Migrate away from hardware-backed keys until keymaster issues are fixed.

Fix cancellation of periodic tasks, remove ticker

Closes #1759

See merge request briar/briar!1274

.idea/codeStyles/Project.xml

@@ -1,8 +1,5 @@
 <component name="ProjectCodeStyleConfiguration">
   <code_scheme name="Project" version="173">
-    <AndroidXmlCodeStyleSettings>
-      <option name="ARRANGEMENT_SETTINGS_MIGRATED_TO_191" value="true" />
-    </AndroidXmlCodeStyleSettings>
     <JavaCodeStyleSettings>
       <option name="ANNOTATION_PARAMETER_WRAP" value="1" />
       <option name="IMPORT_LAYOUT_TABLE">

TRANSLATION.md

@@ -0,0 +1,9 @@
+Translations for this project are managed through Transifex:
+
+https://transifex.com/otf/briar
+
+If you'd like to volunteer as a translator, please create a Transifex account and request to be
+added to the project's translation team. The Localization Lab has some instructions and advice for
+translators here:
+
+https://wiki.localizationlab.org/index.php/Briar

bramble-android/build.gradle

@@ -11,8 +11,8 @@ android {
 	defaultConfig {
 		minSdkVersion 16
 		targetSdkVersion 28
-		versionCode 10207
-		versionName "1.2.7"
+		versionCode 10209
+		versionName "1.2.9"
 		consumerProguardFiles 'proguard-rules.txt'
 
 		testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"

bramble-android/src/main/AndroidManifest.xml

@@ -16,6 +16,8 @@
 		android:label="@string/app_name"
 		android:supportsRtl="true">
 
+		<receiver android:name=".system.AlarmReceiver" />
+
 	</application>
 
 </manifest>

bramble-android/src/main/java/org/briarproject/bramble/BrambleAndroidModule.java

@@ -6,6 +6,8 @@ import org.briarproject.bramble.plugin.tor.CircumventionModule;
 import org.briarproject.bramble.reporting.ReportingModule;
 import org.briarproject.bramble.socks.SocksModule;
 import org.briarproject.bramble.system.AndroidSystemModule;
+import org.briarproject.bramble.system.AndroidTaskSchedulerModule;
+import org.briarproject.bramble.system.AndroidWakefulIoExecutorModule;
 
 import dagger.Module;
 
@@ -13,6 +15,8 @@ import dagger.Module;
 		AndroidBatteryModule.class,
 		AndroidNetworkModule.class,
 		AndroidSystemModule.class,
+		AndroidTaskSchedulerModule.class,
+		AndroidWakefulIoExecutorModule.class,
 		CircumventionModule.class,
 		ReportingModule.class,
 		SocksModule.class

bramble-android/src/main/java/org/briarproject/bramble/BrambleAppComponent.java

@@ -0,0 +1,8 @@
+package org.briarproject.bramble;
+
+import org.briarproject.bramble.api.system.AlarmListener;
+
+public interface BrambleAppComponent {
+
+	AlarmListener alarmListener();
+}

bramble-android/src/main/java/org/briarproject/bramble/BrambleApplication.java

@@ -0,0 +1,6 @@
+package org.briarproject.bramble;
+
+public interface BrambleApplication {
+
+	BrambleAppComponent getBrambleAppComponent();
+}

bramble-android/src/main/java/org/briarproject/bramble/api/system/AlarmListener.java

@@ -0,0 +1,11 @@
+package org.briarproject.bramble.api.system;
+
+import android.content.Intent;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+@NotNullByDefault
+public interface AlarmListener {
+
+	void onAlarm(Intent intent);
+}

bramble-android/src/main/java/org/briarproject/bramble/api/system/AndroidWakeLock.java

@@ -0,0 +1,19 @@
+package org.briarproject.bramble.api.system;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+@NotNullByDefault
+public interface AndroidWakeLock {
+
+	/**
+	 * Acquires the wake lock. This has no effect if the wake lock has already
+	 * been acquired.
+	 */
+	void acquire();
+
+	/**
+	 * Releases the wake lock. This has no effect if the wake lock has already
+	 * been released.
+	 */
+	void release();
+}

bramble-android/src/main/java/org/briarproject/bramble/api/system/AndroidWakeLockManager.java

@@ -0,0 +1,38 @@
+package org.briarproject.bramble.api.system;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+import java.util.concurrent.Executor;
+
+@NotNullByDefault
+public interface AndroidWakeLockManager {
+
+	/**
+	 * Creates a wake lock with the given tag. The tag is only used for
+	 * logging; the underlying OS wake lock will use its own tag.
+	 */
+	AndroidWakeLock createWakeLock(String tag);
+
+	/**
+	 * Runs the given task while holding a wake lock.
+	 */
+	void runWakefully(Runnable r, String tag);
+
+	/**
+	 * Submits the given task to the given executor while holding a wake lock.
+	 * The lock is released when the task completes, or if an exception is
+	 * thrown while submitting or running the task.
+	 */
+	void executeWakefully(Runnable r, Executor executor, String tag);
+
+	/**
+	 * Starts a dedicated thread to run the given task asynchronously. A wake
+	 * lock is acquired before starting the thread and released when the task
+	 * completes, or if an exception is thrown while starting the thread or
+	 * running the task.
+	 * <p>
+	 * This method should only be used for lifecycle management tasks that
+	 * can't be run on an executor.
+	 */
+	void executeWakefully(Runnable r, String tag);
+}

bramble-android/src/main/java/org/briarproject/bramble/network/AndroidNetworkManager.java

@@ -9,16 +9,17 @@ import android.net.ConnectivityManager;
 import android.net.NetworkInfo;
 
 import org.briarproject.bramble.api.event.EventBus;
+import org.briarproject.bramble.api.event.EventExecutor;
 import org.briarproject.bramble.api.lifecycle.Service;
 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.ParametersNotNullByDefault;
-import org.briarproject.bramble.api.system.Scheduler;
+import org.briarproject.bramble.api.system.TaskScheduler;
+import org.briarproject.bramble.api.system.TaskScheduler.Cancellable;
 
-import java.util.concurrent.Future;
-import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.Executor;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicReference;
@@ -50,20 +51,22 @@ class AndroidNetworkManager implements NetworkManager, Service {
 	private static final String WIFI_AP_STATE_CHANGED_ACTION =
 			"android.net.wifi.WIFI_AP_STATE_CHANGED";
 
-	private final ScheduledExecutorService scheduler;
+	private final TaskScheduler scheduler;
 	private final EventBus eventBus;
+	private final Executor eventExecutor;
 	private final Context appContext;
-	private final AtomicReference<Future<?>> connectivityCheck =
+	private final AtomicReference<Cancellable> connectivityCheck =
 			new AtomicReference<>();
 	private final AtomicBoolean used = new AtomicBoolean(false);
 
 	private volatile BroadcastReceiver networkStateReceiver = null;
 
 	@Inject
-	AndroidNetworkManager(@Scheduler ScheduledExecutorService scheduler,
-			EventBus eventBus, Application app) {
+	AndroidNetworkManager(TaskScheduler scheduler, EventBus eventBus,
+			@EventExecutor Executor eventExecutor, Application app) {
 		this.scheduler = scheduler;
 		this.eventBus = eventBus;
+		this.eventExecutor = eventExecutor;
 		this.appContext = app.getApplicationContext();
 	}
 
@@ -104,11 +107,12 @@ class AndroidNetworkManager implements NetworkManager, Service {
 	}
 
 	private void scheduleConnectionStatusUpdate(int delay, TimeUnit unit) {
-		Future<?> newConnectivityCheck =
-				scheduler.schedule(this::updateConnectionStatus, delay, unit);
-		Future<?> oldConnectivityCheck =
+		Cancellable newConnectivityCheck =
+				scheduler.schedule(this::updateConnectionStatus, eventExecutor,
+						delay, unit);
+		Cancellable oldConnectivityCheck =
 				connectivityCheck.getAndSet(newConnectivityCheck);
-		if (oldConnectivityCheck != null) oldConnectivityCheck.cancel(false);
+		if (oldConnectivityCheck != null) oldConnectivityCheck.cancel();
 	}
 
 	private class NetworkStateReceiver extends BroadcastReceiver {

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

@@ -0,0 +1,36 @@
+package org.briarproject.bramble.plugin.bluetooth;
+
+import android.bluetooth.BluetoothSocket;
+
+import org.briarproject.bramble.api.io.TimeoutMonitor;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
+import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
+import org.briarproject.bramble.api.system.AndroidWakeLockManager;
+
+import java.io.IOException;
+
+@NotNullByDefault
+class AndroidBluetoothConnectionFactory
+		implements BluetoothConnectionFactory<BluetoothSocket> {
+
+	private final BluetoothConnectionLimiter connectionLimiter;
+	private final AndroidWakeLockManager wakeLockManager;
+	private final TimeoutMonitor timeoutMonitor;
+
+	AndroidBluetoothConnectionFactory(
+			BluetoothConnectionLimiter connectionLimiter,
+			AndroidWakeLockManager wakeLockManager,
+			TimeoutMonitor timeoutMonitor) {
+		this.connectionLimiter = connectionLimiter;
+		this.wakeLockManager = wakeLockManager;
+		this.timeoutMonitor = timeoutMonitor;
+	}
+
+	@Override
+	public DuplexTransportConnection wrapSocket(DuplexPlugin plugin,
+			BluetoothSocket s) throws IOException {
+		return new AndroidBluetoothTransportConnection(plugin,
+				connectionLimiter, wakeLockManager, timeoutMonitor, s);
+	}
+}

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

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.plugin.bluetooth;
 
+import android.app.Application;
 import android.bluetooth.BluetoothAdapter;
 import android.bluetooth.BluetoothDevice;
 import android.bluetooth.BluetoothServerSocket;
@@ -9,9 +10,9 @@ import android.content.Context;
 import android.content.Intent;
 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;
@@ -59,16 +59,16 @@ import static org.briarproject.bramble.util.PrivacyUtils.scrubMacAddress;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
-class AndroidBluetoothPlugin extends BluetoothPlugin<BluetoothServerSocket> {
+class AndroidBluetoothPlugin
+		extends BluetoothPlugin<BluetoothSocket, BluetoothServerSocket> {
 
 	private static final Logger LOG =
 			getLogger(AndroidBluetoothPlugin.class.getName());
 
 	private static final int MAX_DISCOVERY_MS = 10_000;
 
-	private final ScheduledExecutorService scheduler;
 	private final AndroidExecutor androidExecutor;
-	private final Context appContext;
+	private final Application app;
 	private final Clock clock;
 
 	private volatile boolean wasEnabledByUs = false;
@@ -78,16 +78,22 @@ class AndroidBluetoothPlugin extends BluetoothPlugin<BluetoothServerSocket> {
 	private volatile BluetoothAdapter adapter = null;
 
 	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) {
-		super(connectionLimiter, timeoutMonitor, ioExecutor, secureRandom,
-				callback, maxLatency, maxIdleTime, pollingInterval);
-		this.scheduler = scheduler;
+			BluetoothConnectionFactory<BluetoothSocket> connectionFactory,
+			Executor ioExecutor,
+			Executor wakefulIoExecutor,
+			SecureRandom secureRandom,
+			AndroidExecutor androidExecutor,
+			Application app,
+			Clock clock,
+			Backoff backoff,
+			PluginCallback callback,
+			int maxLatency,
+			int maxIdleTime) {
+		super(connectionLimiter, connectionFactory, ioExecutor,
+				wakefulIoExecutor, secureRandom, backoff, callback,
+				maxLatency, maxIdleTime);
 		this.androidExecutor = androidExecutor;
-		this.appContext = appContext;
+		this.app = app;
 		this.clock = clock;
 	}
 
@@ -99,13 +105,13 @@ class AndroidBluetoothPlugin extends BluetoothPlugin<BluetoothServerSocket> {
 		filter.addAction(ACTION_STATE_CHANGED);
 		filter.addAction(ACTION_SCAN_MODE_CHANGED);
 		receiver = new BluetoothStateReceiver();
-		appContext.registerReceiver(receiver, filter);
+		app.registerReceiver(receiver, filter);
 	}
 
 	@Override
 	public void stop() {
 		super.stop();
-		if (receiver != null) appContext.unregisterReceiver(receiver);
+		if (receiver != null) app.unregisterReceiver(receiver);
 	}
 
 	@Override
@@ -162,7 +168,7 @@ class AndroidBluetoothPlugin extends BluetoothPlugin<BluetoothServerSocket> {
 	@Override
 	@Nullable
 	String getBluetoothAddress() {
-		String address = AndroidUtils.getBluetoothAddress(appContext, adapter);
+		String address = AndroidUtils.getBluetoothAddress(app, adapter);
 		return address.isEmpty() ? null : address;
 	}
 
@@ -180,13 +186,7 @@ class AndroidBluetoothPlugin extends BluetoothPlugin<BluetoothServerSocket> {
 	@Override
 	DuplexTransportConnection acceptConnection(BluetoothServerSocket ss)
 			throws IOException {
-		return wrapSocket(ss.accept());
-	}
-
-	private DuplexTransportConnection wrapSocket(BluetoothSocket s)
-			throws IOException {
-		return new AndroidBluetoothTransportConnection(this, connectionLimiter,
-				timeoutMonitor, appContext, scheduler, s);
+		return connectionFactory.wrapSocket(this, ss.accept());
 	}
 
 	@Override
@@ -203,7 +203,7 @@ class AndroidBluetoothPlugin extends BluetoothPlugin<BluetoothServerSocket> {
 		try {
 			s = d.createInsecureRfcommSocketToServiceRecord(u);
 			s.connect();
-			return wrapSocket(s);
+			return connectionFactory.wrapSocket(this, s);
 		} catch (IOException e) {
 			IoUtils.tryToClose(s, LOG, WARNING);
 			throw e;
@@ -238,7 +238,7 @@ class AndroidBluetoothPlugin extends BluetoothPlugin<BluetoothServerSocket> {
 		filter.addAction(ACTION_DISCOVERY_STARTED);
 		filter.addAction(ACTION_DISCOVERY_FINISHED);
 		filter.addAction(ACTION_FOUND);
-		appContext.registerReceiver(receiver, filter);
+		app.registerReceiver(receiver, filter);
 		try {
 			if (adapter.startDiscovery()) {
 				long now = clock.currentTimeMillis();
@@ -275,7 +275,7 @@ class AndroidBluetoothPlugin extends BluetoothPlugin<BluetoothServerSocket> {
 		} finally {
 			LOG.info("Cancelling discovery");
 			adapter.cancelDiscovery();
-			appContext.unregisterReceiver(receiver);
+			app.unregisterReceiver(receiver);
 		}
 		// Shuffle the addresses so we don't always try the same one first
 		shuffle(addresses);

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

@@ -1,57 +1,72 @@
 package org.briarproject.bramble.plugin.bluetooth;
 
-import android.content.Context;
+import android.app.Application;
+import android.bluetooth.BluetoothSocket;
 
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.io.TimeoutMonitor;
+import org.briarproject.bramble.api.lifecycle.IoExecutor;
 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;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPluginFactory;
 import org.briarproject.bramble.api.system.AndroidExecutor;
+import org.briarproject.bramble.api.system.AndroidWakeLockManager;
 import org.briarproject.bramble.api.system.Clock;
+import org.briarproject.bramble.api.system.WakefulIoExecutor;
 
 import java.security.SecureRandom;
 import java.util.concurrent.Executor;
-import java.util.concurrent.ScheduledExecutorService;
 
 import javax.annotation.concurrent.Immutable;
+import javax.inject.Inject;
 
-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 Executor ioExecutor, wakefulIoExecutor;
 	private final AndroidExecutor androidExecutor;
-	private final Context appContext;
+	private final AndroidWakeLockManager wakeLockManager;
+	private final Application app;
 	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) {
+	@Inject
+	public AndroidBluetoothPluginFactory(@IoExecutor Executor ioExecutor,
+			@WakefulIoExecutor Executor wakefulIoExecutor,
+			AndroidExecutor androidExecutor,
+			AndroidWakeLockManager wakeLockManager,
+			Application app,
+			SecureRandom secureRandom,
+			EventBus eventBus,
+			Clock clock,
+			TimeoutMonitor timeoutMonitor,
+			BackoffFactory backoffFactory) {
 		this.ioExecutor = ioExecutor;
-		this.scheduler = scheduler;
+		this.wakefulIoExecutor = wakefulIoExecutor;
 		this.androidExecutor = androidExecutor;
-		this.appContext = appContext;
+		this.wakeLockManager = wakeLockManager;
+		this.app = app;
 		this.secureRandom = secureRandom;
 		this.eventBus = eventBus;
 		this.clock = clock;
 		this.timeoutMonitor = timeoutMonitor;
+		this.backoffFactory = backoffFactory;
 	}
 
 	@Override
@@ -68,10 +83,15 @@ public class AndroidBluetoothPluginFactory implements DuplexPluginFactory {
 	public DuplexPlugin createPlugin(PluginCallback callback) {
 		BluetoothConnectionLimiter connectionLimiter =
 				new BluetoothConnectionLimiterImpl(eventBus);
+		BluetoothConnectionFactory<BluetoothSocket> connectionFactory =
+				new AndroidBluetoothConnectionFactory(connectionLimiter,
+						wakeLockManager, timeoutMonitor);
+		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);
+				connectionLimiter, connectionFactory, ioExecutor,
+				wakefulIoExecutor, secureRandom, androidExecutor, app,
+				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 +1,19 @@
 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 org.briarproject.bramble.api.system.AndroidWakeLock;
+import org.briarproject.bramble.api.system.AndroidWakeLockManager;
 
 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
@@ -28,25 +21,21 @@ class AndroidBluetoothTransportConnection
 		extends AbstractDuplexTransportConnection {
 
 	private final BluetoothConnectionLimiter connectionLimiter;
-	private final RenewableWakeLock wakeLock;
 	private final BluetoothSocket socket;
 	private final InputStream in;
+	private final AndroidWakeLock wakeLock;
 
 	AndroidBluetoothTransportConnection(Plugin plugin,
 			BluetoothConnectionLimiter connectionLimiter,
-			TimeoutMonitor timeoutMonitor, Context appContext,
-			ScheduledExecutorService scheduler, BluetoothSocket socket)
-			throws IOException {
+			AndroidWakeLockManager wakeLockManager,
+			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 = wakeLockManager.createWakeLock("BluetoothConnection");
 		wakeLock.acquire();
 		String address = socket.getRemoteDevice().getAddress();
 		if (isValidBluetoothAddress(address)) remote.put(PROP_ADDRESS, address);
@@ -66,6 +55,7 @@ class AndroidBluetoothTransportConnection
 	protected void closeConnection(boolean exception) throws IOException {
 		try {
 			socket.close();
+			in.close();
 		} finally {
 			wakeLock.release();
 			connectionLimiter.connectionClosed(this);

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

@@ -1,7 +1,7 @@
 package org.briarproject.bramble.plugin.tcp;
 
 import android.annotation.TargetApi;
-import android.content.Context;
+import android.app.Application;
 import android.net.ConnectivityManager;
 import android.net.LinkAddress;
 import android.net.LinkProperties;
@@ -15,6 +15,7 @@ import org.briarproject.bramble.api.Pair;
 import org.briarproject.bramble.api.event.Event;
 import org.briarproject.bramble.api.network.event.NetworkStatusEvent;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.Backoff;
 import org.briarproject.bramble.api.plugin.PluginCallback;
 import org.briarproject.bramble.api.settings.Settings;
 
@@ -41,6 +42,7 @@ 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.nullsafety.NullSafety.requireNonNull;
 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;
@@ -60,20 +62,22 @@ 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,
-				connectionTimeout);
+	AndroidLanTcpPlugin(Executor ioExecutor,
+			Executor wakefulIoExecutor,
+			Application app,
+			Backoff backoff,
+			PluginCallback callback,
+			int maxLatency,
+			int maxIdleTime,
+			int connectionTimeout) {
+		super(ioExecutor, wakefulIoExecutor, backoff, callback, maxLatency,
+				maxIdleTime, connectionTimeout);
 		// Don't execute more than one connection status check at a time
 		connectionStatusExecutor =
 				new PoliteExecutor("AndroidLanTcpPlugin", ioExecutor, 1);
-		ConnectivityManager connectivityManager = (ConnectivityManager)
-				appContext.getSystemService(CONNECTIVITY_SERVICE);
-		if (connectivityManager == null) throw new AssertionError();
-		this.connectivityManager = connectivityManager;
-		wifiManager = (WifiManager) appContext.getApplicationContext()
-				.getSystemService(WIFI_SERVICE);
+		connectivityManager = (ConnectivityManager)
+				requireNonNull(app.getSystemService(CONNECTIVITY_SERVICE));
+		wifiManager = (WifiManager) app.getSystemService(WIFI_SERVICE);
 		socketFactory = SocketFactory.getDefault();
 	}
 
@@ -273,11 +277,11 @@ class AndroidLanTcpPlugin extends LanTcpPlugin {
 				// make outgoing connections on API 21+ if another network
 				// has internet access
 				socketFactory = SocketFactory.getDefault();
-				if (s == INACTIVE) bind();
+				bind();
 			} else {
 				LOG.info("Connected to wifi");
 				socketFactory = getSocketFactory();
-				if (s == INACTIVE) bind();
+				bind();
 			}
 		});
 	}

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

@@ -1,40 +1,52 @@
 package org.briarproject.bramble.plugin.tcp;
 
-import android.content.Context;
+import android.app.Application;
 
 import org.briarproject.bramble.api.event.EventBus;
+import org.briarproject.bramble.api.lifecycle.IoExecutor;
 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;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPluginFactory;
+import org.briarproject.bramble.api.system.WakefulIoExecutor;
 
 import java.util.concurrent.Executor;
 
 import javax.annotation.concurrent.Immutable;
+import javax.inject.Inject;
 
-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 Executor ioExecutor, wakefulIoExecutor;
 	private final EventBus eventBus;
-	private final Context appContext;
+	private final BackoffFactory backoffFactory;
+	private final Application app;
 
-	public AndroidLanTcpPluginFactory(Executor ioExecutor, EventBus eventBus,
-			Context appContext) {
+	@Inject
+	public AndroidLanTcpPluginFactory(@IoExecutor Executor ioExecutor,
+			@WakefulIoExecutor Executor wakefulIoExecutor,
+			EventBus eventBus,
+			BackoffFactory backoffFactory,
+			Application app) {
 		this.ioExecutor = ioExecutor;
+		this.wakefulIoExecutor = wakefulIoExecutor;
 		this.eventBus = eventBus;
-		this.appContext = appContext;
+		this.backoffFactory = backoffFactory;
+		this.app = app;
 	}
 
 	@Override
@@ -49,9 +61,11 @@ 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);
+				wakefulIoExecutor, app, 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

@@ -1,61 +1,60 @@
 package org.briarproject.bramble.plugin.tor;
 
-import android.content.Context;
+import android.app.Application;
 import android.content.pm.PackageInfo;
 import android.content.pm.PackageManager;
 import android.content.pm.PackageManager.NameNotFoundException;
-import android.os.PowerManager;
 
 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.AndroidWakeLock;
+import org.briarproject.bramble.api.system.AndroidWakeLockManager;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.api.system.LocationUtils;
 import org.briarproject.bramble.api.system.ResourceProvider;
-import org.briarproject.bramble.util.RenewableWakeLock;
 
+import java.io.File;
 import java.io.IOException;
 import java.util.concurrent.Executor;
-import java.util.concurrent.ScheduledExecutorService;
 
 import javax.net.SocketFactory;
 
-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
 class AndroidTorPlugin extends TorPlugin {
 
-	private final Context appContext;
-	private final RenewableWakeLock wakeLock;
+	private final Application app;
+	private final AndroidWakeLock wakeLock;
 
