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

-package org.briarproject.bramble.plugin.droidtooth;
+package org.briarproject.bramble.plugin.bluetooth;
 
-import android.content.Context;
+import android.app.Application;
+import android.bluetooth.BluetoothSocket;
 
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.android.dontkillmelib.wakelock.AndroidWakeLockManager;
+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.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.DuplexPluginCallback;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPluginFactory;
 import org.briarproject.bramble.api.system.AndroidExecutor;
+import org.briarproject.bramble.api.system.Clock;
+import org.briarproject.bramble.api.system.WakefulIoExecutor;
+import org.briarproject.nullsafety.NotNullByDefault;
 
 import java.security.SecureRandom;
 import java.util.concurrent.Executor;
 
 import javax.annotation.concurrent.Immutable;
+import javax.inject.Inject;
 
 import static org.briarproject.bramble.api.plugin.BluetoothConstants.ID;
 
 @Immutable
 @NotNullByDefault
-public class DroidtoothPluginFactory implements DuplexPluginFactory {
+public class AndroidBluetoothPluginFactory implements DuplexPluginFactory {
 
 	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 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 DroidtoothPluginFactory(Executor ioExecutor,
-			AndroidExecutor androidExecutor, Context appContext,
-			SecureRandom secureRandom, BackoffFactory backoffFactory) {
+	@Inject
+	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.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;
 	}
 
@@ -49,15 +75,24 @@ public class DroidtoothPluginFactory implements DuplexPluginFactory {
 	}
 
 	@Override
-	public int getMaxLatency() {
+	public long getMaxLatency() {
 		return MAX_LATENCY;
 	}
 
 	@Override
-	public DuplexPlugin createPlugin(DuplexPluginCallback callback) {
+	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);
-		return new DroidtoothPlugin(ioExecutor, androidExecutor, appContext,
-				secureRandom, backoff, callback, MAX_LATENCY);
+		AndroidBluetoothPlugin plugin = new AndroidBluetoothPlugin(
+				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

+package org.briarproject.bramble.plugin.bluetooth;
+
+import android.bluetooth.BluetoothSocket;
+
+import org.briarproject.android.dontkillmelib.wakelock.AndroidWakeLock;
+import org.briarproject.android.dontkillmelib.wakelock.AndroidWakeLockManager;
+import org.briarproject.bramble.api.io.TimeoutMonitor;
+import org.briarproject.bramble.api.plugin.Plugin;
+import org.briarproject.bramble.api.plugin.duplex.AbstractDuplexTransportConnection;
+import org.briarproject.nullsafety.NotNullByDefault;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+
+import static org.briarproject.bramble.api.plugin.BluetoothConstants.PROP_ADDRESS;
+import static org.briarproject.bramble.util.AndroidUtils.isValidBluetoothAddress;
+
+@NotNullByDefault
+class AndroidBluetoothTransportConnection
+		extends AbstractDuplexTransportConnection {
+
+	private final BluetoothConnectionLimiter connectionLimiter;
+	private final BluetoothSocket socket;
+	private final InputStream in;
+	private final AndroidWakeLock wakeLock;
+
+	AndroidBluetoothTransportConnection(Plugin plugin,
+			BluetoothConnectionLimiter connectionLimiter,
+			AndroidWakeLockManager wakeLockManager,
+			TimeoutMonitor timeoutMonitor,
+			BluetoothSocket socket) throws IOException {
+		super(plugin);
+		this.connectionLimiter = connectionLimiter;
+		this.socket = socket;
+		InputStream socketIn = socket.getInputStream();
+		if (socketIn == null) throw new IOException();
+		in = timeoutMonitor.createTimeoutInputStream(socketIn,
+				plugin.getMaxIdleTime() * 2L);
+		wakeLock = wakeLockManager.createWakeLock("BluetoothConnection");
+		wakeLock.acquire();
+		String address = socket.getRemoteDevice().getAddress();
+		if (isValidBluetoothAddress(address)) remote.put(PROP_ADDRESS, address);
+	}
+
+	@Override
+	protected InputStream getInputStream() {
+		return in;
+	}
+
+	@Override
+	protected OutputStream getOutputStream() throws IOException {
+		OutputStream socketOut = socket.getOutputStream();
+		if (socketOut == null) throw new IOException();
+		return socketOut;
+	}
+
+	@Override
+	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/droidtooth/DroidtoothTransportConnection.java

-package org.briarproject.bramble.plugin.droidtooth;
-
-import android.bluetooth.BluetoothSocket;
-
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.plugin.Plugin;
-import org.briarproject.bramble.api.plugin.duplex.AbstractDuplexTransportConnection;
-
-import java.io.IOException;
-import java.io.InputStream;
-import java.io.OutputStream;
-
-@NotNullByDefault
-class DroidtoothTransportConnection extends AbstractDuplexTransportConnection {
-
-	private final BluetoothSocket socket;
-
-	DroidtoothTransportConnection(Plugin plugin, BluetoothSocket socket) {
-		super(plugin);
-		this.socket = socket;
-	}
-
-	@Override
-	protected InputStream getInputStream() throws IOException {
-		return socket.getInputStream();
-	}
-
-	@Override
-	protected OutputStream getOutputStream() throws IOException {
-		return socket.getOutputStream();
-	}
-
-	@Override
-	protected void closeConnection(boolean exception) throws IOException {
-		socket.close();
-	}
-}

bramble-android/src/main/java/org/briarproject/bramble/plugin/file/AndroidRemovableDrivePlugin.java

