Implement backend for connect via bluetooth

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

@@ -59,8 +59,8 @@ import static org.briarproject.bramble.util.PrivacyUtils.scrubMacAddress;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
-class AndroidBluetoothPlugin
-		extends BluetoothPlugin<BluetoothSocket, BluetoothServerSocket> {
+class AndroidBluetoothPlugin extends
+		AbstractBluetoothPlugin<BluetoothSocket, BluetoothServerSocket> {
 
 	private static final Logger LOG =
 			getLogger(AndroidBluetoothPlugin.class.getName());
@@ -75,6 +75,7 @@ class AndroidBluetoothPlugin
 
 	// Non-null if the plugin started successfully
 	private volatile BluetoothAdapter adapter = null;
+	private volatile boolean stopDiscoverAndConnect;
 
 	AndroidBluetoothPlugin(BluetoothConnectionLimiter connectionLimiter,
 			BluetoothConnectionFactory<BluetoothSocket> connectionFactory,
@@ -187,22 +188,40 @@ class AndroidBluetoothPlugin
 	@Nullable
 	DuplexTransportConnection discoverAndConnect(String uuid) {
 		if (adapter == null) return null;
-		for (String address : discoverDevices()) {
-			try {
-				if (LOG.isLoggable(INFO))
-					LOG.info("Connecting to " + scrubMacAddress(address));
-				return connectTo(address, uuid);
-			} catch (IOException e) {
-				if (LOG.isLoggable(INFO)) {
-					LOG.info("Could not connect to "
-							+ scrubMacAddress(address));
+		if (!discoverSemaphore.tryAcquire()) {
+			LOG.info("Discover already running");
+			return null;
+		}
+		try {
+			stopDiscoverAndConnect = false;
+			for (String address : discoverDevices()) {
+				if (stopDiscoverAndConnect) {
+					break;
+				}
+				try {
+					if (LOG.isLoggable(INFO))
+						LOG.info("Connecting to " + scrubMacAddress(address));
+					return connectTo(address, uuid);
+				} catch (IOException e) {
+					if (LOG.isLoggable(INFO)) {
+						LOG.info("Could not connect to "
+								+ scrubMacAddress(address));
+					}
 				}
 			}
+		} finally {
+			discoverSemaphore.release();
 		}
 		LOG.info("Could not connect to any devices");
 		return null;
 	}
 
+	@Override
+	public void stopDiscoverAndConnect() {
+		stopDiscoverAndConnect = true;
+		adapter.cancelDiscovery();
+	}
+
 	private Collection<String> discoverDevices() {
 		List<String> addresses = new ArrayList<>();
 		BlockingQueue<Intent> intents = new LinkedBlockingQueue<>();

