Add comment explaining relationship between constants.

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

@@ -86,8 +86,8 @@ public class AndroidBluetoothPluginFactory implements DuplexPluginFactory {
 		BluetoothConnectionFactory<BluetoothSocket> connectionFactory =
 				new AndroidBluetoothConnectionFactory(connectionLimiter,
 						wakeLockManager, timeoutMonitor);
-		Backoff backoff = backoffFactory.createBackoff(MIN_POLLING_INTERVAL,
-				MAX_POLLING_INTERVAL, BACKOFF_BASE);
+		Backoff backoff = backoffFactory.createBackoff(eventBus, ID,
+				MIN_POLLING_INTERVAL, MAX_POLLING_INTERVAL, BACKOFF_BASE);
 		AndroidBluetoothPlugin plugin = new AndroidBluetoothPlugin(
 				connectionLimiter, connectionFactory, ioExecutor,
 				wakefulIoExecutor, secureRandom, androidExecutor, app,

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

@@ -61,8 +61,8 @@ public class AndroidLanTcpPluginFactory implements DuplexPluginFactory {
 
 	@Override
 	public DuplexPlugin createPlugin(PluginCallback callback) {
-		Backoff backoff = backoffFactory.createBackoff(MIN_POLLING_INTERVAL,
-				MAX_POLLING_INTERVAL, BACKOFF_BASE);
+		Backoff backoff = backoffFactory.createBackoff(eventBus, ID,
+				MIN_POLLING_INTERVAL, MAX_POLLING_INTERVAL, BACKOFF_BASE);
 		AndroidLanTcpPlugin plugin = new AndroidLanTcpPlugin(ioExecutor,
 				wakefulIoExecutor, app, backoff, callback,
 				MAX_LATENCY, MAX_IDLE_TIME, CONNECTION_TIMEOUT);

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

@@ -9,7 +9,6 @@ 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;
@@ -64,7 +63,6 @@ class AndroidTorPlugin extends TorPlugin {
 			CircumventionProvider circumventionProvider,
 			BatteryManager batteryManager,
 			AndroidWakeLockManager wakeLockManager,
-			Backoff backoff,
 			TorRendezvousCrypto torRendezvousCrypto,
 			PluginCallback callback,
 			String architecture,
@@ -75,7 +73,7 @@ class AndroidTorPlugin extends TorPlugin {
 			int torControlPort) {
 		super(ioExecutor, wakefulIoExecutor, networkManager, locationUtils,
 				torSocketFactory, clock, resourceProvider,
-				circumventionProvider, batteryManager, backoff,
+				circumventionProvider, batteryManager,
 				torRendezvousCrypto, callback, architecture, maxLatency,
 				maxIdleTime, torDirectory, torSocksPort, torControlPort);
 		this.app = app;

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

@@ -8,8 +8,6 @@ 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.TorControlPort;
 import org.briarproject.bramble.api.plugin.TorDirectory;
@@ -44,7 +42,6 @@ public class AndroidTorPluginFactory extends TorPluginFactory {
 			LocationUtils locationUtils,
 			EventBus eventBus,
 			SocketFactory torSocketFactory,
-			BackoffFactory backoffFactory,
 			ResourceProvider resourceProvider,
 			CircumventionProvider circumventionProvider,
 			BatteryManager batteryManager,
@@ -56,7 +53,7 @@ public class AndroidTorPluginFactory extends TorPluginFactory {
 			Application app,
 			AndroidWakeLockManager wakeLockManager) {
 		super(ioExecutor, wakefulIoExecutor, networkManager, locationUtils,
-				eventBus, torSocketFactory, backoffFactory, resourceProvider,
+				eventBus, torSocketFactory, resourceProvider,
 				circumventionProvider, batteryManager, clock, crypto,
 				torDirectory, torSocksPort, torControlPort);
 		this.app = app;
@@ -76,14 +73,14 @@ public class AndroidTorPluginFactory extends TorPluginFactory {
 	}
 
 	@Override
-	TorPlugin createPluginInstance(Backoff backoff,
-			TorRendezvousCrypto torRendezvousCrypto, PluginCallback callback,
+	TorPlugin createPluginInstance(TorRendezvousCrypto torRendezvousCrypto,
+			PluginCallback callback,
 			String architecture) {
 		return new AndroidTorPlugin(ioExecutor,
 				wakefulIoExecutor, app, networkManager, locationUtils,
 				torSocketFactory, clock, resourceProvider,
 				circumventionProvider, batteryManager, wakeLockManager,
-				backoff, torRendezvousCrypto, callback, architecture,
+				torRendezvousCrypto, callback, architecture,
 				MAX_LATENCY, MAX_IDLE_TIME, torDirectory, torSocksPort,
 				torControlPort);
 	}

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

@@ -1,7 +1,9 @@
 package org.briarproject.bramble.api.plugin;
 
+import org.briarproject.bramble.api.event.EventBus;
+
 public interface BackoffFactory {
 
-	Backoff createBackoff(int minInterval, int maxInterval,
-			double base);
+	Backoff createBackoff(EventBus eventBus, TransportId transportId,
+			int minInterval, int maxInterval, double base);
 }

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

@@ -56,4 +56,9 @@ public interface PluginCallback extends ConnectionHandler {
 	 * This method can safely be called while holding a lock.
 	 */
 	void pluginStateChanged(State state);
+
+	/**
+	 * Informs the callback that the plugin's polling interval has decreased.
+	 */
+	void pollingIntervalDecreased();
 }