+package org.briarproject.bramble.plugin.file;
+
+import android.app.Application;
+import android.net.Uri;
+
+import org.briarproject.bramble.api.plugin.PluginCallback;
+import org.briarproject.bramble.api.properties.TransportProperties;
+import org.briarproject.nullsafety.NotNullByDefault;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+
+import javax.annotation.concurrent.Immutable;
+
+import static org.briarproject.bramble.api.plugin.file.RemovableDriveConstants.PROP_URI;
+import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
+
+@Immutable
+@NotNullByDefault
+class AndroidRemovableDrivePlugin extends RemovableDrivePlugin {
+
+	private final Application app;
+
+	AndroidRemovableDrivePlugin(Application app, PluginCallback callback,
+			long maxLatency) {
+		super(callback, maxLatency);
+		this.app = app;
+	}
+
+	@Override
+	InputStream openInputStream(TransportProperties p) throws IOException {
+		String uri = p.get(PROP_URI);
+		if (isNullOrEmpty(uri)) throw new IllegalArgumentException();
+		try {
+			return app.getContentResolver().openInputStream(Uri.parse(uri));
+		} catch (SecurityException e) {
+			throw new IOException(e);
+		}
+	}
+
+	@Override
+	OutputStream openOutputStream(TransportProperties p) throws IOException {
+		String uri = p.get(PROP_URI);
+		if (isNullOrEmpty(uri)) throw new IllegalArgumentException();
+		try {
+			return app.getContentResolver()
+					.openOutputStream(Uri.parse(uri), "wt");
+		} catch (SecurityException e) {
+			throw new IOException(e);
+		}
+	}
+}

bramble-android/src/main/java/org/briarproject/bramble/plugin/file/AndroidRemovableDrivePluginFactory.java

+package org.briarproject.bramble.plugin.file;
+
+import android.app.Application;
+
+import org.briarproject.bramble.api.plugin.PluginCallback;
+import org.briarproject.bramble.api.plugin.TransportId;
+import org.briarproject.bramble.api.plugin.simplex.SimplexPlugin;
+import org.briarproject.bramble.api.plugin.simplex.SimplexPluginFactory;
+import org.briarproject.nullsafety.NotNullByDefault;
+
+import javax.annotation.Nullable;
+import javax.annotation.concurrent.Immutable;
+import javax.inject.Inject;
+
+import static java.util.concurrent.TimeUnit.DAYS;
+import static org.briarproject.bramble.api.plugin.file.RemovableDriveConstants.ID;
+
+@Immutable
+@NotNullByDefault
+public class AndroidRemovableDrivePluginFactory implements
+		SimplexPluginFactory {
+
+	private static final long MAX_LATENCY = DAYS.toMillis(28);
+
+	private final Application app;
+
+	@Inject
+	AndroidRemovableDrivePluginFactory(Application app) {
+		this.app = app;
+	}
+
+	@Override
+	public TransportId getId() {
+		return ID;
+	}
+
+	@Override
+	public long getMaxLatency() {
+		return MAX_LATENCY;
+	}
+
+	@Nullable
+	@Override
+	public SimplexPlugin createPlugin(PluginCallback callback) {
+		return new AndroidRemovableDrivePlugin(app, callback, MAX_LATENCY);
+	}
+}

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

 package org.briarproject.bramble.plugin.tcp;
 
-import android.content.BroadcastReceiver;
-import android.content.Context;
-import android.content.Intent;
-import android.content.IntentFilter;
+import android.app.Application;
 import android.net.ConnectivityManager;
-import android.net.NetworkInfo;
+import android.net.LinkAddress;
+import android.net.LinkProperties;
+import android.net.Network;
+import android.net.NetworkCapabilities;
+import android.net.wifi.WifiInfo;
+import android.net.wifi.WifiManager;
 
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.PoliteExecutor;
+import org.briarproject.bramble.api.Pair;
+import org.briarproject.bramble.api.event.Event;
+import org.briarproject.bramble.api.network.event.NetworkStatusEvent;
 import org.briarproject.bramble.api.plugin.Backoff;
-import org.briarproject.bramble.api.plugin.duplex.DuplexPluginCallback;
+import org.briarproject.bramble.api.plugin.PluginCallback;
+import org.briarproject.bramble.api.settings.Settings;
+import org.briarproject.nullsafety.NotNullByDefault;
 