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

@@ -0,0 +1,623 @@
+package org.briarproject.bramble.plugin.bluetooth;
+
+import org.briarproject.bramble.api.FormatException;
+import org.briarproject.bramble.api.Multiset;
+import org.briarproject.bramble.api.Pair;
+import org.briarproject.bramble.api.data.BdfList;
+import org.briarproject.bramble.api.event.Event;
+import org.briarproject.bramble.api.event.EventListener;
+import org.briarproject.bramble.api.keyagreement.KeyAgreementConnection;
+import org.briarproject.bramble.api.keyagreement.KeyAgreementListener;
+import org.briarproject.bramble.api.keyagreement.event.KeyAgreementListeningEvent;
+import org.briarproject.bramble.api.keyagreement.event.KeyAgreementStoppedListeningEvent;
+import org.briarproject.bramble.api.lifecycle.IoExecutor;
+import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
+import org.briarproject.bramble.api.plugin.Backoff;
+import org.briarproject.bramble.api.plugin.ConnectionHandler;
+import org.briarproject.bramble.api.plugin.PluginCallback;
+import org.briarproject.bramble.api.plugin.PluginException;
+import org.briarproject.bramble.api.plugin.TransportId;
+import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
+import org.briarproject.bramble.api.properties.TransportProperties;
+import org.briarproject.bramble.api.properties.event.RemoteTransportPropertiesUpdatedEvent;
+import org.briarproject.bramble.api.rendezvous.KeyMaterialSource;
+import org.briarproject.bramble.api.rendezvous.RendezvousEndpoint;
+import org.briarproject.bramble.api.settings.Settings;
+import org.briarproject.bramble.api.settings.event.SettingsUpdatedEvent;
+
+import java.io.IOException;
+import java.security.SecureRandom;
+import java.util.Collection;
+import java.util.UUID;
+import java.util.concurrent.Executor;
+import java.util.concurrent.Semaphore;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.logging.Logger;
+
+import javax.annotation.Nullable;
+import javax.annotation.concurrent.GuardedBy;
+import javax.annotation.concurrent.ThreadSafe;
+
+import static java.util.logging.Level.INFO;
+import static java.util.logging.Level.WARNING;
+import static java.util.logging.Logger.getLogger;
+import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.TRANSPORT_ID_BLUETOOTH;
+import static org.briarproject.bramble.api.plugin.BluetoothConstants.DEFAULT_PREF_ADDRESS_IS_REFLECTED;
+import static org.briarproject.bramble.api.plugin.BluetoothConstants.DEFAULT_PREF_EVER_CONNECTED;
+import static org.briarproject.bramble.api.plugin.BluetoothConstants.DEFAULT_PREF_PLUGIN_ENABLE;
+import static org.briarproject.bramble.api.plugin.BluetoothConstants.ID;
+import static org.briarproject.bramble.api.plugin.BluetoothConstants.PREF_ADDRESS_IS_REFLECTED;
+import static org.briarproject.bramble.api.plugin.BluetoothConstants.PREF_EVER_CONNECTED;
+import static org.briarproject.bramble.api.plugin.BluetoothConstants.PROP_ADDRESS;
+import static org.briarproject.bramble.api.plugin.BluetoothConstants.PROP_UUID;
+import static org.briarproject.bramble.api.plugin.BluetoothConstants.UUID_BYTES;
+import static org.briarproject.bramble.api.plugin.Plugin.State.ACTIVE;
+import static org.briarproject.bramble.api.plugin.Plugin.State.DISABLED;
+import static org.briarproject.bramble.api.plugin.Plugin.State.INACTIVE;
+import static org.briarproject.bramble.api.plugin.Plugin.State.STARTING_STOPPING;
+import static org.briarproject.bramble.api.properties.TransportPropertyConstants.REFLECTED_PROPERTY_PREFIX;
+import static org.briarproject.bramble.util.LogUtils.logException;
+import static org.briarproject.bramble.util.PrivacyUtils.scrubMacAddress;
+import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
+import static org.briarproject.bramble.util.StringUtils.macToBytes;
+import static org.briarproject.bramble.util.StringUtils.macToString;
+
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
+abstract class AbstractBluetoothPlugin<S, SS> implements BluetoothPlugin,
+		EventListener {
+
+	private static final Logger LOG =
+			getLogger(AbstractBluetoothPlugin.class.getName());
+
+	private final BluetoothConnectionLimiter connectionLimiter;
+	final BluetoothConnectionFactory<S> connectionFactory;
+
+	private final Executor ioExecutor, wakefulIoExecutor;
+	private final SecureRandom secureRandom;
+	private final Backoff backoff;
+	private final PluginCallback callback;
+	private final int maxLatency, maxIdleTime;
+	private final AtomicBoolean used = new AtomicBoolean(false);
+	private final AtomicBoolean everConnected = new AtomicBoolean(false);
+
+	protected final PluginState state = new PluginState();
+	protected final Semaphore discoverSemaphore = new Semaphore(1);
+
+	private volatile String contactConnectionsUuid = null;
+
+	abstract void initialiseAdapter() throws IOException;
+
+	abstract boolean isAdapterEnabled();
+
+	/**
+	 * Returns the local Bluetooth address, or null if no valid address can
+	 * be found.
+	 */
+	@Nullable
+	abstract String getBluetoothAddress();
+
+	abstract SS openServerSocket(String uuid) throws IOException;
+
+	abstract void tryToClose(@Nullable SS ss);
+
+	abstract DuplexTransportConnection acceptConnection(SS ss)
+			throws IOException;
+
+	abstract boolean isValidAddress(String address);
+
+	abstract DuplexTransportConnection connectTo(String address, String uuid)
+			throws IOException;
+
+	@Nullable
+	abstract DuplexTransportConnection discoverAndConnect(String uuid);
+
+	AbstractBluetoothPlugin(BluetoothConnectionLimiter connectionLimiter,
+			BluetoothConnectionFactory<S> connectionFactory,
+			Executor ioExecutor,
+			Executor wakefulIoExecutor,
+			SecureRandom secureRandom,
+			Backoff backoff,
+			PluginCallback callback,
+			int maxLatency,
+			int maxIdleTime) {
+		this.connectionLimiter = connectionLimiter;
+		this.connectionFactory = connectionFactory;
+		this.ioExecutor = ioExecutor;
+		this.wakefulIoExecutor = wakefulIoExecutor;
+		this.secureRandom = secureRandom;
+		this.backoff = backoff;
+		this.callback = callback;
+		this.maxLatency = maxLatency;
+		this.maxIdleTime = maxIdleTime;
+	}
+
+	void onAdapterEnabled() {
+		LOG.info("Bluetooth enabled");
+		// We may not have been able to get the local address before
+		ioExecutor.execute(this::updateProperties);
+		if (getState() == INACTIVE) bind();
+	}
+
+	void onAdapterDisabled() {
+		LOG.info("Bluetooth disabled");
+		connectionLimiter.allConnectionsClosed();
+		// The server socket may not have been closed automatically
+		SS ss = state.clearServerSocket();
+		if (ss != null) {
+			LOG.info("Closing server socket");
+			tryToClose(ss);
+		}
+	}
+
+	@Override
+	public TransportId getId() {
+		return ID;
+	}
+
+	@Override
+	public int getMaxLatency() {
+		return maxLatency;
+	}
+
+	@Override
+	public int getMaxIdleTime() {
+		return maxIdleTime;
+	}
+
+	@Override
+	public void start() throws PluginException {
+		if (used.getAndSet(true)) throw new IllegalStateException();
+		Settings settings = callback.getSettings();
+		boolean enabledByUser = settings.getBoolean(PREF_PLUGIN_ENABLE,
+				DEFAULT_PREF_PLUGIN_ENABLE);
+		everConnected.set(settings.getBoolean(PREF_EVER_CONNECTED,
+				DEFAULT_PREF_EVER_CONNECTED));
+		state.setStarted(enabledByUser);
+		try {
+			initialiseAdapter();
+		} catch (IOException e) {
+			throw new PluginException(e);
+		}
+		updateProperties();
+		if (enabledByUser && isAdapterEnabled()) bind();
+	}
+
+	private void bind() {
+		ioExecutor.execute(() -> {
+			if (getState() != INACTIVE) return;
+			// Bind a server socket to accept connections from contacts
+			SS ss;
+			try {
+				ss = openServerSocket(contactConnectionsUuid);
+			} catch (IOException e) {
+				logException(LOG, WARNING, e);
+				return;
+			}
+			if (!state.setServerSocket(ss)) {
+				LOG.info("Closing redundant server socket");
+				tryToClose(ss);
+				return;
+			}
+			backoff.reset();
+			acceptContactConnections(ss);
+		});
+	}
+
+	private void updateProperties() {
+		TransportProperties p = callback.getLocalProperties();
+		String address = p.get(PROP_ADDRESS);
+		String uuid = p.get(PROP_UUID);
+		Settings s = callback.getSettings();
+		boolean isReflected = s.getBoolean(PREF_ADDRESS_IS_REFLECTED,
+				DEFAULT_PREF_ADDRESS_IS_REFLECTED);
+		boolean changed = false;
+		if (address == null || isReflected) {
+			address = getBluetoothAddress();
+			if (LOG.isLoggable(INFO)) {
+				LOG.info("Local address " + scrubMacAddress(address));
+			}
+			if (address == null) {
+				if (everConnected.get()) {
+					address = getReflectedAddress();
+					if (LOG.isLoggable(INFO)) {
+						LOG.info("Reflected address " +
+								scrubMacAddress(address));
+					}
+					if (address != null) {
+						changed = true;
+						isReflected = true;
+					}
+				}
+			} else {
+				changed = true;
+				isReflected = false;
+			}
+		}
+		if (uuid == null) {
+			byte[] random = new byte[UUID_BYTES];
+			secureRandom.nextBytes(random);
+			uuid = UUID.nameUUIDFromBytes(random).toString();
+			changed = true;
+		}
+		contactConnectionsUuid = uuid;
+		if (changed) {
+			p = new TransportProperties();
+			// If we previously used a reflected address and there's no longer
+			// a reflected address with enough votes to be used, we'll continue
+			// to use the old reflected address until there's a new winner
+			if (address != null) p.put(PROP_ADDRESS, address);
+			p.put(PROP_UUID, uuid);
+			callback.mergeLocalProperties(p);
+			s = new Settings();
+			s.putBoolean(PREF_ADDRESS_IS_REFLECTED, isReflected);
+			callback.mergeSettings(s);
+		}
+	}
+
+	@Nullable
+	private String getReflectedAddress() {
+		// Count the number of votes for each reflected address
+		String key = REFLECTED_PROPERTY_PREFIX + PROP_ADDRESS;
+		Multiset<String> votes = new Multiset<>();
+		for (TransportProperties p : callback.getRemoteProperties()) {
+			String address = p.get(key);
+			if (address != null && isValidAddress(address)) votes.add(address);
+		}
