pluginStateChanged(ACTIVE);
 			// createConnection()
 			oneOf(callback).getLocalProperties();
 			will(returnValue(local));

bramble-java/src/test/java/org/briarproject/bramble/plugin/tor/BridgeTest.java

@@ -5,6 +5,7 @@ import org.briarproject.bramble.api.battery.BatteryManager;
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.lifecycle.IoExecutor;
 import org.briarproject.bramble.api.network.NetworkManager;
+import org.briarproject.bramble.api.plugin.BackoffFactory;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.api.system.LocationUtils;
@@ -31,7 +32,6 @@ import javax.net.SocketFactory;
 import static java.util.Collections.singletonList;
 import static java.util.concurrent.TimeUnit.SECONDS;
 import static java.util.logging.Logger.getLogger;
-import static org.briarproject.bramble.api.plugin.Plugin.State.ACTIVE;
 import static org.briarproject.bramble.test.TestUtils.deleteTestDirectory;
 import static org.briarproject.bramble.test.TestUtils.getTestDirectory;
 import static org.briarproject.bramble.test.TestUtils.isOptionalTestEnabled;
@@ -68,6 +68,8 @@ public class BridgeTest extends BrambleTestCase {
 	@Inject
 	EventBus eventBus;
 	@Inject
+	BackoffFactory backoffFactory;
+	@Inject
 	Clock clock;
 
 	private final File torDir = getTestDirectory();
@@ -117,8 +119,9 @@ public class BridgeTest extends BrambleTestCase {
 			}
 		};
 		factory = new UnixTorPluginFactory(ioExecutor, networkManager,
-				locationUtils, eventBus, torSocketFactory, resourceProvider,
-				bridgeProvider, batteryManager, clock, torDir);
+				locationUtils, eventBus, torSocketFactory, backoffFactory,
+				resourceProvider, bridgeProvider, batteryManager, clock,
+				torDir);
 	}
 
 	@After
@@ -138,10 +141,10 @@ public class BridgeTest extends BrambleTestCase {
 			plugin.start();
 			long start = clock.currentTimeMillis();
 			while (clock.currentTimeMillis() - start < TIMEOUT) {
-				if (plugin.getState() == ACTIVE) return;
+				if (plugin.isRunning()) return;
 				clock.sleep(500);
 			}
-			if (plugin.getState() != ACTIVE) {
+			if (!plugin.isRunning()) {
 				fail("Could not connect to Tor within timeout.");
 			}
 		} finally {

bramble-java/src/test/java/org/briarproject/bramble/plugin/tor/TestPluginCallback.java

@@ -1,7 +1,6 @@
 package org.briarproject.bramble.plugin.tor;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.plugin.Plugin.State;
 import org.briarproject.bramble.api.plugin.PluginCallback;
 import org.briarproject.bramble.api.plugin.TransportConnectionReader;
 import org.briarproject.bramble.api.plugin.TransportConnectionWriter;
@@ -31,7 +30,11 @@ public class TestPluginCallback implements PluginCallback {
 	}
 
 	@Override
-	public void pluginStateChanged(State state) {
+	public void transportEnabled() {
+	}
+
+	@Override
+	public void transportDisabled() {
 	}
 
 	@Override

briar-android/src/androidTestScreenshot/java/org/briarproject/briar/android/SetupDataTest.java

@@ -120,8 +120,8 @@ public class SetupDataTest extends ScreenshotTest {
 
 		// TODO add messages
 
-		connectionRegistry.registerIncomingConnection(bob.getId(), ID, () -> {
-		});
+		connectionRegistry.registerConnection(bob.getId(), ID, () -> {
+		}, true);
 	}
 
 }

briar-android/src/main/java/org/briarproject/briar/android/AndroidNotificationManagerImpl.java

@@ -164,7 +164,7 @@ class AndroidNotificationManagerImpl implements AndroidNotificationManager,
 		nc.setLockscreenVisibility(VISIBILITY_SECRET);
 		nc.enableVibration(true);
 		nc.enableLights(true);
-		nc.setLightColor(getColor(appContext, R.color.briar_lime_400));
+		nc.setLightColor(getColor(appContext, R.color.briar_green_light));
 		notificationManager.createNotificationChannel(nc);
 	}
 

briar-android/src/main/java/org/briarproject/briar/android/AppModule.java

@@ -19,6 +19,7 @@ import org.briarproject.bramble.api.lifecycle.IoExecutor;
 import org.briarproject.bramble.api.lifecycle.LifecycleManager;
 import org.briarproject.bramble.api.network.NetworkManager;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.BackoffFactory;
 import org.briarproject.bramble.api.plugin.BluetoothConstants;
 import org.briarproject.bramble.api.plugin.LanTcpConstants;
 import org.briarproject.bramble.api.plugin.PluginConfig;
@@ -40,7 +41,6 @@ import org.briarproject.bramble.util.StringUtils;
 import org.briarproject.briar.android.account.LockManagerImpl;
 import org.briarproject.briar.android.keyagreement.ContactExchangeModule;
 import org.briarproject.briar.android.login.LoginModule;
-import org.briarproject.briar.android.navdrawer.NavDrawerModule;
 import org.briarproject.briar.android.viewmodel.ViewModelModule;
 import org.briarproject.briar.api.android.AndroidNotificationManager;
 import org.briarproject.briar.api.android.DozeWatchdog;
@@ -76,7 +76,6 @@ import static org.briarproject.briar.android.TestingConstants.IS_DEBUG_BUILD;
 @Module(includes = {
 		ContactExchangeModule.class,
 		LoginModule.class,
-		NavDrawerModule.class,
 		ViewModelModule.class
 })
 public class AppModule {
@@ -126,22 +125,23 @@ public class AppModule {
 	PluginConfig providePluginConfig(@IoExecutor Executor ioExecutor,
 			@Scheduler ScheduledExecutorService scheduler,
 			AndroidExecutor androidExecutor, SecureRandom random,
-			SocketFactory torSocketFactory, Application app,
-			NetworkManager networkManager, LocationUtils locationUtils,
-			EventBus eventBus, ResourceProvider resourceProvider,
+			SocketFactory torSocketFactory, BackoffFactory backoffFactory,
+			Application app, NetworkManager networkManager,
+			LocationUtils locationUtils, EventBus eventBus,
+			ResourceProvider resourceProvider,
 			CircumventionProvider circumventionProvider,
 			BatteryManager batteryManager, Clock clock,
 			TimeoutMonitor timeoutMonitor) {
 		Context appContext = app.getApplicationContext();
 		DuplexPluginFactory bluetooth = new AndroidBluetoothPluginFactory(
-				ioExecutor, scheduler, androidExecutor, appContext, random,
-				eventBus, clock, timeoutMonitor);
+				ioExecutor, androidExecutor, appContext, random, eventBus,
+				clock, timeoutMonitor, backoffFactory);
 		DuplexPluginFactory tor = new AndroidTorPluginFactory(ioExecutor,
 				scheduler, appContext, networkManager, locationUtils, eventBus,
-				torSocketFactory, resourceProvider, circumventionProvider,
-				batteryManager, clock);
+				torSocketFactory, backoffFactory, resourceProvider,
+				circumventionProvider, batteryManager, clock);
 		DuplexPluginFactory lan = new AndroidLanTcpPluginFactory(ioExecutor,
-				eventBus, appContext);
+				eventBus, backoffFactory, appContext);
 		Collection<DuplexPluginFactory> duplex = asList(bluetooth, tor, lan);
 		@NotNullByDefault
 		PluginConfig pluginConfig = new PluginConfig() {

briar-android/src/main/java/org/briarproject/briar/android/activity/ActivityModule.java

@@ -8,6 +8,8 @@ import org.briarproject.briar.android.controller.BriarController;
 import org.briarproject.briar.android.controller.BriarControllerImpl;
 import org.briarproject.briar.android.controller.DbController;
 import org.briarproject.briar.android.controller.DbControllerImpl;
+import org.briarproject.briar.android.navdrawer.NavDrawerController;
+import org.briarproject.briar.android.navdrawer.NavDrawerControllerImpl;
 
 import dagger.Module;
 import dagger.Provides;
@@ -56,6 +58,14 @@ public class ActivityModule {
 		return dbController;
 	}
 
+	@ActivityScope
+	@Provides
+	NavDrawerController provideNavDrawerController(
+			NavDrawerControllerImpl navDrawerController) {
+		activity.addLifecycleController(navDrawerController);
+		return navDrawerController;
+	}
+
 	@ActivityScope
 	@Provides
 	BriarServiceConnection provideBriarServiceConnection() {

briar-android/src/main/java/org/briarproject/briar/android/contact/add/remote/NicknameFragment.java

@@ -3,6 +3,7 @@ package org.briarproject.briar.android.contact.add.remote;
 import android.content.Context;
 import android.content.DialogInterface.OnClickListener;
 import android.content.Intent;
+import android.graphics.drawable.Drawable;
 import android.os.Bundle;
 import android.text.Editable;
 import android.view.LayoutInflater;
@@ -37,10 +38,12 @@ import androidx.lifecycle.ViewModelProviders;
 import static android.view.View.INVISIBLE;
 import static android.view.View.VISIBLE;
 import static android.widget.Toast.LENGTH_LONG;
+import static androidx.core.content.ContextCompat.getColor;
+import static androidx.core.content.ContextCompat.getDrawable;
+import static androidx.core.graphics.drawable.DrawableCompat.setTint;
 import static java.util.Objects.requireNonNull;
 import static org.briarproject.bramble.api.identity.AuthorConstants.MAX_AUTHOR_NAME_LENGTH;
 import static org.briarproject.bramble.util.StringUtils.utf8IsTooLong;
-import static org.briarproject.briar.android.util.UiUtils.getDialogIcon;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
@@ -196,7 +199,9 @@ public class NicknameFragment extends BaseFragment {
 	private void showWarningDialog(String name1, String name2) {
 		Context ctx = requireContext();
 		Builder b = new Builder(ctx, R.style.BriarDialogTheme);
-		b.setIcon(getDialogIcon(ctx, R.drawable.alerts_and_states_error));
+		Drawable icon = getDrawable(ctx, R.drawable.alerts_and_states_error);
+		setTint(requireNonNull(icon), getColor(ctx, R.color.color_primary));
+		b.setIcon(icon);
 		b.setTitle(getString(R.string.duplicate_link_dialog_title));
 		b.setMessage(
 				getString(R.string.duplicate_link_dialog_text_3, name1, name2));

briar-android/src/main/java/org/briarproject/briar/android/contact/add/remote/PendingContactListActivity.java

@@ -76,7 +76,7 @@ public class PendingContactListActivity extends BriarActivity
 		list.showProgressBar();
 
 		offlineSnackbar = new BriarSnackbarBuilder()
-				.setBackgroundColor(R.color.briar_red_500)
+				.setBackgroundColor(R.color.briar_red)
 				.make(list, R.string.offline_state, LENGTH_INDEFINITE);
 	}
 

briar-android/src/main/java/org/briarproject/briar/android/contact/add/remote/PendingContactViewHolder.java