+import java.io.IOException;
+import java.net.InetAddress;
+import java.net.InterfaceAddress;
+import java.net.NetworkInterface;
+import java.net.Socket;
+import java.net.SocketException;
+import java.net.UnknownHostException;
+import java.util.List;
 import java.util.concurrent.Executor;
 import java.util.logging.Logger;
+import java.util.regex.Pattern;
 
 import javax.annotation.Nullable;
+import javax.net.SocketFactory;
 
 import static android.content.Context.CONNECTIVITY_SERVICE;
-import static android.net.ConnectivityManager.CONNECTIVITY_ACTION;
-import static android.net.ConnectivityManager.TYPE_WIFI;
+import static android.content.Context.WIFI_SERVICE;
+import static android.net.NetworkCapabilities.TRANSPORT_WIFI;
+import static java.util.Collections.emptyList;
+import static java.util.Collections.list;
+import static java.util.Collections.singletonList;
+import static java.util.logging.Level.WARNING;
+import static java.util.logging.Logger.getLogger;
+import static org.briarproject.bramble.api.plugin.LanTcpConstants.DEFAULT_PREF_PLUGIN_ENABLE;
+import static org.briarproject.bramble.api.plugin.Plugin.State.ACTIVE;
+import static org.briarproject.bramble.api.plugin.Plugin.State.INACTIVE;
+import static org.briarproject.bramble.util.IoUtils.tryToClose;
+import static org.briarproject.bramble.util.LogUtils.logException;
+import static org.briarproject.bramble.util.NetworkUtils.getNetworkInterfaces;
+import static org.briarproject.nullsafety.NullSafety.requireNonNull;
 
 @NotNullByDefault
 class AndroidLanTcpPlugin extends LanTcpPlugin {
 
 	private static final Logger LOG =
-			Logger.getLogger(AndroidLanTcpPlugin.class.getName());
+			getLogger(AndroidLanTcpPlugin.class.getName());
 
-	private final Context appContext;
+	/**
+	 * The interface name is used as a heuristic for deciding whether the
+	 * device is providing a wifi access point.
+	 */
+	private static final Pattern AP_INTERFACE_NAME =
+			Pattern.compile("^(wlan|ap|p2p)[-0-9]");
 
+	private final Executor connectionStatusExecutor;
+	private final ConnectivityManager connectivityManager;
 	@Nullable
-	private volatile BroadcastReceiver networkStateReceiver = null;
+	private final WifiManager wifiManager;
 
-	AndroidLanTcpPlugin(Executor ioExecutor, Backoff backoff,
-			Context appContext, DuplexPluginCallback callback, int maxLatency,
-			int maxIdleTime) {
-		super(ioExecutor, backoff, callback, maxLatency, maxIdleTime);
-		this.appContext = appContext;
+	private volatile SocketFactory socketFactory;
+
+	AndroidLanTcpPlugin(Executor ioExecutor,
+			Executor wakefulIoExecutor,
+			Application app,
+			Backoff backoff,
+			PluginCallback callback,
+			long 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)
+				requireNonNull(app.getSystemService(CONNECTIVITY_SERVICE));
+		wifiManager = (WifiManager) app.getSystemService(WIFI_SERVICE);
+		socketFactory = SocketFactory.getDefault();
 	}
 
 	@Override
 	public void start() {
 		if (used.getAndSet(true)) throw new IllegalStateException();
-		running = true;
-		// Register to receive network status events
-		networkStateReceiver = new NetworkStateReceiver();
-		IntentFilter filter = new IntentFilter(CONNECTIVITY_ACTION);
-		appContext.registerReceiver(networkStateReceiver, filter);
+		initialisePortProperty();
+		Settings settings = callback.getSettings();
+		state.setStarted(settings.getBoolean(PREF_PLUGIN_ENABLE,
+				DEFAULT_PREF_PLUGIN_ENABLE));
+		updateConnectionStatus();
 	}
 
 	@Override
-	public void stop() {
-		running = false;
-		if (networkStateReceiver != null)
-			appContext.unregisterReceiver(networkStateReceiver);
-		tryToClose(socket);
+	protected Socket createSocket() throws IOException {
+		return socketFactory.createSocket();
+	}
+
+	@Override
+	protected List<InetAddress> getUsableLocalInetAddresses(boolean ipv4) {
+		InetAddress addr = getWifiAddress(ipv4);
+		return addr == null ? emptyList() : singletonList(addr);
+	}
+
+	@Nullable
+	private InetAddress getWifiAddress(boolean ipv4) {
+		Pair<InetAddress, Boolean> wifi = getWifiIpv4Address();
+		if (ipv4) return wifi == null ? null : wifi.getFirst();
+		// If there's no wifi IPv4 address, we might be a client on an
+		// IPv6-only wifi network. We can only detect this on API 21+
+		if (wifi == null) {
+			return getWifiClientIpv6Address();
+		}
+		// Use the wifi IPv4 address to determine which interface's IPv6
+		// address we should return (if the interface has a suitable address)
+		return getIpv6AddressForInterface(wifi.getFirst());
+	}
+
+	/**
+	 * Returns a {@link Pair} where the first element is the IPv4 address of
+	 * the wifi interface and the second element is true if this device is
+	 * providing an access point, or false if this device is a client. Returns
+	 * null if this device isn't connected to wifi as an access point or client.
+	 */
+	@Nullable
+	private Pair<InetAddress, Boolean> getWifiIpv4Address() {
+		if (wifiManager == null) return null;
+		// If we're connected to a wifi network, return its address
+		WifiInfo info = wifiManager.getConnectionInfo();
+		if (info != null && info.getIpAddress() != 0) {
+			return new Pair<>(intToInetAddress(info.getIpAddress()), false);
+		}
+		// If we're providing an access point, return its address
+		for (NetworkInterface iface : getNetworkInterfaces()) {
+			if (AP_INTERFACE_NAME.matcher(iface.getName()).find()) {
+				for (InterfaceAddress ifAddr : iface.getInterfaceAddresses()) {
+					if (isPossibleWifiApInterface(ifAddr)) {
+						return new Pair<>(ifAddr.getAddress(), true);
+					}
+				}
+			}
+		}
+		// Not connected to wifi
+		return null;
+	}
+
+	/**
+	 * Returns true if the given address may belong to an interface providing
+	 * a wifi access point (including wifi direct legacy mode access points).
+	 * <p>
+	 * This method may return true for wifi client interfaces as well, but
+	 * we've already checked for a wifi client connection above.
+	 */
+	private boolean isPossibleWifiApInterface(InterfaceAddress ifAddr) {
+		if (ifAddr.getNetworkPrefixLength() != 24) return false;
+		byte[] ip = ifAddr.getAddress().getAddress();
+		return ip.length == 4
+				&& ip[0] == (byte) 192
+				&& ip[1] == (byte) 168;
 	}
 