+		// If an address gets more than half of the votes, accept it
+		int total = votes.getTotal();
+		for (String address : votes.keySet()) {
+			if (votes.getCount(address) * 2 > total) return address;
+		}
+		return null;
+	}
+
+	private void acceptContactConnections(SS ss) {
+		while (true) {
+			DuplexTransportConnection conn;
+			try {
+				conn = acceptConnection(ss);
+			} catch (IOException e) {
+				// This is expected when the server socket is closed
+				LOG.info("Server socket closed");
+				state.clearServerSocket();
+				return;
+			}
+			LOG.info("Connection received");
+			connectionLimiter.connectionOpened(conn);
+			backoff.reset();
+			setEverConnected();
+			callback.handleConnection(conn);
+		}
+	}
+
+	private void setEverConnected() {
+		if (!everConnected.getAndSet(true)) {
+			ioExecutor.execute(() -> {
+				Settings s = new Settings();
+				s.putBoolean(PREF_EVER_CONNECTED, true);
+				callback.mergeSettings(s);
+				// Contacts may already have sent a reflected address
+				updateProperties();
+			});
+		}
+	}
+
+	@Override
+	public void stop() {
+		SS ss = state.setStopped();
+		tryToClose(ss);
+	}
+
+	@Override
+	public State getState() {
+		return state.getState();
+	}
+
+	@Override
+	public int getReasonsDisabled() {
+		return state.getReasonsDisabled();
+	}
+
+	@Override
+	public boolean shouldPoll() {
+		return true;
+	}
+
+	@Override
+	public int getPollingInterval() {
+		return backoff.getPollingInterval();
+	}
+
+	@Override
+	public void poll(Collection<Pair<TransportProperties, ConnectionHandler>>
+			properties) {
+		if (getState() != ACTIVE) return;
+		backoff.increment();
+		for (Pair<TransportProperties, ConnectionHandler> p : properties) {
+			connect(p.getFirst(), p.getSecond());
+		}
+	}
+
+	private void connect(TransportProperties p, ConnectionHandler h) {
+		String address = p.get(PROP_ADDRESS);
+		if (isNullOrEmpty(address)) return;
+		String uuid = p.get(PROP_UUID);
+		if (isNullOrEmpty(uuid)) return;
+		wakefulIoExecutor.execute(() -> {
+			DuplexTransportConnection d = createConnection(p);
+			if (d != null) {
+				backoff.reset();
+				setEverConnected();
+				h.handleConnection(d);
+			}
+		});
+	}
+
+	@Nullable
+	private DuplexTransportConnection connect(String address, String uuid) {
+		// Validate the address
+		if (!isValidAddress(address)) {
+			if (LOG.isLoggable(WARNING))
+				// Not scrubbing here to be able to figure out the problem
+				LOG.warning("Invalid address " + address);
+			return null;
+		}
+		// Validate the UUID
+		try {
+			//noinspection ResultOfMethodCallIgnored
+			UUID.fromString(uuid);
+		} catch (IllegalArgumentException e) {
+			if (LOG.isLoggable(WARNING)) LOG.warning("Invalid UUID " + uuid);
+			return null;
+		}
+		if (LOG.isLoggable(INFO))
+			LOG.info("Connecting to " + scrubMacAddress(address));
+		try {
+			DuplexTransportConnection conn = connectTo(address, uuid);
+			if (LOG.isLoggable(INFO))
+				LOG.info("Connected to " + scrubMacAddress(address));
+			return conn;
+		} catch (IOException e) {
+			if (LOG.isLoggable(INFO))
+				LOG.info("Could not connect to " + scrubMacAddress(address));
+			return null;
+		}
+	}
+
+	@Override
+	public DuplexTransportConnection createConnection(TransportProperties p) {
+		if (getState() != ACTIVE) return null;
+		if (!connectionLimiter.canOpenContactConnection()) return null;
+		String address = p.get(PROP_ADDRESS);
+		if (isNullOrEmpty(address)) return null;
+		String uuid = p.get(PROP_UUID);
+		if (isNullOrEmpty(uuid)) return null;
+		DuplexTransportConnection conn = connect(address, uuid);
+		if (conn != null) connectionLimiter.connectionOpened(conn);
+		return conn;
+	}
+
+	@Override
+	public boolean supportsKeyAgreement() {
+		return true;
+	}
+
+	@Override
+	public KeyAgreementListener createKeyAgreementListener(byte[] commitment) {
+		if (getState() != ACTIVE) return null;
+		// No truncation necessary because COMMIT_LENGTH = 16
+		String uuid = UUID.nameUUIDFromBytes(commitment).toString();
+		if (LOG.isLoggable(INFO)) LOG.info("Key agreement UUID " + uuid);
+		// Bind a server socket for receiving key agreement connections
+		SS ss;
+		try {
+			ss = openServerSocket(uuid);
+		} catch (IOException e) {
+			logException(LOG, WARNING, e);
+			return null;
+		}
+		if (getState() != ACTIVE) {
+			tryToClose(ss);
+			return null;
+		}
+		BdfList descriptor = new BdfList();
+		descriptor.add(TRANSPORT_ID_BLUETOOTH);
+		String address = getBluetoothAddress();
+		if (address != null) descriptor.add(macToBytes(address));
+		return new BluetoothKeyAgreementListener(descriptor, ss);
+	}
+
+	@Override
+	public DuplexTransportConnection createKeyAgreementConnection(
+			byte[] commitment, BdfList descriptor) {
+		if (getState() != ACTIVE) return null;
+		// No truncation necessary because COMMIT_LENGTH = 16
+		String uuid = UUID.nameUUIDFromBytes(commitment).toString();
+		DuplexTransportConnection conn;
+		if (descriptor.size() == 1) {
+			if (LOG.isLoggable(INFO)) {
+				LOG.info("Discovering address for key agreement UUID " +
+						uuid);
+			}
+			conn = discoverAndConnect(uuid);
+		} else {
+			String address;
+			try {
+				address = parseAddress(descriptor);
+			} catch (FormatException e) {
+				LOG.info("Invalid address in key agreement descriptor");
+				return null;
+			}
+			if (LOG.isLoggable(INFO))
+				LOG.info("Connecting to key agreement UUID " + uuid);
+			conn = connect(address, uuid);
+		}
+		if (conn != null) {
+			connectionLimiter.connectionOpened(conn);
+			setEverConnected();
+		}
+		return conn;
+	}
+
+	private String parseAddress(BdfList descriptor) throws FormatException {
+		byte[] mac = descriptor.getRaw(1);
+		if (mac.length != 6) throw new FormatException();
+		return macToString(mac);
+	}
+
+	@Override
+	public boolean isDiscovering() {
+		return discoverSemaphore.availablePermits() == 0;
+	}
+
+	@Override
+	public DuplexTransportConnection discoverAndConnectForSetup(String uuid) {
+		DuplexTransportConnection conn = discoverAndConnect(uuid);
+		if (conn != null) {
+			connectionLimiter.connectionOpened(conn);
+			setEverConnected();
+		}
+		return conn;
+	}
+
+	@Override
+	public boolean supportsRendezvous() {
+		return false;
+	}
+
+	@Override
+	public RendezvousEndpoint createRendezvousEndpoint(KeyMaterialSource k,
+			boolean alice, ConnectionHandler incoming) {
+		throw new UnsupportedOperationException();
+	}
+
+	@Override
+	public void eventOccurred(Event e) {
+		if (e instanceof SettingsUpdatedEvent) {
+			SettingsUpdatedEvent s = (SettingsUpdatedEvent) e;
+			if (s.getNamespace().equals(ID.getString()))
+				ioExecutor.execute(() -> onSettingsUpdated(s.getSettings()));
+		} else if (e instanceof KeyAgreementListeningEvent) {
+			ioExecutor.execute(connectionLimiter::keyAgreementStarted);
+		} else if (e instanceof KeyAgreementStoppedListeningEvent) {
+			ioExecutor.execute(connectionLimiter::keyAgreementEnded);
+		} else if (e instanceof RemoteTransportPropertiesUpdatedEvent) {
+			RemoteTransportPropertiesUpdatedEvent r =
+					(RemoteTransportPropertiesUpdatedEvent) e;
+			if (r.getTransportId().equals(ID)) {
+				ioExecutor.execute(this::updateProperties);
+			}
+		}
+	}
+
+	@IoExecutor
+	private void onSettingsUpdated(Settings settings) {
+		boolean enabledByUser = settings.getBoolean(PREF_PLUGIN_ENABLE,
+				DEFAULT_PREF_PLUGIN_ENABLE);
+		SS ss = state.setEnabledByUser(enabledByUser);
+		State s = getState();
+		if (ss != null) {
+			LOG.info("Disabled by user, closing server socket");
+			tryToClose(ss);
+		} else if (s == INACTIVE) {
+			if (isAdapterEnabled()) {
+				LOG.info("Enabled by user, opening server socket");
+				bind();
+			} else {
+				LOG.info("Enabled by user but adapter is disabled");
+			}
+		}
+	}
+
+	private class BluetoothKeyAgreementListener extends KeyAgreementListener {
+
+		private final SS ss;
+
+		private BluetoothKeyAgreementListener(BdfList descriptor, SS ss) {
+			super(descriptor);
+			this.ss = ss;
+		}
+
+		@Override
+		public KeyAgreementConnection accept() throws IOException {
+			DuplexTransportConnection conn = acceptConnection(ss);
+			if (LOG.isLoggable(INFO)) LOG.info(ID + ": Incoming connection");
+			connectionLimiter.connectionOpened(conn);
+			return new KeyAgreementConnection(conn, ID);
+		}
+
+		@Override
+		public void close() {
+			tryToClose(ss);
+		}
+	}
+
+	@ThreadSafe
+	@NotNullByDefault
+	private class PluginState {
+
+		@GuardedBy("this")
+		private boolean started = false,
+				stopped = false,
+				enabledByUser = false;
+
+		@GuardedBy("this")
+		@Nullable
+		private SS serverSocket = null;
+
+		private synchronized void setStarted(boolean enabledByUser) {
+			started = true;
+			this.enabledByUser = enabledByUser;
+			callback.pluginStateChanged(getState());
+		}
+
+		@Nullable
+		private synchronized SS setStopped() {
+			stopped = true;
+			SS ss = serverSocket;
+			serverSocket = null;
+			callback.pluginStateChanged(getState());
+			return ss;
+		}
+
+		@Nullable
+		private synchronized SS setEnabledByUser(boolean enabledByUser) {
+			this.enabledByUser = enabledByUser;
+			SS ss = null;
+			if (!enabledByUser) {
+				ss = serverSocket;
+				serverSocket = null;
+			}
+			callback.pluginStateChanged(getState());
+			return ss;
+		}
+
+		private synchronized boolean setServerSocket(SS ss) {
+			if (stopped || serverSocket != null) return false;
+			serverSocket = ss;
+			callback.pluginStateChanged(getState());
+			return true;
+		}
+
+		@Nullable
+		private synchronized SS clearServerSocket() {
+			SS ss = serverSocket;
+			serverSocket = null;
+			callback.pluginStateChanged(getState());
+			return ss;
+		}
+
+		private synchronized State getState() {
+			if (!started || stopped) return STARTING_STOPPING;
+			if (!enabledByUser) return DISABLED;
+			return serverSocket == null ? INACTIVE : ACTIVE;
+		}
+
+		private synchronized int getReasonsDisabled() {
+			return getState() == DISABLED ? REASON_USER : 0;
+		}
+	}
+}