@@ -46,11 +46,11 @@ class PendingContactViewHolder extends ViewHolder {
 		});
 
 		int color = ContextCompat
-				.getColor(status.getContext(), R.color.briar_lime_600);
+				.getColor(status.getContext(), R.color.briar_green);
 		switch (item.getState()) {
 			case WAITING_FOR_CONNECTION:
-				color = ContextCompat.getColor(status.getContext(),
-						R.color.briar_orange_500);
+				color = ContextCompat
+						.getColor(status.getContext(), R.color.briar_yellow);
 				status.setText(R.string.waiting_for_contact_to_come_online);
 				break;
 			case OFFLINE:
@@ -64,7 +64,7 @@ class PendingContactViewHolder extends ViewHolder {
 				break;
 			case FAILED:
 				color = ContextCompat
-						.getColor(status.getContext(), R.color.briar_red_500);
+						.getColor(status.getContext(), R.color.briar_red);
 				status.setText(R.string.adding_contact_failed);
 				break;
 			default:

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationMessageViewHolder.java

@@ -41,8 +41,7 @@ class ConversationMessageViewHolder extends ConversationItemViewHolder {
 
 		// remember original status text color
 		timeColor = time.getCurrentTextColor();
-		timeColorBubble =
-				getColor(v.getContext(), R.color.msg_status_bubble_foreground);
+		timeColorBubble = getColor(v.getContext(), R.color.briar_white);
 
 		// clone constraint sets from layout files
 		textConstraints.clone(v.getContext(),

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationVisitor.java

@@ -230,11 +230,7 @@ class ConversationVisitor implements
 					R.layout.list_item_conversation_notice_out, text, r);
 		} else {
 			String text;
-			if (r.wasAnswered()) {
-				text = ctx.getString(
-						R.string.introduction_request_answered_received,
-						contactName.getValue(), name);
-			} else if (r.isContact()) {
+			if (r.isContact()) {
 				text = ctx.getString(
 						R.string.introduction_request_exists_received,
 						contactName.getValue(), name);

briar-android/src/main/java/org/briarproject/briar/android/conversation/ImageActivity.java

@@ -2,6 +2,7 @@ package org.briarproject.briar.android.conversation;
 
 import android.content.DialogInterface.OnClickListener;
 import android.content.Intent;
+import android.graphics.drawable.Drawable;
 import android.os.Bundle;
 import android.transition.Fade;
 import android.transition.Transition;
@@ -34,6 +35,8 @@ import androidx.annotation.Nullable;
 import androidx.annotation.RequiresApi;
 import androidx.appcompat.app.AlertDialog.Builder;
 import androidx.appcompat.widget.Toolbar;
+import androidx.core.content.ContextCompat;
+import androidx.core.graphics.drawable.DrawableCompat;
 import androidx.fragment.app.Fragment;
 import androidx.fragment.app.FragmentManager;
 import androidx.fragment.app.FragmentStatePagerAdapter;
@@ -56,7 +59,6 @@ import static com.google.android.material.snackbar.Snackbar.LENGTH_LONG;
 import static java.util.Objects.requireNonNull;
 import static org.briarproject.briar.android.activity.RequestCodes.REQUEST_SAVE_ATTACHMENT;
 import static org.briarproject.briar.android.util.UiUtils.formatDateAbsolute;
-import static org.briarproject.briar.android.util.UiUtils.getDialogIcon;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
@@ -276,7 +278,10 @@ public class ImageActivity extends BriarActivity
 		Builder builder = new Builder(this, R.style.BriarDialogTheme);
 		builder.setTitle(getString(R.string.dialog_title_save_image));
 		builder.setMessage(getString(R.string.dialog_message_save_image));
-		builder.setIcon(getDialogIcon(this, R.drawable.ic_security));
+		Drawable icon = ContextCompat.getDrawable(this, R.drawable.ic_security);
+		DrawableCompat.setTint(requireNonNull(icon),
+				ContextCompat.getColor(this, R.color.color_primary));
+		builder.setIcon(icon);
 		builder.setPositiveButton(R.string.save_image, okListener);
 		builder.setNegativeButton(R.string.cancel, null);
 		builder.show();
@@ -299,7 +304,7 @@ public class ImageActivity extends BriarActivity
 		int stringRes = error ?
 				R.string.save_image_error : R.string.save_image_success;
 		int colorRes = error ?
-				R.color.briar_red_500 : R.color.briar_primary;
+				R.color.briar_red : R.color.briar_primary;
 		new BriarSnackbarBuilder()
 				.setBackgroundColor(colorRes)
 				.make(layout, stringRes, LENGTH_LONG)

briar-android/src/main/java/org/briarproject/briar/android/keyagreement/ContactExchangeActivity.java

@@ -9,7 +9,6 @@ import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.activity.ActivityComponent;
-import org.briarproject.briar.android.fragment.BaseFragment;
 
 import javax.annotation.Nullable;
 import javax.inject.Inject;
@@ -80,13 +79,13 @@ public class ContactExchangeActivity extends KeyAgreementActivity {
 
 	@UiThread
 	private void contactExchangeFailed() {
-		showErrorFragment();
+		showErrorFragment(R.string.connection_error_explanation);
 	}
 
 	@UiThread
 	@Override
 	public void keyAgreementFailed() {
-		showErrorFragment();
+		showErrorFragment(R.string.connection_error_explanation);
 	}
 
 	@UiThread
@@ -104,7 +103,7 @@ public class ContactExchangeActivity extends KeyAgreementActivity {
 	@UiThread
 	@Override
 	public void keyAgreementAborted(boolean remoteAborted) {
-		showErrorFragment();
+		showErrorFragment(R.string.connection_error_explanation);
 	}
 
 	@UiThread
@@ -113,10 +112,4 @@ public class ContactExchangeActivity extends KeyAgreementActivity {
 		startContactExchange(result);
 		return getString(R.string.exchanging_contact_details);
 	}
-
-	protected void showErrorFragment() {
-		String errorMsg = getString(R.string.connection_error_explanation);
-		BaseFragment f = ContactExchangeErrorFragment.newInstance(errorMsg);
-		showNextFragment(f);
-	}
 }

briar-android/src/main/java/org/briarproject/briar/android/keyagreement/KeyAgreementActivity.java

@@ -8,18 +8,10 @@ import android.content.IntentFilter;
 import android.os.Bundle;
 import android.view.MenuItem;
 
-import org.briarproject.bramble.api.event.Event;
 import org.briarproject.bramble.api.event.EventBus;
-import org.briarproject.bramble.api.event.EventListener;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
-import org.briarproject.bramble.api.plugin.BluetoothConstants;
-import org.briarproject.bramble.api.plugin.LanTcpConstants;
-import org.briarproject.bramble.api.plugin.Plugin;
-import org.briarproject.bramble.api.plugin.Plugin.State;
-import org.briarproject.bramble.api.plugin.PluginManager;
 import org.briarproject.bramble.api.plugin.event.BluetoothEnabledEvent;
-import org.briarproject.bramble.api.plugin.event.TransportStateEvent;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.activity.ActivityComponent;
 import org.briarproject.briar.android.activity.BriarActivity;
@@ -45,15 +37,13 @@ import static android.Manifest.permission.ACCESS_COARSE_LOCATION;
 import static android.Manifest.permission.CAMERA;
 import static android.bluetooth.BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE;
 import static android.bluetooth.BluetoothAdapter.ACTION_SCAN_MODE_CHANGED;
+import static android.bluetooth.BluetoothAdapter.ACTION_STATE_CHANGED;
+import static android.bluetooth.BluetoothAdapter.EXTRA_SCAN_MODE;
+import static android.bluetooth.BluetoothAdapter.EXTRA_STATE;
+import static android.bluetooth.BluetoothAdapter.SCAN_MODE_CONNECTABLE;
 import static android.bluetooth.BluetoothAdapter.SCAN_MODE_CONNECTABLE_DISCOVERABLE;
+import static android.bluetooth.BluetoothAdapter.STATE_ON;
 import static android.content.pm.PackageManager.PERMISSION_GRANTED;
-import static java.util.logging.Level.INFO;
-import static java.util.logging.Logger.getLogger;
-import static org.briarproject.bramble.api.nullsafety.NullSafety.requireNonNull;
-import static org.briarproject.bramble.api.plugin.Plugin.State.ACTIVE;
-import static org.briarproject.bramble.api.plugin.Plugin.State.DISABLED;
-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.briar.android.activity.RequestCodes.REQUEST_BLUETOOTH_DISCOVERABLE;
 import static org.briarproject.briar.android.activity.RequestCodes.REQUEST_PERMISSION_CAMERA_LOCATION;
 
@@ -61,33 +51,10 @@ import static org.briarproject.briar.android.activity.RequestCodes.REQUEST_PERMI
 @ParametersNotNullByDefault
 public abstract class KeyAgreementActivity extends BriarActivity implements
 		BaseFragmentListener, IntroScreenSeenListener,
-		KeyAgreementEventListener, EventListener {
+		KeyAgreementEventListener {
 
-	private enum BluetoothDecision {
-		/**
-		 * We haven't asked the user about Bluetooth discoverability.
-		 */
-		UNKNOWN,
-
-		/**
-		 * The device doesn't have a Bluetooth adapter.
-		 */
-		NO_ADAPTER,
-
-		/**
-		 * We're waiting for the user to accept or refuse discoverability.
-		 */
-		WAITING,
-
-		/**
-		 * The user has accepted discoverability.
-		 */
-		ACCEPTED,
-
-		/**
-		 * The user has refused discoverability.
-		 */
-		REFUSED
+	private enum BluetoothState {
+		UNKNOWN, NO_ADAPTER, WAITING, REFUSED, ENABLED, DISCOVERABLE
 	}
 
 	private enum Permission {
@@ -95,14 +62,11 @@ public abstract class KeyAgreementActivity extends BriarActivity implements
 	}
 
 	private static final Logger LOG =
-			getLogger(KeyAgreementActivity.class.getName());
+			Logger.getLogger(KeyAgreementActivity.class.getName());
 
 	@Inject
 	EventBus eventBus;
 
-	@Inject
-	PluginManager pluginManager;
-
 	/**
 	 * Set to true in onPostResume() and false in onPause(). This prevents the
 	 * QR code fragment from being shown if onRequestPermissionsResult() is
@@ -110,36 +74,21 @@ public abstract class KeyAgreementActivity extends BriarActivity implements
 	 * https://issuetracker.google.com/issues/37067655.
 	 */
 	private boolean isResumed = false;
-
 	/**
 	 * Set to true when the continue button is clicked, and false when the QR
 	 * code fragment is shown. This prevents the QR code fragment from being
 	 * shown automatically before the continue button has been clicked.
 	 */
 	private boolean continueClicked = false;
-
 	/**
 	 * Records whether the Bluetooth adapter was already enabled before we
 	 * asked for Bluetooth discoverability, so we know whether to broadcast a
 	 * {@link BluetoothEnabledEvent}.
 	 */
 	private boolean wasAdapterEnabled = false;
-
-	/**
-	 * Records whether we've enabled the wifi plugin so we don't enable it more
-	 * than once.
-	 */
-	private boolean hasEnabledWifi = false;
-
-	/**
-	 * Records whether we've enabled the Bluetooth plugin so we don't enable it
-	 * more than once.
-	 */
-	private boolean hasEnabledBluetooth = false;
-
 	private Permission cameraPermission = Permission.UNKNOWN;
 	private Permission locationPermission = Permission.UNKNOWN;
-	private BluetoothDecision bluetoothDecision = BluetoothDecision.UNKNOWN;
+	private BluetoothState bluetoothState = BluetoothState.UNKNOWN;
 	private BroadcastReceiver bluetoothReceiver = null;
 
 	@Override
@@ -147,17 +96,20 @@ public abstract class KeyAgreementActivity extends BriarActivity implements
 		component.inject(this);
 	}
 