-	private class NetworkStateReceiver extends BroadcastReceiver {
-
-		@Override
-		public void onReceive(Context ctx, Intent i) {
-			if (!running) return;
-			Object o = ctx.getSystemService(CONNECTIVITY_SERVICE);
-			ConnectivityManager cm = (ConnectivityManager) o;
-			NetworkInfo net = cm.getActiveNetworkInfo();
-			if (net != null && net.getType() == TYPE_WIFI && net.isConnected()) {
-				LOG.info("Connected to Wi-Fi");
-				if (socket == null || socket.isClosed()) bind();
+	/**
+	 * Returns a link-local IPv6 address for the wifi client interface, or null
+	 * if there's no such interface or it doesn't have a suitable address.
+	 */
+	@Nullable
+	private InetAddress getWifiClientIpv6Address() {
+		// https://issuetracker.google.com/issues/175055271
+		try {
+			for (Network net : connectivityManager.getAllNetworks()) {
+				NetworkCapabilities caps =
+						connectivityManager.getNetworkCapabilities(net);
+				if (caps == null || !caps.hasTransport(TRANSPORT_WIFI)) {
+					continue;
+				}
+				LinkProperties props =
+						connectivityManager.getLinkProperties(net);
+				if (props == null) continue;
+				for (LinkAddress linkAddress : props.getLinkAddresses()) {
+					InetAddress addr = linkAddress.getAddress();
+					if (isIpv6LinkLocalAddress(addr)) return addr;
+				}
+			}
+		} catch (SecurityException e) {
+			logException(LOG, WARNING, e);
+		}
+		return null;
+	}
+
+	/**
+	 * Returns a link-local IPv6 address for the interface with the given IPv4
+	 * address, or null if the interface doesn't have a suitable address.
+	 */
+	@Nullable
+	private InetAddress getIpv6AddressForInterface(InetAddress ipv4) {
+		try {
+			// We may get an NPE from getByInetAddress() on Android 11
+			NetworkInterface iface = NetworkInterface.getByInetAddress(ipv4);
+			if (iface == null) return null;
+			for (InetAddress addr : list(iface.getInetAddresses())) {
+				if (isIpv6LinkLocalAddress(addr)) return addr;
+			}
+			// No suitable address
+			return null;
+		} catch (SocketException | NullPointerException e) {
+			logException(LOG, WARNING, e);
+			return null;
+		}
+	}
+
+	private InetAddress intToInetAddress(int ip) {
+		byte[] ipBytes = new byte[4];
+		ipBytes[0] = (byte) (ip & 0xFF);
+		ipBytes[1] = (byte) ((ip >> 8) & 0xFF);
+		ipBytes[2] = (byte) ((ip >> 16) & 0xFF);
+		ipBytes[3] = (byte) ((ip >> 24) & 0xFF);
+		try {
+			return InetAddress.getByAddress(ipBytes);
+		} catch (UnknownHostException e) {
+			// Should only be thrown if address has illegal length
+			throw new AssertionError(e);
+		}
+	}
+
+	// On API 21 and later, a socket that is not created with the wifi
+	// network's socket factory may try to connect via another network
+	private SocketFactory getSocketFactory() {
+		// https://issuetracker.google.com/issues/175055271
+		try {
+			for (Network net : connectivityManager.getAllNetworks()) {
+				NetworkCapabilities caps =
+						connectivityManager.getNetworkCapabilities(net);
+				if (caps != null && caps.hasTransport(TRANSPORT_WIFI)) {
+					return net.getSocketFactory();
+				}
+			}
+		} catch (SecurityException e) {
+			logException(LOG, WARNING, e);
+		}
+		LOG.warning("Could not find suitable socket factory");
+		return SocketFactory.getDefault();
+	}
+
+	@Override
+	public void eventOccurred(Event e) {
+		super.eventOccurred(e);
+		if (e instanceof NetworkStatusEvent) updateConnectionStatus();
+	}
+
+	private void updateConnectionStatus() {
+		connectionStatusExecutor.execute(() -> {
+			State s = getState();
+			if (s != ACTIVE && s != INACTIVE) return;
+			Pair<InetAddress, Boolean> wifi = getPreferredWifiAddress();
+			if (wifi == null) {
+				LOG.info("Not connected to wifi");
+				socketFactory = SocketFactory.getDefault();
+				// Server sockets may not have been closed automatically when
+				// interface was taken down. If any sockets are open, closing
+				// them here will cause the sockets to be cleared and the state
+				// to be updated in acceptContactConnections()
+				if (s == ACTIVE) {
+					LOG.info("Closing server sockets");
+					tryToClose(state.getServerSocket(true), LOG, WARNING);
+					tryToClose(state.getServerSocket(false), LOG, WARNING);
+				}
+			} else if (wifi.getSecond()) {
+				LOG.info("Providing wifi hotspot");
+				// There's no corresponding Network object and thus no way
+				// to get a suitable socket factory, so we won't be able to
+				// make outgoing connections on API 21+ if another network
+				// has internet access
+				socketFactory = SocketFactory.getDefault();
+				bind();
 			} else {
-				LOG.info("Not connected to Wi-Fi");
-				tryToClose(socket);
+				LOG.info("Connected to wifi");
+				socketFactory = getSocketFactory();
+				bind();
 			}
+		});
+	}
+
+	/**
+	 * Returns a {@link Pair} where the first element is an IP address (IPv4 if
+	 * available, otherwise IPv6) of the wifi interface and the second element
+	 * is true if this device is providing an access point, or false if this
+	 * device is a client. Returns null if this device isn't connected to wifi
+	 * as an access point or client.
+	 */
+	@Nullable
+	private Pair<InetAddress, Boolean> getPreferredWifiAddress() {
+		Pair<InetAddress, Boolean> wifi = getWifiIpv4Address();
+		// If there's no wifi IPv4 address, we might be a client on an
+		// IPv6-only wifi network. We can only detect this on API 21+
+		if (wifi == null) {
+			InetAddress ipv6 = getWifiClientIpv6Address();
+			if (ipv6 != null) return new Pair<>(ipv6, false);
 		}
+		return wifi;
 	}
-}
+}
\ No newline at end of file