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

@@ -1,606 +1,18 @@
 package org.briarproject.bramble.plugin.bluetooth;
 
-import org.briarproject.bramble.api.FormatException;
-import org.briarproject.bramble.api.Multiset;
-import org.briarproject.bramble.api.Pair;
-import org.briarproject.bramble.api.data.BdfList;
-import org.briarproject.bramble.api.event.Event;
-import org.briarproject.bramble.api.event.EventListener;
-import org.briarproject.bramble.api.keyagreement.KeyAgreementConnection;
-import org.briarproject.bramble.api.keyagreement.KeyAgreementListener;
-import org.briarproject.bramble.api.keyagreement.event.KeyAgreementListeningEvent;
-import org.briarproject.bramble.api.keyagreement.event.KeyAgreementStoppedListeningEvent;
-import org.briarproject.bramble.api.lifecycle.IoExecutor;
-import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
-import org.briarproject.bramble.api.plugin.Backoff;
-import org.briarproject.bramble.api.plugin.ConnectionHandler;
-import org.briarproject.bramble.api.plugin.PluginCallback;
-import org.briarproject.bramble.api.plugin.PluginException;
-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.properties.TransportProperties;
-import org.briarproject.bramble.api.properties.event.RemoteTransportPropertiesUpdatedEvent;
-import org.briarproject.bramble.api.rendezvous.KeyMaterialSource;
-import org.briarproject.bramble.api.rendezvous.RendezvousEndpoint;
-import org.briarproject.bramble.api.settings.Settings;
-import org.briarproject.bramble.api.settings.event.SettingsUpdatedEvent;
-
-import java.io.IOException;
-import java.security.SecureRandom;
-import java.util.Collection;
-import java.util.UUID;
-import java.util.concurrent.Executor;
-import java.util.concurrent.atomic.AtomicBoolean;
-import java.util.logging.Logger;
 
 import javax.annotation.Nullable;
-import javax.annotation.concurrent.GuardedBy;
-import javax.annotation.concurrent.ThreadSafe;
 
-import static java.util.logging.Level.INFO;
-import static java.util.logging.Level.WARNING;
-import static java.util.logging.Logger.getLogger;
-import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.TRANSPORT_ID_BLUETOOTH;
-import static org.briarproject.bramble.api.plugin.BluetoothConstants.DEFAULT_PREF_ADDRESS_IS_REFLECTED;
-import static org.briarproject.bramble.api.plugin.BluetoothConstants.DEFAULT_PREF_EVER_CONNECTED;
-import static org.briarproject.bramble.api.plugin.BluetoothConstants.DEFAULT_PREF_PLUGIN_ENABLE;
-import static org.briarproject.bramble.api.plugin.BluetoothConstants.ID;
-import static org.briarproject.bramble.api.plugin.BluetoothConstants.PREF_ADDRESS_IS_REFLECTED;
-import static org.briarproject.bramble.api.plugin.BluetoothConstants.PREF_EVER_CONNECTED;
-import static org.briarproject.bramble.api.plugin.BluetoothConstants.PROP_ADDRESS;
-import static org.briarproject.bramble.api.plugin.BluetoothConstants.PROP_UUID;
-import static org.briarproject.bramble.api.plugin.BluetoothConstants.UUID_BYTES;
-import static org.briarproject.bramble.api.plugin.Plugin.State.ACTIVE;
-import static org.briarproject.bramble.api.plugin.Plugin.State.DISABLED;
-import static org.briarproject.bramble.api.plugin.Plugin.State.INACTIVE;
-import static org.briarproject.bramble.api.plugin.Plugin.State.STARTING_STOPPING;
-import static org.briarproject.bramble.api.properties.TransportPropertyConstants.REFLECTED_PROPERTY_PREFIX;
-import static org.briarproject.bramble.util.LogUtils.logException;
-import static org.briarproject.bramble.util.PrivacyUtils.scrubMacAddress;
-import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
-import static org.briarproject.bramble.util.StringUtils.macToBytes;
-import static org.briarproject.bramble.util.StringUtils.macToString;
+@NotNullByDefault
+public interface BluetoothPlugin extends DuplexPlugin {
 
-@MethodsNotNullByDefault
-@ParametersNotNullByDefault
-abstract class BluetoothPlugin<S, SS> implements DuplexPlugin, EventListener {
-
-	private static final Logger LOG =
-			getLogger(BluetoothPlugin.class.getName());
-
-	final BluetoothConnectionLimiter connectionLimiter;
-	final BluetoothConnectionFactory<S> connectionFactory;
-
-	private final Executor ioExecutor, wakefulIoExecutor;
-	private final SecureRandom secureRandom;
-	private final Backoff backoff;
-	private final PluginCallback callback;
-	private final int maxLatency, maxIdleTime;
-	private final AtomicBoolean used = new AtomicBoolean(false);
-	private final AtomicBoolean everConnected = new AtomicBoolean(false);
-
-	protected final PluginState state = new PluginState();
-
-	private volatile String contactConnectionsUuid = null;
-
-	abstract void initialiseAdapter() throws IOException;
-
-	abstract boolean isAdapterEnabled();
-
-	/**
-	 * Returns the local Bluetooth address, or null if no valid address can
-	 * be found.
-	 */
-	@Nullable
-	abstract String getBluetoothAddress();
-
-	abstract SS openServerSocket(String uuid) throws IOException;
-
-	abstract void tryToClose(@Nullable SS ss);
-
-	abstract DuplexTransportConnection acceptConnection(SS ss)
-			throws IOException;
-
-	abstract boolean isValidAddress(String address);
-
-	abstract DuplexTransportConnection connectTo(String address, String uuid)
-			throws IOException;
+	boolean isDiscovering();
 
 	@Nullable
-	abstract DuplexTransportConnection discoverAndConnect(String uuid);
+	DuplexTransportConnection discoverAndConnectForSetup(String uuid);
 