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

@@ -0,0 +1,25 @@
+package org.briarproject.bramble.api.plugin.event;
+
+import org.briarproject.bramble.api.event.Event;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.TransportId;
+
+import javax.annotation.concurrent.Immutable;
+
+/**
+ * An event that is broadcast when a plugin's polling interval decreases.
+ */
+@Immutable
+@NotNullByDefault
+public class PollingIntervalDecreasedEvent extends Event {
+
+	private final TransportId transportId;
+
+	public PollingIntervalDecreasedEvent(TransportId transportId) {
+		this.transportId = transportId;
+	}
+
+	public TransportId getTransportId() {
+		return transportId;
+	}
+}

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

@@ -1,8 +1,10 @@
 package org.briarproject.bramble.plugin;
 
+import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.Backoff;
 import org.briarproject.bramble.api.plugin.BackoffFactory;
+import org.briarproject.bramble.api.plugin.TransportId;
 
 import javax.annotation.concurrent.Immutable;
 
@@ -11,8 +13,9 @@ import javax.annotation.concurrent.Immutable;
 class BackoffFactoryImpl implements BackoffFactory {
 
 	@Override
-	public Backoff createBackoff(int minInterval, int maxInterval,
-			double base) {
-		return new BackoffImpl(minInterval, maxInterval, base);
+	public Backoff createBackoff(EventBus eventBus, TransportId transportId,
+			int minInterval, int maxInterval, double base) {
+		return new BackoffImpl(eventBus, transportId, minInterval, maxInterval,
+				base);
 	}
 }

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

@@ -1,7 +1,10 @@
 package org.briarproject.bramble.plugin;
 
+import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.Backoff;
+import org.briarproject.bramble.api.plugin.TransportId;
+import org.briarproject.bramble.api.plugin.event.PollingIntervalDecreasedEvent;
 
 import java.util.concurrent.atomic.AtomicInteger;
 
@@ -11,11 +14,16 @@ import javax.annotation.concurrent.ThreadSafe;
 @NotNullByDefault
 class BackoffImpl implements Backoff {
 
+	private final EventBus eventBus;
+	private final TransportId transportId;
 	private final int minInterval, maxInterval;
 	private final double base;
 	private final AtomicInteger backoff;
 
-	BackoffImpl(int minInterval, int maxInterval, double base) {
+	BackoffImpl(EventBus eventBus, TransportId transportId,
+			int minInterval, int maxInterval, double base) {
+		this.eventBus = eventBus;
+		this.transportId = transportId;
 		this.minInterval = minInterval;
 		this.maxInterval = maxInterval;
 		this.base = base;
@@ -37,6 +45,9 @@ class BackoffImpl implements Backoff {
 
 	@Override
 	public void reset() {
-		backoff.set(0);
+		int old = backoff.getAndSet(0);
+		if (old > 0) {
+			eventBus.broadcast(new PollingIntervalDecreasedEvent(transportId));
+		}
 	}
 }

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

@@ -20,6 +20,7 @@ import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPluginFactory;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
+import org.briarproject.bramble.api.plugin.event.PollingIntervalDecreasedEvent;
 import org.briarproject.bramble.api.plugin.event.TransportActiveEvent;
 import org.briarproject.bramble.api.plugin.event.TransportInactiveEvent;
 import org.briarproject.bramble.api.plugin.event.TransportStateEvent;
@@ -362,6 +363,11 @@ class PluginManagerImpl implements PluginManager, Service {
 			}
 		}
 
+		@Override
+		public void pollingIntervalDecreased() {
+			eventBus.broadcast(new PollingIntervalDecreasedEvent(id));
+		}
+
 		@Override
 		public void handleConnection(DuplexTransportConnection d) {
 			connectionManager.manageIncomingConnection(id, d);

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

@@ -20,7 +20,7 @@ import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
 import org.briarproject.bramble.api.plugin.event.ConnectionClosedEvent;
-import org.briarproject.bramble.api.plugin.event.ConnectionOpenedEvent;
+import org.briarproject.bramble.api.plugin.event.PollingIntervalDecreasedEvent;
 import org.briarproject.bramble.api.plugin.event.TransportActiveEvent;
 import org.briarproject.bramble.api.plugin.event.TransportInactiveEvent;
 import org.briarproject.bramble.api.plugin.simplex.SimplexPlugin;
@@ -107,10 +107,14 @@ class PollerImpl implements Poller, EventListener {
 			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 PollingIntervalDecreasedEvent) {
+			PollingIntervalDecreasedEvent p = (PollingIntervalDecreasedEvent) e;
+			TransportId t = p.getTransportId();
+			if (LOG.isLoggable(INFO)) {
+				LOG.info("Polling interval decreased for " + t);
+			}
+			// Reschedule polling
+			reschedule(t);
 		} else if (e instanceof TransportActiveEvent) {
 			TransportActiveEvent t = (TransportActiveEvent) e;
 			// Poll the newly activated transport
@@ -228,7 +232,7 @@ class PollerImpl implements Poller, EventListener {
 				if (!connected.contains(c))
 					properties.add(new Pair<>(e.getValue(), new Handler(c, t)));
 			}
-			if (!properties.isEmpty()) p.poll(properties);
+			p.poll(properties);
 		} catch (DbException e) {
 			logException(LOG, WARNING, e);
 		}