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

 package org.briarproject.bramble.plugin.tcp;
 
-import android.content.Context;
+import android.app.Application;
 
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.event.EventBus;
+import org.briarproject.bramble.api.lifecycle.IoExecutor;
 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.DuplexPluginCallback;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPluginFactory;
+import org.briarproject.bramble.api.system.WakefulIoExecutor;
+import org.briarproject.nullsafety.NotNullByDefault;
 
 import java.util.concurrent.Executor;
 
 import javax.annotation.concurrent.Immutable;
+import javax.inject.Inject;
 
 import static org.briarproject.bramble.api.plugin.LanTcpConstants.ID;
 
@@ -20,21 +24,29 @@ import static org.briarproject.bramble.api.plugin.LanTcpConstants.ID;
 @NotNullByDefault
 public class AndroidLanTcpPluginFactory implements DuplexPluginFactory {
 
-	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 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;
-	private final Context appContext;
+	private final Application app;
 
-	public AndroidLanTcpPluginFactory(Executor ioExecutor,
-			BackoffFactory backoffFactory, Context appContext) {
+	@Inject
+	AndroidLanTcpPluginFactory(@IoExecutor Executor ioExecutor,
+			@WakefulIoExecutor Executor wakefulIoExecutor,
+			EventBus eventBus,
+			BackoffFactory backoffFactory,
+			Application app) {
 		this.ioExecutor = ioExecutor;
+		this.wakefulIoExecutor = wakefulIoExecutor;
+		this.eventBus = eventBus;
 		this.backoffFactory = backoffFactory;
-		this.appContext = appContext;
+		this.app = app;
 	}
 
 	@Override
@@ -43,15 +55,18 @@ public class AndroidLanTcpPluginFactory implements DuplexPluginFactory {
 	}
 
 	@Override
-	public int getMaxLatency() {
+	public long getMaxLatency() {
 		return MAX_LATENCY;
 	}
 
 	@Override
-	public DuplexPlugin createPlugin(DuplexPluginCallback callback) {
+	public DuplexPlugin createPlugin(PluginCallback callback) {
 		Backoff backoff = backoffFactory.createBackoff(MIN_POLLING_INTERVAL,
 				MAX_POLLING_INTERVAL, BACKOFF_BASE);
-		return new AndroidLanTcpPlugin(ioExecutor, backoff, appContext,
-				callback, MAX_LATENCY, MAX_IDLE_TIME);
+		AndroidLanTcpPlugin plugin = new AndroidLanTcpPlugin(ioExecutor,
+				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/AndroidTorPluginFactory.java