-	AndroidTorPlugin(Executor ioExecutor, ScheduledExecutorService scheduler,
-			Context appContext, NetworkManager networkManager,
-			LocationUtils locationUtils, SocketFactory torSocketFactory,
-			Clock clock, ResourceProvider resourceProvider,
+	AndroidTorPlugin(Executor ioExecutor,
+			Executor wakefulIoExecutor,
+			Application app,
+			NetworkManager networkManager,
+			LocationUtils locationUtils,
+			SocketFactory torSocketFactory,
+			Clock clock,
+			ResourceProvider resourceProvider,
 			CircumventionProvider circumventionProvider,
 			BatteryManager batteryManager,
+			AndroidWakeLockManager wakeLockManager,
+			Backoff backoff,
 			TorRendezvousCrypto torRendezvousCrypto,
-			PluginCallback callback, String architecture, int maxLatency,
-			int maxIdleTime, int initialPollingInterval,
-			int stablePollingInterval) {
-		super(ioExecutor, networkManager, locationUtils, torSocketFactory,
-				clock, resourceProvider, circumventionProvider, batteryManager,
+			PluginCallback callback,
+			String architecture,
+			int maxLatency,
+			int maxIdleTime,
+			File torDirectory) {
+		super(ioExecutor, wakefulIoExecutor, networkManager, locationUtils,
+				torSocketFactory, clock, resourceProvider,
+				circumventionProvider, batteryManager, backoff,
 				torRendezvousCrypto, callback, architecture, maxLatency,
-				maxIdleTime, initialPollingInterval, stablePollingInterval,
-				appContext.getDir("tor", MODE_PRIVATE));
-		this.appContext = appContext;
-		PowerManager pm = (PowerManager)
-				appContext.getSystemService(POWER_SERVICE);
-		if (pm == null) throw new AssertionError();
-		wakeLock = new RenewableWakeLock(pm, scheduler, PARTIAL_WAKE_LOCK,
-				getWakeLockTag(appContext), 1, MINUTES);
+				maxIdleTime, torDirectory);
+		this.app = app;
+		wakeLock = wakeLockManager.createWakeLock("TorPlugin");
 	}
 
 	@Override
@@ -66,8 +65,8 @@ class AndroidTorPlugin extends TorPlugin {
 	@Override
 	protected long getLastUpdateTime() {
 		try {
-			PackageManager pm = appContext.getPackageManager();
-			PackageInfo pi = pm.getPackageInfo(appContext.getPackageName(), 0);
+			PackageManager pm = app.getPackageManager();
+			PackageInfo pi = pm.getPackageInfo(app.getPackageName(), 0);
 			return pi.lastUpdateTime;
 		} catch (NameNotFoundException e) {
 			throw new AssertionError(e);

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

@@ -1,86 +1,91 @@
 package org.briarproject.bramble.plugin.tor;
 
-import android.content.Context;
+import android.app.Application;
 
 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.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.TorDirectory;
 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.system.AndroidWakeLockManager;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.api.system.LocationUtils;
 import org.briarproject.bramble.api.system.ResourceProvider;
+import org.briarproject.bramble.api.system.WakefulIoExecutor;
 import org.briarproject.bramble.util.AndroidUtils;
 
+import java.io.File;
 import java.util.concurrent.Executor;
-import java.util.concurrent.ScheduledExecutorService;
 import java.util.logging.Logger;
 
 import javax.annotation.concurrent.Immutable;
+import javax.inject.Inject;
 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);
+	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;
 
-	/**
-	 * 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 final Executor ioExecutor;
-	private final ScheduledExecutorService scheduler;
-	private final Context appContext;
+	private final Executor ioExecutor, wakefulIoExecutor;
+	private final Application app;
 	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;
+	private final AndroidWakeLockManager wakeLockManager;
 	private final Clock clock;
+	private final File torDirectory;
 
-	public AndroidTorPluginFactory(Executor ioExecutor,
-			ScheduledExecutorService scheduler, Context appContext,
-			NetworkManager networkManager, LocationUtils locationUtils,
-			EventBus eventBus, SocketFactory torSocketFactory,
+	@Inject
+	public AndroidTorPluginFactory(@IoExecutor Executor ioExecutor,
+			@WakefulIoExecutor Executor wakefulIoExecutor,
+			Application app,
+			NetworkManager networkManager,
+			LocationUtils locationUtils,
+			EventBus eventBus,
+			SocketFactory torSocketFactory,
+			BackoffFactory backoffFactory,
 			ResourceProvider resourceProvider,
 			CircumventionProvider circumventionProvider,
-			BatteryManager batteryManager, Clock clock) {
+			BatteryManager batteryManager,
+			AndroidWakeLockManager wakeLockManager,
+			Clock clock,
+			@TorDirectory File torDirectory) {
 		this.ioExecutor = ioExecutor;
-		this.scheduler = scheduler;
-		this.appContext = appContext;
+		this.wakefulIoExecutor = wakefulIoExecutor;
+		this.app = app;
 		this.networkManager = networkManager;
 		this.locationUtils = locationUtils;
 		this.eventBus = eventBus;
 		this.torSocketFactory = torSocketFactory;
+		this.backoffFactory = backoffFactory;
 		this.resourceProvider = resourceProvider;
 		this.circumventionProvider = circumventionProvider;
 		this.batteryManager = batteryManager;
+		this.wakeLockManager = wakeLockManager;
 		this.clock = clock;
+		this.torDirectory = torDirectory;
 	}
 
 	@Override
@@ -120,13 +125,15 @@ 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);
+		AndroidTorPlugin plugin = new AndroidTorPlugin(ioExecutor,
+				wakefulIoExecutor, app, networkManager, locationUtils,
+				torSocketFactory, clock, resourceProvider,
+				circumventionProvider, batteryManager, wakeLockManager,
+				backoff, torRendezvousCrypto, callback, architecture,
+				MAX_LATENCY, MAX_IDLE_TIME, torDirectory);
 		eventBus.addListener(plugin);
 		return plugin;
 	}

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

@@ -0,0 +1,18 @@
+package org.briarproject.bramble.system;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+@NotNullByDefault
+interface AlarmConstants {
+
+	/**
+	 * Request code for the broadcast intent attached to the periodic alarm.
+	 */
+	int REQUEST_ALARM = 1;
+
+	/**
+	 * Key for storing the process ID in the extras of the periodic alarm's
+	 * intent. This allows us to ignore alarms scheduled by dead processes.
+	 */
+	String EXTRA_PID = "org.briarproject.bramble.EXTRA_PID";
+}

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

@@ -0,0 +1,17 @@
+package org.briarproject.bramble.system;
+
+import android.content.BroadcastReceiver;
+import android.content.Context;
+import android.content.Intent;
+
+import org.briarproject.bramble.BrambleApplication;
+
+public class AlarmReceiver extends BroadcastReceiver {
+
+	@Override
+	public void onReceive(Context ctx, Intent intent) {
+		BrambleApplication app =
+				(BrambleApplication) ctx.getApplicationContext();
+		app.getBrambleAppComponent().alarmListener().onAlarm(intent);
+	}
+}

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

@@ -1,12 +1,17 @@
 package org.briarproject.bramble.system;
 
 import org.briarproject.bramble.api.event.EventExecutor;
+import org.briarproject.bramble.api.lifecycle.LifecycleManager;
 import org.briarproject.bramble.api.system.AndroidExecutor;
+import org.briarproject.bramble.api.system.AndroidWakeLockManager;
 import org.briarproject.bramble.api.system.LocationUtils;
 import org.briarproject.bramble.api.system.ResourceProvider;
 import org.briarproject.bramble.api.system.SecureRandomProvider;
 
 import java.util.concurrent.Executor;
+import java.util.concurrent.RejectedExecutionHandler;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.ScheduledThreadPoolExecutor;
 
 import javax.inject.Singleton;
 
@@ -16,6 +21,23 @@ import dagger.Provides;
 @Module
 public class AndroidSystemModule {
 
+	private final ScheduledExecutorService scheduledExecutorService;
+
+	public AndroidSystemModule() {
+		// Discard tasks that are submitted during shutdown
+		RejectedExecutionHandler policy =
+				new ScheduledThreadPoolExecutor.DiscardPolicy();
+		scheduledExecutorService = new ScheduledThreadPoolExecutor(1, policy);
+	}
+
+	@Provides
+	@Singleton
+	ScheduledExecutorService provideScheduledExecutorService(
+			LifecycleManager lifecycleManager) {
+		lifecycleManager.registerForShutdown(scheduledExecutorService);
+		return scheduledExecutorService;
+	}
+
 	@Provides
 	@Singleton
 	SecureRandomProvider provideSecureRandomProvider(
@@ -47,4 +69,11 @@ public class AndroidSystemModule {
 	ResourceProvider provideResourceProvider(AndroidResourceProvider provider) {
 		return provider;
 	}
+
+	@Provides
+	@Singleton
+	AndroidWakeLockManager provideWakeLockManager(
+			AndroidWakeLockManagerImpl wakeLockManager) {
+		return wakeLockManager;
+	}
 }

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

@@ -0,0 +1,242 @@
+package org.briarproject.bramble.system;
+
+import android.annotation.TargetApi;
+import android.app.AlarmManager;
+import android.app.Application;
+import android.app.PendingIntent;
+import android.content.Intent;
+import android.os.Process;
+import android.os.SystemClock;
+
+import org.briarproject.bramble.api.lifecycle.Service;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.system.AlarmListener;
+import org.briarproject.bramble.api.system.AndroidWakeLockManager;
+import org.briarproject.bramble.api.system.TaskScheduler;
+import org.briarproject.bramble.api.system.Wakeful;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.PriorityQueue;
+import java.util.Queue;
+import java.util.concurrent.Executor;
+import java.util.concurrent.Future;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.logging.Logger;
+
+import javax.annotation.concurrent.GuardedBy;
+import javax.annotation.concurrent.ThreadSafe;
+
+import static android.app.AlarmManager.ELAPSED_REALTIME_WAKEUP;
+import static android.app.AlarmManager.INTERVAL_FIFTEEN_MINUTES;
+import static android.app.PendingIntent.FLAG_CANCEL_CURRENT;
+import static android.content.Context.ALARM_SERVICE;
+import static android.os.Build.VERSION.SDK_INT;
+import static java.util.Objects.requireNonNull;
+import static java.util.concurrent.TimeUnit.MILLISECONDS;
+import static java.util.logging.Level.INFO;
+import static java.util.logging.Logger.getLogger;
+import static org.briarproject.bramble.system.AlarmConstants.EXTRA_PID;
+import static org.briarproject.bramble.system.AlarmConstants.REQUEST_ALARM;
+
+@ThreadSafe
+@NotNullByDefault
+class AndroidTaskScheduler implements TaskScheduler, Service, AlarmListener {
+
+	private static final Logger LOG =
+			getLogger(AndroidTaskScheduler.class.getName());
+
+	private static final long ALARM_MS = INTERVAL_FIFTEEN_MINUTES;
+
+	private final Application app;
+	private final AndroidWakeLockManager wakeLockManager;
+	private final ScheduledExecutorService scheduledExecutorService;
+	private final AlarmManager alarmManager;
+
+	private final Object lock = new Object();
+	@GuardedBy("lock")
+	private final Queue<ScheduledTask> tasks = new PriorityQueue<>();
+
+	AndroidTaskScheduler(Application app,
+			AndroidWakeLockManager wakeLockManager,
+			ScheduledExecutorService scheduledExecutorService) {
+		this.app = app;
+		this.wakeLockManager = wakeLockManager;
+		this.scheduledExecutorService = scheduledExecutorService;
+		alarmManager = (AlarmManager)
+				requireNonNull(app.getSystemService(ALARM_SERVICE));
+	}
+
+	@Override
+	public void startService() {
+		scheduleAlarm();
+	}
+
+	@Override
+	public void stopService() {
+		cancelAlarm();
+	}
+
+	@Override
+	public Cancellable schedule(Runnable task, Executor executor, long delay,
+			TimeUnit unit) {
+		AtomicBoolean cancelled = new AtomicBoolean(false);
+		return schedule(task, executor, delay, unit, cancelled);
+	}
+
+	@Override
+	public Cancellable scheduleWithFixedDelay(Runnable task, Executor executor,
+			long delay, long interval, TimeUnit unit) {
+		AtomicBoolean cancelled = new AtomicBoolean(false);
+		return scheduleWithFixedDelay(task, executor, delay, interval, unit,
+				cancelled);
+	}
+
+	@Override
+	public void onAlarm(Intent intent) {
+		wakeLockManager.runWakefully(() -> {
+			int extraPid = intent.getIntExtra(EXTRA_PID, -1);
+			int currentPid = Process.myPid();
+			if (extraPid == currentPid) {
+				LOG.info("Alarm");
+				rescheduleAlarm();
+				runDueTasks();
+			} else if (LOG.isLoggable(INFO)) {
+				LOG.info("Ignoring alarm with PID " + extraPid
+						+ ", current PID is " + currentPid);
+			}
+		}, "TaskAlarm");
+	}
+
+	private Cancellable schedule(Runnable task, Executor executor, long delay,
+			TimeUnit unit, AtomicBoolean cancelled) {
+		long now = SystemClock.elapsedRealtime();
+		long dueMillis = now + MILLISECONDS.convert(delay, unit);
+		Runnable wakeful = () ->
+				wakeLockManager.executeWakefully(task, executor, "TaskHandoff");
+		Future<?> check = scheduleCheckForDueTasks(delay, unit);
+		ScheduledTask s = new ScheduledTask(wakeful, dueMillis, check,
+				cancelled);
+		synchronized (lock) {
+			tasks.add(s);
+		}
+		return s;
+	}
+
+	private Cancellable scheduleWithFixedDelay(Runnable task, Executor executor,
+			long delay, long interval, TimeUnit unit, AtomicBoolean cancelled) {
+		// All executions of this periodic task share a cancelled flag
+		Runnable wrapped = () -> {
+			task.run();
+			scheduleWithFixedDelay(task, executor, interval, interval, unit,
+					cancelled);
+		};
+		return schedule(wrapped, executor, delay, unit, cancelled);
+	}
+
+	private Future<?> scheduleCheckForDueTasks(long delay, TimeUnit unit) {
+		Runnable wakeful = () -> wakeLockManager.runWakefully(
+				this::runDueTasks, "TaskScheduler");
+		return scheduledExecutorService.schedule(wakeful, delay, unit);
+	}
+
+	@Wakeful
+	private void runDueTasks() {
+		long now = SystemClock.elapsedRealtime();
+		List<ScheduledTask> due = new ArrayList<>();
+		synchronized (lock) {
+			while (true) {
+				ScheduledTask s = tasks.peek();
+				if (s == null || s.dueMillis > now) break;
+				due.add(tasks.remove());
+			}
+		}
+		if (LOG.isLoggable(INFO)) {
+			LOG.info("Running " + due.size() + " due tasks");
+		}
+		for (ScheduledTask s : due) {
+			if (LOG.isLoggable(INFO)) {
+				LOG.info("Task is " + (now - s.dueMillis) + " ms overdue");
+			}
+			s.run();
+		}
+	}
+
+	private void scheduleAlarm() {
+		if (SDK_INT >= 23) scheduleIdleAlarm();
+		else scheduleInexactRepeatingAlarm();
+	}
+
+	private void rescheduleAlarm() {
+		// If SDK_INT < 23 the alarm repeats automatically
+		if (SDK_INT >= 23) scheduleIdleAlarm();
+	}
+
+	private void cancelAlarm() {
+		alarmManager.cancel(getAlarmPendingIntent());
+	}
+
+	private void scheduleInexactRepeatingAlarm() {
+		alarmManager.setInexactRepeating(ELAPSED_REALTIME_WAKEUP,
+				SystemClock.elapsedRealtime() + ALARM_MS, ALARM_MS,
+				getAlarmPendingIntent());
+	}
+
+	@TargetApi(23)
+	private void scheduleIdleAlarm() {
+		alarmManager.setAndAllowWhileIdle(ELAPSED_REALTIME_WAKEUP,
+				SystemClock.elapsedRealtime() + ALARM_MS,
+				getAlarmPendingIntent());
+	}
+
+	private PendingIntent getAlarmPendingIntent() {
+		Intent i = new Intent(app, AlarmReceiver.class);
+		i.putExtra(EXTRA_PID, android.os.Process.myPid());
+		return PendingIntent.getBroadcast(app, REQUEST_ALARM, i,
+				FLAG_CANCEL_CURRENT);
+	}
+
+	private class ScheduledTask
+			implements Runnable, Cancellable, Comparable<ScheduledTask> {
+
+		private final Runnable task;
+		private final long dueMillis;
+		private final Future<?> check;
+		private final AtomicBoolean cancelled;
+
+		public ScheduledTask(Runnable task, long dueMillis,
+				Future<?> check, AtomicBoolean cancelled) {
+			this.task = task;
+			this.dueMillis = dueMillis;
+			this.check = check;
+			this.cancelled = cancelled;
+		}
+
+		@Override
+		public void run() {
+			if (!cancelled.get()) task.run();
+		}
+
+		@Override
+		public void cancel() {
+			// Cancel any future executions of this task
+			cancelled.set(true);
+			// Cancel the scheduled check for due tasks
+			check.cancel(false);
+			// Remove the task from the queue
+			synchronized (lock) {
+				tasks.remove(this);
+			}
+		}
+
+		@Override
+		public int compareTo(ScheduledTask s) {
+			//noinspection UseCompareMethod
+			if (dueMillis < s.dueMillis) return -1;
+			if (dueMillis > s.dueMillis) return 1;
+			return 0;
+		}
+	}
+}

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

@@ -0,0 +1,49 @@
+package org.briarproject.bramble.system;
+
+import android.app.Application;
+
+import org.briarproject.bramble.api.lifecycle.LifecycleManager;
+import org.briarproject.bramble.api.system.AlarmListener;
+import org.briarproject.bramble.api.system.AndroidWakeLockManager;
+import org.briarproject.bramble.api.system.TaskScheduler;
+
+import java.util.concurrent.ScheduledExecutorService;
+
+import javax.inject.Inject;
+import javax.inject.Singleton;
+
+import dagger.Module;
+import dagger.Provides;
+
+@Module
+public class AndroidTaskSchedulerModule {
+
+	public static class EagerSingletons {
+		@Inject
+		AndroidTaskScheduler scheduler;
+	}
+
+	@Provides
+	@Singleton
+	AndroidTaskScheduler provideAndroidTaskScheduler(
+			LifecycleManager lifecycleManager, Application app,
+			AndroidWakeLockManager wakeLockManager,
+			ScheduledExecutorService scheduledExecutorService) {
+		AndroidTaskScheduler scheduler = new AndroidTaskScheduler(app,
+				wakeLockManager, scheduledExecutorService);
+		lifecycleManager.registerService(scheduler);
+		return scheduler;
+	}
+
+	@Provides
+	@Singleton
+	AlarmListener provideAlarmListener(AndroidTaskScheduler scheduler) {
+		return scheduler;
+	}
+
+	@Provides
+	@Singleton
+	TaskScheduler provideTaskScheduler(AndroidTaskScheduler scheduler) {
+		return scheduler;
+	}
+}

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

@@ -0,0 +1,74 @@
+package org.briarproject.bramble.system;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.system.AndroidWakeLock;
+
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.logging.Logger;
+
+import javax.annotation.concurrent.GuardedBy;
+import javax.annotation.concurrent.ThreadSafe;
+
+import static java.util.logging.Level.FINE;
+import static java.util.logging.Logger.getLogger;
+
+/**
+ * A wrapper around a {@link SharedWakeLock} that provides the more convenient
+ * semantics of {@link AndroidWakeLock} (i.e. calls to acquire() and release()
+ * don't need to be balanced).
+ */
+@ThreadSafe
+@NotNullByDefault
+class AndroidWakeLockImpl implements AndroidWakeLock {
+
+	private static final Logger LOG =
+			getLogger(AndroidWakeLockImpl.class.getName());
+
+	private static final AtomicInteger INSTANCE_ID = new AtomicInteger(0);
+
+	private final SharedWakeLock sharedWakeLock;
+	private final String tag;
+
+	private final Object lock = new Object();
+	@GuardedBy("lock")
+	private boolean held = false;
+
+	AndroidWakeLockImpl(SharedWakeLock sharedWakeLock, String tag) {
+		this.sharedWakeLock = sharedWakeLock;
+		this.tag = tag + "_" + INSTANCE_ID.getAndIncrement();
+	}
+
+	@Override
+	public void acquire() {
+		synchronized (lock) {
+			if (held) {
+				if (LOG.isLoggable(FINE)) {
+					LOG.fine(tag + " already acquired");
+				}
+			} else {
+				if (LOG.isLoggable(FINE)) {
+					LOG.fine(tag + " acquiring shared wake lock");
+				}
+				held = true;
+				sharedWakeLock.acquire();
+			}
+		}
+	}
+
+	@Override
+	public void release() {
+		synchronized (lock) {
+			if (held) {
+				if (LOG.isLoggable(FINE)) {
+					LOG.fine(tag + " releasing shared wake lock");
+				}
+				held = false;
+				sharedWakeLock.release();
+			} else {
+				if (LOG.isLoggable(FINE)) {
+					LOG.fine(tag + " already released");
+				}
+			}
+		}
+	}
+}

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

@@ -0,0 +1,119 @@
+package org.briarproject.bramble.system;
+
+import android.app.Application;
+import android.content.Context;
+import android.content.pm.PackageInfo;
+import android.content.pm.PackageManager;
+import android.os.PowerManager;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.system.AndroidWakeLock;
+import org.briarproject.bramble.api.system.AndroidWakeLockManager;
+
+import java.util.concurrent.Executor;
+import java.util.concurrent.ScheduledExecutorService;
+
+import javax.inject.Inject;
+
+import static android.content.Context.POWER_SERVICE;
+import static android.os.PowerManager.PARTIAL_WAKE_LOCK;
+import static java.util.concurrent.TimeUnit.MINUTES;
+import static java.util.concurrent.TimeUnit.SECONDS;
+import static org.briarproject.bramble.api.nullsafety.NullSafety.requireNonNull;
+
+@NotNullByDefault
+class AndroidWakeLockManagerImpl implements AndroidWakeLockManager {
+
+	/**
+	 * How often to replace the wake lock.
+	 */
+	private static final long LOCK_DURATION_MS = MINUTES.toMillis(1);
+
+	/**
+	 * Automatically release the lock this many milliseconds after it's due
+	 * to have been replaced and released.
+	 */
+	private static final long SAFETY_MARGIN_MS = SECONDS.toMillis(30);
+
+	private final SharedWakeLock sharedWakeLock;
+
+	@Inject
+	AndroidWakeLockManagerImpl(Application app,
+			ScheduledExecutorService scheduledExecutorService) {
+		PowerManager powerManager = (PowerManager)
+				requireNonNull(app.getSystemService(POWER_SERVICE));
+		String tag = getWakeLockTag(app);
+		sharedWakeLock = new RenewableWakeLock(powerManager,
+				scheduledExecutorService, PARTIAL_WAKE_LOCK, tag,
+				LOCK_DURATION_MS, SAFETY_MARGIN_MS);
+	}
+
+	@Override
+	public AndroidWakeLock createWakeLock(String tag) {
+		return new AndroidWakeLockImpl(sharedWakeLock, tag);
+	}
+
+	@Override
+	public void runWakefully(Runnable r, String tag) {
+		AndroidWakeLock wakeLock = createWakeLock(tag);
+		wakeLock.acquire();
+		try {
+			r.run();
+		} finally {
+			wakeLock.release();
+		}
+	}
+
+	@Override
+	public void executeWakefully(Runnable r, Executor executor, String tag) {
+		AndroidWakeLock wakeLock = createWakeLock(tag);
+		wakeLock.acquire();
+		try {
+			executor.execute(() -> {
+				try {
+					r.run();
+				} finally {
+					// Release the wake lock if the task throws an exception
+					wakeLock.release();
+				}
+			});
+		} catch (Exception e) {
+			// Release the wake lock if the executor throws an exception when
+			// we submit the task (in which case the release() call above won't
+			// happen)
+			wakeLock.release();
+			throw e;
+		}
+	}
+
+	@Override
+	public void executeWakefully(Runnable r, String tag) {
+		AndroidWakeLock wakeLock = createWakeLock(tag);
+		wakeLock.acquire();
+		try {
+			new Thread(() -> {
+				try {
+					r.run();
+				} finally {
+					wakeLock.release();
+				}
+			}).start();
+		} catch (Exception e) {
+			wakeLock.release();
+			throw e;
+		}
+	}
+
+	private String getWakeLockTag(Context ctx) {
+		PackageManager pm = ctx.getPackageManager();
+		for (PackageInfo info : pm.getInstalledPackages(0)) {
+			String name = info.packageName.toLowerCase();
+			if (name.startsWith("com.huawei.powergenie")) {
+				return "LocationManagerService";
+			} else if (name.startsWith("com.evenwell.powermonitor")) {
+				return "AudioIn";
+			}
+		}
+		return ctx.getPackageName();
+	}
+}