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

@@ -335,7 +335,7 @@ abstract class AbstractBluetoothPlugin<S, SS> implements BluetoothPlugin,
 	@Override
 	public void poll(Collection<Pair<TransportProperties, ConnectionHandler>>
 			properties) {
-		if (getState() != ACTIVE) return;
+		if (properties.isEmpty() || getState() != ACTIVE) return;
 		backoff.increment();
 		for (Pair<TransportProperties, ConnectionHandler> p : properties) {
 			connect(p.getFirst(), p.getSecond());

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

@@ -56,8 +56,8 @@ public class LanTcpPluginFactory implements DuplexPluginFactory {
 
 	@Override
 	public DuplexPlugin createPlugin(PluginCallback callback) {
-		Backoff backoff = backoffFactory.createBackoff(MIN_POLLING_INTERVAL,
-				MAX_POLLING_INTERVAL, BACKOFF_BASE);
+		Backoff backoff = backoffFactory.createBackoff(eventBus, ID,
+				MIN_POLLING_INTERVAL, MAX_POLLING_INTERVAL, BACKOFF_BASE);
 		LanTcpPlugin plugin = new LanTcpPlugin(ioExecutor, wakefulIoExecutor,
 				backoff, callback, MAX_LATENCY, MAX_IDLE_TIME,
 				CONNECTION_TIMEOUT);

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

@@ -246,7 +246,7 @@ abstract class TcpPlugin implements DuplexPlugin, EventListener {
 	@Override
 	public void poll(Collection<Pair<TransportProperties, ConnectionHandler>>
 			properties) {
-		if (getState() != ACTIVE) return;
+		if (properties.isEmpty() || getState() != ACTIVE) return;
 		backoff.increment();
 		for (Pair<TransportProperties, ConnectionHandler> p : properties) {
 			connect(p.getFirst(), p.getSecond());

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

@@ -60,8 +60,8 @@ public class WanTcpPluginFactory implements DuplexPluginFactory {
 
 	@Override
 	public DuplexPlugin createPlugin(PluginCallback callback) {
-		Backoff backoff = backoffFactory.createBackoff(MIN_POLLING_INTERVAL,
-				MAX_POLLING_INTERVAL, BACKOFF_BASE);
+		Backoff backoff = backoffFactory.createBackoff(eventBus, ID,
+				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,

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

@@ -18,7 +18,6 @@ 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;
@@ -26,6 +25,7 @@ import org.briarproject.bramble.api.plugin.TorConstants;
 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.properties.TransportProperties;
 import org.briarproject.bramble.api.rendezvous.KeyMaterialSource;
 import org.briarproject.bramble.api.rendezvous.RendezvousEndpoint;
@@ -67,6 +67,7 @@ import javax.net.SocketFactory;
 import static java.util.Arrays.asList;
 import static java.util.Collections.singletonList;
 import static java.util.Collections.singletonMap;
+import static java.util.concurrent.TimeUnit.MINUTES;
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
@@ -124,6 +125,45 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	private static final int COOKIE_POLLING_INTERVAL_MS = 200;
 	private static final Pattern ONION_V3 = Pattern.compile("[a-z2-7]{56}");
 
+	/**
+	 * After this many consecutive successful connections to our own hidden
+	 * service we consider the network to be stable.
+	 * <p>
+	 * This constant times {@link #POLLING_INTERVAL_UNSTABLE} should be
+	 * greater than {@link #POLLING_INTERVAL_STABLE}. This ensures that if
+	 * we experience a network outage that isn't detected by the
+	 * {@link NetworkManager}, and if one of our contacts comes online during
+	 * the outage, then either the outage lasts longer than
+	 * {@link #POLLING_INTERVAL_STABLE}, in which case we detect the outage
+	 * by failing to connect to our own hidden service, or the outage ends
+	 * before the contact considers their own network connection to be stable,
+	 * in which case the contact is still trying to connect to us when the
+	 * outage ends. Either way, we don't end up in a situation where both we
+	 * and the contact consider our network connections to be stable and stop
+	 * trying to connect to each other, despite both being online.
+	 */
+	private static final int STABLE_NETWORK_THRESHOLD = 10;
+
+	/**
+	 * After this many consecutive failed connections to our own hidden service
+	 * we consider our connection to the Tor network to be broken.
+	 */
+	private static final int BROKEN_NETWORK_THRESHOLD = 3;
+
+	/**
+	 * How often to poll our own hidden service when the network is considered
+	 * to be stable.
+	 */
+	private static final int POLLING_INTERVAL_STABLE =
+			(int) MINUTES.toMillis(10);
+
+	/**
+	 * How often to poll our own hidden service and our contacts' hidden
+	 * services when the network is considered to be unstable.
+	 */
+	private static final int POLLING_INTERVAL_UNSTABLE =
+			(int) MINUTES.toMillis(2);
+
 	protected final Executor ioExecutor;
 	private final Executor wakefulIoExecutor;
 	private final Executor connectionStatusExecutor;
@@ -132,7 +172,6 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	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;
@@ -152,6 +191,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	private volatile Socket controlSocket = null;
 	private volatile TorControlConnection controlConnection = null;
 	private volatile Settings settings = null;
+	private volatile String ownOnion = null;
 
 	protected abstract int getProcessId();
 