+package org.briarproject.bramble.plugin.tor;
+
+import android.app.Application;
+
+import org.briarproject.android.dontkillmelib.wakelock.AndroidWakeLockManager;
+import org.briarproject.bramble.api.battery.BatteryManager;
+import org.briarproject.bramble.api.crypto.CryptoComponent;
+import org.briarproject.bramble.api.event.EventBus;
+import org.briarproject.bramble.api.event.EventExecutor;
+import org.briarproject.bramble.api.lifecycle.IoExecutor;
+import org.briarproject.bramble.api.network.NetworkManager;
+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;
+import org.briarproject.bramble.api.plugin.TorSocksPort;
+import org.briarproject.bramble.api.system.Clock;
+import org.briarproject.bramble.api.system.WakefulIoExecutor;
+import org.briarproject.nullsafety.NotNullByDefault;
+import org.briarproject.onionwrapper.AndroidTorWrapper;
+import org.briarproject.onionwrapper.CircumventionProvider;
+import org.briarproject.onionwrapper.LocationUtils;
+import org.briarproject.onionwrapper.TorWrapper;
+
+import java.io.File;
+import java.util.concurrent.Executor;
+
+import javax.annotation.Nullable;
+import javax.annotation.concurrent.Immutable;
+import javax.inject.Inject;
+import javax.net.SocketFactory;
+
+import static org.briarproject.bramble.util.AndroidUtils.getSupportedArchitectures;
+
+@Immutable
+@NotNullByDefault
+public class AndroidTorPluginFactory extends TorPluginFactory {
+
+	private final Application app;
+	private final AndroidWakeLockManager wakeLockManager;
+
+	@Inject
+	AndroidTorPluginFactory(@IoExecutor Executor ioExecutor,
+			@EventExecutor Executor eventExecutor,
+			@WakefulIoExecutor Executor wakefulIoExecutor,
+			NetworkManager networkManager,
+			LocationUtils locationUtils,
+			EventBus eventBus,
+			SocketFactory torSocketFactory,
+			BackoffFactory backoffFactory,
+			CircumventionProvider circumventionProvider,
+			BatteryManager batteryManager,
+			Clock clock,
+			CryptoComponent crypto,
+			@TorDirectory File torDirectory,
+			@TorSocksPort int torSocksPort,
+			@TorControlPort int torControlPort,
+			Application app,
+			AndroidWakeLockManager wakeLockManager) {
+		super(ioExecutor, eventExecutor, wakefulIoExecutor, networkManager,
+				locationUtils, eventBus, torSocketFactory, backoffFactory,
+				circumventionProvider, batteryManager, clock, crypto,
+				torDirectory, torSocksPort, torControlPort);
+		this.app = app;
+		this.wakeLockManager = wakeLockManager;
+	}
+
+	@Nullable
+	@Override
+	String getArchitectureForTorBinary() {
+		for (String abi : getSupportedArchitectures()) {
+			if (abi.startsWith("x86_64")) return "x86_64_pie";
+			else if (abi.startsWith("x86")) return "x86_pie";
+			else if (abi.startsWith("arm64")) return "arm64_pie";
+			else if (abi.startsWith("armeabi")) return "arm_pie";
+		}
+		return null;
+	}
+
+	@Override
+	TorPlugin createPluginInstance(Backoff backoff,
+			TorRendezvousCrypto torRendezvousCrypto, PluginCallback callback,
+			String architecture) {
+		TorWrapper tor = new AndroidTorWrapper(app, wakeLockManager,
+				ioExecutor, eventExecutor, architecture, torDirectory,
+				torSocksPort, torControlPort);
+		return new TorPlugin(ioExecutor, wakefulIoExecutor,
+				networkManager, locationUtils, torSocketFactory,
+				circumventionProvider, batteryManager, backoff,
+				torRendezvousCrypto, tor, callback, MAX_LATENCY,
+				MAX_IDLE_TIME);
+	}
+}

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

-package org.briarproject.bramble.plugin.tor;
-
-import java.util.Arrays;
-import java.util.HashSet;
-import java.util.Set;
-
-class TorNetworkMetadata {
-
-	// See https://en.wikipedia.org/wiki/ISO_3166-1_alpha-2
-	// and https://trac.torproject.org/projects/tor/wiki/doc/OONI/censorshipwiki
-	// TODO: get a more complete list
-	private static final Set<String> BLOCKED_IN_COUNTRIES =
-			new HashSet<>(Arrays.asList("CN", "IR", "SY", "ZZ"));
-
-	static boolean isTorProbablyBlocked(String countryCode) {
-		return BLOCKED_IN_COUNTRIES.contains(countryCode);
-	}
-}

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

+package org.briarproject.bramble.system;
+
+import org.briarproject.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

+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/AndroidExecutorImpl.java

@@ -27,14 +27,11 @@ class AndroidExecutorImpl implements AndroidExecutor {
 	@Inject
 	AndroidExecutorImpl(Application app) {
 		uiHandler = new Handler(app.getApplicationContext().getMainLooper());
-		loop = new Runnable() {
-			@Override
-			public void run() {
-				Looper.prepare();
-				backgroundHandler = new Handler();
-				startLatch.countDown();
-				Looper.loop();
-			}
+		loop = () -> {
+			Looper.prepare();
+			backgroundHandler = new Handler();
+			startLatch.countDown();
+			Looper.loop();
 		};
 	}
 