+	@SuppressWarnings("ConstantConditions")
 	@Override
 	public void onCreate(@Nullable Bundle state) {
 		super.onCreate(state);
 		setContentView(R.layout.activity_fragment_container_toolbar);
 		Toolbar toolbar = findViewById(R.id.toolbar);
 		setSupportActionBar(toolbar);
-		requireNonNull(getSupportActionBar()).setDisplayHomeAsUpEnabled(true);
+		getSupportActionBar().setDisplayHomeAsUpEnabled(true);
 		if (state == null) {
 			showInitialFragment(IntroFragment.newInstance());
 		}
-		IntentFilter filter = new IntentFilter(ACTION_SCAN_MODE_CHANGED);
+		IntentFilter filter = new IntentFilter();
+		filter.addAction(ACTION_STATE_CHANGED);
+		filter.addAction(ACTION_SCAN_MODE_CHANGED);
 		bluetoothReceiver = new BluetoothStateReceiver();
 		registerReceiver(bluetoothReceiver, filter);
 	}
@@ -170,17 +122,18 @@ public abstract class KeyAgreementActivity extends BriarActivity implements
 
 	@Override
 	public boolean onOptionsItemSelected(MenuItem item) {
-		if (item.getItemId() == android.R.id.home) {
-			onBackPressed();
-			return true;
+		switch (item.getItemId()) {
+			case android.R.id.home:
+				onBackPressed();
+				return true;
+			default:
+				return super.onOptionsItemSelected(item);
 		}
-		return super.onOptionsItemSelected(item);
 	}
 
 	@Override
 	public void onStart() {
 		super.onStart();
-		eventBus.addListener(this);
 		// Permissions may have been granted manually while we were stopped
 		cameraPermission = Permission.UNKNOWN;
 		locationPermission = Permission.UNKNOWN;
@@ -197,22 +150,11 @@ public abstract class KeyAgreementActivity extends BriarActivity implements
 
 	private void showQrCodeFragmentIfAllowed() {
 		if (isResumed && continueClicked && areEssentialPermissionsGranted()) {
-			if (isWifiReady() && isBluetoothReady()) {
-				LOG.info("Wifi and Bluetooth are ready");
+			if (bluetoothState == BluetoothState.UNKNOWN ||
+					bluetoothState == BluetoothState.ENABLED) {
+				requestBluetoothDiscoverable();
+			} else if (bluetoothState != BluetoothState.WAITING) {
 				showQrCodeFragment();
-			} else {
-				if (shouldEnableWifi()) {
-					LOG.info("Enabling wifi plugin");
-					hasEnabledWifi = true;
-					pluginManager.setPluginEnabled(LanTcpConstants.ID, true);
-				}
-				if (bluetoothDecision == BluetoothDecision.UNKNOWN) {
-					requestBluetoothDiscoverable();
-				} else if (shouldEnableBluetooth()) {
-					LOG.info("Enabling Bluetooth plugin");
-					hasEnabledBluetooth = true;
-					pluginManager.setPluginEnabled(BluetoothConstants.ID, true);
-				}
 			}
 		}
 	}
@@ -225,108 +167,57 @@ public abstract class KeyAgreementActivity extends BriarActivity implements
 						locationPermission == Permission.PERMANENTLY_DENIED);
 	}
 
-	private boolean isWifiReady() {
-		Plugin p = pluginManager.getPlugin(LanTcpConstants.ID);
-		if (p == null) return true; // Continue without wifi
-		State state = p.getState();
-		// Wait for plugin to become enabled
-		return state == ACTIVE || state == INACTIVE;
-	}
-
-	private boolean isBluetoothReady() {
-		if (bluetoothDecision == BluetoothDecision.UNKNOWN ||
-				bluetoothDecision == BluetoothDecision.WAITING) {
-			// Wait for decision
-			return false;
-		}
-		if (bluetoothDecision == BluetoothDecision.NO_ADAPTER
-				|| bluetoothDecision == BluetoothDecision.REFUSED) {
-			// Continue without Bluetooth
-			return true;
-		}
-		BluetoothAdapter bt = BluetoothAdapter.getDefaultAdapter();
-		if (bt == null) return true; // Continue without Bluetooth
-		if (bt.getScanMode() != SCAN_MODE_CONNECTABLE_DISCOVERABLE) {
-			// Wait for adapter to become discoverable
-			return false;
-		}
-		Plugin p = pluginManager.getPlugin(BluetoothConstants.ID);
-		if (p == null) return true; // Continue without Bluetooth
-		// Wait for plugin to become active
-		return p.getState() == ACTIVE;
-	}
-
-	private boolean shouldEnableWifi() {
-		if (hasEnabledWifi) return false;
-		Plugin p = pluginManager.getPlugin(LanTcpConstants.ID);
-		if (p == null) return false;
-		State state = p.getState();
-		return state == STARTING_STOPPING || state == DISABLED;
-	}
-
-	private void requestBluetoothDiscoverable() {
-		BluetoothAdapter bt = BluetoothAdapter.getDefaultAdapter();
-		if (bt == null) {
-			bluetoothDecision = BluetoothDecision.NO_ADAPTER;
-			showQrCodeFragmentIfAllowed();
-		} else {
-			Intent i = new Intent(ACTION_REQUEST_DISCOVERABLE);
-			if (i.resolveActivity(getPackageManager()) != null) {
-				LOG.info("Asking for Bluetooth discoverability");
-				bluetoothDecision = BluetoothDecision.WAITING;
-				wasAdapterEnabled = bt.isEnabled();
-				startActivityForResult(i, REQUEST_BLUETOOTH_DISCOVERABLE);
-			} else {
-				bluetoothDecision = BluetoothDecision.NO_ADAPTER;
-				showQrCodeFragmentIfAllowed();
-			}
-		}
-	}
-
-	private boolean shouldEnableBluetooth() {
-		if (bluetoothDecision != BluetoothDecision.ACCEPTED) return false;
-		if (hasEnabledBluetooth) return false;
-		Plugin p = pluginManager.getPlugin(BluetoothConstants.ID);
-		if (p == null) return false;
-		State state = p.getState();
-		return state == STARTING_STOPPING || state == DISABLED;
-	}
-
 	@Override
 	protected void onPause() {
 		super.onPause();
 		isResumed = false;
 	}
 
-	@Override
-	protected void onStop() {
-		super.onStop();
-		eventBus.removeListener(this);
-	}
-
 	@Override
 	public void showNextScreen() {
 		continueClicked = true;
 		if (checkPermissions()) showQrCodeFragmentIfAllowed();
 	}
 
+	private void requestBluetoothDiscoverable() {
+		BluetoothAdapter bt = BluetoothAdapter.getDefaultAdapter();
+		if (bt == null) {
+			setBluetoothState(BluetoothState.NO_ADAPTER);
+		} else {
+			Intent i = new Intent(ACTION_REQUEST_DISCOVERABLE);
+			if (i.resolveActivity(getPackageManager()) != null) {
+				setBluetoothState(BluetoothState.WAITING);
+				wasAdapterEnabled = bt.isEnabled();
+				startActivityForResult(i, REQUEST_BLUETOOTH_DISCOVERABLE);
+			} else {
+				setBluetoothState(BluetoothState.NO_ADAPTER);
+			}
+		}
+	}
+
+	private void setBluetoothState(BluetoothState bluetoothState) {
+		LOG.info("Setting Bluetooth state to " + bluetoothState);
+		this.bluetoothState = bluetoothState;
+		if (!wasAdapterEnabled && bluetoothState == BluetoothState.ENABLED) {
+			eventBus.broadcast(new BluetoothEnabledEvent());
+			wasAdapterEnabled = true;
+		}
+		showQrCodeFragmentIfAllowed();
+	}
+
 	@Override
-	public void onActivityResult(int request, int result,
-			@Nullable Intent data) {
+	public void onActivityResult(int request, int result, Intent data) {
 		if (request == REQUEST_BLUETOOTH_DISCOVERABLE) {
 			if (result == RESULT_CANCELED) {
-				LOG.info("Bluetooth discoverability was refused");
-				bluetoothDecision = BluetoothDecision.REFUSED;
+				setBluetoothState(BluetoothState.REFUSED);
 			} else {
-				LOG.info("Bluetooth discoverability was accepted");
-				bluetoothDecision = BluetoothDecision.ACCEPTED;
-				if (!wasAdapterEnabled) {
-					LOG.info("Bluetooth adapter was enabled by us");
-					eventBus.broadcast(new BluetoothEnabledEvent());
-					wasAdapterEnabled = true;
-				}
+				// If Bluetooth is already discoverable, show the QR code -
+				// otherwise wait for the state or scan mode to change
+				BluetoothAdapter bt = BluetoothAdapter.getDefaultAdapter();
+				if (bt == null) throw new AssertionError();
+				if (bt.getScanMode() == SCAN_MODE_CONNECTABLE_DISCOVERABLE)
+					setBluetoothState(BluetoothState.DISCOVERABLE);
 			}
-			showQrCodeFragmentIfAllowed();
 		} else super.onActivityResult(request, result, data);
 	}
 
@@ -336,12 +227,7 @@ public abstract class KeyAgreementActivity extends BriarActivity implements
 		continueClicked = false;
 		// If we return to the intro fragment, ask for Bluetooth
 		// discoverability again before showing the QR code fragment
-		bluetoothDecision = BluetoothDecision.UNKNOWN;
-		// If we return to the intro fragment, we may need to enable wifi and
-		// Bluetooth again
-		hasEnabledWifi = false;
-		hasEnabledBluetooth = false;
-
+		bluetoothState = BluetoothState.UNKNOWN;
 		// FIXME #824
 		FragmentManager fm = getSupportFragmentManager();
 		if (fm.findFragmentByTag(KeyAgreementFragment.TAG) == null) {
@@ -353,6 +239,12 @@ public abstract class KeyAgreementActivity extends BriarActivity implements
 		}
 	}
 
+	protected void showErrorFragment(@StringRes int errorResId) {
+		String errorMsg = getString(errorResId);
+		BaseFragment f = ContactExchangeErrorFragment.newInstance(errorMsg);
+		showNextFragment(f);
+	}
+
 	private boolean checkPermissions() {
 		if (areEssentialPermissionsGranted()) return true;
 		// If the camera permission has been permanently denied, ask the
@@ -443,30 +335,24 @@ public abstract class KeyAgreementActivity extends BriarActivity implements
 				permission);
 	}
 
-	@Override
-	public void eventOccurred(Event e) {
-		if (e instanceof TransportStateEvent) {
-			TransportStateEvent t = (TransportStateEvent) e;
-			if (t.getTransportId().equals(BluetoothConstants.ID)) {
-				if (LOG.isLoggable(INFO)) {
-					LOG.info("Bluetooth state changed to " + t.getState());
-				}
-				showQrCodeFragmentIfAllowed();
-			} else if (t.getTransportId().equals(LanTcpConstants.ID)) {
-				if (LOG.isLoggable(INFO)) {
-					LOG.info("Wifi state changed to " + t.getState());
-				}
-				showQrCodeFragmentIfAllowed();
-			}
-		}
-	}
-
 	private class BluetoothStateReceiver extends BroadcastReceiver {
 