-	BluetoothPlugin(BluetoothConnectionLimiter connectionLimiter,
-			BluetoothConnectionFactory<S> connectionFactory,
-			Executor ioExecutor,
-			Executor wakefulIoExecutor,
-			SecureRandom secureRandom,
-			Backoff backoff,
-			PluginCallback callback,
-			int maxLatency,
-			int maxIdleTime) {
-		this.connectionLimiter = connectionLimiter;
-		this.connectionFactory = connectionFactory;
-		this.ioExecutor = ioExecutor;
-		this.wakefulIoExecutor = wakefulIoExecutor;
-		this.secureRandom = secureRandom;
-		this.backoff = backoff;
-		this.callback = callback;
-		this.maxLatency = maxLatency;
-		this.maxIdleTime = maxIdleTime;
-	}
-
-	void onAdapterEnabled() {
-		LOG.info("Bluetooth enabled");
-		// We may not have been able to get the local address before
-		ioExecutor.execute(this::updateProperties);
-		if (getState() == INACTIVE) bind();
-	}
-
-	void onAdapterDisabled() {
-		LOG.info("Bluetooth disabled");
-		connectionLimiter.allConnectionsClosed();
-		// The server socket may not have been closed automatically
-		SS ss = state.clearServerSocket();
-		if (ss != null) {
-			LOG.info("Closing server socket");
-			tryToClose(ss);
-		}
-	}
-
-	@Override
-	public TransportId getId() {
-		return ID;
-	}
-
-	@Override
-	public int getMaxLatency() {
-		return maxLatency;
-	}
-
-	@Override
-	public int getMaxIdleTime() {
-		return maxIdleTime;
-	}
-
-	@Override
-	public void start() throws PluginException {
-		if (used.getAndSet(true)) throw new IllegalStateException();
-		Settings settings = callback.getSettings();
-		boolean enabledByUser = settings.getBoolean(PREF_PLUGIN_ENABLE,
-				DEFAULT_PREF_PLUGIN_ENABLE);
-		everConnected.set(settings.getBoolean(PREF_EVER_CONNECTED,
-				DEFAULT_PREF_EVER_CONNECTED));
-		state.setStarted(enabledByUser);
-		try {
-			initialiseAdapter();
-		} catch (IOException e) {
-			throw new PluginException(e);
-		}
-		updateProperties();
-		if (enabledByUser && isAdapterEnabled()) bind();
-	}
-
-	private void bind() {
-		ioExecutor.execute(() -> {
-			if (getState() != INACTIVE) return;
-			// Bind a server socket to accept connections from contacts
-			SS ss;
-			try {
-				ss = openServerSocket(contactConnectionsUuid);
-			} catch (IOException e) {
-				logException(LOG, WARNING, e);
-				return;
-			}
-			if (!state.setServerSocket(ss)) {
-				LOG.info("Closing redundant server socket");
-				tryToClose(ss);
-				return;
-			}
-			backoff.reset();
-			acceptContactConnections(ss);
-		});
-	}
-
-	private void updateProperties() {
-		TransportProperties p = callback.getLocalProperties();
-		String address = p.get(PROP_ADDRESS);
-		String uuid = p.get(PROP_UUID);
-		Settings s = callback.getSettings();
-		boolean isReflected = s.getBoolean(PREF_ADDRESS_IS_REFLECTED,
-				DEFAULT_PREF_ADDRESS_IS_REFLECTED);
-		boolean changed = false;
-		if (address == null || isReflected) {
-			address = getBluetoothAddress();
-			if (LOG.isLoggable(INFO)) {
-				LOG.info("Local address " + scrubMacAddress(address));
-			}
-			if (address == null) {
-				if (everConnected.get()) {
-					address = getReflectedAddress();
-					if (LOG.isLoggable(INFO)) {
-						LOG.info("Reflected address " +
-								scrubMacAddress(address));
-					}
-					if (address != null) {
-						changed = true;
-						isReflected = true;
-					}
-				}
-			} else {
-				changed = true;
-				isReflected = false;
-			}
-		}
-		if (uuid == null) {
-			byte[] random = new byte[UUID_BYTES];
-			secureRandom.nextBytes(random);
-			uuid = UUID.nameUUIDFromBytes(random).toString();
-			changed = true;
-		}
-		contactConnectionsUuid = uuid;
-		if (changed) {
-			p = new TransportProperties();
-			// If we previously used a reflected address and there's no longer
-			// a reflected address with enough votes to be used, we'll continue
-			// to use the old reflected address until there's a new winner
-			if (address != null) p.put(PROP_ADDRESS, address);
-			p.put(PROP_UUID, uuid);
-			callback.mergeLocalProperties(p);
-			s = new Settings();
-			s.putBoolean(PREF_ADDRESS_IS_REFLECTED, isReflected);
-			callback.mergeSettings(s);
-		}
-	}
-
-	@Nullable
-	private String getReflectedAddress() {
-		// Count the number of votes for each reflected address
-		String key = REFLECTED_PROPERTY_PREFIX + PROP_ADDRESS;
-		Multiset<String> votes = new Multiset<>();
-		for (TransportProperties p : callback.getRemoteProperties()) {
-			String address = p.get(key);
-			if (address != null && isValidAddress(address)) votes.add(address);
-		}
-		// If an address gets more than half of the votes, accept it
-		int total = votes.getTotal();
-		for (String address : votes.keySet()) {
-			if (votes.getCount(address) * 2 > total) return address;
-		}
-		return null;
-	}
-
-	private void acceptContactConnections(SS ss) {
-		while (true) {
-			DuplexTransportConnection conn;
-			try {
-				conn = acceptConnection(ss);
-			} catch (IOException e) {
-				// This is expected when the server socket is closed
-				LOG.info("Server socket closed");
-				state.clearServerSocket();
-				return;
-			}
-			LOG.info("Connection received");
-			connectionLimiter.connectionOpened(conn);
-			backoff.reset();
-			setEverConnected();
-			callback.handleConnection(conn);
-		}
-	}
-
-	private void setEverConnected() {
-		if (!everConnected.getAndSet(true)) {
-			ioExecutor.execute(() -> {
-				Settings s = new Settings();
-				s.putBoolean(PREF_EVER_CONNECTED, true);
-				callback.mergeSettings(s);
-				// Contacts may already have sent a reflected address
-				updateProperties();
-			});
-		}
-	}
-
-	@Override
-	public void stop() {
-		SS ss = state.setStopped();
-		tryToClose(ss);
-	}
-
-	@Override
-	public State getState() {
-		return state.getState();
-	}
-
-	@Override
-	public int getReasonsDisabled() {
-		return state.getReasonsDisabled();
-	}
-
-	@Override
-	public boolean shouldPoll() {
-		return true;
-	}
-
-	@Override
-	public int getPollingInterval() {
-		return backoff.getPollingInterval();
-	}
-
-	@Override
-	public void poll(Collection<Pair<TransportProperties, ConnectionHandler>>
-			properties) {
-		if (getState() != ACTIVE) return;
-		backoff.increment();
-		for (Pair<TransportProperties, ConnectionHandler> p : properties) {
-			connect(p.getFirst(), p.getSecond());
-		}
-	}
-
-	private void connect(TransportProperties p, ConnectionHandler h) {
-		String address = p.get(PROP_ADDRESS);
-		if (isNullOrEmpty(address)) return;
-		String uuid = p.get(PROP_UUID);
-		if (isNullOrEmpty(uuid)) return;
-		wakefulIoExecutor.execute(() -> {
-			DuplexTransportConnection d = createConnection(p);
-			if (d != null) {
-				backoff.reset();
-				setEverConnected();
-				h.handleConnection(d);
-			}
-		});
-	}
-
-	@Nullable
-	private DuplexTransportConnection connect(String address, String uuid) {
-		// Validate the address
-		if (!isValidAddress(address)) {
-			if (LOG.isLoggable(WARNING))
-				// Not scrubbing here to be able to figure out the problem
-				LOG.warning("Invalid address " + address);
-			return null;
-		}
-		// Validate the UUID