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

@@ -0,0 +1,23 @@
+package org.briarproject.bramble.system;
+
+import org.briarproject.bramble.api.lifecycle.IoExecutor;
+import org.briarproject.bramble.api.system.AndroidWakeLockManager;
+import org.briarproject.bramble.api.system.WakefulIoExecutor;
+
+import java.util.concurrent.Executor;
+
+import dagger.Module;
+import dagger.Provides;
+
+@Module
+public
+class AndroidWakefulIoExecutorModule {
+
+	@Provides
+	@WakefulIoExecutor
+	Executor provideWakefulIoExecutor(@IoExecutor Executor ioExecutor,
+			AndroidWakeLockManager wakeLockManager) {
+		return r -> wakeLockManager.executeWakefully(r, ioExecutor,
+				"WakefulIoExecutor");
+	}
+}

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

@@ -0,0 +1,130 @@
+package org.briarproject.bramble.system;
+
+import android.os.PowerManager;
+import android.os.PowerManager.WakeLock;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+import java.util.concurrent.Future;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.logging.Logger;
+
+import javax.annotation.Nullable;
+import javax.annotation.concurrent.GuardedBy;
+import javax.annotation.concurrent.ThreadSafe;
+
+import static java.util.concurrent.TimeUnit.MILLISECONDS;
+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.nullsafety.NullSafety.requireNonNull;
+
+@ThreadSafe
+@NotNullByDefault
+class RenewableWakeLock implements SharedWakeLock {
+
+	private static final Logger LOG =
+			getLogger(RenewableWakeLock.class.getName());
+
+	private final PowerManager powerManager;
+	private final ScheduledExecutorService scheduledExecutorService;
+	private final int levelAndFlags;
+	private final String tag;
+	private final long durationMs, safetyMarginMs;
+
+	private final Object lock = new Object();
+	@GuardedBy("lock")
+	@Nullable
+	private WakeLock wakeLock;
+	@GuardedBy("lock")
+	@Nullable
+	private Future<?> future;
+	@GuardedBy("lock")
+	private int refCount = 0;
+	@GuardedBy("lock")
+	private long acquired = 0;
+
+	RenewableWakeLock(PowerManager powerManager,
+			ScheduledExecutorService scheduledExecutorService,
+			int levelAndFlags,
+			String tag,
+			long durationMs,
+			long safetyMarginMs) {
+		this.powerManager = powerManager;
+		this.scheduledExecutorService = scheduledExecutorService;
+		this.levelAndFlags = levelAndFlags;
+		this.tag = tag;
+		this.durationMs = durationMs;
+		this.safetyMarginMs = safetyMarginMs;
+	}
+
+	@Override
+	public void acquire() {
+		synchronized (lock) {
+			refCount++;
+			if (refCount == 1) {
+				if (LOG.isLoggable(INFO)) {
+					LOG.info("Acquiring wake lock " + tag);
+				}
+				wakeLock = powerManager.newWakeLock(levelAndFlags, tag);
+				// We do our own reference counting so we can replace the lock
+				// TODO: Check whether using a ref-counted wake lock affects
+				//  power management apps
+				wakeLock.setReferenceCounted(false);
+				wakeLock.acquire(durationMs + safetyMarginMs);
+				future = scheduledExecutorService.schedule(this::renew,
+						durationMs, MILLISECONDS);
+				acquired = android.os.SystemClock.elapsedRealtime();
+			} else if (LOG.isLoggable(FINE)) {
+				LOG.fine("Wake lock " + tag + " has " + refCount + " holders");
+			}
+		}
+	}
+
+	private void renew() {
+		if (LOG.isLoggable(INFO)) LOG.info("Renewing wake lock " + tag);
+		synchronized (lock) {
+			if (wakeLock == null) {
+				LOG.info("Already released");
+				return;
+			}
+			if (LOG.isLoggable(FINE)) {
+				LOG.fine("Wake lock " + tag + " has " + refCount + " holders");
+			}
+			long now = android.os.SystemClock.elapsedRealtime();
+			long expiry = acquired + durationMs + safetyMarginMs;
+			if (now > expiry && LOG.isLoggable(WARNING)) {
+				LOG.warning("Wake lock expired " + (now - expiry) + " ms ago");
+			}
+			WakeLock oldWakeLock = wakeLock;
+			wakeLock = powerManager.newWakeLock(levelAndFlags, tag);
+			wakeLock.setReferenceCounted(false);
+			wakeLock.acquire(durationMs + safetyMarginMs);
+			oldWakeLock.release();
+			future = scheduledExecutorService.schedule(this::renew, durationMs,
+					MILLISECONDS);
+			acquired = now;
+		}
+	}
+
+	@Override
+	public void release() {
+		synchronized (lock) {
+			refCount--;
+			if (refCount == 0) {
+				if (LOG.isLoggable(INFO)) {
+					LOG.info("Releasing wake lock " + tag);
+				}
+				requireNonNull(future).cancel(false);
+				future = null;
+				requireNonNull(wakeLock).release();
+				wakeLock = null;
+				acquired = 0;
+			} else if (LOG.isLoggable(FINE)) {
+				LOG.fine("Wake lock " + tag + " has " + refCount + " holders");
+			}
+		}
+	}
+}
+

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

@@ -0,0 +1,22 @@
+package org.briarproject.bramble.system;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.system.AndroidWakeLock;
+
+@NotNullByDefault
+interface SharedWakeLock {
+
+	/**
+	 * Acquires the wake lock. This increments the wake lock's reference count,
+	 * so unlike {@link AndroidWakeLock#acquire()} every call to this method
+	 * must be followed by a balancing call to {@link #release()}.
+	 */
+	void acquire();
+
+	/**
+	 * Releases the wake lock. This decrements the wake lock's reference count,
+	 * so unlike {@link AndroidWakeLock#release()} every call to this method
+	 * must follow a balancing call to {@link #acquire()}.
+	 */
+	void release();
+}

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

@@ -1,100 +0,0 @@
-package org.briarproject.bramble.util;
-
-import android.os.PowerManager;
-
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-
-import java.util.concurrent.ScheduledExecutorService;
-import java.util.concurrent.ScheduledFuture;
-import java.util.concurrent.TimeUnit;
-import java.util.logging.Logger;
-
-import javax.annotation.Nullable;
-import javax.annotation.concurrent.ThreadSafe;
-
-import static java.util.concurrent.TimeUnit.MILLISECONDS;
-import static java.util.logging.Level.INFO;
-
-@ThreadSafe
-@NotNullByDefault
-public class RenewableWakeLock {
-
-	private static final Logger LOG =
-			Logger.getLogger(RenewableWakeLock.class.getName());
-
-	/**
-	 * Automatically release the lock this many milliseconds after it's due
-	 * to have been replaced and released.
-	 */
-	private static final int SAFETY_MARGIN_MS = 10_000;
-
-	private final PowerManager powerManager;
-	private final ScheduledExecutorService scheduler;
-	private final int levelAndFlags;
-	private final String tag;
-	private final long durationMs;
-	private final Runnable renewTask;
-
-	private final Object lock = new Object();
-	@Nullable
-	private PowerManager.WakeLock wakeLock; // Locking: lock
-	@Nullable
-	private ScheduledFuture future; // Locking: lock
-
-	public RenewableWakeLock(PowerManager powerManager,
-			ScheduledExecutorService scheduler, int levelAndFlags, String tag,
-			long duration, TimeUnit timeUnit) {
-		this.powerManager = powerManager;
-		this.scheduler = scheduler;
-		this.levelAndFlags = levelAndFlags;
-		this.tag = tag;
-		durationMs = MILLISECONDS.convert(duration, timeUnit);
-		renewTask = this::renew;
-	}
-
-	public void acquire() {
-		if (LOG.isLoggable(INFO)) LOG.info("Acquiring wake lock " + tag);
-		synchronized (lock) {
-			if (wakeLock != null) {
-				LOG.info("Already acquired");
-				return;
-			}
-			wakeLock = powerManager.newWakeLock(levelAndFlags, tag);
-			wakeLock.setReferenceCounted(false);
-			wakeLock.acquire(durationMs + SAFETY_MARGIN_MS);
-			future = scheduler.schedule(renewTask, durationMs, MILLISECONDS);
-		}
-	}
-
-	private void renew() {
-		if (LOG.isLoggable(INFO)) LOG.info("Renewing wake lock " + tag);
-		synchronized (lock) {
-			if (wakeLock == null) {
-				LOG.info("Already released");
-				return;
-			}
-			PowerManager.WakeLock oldWakeLock = wakeLock;
-			wakeLock = powerManager.newWakeLock(levelAndFlags, tag);
-			wakeLock.setReferenceCounted(false);
-			wakeLock.acquire(durationMs + SAFETY_MARGIN_MS);
-			oldWakeLock.release();
-			future = scheduler.schedule(renewTask, durationMs, MILLISECONDS);
-		}
-	}
-
-	public void release() {
-		if (LOG.isLoggable(INFO)) LOG.info("Releasing wake lock " + tag);
-		synchronized (lock) {
-			if (wakeLock == null) {
-				LOG.info("Already released");
-				return;
-			}
-			if (future == null) throw new AssertionError();
-			future.cancel(false);
-			future = null;
-			wakeLock.release();
-			wakeLock = null;
-		}
-	}
-}
-

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

@@ -5,6 +5,9 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 /**
  * Interface for strengthening a password-based key, for example by using a
  * key stored in a key management service or hardware security module.
+ *
+ * TODO: Remove after a reasonable migration period unless we can work around
+ * Android keymaster bugs. Added 2020-02-24
  */
 @NotNullByDefault
 public interface KeyStrengthener {

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

@@ -7,6 +7,10 @@ public interface TimeoutMonitor {
 	/**
 	 * Returns an {@link InputStream} that wraps the given stream and allows
 	 * read timeouts to be detected.
+	 * <p>
+	 * The returned stream must be {@link InputStream#close() closed} when it's
+	 * no longer needed to ensure that resources held by the timeout monitor
+	 * are released.
 	 *
 	 * @param timeoutMs The read timeout in milliseconds. Timeouts will be
 	 * detected eventually but are not guaranteed to be detected immediately.

bramble-api/src/main/java/org/briarproject/bramble/api/lifecycle/LifecycleManager.java

@@ -5,6 +5,7 @@ import org.briarproject.bramble.api.db.DatabaseComponent;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.Transaction;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.system.Wakeful;
 
 import java.util.concurrent.ExecutorService;
 
@@ -65,6 +66,7 @@ public interface LifecycleManager {
 	 * Opens the {@link DatabaseComponent} using the given key and starts any
 	 * registered {@link Service Services}.
 	 */
+	@Wakeful
 	StartResult startServices(SecretKey dbKey);
 
 	/**
@@ -72,6 +74,7 @@ public interface LifecycleManager {
 	 * registered {@link ExecutorService ExecutorServices}, and closes the
 	 * {@link DatabaseComponent}.
 	 */
+	@Wakeful
 	void stopServices();
 
 	/**
@@ -104,6 +107,7 @@ public interface LifecycleManager {
 		 *
 		 * @param txn A read-write transaction
 		 */
+		@Wakeful
 		void onDatabaseOpened(Transaction txn) throws DbException;
 	}
 }

bramble-api/src/main/java/org/briarproject/bramble/api/lifecycle/Service.java

@@ -1,16 +1,20 @@
 package org.briarproject.bramble.api.lifecycle;
 
+import org.briarproject.bramble.api.system.Wakeful;
+
 public interface Service {
 
 	/**
-	 * Starts the service.This method must not be called concurrently with
+	 * Starts the service. This method must not be called concurrently with
 	 * {@link #stopService()}.
 	 */
+	@Wakeful
 	void startService() throws ServiceException;
 
 	/**
 	 * Stops the service. This method must not be called concurrently with
 	 * {@link #startService()}.
 	 */
+	@Wakeful
 	void stopService() throws ServiceException;
 }

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

@@ -10,6 +10,12 @@ public interface BluetoothConstants {
 	String PROP_ADDRESS = "address";
 	String PROP_UUID = "uuid";
 
-	// Default value for PREF_PLUGIN_ENABLE
+	// Local settings (not shared with contacts)
+	String PREF_ADDRESS_IS_REFLECTED = "addressIsReflected";
+	String PREF_EVER_CONNECTED = "everConnected";
+
+	// Default values for local settings
 	boolean DEFAULT_PREF_PLUGIN_ENABLE = false;
+	boolean DEFAULT_PREF_ADDRESS_IS_REFLECTED = false;
+	boolean DEFAULT_PREF_EVER_CONNECTED = false;
 }

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

@@ -4,6 +4,7 @@ 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 org.briarproject.bramble.api.system.Wakeful;
 
 import java.util.Collection;
 
@@ -70,11 +71,13 @@ public interface Plugin {
 	/**
 	 * Starts the plugin.
 	 */
+	@Wakeful
 	void start() throws PluginException;
 
 	/**
 	 * Stops the plugin.
 	 */
+	@Wakeful
 	void stop() throws PluginException;
 
 	/**
@@ -106,6 +109,7 @@ public interface Plugin {
 	 * Attempts to create connections using the given transport properties,
 	 * passing any created connections to the corresponding handlers.
 	 */
+	@Wakeful
 	void poll(Collection<Pair<TransportProperties, ConnectionHandler>>
 			properties);
 }

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

@@ -8,6 +8,8 @@ import org.briarproject.bramble.api.plugin.event.TransportStateEvent;
 import org.briarproject.bramble.api.properties.TransportProperties;
 import org.briarproject.bramble.api.settings.Settings;
 
+import java.util.Collection;
+
 /**
  * An interface through which a transport plugin interacts with the rest of
  * the application.
@@ -25,6 +27,11 @@ public interface PluginCallback extends ConnectionHandler {
 	 */
 	TransportProperties getLocalProperties();
 
+	/**
+	 * Returns the plugin's remote transport properties.
+	 */
+	Collection<TransportProperties> getRemoteProperties();
+
 	/**
 	 * Merges the given settings with the plugin's settings
 	 */

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

@@ -1,5 +1,6 @@
-package org.briarproject.bramble.api.system;
+package org.briarproject.bramble.api.plugin;
 
+import java.io.File;
 import java.lang.annotation.Retention;
 import java.lang.annotation.Target;
 
@@ -11,15 +12,11 @@ import static java.lang.annotation.ElementType.PARAMETER;
 import static java.lang.annotation.RetentionPolicy.RUNTIME;
 
 /**
- * Annotation for injecting a scheduled executor service
- * that can be used to schedule the execution of tasks.
- * <p>
- * The service should <b>only</b> be used for running tasks on other executors
- * at scheduled times.
- * No significant work should be run by the service itself!
+ * Annotation for injecting the {@link File directory} where the Tor plugin
+ * should store its state.
  */
 @Qualifier
 @Target({FIELD, METHOD, PARAMETER})
 @Retention(RUNTIME)
-public @interface Scheduler {
-}
+public @interface TorDirectory {
+}

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

@@ -8,6 +8,7 @@ import org.briarproject.bramble.api.plugin.Plugin;
 import org.briarproject.bramble.api.properties.TransportProperties;
 import org.briarproject.bramble.api.rendezvous.KeyMaterialSource;
 import org.briarproject.bramble.api.rendezvous.RendezvousEndpoint;
+import org.briarproject.bramble.api.system.Wakeful;
 
 import javax.annotation.Nullable;
 
@@ -21,6 +22,7 @@ public interface DuplexPlugin extends Plugin {
 	 * Attempts to create and return a connection using the given transport
 	 * properties. Returns null if a connection cannot be created.
 	 */
+	@Wakeful
 	@Nullable
 	DuplexTransportConnection createConnection(TransportProperties p);
 

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/simplex/SimplexPlugin.java

@@ -5,6 +5,7 @@ import org.briarproject.bramble.api.plugin.Plugin;
 import org.briarproject.bramble.api.plugin.TransportConnectionReader;
 import org.briarproject.bramble.api.plugin.TransportConnectionWriter;
 import org.briarproject.bramble.api.properties.TransportProperties;
+import org.briarproject.bramble.api.system.Wakeful;
 
 import javax.annotation.Nullable;
 
@@ -18,6 +19,7 @@ public interface SimplexPlugin extends Plugin {
 	 * Attempts to create and return a reader for the given transport
 	 * properties. Returns null if a reader cannot be created.
 	 */
+	@Wakeful
 	@Nullable
 	TransportConnectionReader createReader(TransportProperties p);
 
@@ -25,6 +27,7 @@ public interface SimplexPlugin extends Plugin {
 	 * Attempts to create and return a writer for the given transport
 	 * properties. Returns null if a writer cannot be created.
 	 */
+	@Wakeful
 	@Nullable
 	TransportConnectionWriter createWriter(TransportProperties p);
 }

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

@@ -12,6 +12,11 @@ public interface TransportPropertyConstants {
 	 */
 	int MAX_PROPERTY_LENGTH = 100;
 
+	/**
+	 * Prefix for keys that represent reflected properties.
+	 */
+	String REFLECTED_PROPERTY_PREFIX = "u:";
+
 	/**
 	 * Message metadata key for the transport ID of a local or remote update,
 	 * as a BDF string.

bramble-api/src/main/java/org/briarproject/bramble/api/properties/event/RemoteTransportPropertiesUpdatedEvent.java

@@ -0,0 +1,27 @@
+package org.briarproject.bramble.api.properties.event;
+
+import org.briarproject.bramble.api.event.Event;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.TransportId;
+import org.briarproject.bramble.api.properties.TransportProperties;
+
+import javax.annotation.concurrent.Immutable;
+
+/**
+ * An event that is broadcast when {@link TransportProperties} are received
+ * from a contact.
+ */
+@Immutable
+@NotNullByDefault
+public class RemoteTransportPropertiesUpdatedEvent extends Event {
+
+	private final TransportId transportId;
+
+	public RemoteTransportPropertiesUpdatedEvent(TransportId transportId) {
+		this.transportId = transportId;
+	}
+
+	public TransportId getTransportId() {
+		return transportId;
+	}
+}

bramble-api/src/main/java/org/briarproject/bramble/api/system/TaskScheduler.java

@@ -0,0 +1,43 @@
+package org.briarproject.bramble.api.system;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+import java.util.concurrent.Executor;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * A service that can be used to schedule the execution of tasks.
+ */
+@NotNullByDefault
+public interface TaskScheduler {
+
+	/**
+	 * Submits the given task to the given executor after the given delay.
+	 * <p>
+	 * If the platform supports wake locks, a wake lock will be held while
+	 * submitting and running the task.
+	 */
+	Cancellable schedule(Runnable task, Executor executor, long delay,
+			TimeUnit unit);
+
+	/**
+	 * Submits the given task to the given executor after the given delay,
+	 * and then repeatedly with the given interval between executions
+	 * (measured from the end of one execution to the beginning of the next).
+	 * <p>
+	 * If the platform supports wake locks, a wake lock will be held while
+	 * submitting and running the task.
+	 */
+	Cancellable scheduleWithFixedDelay(Runnable task, Executor executor,
+			long delay, long interval, TimeUnit unit);
+
+	interface Cancellable {
+
+		/**
+		 * Cancels the task if it has not already started running. If the task
+		 * is {@link #scheduleWithFixedDelay(Runnable, Executor, long, long, TimeUnit) periodic},
+		 * all future executions of the task are cancelled.
+		 */
+		void cancel();
+	}
+}

bramble-api/src/main/java/org/briarproject/bramble/api/system/Wakeful.java

@@ -0,0 +1,19 @@
+package org.briarproject.bramble.api.system;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.Target;
+
+import javax.inject.Qualifier;
+
+import static java.lang.annotation.ElementType.METHOD;
+import static java.lang.annotation.RetentionPolicy.RUNTIME;
+
+/**
+ * Annotation for methods that must be called while holding a wake lock, if
+ * the platform supports wake locks.
+ */
+@Qualifier
+@Target(METHOD)
+@Retention(RUNTIME)
+public @interface Wakeful {
+}

bramble-api/src/main/java/org/briarproject/bramble/api/system/WakefulIoExecutor.java

@@ -0,0 +1,26 @@
+package org.briarproject.bramble.api.system;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.Target;
+
+import javax.inject.Qualifier;
+
+import static java.lang.annotation.ElementType.FIELD;
+import static java.lang.annotation.ElementType.METHOD;
+import static java.lang.annotation.ElementType.PARAMETER;
+import static java.lang.annotation.RetentionPolicy.RUNTIME;
+
+/**
+ * Annotation for injecting the executor for long-running IO tasks that should
+ * run without sleeping. Also used for annotating methods that should run on
+ * this executor.
+ * <p>
+ * The contract of this executor is that tasks may be run concurrently, and
+ * submitting a task will never block. Tasks must not run indefinitely. Tasks
+ * submitted during shutdown are discarded.
+ */
+@Qualifier
+@Target({FIELD, METHOD, PARAMETER})
+@Retention(RUNTIME)
+public @interface WakefulIoExecutor {
+}

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

@@ -9,7 +9,6 @@ import org.briarproject.bramble.plugin.PluginModule;
 import org.briarproject.bramble.properties.PropertiesModule;
 import org.briarproject.bramble.rendezvous.RendezvousModule;
 import org.briarproject.bramble.sync.validation.ValidationModule;
-import org.briarproject.bramble.system.SystemModule;
 import org.briarproject.bramble.transport.TransportModule;
 import org.briarproject.bramble.versioning.VersioningModule;
 
@@ -31,8 +30,6 @@ public interface BrambleCoreEagerSingletons {
 
 	void inject(RendezvousModule.EagerSingletons init);
 
-	void inject(SystemModule.EagerSingletons init);
-
 	void inject(TransportModule.EagerSingletons init);
 
 	void inject(ValidationModule.EagerSingletons init);
@@ -50,7 +47,6 @@ public interface BrambleCoreEagerSingletons {
 			c.inject(new RendezvousModule.EagerSingletons());
 			c.inject(new PluginModule.EagerSingletons());
 			c.inject(new PropertiesModule.EagerSingletons());
-			c.inject(new SystemModule.EagerSingletons());
 			c.inject(new TransportModule.EagerSingletons());
 			c.inject(new ValidationModule.EagerSingletons());
 			c.inject(new VersioningModule.EagerSingletons());

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

@@ -21,7 +21,7 @@ import org.briarproject.bramble.rendezvous.RendezvousModule;
 import org.briarproject.bramble.settings.SettingsModule;
 import org.briarproject.bramble.sync.SyncModule;
 import org.briarproject.bramble.sync.validation.ValidationModule;
-import org.briarproject.bramble.system.SystemModule;
+import org.briarproject.bramble.system.ClockModule;
 import org.briarproject.bramble.transport.TransportModule;
 import org.briarproject.bramble.versioning.VersioningModule;
 
@@ -29,6 +29,7 @@ import dagger.Module;
 
 @Module(includes = {
 		ClientModule.class,
+		ClockModule.class,
 		ConnectionModule.class,
 		ContactModule.class,
 		CryptoModule.class,
@@ -48,7 +49,6 @@ import dagger.Module;
 		RendezvousModule.class,
 		SettingsModule.class,
 		SyncModule.class,
-		SystemModule.class,
 		TransportModule.class,
 		ValidationModule.class,
 		VersioningModule.class