@@ -166,7 +206,6 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			ResourceProvider resourceProvider,
 			CircumventionProvider circumventionProvider,
 			BatteryManager batteryManager,
-			Backoff backoff,
 			TorRendezvousCrypto torRendezvousCrypto,
 			PluginCallback callback,
 			String architecture,
@@ -184,7 +223,6 @@ 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;
@@ -474,7 +512,6 @@ 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);
 		});
@@ -513,6 +550,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			return;
 		}
 		String onion3 = response.get(HS_ADDRESS);
+		ownOnion = onion3;
 		if (LOG.isLoggable(INFO)) {
 			LOG.info("V3 hidden service " + scrubOnion(onion3));
 		}
@@ -541,7 +579,6 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 				return;
 			}
 			LOG.info("Connection received");
-			backoff.reset();
 			callback.handleConnection(new TorTransportConnection(this, s));
 		}
 	}
@@ -618,14 +655,58 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 
 	@Override
 	public int getPollingInterval() {
-		return backoff.getPollingInterval();
+		if (state.isNetworkStable()) {
+			LOG.info("Using stable polling interval");
+			return POLLING_INTERVAL_STABLE;
+		} else {
+			LOG.info("Using unstable polling interval");
+			return POLLING_INTERVAL_UNSTABLE;
+		}
 	}
 
 	@Override
 	public void poll(Collection<Pair<TransportProperties, ConnectionHandler>>
 			properties) {
 		if (getState() != ACTIVE) return;
-		backoff.increment();
+		String ownOnion = this.ownOnion;
+		if (ownOnion == null) {
+			// Our own hidden service hasn't been created yet
+			pollContacts(properties);
+		} else {
+			// If the network is unstable, poll our contacts
+			boolean stable = state.isNetworkStable();
+			if (!stable) pollContacts(properties);
+			// Poll our own hidden service to check if the network is stable
+			wakefulIoExecutor.execute(() -> {
+				LOG.info("Connecting to own hidden service");
+				TransportProperties p = new TransportProperties();
+				p.put(PROP_ONION_V3, ownOnion);
+				DuplexTransportConnection d = createConnection(p);
+				if (d == null) {
+					LOG.info("Could not connect to own hidden service");
+					state.onStabilityCheckFailed();
+					// If the network was previously considered stable then
+					// we didn't poll our contacts above, so poll them now
+					if (stable) pollContacts(properties);
+				} else {
+					LOG.info("Connected to own hidden service");
+					// Close the connection (this will cause the other end of
+					// the connection to log an EOFException)
+					try {
+						d.getWriter().dispose(false);
+						d.getReader().dispose(false, false);
+					} catch (IOException e) {
+						logException(LOG, WARNING, e);
+					}
+					state.onStabilityCheckSucceeded();
+				}
+			});
+		}
+	}
+
+	private void pollContacts(
+			Collection<Pair<TransportProperties, ConnectionHandler>> properties) {
+		if (properties.isEmpty() || getState() != ACTIVE) return;
 		for (Pair<TransportProperties, ConnectionHandler> p : properties) {
 			connect(p.getFirst(), p.getSecond());
 		}
@@ -634,10 +715,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	private void connect(TransportProperties p, ConnectionHandler h) {
 		wakefulIoExecutor.execute(() -> {
 			DuplexTransportConnection d = createConnection(p);
-			if (d != null) {
-				backoff.reset();
-				h.handleConnection(d);
-			}
+			if (d != null) h.handleConnection(d);
 		});
 	}
 
@@ -760,7 +838,6 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		// DisableNetwork, set our circuitBuilt flag if not already set
 		if (status.equals("BUILT") && !state.getAndSetCircuitBuilt(true)) {
 			LOG.info("Circuit built");
-			backoff.reset();
 		}
 	}
 
@@ -787,6 +864,9 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	@Override
 	public void message(String severity, String msg) {
 		if (LOG.isLoggable(INFO)) LOG.info(severity + " " + msg);
+		if (msg.startsWith("Switching to guard context")) {
+			state.resetNetworkStability();
+		}
 	}
 
 	@Override
@@ -813,12 +893,8 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		if (msg.startsWith("BOOTSTRAP PROGRESS=100")) {
 			LOG.info("Bootstrapped");
 			state.setBootstrapped();
-			backoff.reset();
 		} else if (msg.startsWith("CIRCUIT_ESTABLISHED")) {
-			if (!state.getAndSetCircuitBuilt(true)) {
-				LOG.info("Circuit built");
-				backoff.reset();
-			}
+			if (!state.getAndSetCircuitBuilt(true)) LOG.info("Circuit built");
 		} else if (msg.startsWith("CIRCUIT_NOT_ESTABLISHED")) {
 			if (state.getAndSetCircuitBuilt(false)) {
 				LOG.info("Circuit not built");
@@ -863,7 +939,15 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 
 	@Override
 	public void eventOccurred(Event e) {
-		if (e instanceof SettingsUpdatedEvent) {
+		if (e instanceof ConnectionClosedEvent) {
+			ConnectionClosedEvent c = (ConnectionClosedEvent) e;
+			if (c.getTransportId().equals(getId())
+					&& !c.isIncoming() && c.isException()) {
+				LOG.info("Outgoing connection closed with exception");
+				// The failure may indicate that the network is unstable
+				state.resetNetworkStability();
+			}
+		} else if (e instanceof SettingsUpdatedEvent) {
 			SettingsUpdatedEvent s = (SettingsUpdatedEvent) e;
 			if (s.getNamespace().equals(ID.getString())) {
 				LOG.info("Tor settings updated");
@@ -880,6 +964,18 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		}
 	}
 