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

-package org.briarproject.bramble.system;
-
-import android.annotation.SuppressLint;
-import android.app.Application;
-import android.content.Context;
-import android.telephony.TelephonyManager;
-import android.text.TextUtils;
-
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.system.LocationUtils;
-
-import java.util.Locale;
-import java.util.logging.Logger;
-
-import javax.inject.Inject;
-
-import static android.content.Context.TELEPHONY_SERVICE;
-
-@NotNullByDefault
-class AndroidLocationUtils implements LocationUtils {
-
-	private static final Logger LOG =
-			Logger.getLogger(AndroidLocationUtils.class.getName());
-
-	private final Context appContext;
-
-	@Inject
-	AndroidLocationUtils(Application app) {
-		appContext = app.getApplicationContext();
-	}
-
-	/**
-	 * This guesses the current country from the first of these sources that
-	 * succeeds (also in order of likelihood of being correct):
-	 *
-	 * <ul>
-	 * <li>Phone network. This works even when no SIM card is inserted, or a
-	 *     foreign SIM card is inserted.</li>
-	 * <li>SIM card. This is only an heuristic and assumes the user is not
-	 *     roaming.</li>
-	 * <li>User locale. This is an even worse heuristic.</li>
-	 * </ul>
-	 *
-	 * Note: this is very similar to <a href="https://android.googlesource.com/platform/frameworks/base/+/cd92588%5E/location/java/android/location/CountryDetector.java">
-	 * this API</a> except it seems that Google doesn't want us to use it for
-	 * some reason - both that class and {@code Context.COUNTRY_CODE} are
-	 * annotated {@code @hide}.
-	 */
-	@Override
-	@SuppressLint("DefaultLocale")
-	public String getCurrentCountry() {
-		String countryCode = getCountryFromPhoneNetwork();
-		if (!TextUtils.isEmpty(countryCode)) return countryCode.toUpperCase();
-		LOG.info("Falling back to SIM card country");
-		countryCode = getCountryFromSimCard();
-		if (!TextUtils.isEmpty(countryCode)) return countryCode.toUpperCase();
-		LOG.info("Falling back to user-defined locale");
-		return Locale.getDefault().getCountry();
-	}
-
-	private String getCountryFromPhoneNetwork() {
-		Object o = appContext.getSystemService(TELEPHONY_SERVICE);
-		TelephonyManager tm = (TelephonyManager) o;
-		return tm.getNetworkCountryIso();
-	}
-
-	private String getCountryFromSimCard() {
-		Object o = appContext.getSystemService(TELEPHONY_SERVICE);
-		TelephonyManager tm = (TelephonyManager) o;
-		return tm.getSimCountryIso();
-	}
-}

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

+package org.briarproject.bramble.system;
+
+import android.app.Application;
+import android.content.Context;
+import android.content.res.Resources;
+
+import org.briarproject.bramble.api.system.ResourceProvider;
+import org.briarproject.nullsafety.NotNullByDefault;
+
+import java.io.InputStream;
+
+import javax.inject.Inject;
+
+@NotNullByDefault
+class AndroidResourceProvider implements ResourceProvider {
+
+	private final Context appContext;
+
+	@Inject
+	AndroidResourceProvider(Application app) {
+		this.appContext = app.getApplicationContext();
+	}
+
+	@Override
+	public InputStream getResourceInputStream(String name, String extension) {
+		Resources res = appContext.getResources();
+		// extension is ignored on Android, resources are retrieved without it
+		int resId =
+				res.getIdentifier(name, "raw", appContext.getPackageName());
+		return res.openRawResource(resId);
+	}
+}

bramble-android/src/main/java/org/briarproject/bramble/system/AndroidSeedProvider.java → bramble-android/src/main/java/org/briarproject/bramble/system/AndroidSecureRandomProvider.java

 package org.briarproject.bramble.system;
 
+import android.annotation.SuppressLint;
 import android.app.Application;
+import android.bluetooth.BluetoothAdapter;
+import android.bluetooth.BluetoothDevice;
 import android.content.ContentResolver;
 import android.content.Context;
-import android.os.Build;
+import android.os.Parcel;
+import android.os.StrictMode;
 import android.provider.Settings;
 
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.nullsafety.NotNullByDefault;
 
 import java.io.DataOutputStream;
 import java.io.IOException;
+import java.util.Set;
 
 import javax.annotation.concurrent.Immutable;
 import javax.inject.Inject;
 
+import static android.os.Build.FINGERPRINT;
+import static android.os.Build.SERIAL;
+import static android.os.Build.VERSION.SDK_INT;
+import static android.os.Process.myPid;
+import static android.os.Process.myTid;
+import static android.os.Process.myUid;
 import static android.provider.Settings.Secure.ANDROID_ID;
 
 @Immutable
 @NotNullByDefault
-class AndroidSeedProvider extends LinuxSeedProvider {
+class AndroidSecureRandomProvider extends UnixSecureRandomProvider {
 
 	private final Context appContext;
 
 	@Inject
-	AndroidSeedProvider(Application app) {
+	AndroidSecureRandomProvider(Application app) {
 		appContext = app.getApplicationContext();
 	}
 