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

@@ -179,8 +179,9 @@ class AccountManagerImpl implements AccountManager {
 	@GuardedBy("stateChangeLock")
 	private boolean encryptAndStoreDatabaseKey(SecretKey key, String password) {
 		byte[] plaintext = key.getBytes();
-		byte[] ciphertext = crypto.encryptWithPassword(plaintext, password,
-				databaseConfig.getKeyStrengthener());
+		// Don't use a key strengthener as the Android keymaster isn't reliable
+		byte[] ciphertext =
+				crypto.encryptWithPassword(plaintext, password, null);
 		return storeEncryptedDatabaseKey(toHexString(ciphertext));
 	}
 
@@ -197,13 +198,13 @@ class AccountManagerImpl implements AccountManager {
 	@Override
 	public void signIn(String password) throws DecryptionException {
 		synchronized (stateChangeLock) {
-			databaseKey = loadAndDecryptDatabaseKey(password);
+			databaseKey = loadAndDecryptDatabaseKey(password, false);
 		}
 	}
 
 	@GuardedBy("stateChangeLock")
-	private SecretKey loadAndDecryptDatabaseKey(String password)
-			throws DecryptionException {
+	private SecretKey loadAndDecryptDatabaseKey(String password,
+			boolean changing) throws DecryptionException {
 		String hex = loadEncryptedDatabaseKey();
 		if (hex == null) {
 			LOG.warning("Failed to load encrypted database key");
@@ -214,11 +215,11 @@ class AccountManagerImpl implements AccountManager {
 		byte[] plaintext = crypto.decryptWithPassword(ciphertext, password,
 				keyStrengthener);
 		SecretKey key = new SecretKey(plaintext);
-		// If the DB key was encrypted with a weak key and a key strengthener
-		// is now available, re-encrypt the DB key with a strengthened key
-		if (keyStrengthener != null &&
-				!crypto.isEncryptedWithStrengthenedKey(ciphertext)) {
-			LOG.info("Re-encrypting database key with strengthened key");
+		// If the DB key was encrypted with a hardware-backed key, re-encrypt
+		// it without the hardware-backed key so keymaster bugs don't delete
+		// the user's account
+		if (!changing && crypto.isEncryptedWithStrengthenedKey(ciphertext)) {
+			LOG.info("Re-encrypting database key without strengthened key");
 			encryptAndStoreDatabaseKey(key, password);
 		}
 		return key;
@@ -228,7 +229,7 @@ class AccountManagerImpl implements AccountManager {
 	public void changePassword(String oldPassword, String newPassword)
 			throws DecryptionException {
 		synchronized (stateChangeLock) {
-			SecretKey key = loadAndDecryptDatabaseKey(oldPassword);
+			SecretKey key = loadAndDecryptDatabaseKey(oldPassword, true);
 			encryptAndStoreDatabaseKey(key, newPassword);
 		}
 	}

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

@@ -3,15 +3,15 @@ package org.briarproject.bramble.io;
 import org.briarproject.bramble.api.io.TimeoutMonitor;
 import org.briarproject.bramble.api.lifecycle.IoExecutor;
 import org.briarproject.bramble.api.system.Clock;
-import org.briarproject.bramble.api.system.Scheduler;
+import org.briarproject.bramble.api.system.TaskScheduler;
+import org.briarproject.bramble.api.system.TaskScheduler.Cancellable;
+import org.briarproject.bramble.api.system.Wakeful;
 
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.concurrent.Executor;
-import java.util.concurrent.Future;
-import java.util.concurrent.ScheduledExecutorService;
 import java.util.logging.Logger;
 
 import javax.annotation.concurrent.GuardedBy;
@@ -30,7 +30,7 @@ class TimeoutMonitorImpl implements TimeoutMonitor {
 
 	private static final long CHECK_INTERVAL_MS = SECONDS.toMillis(10);
 
-	private final ScheduledExecutorService scheduler;
+	private final TaskScheduler scheduler;
 	private final Executor ioExecutor;
 	private final Clock clock;
 	private final Object lock = new Object();
@@ -38,10 +38,10 @@ class TimeoutMonitorImpl implements TimeoutMonitor {
 	private final List<TimeoutInputStream> streams = new ArrayList<>();
 
 	@GuardedBy("lock")
-	private Future<?> task = null;
+	private Cancellable cancellable = null;
 
 	@Inject
-	TimeoutMonitorImpl(@Scheduler ScheduledExecutorService scheduler,
+	TimeoutMonitorImpl(TaskScheduler scheduler,
 			@IoExecutor Executor ioExecutor, Clock clock) {
 		this.scheduler = scheduler;
 		this.ioExecutor = ioExecutor;
@@ -55,8 +55,9 @@ class TimeoutMonitorImpl implements TimeoutMonitor {
 				timeoutMs, this::removeStream);
 		synchronized (lock) {
 			if (streams.isEmpty()) {
-				task = scheduler.scheduleWithFixedDelay(this::checkTimeouts,
-						CHECK_INTERVAL_MS, CHECK_INTERVAL_MS, MILLISECONDS);
+				cancellable = scheduler.scheduleWithFixedDelay(
+						this::checkTimeouts, ioExecutor, CHECK_INTERVAL_MS,
+						CHECK_INTERVAL_MS, MILLISECONDS);
 			}
 			streams.add(stream);
 		}
@@ -64,33 +65,35 @@ class TimeoutMonitorImpl implements TimeoutMonitor {
 	}
 
 	private void removeStream(TimeoutInputStream stream) {
-		Future<?> toCancel = null;
+		Cancellable toCancel = null;
 		synchronized (lock) {
 			if (streams.remove(stream) && streams.isEmpty()) {
-				toCancel = task;
-				task = null;
+				toCancel = cancellable;
+				cancellable = null;
 			}
 		}
-		if (toCancel != null) toCancel.cancel(false);
+		if (toCancel != null) {
+			LOG.info("Cancelling timeout monitor task");
+			toCancel.cancel();
+		}
 	}
 
-	@Scheduler
+	@IoExecutor
+	@Wakeful
 	private void checkTimeouts() {
-		ioExecutor.execute(() -> {
-			List<TimeoutInputStream> snapshot;
-			synchronized (lock) {
-				snapshot = new ArrayList<>(streams);
-			}
-			for (TimeoutInputStream stream : snapshot) {
-				if (stream.hasTimedOut()) {
-					LOG.info("Input stream has timed out");
-					try {
-						stream.close();
-					} catch (IOException e) {
-						logException(LOG, INFO, e);
-					}
+		List<TimeoutInputStream> snapshot;
+		synchronized (lock) {
+			snapshot = new ArrayList<>(streams);
+		}
+		for (TimeoutInputStream stream : snapshot) {
+			if (stream.hasTimedOut()) {
+				LOG.info("Input stream has timed out");
+				try {
+					stream.close();
+				} catch (IOException e) {
+					logException(LOG, INFO, e);
 				}
 			}
-		});
+		}
 	}
 }

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

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

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

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

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

@@ -1,6 +1,7 @@
 package org.briarproject.bramble.plugin;
 
 import org.briarproject.bramble.api.connection.ConnectionManager;
+import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.lifecycle.IoExecutor;
@@ -28,6 +29,7 @@ import org.briarproject.bramble.api.properties.TransportProperties;
 import org.briarproject.bramble.api.properties.TransportPropertyManager;
 import org.briarproject.bramble.api.settings.Settings;
 import org.briarproject.bramble.api.settings.SettingsManager;
+import org.briarproject.bramble.api.system.WakefulIoExecutor;
 
 import java.util.ArrayList;
 import java.util.Collection;
@@ -44,6 +46,7 @@ import java.util.logging.Logger;
 import javax.annotation.concurrent.ThreadSafe;
 import javax.inject.Inject;
 
+import static java.util.Collections.emptyList;
 import static java.util.logging.Level.FINE;
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
@@ -62,7 +65,7 @@ class PluginManagerImpl implements PluginManager, Service {
 	private static final Logger LOG =
 			getLogger(PluginManagerImpl.class.getName());
 
-	private final Executor ioExecutor;
+	private final Executor ioExecutor, wakefulIoExecutor;
 	private final EventBus eventBus;
 	private final PluginConfig pluginConfig;
 	private final ConnectionManager connectionManager;
@@ -75,11 +78,15 @@ class PluginManagerImpl implements PluginManager, Service {
 	private final AtomicBoolean used = new AtomicBoolean(false);
 
 	@Inject
-	PluginManagerImpl(@IoExecutor Executor ioExecutor, EventBus eventBus,
-			PluginConfig pluginConfig, ConnectionManager connectionManager,
+	PluginManagerImpl(@IoExecutor Executor ioExecutor,
+			@WakefulIoExecutor Executor wakefulIoExecutor,
+			EventBus eventBus,
+			PluginConfig pluginConfig,
+			ConnectionManager connectionManager,
 			SettingsManager settingsManager,
 			TransportPropertyManager transportPropertyManager) {
 		this.ioExecutor = ioExecutor;
+		this.wakefulIoExecutor = wakefulIoExecutor;
 		this.eventBus = eventBus;
 		this.pluginConfig = pluginConfig;
 		this.connectionManager = connectionManager;
@@ -107,7 +114,7 @@ class PluginManagerImpl implements PluginManager, Service {
 				simplexPlugins.add(s);
 				CountDownLatch startLatch = new CountDownLatch(1);
 				startLatches.put(t, startLatch);
-				ioExecutor.execute(new PluginStarter(s, startLatch));
+				wakefulIoExecutor.execute(new PluginStarter(s, startLatch));
 			}
 		}
 		// Instantiate the duplex plugins and start them asynchronously
@@ -123,7 +130,7 @@ class PluginManagerImpl implements PluginManager, Service {
 				duplexPlugins.add(d);
 				CountDownLatch startLatch = new CountDownLatch(1);
 				startLatches.put(t, startLatch);
-				ioExecutor.execute(new PluginStarter(d, startLatch));
+				wakefulIoExecutor.execute(new PluginStarter(d, startLatch));
 			}
 		}
 	}
@@ -135,12 +142,16 @@ class PluginManagerImpl implements PluginManager, Service {
 		LOG.info("Stopping simplex plugins");
 		for (SimplexPlugin s : simplexPlugins) {
 			CountDownLatch startLatch = startLatches.get(s.getId());
+			// Don't need the wakeful executor here as we wait for the plugin
+			// to stop before returning
 			ioExecutor.execute(new PluginStopper(s, startLatch, stopLatch));
 		}
 		// Stop the duplex plugins
 		LOG.info("Stopping duplex plugins");
 		for (DuplexPlugin d : duplexPlugins) {
 			CountDownLatch startLatch = startLatches.get(d.getId());
+			// Don't need the wakeful executor here as we wait for the plugin
+			// to stop before returning
 			ioExecutor.execute(new PluginStopper(d, startLatch, stopLatch));
 		}
 		// Wait for all the plugins to stop
@@ -203,7 +214,7 @@ class PluginManagerImpl implements PluginManager, Service {
 		}
 	}
 
-	private class PluginStarter implements Runnable {
+	private static class PluginStarter implements Runnable {
 
 		private final Plugin plugin;
 		private final CountDownLatch startLatch;
@@ -233,7 +244,7 @@ class PluginManagerImpl implements PluginManager, Service {
 		}
 	}
 
-	private class PluginStopper implements Runnable {
+	private static class PluginStopper implements Runnable {
 
 		private final Plugin plugin;
 		private final CountDownLatch startLatch, stopLatch;
@@ -303,6 +314,18 @@ class PluginManagerImpl implements PluginManager, Service {
 			}
 		}
 
+		@Override
+		public Collection<TransportProperties> getRemoteProperties() {
+			try {
+				Map<ContactId, TransportProperties> remote =
+						transportPropertyManager.getRemoteProperties(id);
+				return remote.values();
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+				return emptyList();
+			}
+		}
+
 		@Override
 		public void mergeSettings(Settings s) {
 			PluginManagerImpl.this.mergeSettings(s, id.getString());

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

@@ -19,13 +19,17 @@ import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
 import org.briarproject.bramble.api.plugin.event.ConnectionClosedEvent;
+import org.briarproject.bramble.api.plugin.event.ConnectionOpenedEvent;
 import org.briarproject.bramble.api.plugin.event.TransportActiveEvent;
 import org.briarproject.bramble.api.plugin.event.TransportInactiveEvent;
 import org.briarproject.bramble.api.plugin.simplex.SimplexPlugin;
 import org.briarproject.bramble.api.properties.TransportProperties;
 import org.briarproject.bramble.api.properties.TransportPropertyManager;
 import org.briarproject.bramble.api.system.Clock;
-import org.briarproject.bramble.api.system.Scheduler;
+import org.briarproject.bramble.api.system.TaskScheduler;
+import org.briarproject.bramble.api.system.TaskScheduler.Cancellable;
+import org.briarproject.bramble.api.system.Wakeful;
+import org.briarproject.bramble.api.system.WakefulIoExecutor;
 
 import java.security.SecureRandom;
 import java.util.ArrayList;
@@ -34,8 +38,6 @@ import java.util.HashMap;
 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.concurrent.Executor;
-import java.util.concurrent.Future;
-import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.locks.Lock;
 import java.util.concurrent.locks.ReentrantLock;
 import java.util.logging.Logger;
@@ -56,8 +58,8 @@ class PollerImpl implements Poller, EventListener {
 
 	private static final Logger LOG = getLogger(PollerImpl.class.getName());
 
-	private final Executor ioExecutor;
-	private final ScheduledExecutorService scheduler;
+	private final Executor ioExecutor, wakefulIoExecutor;
+	private final TaskScheduler scheduler;
 	private final ConnectionManager connectionManager;
 	private final ConnectionRegistry connectionRegistry;
 	private final PluginManager pluginManager;
@@ -70,12 +72,16 @@ class PollerImpl implements Poller, EventListener {
 
 	@Inject
 	PollerImpl(@IoExecutor Executor ioExecutor,
-			@Scheduler ScheduledExecutorService scheduler,
+			@WakefulIoExecutor Executor wakefulIoExecutor,
+			TaskScheduler scheduler,
 			ConnectionManager connectionManager,
-			ConnectionRegistry connectionRegistry, PluginManager pluginManager,
+			ConnectionRegistry connectionRegistry,
+			PluginManager pluginManager,
 			TransportPropertyManager transportPropertyManager,
-			SecureRandom random, Clock clock) {
+			SecureRandom random,
+			Clock clock) {
 		this.ioExecutor = ioExecutor;
+		this.wakefulIoExecutor = wakefulIoExecutor;
 		this.scheduler = scheduler;
 		this.connectionManager = connectionManager;
 		this.connectionRegistry = connectionRegistry;
@@ -95,10 +101,16 @@ 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 ConnectionOpenedEvent) {
+			ConnectionOpenedEvent c = (ConnectionOpenedEvent) e;
+			// Reschedule polling, the polling interval may have decreased
+			reschedule(c.getTransportId());
 		} else if (e instanceof TransportActiveEvent) {
 			TransportActiveEvent t = (TransportActiveEvent) e;
 			// Poll the newly activated transport
@@ -126,7 +138,7 @@ class PollerImpl implements Poller, EventListener {
 	}
 
 	private void connectToContact(ContactId c, SimplexPlugin p) {
-		ioExecutor.execute(() -> {
+		wakefulIoExecutor.execute(() -> {
 			TransportId t = p.getId();
 			if (connectionRegistry.isConnected(c, t)) return;
 			try {
@@ -142,7 +154,7 @@ class PollerImpl implements Poller, EventListener {
 	}
 
 	private void connectToContact(ContactId c, DuplexPlugin p) {
-		ioExecutor.execute(() -> {
+		wakefulIoExecutor.execute(() -> {
 			TransportId t = p.getId();
 			if (connectionRegistry.isConnected(c, t)) return;
 			try {
@@ -157,6 +169,12 @@ 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
@@ -173,11 +191,11 @@ class PollerImpl implements Poller, EventListener {
 			if (scheduled == null || due < scheduled.task.due) {
 				// If a later task exists, cancel it. If it's already started
 				// it will abort safely when it finds it's been replaced
-				if (scheduled != null) scheduled.future.cancel(false);
+				if (scheduled != null) scheduled.cancellable.cancel();
 				PollTask task = new PollTask(p, due, randomiseNext);
-				Future future = scheduler.schedule(() ->
-						ioExecutor.execute(task), delay, MILLISECONDS);
-				tasks.put(t, new ScheduledPollTask(task, future));
+				Cancellable cancellable = scheduler.schedule(task, ioExecutor,
+						delay, MILLISECONDS);
+				tasks.put(t, new ScheduledPollTask(task, cancellable));
 			}
 		} finally {
 			lock.unlock();
@@ -188,7 +206,7 @@ class PollerImpl implements Poller, EventListener {
 		lock.lock();
 		try {
 			ScheduledPollTask scheduled = tasks.remove(t);
-			if (scheduled != null) scheduled.future.cancel(false);
+			if (scheduled != null) scheduled.cancellable.cancel();
 		} finally {
 			lock.unlock();
 		}
@@ -219,11 +237,11 @@ class PollerImpl implements Poller, EventListener {
 	private class ScheduledPollTask {
 
 		private final PollTask task;
-		private final Future future;
+		private final Cancellable cancellable;
 
-		private ScheduledPollTask(PollTask task, Future future) {
+		private ScheduledPollTask(PollTask task, Cancellable cancellable) {
 			this.task = task;
-			this.future = future;
+			this.cancellable = cancellable;
 		}
 	}
 
@@ -241,6 +259,7 @@ class PollerImpl implements Poller, EventListener {
 
 		@Override
 		@IoExecutor
+		@Wakeful
 		public void run() {
 			lock.lock();
 			try {

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

@@ -0,0 +1,14 @@
+package org.briarproject.bramble.plugin.bluetooth;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
+import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
+
+import java.io.IOException;
+
+@NotNullByDefault
+interface BluetoothConnectionFactory<S> {
+
+	DuplexTransportConnection wrapSocket(DuplexPlugin plugin, S socket)
+			throws IOException;
+}

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

@@ -1,11 +1,11 @@
 package org.briarproject.bramble.plugin.bluetooth;
 
 import org.briarproject.bramble.api.FormatException;
+import org.briarproject.bramble.api.Multiset;
 import org.briarproject.bramble.api.Pair;
 import org.briarproject.bramble.api.data.BdfList;
 import org.briarproject.bramble.api.event.Event;
 import org.briarproject.bramble.api.event.EventListener;
-import org.briarproject.bramble.api.io.TimeoutMonitor;
 import org.briarproject.bramble.api.keyagreement.KeyAgreementConnection;
 import org.briarproject.bramble.api.keyagreement.KeyAgreementListener;
 import org.briarproject.bramble.api.keyagreement.event.KeyAgreementListeningEvent;
@@ -14,6 +14,7 @@ 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;
@@ -24,6 +25,7 @@ import org.briarproject.bramble.api.plugin.event.BluetoothEnabledEvent;
 import org.briarproject.bramble.api.plugin.event.DisableBluetoothEvent;
 import org.briarproject.bramble.api.plugin.event.EnableBluetoothEvent;
 import org.briarproject.bramble.api.properties.TransportProperties;
+import org.briarproject.bramble.api.properties.event.RemoteTransportPropertiesUpdatedEvent;
 import org.briarproject.bramble.api.rendezvous.KeyMaterialSource;
 import org.briarproject.bramble.api.rendezvous.RendezvousEndpoint;
 import org.briarproject.bramble.api.settings.Settings;
@@ -45,8 +47,12 @@ 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_ADDRESS_IS_REFLECTED;
+import static org.briarproject.bramble.api.plugin.BluetoothConstants.DEFAULT_PREF_EVER_CONNECTED;
 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_ADDRESS_IS_REFLECTED;
+import static org.briarproject.bramble.api.plugin.BluetoothConstants.PREF_EVER_CONNECTED;
 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;
@@ -54,6 +60,7 @@ 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.api.properties.TransportPropertyConstants.REFLECTED_PROPERTY_PREFIX;
 import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.bramble.util.PrivacyUtils.scrubMacAddress;
 import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
@@ -62,19 +69,21 @@ import static org.briarproject.bramble.util.StringUtils.macToString;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
-abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
+abstract class BluetoothPlugin<S, SS> implements DuplexPlugin, EventListener {
 
 	private static final Logger LOG =
 			getLogger(BluetoothPlugin.class.getName());
 
 	final BluetoothConnectionLimiter connectionLimiter;
-	final TimeoutMonitor timeoutMonitor;
+	final BluetoothConnectionFactory<S> connectionFactory;
 
-	private final Executor ioExecutor;
+	private final Executor ioExecutor, wakefulIoExecutor;
 	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);
+	private final AtomicBoolean everConnected = new AtomicBoolean(false);
 
 	protected final PluginState state = new PluginState();
 
@@ -113,17 +122,23 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 	abstract DuplexTransportConnection discoverAndConnect(String uuid);
 
 	BluetoothPlugin(BluetoothConnectionLimiter connectionLimiter,
-			TimeoutMonitor timeoutMonitor, Executor ioExecutor,
-			SecureRandom secureRandom, PluginCallback callback, int maxLatency, int maxIdleTime,
-			int pollingInterval) {
+			BluetoothConnectionFactory<S> connectionFactory,
+			Executor ioExecutor,
+			Executor wakefulIoExecutor,
+			SecureRandom secureRandom,
+			Backoff backoff,
+			PluginCallback callback,
+			int maxLatency,
+			int maxIdleTime) {
 		this.connectionLimiter = connectionLimiter;
-		this.timeoutMonitor = timeoutMonitor;
+		this.connectionFactory = connectionFactory;
 		this.ioExecutor = ioExecutor;
+		this.wakefulIoExecutor = wakefulIoExecutor;
 		this.secureRandom = secureRandom;
+		this.backoff = backoff;
 		this.callback = callback;
 		this.maxLatency = maxLatency;
 		this.maxIdleTime = maxIdleTime;
-		this.pollingInterval = pollingInterval;
 	}
 
 	void onAdapterEnabled() {
@@ -165,6 +180,8 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 		Settings settings = callback.getSettings();
 		boolean enabledByUser = settings.getBoolean(PREF_PLUGIN_ENABLE,
 				DEFAULT_PREF_PLUGIN_ENABLE);
+		everConnected.set(settings.getBoolean(PREF_EVER_CONNECTED,
+				DEFAULT_PREF_EVER_CONNECTED));
 		state.setStarted(enabledByUser);
 		try {
 			initialiseAdapter();
@@ -194,6 +211,7 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 				tryToClose(ss);
 				return;
 			}
+			backoff.reset();
 			acceptContactConnections(ss);
 		});
 	}
@@ -202,25 +220,68 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 		TransportProperties p = callback.getLocalProperties();
 		String address = p.get(PROP_ADDRESS);
 		String uuid = p.get(PROP_UUID);
+		Settings s = callback.getSettings();
+		boolean isReflected = s.getBoolean(PREF_ADDRESS_IS_REFLECTED,
+				DEFAULT_PREF_ADDRESS_IS_REFLECTED);
 		boolean changed = false;
-		if (address == null) {
+		if (address == null || isReflected) {
 			address = getBluetoothAddress();
-			if (LOG.isLoggable(INFO))
+			if (LOG.isLoggable(INFO)) {
 				LOG.info("Local address " + scrubMacAddress(address));
-			if (!isNullOrEmpty(address)) {
-				p.put(PROP_ADDRESS, address);
+			}
+			if (address == null) {
+				if (everConnected.get()) {
+					address = getReflectedAddress();
+					if (LOG.isLoggable(INFO)) {
+						LOG.info("Reflected address " +
+								scrubMacAddress(address));
+					}
+					if (address != null) {
+						changed = true;
+						isReflected = true;
+					}
+				}
+			} else {
 				changed = true;
+				isReflected = false;
 			}
 		}
 		if (uuid == null) {
 			byte[] random = new byte[UUID_BYTES];
 			secureRandom.nextBytes(random);
 			uuid = UUID.nameUUIDFromBytes(random).toString();
-			p.put(PROP_UUID, uuid);
 			changed = true;
 		}
 		contactConnectionsUuid = uuid;
-		if (changed) callback.mergeLocalProperties(p);
+		if (changed) {
+			p = new TransportProperties();
+			// If we previously used a reflected address and there's no longer
+			// a reflected address with enough votes to be used, we'll continue
+			// to use the old reflected address until there's a new winner
+			if (address != null) p.put(PROP_ADDRESS, address);
+			p.put(PROP_UUID, uuid);
+			callback.mergeLocalProperties(p);
+			s = new Settings();
+			s.putBoolean(PREF_ADDRESS_IS_REFLECTED, isReflected);
+			callback.mergeSettings(s);
+		}
+	}
+
+	@Nullable
+	private String getReflectedAddress() {
+		// Count the number of votes for each reflected address
+		String key = REFLECTED_PROPERTY_PREFIX + PROP_ADDRESS;
+		Multiset<String> votes = new Multiset<>();
+		for (TransportProperties p : callback.getRemoteProperties()) {
+			String address = p.get(key);
+			if (address != null && isValidAddress(address)) votes.add(address);
+		}
+		// If an address gets more than half of the votes, accept it
+		int total = votes.getTotal();
+		for (String address : votes.keySet()) {
+			if (votes.getCount(address) * 2 > total) return address;
+		}
+		return null;
 	}
 
 	private void acceptContactConnections(SS ss) {
@@ -236,10 +297,24 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 			}
 			LOG.info("Connection received");
 			connectionLimiter.connectionOpened(conn);
+			backoff.reset();
+			setEverConnected();
 			callback.handleConnection(conn);
 		}
 	}
 
