Limit the number of open Bluetooth connections.

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

@@ -55,10 +55,12 @@ class AndroidBluetoothPlugin extends BluetoothPlugin<BluetoothServerSocket> {
 	// Non-null if the plugin started successfully
 	private volatile BluetoothAdapter adapter = null;
 
-	AndroidBluetoothPlugin(Executor ioExecutor, AndroidExecutor androidExecutor,
+	AndroidBluetoothPlugin(BluetoothConnectionManager connectionManager,
+			Executor ioExecutor, AndroidExecutor androidExecutor,
 			Context appContext, SecureRandom secureRandom, Backoff backoff,
 			DuplexPluginCallback callback, int maxLatency) {
-		super(ioExecutor, secureRandom, backoff, callback, maxLatency);
+		super(connectionManager, ioExecutor, secureRandom, backoff, callback,
+				maxLatency);
 		this.androidExecutor = androidExecutor;
 		this.appContext = appContext;
 	}
@@ -154,7 +156,8 @@ class AndroidBluetoothPlugin extends BluetoothPlugin<BluetoothServerSocket> {
 	}
 
 	private DuplexTransportConnection wrapSocket(BluetoothSocket s) {
-		return new AndroidBluetoothTransportConnection(this, s);
+		return new AndroidBluetoothTransportConnection(this,
+				connectionManager, s);
 	}
 
 	@Override

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

@@ -59,11 +59,13 @@ public class AndroidBluetoothPluginFactory implements DuplexPluginFactory {
 
 	@Override
 	public DuplexPlugin createPlugin(DuplexPluginCallback callback) {
+		BluetoothConnectionManager connectionManager =
+				new BluetoothConnectionManagerImpl();
 		Backoff backoff = backoffFactory.createBackoff(MIN_POLLING_INTERVAL,
 				MAX_POLLING_INTERVAL, BACKOFF_BASE);
-		AndroidBluetoothPlugin plugin = new AndroidBluetoothPlugin(ioExecutor,
+		AndroidBluetoothPlugin plugin = new AndroidBluetoothPlugin(
-				androidExecutor, appContext, secureRandom, backoff, callback,
+				connectionManager, ioExecutor, androidExecutor, appContext,
-				MAX_LATENCY);
+				secureRandom, backoff, callback, MAX_LATENCY);
 		eventBus.addListener(plugin);
 		return plugin;
 	}

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

@@ -14,10 +14,14 @@ import java.io.OutputStream;
 class AndroidBluetoothTransportConnection
 		extends AbstractDuplexTransportConnection {
 
+	private final BluetoothConnectionManager connectionManager;
 	private final BluetoothSocket socket;
 
-	AndroidBluetoothTransportConnection(Plugin plugin, BluetoothSocket socket) {
+	AndroidBluetoothTransportConnection(Plugin plugin,
+			BluetoothConnectionManager connectionManager,
+			BluetoothSocket socket) {
 		super(plugin);
+		this.connectionManager = connectionManager;
 		this.socket = socket;
 	}
 
@@ -33,6 +37,10 @@ class AndroidBluetoothTransportConnection
 
 	@Override
 	protected void closeConnection(boolean exception) throws IOException {
-		socket.close();
+		try {
+			socket.close();
+		} finally {
+			connectionManager.connectionClosed();
+		}
 	}
 }

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

@@ -0,0 +1,26 @@
+package org.briarproject.bramble.plugin.bluetooth;
+
+interface BluetoothConnectionManager {
+
+	/**
+	 * Returns true if a contact connection can be opened without exceeding
+	 * the connection limit.
+	 */
+	boolean canOpenConnection();
+
+	/**
+	 * Increments the number of open connections and returns true if the new
+	 * connection can be kept open without exceeding the connection limit.
+	 */
+	boolean connectionOpened();
+
+	/**
+	 * Decrements the number of open connections.
+	 */
+	void connectionClosed();
+
+	/**
+	 * Resets the number of open connections.
+	 */
+	void allConnectionsClosed();
+}

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

@@ -0,0 +1,45 @@
+package org.briarproject.bramble.plugin.bluetooth;
+
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.logging.Logger;
+
+import static java.util.logging.Level.INFO;
+
+class BluetoothConnectionManagerImpl implements BluetoothConnectionManager {
+
+	private static final int MAX_OPEN_CONNECTIONS = 5;
+
+	private static final Logger LOG =
+			Logger.getLogger(BluetoothConnectionManagerImpl.class.getName());
+
+	private final AtomicInteger openConnections = new AtomicInteger(0);
+
+	@Override
+	public boolean canOpenConnection() {
+		int open = openConnections.get();
+		if (LOG.isLoggable(INFO))
+			LOG.info(open + " open connections");
+		return open < MAX_OPEN_CONNECTIONS;
+	}
+
+	@Override
+	public boolean connectionOpened() {
+		int open = openConnections.incrementAndGet();
+		if (LOG.isLoggable(INFO))
+			LOG.info("Connection opened, " + open + " open");
+		return open <= MAX_OPEN_CONNECTIONS;
+	}
+
+	@Override
+	public void connectionClosed() {
+		int open = openConnections.decrementAndGet();
+		if (LOG.isLoggable(INFO))
+			LOG.info("Connection closed, " + open + " open");
+	}
+
+	@Override
+	public void allConnectionsClosed() {
+		LOG.info("All connections closed");
+		openConnections.set(0);
+	}
+}