+	@SuppressLint("HardwareIds")
 	@Override
-	void writeToEntropyPool(DataOutputStream out) throws IOException {
-		out.writeInt(android.os.Process.myPid());
-		out.writeInt(android.os.Process.myTid());
-		out.writeInt(android.os.Process.myUid());
-		if (Build.FINGERPRINT != null) out.writeUTF(Build.FINGERPRINT);
-		if (Build.SERIAL != null) out.writeUTF(Build.SERIAL);
+	protected void writeToEntropyPool(DataOutputStream out) throws IOException {
+		super.writeToEntropyPool(out);
+		out.writeInt(myPid());
+		out.writeInt(myTid());
+		out.writeInt(myUid());
+		if (FINGERPRINT != null) out.writeUTF(FINGERPRINT);
+		if (SERIAL != null) out.writeUTF(SERIAL);
 		ContentResolver contentResolver = appContext.getContentResolver();
 		String id = Settings.Secure.getString(contentResolver, ANDROID_ID);
 		if (id != null) out.writeUTF(id);
-		super.writeToEntropyPool(out);
+		// On API 31 and higher we need permission to access bonded devices
+		if (SDK_INT < 31) {
+			Parcel parcel = Parcel.obtain();
+			BluetoothAdapter bt = BluetoothAdapter.getDefaultAdapter();
+			if (bt != null) {
+				@SuppressLint("MissingPermission")
+				Set<BluetoothDevice> deviceSet = bt.getBondedDevices();
+				for (BluetoothDevice device : deviceSet)
+					parcel.writeParcelable(device, 0);
+			}
+			out.write(parcel.marshall());
+			parcel.recycle();
+		}
+	}
+
+	@Override
+	protected void writeSeed() {
+		// Silence strict mode
+		StrictMode.ThreadPolicy tp = StrictMode.allowThreadDiskWrites();
+		super.writeSeed();
+		StrictMode.setThreadPolicy(tp);
 	}
 }

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

@@ -2,9 +2,18 @@ package org.briarproject.bramble.system;
 
 import android.app.Application;
 
+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.LocationUtils;
-import org.briarproject.bramble.api.system.SeedProvider;
+import org.briarproject.bramble.api.system.ResourceProvider;
+import org.briarproject.bramble.api.system.SecureRandomProvider;
+import org.briarproject.onionwrapper.AndroidLocationUtilsFactory;
+import org.briarproject.onionwrapper.LocationUtils;
+
+import java.util.concurrent.Executor;
+import java.util.concurrent.RejectedExecutionHandler;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.ScheduledThreadPoolExecutor;
 
 import javax.inject.Singleton;
 
@@ -14,20 +23,53 @@ 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
-	SeedProvider provideSeedProvider(Application app) {
-		return new AndroidSeedProvider(app);
+	ScheduledExecutorService provideScheduledExecutorService(
+			LifecycleManager lifecycleManager) {
+		lifecycleManager.registerForShutdown(scheduledExecutorService);
+		return scheduledExecutorService;
 	}
 
 	@Provides
+	@Singleton
+	SecureRandomProvider provideSecureRandomProvider(
+			AndroidSecureRandomProvider provider) {
+		return provider;
+	}
+
+	@Provides
+	@Singleton
 	LocationUtils provideLocationUtils(Application app) {
-		return new AndroidLocationUtils(app);
+		return AndroidLocationUtilsFactory.createAndroidLocationUtils(app);
+	}
+
+	@Provides
+	@Singleton
+	AndroidExecutor provideAndroidExecutor(
+			AndroidExecutorImpl androidExecutor) {
+		return androidExecutor;
+	}
+
+	@Provides
+	@Singleton
+	@EventExecutor
+	Executor provideEventExecutor(AndroidExecutor androidExecutor) {
+		return androidExecutor::runOnUiThread;
 	}
 
 	@Provides
 	@Singleton
-	AndroidExecutor provideAndroidExecutor(Application app) {
-		return new AndroidExecutorImpl(app);
+	ResourceProvider provideResourceProvider(AndroidResourceProvider provider) {
+		return provider;
 	}
 }

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

+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.android.dontkillmelib.wakelock.AndroidWakeLockManager;
+import org.briarproject.bramble.api.Cancellable;
+import org.briarproject.bramble.api.lifecycle.Service;
+import org.briarproject.bramble.api.system.AlarmListener;
+import org.briarproject.bramble.api.system.TaskScheduler;
+import org.briarproject.bramble.api.system.Wakeful;
+import org.briarproject.nullsafety.NotNullByDefault;
+
+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;
+import static org.briarproject.bramble.util.AndroidUtils.getImmutableFlags;
+
+@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");
+		// Acquire the lock before scheduling the check to ensure the check
+		// doesn't access the task queue before the task has been added
+		ScheduledTask s;
+		synchronized (lock) {
+			Future<?> check = scheduleCheckForDueTasks(delay, unit);
+			s = new ScheduledTask(wakeful, dueMillis, check, cancelled);
+			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);
+	}
+
+	@GuardedBy("lock")
+	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,
+				getImmutableFlags(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;
+
+		private 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

+package org.briarproject.bramble.system;
+
+import android.app.Application;
+
+import org.briarproject.android.dontkillmelib.wakelock.AndroidWakeLockManager;
+import org.briarproject.bramble.api.lifecycle.LifecycleManager;
+import org.briarproject.bramble.api.system.AlarmListener;
+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;
+	}
+}