 		@Override
 		public void onReceive(Context context, Intent intent) {
-			LOG.info("Bluetooth scan mode changed");
-			showQrCodeFragmentIfAllowed();
+			String action = intent.getAction();
+			if (ACTION_STATE_CHANGED.equals(action)) {
+				int state = intent.getIntExtra(EXTRA_STATE, 0);
+				if (state == STATE_ON)
+					setBluetoothState(BluetoothState.ENABLED);
+				else setBluetoothState(BluetoothState.UNKNOWN);
+			} else if (ACTION_SCAN_MODE_CHANGED.equals(action)) {
+				int scanMode = intent.getIntExtra(EXTRA_SCAN_MODE, 0);
+				if (scanMode == SCAN_MODE_CONNECTABLE_DISCOVERABLE)
+					setBluetoothState(BluetoothState.DISCOVERABLE);
+				else if (scanMode == SCAN_MODE_CONNECTABLE)
+					setBluetoothState(BluetoothState.ENABLED);
+				else setBluetoothState(BluetoothState.UNKNOWN);
+			}
 		}
 	}
 }

briar-android/src/main/java/org/briarproject/briar/android/navdrawer/NavDrawerActivity.java

@@ -1,5 +1,6 @@
 package org.briarproject.briar.android.navdrawer;
 
+import android.annotation.SuppressLint;
 import android.content.Intent;
 import android.content.res.Configuration;
 import android.net.Uri;
@@ -22,7 +23,6 @@ import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.bramble.api.plugin.BluetoothConstants;
 import org.briarproject.bramble.api.plugin.LanTcpConstants;
-import org.briarproject.bramble.api.plugin.Plugin.State;
 import org.briarproject.bramble.api.plugin.TorConstants;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.briar.R;
@@ -30,6 +30,7 @@ import org.briarproject.briar.android.activity.ActivityComponent;
 import org.briarproject.briar.android.activity.BriarActivity;
 import org.briarproject.briar.android.blog.FeedFragment;
 import org.briarproject.briar.android.contact.ContactListFragment;
+import org.briarproject.briar.android.controller.handler.UiResultHandler;
 import org.briarproject.briar.android.forum.ForumListFragment;
 import org.briarproject.briar.android.fragment.BaseFragment;
 import org.briarproject.briar.android.fragment.BaseFragment.BaseFragmentListener;
@@ -43,11 +44,9 @@ import java.util.logging.Logger;
 
 import javax.inject.Inject;
 
-import androidx.annotation.ColorRes;
-import androidx.annotation.DrawableRes;
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
-import androidx.annotation.StringRes;
+import androidx.annotation.UiThread;
 import androidx.appcompat.app.ActionBar;
 import androidx.appcompat.app.ActionBarDrawerToggle;
 import androidx.appcompat.widget.Toolbar;
@@ -56,8 +55,6 @@ import androidx.core.content.ContextCompat;
 import androidx.drawerlayout.widget.DrawerLayout;
 import androidx.fragment.app.FragmentManager;
 import androidx.fragment.app.FragmentTransaction;
-import androidx.lifecycle.ViewModelProvider;
-import androidx.lifecycle.ViewModelProviders;
 
 import static android.view.View.GONE;
 import static android.view.View.VISIBLE;
@@ -67,9 +64,6 @@ import static androidx.fragment.app.FragmentManager.POP_BACK_STACK_INCLUSIVE;
 import static java.util.Objects.requireNonNull;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState.RUNNING;
-import static org.briarproject.bramble.api.plugin.Plugin.State.ACTIVE;
-import static org.briarproject.bramble.api.plugin.Plugin.State.ENABLING;
-import static org.briarproject.bramble.api.plugin.Plugin.State.STARTING_STOPPING;
 import static org.briarproject.briar.android.BriarService.EXTRA_STARTUP_FAILED;
 import static org.briarproject.briar.android.activity.RequestCodes.REQUEST_PASSWORD;
 import static org.briarproject.briar.android.navdrawer.IntentRouter.handleExternalIntent;
@@ -78,7 +72,8 @@ import static org.briarproject.briar.android.util.UiUtils.getDaysUntilExpiry;
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
 public class NavDrawerActivity extends BriarActivity implements
-		BaseFragmentListener, OnNavigationItemSelectedListener {
+		BaseFragmentListener, TransportStateListener,
+		OnNavigationItemSelectedListener {
 
 	private static final Logger LOG =
 			getLogger(NavDrawerActivity.class.getName());
@@ -96,13 +91,10 @@ public class NavDrawerActivity extends BriarActivity implements
 	public static Uri SIGN_OUT_URI =
 			Uri.parse("briar-content://org.briarproject.briar/sign-out");
 
-	private NavDrawerViewModel navDrawerViewModel;
-	private PluginViewModel pluginViewModel;
 	private ActionBarDrawerToggle drawerToggle;
 
 	@Inject
-	ViewModelProvider.Factory viewModelFactory;
-
+	NavDrawerController controller;
 	@Inject
 	LifecycleManager lifecycleManager;
 
@@ -123,17 +115,6 @@ public class NavDrawerActivity extends BriarActivity implements
 		exitIfStartupFailed(getIntent());
 		setContentView(R.layout.activity_nav_drawer);
 
-		ViewModelProvider provider =
-				ViewModelProviders.of(this, viewModelFactory);
-		navDrawerViewModel = provider.get(NavDrawerViewModel.class);
-		pluginViewModel = provider.get(PluginViewModel.class);
-
-		navDrawerViewModel.showExpiryWarning()
-				.observe(this, this::showExpiryWarning);
-		navDrawerViewModel.shouldAskForDozeWhitelisting().observe(this, ask -> {
-			if (ask) showDozeDialog(getString(R.string.setup_doze_intro));
-		});
-
 		Toolbar toolbar = findViewById(R.id.toolbar);
 		drawerLayout = findViewById(R.id.drawer_layout);
 		navigation = findViewById(R.id.navigation);
@@ -150,7 +131,7 @@ public class NavDrawerActivity extends BriarActivity implements
 		drawerLayout.addDrawerListener(drawerToggle);
 		navigation.setNavigationItemSelectedListener(this);
 
-		initializeTransports();
+		initializeTransports(getLayoutInflater());
 		transportsView.setAdapter(transportsAdapter);
 
 		lockManager.isLockable().observe(this, this::setLockVisible);
@@ -168,10 +149,17 @@ public class NavDrawerActivity extends BriarActivity implements
 	}
 
 	@Override
+	@SuppressLint("NewApi")
 	public void onStart() {
 		super.onStart();
+		updateTransports();
 		lockManager.checkIfLockable();
-		navDrawerViewModel.checkExpiryWarning();
+		controller.showExpiryWarning(new UiResultHandler<Boolean>(this) {
+			@Override
+			public void onResultUi(Boolean expiry) {
+				if (expiry) showExpiryWarning();
+			}
+		});
 	}
 
 	@Override
@@ -179,7 +167,16 @@ public class NavDrawerActivity extends BriarActivity implements
 			@Nullable Intent data) {
 		super.onActivityResult(request, result, data);
 		if (request == REQUEST_PASSWORD && result == RESULT_OK) {
-			navDrawerViewModel.checkDozeWhitelisting();
+			controller.shouldAskForDozeWhitelisting(this,
+					new UiResultHandler<Boolean>(this) {
+						@Override
+						public void onResultUi(Boolean ask) {
+							if (ask) {
+								showDozeDialog(
+										getString(R.string.setup_doze_intro));
+							}
+						}
+					});
 		}
 	}
 
@@ -349,37 +346,55 @@ public class NavDrawerActivity extends BriarActivity implements
 		if (item != null) item.setVisible(visible);
 	}
 
-	private void showExpiryWarning(boolean show) {
+	private void showExpiryWarning() {
 		int daysUntilExpiry = getDaysUntilExpiry();
-		if (daysUntilExpiry < 0) {
-			signOut();
-			return;
-		}
+		if (daysUntilExpiry < 0) signOut();
 
+		// show expiry warning text
 		ViewGroup expiryWarning = findViewById(R.id.expiryWarning);
-		if (show) {
-			// show expiry warning text
-			TextView expiryWarningText =
-					expiryWarning.findViewById(R.id.expiryWarningText);
-			String text = getResources().getQuantityString(
-					R.plurals.expiry_warning, daysUntilExpiry, daysUntilExpiry);
-			expiryWarningText.setText(text);
-			// make close button functional
-			ImageView expiryWarningClose =
-					expiryWarning.findViewById(R.id.expiryWarningClose);
-			expiryWarningClose.setOnClickListener(v ->
-					navDrawerViewModel.expiryWarningDismissed());
-			expiryWarning.setVisibility(VISIBLE);
-		} else {
+		TextView expiryWarningText =
+				expiryWarning.findViewById(R.id.expiryWarningText);
+		// make close button functional
+		ImageView expiryWarningClose =
+				expiryWarning.findViewById(R.id.expiryWarningClose);
+
+		expiryWarningText.setText(getResources()
+				.getQuantityString(R.plurals.expiry_warning,
+						daysUntilExpiry, daysUntilExpiry));
+
+		expiryWarningClose.setOnClickListener(v -> {
+			controller.expiryWarningDismissed();
 			expiryWarning.setVisibility(GONE);
-		}
+		});
+
+		expiryWarning.setVisibility(VISIBLE);
 	}
 
-	private void initializeTransports() {
+	private void initializeTransports(LayoutInflater inflater) {
 		transports = new ArrayList<>(3);
 
-		transportsAdapter = new BaseAdapter() {
+		Transport tor = new Transport();
+		tor.id = TorConstants.ID;
+		tor.enabled = controller.isTransportRunning(tor.id);
+		tor.iconId = R.drawable.transport_tor;
+		tor.textId = R.string.transport_tor;
+		transports.add(tor);
 
+		Transport bt = new Transport();
+		bt.id = BluetoothConstants.ID;
+		bt.enabled = controller.isTransportRunning(bt.id);
+		bt.iconId = R.drawable.transport_bt;
+		bt.textId = R.string.transport_bt;
+		transports.add(bt);
+
+		Transport lan = new Transport();
+		lan.id = LanTcpConstants.ID;
+		lan.enabled = controller.isTransportRunning(lan.id);
+		lan.iconId = R.drawable.transport_lan;
+		lan.textId = R.string.transport_lan;
+		transports.add(lan);
+
+		transportsAdapter = new BaseAdapter() {
 			@Override
 			public int getCount() {
 				return transports.size();
@@ -402,67 +417,63 @@ public class NavDrawerActivity extends BriarActivity implements
 				if (convertView != null) {
 					view = convertView;
 				} else {
-					LayoutInflater inflater = getLayoutInflater();
 					view = inflater.inflate(R.layout.list_item_transport,
 							parent, false);
 				}
 
 				Transport t = getItem(position);
+				int c;
+				if (t.enabled) {
+					c = ContextCompat.getColor(NavDrawerActivity.this,
+							R.color.briar_green_light);
+				} else {
+					c = ContextCompat.getColor(NavDrawerActivity.this,
+							android.R.color.tertiary_text_light);
+				}
 
 				ImageView icon = view.findViewById(R.id.imageView);
-				icon.setImageDrawable(ContextCompat.getDrawable(
-						NavDrawerActivity.this, t.iconDrawable));
-				icon.setColorFilter(ContextCompat.getColor(
-						NavDrawerActivity.this, t.iconColor));
+				icon.setImageDrawable(ContextCompat
+						.getDrawable(NavDrawerActivity.this, t.iconId));
+				icon.setColorFilter(c);
 
 				TextView text = view.findViewById(R.id.textView);
-				text.setText(getString(t.label));
+				text.setText(getString(t.textId));
 
 				return view;
 			}
 		};
-
-		transports.add(createTransport(TorConstants.ID,
-				R.drawable.transport_tor, R.string.transport_tor));
-		transports.add(createTransport(LanTcpConstants.ID,
-				R.drawable.transport_lan, R.string.transport_lan));
-		transports.add(createTransport(BluetoothConstants.ID,
-				R.drawable.transport_bt, R.string.transport_bt));
 	}
 