+	private void setEverConnected() {
+		if (!everConnected.getAndSet(true)) {
+			ioExecutor.execute(() -> {
+				Settings s = new Settings();
+				s.putBoolean(PREF_EVER_CONNECTED, true);
+				callback.mergeSettings(s);
+				// Contacts may already have sent a reflected address
+				updateProperties();
+			});
+		}
+	}
+
 	@Override
 	public void stop() {
 		SS ss = state.setStopped();
@@ -264,13 +339,14 @@ 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;
+		backoff.increment();
 		for (Pair<TransportProperties, ConnectionHandler> p : properties) {
 			connect(p.getFirst(), p.getSecond());
 		}
@@ -281,9 +357,13 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 		if (isNullOrEmpty(address)) return;
 		String uuid = p.get(PROP_UUID);
 		if (isNullOrEmpty(uuid)) return;
-		ioExecutor.execute(() -> {
+		wakefulIoExecutor.execute(() -> {
 			DuplexTransportConnection d = createConnection(p);
-			if (d != null) h.handleConnection(d);
+			if (d != null) {
+				backoff.reset();
+				setEverConnected();
+				h.handleConnection(d);
+			}
 		});
 	}
 
@@ -384,7 +464,10 @@ 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.connectionOpened(conn);
+			setEverConnected();
+		}
 		return conn;
 	}
 
@@ -421,6 +504,12 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 			ioExecutor.execute(connectionLimiter::keyAgreementStarted);
 		} else if (e instanceof KeyAgreementStoppedListeningEvent) {
 			ioExecutor.execute(connectionLimiter::keyAgreementEnded);
+		} else if (e instanceof RemoteTransportPropertiesUpdatedEvent) {
+			RemoteTransportPropertiesUpdatedEvent r =
+					(RemoteTransportPropertiesUpdatedEvent) e;
+			if (r.getTransportId().equals(ID)) {
+				ioExecutor.execute(this::updateProperties);
+			}
 		}
 	}
 

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

@@ -5,6 +5,7 @@ import org.briarproject.bramble.api.data.BdfList;
 import org.briarproject.bramble.api.keyagreement.KeyAgreementConnection;
 import org.briarproject.bramble.api.keyagreement.KeyAgreementListener;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.Backoff;
 import org.briarproject.bramble.api.plugin.PluginCallback;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
@@ -87,10 +88,15 @@ class LanTcpPlugin extends TcpPlugin {
 		}
 	}
 
-	LanTcpPlugin(Executor ioExecutor, PluginCallback callback, int maxLatency,
-			int maxIdleTime, int pollingInterval, int connectionTimeout) {
-		super(ioExecutor, callback, maxLatency, maxIdleTime, pollingInterval,
-				connectionTimeout);
+	LanTcpPlugin(Executor ioExecutor,
+			Executor wakefulIoExecutor,
+			Backoff backoff,
+			PluginCallback callback,
+			int maxLatency,
+			int maxIdleTime,
+			int connectionTimeout) {
+		super(ioExecutor, wakefulIoExecutor, backoff, callback, maxLatency,
+				maxIdleTime, connectionTimeout);
 	}
 
 	@Override
@@ -348,7 +354,7 @@ class LanTcpPlugin extends TcpPlugin {
 				tryToClose(ss, LOG, WARNING);
 			}
 		}
-		if (ss == null) {
+		if (ss == null || !ss.isBound()) {
 			LOG.info("Could not bind server socket for key agreement");
 			return null;
 		}

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

@@ -1,35 +1,47 @@
 package org.briarproject.bramble.plugin.tcp;
 
 import org.briarproject.bramble.api.event.EventBus;
+import org.briarproject.bramble.api.lifecycle.IoExecutor;
 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;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPluginFactory;
+import org.briarproject.bramble.api.system.WakefulIoExecutor;
 
 import java.util.concurrent.Executor;
 
 import javax.annotation.concurrent.Immutable;
+import javax.inject.Inject;
 
-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 Executor ioExecutor, wakefulIoExecutor;
 	private final EventBus eventBus;
+	private final BackoffFactory backoffFactory;
 
-	public LanTcpPluginFactory(Executor ioExecutor, EventBus eventBus) {
+	@Inject
+	public LanTcpPluginFactory(@IoExecutor Executor ioExecutor,
+			@WakefulIoExecutor Executor wakefulIoExecutor,
+			EventBus eventBus,
+			BackoffFactory backoffFactory) {
 		this.ioExecutor = ioExecutor;
+		this.wakefulIoExecutor = wakefulIoExecutor;
 		this.eventBus = eventBus;
+		this.backoffFactory = backoffFactory;
 	}
 
 	@Override
@@ -44,8 +56,10 @@ public class LanTcpPluginFactory implements DuplexPluginFactory {
 
 	@Override
 	public DuplexPlugin createPlugin(PluginCallback callback) {
-		LanTcpPlugin plugin = new LanTcpPlugin(ioExecutor, callback,
-				MAX_LATENCY, MAX_IDLE_TIME, POLLING_INTERVAL,
+		Backoff backoff = backoffFactory.createBackoff(MIN_POLLING_INTERVAL,
+				MAX_POLLING_INTERVAL, BACKOFF_BASE);
+		LanTcpPlugin plugin = new LanTcpPlugin(ioExecutor, wakefulIoExecutor,
+				backoff, callback, MAX_LATENCY, MAX_IDLE_TIME,
 				CONNECTION_TIMEOUT);
 		eventBus.addListener(plugin);
 		return plugin;

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

@@ -10,6 +10,7 @@ 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;
@@ -65,9 +66,10 @@ abstract class TcpPlugin implements DuplexPlugin, EventListener {
 	private static final Pattern DOTTED_QUAD =
 			Pattern.compile("^\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}$");
 
-	protected final Executor ioExecutor, bindExecutor;
+	protected final Executor ioExecutor, wakefulIoExecutor, 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();
@@ -105,13 +107,19 @@ abstract class TcpPlugin implements DuplexPlugin, EventListener {
 	 */
 	protected abstract boolean isEnabledByDefault();
 
-	TcpPlugin(Executor ioExecutor, PluginCallback callback, int maxLatency,
-			int maxIdleTime, int pollingInterval, int connectionTimeout) {
+	TcpPlugin(Executor ioExecutor,
+			Executor wakefulIoExecutor,
+			Backoff backoff,
+			PluginCallback callback,
+			int maxLatency,
+			int maxIdleTime,
+			int connectionTimeout) {
 		this.ioExecutor = ioExecutor;
+		this.wakefulIoExecutor = wakefulIoExecutor;
+		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;
@@ -141,15 +149,21 @@ abstract class TcpPlugin implements DuplexPlugin, EventListener {
 
 	protected void bind() {
 		bindExecutor.execute(() -> {
-			if (getState() != INACTIVE) return;
+			State s = getState();
+			if (s != ACTIVE && s != INACTIVE) return;
 			bind(true);
 			bind(false);
 		});
 	}
 
 	private void bind(boolean ipv4) {
+		ServerSocket old = state.getServerSocket(ipv4);
 		ServerSocket ss = null;
 		for (InetSocketAddress addr : getLocalSocketAddresses(ipv4)) {
+			if (old != null && addr.equals(old.getLocalSocketAddress())) {
+				LOG.info("Server socket already bound");
+				return;
+			}
 			try {
 				ss = new ServerSocket();
 				ss.bind(addr);
@@ -160,7 +174,7 @@ abstract class TcpPlugin implements DuplexPlugin, EventListener {
 				tryToClose(ss, LOG, WARNING);
 			}
 		}
-		if (ss == null) {
+		if (ss == null || !ss.isBound()) {
 			LOG.info("Could not bind server socket");
 			return;
 		}
@@ -169,6 +183,7 @@ abstract class TcpPlugin implements DuplexPlugin, EventListener {
 			tryToClose(ss, LOG, WARNING);
 			return;
 		}
+		backoff.reset();
 		InetSocketAddress local =
 				(InetSocketAddress) ss.getLocalSocketAddress();
 		setLocalSocketAddress(local, ipv4);
@@ -201,6 +216,7 @@ abstract class TcpPlugin implements DuplexPlugin, EventListener {
 				LOG.info("Connection from " +
 						scrubSocketAddress(s.getRemoteSocketAddress()));
 			}
+			backoff.reset();
 			callback.handleConnection(new TcpTransportConnection(this, s));
 		}
 	}
@@ -227,22 +243,26 @@ 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;
+		backoff.increment();
 		for (Pair<TransportProperties, ConnectionHandler> p : properties) {
 			connect(p.getFirst(), p.getSecond());
 		}
 	}
 
 	private void connect(TransportProperties p, ConnectionHandler h) {
-		ioExecutor.execute(() -> {
+		wakefulIoExecutor.execute(() -> {
 			DuplexTransportConnection d = createConnection(p);
-			if (d != null) h.handleConnection(d);
+			if (d != null) {
+				backoff.reset();
+				h.handleConnection(d);
+			}
 		});
 	}
 

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;
@@ -29,11 +30,16 @@ class WanTcpPlugin extends TcpPlugin {
 
 	private volatile MappingResult mappingResult;
 
-	WanTcpPlugin(Executor ioExecutor, PortMapper portMapper,
-			PluginCallback callback, int maxLatency, int maxIdleTime,
-			int pollingInterval, int connectionTimeout) {
-		super(ioExecutor, callback, maxLatency, maxIdleTime, pollingInterval,
-				connectionTimeout);
+	WanTcpPlugin(Executor ioExecutor,
+			Executor wakefulIoExecutor,
+			Backoff backoff,
+			PortMapper portMapper,
+			PluginCallback callback,
+			int maxLatency,
+			int maxIdleTime,
+			int connectionTimeout) {
+		super(ioExecutor, wakefulIoExecutor, backoff, callback, maxLatency,
+				maxIdleTime, connectionTimeout);
 		this.portMapper = portMapper;
 	}
 

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

@@ -1,38 +1,50 @@
 package org.briarproject.bramble.plugin.tcp;
 
 import org.briarproject.bramble.api.event.EventBus;
+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.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;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPluginFactory;
+import org.briarproject.bramble.api.system.WakefulIoExecutor;
 
 import java.util.concurrent.Executor;
 
 import javax.annotation.concurrent.Immutable;
+import javax.inject.Inject;
 
-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 Executor ioExecutor, wakefulIoExecutor;
 	private final EventBus eventBus;
+	private final BackoffFactory backoffFactory;
 	private final ShutdownManager shutdownManager;
 
-	public WanTcpPluginFactory(Executor ioExecutor, EventBus eventBus,
+	@Inject
+	public WanTcpPluginFactory(@IoExecutor Executor ioExecutor,
+			@WakefulIoExecutor Executor wakefulIoExecutor,
+			EventBus eventBus,
+			BackoffFactory backoffFactory,
 			ShutdownManager shutdownManager) {
 		this.ioExecutor = ioExecutor;
+		this.wakefulIoExecutor = wakefulIoExecutor;
 		this.eventBus = eventBus;
+		this.backoffFactory = backoffFactory;
 		this.shutdownManager = shutdownManager;
 	}
 
@@ -48,9 +60,12 @@ public class WanTcpPluginFactory implements DuplexPluginFactory {
 
 	@Override
 	public DuplexPlugin createPlugin(PluginCallback callback) {
-		WanTcpPlugin plugin = new WanTcpPlugin(ioExecutor,
-				new PortMapperImpl(shutdownManager), callback, MAX_LATENCY,
-				MAX_IDLE_TIME, POLLING_INTERVAL, CONNECTION_TIMEOUT);
+		Backoff backoff = backoffFactory.createBackoff(MIN_POLLING_INTERVAL,
+				MAX_POLLING_INTERVAL, BACKOFF_BASE);
+		PortMapper portMapper = new PortMapperImpl(shutdownManager);
+		WanTcpPlugin plugin = new WanTcpPlugin(ioExecutor, wakefulIoExecutor,
+				backoff, portMapper, callback, MAX_LATENCY, MAX_IDLE_TIME,
+				CONNECTION_TIMEOUT);
 		eventBus.addListener(plugin);
 		return plugin;
 	}

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

@@ -17,6 +17,7 @@ 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;
@@ -45,11 +46,9 @@ import java.net.ServerSocket;
 import java.net.Socket;
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Scanner;
-import java.util.Set;
 import java.util.concurrent.Executor;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.logging.Logger;
@@ -110,59 +109,29 @@ 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 Executor ioExecutor, wakefulIoExecutor;
+	private final Executor connectionStatusExecutor;
 	private final NetworkManager networkManager;
 	private final LocationUtils locationUtils;
 	private final SocketFactory torSocketFactory;
 	private final Clock clock;
 	private final BatteryManager batteryManager;
+	private final Backoff backoff;
 	private final TorRendezvousCrypto torRendezvousCrypto;
 	private final PluginCallback callback;
 	private final String architecture;
 	private final CircumventionProvider circumventionProvider;
 	private final ResourceProvider resourceProvider;
 	private final int maxLatency, maxIdleTime, socketTimeout;
-	private final int initialPollingInterval, stablePollingInterval;
 	private final File torDirectory, torFile, geoIpFile, obfs4File, configFile;
 	private final File doneFile, cookieFile;
 	private final AtomicBoolean used = new AtomicBoolean(false);
@@ -177,16 +146,24 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 
 	protected abstract long getLastUpdateTime();
 
-	TorPlugin(Executor ioExecutor, NetworkManager networkManager,
-			LocationUtils locationUtils, SocketFactory torSocketFactory,
-			Clock clock, ResourceProvider resourceProvider,
+	TorPlugin(Executor ioExecutor,
+			Executor wakefulIoExecutor,
+			NetworkManager networkManager,
+			LocationUtils locationUtils,
+			SocketFactory torSocketFactory,
+			Clock clock,
+			ResourceProvider resourceProvider,
 			CircumventionProvider circumventionProvider,
 			BatteryManager batteryManager,
+			Backoff backoff,
 			TorRendezvousCrypto torRendezvousCrypto,
-			PluginCallback callback, String architecture, int maxLatency,
-			int maxIdleTime, int initialPollingInterval,
-			int stablePollingInterval, File torDirectory) {
+			PluginCallback callback,
+			String architecture,
+			int maxLatency,
+			int maxIdleTime,
+			File torDirectory) {
 		this.ioExecutor = ioExecutor;
+		this.wakefulIoExecutor = wakefulIoExecutor;
 		this.networkManager = networkManager;
 		this.locationUtils = locationUtils;
 		this.torSocketFactory = torSocketFactory;
@@ -194,6 +171,7 @@ 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 +180,6 @@ 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");
@@ -468,6 +444,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			callback.mergeSettings(s);
 			// Create a hidden service if necessary
 			ioExecutor.execute(() -> publishHiddenService(localPort));
+			backoff.reset();
 			// Accept incoming hidden service connections from Tor
 			acceptContactConnections(ss);
 		});
@@ -485,7 +462,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		// in the migration period since first publishing it
 		if (!isNullOrEmpty(privKey2)) {
 			long now = clock.currentTimeMillis();
-			long then = v3Created == null ? now : Long.valueOf(v3Created);
+			long then = v3Created == null ? now : Long.parseLong(v3Created);
 			if (now - then >= V3_MIGRATION_PERIOD_MS) retireV2HiddenService();
 			else publishV2HiddenService(port, privKey2);
 		}
@@ -547,15 +524,15 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			LOG.warning("Tor did not return a private key");
 			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));
 		}
-		TransportProperties p = new TransportProperties();
-		p.put(PROP_ONION_V3, onion3);
-		callback.mergeLocalProperties(p);
 		if (privKey == null) {
+			// Publish the hidden service's onion hostname in transport props
+			TransportProperties p = new TransportProperties();
+			p.put(PROP_ONION_V3, onion3);
+			callback.mergeLocalProperties(p);
 			// Save the hidden service's private key for next time
 			Settings s = new Settings();
 			s.put(HS_PRIVATE_KEY_V3, response.get(HS_PRIVKEY));
@@ -577,6 +554,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 				return;
 			}
 			LOG.info("Connection received");
+			backoff.reset();
 			callback.handleConnection(new TorTransportConnection(this, s));
 		}
 	}
@@ -638,28 +616,26 @@ 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;
+		backoff.increment();
 		for (Pair<TransportProperties, ConnectionHandler> p : properties) {
 			connect(p.getFirst(), p.getSecond());
 		}
 	}
 
 	private void connect(TransportProperties p, ConnectionHandler h) {
-		ioExecutor.execute(() -> {
+		wakefulIoExecutor.execute(() -> {
 			DuplexTransportConnection d = createConnection(p);
-			if (d != null) h.handleConnection(d);
+			if (d != null) {
+				backoff.reset();
+				h.handleConnection(d);
+			}
 		});
 	}
 
@@ -789,8 +765,10 @@ 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") &&
+				state.getAndSetCircuitBuilt()) {
 			LOG.info("First circuit built");
+			backoff.reset();
 		}
 	}
 
@@ -800,8 +778,8 @@ 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(),
@@ -822,18 +800,20 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		if (LOG.isLoggable(INFO)) LOG.info(severity + " " + msg);
 		if (severity.equals("NOTICE") && msg.startsWith("Bootstrapped 100%")) {
 			state.setBootstrapped();
+			backoff.reset();
 		}
 	}
 
 	@Override
 	public void unrecognized(String type, String msg) {
 		if (type.equals("HS_DESC") && msg.startsWith("UPLOADED")) {
-			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 (LOG.isLoggable(INFO)) {
+				String[] words = msg.split(" ");
+				if (words.length > 1 && ONION_V3.matcher(words[1]).matches()) {
+					LOG.info("V3 descriptor uploaded");
+				} else {
+					LOG.info("V2 descriptor uploaded");
+				}
 			}
 		}
 	}
@@ -989,12 +969,6 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		@Nullable
 		private ServerSocket serverSocket = null;
 
-		@GuardedBy("this")
-		private final Set<String> orConnections = new HashSet<>();
-
-		@GuardedBy("this")
-		private int descriptorsUploaded = 0;
-
 		synchronized void setStarted() {
 			started = true;
 			callback.pluginStateChanged(getState());
@@ -1028,10 +1002,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		synchronized void enableNetwork(boolean enable) {
 			networkInitialised = true;
 			networkEnabled = enable;
-			if (!enable) {
-				circuitBuilt = false;
-				descriptorsUploaded = 0;
-			}
+			if (!enable) circuitBuilt = false;
 			callback.pluginStateChanged(getState());
 		}
 
@@ -1041,34 +1012,6 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			callback.pluginStateChanged(getState());
 		}
 
-		synchronized void setOrConnectionStatus(String orName, String status) {
-			if (status.equals("CONNECTED")) {
-				if (!orConnections.add(orName)) {
-					LOG.warning("Duplicate OR connection");
-				}
-			} else {
-				orConnections.remove(orName);
-				if (orConnections.isEmpty()) descriptorsUploaded = 0;
-			}
-			if (LOG.isLoggable(INFO)) {
-				LOG.info(orConnections.size() + " OR connections");
-			}
-			callback.pluginStateChanged(getState());
-		}
-
-		// Doesn't affect getState()
-		synchronized void descriptorUploaded() {
-			if (networkEnabled && !orConnections.isEmpty()) {
-				descriptorsUploaded++;
-			} else {
-				LOG.warning("Descriptor was uploaded with no OR connection");
-			}
-		}
-
-		synchronized boolean isDescriptorPublished() {
-			return descriptorsUploaded >= MIN_DESCRIPTORS_UPLOADED;
-		}
-
 		// Doesn't affect getState()
 		synchronized boolean setServerSocket(ServerSocket ss) {
 			if (stopped || serverSocket != null) return false;
@@ -1088,8 +1031,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			if (reasonsDisabled != 0) return DISABLED;
 			if (!networkInitialised) return ENABLING;
 			if (!networkEnabled) return INACTIVE;
-			return bootstrapped && circuitBuilt && !orConnections.isEmpty()
-					? ACTIVE : ENABLING;
+			return bootstrapped && circuitBuilt ? ACTIVE : ENABLING;
 		}
 
 		synchronized int getReasonsDisabled() {

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

@@ -18,6 +18,7 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.properties.TransportProperties;
 import org.briarproject.bramble.api.properties.TransportPropertyManager;
+import org.briarproject.bramble.api.properties.event.RemoteTransportPropertiesUpdatedEvent;
 import org.briarproject.bramble.api.sync.Group;
 import org.briarproject.bramble.api.sync.Group.Visibility;
 import org.briarproject.bramble.api.sync.GroupId;
@@ -42,6 +43,7 @@ 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.api.properties.TransportPropertyConstants.REFLECTED_PROPERTY_PREFIX;
 import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
 
 @Immutable
@@ -129,8 +131,10 @@ class TransportPropertyManagerImpl implements TransportPropertyManager,
 					// We've already received a newer update - delete this one
 					db.deleteMessage(txn, m.getId());
 					db.deleteMessageMetadata(txn, m.getId());
+					return false;
 				}
 			}
+			txn.attach(new RemoteTransportPropertiesUpdatedEvent(t));
 		} catch (FormatException e) {
 			throw new InvalidMessageException(e);
 		}
@@ -153,15 +157,27 @@ class TransportPropertyManagerImpl implements TransportPropertyManager,
 		if (props.isEmpty()) return;
 		try {
 			db.transaction(false, txn -> {
-				Group g = getContactGroup(db.getContact(txn, c));
+				Contact contact = db.getContact(txn, c);
+				Group g = getContactGroup(contact);
 				BdfDictionary meta = clientHelper.getGroupMetadataAsDictionary(
 						txn, g.getId());
 				BdfDictionary discovered =
 						meta.getOptionalDictionary(GROUP_KEY_DISCOVERED);
-				if (discovered == null) discovered = new BdfDictionary();
-				discovered.putAll(props);
-				meta.put(GROUP_KEY_DISCOVERED, discovered);
-				clientHelper.mergeGroupMetadata(txn, g.getId(), meta);
+				BdfDictionary merged;
+				boolean changed;
+				if (discovered == null) {
+					merged = new BdfDictionary(props);
+					changed = true;
+				} else {
+					merged = new BdfDictionary(discovered);
+					merged.putAll(props);
+					changed = !merged.equals(discovered);
+				}
+				if (changed) {
+					meta.put(GROUP_KEY_DISCOVERED, merged);
+					clientHelper.mergeGroupMetadata(txn, g.getId(), meta);
+					updateLocalProperties(txn, contact, t);
+				}
 			});
 		} catch (FormatException e) {
 			throw new DbException(e);
@@ -226,6 +242,24 @@ class TransportPropertyManagerImpl implements TransportPropertyManager,
 		});
 	}
 