-		try {
-			//noinspection ResultOfMethodCallIgnored
-			UUID.fromString(uuid);
-		} catch (IllegalArgumentException e) {
-			if (LOG.isLoggable(WARNING)) LOG.warning("Invalid UUID " + uuid);
-			return null;
-		}
-		if (LOG.isLoggable(INFO))
-			LOG.info("Connecting to " + scrubMacAddress(address));
-		try {
-			DuplexTransportConnection conn = connectTo(address, uuid);
-			if (LOG.isLoggable(INFO))
-				LOG.info("Connected to " + scrubMacAddress(address));
-			return conn;
-		} catch (IOException e) {
-			if (LOG.isLoggable(INFO))
-				LOG.info("Could not connect to " + scrubMacAddress(address));
-			return null;
-		}
-	}
-
-	@Override
-	public DuplexTransportConnection createConnection(TransportProperties p) {
-		if (getState() != ACTIVE) return null;
-		if (!connectionLimiter.canOpenContactConnection()) return null;
-		String address = p.get(PROP_ADDRESS);
-		if (isNullOrEmpty(address)) return null;
-		String uuid = p.get(PROP_UUID);
-		if (isNullOrEmpty(uuid)) return null;
-		DuplexTransportConnection conn = connect(address, uuid);
-		if (conn != null) connectionLimiter.connectionOpened(conn);
-		return conn;
-	}
-
-	@Override
-	public boolean supportsKeyAgreement() {
-		return true;
-	}
-
-	@Override
-	public KeyAgreementListener createKeyAgreementListener(byte[] commitment) {
-		if (getState() != ACTIVE) return null;
-		// No truncation necessary because COMMIT_LENGTH = 16
-		String uuid = UUID.nameUUIDFromBytes(commitment).toString();
-		if (LOG.isLoggable(INFO)) LOG.info("Key agreement UUID " + uuid);
-		// Bind a server socket for receiving key agreement connections
-		SS ss;
-		try {
-			ss = openServerSocket(uuid);
-		} catch (IOException e) {
-			logException(LOG, WARNING, e);
-			return null;
-		}
-		if (getState() != ACTIVE) {
-			tryToClose(ss);
-			return null;
-		}
-		BdfList descriptor = new BdfList();
-		descriptor.add(TRANSPORT_ID_BLUETOOTH);
-		String address = getBluetoothAddress();
-		if (address != null) descriptor.add(macToBytes(address));
-		return new BluetoothKeyAgreementListener(descriptor, ss);
-	}
-
-	@Override
-	public DuplexTransportConnection createKeyAgreementConnection(
-			byte[] commitment, BdfList descriptor) {
-		if (getState() != ACTIVE) return null;
-		// No truncation necessary because COMMIT_LENGTH = 16
-		String uuid = UUID.nameUUIDFromBytes(commitment).toString();
-		DuplexTransportConnection conn;
-		if (descriptor.size() == 1) {
-			if (LOG.isLoggable(INFO)) {
-				LOG.info("Discovering address for key agreement UUID " +
-						uuid);
-			}
-			conn = discoverAndConnect(uuid);
-		} else {
-			String address;
-			try {
-				address = parseAddress(descriptor);
-			} catch (FormatException e) {
-				LOG.info("Invalid address in key agreement descriptor");
-				return null;
-			}
-			if (LOG.isLoggable(INFO))
-				LOG.info("Connecting to key agreement UUID " + uuid);
-			conn = connect(address, uuid);
-		}
-		if (conn != null) {
-			connectionLimiter.connectionOpened(conn);
-			setEverConnected();
-		}
-		return conn;
-	}
-
-	private String parseAddress(BdfList descriptor) throws FormatException {
-		byte[] mac = descriptor.getRaw(1);
-		if (mac.length != 6) throw new FormatException();
-		return macToString(mac);
-	}
-
-	@Override
-	public boolean supportsRendezvous() {
-		return false;
-	}
-
-	@Override
-	public RendezvousEndpoint createRendezvousEndpoint(KeyMaterialSource k,
-			boolean alice, ConnectionHandler incoming) {
-		throw new UnsupportedOperationException();
-	}
-
-	@Override
-	public void eventOccurred(Event e) {
-		if (e instanceof SettingsUpdatedEvent) {
-			SettingsUpdatedEvent s = (SettingsUpdatedEvent) e;
-			if (s.getNamespace().equals(ID.getString()))
-				ioExecutor.execute(() -> onSettingsUpdated(s.getSettings()));
-		} else if (e instanceof KeyAgreementListeningEvent) {
-			ioExecutor.execute(connectionLimiter::keyAgreementStarted);
-		} else if (e instanceof KeyAgreementStoppedListeningEvent) {
-			ioExecutor.execute(connectionLimiter::keyAgreementEnded);
-		} else if (e instanceof RemoteTransportPropertiesUpdatedEvent) {
-			RemoteTransportPropertiesUpdatedEvent r =
-					(RemoteTransportPropertiesUpdatedEvent) e;
-			if (r.getTransportId().equals(ID)) {
-				ioExecutor.execute(this::updateProperties);
-			}
-		}
-	}
-
-	@IoExecutor
-	private void onSettingsUpdated(Settings settings) {
-		boolean enabledByUser = settings.getBoolean(PREF_PLUGIN_ENABLE,
-				DEFAULT_PREF_PLUGIN_ENABLE);
-		SS ss = state.setEnabledByUser(enabledByUser);
-		State s = getState();
-		if (ss != null) {
-			LOG.info("Disabled by user, closing server socket");
-			tryToClose(ss);
-		} else if (s == INACTIVE) {
-			if (isAdapterEnabled()) {
-				LOG.info("Enabled by user, opening server socket");
-				bind();
-			} else {
-				LOG.info("Enabled by user but adapter is disabled");
-			}
-		}
-	}
-
-	private class BluetoothKeyAgreementListener extends KeyAgreementListener {
-
-		private final SS ss;
-
-		private BluetoothKeyAgreementListener(BdfList descriptor, SS ss) {
-			super(descriptor);
-			this.ss = ss;
-		}
-
-		@Override
-		public KeyAgreementConnection accept() throws IOException {
-			DuplexTransportConnection conn = acceptConnection(ss);
-			if (LOG.isLoggable(INFO)) LOG.info(ID + ": Incoming connection");
-			connectionLimiter.connectionOpened(conn);
-			return new KeyAgreementConnection(conn, ID);
-		}
-
-		@Override
-		public void close() {
-			tryToClose(ss);
-		}
-	}
-
-	@ThreadSafe
-	@NotNullByDefault
-	protected class PluginState {
-
-		@GuardedBy("this")
-		private boolean started = false,
-				stopped = false,
-				enabledByUser = false;
-
-		@GuardedBy("this")
-		@Nullable
-		private SS serverSocket = null;
-
-		synchronized void setStarted(boolean enabledByUser) {
-			started = true;
-			this.enabledByUser = enabledByUser;
-			callback.pluginStateChanged(getState());
-		}
-
-		@Nullable
-		synchronized SS setStopped() {
-			stopped = true;
-			SS ss = serverSocket;
-			serverSocket = null;
-			callback.pluginStateChanged(getState());
-			return ss;
-		}
-
-		@Nullable
-		synchronized SS setEnabledByUser(boolean enabledByUser) {
-			this.enabledByUser = enabledByUser;
-			SS ss = null;
-			if (!enabledByUser) {
-				ss = serverSocket;
-				serverSocket = null;
-			}
-			callback.pluginStateChanged(getState());
-			return ss;
-		}
-
-		synchronized boolean setServerSocket(SS ss) {
-			if (stopped || serverSocket != null) return false;
-			serverSocket = ss;
-			callback.pluginStateChanged(getState());
-			return true;
-		}
-
-		@Nullable
-		synchronized SS clearServerSocket() {
-			SS ss = serverSocket;
-			serverSocket = null;
-			callback.pluginStateChanged(getState());
-			return ss;
-		}
-
-		synchronized State getState() {
-			if (!started || stopped) return STARTING_STOPPING;
-			if (!enabledByUser) return DISABLED;
-			return serverSocket == null ? INACTIVE : ACTIVE;
-		}
-
-		synchronized int getReasonsDisabled() {
-			return getState() == DISABLED ? REASON_USER : 0;
-		}
-	}
+	void stopDiscoverAndConnect();
 }