-	@ColorRes
-	private int getIconColor(State state) {
-		if (state == ACTIVE) return R.color.briar_lime_400;
-		else if (state == ENABLING) return R.color.briar_orange_500;
-		else return android.R.color.tertiary_text_light;
+	@UiThread
+	private void setTransport(TransportId id, boolean enabled) {
+		if (transports == null || transportsAdapter == null) return;
+		for (Transport t : transports) {
+			if (t.id.equals(id)) {
+				t.enabled = enabled;
+				transportsAdapter.notifyDataSetChanged();
+				break;
+			}
+		}
 	}
 
-	private Transport createTransport(TransportId id,
-			@DrawableRes int iconDrawable, @StringRes int label) {
-		int iconColor = getIconColor(STARTING_STOPPING);
-		Transport transport = new Transport(iconDrawable, label, iconColor);
-		pluginViewModel.getPluginState(id).observe(this, state -> {
-			transport.iconColor = getIconColor(state);
-			transportsAdapter.notifyDataSetChanged();
-		});
-		return transport;
+	private void updateTransports() {
+		if (transports == null || transportsAdapter == null) return;
+		for (Transport t : transports) {
+			t.enabled = controller.isTransportRunning(t.id);
+		}
+		transportsAdapter.notifyDataSetChanged();
+	}
+
+	@Override
+	public void stateUpdate(TransportId id, boolean enabled) {
+		setTransport(id, enabled);
 	}
 
 	private static class Transport {
 
-		@DrawableRes
-		private final int iconDrawable;
-		@StringRes
-		private final int label;
-
-		@ColorRes
-		private int iconColor;
-
-		private Transport(@DrawableRes int iconDrawable, @StringRes int label,
-				@ColorRes int iconColor) {
-			this.iconDrawable = iconDrawable;
-			this.label = label;
-			this.iconColor = iconColor;
-		}
+		private TransportId id;
+		private boolean enabled;
+		private int iconId;
+		private int textId;
 	}
 }

briar-android/src/main/java/org/briarproject/briar/android/navdrawer/NavDrawerController.java

@@ -0,0 +1,22 @@
+package org.briarproject.briar.android.navdrawer;
+
+import android.content.Context;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.TransportId;
+import org.briarproject.briar.android.controller.ActivityLifecycleController;
+import org.briarproject.briar.android.controller.handler.ResultHandler;
+
+@NotNullByDefault
+public interface NavDrawerController extends ActivityLifecycleController {
+
+	boolean isTransportRunning(TransportId transportId);
+
+	void showExpiryWarning(ResultHandler<Boolean> handler);
+
+	void expiryWarningDismissed();
+
+	void shouldAskForDozeWhitelisting(Context ctx,
+			ResultHandler<Boolean> handler);
+
+}

briar-android/src/main/java/org/briarproject/briar/android/navdrawer/NavDrawerControllerImpl.java

@@ -0,0 +1,182 @@
+package org.briarproject.briar.android.navdrawer;
+
+import android.app.Activity;
+import android.content.Context;
+
+import org.briarproject.bramble.api.db.DatabaseExecutor;
+import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.bramble.api.event.Event;
+import org.briarproject.bramble.api.event.EventBus;
+import org.briarproject.bramble.api.event.EventListener;
+import org.briarproject.bramble.api.lifecycle.LifecycleManager;
+import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
+import org.briarproject.bramble.api.plugin.Plugin;
+import org.briarproject.bramble.api.plugin.PluginManager;
+import org.briarproject.bramble.api.plugin.TransportId;
+import org.briarproject.bramble.api.plugin.event.TransportDisabledEvent;
+import org.briarproject.bramble.api.plugin.event.TransportEnabledEvent;
+import org.briarproject.bramble.api.settings.Settings;
+import org.briarproject.bramble.api.settings.SettingsManager;
+import org.briarproject.briar.android.controller.DbControllerImpl;
+import org.briarproject.briar.android.controller.handler.ResultHandler;
+
+import java.util.concurrent.Executor;
+import java.util.logging.Logger;
+
+import javax.inject.Inject;
+
+import static java.util.concurrent.TimeUnit.DAYS;
+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.util.LogUtils.logException;
+import static org.briarproject.briar.android.TestingConstants.EXPIRY_DATE;
+import static org.briarproject.briar.android.TestingConstants.IS_DEBUG_BUILD;
+import static org.briarproject.briar.android.controller.BriarControllerImpl.DOZE_ASK_AGAIN;
+import static org.briarproject.briar.android.settings.SettingsFragment.SETTINGS_NAMESPACE;
+import static org.briarproject.briar.android.util.UiUtils.needsDozeWhitelisting;
+
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
+public class NavDrawerControllerImpl extends DbControllerImpl
+		implements NavDrawerController, EventListener {
+
+	private static final Logger LOG =
+			getLogger(NavDrawerControllerImpl.class.getName());
+
+	private static final String EXPIRY_DATE_WARNING = "expiryDateWarning";
+
+	private final PluginManager pluginManager;
+	private final SettingsManager settingsManager;
+	private final EventBus eventBus;
+
+	// UI thread
+	private TransportStateListener listener;
+
+	@Inject
+	NavDrawerControllerImpl(@DatabaseExecutor Executor dbExecutor,
+			LifecycleManager lifecycleManager, PluginManager pluginManager,
+			SettingsManager settingsManager, EventBus eventBus) {
+		super(dbExecutor, lifecycleManager);
+		this.pluginManager = pluginManager;
+		this.settingsManager = settingsManager;
+		this.eventBus = eventBus;
+	}
+
+	@Override
+	public void onActivityCreate(Activity activity) {
+		listener = (TransportStateListener) activity;
+	}
+
+	@Override
+	public void onActivityStart() {
+		eventBus.addListener(this);
+	}
+
+	@Override
+	public void onActivityStop() {
+		eventBus.removeListener(this);
+	}
+
+	@Override
+	public void onActivityDestroy() {
+	}
+
+	@Override
+	public void eventOccurred(Event e) {
+		if (e instanceof TransportEnabledEvent) {
+			TransportId id = ((TransportEnabledEvent) e).getTransportId();
+			if (LOG.isLoggable(INFO)) {
+				LOG.info("TransportEnabledEvent: " + id.getString());
+			}
+			listener.stateUpdate(id, true);
+		} else if (e instanceof TransportDisabledEvent) {
+			TransportId id = ((TransportDisabledEvent) e).getTransportId();
+			if (LOG.isLoggable(INFO)) {
+				LOG.info("TransportDisabledEvent: " + id.getString());
+			}
+			listener.stateUpdate(id, false);
+		}
+	}
+
+	@Override
+	public void showExpiryWarning(ResultHandler<Boolean> handler) {
+		if (!IS_DEBUG_BUILD) {
+			handler.onResult(false);
+			return;
+		}
+		runOnDbThread(() -> {
+			try {
+				Settings settings =
+						settingsManager.getSettings(SETTINGS_NAMESPACE);
+				int warningInt = settings.getInt(EXPIRY_DATE_WARNING, 0);
+
+				if (warningInt == 0) {
+					// we have not warned before
+					handler.onResult(true);
+				} else {
+					long warningLong = warningInt * 1000L;
+					long now = System.currentTimeMillis();
+					long daysSinceLastWarning =
+							(now - warningLong) / DAYS.toMillis(1);
+					long daysBeforeExpiry =
+							(EXPIRY_DATE - now) / DAYS.toMillis(1);
+
+					if (daysSinceLastWarning >= 30) {
+						handler.onResult(true);
+					} else if (daysBeforeExpiry <= 3 &&
+							daysSinceLastWarning > 0) {
+						handler.onResult(true);
+					} else {
+						handler.onResult(false);
+					}
+				}
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+			}
+		});
+	}
+
+	@Override
+	public void expiryWarningDismissed() {
+		runOnDbThread(() -> {
+			try {
+				Settings settings = new Settings();
+				int date = (int) (System.currentTimeMillis() / 1000L);
+				settings.putInt(EXPIRY_DATE_WARNING, date);
+				settingsManager.mergeSettings(settings, SETTINGS_NAMESPACE);
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+			}
+		});
+	}
+
+	@Override
+	public void shouldAskForDozeWhitelisting(Context ctx,
+			ResultHandler<Boolean> handler) {
+		// check this first, to hit the DbThread only when really necessary
+		if (!needsDozeWhitelisting(ctx)) {
+			handler.onResult(false);
+			return;
+		}
+		runOnDbThread(() -> {
+			try {
+				Settings settings =
+						settingsManager.getSettings(SETTINGS_NAMESPACE);
+				boolean ask = settings.getBoolean(DOZE_ASK_AGAIN, true);
+				handler.onResult(ask);
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+				handler.onResult(true);
+			}
+		});
+	}
+
+	@Override
+	public boolean isTransportRunning(TransportId transportId) {
+		Plugin plugin = pluginManager.getPlugin(transportId);
+		return plugin != null && plugin.isRunning();
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/navdrawer/NavDrawerModule.java

@@ -1,23 +0,0 @@
-package org.briarproject.briar.android.navdrawer;
-
-import org.briarproject.briar.android.viewmodel.ViewModelKey;
-
-import androidx.lifecycle.ViewModel;
-import dagger.Binds;
-import dagger.Module;
-import dagger.multibindings.IntoMap;
-
-@Module
-public abstract class NavDrawerModule {
-
-	@Binds
-	@IntoMap
-	@ViewModelKey(NavDrawerViewModel.class)
-	abstract ViewModel bindNavDrawerViewModel(
-			NavDrawerViewModel navDrawerViewModel);
-
-	@Binds
-	@IntoMap
-	@ViewModelKey(PluginViewModel.class)
-	abstract ViewModel bindPluginViewModel(PluginViewModel pluginViewModel);
-}

briar-android/src/main/java/org/briarproject/briar/android/navdrawer/NavDrawerViewModel.java