+	private void updateLocalProperties(Transaction txn, Contact c,
+			TransportId t) throws DbException {
+		try {
+			TransportProperties local;
+			LatestUpdate latest = findLatest(txn, localGroup.getId(), t, true);
+			if (latest == null) {
+				local = new TransportProperties();
+			} else {
+				BdfList message = clientHelper.getMessageAsList(txn,
+						latest.messageId);
+				local = parseProperties(message);
+			}
+			storeLocalProperties(txn, c, t, local);
+		} catch (FormatException e) {
+			throw new DbException(e);
+		}
+	}
+
 	private TransportProperties getRemoteProperties(Transaction txn, Contact c,
 			TransportId t) throws DbException {
 		Group g = getContactGroup(c);
@@ -298,18 +332,10 @@ class TransportPropertyManagerImpl implements TransportPropertyManager,
 					storeMessage(txn, localGroup.getId(), t, merged, version,
 							true, false);
 					// Delete the previous update, if any
-					if (latest != null)
-						db.removeMessage(txn, latest.messageId);
+					if (latest != null) db.removeMessage(txn, latest.messageId);
 					// Store the merged properties in each contact's group
 					for (Contact c : db.getContacts(txn)) {
-						Group g = getContactGroup(c);
-						latest = findLatest(txn, g.getId(), t, true);
-						version = latest == null ? 1 : latest.version + 1;
-						storeMessage(txn, g.getId(), t, merged, version,
-								true, true);
-						// Delete the previous update, if any
-						if (latest != null)
-							db.removeMessage(txn, latest.messageId);
+						storeLocalProperties(txn, c, t, merged);
 					}
 				}
 			});
@@ -318,6 +344,34 @@ class TransportPropertyManagerImpl implements TransportPropertyManager,
 		}
 	}
 
+	private void storeLocalProperties(Transaction txn, Contact c,
+			TransportId t, TransportProperties p)
+			throws DbException, FormatException {
+		Group g = getContactGroup(c);
+		LatestUpdate latest = findLatest(txn, g.getId(), t, true);
+		long version = latest == null ? 1 : latest.version + 1;
+		// Reflect any remote properties we've discovered
+		BdfDictionary meta = clientHelper.getGroupMetadataAsDictionary(txn,
+				g.getId());
+		BdfDictionary discovered =
+				meta.getOptionalDictionary(GROUP_KEY_DISCOVERED);
+		TransportProperties combined;
+		if (discovered == null) {
+			combined = p;
+		} else {
+			combined = new TransportProperties(p);
+			TransportProperties d = clientHelper
+					.parseAndValidateTransportProperties(discovered);
+			for (Entry<String, String> e : d.entrySet()) {
+				String key = REFLECTED_PROPERTY_PREFIX + e.getKey();
+				combined.put(key, e.getValue());
+			}
+		}
+		storeMessage(txn, g.getId(), t, combined, version, true, true);
+		// Delete the previous update, if any
+		if (latest != null) db.removeMessage(txn, latest.messageId);
+	}
+
 	private Group getContactGroup(Contact c) {
 		return contactGroupFactory.createContactGroup(CLIENT_ID,
 				MAJOR_VERSION, c);

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

@@ -41,7 +41,8 @@ import org.briarproject.bramble.api.rendezvous.event.RendezvousConnectionClosedE
 import org.briarproject.bramble.api.rendezvous.event.RendezvousConnectionOpenedEvent;
 import org.briarproject.bramble.api.rendezvous.event.RendezvousPollEvent;
 import org.briarproject.bramble.api.system.Clock;
-import org.briarproject.bramble.api.system.Scheduler;
+import org.briarproject.bramble.api.system.TaskScheduler;
+import org.briarproject.bramble.api.system.Wakeful;
 
 import java.security.GeneralSecurityException;
 import java.util.ArrayList;
@@ -52,7 +53,6 @@ import java.util.Map;
 import java.util.Map.Entry;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.Executor;
-import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.logging.Logger;
 
@@ -80,7 +80,7 @@ class RendezvousPollerImpl implements RendezvousPoller, Service, EventListener {
 	private static final Logger LOG =
 			getLogger(RendezvousPollerImpl.class.getName());
 
-	private final ScheduledExecutorService scheduler;
+	private final TaskScheduler scheduler;
 	private final DatabaseComponent db;
 	private final IdentityManager identityManager;
 	private final TransportCrypto transportCrypto;
@@ -105,7 +105,7 @@ class RendezvousPollerImpl implements RendezvousPoller, Service, EventListener {
 
 	@Inject
 	RendezvousPollerImpl(@IoExecutor Executor ioExecutor,
-			@Scheduler ScheduledExecutorService scheduler,
+			TaskScheduler scheduler,
 			DatabaseComponent db,
 			IdentityManager identityManager,
 			TransportCrypto transportCrypto,
@@ -144,8 +144,8 @@ class RendezvousPollerImpl implements RendezvousPoller, Service, EventListener {
 		} catch (DbException e) {
 			throw new ServiceException(e);
 		}
-		scheduler.scheduleAtFixedRate(this::poll, POLLING_INTERVAL_MS,
-				POLLING_INTERVAL_MS, MILLISECONDS);
+		scheduler.scheduleWithFixedDelay(this::poll, worker,
+				POLLING_INTERVAL_MS, POLLING_INTERVAL_MS, MILLISECONDS);
 	}
 
 	@EventExecutor
@@ -205,12 +205,11 @@ class RendezvousPollerImpl implements RendezvousPoller, Service, EventListener {
 		return plugin.createRendezvousEndpoint(k, cs.alice, h);
 	}
 
-	@Scheduler
+	// Worker
+	@Wakeful
 	private void poll() {
-		worker.execute(() -> {
-			removeExpiredPendingContacts();
-			for (PluginState ps : pluginStates.values()) poll(ps);
-		});
+		removeExpiredPendingContacts();
+		for (PluginState ps : pluginStates.values()) poll(ps);
 	}
 
 	// Worker
@@ -238,6 +237,7 @@ class RendezvousPollerImpl implements RendezvousPoller, Service, EventListener {
 	}
 
 	// Worker
+	@Wakeful
 	private void poll(PluginState ps) {
 		if (ps.endpoints.isEmpty()) return;
 		TransportId t = ps.plugin.getId();

bramble-core/src/main/java/org/briarproject/bramble/system/ClockModule.java

@@ -0,0 +1,15 @@
+package org.briarproject.bramble.system;
+
+import org.briarproject.bramble.api.system.Clock;
+
+import dagger.Module;
+import dagger.Provides;
+
+@Module
+public class ClockModule {
+
+	@Provides
+	Clock provideClock() {
+		return new SystemClock();
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/system/DefaultTaskSchedulerModule.java

@@ -1,8 +1,7 @@
 package org.briarproject.bramble.system;
 
 import org.briarproject.bramble.api.lifecycle.LifecycleManager;
-import org.briarproject.bramble.api.system.Clock;
-import org.briarproject.bramble.api.system.Scheduler;
+import org.briarproject.bramble.api.system.TaskScheduler;
 
 import java.util.concurrent.RejectedExecutionHandler;
 import java.util.concurrent.ScheduledExecutorService;
@@ -15,34 +14,26 @@ import dagger.Module;
 import dagger.Provides;
 
 @Module
-public class SystemModule {
+public class DefaultTaskSchedulerModule {
 
 	public static class EagerSingletons {
 		@Inject
-		@Scheduler
-		ScheduledExecutorService scheduledExecutorService;
+		TaskScheduler scheduler;
 	}
 
-	private final ScheduledExecutorService scheduler;
+	private final ScheduledExecutorService scheduledExecutorService;
 
-	public SystemModule() {
+	public DefaultTaskSchedulerModule() {
 		// Discard tasks that are submitted during shutdown
 		RejectedExecutionHandler policy =
 				new ScheduledThreadPoolExecutor.DiscardPolicy();
-		scheduler = new ScheduledThreadPoolExecutor(1, policy);
-	}
-
-	@Provides
-	Clock provideClock() {
-		return new SystemClock();
+		scheduledExecutorService = new ScheduledThreadPoolExecutor(1, policy);
 	}
 
 	@Provides
 	@Singleton
-	@Scheduler
-	ScheduledExecutorService provideScheduledExecutorService(
-			LifecycleManager lifecycleManager) {
-		lifecycleManager.registerForShutdown(scheduler);
-		return scheduler;
+	TaskScheduler provideTaskScheduler(LifecycleManager lifecycleManager) {
+		lifecycleManager.registerForShutdown(scheduledExecutorService);
+		return new TaskSchedulerImpl(scheduledExecutorService);
 	}
 }

bramble-core/src/main/java/org/briarproject/bramble/system/DefaultWakefulIoExecutorModule.java

@@ -0,0 +1,23 @@
+package org.briarproject.bramble.system;
+
+import org.briarproject.bramble.api.lifecycle.IoExecutor;
+import org.briarproject.bramble.api.system.WakefulIoExecutor;
+
+import java.util.concurrent.Executor;
+
+import dagger.Module;
+import dagger.Provides;
+
+/**
+ * Provides a default implementation of {@link WakefulIoExecutor} for systems
+ * without wake locks.
+ */
+@Module
+public class DefaultWakefulIoExecutorModule {
+
+	@Provides
+	@WakefulIoExecutor
+	Executor provideWakefulIoExecutor(@IoExecutor Executor ioExecutor) {
+		return ioExecutor;
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/system/TaskSchedulerImpl.java

@@ -0,0 +1,43 @@
+package org.briarproject.bramble.system;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.system.TaskScheduler;
+
+import java.util.concurrent.Executor;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.ScheduledFuture;
+import java.util.concurrent.TimeUnit;
+
+import javax.annotation.concurrent.ThreadSafe;
+
+/**
+ * A {@link TaskScheduler} that uses a {@link ScheduledExecutorService}.
+ */
+@ThreadSafe
+@NotNullByDefault
+class TaskSchedulerImpl implements TaskScheduler {
+
+	private final ScheduledExecutorService scheduledExecutorService;
+
+	TaskSchedulerImpl(ScheduledExecutorService scheduledExecutorService) {
+		this.scheduledExecutorService = scheduledExecutorService;
+	}
+
+	@Override
+	public Cancellable schedule(Runnable task, Executor executor, long delay,
+			TimeUnit unit) {
+		Runnable execute = () -> executor.execute(task);
+		ScheduledFuture<?> future =
+				scheduledExecutorService.schedule(execute, delay, unit);
+		return () -> future.cancel(false);
+	}
+
+	@Override
+	public Cancellable scheduleWithFixedDelay(Runnable task, Executor executor,
+			long delay, long interval, TimeUnit unit) {
+		Runnable execute = () -> executor.execute(task);
+		ScheduledFuture<?> future = scheduledExecutorService.
+				scheduleWithFixedDelay(execute, delay, interval, unit);
+		return () -> future.cancel(false);
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/transport/TransportKeyManagerFactoryImpl.java

@@ -6,10 +6,9 @@ import org.briarproject.bramble.api.db.DatabaseExecutor;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.system.Clock;
-import org.briarproject.bramble.api.system.Scheduler;
+import org.briarproject.bramble.api.system.TaskScheduler;
 
 import java.util.concurrent.Executor;
-import java.util.concurrent.ScheduledExecutorService;
 
 import javax.annotation.concurrent.Immutable;
 import javax.inject.Inject;
@@ -22,14 +21,15 @@ class TransportKeyManagerFactoryImpl implements
 	private final DatabaseComponent db;
 	private final TransportCrypto transportCrypto;
 	private final Executor dbExecutor;
-	private final ScheduledExecutorService scheduler;
+	private final TaskScheduler scheduler;
 	private final Clock clock;
 
 	@Inject
 	TransportKeyManagerFactoryImpl(DatabaseComponent db,
 			TransportCrypto transportCrypto,
 			@DatabaseExecutor Executor dbExecutor,
-			@Scheduler ScheduledExecutorService scheduler, Clock clock) {
+			TaskScheduler scheduler,
+			Clock clock) {
 		this.db = db;
 		this.transportCrypto = transportCrypto;
 		this.dbExecutor = dbExecutor;

bramble-core/src/main/java/org/briarproject/bramble/transport/TransportKeyManagerImpl.java

@@ -6,12 +6,14 @@ import org.briarproject.bramble.api.contact.PendingContactId;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.crypto.TransportCrypto;
 import org.briarproject.bramble.api.db.DatabaseComponent;
+import org.briarproject.bramble.api.db.DatabaseExecutor;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.Transaction;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.system.Clock;
-import org.briarproject.bramble.api.system.Scheduler;
+import org.briarproject.bramble.api.system.TaskScheduler;
+import org.briarproject.bramble.api.system.Wakeful;
 import org.briarproject.bramble.api.transport.KeySetId;
 import org.briarproject.bramble.api.transport.StreamContext;
 import org.briarproject.bramble.api.transport.TransportKeySet;
@@ -24,7 +26,6 @@ import java.util.HashMap;
 import java.util.Iterator;
 import java.util.Map;
 import java.util.concurrent.Executor;
-import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.locks.ReentrantLock;
 import java.util.logging.Logger;
@@ -53,7 +54,7 @@ class TransportKeyManagerImpl implements TransportKeyManager {
 	private final DatabaseComponent db;
 	private final TransportCrypto transportCrypto;
 	private final Executor dbExecutor;
-	private final ScheduledExecutorService scheduler;
+	private final TaskScheduler scheduler;
 	private final Clock clock;
 	private final TransportId transportId;
 	private final long timePeriodLength;
@@ -72,9 +73,12 @@ class TransportKeyManagerImpl implements TransportKeyManager {
 			pendingContactOutContexts = new HashMap<>();
 
 	TransportKeyManagerImpl(DatabaseComponent db,
-			TransportCrypto transportCrypto, Executor dbExecutor,
-			@Scheduler ScheduledExecutorService scheduler, Clock clock,
-			TransportId transportId, long maxLatency) {
+			TransportCrypto transportCrypto,
+			Executor dbExecutor,
+			TaskScheduler scheduler,
+			Clock clock,
+			TransportId transportId,
+			long maxLatency) {
 		this.db = db;
 		this.transportCrypto = transportCrypto;
 		this.dbExecutor = dbExecutor;
@@ -196,17 +200,17 @@ class TransportKeyManagerImpl implements TransportKeyManager {
 
 	private void scheduleKeyUpdate(long now) {
 		long delay = timePeriodLength - now % timePeriodLength;
-		scheduler.schedule((Runnable) this::updateKeys, delay, MILLISECONDS);
+		scheduler.schedule(this::updateKeys, dbExecutor, delay, MILLISECONDS);
 	}
 
+	@DatabaseExecutor
+	@Wakeful
 	private void updateKeys() {
-		dbExecutor.execute(() -> {
-			try {
-				db.transaction(false, this::updateKeys);
-			} catch (DbException e) {
-				logException(LOG, WARNING, e);
-			}
-		});
+		try {
+			db.transaction(false, this::updateKeys);
+		} catch (DbException e) {
+			logException(LOG, WARNING, e);
+		}
 	}
 
 	@Override
@@ -439,6 +443,8 @@ class TransportKeyManagerImpl implements TransportKeyManager {
 		}
 	}
 
+	@DatabaseExecutor
+	@Wakeful
 	private void updateKeys(Transaction txn) throws DbException {
 		long now = clock.currentTimeMillis();
 		lock.lock();

bramble-core/src/test/java/org/briarproject/bramble/BrambleCoreIntegrationTestEagerSingletons.java

@@ -0,0 +1,18 @@
+package org.briarproject.bramble;
+
+import org.briarproject.bramble.system.DefaultTaskSchedulerModule;
+
+public interface BrambleCoreIntegrationTestEagerSingletons
+		extends BrambleCoreEagerSingletons {
+
+	void inject(DefaultTaskSchedulerModule.EagerSingletons init);
+
+	class Helper {
+
+		public static void injectEagerSingletons(
+				BrambleCoreIntegrationTestEagerSingletons c) {
+			BrambleCoreEagerSingletons.Helper.injectEagerSingletons(c);
+			c.inject(new DefaultTaskSchedulerModule.EagerSingletons());
+		}
+	}
+}

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

@@ -134,7 +134,7 @@ public class AccountManagerImplTest extends BrambleMockTestCase {
 					keyStrengthener);
 			will(returnValue(key.getBytes()));
 			oneOf(crypto).isEncryptedWithStrengthenedKey(encryptedKey);
-			will(returnValue(true));
+			will(returnValue(false));
 		}});
 
 		storeDatabaseKey(keyFile, encryptedKeyHex);
@@ -160,9 +160,8 @@ public class AccountManagerImplTest extends BrambleMockTestCase {
 					keyStrengthener);
 			will(returnValue(key.getBytes()));
 			oneOf(crypto).isEncryptedWithStrengthenedKey(encryptedKey);
-			will(returnValue(false));
-			oneOf(crypto).encryptWithPassword(key.getBytes(), password,
-					keyStrengthener);
+			will(returnValue(true));
+			oneOf(crypto).encryptWithPassword(key.getBytes(), password, null);
 			will(returnValue(newEncryptedKey));
 		}});
 
@@ -262,8 +261,7 @@ public class AccountManagerImplTest extends BrambleMockTestCase {
 			oneOf(identityManager).registerIdentity(identity);
 			oneOf(crypto).generateSecretKey();
 			will(returnValue(key));
-			oneOf(crypto).encryptWithPassword(key.getBytes(), password,
-					keyStrengthener);
+			oneOf(crypto).encryptWithPassword(key.getBytes(), password, null);
 			will(returnValue(encryptedKey));
 		}});
 
@@ -323,10 +321,8 @@ public class AccountManagerImplTest extends BrambleMockTestCase {
 			oneOf(crypto).decryptWithPassword(encryptedKey, password,
 					keyStrengthener);
 			will(returnValue(key.getBytes()));
-			oneOf(crypto).isEncryptedWithStrengthenedKey(encryptedKey);
-			will(returnValue(true));
 			oneOf(crypto).encryptWithPassword(key.getBytes(), newPassword,
-					keyStrengthener);
+					null);
 			will(returnValue(newEncryptedKey));
 		}});
 

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

@@ -1,6 +1,6 @@
 package org.briarproject.bramble.contact;
 
-import org.briarproject.bramble.BrambleCoreEagerSingletons;
+import org.briarproject.bramble.BrambleCoreIntegrationTestEagerSingletons;
 import org.briarproject.bramble.api.Pair;
 import org.briarproject.bramble.api.contact.Contact;
 import org.briarproject.bramble.api.contact.ContactManager;
@@ -62,11 +62,13 @@ public class ContactExchangeIntegrationTest extends BrambleTestCase {
 		alice = DaggerContactExchangeIntegrationTestComponent.builder()
 				.testDatabaseConfigModule(
 						new TestDatabaseConfigModule(aliceDir)).build();
-		BrambleCoreEagerSingletons.Helper.injectEagerSingletons(alice);
+		BrambleCoreIntegrationTestEagerSingletons.Helper
+				.injectEagerSingletons(alice);
 		bob = DaggerContactExchangeIntegrationTestComponent.builder()
 				.testDatabaseConfigModule(new TestDatabaseConfigModule(bobDir))
 				.build();
-		BrambleCoreEagerSingletons.Helper.injectEagerSingletons(bob);
+		BrambleCoreIntegrationTestEagerSingletons.Helper
+				.injectEagerSingletons(bob);
 		// Set up the devices and get the identities
 		aliceIdentity = setUp(alice, "Alice");
 		bobIdentity = setUp(bob, "Bob");

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

@@ -1,6 +1,6 @@
 package org.briarproject.bramble.contact;
 
-import org.briarproject.bramble.BrambleCoreEagerSingletons;
+import org.briarproject.bramble.BrambleCoreIntegrationTestEagerSingletons;
 import org.briarproject.bramble.BrambleCoreModule;
 import org.briarproject.bramble.api.connection.ConnectionManager;
 import org.briarproject.bramble.api.contact.ContactExchangeManager;
@@ -23,7 +23,7 @@ import dagger.Component;
 		BrambleCoreModule.class
 })
 interface ContactExchangeIntegrationTestComponent
-		extends BrambleCoreEagerSingletons {
+		extends BrambleCoreIntegrationTestEagerSingletons {
 
 	ConnectionManager getConnectionManager();
 

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/PluginManagerImplTest.java

@@ -109,8 +109,8 @@ public class PluginManagerImplTest extends BrambleTestCase {
 			oneOf(duplexPlugin).stop();
 		}});
 
-		PluginManagerImpl p = new PluginManagerImpl(ioExecutor, eventBus,
-				pluginConfig, connectionManager, settingsManager,
+		PluginManagerImpl p = new PluginManagerImpl(ioExecutor, ioExecutor,
+				eventBus, pluginConfig, connectionManager, settingsManager,
 				transportPropertyManager);
 
 		// Two plugins should be started and stopped

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

@@ -12,12 +12,15 @@ import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
 import org.briarproject.bramble.api.plugin.event.ConnectionClosedEvent;
+import org.briarproject.bramble.api.plugin.event.ConnectionOpenedEvent;
 import org.briarproject.bramble.api.plugin.event.TransportActiveEvent;
 import org.briarproject.bramble.api.plugin.event.TransportInactiveEvent;
 import org.briarproject.bramble.api.plugin.simplex.SimplexPlugin;
 import org.briarproject.bramble.api.properties.TransportProperties;
 import org.briarproject.bramble.api.properties.TransportPropertyManager;
 import org.briarproject.bramble.api.system.Clock;
+import org.briarproject.bramble.api.system.TaskScheduler;
+import org.briarproject.bramble.api.system.TaskScheduler.Cancellable;
 import org.briarproject.bramble.test.BrambleMockTestCase;
 import org.briarproject.bramble.test.ImmediateExecutor;
 import org.briarproject.bramble.test.RunAction;
@@ -29,8 +32,6 @@ import org.junit.Test;
 import java.security.SecureRandom;
 import java.util.List;
 import java.util.concurrent.Executor;
-import java.util.concurrent.ScheduledExecutorService;
-import java.util.concurrent.ScheduledFuture;
 
 import static java.util.Arrays.asList;
 import static java.util.Collections.emptyList;
@@ -44,8 +45,7 @@ import static org.briarproject.bramble.test.TestUtils.getTransportId;
 
 public class PollerImplTest extends BrambleMockTestCase {
 
-	private final ScheduledExecutorService scheduler =
-			context.mock(ScheduledExecutorService.class);
+	private final TaskScheduler scheduler = context.mock(TaskScheduler.class);
 	private final ConnectionManager connectionManager =
 			context.mock(ConnectionManager.class);
 	private final ConnectionRegistry connectionRegistry =
@@ -55,10 +55,11 @@ public class PollerImplTest extends BrambleMockTestCase {
 	private final TransportPropertyManager transportPropertyManager =
 			context.mock(TransportPropertyManager.class);
 	private final Clock clock = context.mock(Clock.class);
-	private final ScheduledFuture future = context.mock(ScheduledFuture.class);
+	private final Cancellable cancellable = context.mock(Cancellable.class);
 	private final SecureRandom random;
 
 	private final Executor ioExecutor = new ImmediateExecutor();
+	private final Executor wakefulIoExecutor = new ImmediateExecutor();
 	private final TransportId transportId = getTransportId();
 	private final ContactId contactId = getContactId();
 	private final TransportProperties properties = new TransportProperties();
@@ -74,9 +75,9 @@ public class PollerImplTest extends BrambleMockTestCase {
 
 	@Before
 	public void setUp() {
-		poller = new PollerImpl(ioExecutor, scheduler, connectionManager,
-				connectionRegistry, pluginManager, transportPropertyManager,
-				random, clock);
+		poller = new PollerImpl(ioExecutor, wakefulIoExecutor, scheduler,
+				connectionManager, connectionRegistry, pluginManager,
+				transportPropertyManager, random, clock);
 	}
 