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

@@ -25,8 +25,8 @@ import static org.briarproject.bramble.util.StringUtils.isValidMac;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
-class JavaBluetoothPlugin
-		extends BluetoothPlugin<StreamConnection, StreamConnectionNotifier> {
+class JavaBluetoothPlugin extends
+		AbstractBluetoothPlugin<StreamConnection, StreamConnectionNotifier> {
 
 	private static final Logger LOG =
 			getLogger(JavaBluetoothPlugin.class.getName());
@@ -108,6 +108,11 @@ class JavaBluetoothPlugin
 		return null; // TODO
 	}
 
+	@Override
+	public void stopDiscoverAndConnect() {
+		// TODO
+	}
+
 	private String makeUrl(String address, String uuid) {
 		return "btspp://" + address + ":" + uuid + ";name=RFCOMM";
 	}

briar-android/src/main/java/org/briarproject/briar/android/contact/add/nearby/AddNearbyContactIntroFragment.java

@@ -73,6 +73,7 @@ public class AddNearbyContactIntroFragment extends BaseFragment {
 		scrollView = v.findViewById(R.id.scrollView);
 		View button = v.findViewById(R.id.continueButton);
 		button.setOnClickListener(view -> {
+			viewModel.stopDiscovery();
 			viewModel.onContinueClicked();
 			if (permissionManager.checkPermissions()) {
 				viewModel.showQrCodeFragmentIfAllowed();

briar-android/src/main/java/org/briarproject/briar/android/contact/add/nearby/AddNearbyContactViewModel.java

@@ -44,6 +44,7 @@ import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
 import org.briarproject.bramble.api.plugin.event.TransportStateEvent;
 import org.briarproject.bramble.api.system.AndroidExecutor;
+import org.briarproject.bramble.plugin.bluetooth.BluetoothPlugin;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.contact.add.nearby.AddContactState.ContactExchangeFinished;
 import org.briarproject.briar.android.contact.add.nearby.AddContactState.ContactExchangeResult.Error;
@@ -149,7 +150,9 @@ class AddNearbyContactViewModel extends AndroidViewModel
 	@Nullable
 	private final BluetoothAdapter bt;
 	@Nullable // UiThread
-	private Plugin wifiPlugin, bluetoothPlugin;
+	private Plugin wifiPlugin;
+	@Nullable // UiThread
+	private BluetoothPlugin bluetoothPlugin;
 
 	// UiThread
 	private BluetoothDecision bluetoothDecision = BluetoothDecision.UNKNOWN;
@@ -195,7 +198,8 @@ class AddNearbyContactViewModel extends AndroidViewModel
 		this.connectionManager = connectionManager;
 		bt = BluetoothAdapter.getDefaultAdapter();
 		wifiPlugin = pluginManager.getPlugin(LanTcpConstants.ID);
-		bluetoothPlugin = pluginManager.getPlugin(BluetoothConstants.ID);
+		bluetoothPlugin = (BluetoothPlugin) pluginManager
+				.getPlugin(BluetoothConstants.ID);
 		qrCodeDecoder = new QrCodeDecoder(androidExecutor, ioExecutor, this);
 		eventBus.addListener(this);
 		IntentFilter filter = new IntentFilter(ACTION_SCAN_MODE_CHANGED);
@@ -218,7 +222,8 @@ class AddNearbyContactViewModel extends AndroidViewModel
 	@UiThread
 	void resetPlugins() {
 		wifiPlugin = pluginManager.getPlugin(LanTcpConstants.ID);
-		bluetoothPlugin = pluginManager.getPlugin(BluetoothConstants.ID);
+		bluetoothPlugin = (BluetoothPlugin) pluginManager
+				.getPlugin(BluetoothConstants.ID);
 	}
 
 	@UiThread
@@ -375,6 +380,13 @@ class AddNearbyContactViewModel extends AndroidViewModel
 		}
 	}
 
+	void stopDiscovery() {
+		if (!isBluetoothSupported() || !bluetoothPlugin.isDiscovering()) {
+			return;
+		}
+		bluetoothPlugin.stopDiscoverAndConnect();
+	}
+
 	@SuppressWarnings("StatementWithEmptyBody")
 	@UiThread
 	void showQrCodeFragmentIfAllowed() {

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

@@ -6,23 +6,30 @@ import android.bluetooth.BluetoothAdapter;
 import android.content.Context;
 import android.widget.Toast;
 
+import org.briarproject.bramble.api.connection.ConnectionManager;
 import org.briarproject.bramble.api.connection.ConnectionRegistry;
 import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.bramble.api.event.Event;
+import org.briarproject.bramble.api.event.EventBus;
+import org.briarproject.bramble.api.event.EventListener;
 import org.briarproject.bramble.api.lifecycle.IoExecutor;
-import org.briarproject.bramble.api.plugin.BluetoothConstants;
-import org.briarproject.bramble.api.plugin.Plugin;
 import org.briarproject.bramble.api.plugin.PluginManager;
+import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
+import org.briarproject.bramble.api.plugin.event.ConnectionOpenedEvent;
+import org.briarproject.bramble.api.properties.TransportPropertyManager;
 import org.briarproject.bramble.api.system.AndroidExecutor;
+import org.briarproject.bramble.plugin.bluetooth.BluetoothPlugin;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.contact.ContactItem;
 
-import java.util.Random;
 import java.util.concurrent.Executor;
 import java.util.logging.Logger;
 
 import javax.inject.Inject;
 
 import androidx.activity.result.ActivityResultLauncher;
+import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.annotation.StringRes;
 import androidx.annotation.UiThread;
@@ -31,17 +38,24 @@ import androidx.appcompat.app.AlertDialog;
 import static android.Manifest.permission.ACCESS_FINE_LOCATION;
 import static android.os.Build.VERSION.SDK_INT;
 import static androidx.core.app.ActivityCompat.shouldShowRequestPermissionRationale;
+import static java.util.concurrent.TimeUnit.SECONDS;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
+import static org.briarproject.bramble.api.plugin.BluetoothConstants.ID;
+import static org.briarproject.bramble.api.plugin.BluetoothConstants.PROP_UUID;
+import static org.briarproject.bramble.api.plugin.Plugin.State.ACTIVE;
 import static org.briarproject.bramble.util.LogUtils.logException;
+import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
 import static org.briarproject.briar.android.util.UiUtils.getGoToSettingsListener;
 import static org.briarproject.briar.android.util.UiUtils.isLocationEnabled;
 import static org.briarproject.briar.android.util.UiUtils.showLocationDialog;
 
-class BluetoothConnecter {
+class BluetoothConnecter implements EventListener {
 
 	private final Logger LOG = getLogger(BluetoothConnecter.class.getName());
 