+	private void disableAndReenableNetwork() {
+		connectionStatusExecutor.execute(() -> {
+			try {
+				if (state.isTorRunning()) enableNetwork(false);
+			} catch (IOException ex) {
+				logException(LOG, WARNING, ex);
+			}
+		});
+		updateConnectionStatus(networkManager.getNetworkStatus(),
+				batteryManager.isCharging());
+	}
+
 	private void updateConnectionStatus(NetworkStatus status,
 			boolean charging) {
 		connectionStatusExecutor.execute(() -> {
@@ -1008,6 +1104,13 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		@GuardedBy("this")
 		private int reasonsDisabled = 0;
 
+		/**
+		 * The number of consecutive successful (positive) or failed (negative)
+		 * connections to our own hidden service.
+		 */
+		@GuardedBy("this")
+		private int networkStability = 0;
+
 		@GuardedBy("this")
 		@Nullable
 		private ServerSocket serverSocket = null;
@@ -1102,6 +1205,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			}
 			logOrConnections();
 			if (orConnectionsConnected == 0 && oldConnected != 0) {
+				resetNetworkStability();
 				callback.pluginStateChanged(getState());
 			}
 		}
@@ -1112,5 +1216,43 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 				LOG.info(orConnectionsConnected + " OR connections connected");
 			}
 		}
+
+		private synchronized boolean isNetworkStable() {
+			return networkStability >= STABLE_NETWORK_THRESHOLD;
+		}
+
+		private synchronized void onStabilityCheckSucceeded() {
+			if (networkStability <= 0) networkStability = 1;
+			else networkStability++;
+			logNetworkStability();
+		}
+
+		private synchronized void onStabilityCheckFailed() {
+			if (networkStability >= 0) networkStability = -1;
+			else networkStability--;
+			if (networkStability <= -BROKEN_NETWORK_THRESHOLD) {
+				LOG.warning("Connection to Tor appears to be broken");
+				resetNetworkStability();
+				disableAndReenableNetwork();
+			} else {
+				logNetworkStability();
+			}
+		}
+
+		private synchronized void resetNetworkStability() {
+			int old = networkStability;
+			networkStability = 0;
+			logNetworkStability();
+			if (old >= STABLE_NETWORK_THRESHOLD) {
+				callback.pollingIntervalDecreased();
+			}
+		}
+
+		@GuardedBy("this")
+		private void logNetworkStability() {
+			if (LOG.isLoggable(INFO)) {
+				LOG.info("Network stability score " + networkStability);
+			}
+		}
 	}
 }

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

@@ -6,8 +6,6 @@ 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.TorControlPort;
@@ -41,16 +39,12 @@ abstract class TorPluginFactory implements DuplexPluginFactory {
 
 	protected static final int MAX_LATENCY = 30 * 1000; // 30 seconds
 	protected 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;
 
 	protected final Executor ioExecutor, wakefulIoExecutor;
 	protected final NetworkManager networkManager;
 	protected final LocationUtils locationUtils;
 	protected final EventBus eventBus;
 	protected final SocketFactory torSocketFactory;
-	protected final BackoffFactory backoffFactory;
 	protected final ResourceProvider resourceProvider;
 	protected final CircumventionProvider circumventionProvider;
 	protected final BatteryManager batteryManager;
@@ -66,7 +60,6 @@ abstract class TorPluginFactory implements DuplexPluginFactory {
 			LocationUtils locationUtils,
 			EventBus eventBus,
 			SocketFactory torSocketFactory,
-			BackoffFactory backoffFactory,
 			ResourceProvider resourceProvider,
 			CircumventionProvider circumventionProvider,
 			BatteryManager batteryManager,
@@ -81,7 +74,6 @@ abstract class TorPluginFactory implements DuplexPluginFactory {
 		this.locationUtils = locationUtils;
 		this.eventBus = eventBus;
 		this.torSocketFactory = torSocketFactory;
-		this.backoffFactory = backoffFactory;
 		this.resourceProvider = resourceProvider;
 		this.circumventionProvider = circumventionProvider;
 		this.batteryManager = batteryManager;
@@ -95,7 +87,7 @@ abstract class TorPluginFactory implements DuplexPluginFactory {
 	@Nullable
 	abstract String getArchitectureForTorBinary();
 
-	abstract TorPlugin createPluginInstance(Backoff backoff,
+	abstract TorPlugin createPluginInstance(
 			TorRendezvousCrypto torRendezvousCrypto, PluginCallback callback,
 			String architecture);
 
@@ -122,11 +114,9 @@ abstract class TorPluginFactory implements DuplexPluginFactory {
 			LOG.info("The selected architecture for Tor is " + architecture);
 		}
 
-		Backoff backoff = backoffFactory.createBackoff(MIN_POLLING_INTERVAL,
-				MAX_POLLING_INTERVAL, BACKOFF_BASE);
 		TorRendezvousCrypto torRendezvousCrypto =
 				new TorRendezvousCryptoImpl(crypto);
-		TorPlugin plugin = createPluginInstance(backoff, torRendezvousCrypto,
+		TorPlugin plugin = createPluginInstance(torRendezvousCrypto,
 				callback, architecture);
 		eventBus.addListener(plugin);
 		return plugin;

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

@@ -1,45 +1,69 @@
 package org.briarproject.bramble.plugin;
 
-import org.briarproject.bramble.test.BrambleTestCase;
+import org.briarproject.bramble.api.event.EventBus;
+import org.briarproject.bramble.api.plugin.TransportId;
+import org.briarproject.bramble.api.plugin.event.PollingIntervalDecreasedEvent;
+import org.briarproject.bramble.test.BrambleMockTestCase;
+import org.jmock.Expectations;
 import org.junit.Test;
 
+import static org.briarproject.bramble.test.TestUtils.getTransportId;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
 