 	@Test
@@ -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,
@@ -185,31 +189,151 @@ 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 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(ioExecutor), with((long) pollingInterval),
+					with(MILLISECONDS));
+			will(returnValue(cancellable));
+		}});
+
+		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(ioExecutor), with((long) pollingInterval),
+					with(MILLISECONDS));
+			will(returnValue(cancellable));
+			// 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(ioExecutor), with((long) pollingInterval),
+					with(MILLISECONDS));
+			will(returnValue(cancellable));
+			// 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(cancellable).cancel();
+			oneOf(scheduler).schedule(with(any(Runnable.class)),
+					with(ioExecutor), with((long) pollingInterval - 2),
+					with(MILLISECONDS));
+		}});
+
+		poller.eventOccurred(new ConnectionOpenedEvent(contactId, transportId,
+				false));
+		poller.eventOccurred(new ConnectionOpenedEvent(contactId, transportId,
+				false));
+	}
+
 	@Test
 	public void testPollsOnTransportActivated() throws Exception {
 		DuplexPlugin plugin = context.mock(DuplexPlugin.class);
@@ -226,9 +350,9 @@ public class PollerImplTest extends BrambleMockTestCase {
 			// Schedule a polling task immediately
 			oneOf(clock).currentTimeMillis();
 			will(returnValue(now));
-			oneOf(scheduler).schedule(with(any(Runnable.class)), with(0L),
-					with(MILLISECONDS));
-			will(returnValue(future));
+			oneOf(scheduler).schedule(with(any(Runnable.class)),
+					with(ioExecutor), with(0L), with(MILLISECONDS));
+			will(returnValue(cancellable));
 			will(new RunAction());
 			// Running the polling task schedules the next polling task
 			oneOf(plugin).getPollingInterval();
@@ -238,8 +362,9 @@ public class PollerImplTest extends BrambleMockTestCase {
 			oneOf(clock).currentTimeMillis();
 			will(returnValue(now));
 			oneOf(scheduler).schedule(with(any(Runnable.class)),
-					with((long) (pollingInterval * 0.5)), with(MILLISECONDS));
-			will(returnValue(future));
+					with(ioExecutor), with((long) (pollingInterval * 0.5)),
+					with(MILLISECONDS));
+			will(returnValue(cancellable));
 			// Get the transport properties and connected contacts
 			oneOf(transportPropertyManager).getRemoteProperties(transportId);
 			will(returnValue(singletonMap(contactId, properties)));
@@ -269,9 +394,9 @@ public class PollerImplTest extends BrambleMockTestCase {
 			// Schedule a polling task immediately
 			oneOf(clock).currentTimeMillis();
 			will(returnValue(now));
-			oneOf(scheduler).schedule(with(any(Runnable.class)), with(0L),
-					with(MILLISECONDS));
-			will(returnValue(future));
+			oneOf(scheduler).schedule(with(any(Runnable.class)),
+					with(ioExecutor), with(0L), with(MILLISECONDS));
+			will(returnValue(cancellable));
 			will(new RunAction());
 			// Running the polling task schedules the next polling task
 			oneOf(plugin).getPollingInterval();
@@ -281,8 +406,9 @@ public class PollerImplTest extends BrambleMockTestCase {
 			oneOf(clock).currentTimeMillis();
 			will(returnValue(now));
 			oneOf(scheduler).schedule(with(any(Runnable.class)),
-					with((long) (pollingInterval * 0.5)), with(MILLISECONDS));
-			will(returnValue(future));
+					with(ioExecutor), with((long) (pollingInterval * 0.5)),
+					with(MILLISECONDS));
+			will(returnValue(cancellable));
 			// Get the transport properties and connected contacts
 			oneOf(transportPropertyManager).getRemoteProperties(transportId);
 			will(returnValue(singletonMap(contactId, properties)));
@@ -310,17 +436,37 @@ public class PollerImplTest extends BrambleMockTestCase {
 			// Schedule a polling task immediately
 			oneOf(clock).currentTimeMillis();
 			will(returnValue(now));
-			oneOf(scheduler).schedule(with(any(Runnable.class)), with(0L),
-					with(MILLISECONDS));
-			will(returnValue(future));
+			oneOf(scheduler).schedule(with(any(Runnable.class)),
+					with(ioExecutor), with(0L), with(MILLISECONDS));
+			will(returnValue(cancellable));
 			// The plugin is deactivated before the task runs - cancel the task
-			oneOf(future).cancel(false);
+			oneOf(cancellable).cancel();
 		}});
 
 		poller.eventOccurred(new TransportActiveEvent(transportId));
 		poller.eventOccurred(new TransportInactiveEvent(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(ioExecutor), with((long) pollingInterval),
+					with(MILLISECONDS));
+			will(returnValue(cancellable));
+		}});
+	}
+
 	private void expectReconnect(DuplexPlugin plugin,
 			DuplexTransportConnection duplexConnection) throws Exception {
 		context.checking(new Expectations() {{

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

@@ -3,6 +3,7 @@ package org.briarproject.bramble.plugin.tcp;
 import org.briarproject.bramble.api.data.BdfList;
 import org.briarproject.bramble.api.keyagreement.KeyAgreementListener;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.Backoff;
 import org.briarproject.bramble.api.plugin.Plugin.State;
 import org.briarproject.bramble.api.plugin.PluginCallback;
 import org.briarproject.bramble.api.plugin.TransportConnectionReader;
@@ -21,11 +22,13 @@ import java.net.InetSocketAddress;
 import java.net.NetworkInterface;
 import java.net.ServerSocket;
 import java.net.Socket;
+import java.util.Collection;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.atomic.AtomicBoolean;
 
 import static java.net.NetworkInterface.getNetworkInterfaces;
+import static java.util.Collections.emptyList;
 import static java.util.Collections.list;
 import static java.util.concurrent.Executors.newCachedThreadPool;
 import static java.util.concurrent.TimeUnit.SECONDS;
@@ -41,6 +44,7 @@ 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 +53,8 @@ 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, ioExecutor, backoff, callback,
+				0, 0, 1000) {
 			@Override
 			protected boolean canConnectToOwnAddress() {
 				return true;
@@ -318,6 +323,11 @@ public class LanTcpPluginTest extends BrambleTestCase {
 			return local;
 		}
 
+		@Override
+		public Collection<TransportProperties> getRemoteProperties() {
+			return emptyList();
+		}
+
 		@Override
 		public void mergeSettings(Settings s) {
 		}
@@ -345,4 +355,20 @@ 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

@@ -8,11 +8,15 @@ import org.briarproject.bramble.api.data.BdfDictionary;
 import org.briarproject.bramble.api.data.BdfEntry;
 import org.briarproject.bramble.api.data.BdfList;
 import org.briarproject.bramble.api.data.MetadataParser;
+import org.briarproject.bramble.api.db.CommitAction;
 import org.briarproject.bramble.api.db.DatabaseComponent;
+import org.briarproject.bramble.api.db.EventAction;
 import org.briarproject.bramble.api.db.Metadata;
 import org.briarproject.bramble.api.db.Transaction;
+import org.briarproject.bramble.api.event.Event;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.properties.TransportProperties;
+import org.briarproject.bramble.api.properties.event.RemoteTransportPropertiesUpdatedEvent;
 import org.briarproject.bramble.api.sync.Group;
 import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.Message;
@@ -45,6 +49,7 @@ import static org.briarproject.bramble.test.TestUtils.getMessage;
 import static org.briarproject.bramble.test.TestUtils.getRandomId;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
 
 public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 
@@ -59,23 +64,28 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 	private final Clock clock = context.mock(Clock.class);
 
 	private final Group localGroup = getGroup(CLIENT_ID, MAJOR_VERSION);
-	private final BdfDictionary fooPropertiesDict = BdfDictionary.of(
-			new BdfEntry("fooKey1", "fooValue1"),
-			new BdfEntry("fooKey2", "fooValue2")
-	);
-	private final BdfDictionary barPropertiesDict = BdfDictionary.of(
-			new BdfEntry("barKey1", "barValue1"),
-			new BdfEntry("barKey2", "barValue2")
-	);
+	private final BdfDictionary fooPropertiesDict, barPropertiesDict;
+	private final BdfDictionary discoveredPropertiesDict, mergedPropertiesDict;
 	private final TransportProperties fooProperties, barProperties;
+	private final TransportProperties discoveredProperties;
 
-	public TransportPropertyManagerImplTest() throws Exception {
+	public TransportPropertyManagerImplTest() {
 		fooProperties = new TransportProperties();
-		for (String key : fooPropertiesDict.keySet())
-			fooProperties.put(key, fooPropertiesDict.getString(key));
+		fooProperties.put("fooKey1", "fooValue1");
+		fooProperties.put("fooKey2", "fooValue2");
+		fooPropertiesDict = new BdfDictionary(fooProperties);
+
 		barProperties = new TransportProperties();
-		for (String key : barPropertiesDict.keySet())
-			barProperties.put(key, barPropertiesDict.getString(key));
+		barProperties.put("barKey1", "barValue1");
+		barProperties.put("barKey2", "barValue2");
+		barPropertiesDict = new BdfDictionary(barProperties);
+
+		discoveredProperties = new TransportProperties();
+		discoveredProperties.put("fooKey3", "fooValue3");
+		discoveredPropertiesDict = new BdfDictionary(discoveredProperties);
+
+		mergedPropertiesDict = new BdfDictionary(fooProperties);
+		mergedPropertiesDict.put("u:fooKey3", "fooValue3");
 	}
 
 	private TransportPropertyManagerImpl createInstance() {
@@ -221,6 +231,7 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 
 		TransportPropertyManagerImpl t = createInstance();
 		assertFalse(t.incomingMessage(txn, message, meta));
+		assertTrue(hasEvent(txn, RemoteTransportPropertiesUpdatedEvent.class));
 	}
 
 	@Test
@@ -259,6 +270,7 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 
 		TransportPropertyManagerImpl t = createInstance();
 		assertFalse(t.incomingMessage(txn, message, meta));
+		assertTrue(hasEvent(txn, RemoteTransportPropertiesUpdatedEvent.class));
 	}
 
 	@Test
@@ -292,10 +304,12 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 			// The update being delivered (version 3) should be deleted
 			oneOf(db).deleteMessage(txn, message.getId());
 			oneOf(db).deleteMessageMetadata(txn, message.getId());
+			// No event should be broadcast
 		}});
 
 		TransportPropertyManagerImpl t = createInstance();
 		assertFalse(t.incomingMessage(txn, message, meta));
+		assertFalse(hasEvent(txn, RemoteTransportPropertiesUpdatedEvent.class));
 	}
 
 	@Test
@@ -588,6 +602,9 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
 					contactGroup.getId());
 			will(returnValue(emptyMap()));
+			oneOf(clientHelper).getGroupMetadataAsDictionary(txn,
+					contactGroup.getId());
+			will(returnValue(new BdfDictionary()));
 			expectStoreMessage(txn, contactGroup.getId(), "foo",
 					fooPropertiesDict, 1, true, true);
 		}});
@@ -596,6 +613,49 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 		t.mergeLocalProperties(new TransportId("foo"), properties);
 	}
 
+	@Test
+	public void testMergingNewPropertiesCreatesUpdateWithReflectedProperties()
+			throws Exception {
+		Transaction txn = new Transaction(null, false);
+		Contact contact = getContact();
+		Group contactGroup = getGroup(CLIENT_ID, MAJOR_VERSION);
+		BdfDictionary contactGroupMeta = BdfDictionary.of(
+				new BdfEntry(GROUP_KEY_DISCOVERED, discoveredPropertiesDict)
+		);
+
+		context.checking(new DbExpectations() {{
+			oneOf(db).transaction(with(false), withDbRunnable(txn));
+			// There are no existing properties to merge with
+			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
+					localGroup.getId());
+			will(returnValue(emptyMap()));
+			// Store the new properties in the local group, version 1
+			expectStoreMessage(txn, localGroup.getId(), "foo",
+					fooPropertiesDict, 1, true, false);
+			// Store the new properties in each contact's group, version 1
+			oneOf(db).getContacts(txn);
+			will(returnValue(singletonList(contact)));
+			oneOf(contactGroupFactory).createContactGroup(CLIENT_ID,
+					MAJOR_VERSION, contact);
+			will(returnValue(contactGroup));
+			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
+					contactGroup.getId());
+			will(returnValue(emptyMap()));
+			oneOf(clientHelper).getGroupMetadataAsDictionary(txn,
+					contactGroup.getId());
+			will(returnValue(contactGroupMeta));
+			// Reflect discovered properties
+			oneOf(clientHelper).parseAndValidateTransportProperties(
+					discoveredPropertiesDict);
+			will(returnValue(discoveredProperties));
+			expectStoreMessage(txn, contactGroup.getId(), "foo",
+					mergedPropertiesDict, 1, true, true);
+		}});
+
+		TransportPropertyManagerImpl t = createInstance();
+		t.mergeLocalProperties(new TransportId("foo"), fooProperties);
+	}
+
 	@Test
 	public void testMergingUpdatedPropertiesCreatesUpdate() throws Exception {
 		Transaction txn = new Transaction(null, false);
@@ -652,6 +712,9 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
 					contactGroup.getId());
 			will(returnValue(contactGroupMessageMetadata));
+			oneOf(clientHelper).getGroupMetadataAsDictionary(txn,
+					contactGroup.getId());
+			will(returnValue(new BdfDictionary()));
 			expectStoreMessage(txn, contactGroup.getId(), "foo",
 					fooPropertiesDict, 2, true, true);
 			// Delete the previous update
@@ -662,6 +725,75 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 		t.mergeLocalProperties(new TransportId("foo"), properties);
 	}
 
+	@Test
+	public void testMergingUpdatedPropertiesCreatesUpdateWithReflectedProperties()
+			throws Exception {
+		Transaction txn = new Transaction(null, false);
+		Contact contact = getContact();
+		Group contactGroup = getGroup(CLIENT_ID, MAJOR_VERSION);
+		BdfDictionary contactGroupMeta = BdfDictionary.of(
+				new BdfEntry(GROUP_KEY_DISCOVERED, discoveredPropertiesDict)
+		);
+		BdfDictionary oldMetadata = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_TRANSPORT_ID, "foo"),
+				new BdfEntry(MSG_KEY_VERSION, 1),
+				new BdfEntry(MSG_KEY_LOCAL, true)
+		);
+		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");
+		BdfDictionary oldPropertiesDict = BdfDictionary.of(
+				new BdfEntry("fooKey1", "oldFooValue1")
+		);
+		BdfList oldUpdate = BdfList.of("foo", 1, oldPropertiesDict);
+
+		context.checking(new DbExpectations() {{
+			oneOf(db).transaction(with(false), withDbRunnable(txn));
+			// Merge the new properties with the existing properties
+			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
+					localGroup.getId());
+			will(returnValue(localGroupMessageMetadata));
+			oneOf(clientHelper).getMessageAsList(txn, localGroupUpdateId);
+			will(returnValue(oldUpdate));
+			oneOf(clientHelper).parseAndValidateTransportProperties(
+					oldPropertiesDict);
+			will(returnValue(oldProperties));
+			// Store the merged properties in the local group, version 2
+			expectStoreMessage(txn, localGroup.getId(), "foo",
+					fooPropertiesDict, 2, true, false);
+			// Delete the previous update
+			oneOf(db).removeMessage(txn, localGroupUpdateId);
+			// Store the merged properties in each contact's group, version 2
+			oneOf(db).getContacts(txn);
+			will(returnValue(singletonList(contact)));
+			oneOf(contactGroupFactory).createContactGroup(CLIENT_ID,
+					MAJOR_VERSION, contact);
+			will(returnValue(contactGroup));
+			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
+					contactGroup.getId());
+			will(returnValue(contactGroupMessageMetadata));
+			oneOf(clientHelper).getGroupMetadataAsDictionary(txn,
+					contactGroup.getId());
+			will(returnValue(contactGroupMeta));
+			// Reflect discovered properties
+			oneOf(clientHelper).parseAndValidateTransportProperties(
+					discoveredPropertiesDict);
+			will(returnValue(discoveredProperties));
+			expectStoreMessage(txn, contactGroup.getId(), "foo",
+					mergedPropertiesDict, 2, true, true);
+			// Delete the previous update
+			oneOf(db).removeMessage(txn, contactGroupUpdateId);
+		}});
+
+		TransportPropertyManagerImpl t = createInstance();
+		t.mergeLocalProperties(new TransportId("foo"), fooProperties);
+	}
+
 	private void expectGetLocalProperties(Transaction txn) throws Exception {
 		Map<MessageId, BdfDictionary> messageMetadata = new LinkedHashMap<>();
 		// The latest update for transport "foo" should be returned
@@ -719,4 +851,15 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 					false);
 		}});
 	}
+
+	private boolean hasEvent(Transaction txn,
+			Class<? extends Event> eventClass) {
+		for (CommitAction action : txn.getActions()) {
+			if (action instanceof EventAction) {
+				Event event = ((EventAction) action).getEvent();
+				if (eventClass.isInstance(event)) return true;
+			}
+		}
+		return false;
+	}
 }

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

@@ -26,6 +26,7 @@ import org.briarproject.bramble.api.rendezvous.event.RendezvousConnectionClosedE
 import org.briarproject.bramble.api.rendezvous.event.RendezvousConnectionOpenedEvent;
 import org.briarproject.bramble.api.rendezvous.event.RendezvousPollEvent;
 import org.briarproject.bramble.api.system.Clock;
+import org.briarproject.bramble.api.system.TaskScheduler;
 import org.briarproject.bramble.test.BrambleMockTestCase;
 import org.briarproject.bramble.test.CaptureArgumentAction;
 import org.briarproject.bramble.test.DbExpectations;
@@ -37,7 +38,6 @@ import org.junit.Test;
 
 import java.util.Random;
 import java.util.concurrent.Executor;
-import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.atomic.AtomicReference;
 
 import static java.util.Collections.emptyList;
@@ -60,8 +60,7 @@ import static org.briarproject.bramble.test.TestUtils.getTransportProperties;
 
 public class RendezvousPollerImplTest extends BrambleMockTestCase {
 
-	private final ScheduledExecutorService scheduler =
-			context.mock(ScheduledExecutorService.class);
+	private final TaskScheduler scheduler = context.mock(TaskScheduler.class);
 	private final DatabaseComponent db = context.mock(DatabaseComponent.class);
 	private final IdentityManager identityManager =
 			context.mock(IdentityManager.class);
@@ -123,9 +122,9 @@ public class RendezvousPollerImplTest extends BrambleMockTestCase {
 					PendingContactStateChangedEvent.class, e ->
 					e.getPendingContactState() == OFFLINE)));
 			// Capture the poll task
-			oneOf(scheduler).scheduleAtFixedRate(with(any(Runnable.class)),
-					with(POLLING_INTERVAL_MS), with(POLLING_INTERVAL_MS),
-					with(MILLISECONDS));
+			oneOf(scheduler).scheduleWithFixedDelay(with(any(Runnable.class)),
+					with(any(Executor.class)), with(POLLING_INTERVAL_MS),
+					with(POLLING_INTERVAL_MS), with(MILLISECONDS));
 			will(new CaptureArgumentAction<>(capturePollTask, Runnable.class,
 					0));
 		}});
@@ -159,9 +158,9 @@ public class RendezvousPollerImplTest extends BrambleMockTestCase {
 					PendingContactStateChangedEvent.class, e ->
 					e.getPendingContactState() == FAILED)));
 			// Schedule the poll task
-			oneOf(scheduler).scheduleAtFixedRate(with(any(Runnable.class)),
-					with(POLLING_INTERVAL_MS), with(POLLING_INTERVAL_MS),
-					with(MILLISECONDS));
+			oneOf(scheduler).scheduleWithFixedDelay(with(any(Runnable.class)),
+					with(any(Executor.class)), with(POLLING_INTERVAL_MS),
+					with(POLLING_INTERVAL_MS), with(MILLISECONDS));
 		}});
 
 		rendezvousPoller.startService();
@@ -468,9 +467,9 @@ public class RendezvousPollerImplTest extends BrambleMockTestCase {
 			oneOf(db).getPendingContacts(txn);
 			will(returnValue(emptyList()));
 			// Capture the poll task
-			oneOf(scheduler).scheduleAtFixedRate(with(any(Runnable.class)),
-					with(POLLING_INTERVAL_MS), with(POLLING_INTERVAL_MS),
-					with(MILLISECONDS));
+			oneOf(scheduler).scheduleWithFixedDelay(with(any(Runnable.class)),
+					with(any(Executor.class)), with(POLLING_INTERVAL_MS),
+					with(POLLING_INTERVAL_MS), with(MILLISECONDS));
 			will(new CaptureArgumentAction<>(capturePollTask, Runnable.class,
 					0));
 		}});
@@ -545,9 +544,9 @@ public class RendezvousPollerImplTest extends BrambleMockTestCase {
 					PendingContactStateChangedEvent.class, e ->
 					e.getPendingContactState() == OFFLINE)));
 			// Capture the poll task
-			oneOf(scheduler).scheduleAtFixedRate(with(any(Runnable.class)),
-					with(POLLING_INTERVAL_MS), with(POLLING_INTERVAL_MS),
-					with(MILLISECONDS));
+			oneOf(scheduler).scheduleWithFixedDelay(with(any(Runnable.class)),
+					with(any(Executor.class)), with(POLLING_INTERVAL_MS),
+					with(POLLING_INTERVAL_MS), with(MILLISECONDS));
 			will(new CaptureArgumentAction<>(capturePollTask, Runnable.class,
 					0));
 		}});

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

@@ -1,6 +1,6 @@
 package org.briarproject.bramble.sync;
 
-import org.briarproject.bramble.BrambleCoreEagerSingletons;
+import org.briarproject.bramble.BrambleCoreIntegrationTestEagerSingletons;
 import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.crypto.TransportCrypto;
@@ -73,7 +73,8 @@ public class SyncIntegrationTest extends BrambleTestCase {
 
 		SyncIntegrationTestComponent component =
 				DaggerSyncIntegrationTestComponent.builder().build();
-		BrambleCoreEagerSingletons.Helper.injectEagerSingletons(component);
+		BrambleCoreIntegrationTestEagerSingletons.Helper
+				.injectEagerSingletons(component);
 		component.inject(this);
 
 		contactId = getContactId();

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

@@ -1,6 +1,6 @@
 package org.briarproject.bramble.sync;
 
-import org.briarproject.bramble.BrambleCoreEagerSingletons;
+import org.briarproject.bramble.BrambleCoreIntegrationTestEagerSingletons;
 import org.briarproject.bramble.BrambleCoreModule;
 import org.briarproject.bramble.test.BrambleCoreIntegrationTestModule;
 
@@ -13,7 +13,8 @@ import dagger.Component;
 		BrambleCoreIntegrationTestModule.class,
 		BrambleCoreModule.class
 })
-interface SyncIntegrationTestComponent extends BrambleCoreEagerSingletons {
+interface SyncIntegrationTestComponent extends
+		BrambleCoreIntegrationTestEagerSingletons {
 
 	void inject(SyncIntegrationTest testCase);
 }

bramble-core/src/test/java/org/briarproject/bramble/test/BrambleCoreIntegrationTestModule.java

@@ -3,6 +3,8 @@ package org.briarproject.bramble.test;
 import org.briarproject.bramble.api.FeatureFlags;
 import org.briarproject.bramble.battery.DefaultBatteryManagerModule;
 import org.briarproject.bramble.event.DefaultEventExecutorModule;
+import org.briarproject.bramble.system.DefaultTaskSchedulerModule;
+import org.briarproject.bramble.system.DefaultWakefulIoExecutorModule;
 
 import dagger.Module;
 import dagger.Provides;
@@ -10,6 +12,8 @@ import dagger.Provides;
 @Module(includes = {
 		DefaultBatteryManagerModule.class,
 		DefaultEventExecutorModule.class,
+		DefaultTaskSchedulerModule.class,
+		DefaultWakefulIoExecutorModule.class,
 		TestDatabaseConfigModule.class,
 		TestPluginConfigModule.class,
 		TestSecureRandomModule.class

bramble-core/src/test/java/org/briarproject/bramble/transport/TransportKeyManagerImplTest.java