+	private final long BT_ACTIVE_TIMEOUT = SECONDS.toMillis(5);
+
 	private enum Permission {
 		UNKNOWN, GRANTED, SHOW_RATIONALE, PERMANENTLY_DENIED
 	}
@@ -52,32 +66,41 @@ class BluetoothConnecter {
 	private final AndroidExecutor androidExecutor;
 	private final ConnectionRegistry connectionRegistry;
 	private final BluetoothAdapter bt = BluetoothAdapter.getDefaultAdapter();
+	private final EventBus eventBus;
+	private final TransportPropertyManager transportPropertyManager;
+	private final ConnectionManager connectionManager;
 
-	private volatile Plugin bluetoothPlugin;
+	private volatile BluetoothPlugin bluetoothPlugin;
 
 	private Permission locationPermission = Permission.UNKNOWN;
+	private ContactId contactId = null;
 
 	@Inject
 	BluetoothConnecter(Application app,
 			PluginManager pluginManager,
 			@IoExecutor Executor ioExecutor,
 			AndroidExecutor androidExecutor,
-			ConnectionRegistry connectionRegistry) {
+			ConnectionRegistry connectionRegistry,
+			EventBus eventBus,
+			TransportPropertyManager transportPropertyManager,
+			ConnectionManager connectionManager) {
 		this.app = app;
 		this.pluginManager = pluginManager;
 		this.ioExecutor = ioExecutor;
 		this.androidExecutor = androidExecutor;
-		this.bluetoothPlugin = pluginManager.getPlugin(BluetoothConstants.ID);
+		this.bluetoothPlugin = (BluetoothPlugin) pluginManager.getPlugin(ID);
 		this.connectionRegistry = connectionRegistry;
+		this.eventBus = eventBus;
+		this.transportPropertyManager = transportPropertyManager;
+		this.connectionManager = connectionManager;
 	}
 
 	boolean isConnectedViaBluetooth(ContactId contactId) {
-		return connectionRegistry.isConnected(contactId, BluetoothConstants.ID);
+		return connectionRegistry.isConnected(contactId, ID);
 	}
 
 	boolean isDiscovering() {
-		// TODO bluetoothPlugin.isDiscovering()
-		return false;
+		return bluetoothPlugin.isDiscovering();
 	}
 
 	/**
@@ -89,7 +112,7 @@ class BluetoothConnecter {
 		// When this class is instantiated before we are logged in
 		// (like when returning to a killed activity), bluetoothPlugin would be
 		// null and we consider bluetooth not supported. So reset here.
-		bluetoothPlugin = pluginManager.getPlugin(BluetoothConstants.ID);
+		bluetoothPlugin = (BluetoothPlugin) pluginManager.getPlugin(ID);
 	}
 
 	@UiThread
@@ -149,30 +172,84 @@ class BluetoothConnecter {
 
 	@UiThread
 	void onBluetoothDiscoverable(ContactItem contact) {
-		connect(contact.getContact().getId());
+		contactId = contact.getContact().getId();
+		connect();
 	}
 
-	private void connect(ContactId contactId) {
-		// TODO
-		//  * enable bluetooth connections setting, if not enabled
-		//  * wait for plugin to become active
-		ioExecutor.execute(() -> {
-			Random r = new Random();
-			try {
-				showToast(R.string.toast_connect_via_bluetooth_start);
-				// TODO do real work here
-				Thread.sleep(r.nextInt(3000) + 3000);
-				if (r.nextBoolean()) {
-					showToast(R.string.toast_connect_via_bluetooth_success);
-				} else {
-					showToast(R.string.toast_connect_via_bluetooth_error);
+	@Override
+	public void eventOccurred(@NonNull Event e) {
+		if (e instanceof ConnectionOpenedEvent) {
+			ConnectionOpenedEvent c = (ConnectionOpenedEvent) e;
+			if (c.getContactId().equals(contactId) && c.isIncoming() &&
+					c.getTransportId() == ID) {
+				if (bluetoothPlugin != null) {
+					bluetoothPlugin.stopDiscoverAndConnect();
 				}
-			} catch (InterruptedException e) {
-				logException(LOG, WARNING, e);
+				LOG.info("Contact connected to us");
+				showToast(R.string.toast_connect_via_bluetooth_success);
+			}
+		}
+	}
+
+	private void connect() {
+		pluginManager.setPluginEnabled(ID, true);
+
+		ioExecutor.execute(() -> {
+			if (!waitForBluetoothActive()) {
+				showToast(R.string.bt_plugin_status_inactive);
+				LOG.warning("Bluetooth plugin didn't become active");
+				return;
+			}
+			showToast(R.string.toast_connect_via_bluetooth_start);
+			eventBus.addListener(this);
+			try {
+				String uuid = null;
+				try {
+					uuid = transportPropertyManager
+							.getRemoteProperties(contactId, ID).get(PROP_UUID);
+				} catch (DbException e) {
+					logException(LOG, WARNING, e);
+				}
+				if (isNullOrEmpty(uuid)) {
+					LOG.warning("PROP_UUID missing for contact");
+					return;
+				}
+				DuplexTransportConnection conn = bluetoothPlugin
+						.discoverAndConnectForSetup(uuid);
+				if (conn == null) {
+					if (!isConnectedViaBluetooth(contactId)) {
+						LOG.warning("Failed to connect");
+						showToast(R.string.toast_connect_via_bluetooth_error);
+					} else {
+						LOG.info("Failed to connect, but contact connected");
+					}
+					return;
+				}
+				connectionManager.manageOutgoingConnection(contactId, ID, conn);
+				showToast(R.string.toast_connect_via_bluetooth_success);
+			} finally {
+				eventBus.removeListener(this);
 			}
 		});
 	}
 
+	private boolean waitForBluetoothActive() {
+		long left = BT_ACTIVE_TIMEOUT;
+		final long sleep = 250;
+		try {
+			while (left > 0) {
+				if (bluetoothPlugin.getState() == ACTIVE) {
+					return true;
+				}
+				Thread.sleep(sleep);
+				left -= sleep;
+			}
+		} catch (InterruptedException e) {
+			Thread.currentThread().interrupt();
+		}
+		return (bluetoothPlugin.getState() == ACTIVE);
+	}
+
 	private void showToast(@StringRes int res) {
 		androidExecutor.runOnUiThread(() ->
 				Toast.makeText(app, res, Toast.LENGTH_LONG).show()

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

@@ -91,7 +91,7 @@ public class BluetoothConnecterDialogFragment extends DialogFragment {
 			return;
 		}
 		if (bluetoothConnecter.isDiscovering()) {
-			// TODO showToast(R.string.toast_connect_via_bluetooth_discovering);
+			showToast(R.string.toast_connect_via_bluetooth_already_discovering);
 			dismiss();
 		}
 	}

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

@@ -34,6 +34,7 @@ import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.event.EventListener;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
+import org.briarproject.bramble.api.plugin.BluetoothConstants;
 import org.briarproject.bramble.api.plugin.event.ContactConnectedEvent;
 import org.briarproject.bramble.api.plugin.event.ContactDisconnectedEvent;
 import org.briarproject.bramble.api.sync.ClientId;

briar-android/src/main/res/values/strings.xml

@@ -175,6 +175,7 @@
 	<string name="menu_item_connect_via_bluetooth">Connect via Bluetooth</string>
 	<string name="dialog_title_connect_via_bluetooth">Connect via Bluetooth</string>
 	<string name="dialog_message_connect_via_bluetooth">Your contact needs to be nearby for this to work.\n\nYou and your contact should both press \"Start\" at the same time.</string>
+	<string name="toast_connect_via_bluetooth_already_discovering">Already trying to connect via Bluetooth</string>
 	<string name="toast_connect_via_bluetooth_not_discoverable">Cannot continue without Bluetooth</string>
 	<string name="toast_connect_via_bluetooth_no_location_permission">Cannot continue without location permission</string>
 	<string name="toast_connect_via_bluetooth_start">Connecting via Bluetooth…</string>