@@ -1,136 +0,0 @@
-package org.briarproject.briar.android.navdrawer;
-
-import android.app.Application;
-
-import org.briarproject.bramble.api.db.DatabaseExecutor;
-import org.briarproject.bramble.api.db.DbException;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.settings.Settings;
-import org.briarproject.bramble.api.settings.SettingsManager;
-
-import java.util.concurrent.Executor;
-import java.util.logging.Logger;
-
-import javax.inject.Inject;
-
-import androidx.annotation.UiThread;
-import androidx.lifecycle.AndroidViewModel;
-import androidx.lifecycle.LiveData;
-import androidx.lifecycle.MutableLiveData;
-
-import static java.util.concurrent.TimeUnit.DAYS;
-import static java.util.logging.Level.WARNING;
-import static java.util.logging.Logger.getLogger;
-import static org.briarproject.bramble.util.LogUtils.logException;
-import static org.briarproject.briar.android.TestingConstants.EXPIRY_DATE;
-import static org.briarproject.briar.android.TestingConstants.IS_DEBUG_BUILD;
-import static org.briarproject.briar.android.controller.BriarControllerImpl.DOZE_ASK_AGAIN;
-import static org.briarproject.briar.android.settings.SettingsFragment.SETTINGS_NAMESPACE;
-import static org.briarproject.briar.android.util.UiUtils.needsDozeWhitelisting;
-
-@NotNullByDefault
-public class NavDrawerViewModel extends AndroidViewModel {
-
-	private static final Logger LOG =
-			getLogger(NavDrawerViewModel.class.getName());
-
-	private static final String EXPIRY_DATE_WARNING = "expiryDateWarning";
-
-	@DatabaseExecutor
-	private final Executor dbExecutor;
-	private final SettingsManager settingsManager;
-
-	private final MutableLiveData<Boolean> showExpiryWarning =
-			new MutableLiveData<>();
-	private final MutableLiveData<Boolean> shouldAskForDozeWhitelisting =
-			new MutableLiveData<>();
-
-	@Inject
-	NavDrawerViewModel(Application app, @DatabaseExecutor Executor dbExecutor,
-			SettingsManager settingsManager) {
-		super(app);
-		this.dbExecutor = dbExecutor;
-		this.settingsManager = settingsManager;
-	}
-
-	LiveData<Boolean> showExpiryWarning() {
-		return showExpiryWarning;
-	}
-
-	@UiThread
-	void checkExpiryWarning() {
-		if (!IS_DEBUG_BUILD) {
-			showExpiryWarning.setValue(false);
-			return;
-		}
-		dbExecutor.execute(() -> {
-			try {
-				Settings settings =
-						settingsManager.getSettings(SETTINGS_NAMESPACE);
-				int warningInt = settings.getInt(EXPIRY_DATE_WARNING, 0);
-
-				if (warningInt == 0) {
-					// we have not warned before
-					showExpiryWarning.postValue(true);
-				} else {
-					long warningLong = warningInt * 1000L;
-					long now = System.currentTimeMillis();
-					long daysSinceLastWarning =
-							(now - warningLong) / DAYS.toMillis(1);
-					long daysBeforeExpiry =
-							(EXPIRY_DATE - now) / DAYS.toMillis(1);
-
-					if (daysSinceLastWarning >= 30) {
-						showExpiryWarning.postValue(true);
-					} else if (daysBeforeExpiry <= 3 &&
-							daysSinceLastWarning > 0) {
-						showExpiryWarning.postValue(true);
-					} else {
-						showExpiryWarning.postValue(false);
-					}
-				}
-			} catch (DbException e) {
-				logException(LOG, WARNING, e);
-			}
-		});
-	}
-
-	@UiThread
-	void expiryWarningDismissed() {
-		showExpiryWarning.setValue(false);
-		dbExecutor.execute(() -> {
-			try {
-				Settings settings = new Settings();
-				int date = (int) (System.currentTimeMillis() / 1000L);
-				settings.putInt(EXPIRY_DATE_WARNING, date);
-				settingsManager.mergeSettings(settings, SETTINGS_NAMESPACE);
-			} catch (DbException e) {
-				logException(LOG, WARNING, e);
-			}
-		});
-	}
-
-	LiveData<Boolean> shouldAskForDozeWhitelisting() {
-		return shouldAskForDozeWhitelisting;
-	}
-
-	@UiThread
-	void checkDozeWhitelisting() {
-		// check this first, to hit the DbThread only when really necessary
-		if (!needsDozeWhitelisting(getApplication())) {
-			shouldAskForDozeWhitelisting.setValue(false);
-			return;
-		}
-		dbExecutor.execute(() -> {
-			try {
-				Settings settings =
-						settingsManager.getSettings(SETTINGS_NAMESPACE);
-				boolean ask = settings.getBoolean(DOZE_ASK_AGAIN, true);
-				shouldAskForDozeWhitelisting.postValue(ask);
-			} catch (DbException e) {
-				logException(LOG, WARNING, e);
-				shouldAskForDozeWhitelisting.postValue(true);
-			}
-		});
-	}
-}

briar-android/src/main/java/org/briarproject/briar/android/navdrawer/PluginViewModel.java

@@ -1,92 +0,0 @@
-package org.briarproject.briar.android.navdrawer;
-
-import org.briarproject.bramble.api.event.Event;
-import org.briarproject.bramble.api.event.EventBus;
-import org.briarproject.bramble.api.event.EventListener;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.plugin.BluetoothConstants;
-import org.briarproject.bramble.api.plugin.LanTcpConstants;
-import org.briarproject.bramble.api.plugin.Plugin;
-import org.briarproject.bramble.api.plugin.Plugin.State;
-import org.briarproject.bramble.api.plugin.PluginManager;
-import org.briarproject.bramble.api.plugin.TorConstants;
-import org.briarproject.bramble.api.plugin.TransportId;
-import org.briarproject.bramble.api.plugin.event.TransportStateEvent;
-
-import java.util.logging.Logger;
-
-import javax.inject.Inject;
-
-import androidx.annotation.Nullable;
-import androidx.lifecycle.LiveData;
-import androidx.lifecycle.MutableLiveData;
-import androidx.lifecycle.ViewModel;
-
-import static java.util.logging.Level.INFO;
-import static java.util.logging.Logger.getLogger;
-import static org.briarproject.bramble.api.plugin.Plugin.State.STARTING_STOPPING;
-
-@NotNullByDefault
-public class PluginViewModel extends ViewModel implements EventListener {
-
-	private static final Logger LOG =
-			getLogger(PluginViewModel.class.getName());
-
-	private final PluginManager pluginManager;
-	private final EventBus eventBus;
-
-	private final MutableLiveData<State> torPluginState =
-			new MutableLiveData<>();
-	private final MutableLiveData<State> wifiPluginState =
-			new MutableLiveData<>();
-	private final MutableLiveData<State> btPluginState =
-			new MutableLiveData<>();
-
-	@Inject
-	PluginViewModel(PluginManager pluginManager, EventBus eventBus) {
-		this.pluginManager = pluginManager;
-		this.eventBus = eventBus;
-		eventBus.addListener(this);
-		torPluginState.setValue(getTransportState(TorConstants.ID));
-		wifiPluginState.setValue(getTransportState(LanTcpConstants.ID));
-		btPluginState.setValue(getTransportState(BluetoothConstants.ID));
-	}
-
-	@Override
-	protected void onCleared() {
-		eventBus.removeListener(this);
-	}
-
-	@Override
-	public void eventOccurred(Event e) {
-		if (e instanceof TransportStateEvent) {
-			TransportStateEvent t = (TransportStateEvent) e;
-			TransportId id = t.getTransportId();
-			State state = t.getState();
-			if (LOG.isLoggable(INFO)) {
-				LOG.info("TransportStateEvent: " + id + " is " + state);
-			}
-			MutableLiveData<State> liveData = getPluginLiveData(id);
-			if (liveData != null) liveData.postValue(state);
-		}
-	}
-
-	LiveData<State> getPluginState(TransportId id) {
-		LiveData<State> liveData = getPluginLiveData(id);
-		if (liveData == null) throw new IllegalArgumentException();
-		return liveData;
-	}
-
-	private State getTransportState(TransportId id) {
-		Plugin plugin = pluginManager.getPlugin(id);
-		return plugin == null ? STARTING_STOPPING : plugin.getState();
-	}
-
-	@Nullable
-	private MutableLiveData<State> getPluginLiveData(TransportId id) {
-		if (id.equals(TorConstants.ID)) return torPluginState;
-		else if (id.equals(LanTcpConstants.ID)) return wifiPluginState;
-		else if (id.equals(BluetoothConstants.ID)) return btPluginState;
-		else return null;
-	}
-}

briar-android/src/main/java/org/briarproject/briar/android/navdrawer/TransportStateListener.java

@@ -0,0 +1,11 @@
+package org.briarproject.briar.android.navdrawer;
+
+import org.briarproject.bramble.api.plugin.TransportId;
+
+import androidx.annotation.UiThread;
+
+interface TransportStateListener {
+
+	@UiThread
+	void stateUpdate(TransportId id, boolean enabled);
+}

briar-android/src/main/java/org/briarproject/briar/android/reporting/BriarReportPrimer.java

@@ -21,8 +21,6 @@ import org.briarproject.briar.android.logging.BriefLogFormatter;
 import java.io.File;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
-import java.net.InetAddress;
-import java.net.UnknownHostException;
 import java.util.LinkedHashMap;
 import java.util.Map;
 import java.util.concurrent.Callable;
@@ -187,18 +185,12 @@ public class BriarReportPrimer implements ReportPrimer {
 				WifiInfo wifiInfo = wm.getConnectionInfo();
 				if (wifiInfo != null) {
 					int ip = wifiInfo.getIpAddress(); // Nice API, Google
-					byte[] ipBytes = new byte[4];
-					ipBytes[0] = (byte) (ip & 0xFF);
-					ipBytes[1] = (byte) ((ip >> 8) & 0xFF);
-					ipBytes[2] = (byte) ((ip >> 16) & 0xFF);
-					ipBytes[3] = (byte) ((ip >> 24) & 0xFF);
-					try {
-						InetAddress address = InetAddress.getByAddress(ipBytes);
-						customData.put("Wi-Fi address",
-								scrubInetAddress(address));
-					} catch (UnknownHostException ignored) {
-						// Should only be thrown if address has illegal length
-					}
+					int ip1 = ip & 0xFF;
+					int ip2 = (ip >> 8) & 0xFF;
+					int ip3 = (ip >> 16) & 0xFF;
+					int ip4 = (ip >> 24) & 0xFF;
+					String address = ip1 + "." + ip2 + "." + ip3 + "." + ip4;
+					customData.put("Wi-Fi address", scrubInetAddress(address));
 				}
 			}
 

briar-android/src/main/java/org/briarproject/briar/android/settings/SettingsFragment.java

@@ -21,7 +21,6 @@ import org.briarproject.bramble.api.event.EventListener;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.bramble.api.plugin.BluetoothConstants;
-import org.briarproject.bramble.api.plugin.LanTcpConstants;
 import org.briarproject.bramble.api.plugin.TorConstants;
 import org.briarproject.bramble.api.settings.Settings;
 import org.briarproject.bramble.api.settings.SettingsManager;
@@ -42,7 +41,6 @@ import java.util.logging.Logger;
 
 import javax.inject.Inject;
 
-import androidx.annotation.Nullable;
 import androidx.annotation.StringRes;
 import androidx.core.content.ContextCompat;
 import androidx.core.text.TextUtilsCompat;
@@ -74,14 +72,10 @@ import static android.widget.Toast.LENGTH_SHORT;
 import static androidx.core.view.ViewCompat.LAYOUT_DIRECTION_LTR;
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
-import static org.briarproject.bramble.api.plugin.Plugin.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.BluetoothConstants.PREF_BT_ENABLE;
 import static org.briarproject.bramble.api.plugin.TorConstants.PREF_TOR_MOBILE;
 import static org.briarproject.bramble.api.plugin.TorConstants.PREF_TOR_NETWORK;
 import static org.briarproject.bramble.api.plugin.TorConstants.PREF_TOR_NETWORK_AUTOMATIC;
-import static org.briarproject.bramble.api.plugin.TorConstants.PREF_TOR_NETWORK_NEVER;
 import static org.briarproject.bramble.api.plugin.TorConstants.PREF_TOR_ONLY_WHEN_CHARGING;
 import static org.briarproject.bramble.util.LogUtils.logDuration;
 import static org.briarproject.bramble.util.LogUtils.logException;
@@ -90,7 +84,6 @@ import static org.briarproject.briar.android.BriarApplication.ENTRY_ACTIVITY;
 import static org.briarproject.briar.android.TestingConstants.IS_DEBUG_BUILD;
 import static org.briarproject.briar.android.activity.RequestCodes.REQUEST_RINGTONE;
 import static org.briarproject.briar.android.navdrawer.NavDrawerActivity.SIGN_OUT_URI;
-import static org.briarproject.briar.android.util.UiUtils.getCountryDisplayName;
 import static org.briarproject.briar.android.util.UiUtils.hasScreenLock;
 import static org.briarproject.briar.android.util.UiUtils.triggerFeedback;
 import static org.briarproject.briar.api.android.AndroidNotificationManager.BLOG_CHANNEL_ID;
@@ -112,24 +105,16 @@ public class SettingsFragment extends PreferenceFragmentCompat
 		implements EventListener, OnPreferenceChangeListener {
 