@@ -8,6 +8,7 @@ import org.briarproject.bramble.api.db.DatabaseComponent;
 import org.briarproject.bramble.api.db.Transaction;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.system.Clock;
+import org.briarproject.bramble.api.system.TaskScheduler;
 import org.briarproject.bramble.api.transport.IncomingKeys;
 import org.briarproject.bramble.api.transport.KeySetId;
 import org.briarproject.bramble.api.transport.OutgoingKeys;
@@ -29,7 +30,6 @@ import java.util.Collection;
 import java.util.List;
 import java.util.Random;
 import java.util.concurrent.Executor;
-import java.util.concurrent.ScheduledExecutorService;
 
 import static java.util.Arrays.asList;
 import static java.util.Collections.singletonList;
@@ -55,8 +55,7 @@ public class TransportKeyManagerImplTest extends BrambleMockTestCase {
 	private final TransportCrypto transportCrypto =
 			context.mock(TransportCrypto.class);
 	private final Executor dbExecutor = context.mock(Executor.class);
-	private final ScheduledExecutorService scheduler =
-			context.mock(ScheduledExecutorService.class);
+	private final TaskScheduler scheduler = context.mock(TaskScheduler.class);
 	private final Clock clock = context.mock(Clock.class);
 
 	private final TransportId transportId = getTransportId();
@@ -118,7 +117,8 @@ public class TransportKeyManagerImplTest extends BrambleMockTestCase {
 					new TransportKeySet(keySetId, contactId, null, updated)));
 			// Schedule a key update at the start of the next time period
 			oneOf(scheduler).schedule(with(any(Runnable.class)),
-					with(timePeriodLength - 1), with(MILLISECONDS));
+					with(dbExecutor), with(timePeriodLength - 1),
+					with(MILLISECONDS));
 		}});
 
 		transportKeyManager.start(txn);
@@ -421,9 +421,8 @@ public class TransportKeyManagerImplTest extends BrambleMockTestCase {
 			}
 			// Schedule a key update at the start of the next time period
 			oneOf(scheduler).schedule(with(any(Runnable.class)),
-					with(timePeriodLength), with(MILLISECONDS));
-			will(new RunAction());
-			oneOf(dbExecutor).execute(with(any(Runnable.class)));
+					with(dbExecutor), with(timePeriodLength),
+					with(MILLISECONDS));
 			will(new RunAction());
 			// Start a transaction for updating keys
 			oneOf(db).transaction(with(false), withDbRunnable(txn1));
@@ -446,7 +445,8 @@ public class TransportKeyManagerImplTest extends BrambleMockTestCase {
 					new TransportKeySet(keySetId, contactId, null, updated)));
 			// Schedule a key update at the start of the next time period
 			oneOf(scheduler).schedule(with(any(Runnable.class)),
-					with(timePeriodLength), with(MILLISECONDS));
+					with(dbExecutor), with(timePeriodLength),
+					with(MILLISECONDS));
 		}});
 
 		transportKeyManager.start(txn);

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

@@ -1,9 +1,5 @@
 package org.briarproject.bramble.plugin;
 
-import org.briarproject.bramble.api.event.EventBus;
-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.BluetoothConstants;
 import org.briarproject.bramble.api.plugin.LanTcpConstants;
@@ -11,17 +7,14 @@ import org.briarproject.bramble.api.plugin.PluginConfig;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPluginFactory;
 import org.briarproject.bramble.api.plugin.simplex.SimplexPluginFactory;
-import org.briarproject.bramble.api.reliability.ReliabilityLayerFactory;
 import org.briarproject.bramble.plugin.bluetooth.JavaBluetoothPluginFactory;
 import org.briarproject.bramble.plugin.modem.ModemPluginFactory;
 import org.briarproject.bramble.plugin.tcp.LanTcpPluginFactory;
 import org.briarproject.bramble.plugin.tcp.WanTcpPluginFactory;
 
-import java.security.SecureRandom;
 import java.util.Collection;
 import java.util.List;
 import java.util.Map;
-import java.util.concurrent.Executor;
 
 import dagger.Module;
 import dagger.Provides;
@@ -35,25 +28,15 @@ import static java.util.Collections.singletonMap;
 public class DesktopPluginModule extends PluginModule {
 
 	@Provides
-	PluginConfig getPluginConfig(@IoExecutor Executor ioExecutor,
-			SecureRandom random, ReliabilityLayerFactory reliabilityFactory,
-			ShutdownManager shutdownManager, EventBus eventBus,
-			TimeoutMonitor timeoutMonitor) {
-		DuplexPluginFactory bluetooth = new JavaBluetoothPluginFactory(
-				ioExecutor, random, eventBus, timeoutMonitor);
-		DuplexPluginFactory modem = new ModemPluginFactory(ioExecutor,
-				reliabilityFactory);
-		DuplexPluginFactory lan = new LanTcpPluginFactory(ioExecutor, eventBus);
-		DuplexPluginFactory wan = new WanTcpPluginFactory(ioExecutor, eventBus,
-				shutdownManager);
-		Collection<DuplexPluginFactory> duplex =
-				asList(bluetooth, modem, lan, wan);
+	PluginConfig getPluginConfig(JavaBluetoothPluginFactory bluetooth,
+			ModemPluginFactory modem, LanTcpPluginFactory lan,
+			WanTcpPluginFactory wan) {
 		@NotNullByDefault
 		PluginConfig pluginConfig = new PluginConfig() {
 
 			@Override
 			public Collection<DuplexPluginFactory> getDuplexFactories() {
-				return duplex;
+				return asList(bluetooth, modem, lan, wan);
 			}
 
 			@Override

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

@@ -0,0 +1,34 @@
+package org.briarproject.bramble.plugin.bluetooth;
+
+import org.briarproject.bramble.api.io.TimeoutMonitor;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
+import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
+
+import java.io.IOException;
+
+import javax.annotation.concurrent.Immutable;
+import javax.microedition.io.StreamConnection;
+
+@Immutable
+@NotNullByDefault
+class JavaBluetoothConnectionFactory
+		implements BluetoothConnectionFactory<StreamConnection> {
+
+	private final BluetoothConnectionLimiter connectionLimiter;
+	private final TimeoutMonitor timeoutMonitor;
+
+	JavaBluetoothConnectionFactory(
+			BluetoothConnectionLimiter connectionLimiter,
+			TimeoutMonitor timeoutMonitor) {
+		this.connectionLimiter = connectionLimiter;
+		this.timeoutMonitor = timeoutMonitor;
+	}
+
+	@Override
+	public DuplexTransportConnection wrapSocket(DuplexPlugin plugin,
+			StreamConnection socket) throws IOException {
+		return new JavaBluetoothTransportConnection(plugin, connectionLimiter,
+				timeoutMonitor, socket);
+	}
+}

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

@@ -1,8 +1,8 @@
 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;
 
@@ -25,7 +25,8 @@ import static org.briarproject.bramble.util.StringUtils.isValidMac;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
-class JavaBluetoothPlugin extends BluetoothPlugin<StreamConnectionNotifier> {
+class JavaBluetoothPlugin
+		extends BluetoothPlugin<StreamConnection, StreamConnectionNotifier> {
 
 	private static final Logger LOG =
 			getLogger(JavaBluetoothPlugin.class.getName());
@@ -34,11 +35,17 @@ class JavaBluetoothPlugin extends BluetoothPlugin<StreamConnectionNotifier> {
 	private volatile LocalDevice localDevice = null;
 
 	JavaBluetoothPlugin(BluetoothConnectionLimiter connectionManager,
-			TimeoutMonitor timeoutMonitor, Executor ioExecutor,
-			SecureRandom secureRandom, PluginCallback callback, int maxLatency,
-			int maxIdleTime, int pollingInterval) {
-		super(connectionManager, timeoutMonitor, ioExecutor, secureRandom,
-				callback, maxLatency, maxIdleTime, pollingInterval);
+			BluetoothConnectionFactory<StreamConnection> connectionFactory,
+			Executor ioExecutor,
+			Executor wakefulIoExecutor,
+			SecureRandom secureRandom,
+			Backoff backoff,
+			PluginCallback callback,
+			int maxLatency,
+			int maxIdleTime) {
+		super(connectionManager, connectionFactory, ioExecutor,
+				wakefulIoExecutor, secureRandom, backoff, callback,
+				maxLatency, maxIdleTime);
 	}
 
 	@Override
@@ -95,7 +102,7 @@ class JavaBluetoothPlugin extends BluetoothPlugin<StreamConnectionNotifier> {
 	@Override
 	DuplexTransportConnection acceptConnection(StreamConnectionNotifier ss)
 			throws IOException {
-		return wrapSocket(ss.acceptAndOpen());
+		return connectionFactory.wrapSocket(this, ss.acceptAndOpen());
 	}
 
 	@Override
@@ -107,7 +114,8 @@ class JavaBluetoothPlugin extends BluetoothPlugin<StreamConnectionNotifier> {
 	DuplexTransportConnection connectTo(String address, String uuid)
 			throws IOException {
 		String url = makeUrl(address, uuid);
-		return wrapSocket((StreamConnection) Connector.open(url));
+		StreamConnection s = (StreamConnection) Connector.open(url);
+		return connectionFactory.wrapSocket(this, s);
 	}
 
 	@Override
@@ -119,10 +127,4 @@ class JavaBluetoothPlugin extends BluetoothPlugin<StreamConnectionNotifier> {
 	private String makeUrl(String address, String uuid) {
 		return "btspp://" + address + ":" + uuid + ";name=RFCOMM";
 	}
-
-	private DuplexTransportConnection wrapSocket(StreamConnection s)
-			throws IOException {
-		return new JavaBluetoothTransportConnection(this, connectionLimiter,
-				timeoutMonitor, s);
-	}
 }

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

@@ -2,41 +2,54 @@ 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.lifecycle.IoExecutor;
 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;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPluginFactory;
+import org.briarproject.bramble.api.system.WakefulIoExecutor;
 
 import java.security.SecureRandom;
 import java.util.concurrent.Executor;
 
 import javax.annotation.concurrent.Immutable;
+import javax.inject.Inject;
+import javax.microedition.io.StreamConnection;
 
-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 Executor ioExecutor, wakefulIoExecutor;
 	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) {
+	@Inject
+	public JavaBluetoothPluginFactory(@IoExecutor Executor ioExecutor,
+			@WakefulIoExecutor Executor wakefulIoExecutor,
+			SecureRandom secureRandom,
+			EventBus eventBus,
+			TimeoutMonitor timeoutMonitor,
+			BackoffFactory backoffFactory) {
 		this.ioExecutor = ioExecutor;
+		this.wakefulIoExecutor = wakefulIoExecutor;
 		this.secureRandom = secureRandom;
 		this.eventBus = eventBus;
 		this.timeoutMonitor = timeoutMonitor;
+		this.backoffFactory = backoffFactory;
 	}
 
 	@Override
@@ -53,9 +66,14 @@ public class JavaBluetoothPluginFactory implements DuplexPluginFactory {
 	public DuplexPlugin createPlugin(PluginCallback callback) {
 		BluetoothConnectionLimiter connectionLimiter =
 				new BluetoothConnectionLimiterImpl(eventBus);
+		BluetoothConnectionFactory<StreamConnection> connectionFactory =
+				new JavaBluetoothConnectionFactory(connectionLimiter,
+						timeoutMonitor);
+		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);
+				connectionFactory, ioExecutor, wakefulIoExecutor, secureRandom,
+				backoff, callback, MAX_LATENCY, MAX_IDLE_TIME);
 		eventBus.addListener(plugin);
 		return plugin;
 	}

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

@@ -16,18 +16,20 @@ class JavaBluetoothTransportConnection
 		extends AbstractDuplexTransportConnection {
 
 	private final BluetoothConnectionLimiter connectionLimiter;
-	private final StreamConnection stream;
+	private final StreamConnection socket;
 	private final InputStream in;
+	private final OutputStream out;
 
 	JavaBluetoothTransportConnection(Plugin plugin,
 			BluetoothConnectionLimiter connectionLimiter,
 			TimeoutMonitor timeoutMonitor,
-			StreamConnection stream) throws IOException {
+			StreamConnection socket) throws IOException {
 		super(plugin);
 		this.connectionLimiter = connectionLimiter;
-		this.stream = stream;
+		this.socket = socket;
 		in = timeoutMonitor.createTimeoutInputStream(
-				stream.openInputStream(), plugin.getMaxIdleTime() * 2);
+				socket.openInputStream(), plugin.getMaxIdleTime() * 2);
+		out = socket.openOutputStream();
 	}
 
 	@Override
@@ -36,14 +38,15 @@ class JavaBluetoothTransportConnection
 	}
 
 	@Override
-	protected OutputStream getOutputStream() throws IOException {
-		return stream.openOutputStream();
+	protected OutputStream getOutputStream() {
+		return out;
 	}
 
 	@Override
 	protected void closeConnection(boolean exception) throws IOException {
 		try {
-			stream.close();
+			socket.close();
+			in.close();
 		} finally {
 			connectionLimiter.connectionClosed(this);
 		}

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

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.plugin.modem;
 
+import org.briarproject.bramble.api.lifecycle.IoExecutor;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.PluginCallback;
 import org.briarproject.bramble.api.plugin.TransportId;
@@ -11,6 +12,7 @@ import org.briarproject.bramble.util.StringUtils;
 import java.util.concurrent.Executor;
 
 import javax.annotation.concurrent.Immutable;
+import javax.inject.Inject;
 
 @Immutable
 @NotNullByDefault
@@ -21,7 +23,8 @@ public class ModemPluginFactory implements DuplexPluginFactory {
 	private final ModemFactory modemFactory;
 	private final SerialPortList serialPortList;
 
-	public ModemPluginFactory(Executor ioExecutor,
+	@Inject
+	public ModemPluginFactory(@IoExecutor Executor ioExecutor,
 			ReliabilityLayerFactory reliabilityFactory) {
 		modemFactory = new ModemFactoryImpl(ioExecutor, reliabilityFactory);
 		serialPortList = new SerialPortListImpl();

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;
@@ -19,20 +20,27 @@ import javax.net.SocketFactory;
 @NotNullByDefault
 abstract class JavaTorPlugin extends TorPlugin {
 
-	JavaTorPlugin(Executor ioExecutor, NetworkManager networkManager,
-			LocationUtils locationUtils, SocketFactory torSocketFactory,
-			Clock clock, ResourceProvider resourceProvider,
+	JavaTorPlugin(Executor ioExecutor,
+			Executor wakefulIoExecutor,
+			NetworkManager networkManager,
+			LocationUtils locationUtils,
+			SocketFactory torSocketFactory,
+			Clock clock,
+			ResourceProvider resourceProvider,
 			CircumventionProvider circumventionProvider,
 			BatteryManager batteryManager,
+			Backoff backoff,
 			TorRendezvousCrypto torRendezvousCrypto,
-			PluginCallback callback, String architecture, int maxLatency,
-			int maxIdleTime, int initialPollingInterval,
-			int stablePollingInterval, File torDirectory) {
-		super(ioExecutor, networkManager, locationUtils, torSocketFactory,
-				clock, resourceProvider, circumventionProvider, batteryManager,
-				torRendezvousCrypto, callback, architecture, maxLatency,
-				maxIdleTime, initialPollingInterval, stablePollingInterval,
-				torDirectory);
+			PluginCallback callback,
+			String architecture,
+			int maxLatency,
+			int maxIdleTime,
+			File torDirectory) {
+		super(ioExecutor, wakefulIoExecutor, networkManager, locationUtils,
+				torSocketFactory, clock, resourceProvider,
+				circumventionProvider, batteryManager, 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;
@@ -19,20 +20,27 @@ import javax.net.SocketFactory;
 @NotNullByDefault
 class UnixTorPlugin extends JavaTorPlugin {
 
-	UnixTorPlugin(Executor ioExecutor, NetworkManager networkManager,
-			LocationUtils locationUtils, SocketFactory torSocketFactory,
-			Clock clock, ResourceProvider resourceProvider,
+	UnixTorPlugin(Executor ioExecutor,
+			Executor wakefulIoExecutor,
+			NetworkManager networkManager,
+			LocationUtils locationUtils,
+			SocketFactory torSocketFactory,
+			Clock clock,
+			ResourceProvider resourceProvider,
 			CircumventionProvider circumventionProvider,
 			BatteryManager batteryManager,
+			Backoff backoff,
 			TorRendezvousCrypto torRendezvousCrypto,
-			PluginCallback callback, String architecture, int maxLatency,
-			int maxIdleTime, int initialPollingInterval,
-			int stablePollingInterval, File torDirectory) {
-		super(ioExecutor, networkManager, locationUtils, torSocketFactory,
-				clock, resourceProvider, circumventionProvider, batteryManager,
+			PluginCallback callback,
+			String architecture,
+			int maxLatency,
+			int maxIdleTime,
+			File torDirectory) {
+		super(ioExecutor, wakefulIoExecutor, networkManager, locationUtils,
+				torSocketFactory, clock, resourceProvider,
+				circumventionProvider, batteryManager, backoff,
 				torRendezvousCrypto, callback, architecture,
-				maxLatency, maxIdleTime, initialPollingInterval,
-				stablePollingInterval, torDirectory);
+				maxLatency, maxIdleTime, torDirectory);
 	}
 
 	@Override

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

@@ -2,10 +2,14 @@ package org.briarproject.bramble.plugin.tor;
 
 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.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.TorDirectory;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPluginFactory;
@@ -18,10 +22,9 @@ import java.util.concurrent.Executor;
 import java.util.logging.Logger;
 
 import javax.annotation.concurrent.Immutable;
+import javax.inject.Inject;
 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;
 
@@ -32,45 +35,44 @@ 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);
+	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;
 
-	/**
-	 * 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 final Executor ioExecutor;
+	private final Executor ioExecutor, wakefulIoExecutor;
 	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;
 	private final Clock clock;
 	private final File torDirectory;
 
-	public UnixTorPluginFactory(Executor ioExecutor,
-			NetworkManager networkManager, LocationUtils locationUtils,
-			EventBus eventBus, SocketFactory torSocketFactory,
+	@Inject
+	public UnixTorPluginFactory(@IoExecutor Executor ioExecutor,
+			@IoExecutor Executor wakefulIoExecutor,
+			NetworkManager networkManager,
+			LocationUtils locationUtils,
+			EventBus eventBus,
+			SocketFactory torSocketFactory,
+			BackoffFactory backoffFactory,
 			ResourceProvider resourceProvider,
 			CircumventionProvider circumventionProvider,
-			BatteryManager batteryManager, Clock clock, File torDirectory) {
+			BatteryManager batteryManager,
+			Clock clock,
+			@TorDirectory File torDirectory) {
 		this.ioExecutor = ioExecutor;
+		this.wakefulIoExecutor = wakefulIoExecutor;
 		this.networkManager = networkManager;
 		this.locationUtils = locationUtils;
 		this.eventBus = eventBus;
 		this.torSocketFactory = torSocketFactory;
+		this.backoffFactory = backoffFactory;
 		this.resourceProvider = resourceProvider;
 		this.circumventionProvider = circumventionProvider;
 		this.batteryManager = batteryManager;
@@ -103,13 +105,14 @@ 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);
+		UnixTorPlugin plugin = new UnixTorPlugin(ioExecutor, wakefulIoExecutor,
+				networkManager, locationUtils, torSocketFactory, clock,
+				resourceProvider, 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/tor/BridgeTest.java

@@ -1,14 +1,16 @@
 package org.briarproject.bramble.plugin.tor;
 
-import org.briarproject.bramble.BrambleCoreEagerSingletons;
+import org.briarproject.bramble.BrambleCoreIntegrationTestEagerSingletons;
 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;
 import org.briarproject.bramble.api.system.ResourceProvider;
+import org.briarproject.bramble.api.system.WakefulIoExecutor;
 import org.briarproject.bramble.test.BrambleJavaIntegrationTestComponent;
 import org.briarproject.bramble.test.BrambleTestCase;
 import org.briarproject.bramble.test.DaggerBrambleJavaIntegrationTestComponent;
@@ -46,7 +48,8 @@ public class BridgeTest extends BrambleTestCase {
 	public static Iterable<String> data() {
 		BrambleJavaIntegrationTestComponent component =
 				DaggerBrambleJavaIntegrationTestComponent.builder().build();
-		BrambleCoreEagerSingletons.Helper.injectEagerSingletons(component);
+		BrambleCoreIntegrationTestEagerSingletons.Helper
+				.injectEagerSingletons(component);
 		return component.getCircumventionProvider().getBridges(false);
 	}
 
@@ -58,6 +61,9 @@ public class BridgeTest extends BrambleTestCase {
 	@IoExecutor
 	Executor ioExecutor;
 	@Inject
+	@WakefulIoExecutor
+	Executor wakefulIoExecutor;
+	@Inject
 	NetworkManager networkManager;
 	@Inject
 	ResourceProvider resourceProvider;
@@ -68,6 +74,8 @@ public class BridgeTest extends BrambleTestCase {
 	@Inject
 	EventBus eventBus;
 	@Inject
+	BackoffFactory backoffFactory;
+	@Inject
 	Clock clock;
 
 	private final File torDir = getTestDirectory();
@@ -89,7 +97,8 @@ public class BridgeTest extends BrambleTestCase {
 
 		BrambleJavaIntegrationTestComponent component =
 				DaggerBrambleJavaIntegrationTestComponent.builder().build();
-		BrambleCoreEagerSingletons.Helper.injectEagerSingletons(component);
+		BrambleCoreIntegrationTestEagerSingletons.Helper
+				.injectEagerSingletons(component);
 		component.inject(this);
 
 		LocationUtils locationUtils = () -> "US";
@@ -116,9 +125,10 @@ public class BridgeTest extends BrambleTestCase {
 				return singletonList(bridge);
 			}
 		};
-		factory = new UnixTorPluginFactory(ioExecutor, networkManager,
-				locationUtils, eventBus, torSocketFactory, resourceProvider,
-				bridgeProvider, batteryManager, clock, torDir);
+		factory = new UnixTorPluginFactory(ioExecutor, wakefulIoExecutor,
+				networkManager, locationUtils, eventBus, torSocketFactory,
+				backoffFactory, resourceProvider, bridgeProvider,
+				batteryManager, clock, torDir);
 	}
 
 	@After

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

@@ -9,6 +9,10 @@ import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
 import org.briarproject.bramble.api.properties.TransportProperties;
 import org.briarproject.bramble.api.settings.Settings;
 
+import java.util.Collection;
+
+import static java.util.Collections.emptyList;
+
 @NotNullByDefault
 public class TestPluginCallback implements PluginCallback {
 
@@ -22,6 +26,11 @@ public class TestPluginCallback implements PluginCallback {
 		return new TransportProperties();
 	}
 
+	@Override
+	public Collection<TransportProperties> getRemoteProperties() {
+		return emptyList();
+	}
+
 	@Override
 	public void mergeSettings(Settings s) {
 	}

bramble-java/src/test/java/org/briarproject/bramble/test/BrambleJavaIntegrationTestComponent.java

@@ -1,6 +1,6 @@
 package org.briarproject.bramble.test;
 
-import org.briarproject.bramble.BrambleCoreEagerSingletons;
+import org.briarproject.bramble.BrambleCoreIntegrationTestEagerSingletons;
 import org.briarproject.bramble.BrambleCoreModule;
 import org.briarproject.bramble.BrambleJavaModule;
 import org.briarproject.bramble.plugin.tor.BridgeTest;
@@ -17,7 +17,7 @@ import dagger.Component;
 		BrambleJavaModule.class
 })
 public interface BrambleJavaIntegrationTestComponent
-		extends BrambleCoreEagerSingletons {
+		extends BrambleCoreIntegrationTestEagerSingletons {
 
 	void inject(BridgeTest init);
 

briar-android/build.gradle

@@ -22,8 +22,8 @@ android {
 	defaultConfig {
 		minSdkVersion 16
 		targetSdkVersion 28
-		versionCode 10207
-		versionName "1.2.7"
+		versionCode 10209
+		versionName "1.2.9"
 		applicationId "org.briarproject.briar.android"
 		buildConfigField "String", "GitHash",
 				"\"${getStdout(['git', 'rev-parse', '--short=7', 'HEAD'], 'No commit hash')}\""