-public class BackoffImplTest extends BrambleTestCase {
+public class BackoffImplTest extends BrambleMockTestCase {
 
+	private final EventBus eventBus = context.mock(EventBus.class);
+
+	private final TransportId transportId = getTransportId();
 	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);
+		BackoffImpl b = new BackoffImpl(eventBus, transportId,
+				MIN_INTERVAL, MAX_INTERVAL, BASE);
 		assertEquals(MIN_INTERVAL, b.getPollingInterval());
 	}
 
 	@Test
-	public void testIncrementIncreasesPollingInterval() {
-		BackoffImpl b = new BackoffImpl(MIN_INTERVAL, MAX_INTERVAL, BASE);
+	public void testIncrementMethodIncreasesPollingInterval() {
+		BackoffImpl b = new BackoffImpl(eventBus, transportId,
+				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();
+	public void testResetMethodResetsPollingInterval() {
+		BackoffImpl b = new BackoffImpl(eventBus, transportId,
+				MIN_INTERVAL, MAX_INTERVAL, BASE);
 		b.increment();
+		assertTrue(b.getPollingInterval() > MIN_INTERVAL);
+
+		context.checking(new Expectations() {{
+			oneOf(eventBus).broadcast(with(any(
+					PollingIntervalDecreasedEvent.class)));
+		}});
+
+		b.reset();
+		assertEquals(MIN_INTERVAL, b.getPollingInterval());
+		context.assertIsSatisfied();
+
+		// Resetting again should not broadcast another event
 		b.reset();
 		assertEquals(MIN_INTERVAL, b.getPollingInterval());
 	}
 
 	@Test
 	public void testBaseAffectsBackoffSpeed() {
-		BackoffImpl b = new BackoffImpl(MIN_INTERVAL, MAX_INTERVAL, BASE);
+		BackoffImpl b = new BackoffImpl(eventBus, transportId,
+				MIN_INTERVAL, MAX_INTERVAL, BASE);
 		b.increment();
 		int interval = b.getPollingInterval();
-		BackoffImpl b1 = new BackoffImpl(MIN_INTERVAL, MAX_INTERVAL, BASE * 2);
+		BackoffImpl b1 = new BackoffImpl(eventBus, transportId, MIN_INTERVAL,
+				MAX_INTERVAL, BASE * 2);
 		b1.increment();
 		int interval1 = b1.getPollingInterval();
 		assertTrue(interval < interval1);
@@ -47,15 +71,16 @@ public class BackoffImplTest extends BrambleTestCase {
 
 	@Test
 	public void testIntervalDoesNotExceedMaxInterval() {
-		BackoffImpl b = new BackoffImpl(MIN_INTERVAL, MAX_INTERVAL, BASE);
+		BackoffImpl b = new BackoffImpl(eventBus, transportId,
+				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);
+		BackoffImpl b = new BackoffImpl(eventBus, transportId,
+				MIN_INTERVAL, MAX_INTERVAL, Double.POSITIVE_INFINITY);
 		b.increment();
 		assertEquals(MAX_INTERVAL, b.getPollingInterval());
 	}

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

@@ -13,7 +13,7 @@ import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
 import org.briarproject.bramble.api.plugin.event.ConnectionClosedEvent;
-import org.briarproject.bramble.api.plugin.event.ConnectionOpenedEvent;
+import org.briarproject.bramble.api.plugin.event.PollingIntervalDecreasedEvent;
 import org.briarproject.bramble.api.plugin.event.TransportActiveEvent;
 import org.briarproject.bramble.api.plugin.event.TransportInactiveEvent;
 import org.briarproject.bramble.api.plugin.simplex.SimplexPlugin;
@@ -35,7 +35,6 @@ import java.util.concurrent.Executor;
 
 import static java.util.Arrays.asList;
 import static java.util.Collections.emptyList;
-import static java.util.Collections.singletonList;
 import static java.util.Collections.singletonMap;
 import static java.util.concurrent.TimeUnit.MILLISECONDS;
 import static org.briarproject.bramble.test.CollectionMatcher.collectionOf;
@@ -217,7 +216,7 @@ public class PollerImplTest extends BrambleMockTestCase {
 	}
 
 	@Test
-	public void testRescheduleOnConnectionOpened() {
+	public void testRescheduleOnPollingIntervalDecreased() {
 		Plugin plugin = context.mock(Plugin.class);
 
 		context.checking(new Expectations() {{
@@ -240,8 +239,7 @@ public class PollerImplTest extends BrambleMockTestCase {
 			will(returnValue(cancellable));
 		}});
 
-		poller.eventOccurred(new ConnectionOpenedEvent(contactId, transportId,
-				false));
+		poller.eventOccurred(new PollingIntervalDecreasedEvent(transportId));
 	}
 
 	@Test
@@ -281,10 +279,8 @@ public class PollerImplTest extends BrambleMockTestCase {
 			will(returnValue(now + 1));
 		}});
 
-		poller.eventOccurred(new ConnectionOpenedEvent(contactId, transportId,
-				false));
-		poller.eventOccurred(new ConnectionOpenedEvent(contactId, transportId,
-				false));
+		poller.eventOccurred(new PollingIntervalDecreasedEvent(transportId));
+		poller.eventOccurred(new PollingIntervalDecreasedEvent(transportId));
 	}
 
 	@Test
@@ -328,10 +324,8 @@ public class PollerImplTest extends BrambleMockTestCase {
 					with(MILLISECONDS));
 		}});
 