 	public static final String SETTINGS_NAMESPACE = "android-ui";
+	public static final String BT_NAMESPACE = BluetoothConstants.ID.getString();
+	public static final String TOR_NAMESPACE = TorConstants.ID.getString();
 	public static final String LANGUAGE = "pref_key_language";
 	public static final String PREF_SCREEN_LOCK = "pref_key_lock";
 	public static final String PREF_SCREEN_LOCK_TIMEOUT =
 			"pref_key_lock_timeout";
 	public static final String NOTIFY_SIGN_IN = "pref_key_notify_sign_in";
-
-	private static final String BT_NAMESPACE =
-			BluetoothConstants.ID.getString();
-	private static final String BT_ENABLE = "pref_key_bluetooth";
-
-	private static final String WIFI_NAMESPACE = LanTcpConstants.ID.getString();
-	private static final String WIFI_ENABLE = "pref_key_wifi";
-
-	private static final String TOR_NAMESPACE = TorConstants.ID.getString();
-	private static final String TOR_ENABLE = "pref_key_tor_enable";
-	private static final String TOR_NETWORK = "pref_key_tor_network";
-	private static final String TOR_MOBILE = "pref_key_tor_mobile_data";
-	private static final String TOR_ONLY_WHEN_CHARGING =
+	public static final String TOR_NETWORK = "pref_key_tor_network";
+	public static final String TOR_MOBILE = "pref_key_tor_mobile_data";
+	public static final String TOR_ONLY_WHEN_CHARGING =
 			"pref_key_tor_only_when_charging";
 
 	private static final Logger LOG =
@@ -137,9 +122,7 @@ public class SettingsFragment extends PreferenceFragmentCompat
 
 	private SettingsActivity listener;
 	private ListPreference language;
-	private SwitchPreference enableBluetooth;
-	private SwitchPreference enableWifi;
-	private SwitchPreference enableTor;
+	private ListPreference enableBluetooth;
 	private ListPreference torNetwork;
 	private SwitchPreference torMobile;
 	private SwitchPreference torOnlyWhenCharging;
@@ -154,7 +137,7 @@ public class SettingsFragment extends PreferenceFragmentCompat
 	private Preference notifySound;
 
 	// Fields that are accessed from background threads must be volatile
-	private volatile Settings settings, btSettings, wifiSettings, torSettings;
+	private volatile Settings settings, btSettings, torSettings;
 	private volatile boolean settingsLoaded = false;
 
 	@Inject
@@ -180,23 +163,28 @@ public class SettingsFragment extends PreferenceFragmentCompat
 	public void onCreatePreferences(Bundle bundle, String s) {
 		addPreferencesFromResource(R.xml.settings);
 
-		language = findPreference(LANGUAGE);
+		language = (ListPreference) findPreference(LANGUAGE);
 		setLanguageEntries();
-		ListPreference theme = findPreference("pref_key_theme");
-		enableBluetooth = findPreference(BT_ENABLE);
-		enableWifi = findPreference(WIFI_ENABLE);
-		enableTor = findPreference(TOR_ENABLE);
-		torNetwork = findPreference(TOR_NETWORK);
-		torMobile = findPreference(TOR_MOBILE);
-		torOnlyWhenCharging = findPreference(TOR_ONLY_WHEN_CHARGING);
-		screenLock = findPreference(PREF_SCREEN_LOCK);
-		screenLockTimeout = findPreference(PREF_SCREEN_LOCK_TIMEOUT);
-		notifyPrivateMessages =
-				findPreference("pref_key_notify_private_messages");
-		notifyGroupMessages = findPreference("pref_key_notify_group_messages");
-		notifyForumPosts = findPreference("pref_key_notify_forum_posts");
-		notifyBlogPosts = findPreference("pref_key_notify_blog_posts");
-		notifyVibration = findPreference("pref_key_notify_vibration");
+		ListPreference theme =
+				(ListPreference) findPreference("pref_key_theme");
+		enableBluetooth = (ListPreference) findPreference("pref_key_bluetooth");
+		torNetwork = (ListPreference) findPreference(TOR_NETWORK);
+		torMobile = (SwitchPreference) findPreference(TOR_MOBILE);
+		torOnlyWhenCharging =
+				(SwitchPreference) findPreference(TOR_ONLY_WHEN_CHARGING);
+		screenLock = (SwitchPreference) findPreference(PREF_SCREEN_LOCK);
+		screenLockTimeout =
+				(ListPreference) findPreference(PREF_SCREEN_LOCK_TIMEOUT);
+		notifyPrivateMessages = (SwitchPreference) findPreference(
+				"pref_key_notify_private_messages");
+		notifyGroupMessages = (SwitchPreference) findPreference(
+				"pref_key_notify_group_messages");
+		notifyForumPosts = (SwitchPreference) findPreference(
+				"pref_key_notify_forum_posts");
+		notifyBlogPosts = (SwitchPreference) findPreference(
+				"pref_key_notify_blog_posts");
+		notifyVibration = (SwitchPreference) findPreference(
+				"pref_key_notify_vibration");
 		notifySound = findPreference("pref_key_notify_sound");
 
 		language.setOnPreferenceChangeListener(this);
@@ -206,7 +194,8 @@ public class SettingsFragment extends PreferenceFragmentCompat
 				UiUtils.setTheme(getActivity(), (String) newValue);
 				// bring up parent activity, so it can change its theme as well
 				// upstream bug: https://issuetracker.google.com/issues/38352704
-				Intent intent = new Intent(getActivity(), ENTRY_ACTIVITY);
+				Intent intent =
+						new Intent(getActivity(), ENTRY_ACTIVITY);
 				intent.setFlags(
 						FLAG_ACTIVITY_CLEAR_TASK | FLAG_ACTIVITY_NEW_TASK);
 				startActivity(intent);
@@ -218,8 +207,6 @@ public class SettingsFragment extends PreferenceFragmentCompat
 			return true;
 		});
 		enableBluetooth.setOnPreferenceChangeListener(this);
-		enableWifi.setOnPreferenceChangeListener(this);
-		enableTor.setOnPreferenceChangeListener(this);
 		torNetwork.setOnPreferenceChangeListener(this);
 		torMobile.setOnPreferenceChangeListener(this);
 		torOnlyWhenCharging.setOnPreferenceChangeListener(this);
@@ -262,9 +249,8 @@ public class SettingsFragment extends PreferenceFragmentCompat
 	}
 
 	@Override
-	public View onCreateView(LayoutInflater inflater,
-			@Nullable ViewGroup container,
-			@Nullable Bundle savedInstanceState) {
+	public View onCreateView(LayoutInflater inflater, ViewGroup container,
+			Bundle savedInstanceState) {
 		View view = super.onCreateView(inflater, container, savedInstanceState);
 		ColorDrawable divider = new ColorDrawable(
 				ContextCompat.getColor(requireContext(), R.color.divider));
@@ -339,13 +325,17 @@ public class SettingsFragment extends PreferenceFragmentCompat
 
 		// Look up country name in the user's chosen language if available
 		String country = locationUtils.getCurrentCountry();
-		String countryName = getCountryDisplayName(country);
-
+		String countryName = country;
+		for (Locale locale : Locale.getAvailableLocales()) {
+			if (locale.getCountry().equalsIgnoreCase(country)) {
+				countryName = locale.getDisplayCountry();
+				break;
+			}
+		}
 		boolean blocked =
 				circumventionProvider.isTorProbablyBlocked(country);
 		boolean useBridges = circumventionProvider.doBridgesWork(country);
-		String setting =
-				getString(R.string.tor_network_setting_without_bridges);
+		String setting = getString(R.string.tor_network_setting_without_bridges);
 		if (blocked && useBridges) {
 			setting = getString(R.string.tor_network_setting_with_bridges);
 		} else if (blocked) {
@@ -362,7 +352,6 @@ public class SettingsFragment extends PreferenceFragmentCompat
 				long start = now();
 				settings = settingsManager.getSettings(SETTINGS_NAMESPACE);
 				btSettings = settingsManager.getSettings(BT_NAMESPACE);
-				wifiSettings = settingsManager.getSettings(WIFI_NAMESPACE);
 				torSettings = settingsManager.getSettings(TOR_NAMESPACE);
 				settingsLoaded = true;
 				logDuration(LOG, "Loading settings", start);
@@ -373,50 +362,26 @@ public class SettingsFragment extends PreferenceFragmentCompat
 		});
 	}
 
-	// TODO: Remove after a reasonable migration period (added 2020-06-25)
-	private Settings migrateTorSettings(Settings s) {
-		int network = s.getInt(PREF_TOR_NETWORK, DEFAULT_PREF_TOR_NETWORK);
-		if (network == PREF_TOR_NETWORK_NEVER) {
-			s.putInt(PREF_TOR_NETWORK, DEFAULT_PREF_TOR_NETWORK);
-			s.putBoolean(PREF_PLUGIN_ENABLE, false);
-			// We don't need to save the migrated settings - the Tor plugin is
-			// responsible for that. This code just handles the case where the
-			// settings are loaded before the plugin migrates them.
-		}
-		return s;
-	}
-
 	private void displaySettings() {
 		listener.runOnUiThreadUnlessDestroyed(() -> {
 			// due to events, we might try to display before a load completed
 			if (!settingsLoaded) return;
 
-			boolean btEnabledSetting = btSettings.getBoolean(PREF_PLUGIN_ENABLE,
-					BluetoothConstants.DEFAULT_PREF_PLUGIN_ENABLE);
-			enableBluetooth.setChecked(btEnabledSetting);
-
-			boolean wifiEnabledSetting =
-					wifiSettings.getBoolean(PREF_PLUGIN_ENABLE,
-							LanTcpConstants.DEFAULT_PREF_PLUGIN_ENABLE);
-			enableWifi.setChecked(wifiEnabledSetting);
-
-			boolean torEnabledSetting =
-					torSettings.getBoolean(PREF_PLUGIN_ENABLE,
-							TorConstants.DEFAULT_PREF_PLUGIN_ENABLE);
-			enableTor.setChecked(torEnabledSetting);
+			boolean btEnabledSetting =
+					btSettings.getBoolean(PREF_BT_ENABLE, false);
+			enableBluetooth.setValue(Boolean.toString(btEnabledSetting));
 
 			int torNetworkSetting = torSettings.getInt(PREF_TOR_NETWORK,
-					DEFAULT_PREF_TOR_NETWORK);
+					PREF_TOR_NETWORK_AUTOMATIC);
 			torNetwork.setValue(Integer.toString(torNetworkSetting));
 			setTorNetworkSummary(torNetworkSetting);
 
-			boolean torMobileSetting = torSettings.getBoolean(PREF_TOR_MOBILE,
-					DEFAULT_PREF_TOR_MOBILE);
+			boolean torMobileSetting =
+					torSettings.getBoolean(PREF_TOR_MOBILE, true);
 			torMobile.setChecked(torMobileSetting);
 
 			boolean torChargingSetting =
-					torSettings.getBoolean(PREF_TOR_ONLY_WHEN_CHARGING,
-							DEFAULT_PREF_TOR_ONLY_WHEN_CHARGING);
+					torSettings.getBoolean(PREF_TOR_ONLY_WHEN_CHARGING, false);
 			torOnlyWhenCharging.setChecked(torChargingSetting);
 
 			displayScreenLockSetting();
@@ -478,8 +443,6 @@ public class SettingsFragment extends PreferenceFragmentCompat
 		// - pref_key_lock (screenLock -> displayScreenLockSetting())
 		// - pref_key_lock_timeout (screenLockTimeout)
 		enableBluetooth.setEnabled(enabled);
-		enableWifi.setEnabled(enabled);
-		enableTor.setEnabled(enabled);
 		torNetwork.setEnabled(enabled);
 		torMobile.setEnabled(enabled);
 		torOnlyWhenCharging.setEnabled(enabled);
@@ -582,14 +545,8 @@ public class SettingsFragment extends PreferenceFragmentCompat
 				languageChanged((String) newValue);
 			return false;
 		} else if (preference == enableBluetooth) {
-			boolean btSetting = (Boolean) newValue;
-			storeBluetoothSetting(btSetting);
-		} else if (preference == enableWifi) {
-			boolean wifiSetting = (Boolean) newValue;
-			storeWifiSetting(wifiSetting);
-		} else if (preference == enableTor) {
-			boolean torEnabledSetting = (Boolean) newValue;
-			storeTorEnabledSetting(torEnabledSetting);
+			boolean btSetting = Boolean.valueOf((String) newValue);
+			storeBluetoothSettings(btSetting);
 		} else if (preference == torNetwork) {
 			int torNetworkSetting = Integer.valueOf((String) newValue);
 			storeTorNetworkSetting(torNetworkSetting);
@@ -653,12 +610,6 @@ public class SettingsFragment extends PreferenceFragmentCompat
 		builder.show();
 	}
 
-	private void storeTorEnabledSetting(boolean torEnabledSetting) {
-		Settings s = new Settings();
-		s.putBoolean(PREF_PLUGIN_ENABLE, torEnabledSetting);
-		mergeSettings(s, TOR_NAMESPACE);
-	}
-
 	private void storeTorNetworkSetting(int torNetworkSetting) {
 		Settings s = new Settings();
 		s.putInt(PREF_TOR_NETWORK, torNetworkSetting);
@@ -677,18 +628,12 @@ public class SettingsFragment extends PreferenceFragmentCompat
 		mergeSettings(s, TOR_NAMESPACE);
 	}
 
-	private void storeBluetoothSetting(boolean btSetting) {
+	private void storeBluetoothSettings(boolean btSetting) {
 		Settings s = new Settings();
-		s.putBoolean(PREF_PLUGIN_ENABLE, btSetting);
+		s.putBoolean(PREF_BT_ENABLE, btSetting);
 		mergeSettings(s, BT_NAMESPACE);
 	}
 
-	private void storeWifiSetting(boolean wifiSetting) {
-		Settings s = new Settings();
-		s.putBoolean(PREF_PLUGIN_ENABLE, wifiSetting);
-		mergeSettings(s, WIFI_NAMESPACE);
-	}
-
 	private void storeSettings(Settings s) {
 		mergeSettings(s, SETTINGS_NAMESPACE);
 	}
@@ -751,13 +696,9 @@ public class SettingsFragment extends PreferenceFragmentCompat
 				LOG.info("Bluetooth settings updated");
 				btSettings = s.getSettings();
 				displaySettings();
-			} else if (namespace.equals(WIFI_NAMESPACE)) {
-				LOG.info("Wifi settings updated");
-				wifiSettings = s.getSettings();
-				displaySettings();
 			} else if (namespace.equals(TOR_NAMESPACE)) {
 				LOG.info("Tor settings updated");
-				torSettings = migrateTorSettings(s.getSettings());
+				torSettings = s.getSettings();
 				displaySettings();
 			}
 		}

briar-android/src/main/java/org/briarproject/briar/android/util/BriarNotificationBuilder.java

@@ -20,7 +20,7 @@ public class BriarNotificationBuilder extends NotificationCompat.Builder {
 		// https://issuetracker.google.com/issues/36961721
 		setAutoCancel(true);
 
-		setLights(ContextCompat.getColor(context, R.color.briar_lime_400),
+		setLights(ContextCompat.getColor(context, R.color.briar_green_light),
 				750, 500);
 		if (SDK_INT >= 21) setVisibility(VISIBILITY_PRIVATE);
 	}

briar-android/src/main/java/org/briarproject/briar/android/util/UiUtils.java

@@ -6,7 +6,6 @@ import android.app.KeyguardManager;
 import android.content.Context;
 import android.content.DialogInterface.OnClickListener;
 import android.content.Intent;
-import android.graphics.drawable.Drawable;
 import android.net.Uri;
 import android.os.PowerManager;
 import android.text.Html;
@@ -39,12 +38,9 @@ import org.briarproject.briar.R;
 import org.briarproject.briar.android.view.ArticleMovementMethod;
 import org.briarproject.briar.android.widget.LinkDialogFragment;
 
-import java.util.Locale;
-
 import androidx.annotation.AttrRes;
 import androidx.annotation.ColorInt;
 import androidx.annotation.ColorRes;
-import androidx.annotation.DrawableRes;
 import androidx.annotation.Nullable;
 import androidx.annotation.RequiresApi;
 import androidx.annotation.UiThread;
@@ -83,10 +79,7 @@ import static androidx.appcompat.app.AppCompatDelegate.MODE_NIGHT_FOLLOW_SYSTEM;
 import static androidx.appcompat.app.AppCompatDelegate.MODE_NIGHT_NO;
 import static androidx.appcompat.app.AppCompatDelegate.MODE_NIGHT_YES;
 import static androidx.appcompat.app.AppCompatDelegate.setDefaultNightMode;
-import static androidx.core.content.ContextCompat.getColor;
-import static androidx.core.content.ContextCompat.getDrawable;
 import static androidx.core.content.ContextCompat.getSystemService;
-import static androidx.core.graphics.drawable.DrawableCompat.setTint;
 import static androidx.core.view.ViewCompat.LAYOUT_DIRECTION_RTL;
 import static java.util.Objects.requireNonNull;
 import static java.util.concurrent.TimeUnit.DAYS;
@@ -408,20 +401,4 @@ public class UiUtils {
 		return ctx.getResources().getConfiguration().getLayoutDirection() ==
 				LAYOUT_DIRECTION_RTL;
 	}
-
-	public static String getCountryDisplayName(String isoCode) {
-		for (Locale locale : Locale.getAvailableLocales()) {
-			if (locale.getCountry().equalsIgnoreCase(isoCode)) {
-				return locale.getDisplayCountry();
-			}
-		}
-		// Name is unknown
-		return isoCode;
-	}
-
-	public static Drawable getDialogIcon(Context ctx, @DrawableRes int resId) {
-		Drawable icon = getDrawable(ctx, resId);
-		setTint(requireNonNull(icon), getColor(ctx, R.color.color_primary));
-		return icon;
-	}
 }

briar-android/src/main/res/drawable-night/contact_connected.xml

@@ -11,7 +11,7 @@
 C7.58,20,4,16.42,4,12 S7.58,4,12,4 S20,7.58,20,12 S16.42,20,12,20 Z"/>
 
 	<path
-		android:fillColor="#82c91e"
+		android:fillColor="#95d220"
 		android:pathData="M10.8972,19.9503 C6.5514,19.3493,3.43091,15.2154,4.0625,10.896
 C4.55452,7.53099,7.09451,4.8236,10.394,4.14714
 C14.2569,3.35517,18.1698,5.54347,19.5236,9.25295

briar-android/src/main/res/drawable-night/qr_code_explanation.xml

@@ -17,12 +17,12 @@
 		android:fillColor="#ffffff"
 		android:pathData="M175.3 16.5l-9.8 0 0 -5.7c0 -1.4 -1.2 -2.6 -2.6 -2.6l-19.3 0c-1.4 0 -2.6 1.2 -2.6 2.6l0 14.4c0 1.4 1.2 2.6 2.6 2.6l15.1 0 0 17.3c0 2.4 2 4.4 4.4 4.4l12.2 0c2.4 0 4.4 -2 4.4 -4.4l0 -24.2c0.1 -2.4 -1.9 -4.4 -4.4 -4.4zm-12.4 -5.9l-9.6 6 -9.6 -6 19.2 0zm-19.4 14.8l0 -12.3 9.8 6.1 9.8 -6.1 0 12.3 -19.6 0zm28.6 21.2l-5.8 0 0 -1.5 5.8 0 0 1.5zm5 -4.6l-15.8 0 0 -14.2 1.6 0c1.4 0 2.6 -1.2 2.6 -2.6l0 -4.1 11.6 0 0 20.9z"/>
 	<path
-		android:fillColor="#db3b21"
+		android:fillColor="#ff0000"
 		android:pathData="M101.4 17.8l2 2 7.4 -7.3 7.3 7.3 2.1 -2 -7.4 -7.4 7.4 -7.3 -2.1 -2.1 -7.3 7.4 -7.4 -7.4 -2 2.1 7.3 7.3z"/>
 	<path
-		android:fillColor="#db3b21"
+		android:fillColor="#ff0000"
 		android:pathData="M176 17.8l2.1 2 7.3 -7.3 7.4 7.3 2 -2 -7.3 -7.4 7.3 -7.3 -2 -2.1 -7.4 7.4 -7.3 -7.4 -2.1 2.1 7.3 7.3z"/>
 	<path
-		android:fillColor="#67a60f"
+		android:fillColor="#08b124"
 		android:pathData="M35.8 18.8l0 0L52.5 2.1 50.5 0 35.6 14.8 28.5 7.7l-2.1 2.1 9.2 9.1z"/>
 </vector>

briar-android/src/main/res/drawable/bubble_completed.xml

@@ -7,7 +7,7 @@
 		android:radius="32dp"/>
 
 	<solid
-		android:color="@color/briar_lime_600"/>
+		android:color="@color/briar_green"/>
 
 </shape>
 

briar-android/src/main/res/drawable/contact_connected.xml

@@ -13,7 +13,7 @@ C7.58,20,4,16.42,4,12 S7.58,4,12,4 S20,7.58,20,12 S16.42,20,12,20 Z"/>
 	<path
 		android:pathData="M0,0 L24,0 L24,24 L0,24 Z"/>
 	<path
-		android:fillColor="#82c91e"
+		android:fillColor="#95d220"
 		android:pathData="M10.8972,19.9503 C6.5514,19.3493,3.43091,15.2154,4.0625,10.896
 C4.55452,7.53099,7.09451,4.8236,10.394,4.14714
 C14.2569,3.35517,18.1698,5.54347,19.5236,9.25295

briar-android/src/main/res/drawable/contact_offline.xml

@@ -6,7 +6,7 @@
         android:viewportWidth="24">
 
 	<path
-		android:fillColor="#2e3d4f"
+		android:fillColor="#2D3E50"
 		android:pathData="M10.8972,19.9503 C6.5514,19.3493,3.43091,15.2154,4.0625,10.896
 C4.55452,7.53099,7.09451,4.8236,10.394,4.14714
 C14.2569,3.35517,18.1698,5.54347,19.5236,9.25295

briar-android/src/main/res/drawable/contact_online.xml

@@ -6,7 +6,7 @@
         android:viewportWidth="24">
 
 	<path
-		android:fillColor="#82c91e"
+		android:fillColor="#95D220"
 		android:pathData="M10.8972,19.9503 C6.5514,19.3493,3.43091,15.2154,4.0625,10.896
 C4.55452,7.53099,7.09451,4.8236,10.394,4.14714
 C14.2569,3.35517,18.1698,5.54347,19.5236,9.25295