-		poller.eventOccurred(new ConnectionOpenedEvent(contactId, transportId,
-				false));
-		poller.eventOccurred(new ConnectionOpenedEvent(contactId, transportId,
-				false));
+		poller.eventOccurred(new PollingIntervalDecreasedEvent(transportId));
+		poller.eventOccurred(new PollingIntervalDecreasedEvent(transportId));
 	}
 
 	@Test
@@ -378,48 +372,6 @@ public class PollerImplTest extends BrambleMockTestCase {
 		poller.eventOccurred(new TransportActiveEvent(transportId));
 	}
 
-	@Test
-	public void testDoesNotPollIfAllContactsAreConnected() throws Exception {
-		DuplexPlugin plugin = context.mock(DuplexPlugin.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 a polling task immediately
-			oneOf(clock).currentTimeMillis();
-			will(returnValue(now));
-			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();
-			will(returnValue(pollingInterval));
-			oneOf(random).nextDouble();
-			will(returnValue(0.5));
-			oneOf(clock).currentTimeMillis();
-			will(returnValue(now));
-			oneOf(scheduler).schedule(with(any(Runnable.class)),
-					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)));
-			oneOf(connectionRegistry).getConnectedOrBetterContacts(transportId);
-			will(returnValue(singletonList(contactId)));
-			// All contacts are connected, so don't poll the plugin
-		}});
-
-		poller.eventOccurred(new TransportActiveEvent(transportId));
-	}
-
 	@Test
 	public void testCancelsPollingOnTransportDeactivated() {
 		Plugin plugin = context.mock(Plugin.class);

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

@@ -342,6 +342,10 @@ public class LanTcpPluginTest extends BrambleTestCase {
 		public void pluginStateChanged(State newState) {
 		}
 
+		@Override
+		public void pollingIntervalDecreased() {
+		}
+
 		@Override
 		public void handleConnection(DuplexTransportConnection d) {
 			connectionsLatch.countDown();

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

@@ -69,8 +69,8 @@ public class JavaBluetoothPluginFactory implements DuplexPluginFactory {
 		BluetoothConnectionFactory<StreamConnection> connectionFactory =
 				new JavaBluetoothConnectionFactory(connectionLimiter,
 						timeoutMonitor);
-		Backoff backoff = backoffFactory.createBackoff(MIN_POLLING_INTERVAL,
-				MAX_POLLING_INTERVAL, BACKOFF_BASE);
+		Backoff backoff = backoffFactory.createBackoff(eventBus, ID,
+				MIN_POLLING_INTERVAL, MAX_POLLING_INTERVAL, BACKOFF_BASE);
 		JavaBluetoothPlugin plugin = new JavaBluetoothPlugin(connectionLimiter,
 				connectionFactory, ioExecutor, wakefulIoExecutor, secureRandom,
 				backoff, callback, MAX_LATENCY, MAX_IDLE_TIME);

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

@@ -3,7 +3,6 @@ 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;
@@ -29,7 +28,6 @@ abstract class JavaTorPlugin extends TorPlugin {
 			ResourceProvider resourceProvider,
 			CircumventionProvider circumventionProvider,
 			BatteryManager batteryManager,
-			Backoff backoff,
 			TorRendezvousCrypto torRendezvousCrypto,
 			PluginCallback callback,
 			String architecture,
@@ -40,7 +38,7 @@ abstract class JavaTorPlugin extends TorPlugin {
 			int torControlPort) {
 		super(ioExecutor, wakefulIoExecutor, networkManager, locationUtils,
 				torSocketFactory, clock, resourceProvider,
-				circumventionProvider, batteryManager, backoff,
+				circumventionProvider, batteryManager,
 				torRendezvousCrypto, callback, architecture,
 				maxLatency, maxIdleTime, torDirectory, torSocksPort,
 				torControlPort);

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

@@ -6,7 +6,6 @@ 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;
@@ -29,7 +28,6 @@ class UnixTorPlugin extends JavaTorPlugin {
 			ResourceProvider resourceProvider,
 			CircumventionProvider circumventionProvider,
 			BatteryManager batteryManager,
-			Backoff backoff,
 			TorRendezvousCrypto torRendezvousCrypto,
 			PluginCallback callback,
 			String architecture,
@@ -40,7 +38,7 @@ class UnixTorPlugin extends JavaTorPlugin {
 			int torControlPort) {
 		super(ioExecutor, wakefulIoExecutor, networkManager, locationUtils,
 				torSocketFactory, clock, resourceProvider,
-				circumventionProvider, batteryManager, backoff,
+				circumventionProvider, batteryManager,
 				torRendezvousCrypto, callback, architecture,
 				maxLatency, maxIdleTime, torDirectory, torSocksPort,
 				torControlPort);

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

@@ -6,8 +6,6 @@ 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.TorControlPort;
 import org.briarproject.bramble.api.plugin.TorDirectory;
@@ -39,7 +37,6 @@ public class UnixTorPluginFactory extends TorPluginFactory {
 			LocationUtils locationUtils,
 			EventBus eventBus,
 			SocketFactory torSocketFactory,
-			BackoffFactory backoffFactory,
 			ResourceProvider resourceProvider,
 			CircumventionProvider circumventionProvider,
 			BatteryManager batteryManager,
@@ -49,7 +46,7 @@ public class UnixTorPluginFactory extends TorPluginFactory {
 			@TorSocksPort int torSocksPort,
 			@TorControlPort int torControlPort) {
 		super(ioExecutor, wakefulIoExecutor, networkManager, locationUtils,
-				eventBus, torSocketFactory, backoffFactory, resourceProvider,
+				eventBus, torSocketFactory, resourceProvider,
 				circumventionProvider, batteryManager, clock, crypto,
 				torDirectory, torSocksPort, torControlPort);
 	}
@@ -69,13 +66,13 @@ public class UnixTorPluginFactory extends TorPluginFactory {
 	}
 
 	@Override
-	TorPlugin createPluginInstance(Backoff backoff,
-			TorRendezvousCrypto torRendezvousCrypto, PluginCallback callback,
+	TorPlugin createPluginInstance(TorRendezvousCrypto torRendezvousCrypto,
+			PluginCallback callback,
 			String architecture) {
 		return new UnixTorPlugin(ioExecutor, wakefulIoExecutor,
 				networkManager, locationUtils, torSocketFactory, clock,
 				resourceProvider, circumventionProvider, batteryManager,
-				backoff, torRendezvousCrypto, callback, architecture,
+				torRendezvousCrypto, callback, architecture,
 				MAX_LATENCY, MAX_IDLE_TIME, torDirectory, torSocksPort,
 				torControlPort);
 	}

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

@@ -5,7 +5,6 @@ import com.sun.jna.platform.win32.Kernel32;
 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.plugin.PluginException;
 import org.briarproject.bramble.api.system.Clock;
@@ -34,7 +33,6 @@ class WindowsTorPlugin extends JavaTorPlugin {
 			ResourceProvider resourceProvider,
 			CircumventionProvider circumventionProvider,
 			BatteryManager batteryManager,
-			Backoff backoff,
 			TorRendezvousCrypto torRendezvousCrypto,
 			PluginCallback callback,
 			String architecture,
@@ -45,7 +43,7 @@ class WindowsTorPlugin extends JavaTorPlugin {
 			int torControlPort) {
 		super(ioExecutor, wakefulIoExecutor, networkManager, locationUtils,
 				torSocketFactory, clock, resourceProvider,
-				circumventionProvider, batteryManager, backoff,
+				circumventionProvider, batteryManager,
 				torRendezvousCrypto, callback, architecture,
 				maxLatency, maxIdleTime, torDirectory, torSocksPort,
 				torControlPort);

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

@@ -6,8 +6,6 @@ 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.TorControlPort;
 import org.briarproject.bramble.api.plugin.TorDirectory;
@@ -39,7 +37,6 @@ public class WindowsTorPluginFactory extends TorPluginFactory {
 			LocationUtils locationUtils,
 			EventBus eventBus,
 			SocketFactory torSocketFactory,
-			BackoffFactory backoffFactory,
 			ResourceProvider resourceProvider,
 			CircumventionProvider circumventionProvider,
 			BatteryManager batteryManager,
@@ -49,7 +46,7 @@ public class WindowsTorPluginFactory extends TorPluginFactory {
 			@TorSocksPort int torSocksPort,
 			@TorControlPort int torControlPort) {
 		super(ioExecutor, wakefulIoExecutor, networkManager, locationUtils,
-				eventBus, torSocketFactory, backoffFactory, resourceProvider,
+				eventBus, torSocketFactory, resourceProvider,
 				circumventionProvider, batteryManager, clock, crypto,
 				torDirectory, torSocksPort, torControlPort);
 	}
@@ -67,13 +64,13 @@ public class WindowsTorPluginFactory extends TorPluginFactory {
 	}
 
 	@Override
-	TorPlugin createPluginInstance(Backoff backoff,
-			TorRendezvousCrypto torRendezvousCrypto, PluginCallback callback,
+	TorPlugin createPluginInstance(TorRendezvousCrypto torRendezvousCrypto,
+			PluginCallback callback,
 			String architecture) {
 		return new WindowsTorPlugin(ioExecutor, wakefulIoExecutor,
 				networkManager, locationUtils, torSocketFactory, clock,
 				resourceProvider, circumventionProvider, batteryManager,
-				backoff, torRendezvousCrypto, callback, architecture,
+				torRendezvousCrypto, callback, architecture,
 				MAX_LATENCY, MAX_IDLE_TIME, torDirectory, torSocksPort,
 				torControlPort);
 	}

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

@@ -8,7 +8,6 @@ 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.BackoffFactory;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.api.system.LocationUtils;
@@ -110,8 +109,6 @@ public class BridgeTest extends BrambleTestCase {
 	@Inject
 	EventBus eventBus;
 	@Inject
-	BackoffFactory backoffFactory;
-	@Inject
 	Clock clock;
 	@Inject
 	CryptoComponent crypto;
@@ -166,9 +163,8 @@ public class BridgeTest extends BrambleTestCase {
 		};
 		factory = new UnixTorPluginFactory(ioExecutor, wakefulIoExecutor,
 				networkManager, locationUtils, eventBus, torSocketFactory,
-				backoffFactory, resourceProvider, bridgeProvider,
-				batteryManager, clock, crypto, torDir,
-				SOCKS_PORT, CONTROL_PORT);
+				resourceProvider, bridgeProvider, batteryManager, clock,
+				crypto, torDir, SOCKS_PORT, CONTROL_PORT);
 	}
 
 	@After

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

@@ -43,6 +43,10 @@ public class TestPluginCallback implements PluginCallback {
 	public void pluginStateChanged(State state) {
 	}
 
+	@Override
+	public void pollingIntervalDecreased() {
+	}
+
 	@Override
 	public void handleConnection(DuplexTransportConnection c) {
 	}