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

@@ -52,6 +52,8 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 	private static final Logger LOG =
 			Logger.getLogger(BluetoothPlugin.class.getName());
 
+	protected final BluetoothConnectionManager connectionManager;
+
 	private final Executor ioExecutor;
 	private final SecureRandom secureRandom;
 	private final Backoff backoff;
@@ -92,8 +94,10 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 	abstract DuplexTransportConnection connectTo(String address, String uuid)
 			throws IOException;
 
-	BluetoothPlugin(Executor ioExecutor, SecureRandom secureRandom,
+	BluetoothPlugin(BluetoothConnectionManager connectionManager,
+			Executor ioExecutor, SecureRandom secureRandom,
 			Backoff backoff, DuplexPluginCallback callback, int maxLatency) {
+		this.connectionManager = connectionManager;
 		this.ioExecutor = ioExecutor;
 		this.secureRandom = secureRandom;
 		this.backoff = backoff;
@@ -111,6 +115,7 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 	void onAdapterDisabled() {
 		LOG.info("Bluetooth disabled");
 		tryToClose(socket);
+		connectionManager.allConnectionsClosed();
 		callback.transportDisabled();
 	}
 
@@ -214,11 +219,25 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 				return;
 			}
 			backoff.reset();
-			callback.incomingConnectionCreated(conn);
+			if (connectionManager.connectionOpened()) {
+				callback.incomingConnectionCreated(conn);
+			} else {
+				LOG.info("Closing incoming connection");
+				tryToCloseUnusedConnection(conn);
+			}
 			if (!running) return;
 		}
 	}
 
+	private void tryToCloseUnusedConnection(DuplexTransportConnection conn) {
+		try {
+			conn.getWriter().dispose(false);
+			conn.getReader().dispose(false, false);
+		} catch (IOException e) {
+			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
+		}
+	}
+
 	@Override
 	public void stop() {
 		running = false;
@@ -258,10 +277,19 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 			if (StringUtils.isNullOrEmpty(uuid)) continue;
 			ioExecutor.execute(() -> {
 				if (!isRunning() || !shouldAllowContactConnections()) return;
+				if (!connectionManager.canOpenConnection()) {
+					LOG.info("Not connecting, too many open connections");
+					return;
+				}
 				DuplexTransportConnection conn = connect(address, uuid);
 				if (conn != null) {
 					backoff.reset();
-					callback.outgoingConnectionCreated(c, conn);
+					if (connectionManager.connectionOpened()) {
+						callback.outgoingConnectionCreated(c, conn);
+					} else {
+						LOG.info("Closing outgoing connection");
+						tryToCloseUnusedConnection(conn);
+					}
 				}
 			});
 		}
@@ -301,12 +329,25 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 	@Override
 	public DuplexTransportConnection createConnection(ContactId c) {
 		if (!isRunning() || !shouldAllowContactConnections()) return null;
+		if (!connectionManager.canOpenConnection()) {
+			LOG.info("Not connecting, too many open connections");
+			return null;
+		}
 		TransportProperties p = callback.getRemoteProperties(c);
 		String address = p.get(PROP_ADDRESS);
 		if (StringUtils.isNullOrEmpty(address)) return null;
 		String uuid = p.get(PROP_UUID);
 		if (StringUtils.isNullOrEmpty(uuid)) return null;
-		return connect(address, uuid);
+		DuplexTransportConnection conn = connect(address, uuid);
+		if (conn == null) return null;
+		// TODO: Why don't we reset the backoff here?
+		if (connectionManager.connectionOpened()) {
+			return conn;
+		} else {
+			LOG.info("Closing outgoing connection");
+			tryToCloseUnusedConnection(conn);
+			return null;
+		}
 	}
 
 	@Override
@@ -356,7 +397,10 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 		String uuid = UUID.nameUUIDFromBytes(commitment).toString();
 		if (LOG.isLoggable(INFO))
 			LOG.info("Connecting to key agreement UUID " + uuid);
-		return connect(address, uuid);
+		DuplexTransportConnection conn = connect(address, uuid);
+		// The connection limit doesn't apply to key agreement
+		if (conn != null) connectionManager.connectionOpened();
+		return conn;
 	}
 
 	private String parseAddress(BdfList descriptor) throws FormatException {
@@ -411,6 +455,8 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 				DuplexTransportConnection conn = acceptConnection(ss);
 				if (LOG.isLoggable(INFO))
 					LOG.info(ID.getString() + ": Incoming connection");
+				// The connection limit doesn't apply to key agreement
+				connectionManager.connectionOpened();
 				return new KeyAgreementConnection(conn, ID);
 			};
 		}

bramble-j2se/src/main/java/org/briarproject/bramble/plugin/bluetooth/JavaBluetoothPlugin.java

@@ -31,9 +31,11 @@ class JavaBluetoothPlugin extends BluetoothPlugin<StreamConnectionNotifier> {
 	// Non-null if the plugin started successfully
 	private volatile LocalDevice localDevice = null;
 
-	JavaBluetoothPlugin(Executor ioExecutor, SecureRandom secureRandom,
+	JavaBluetoothPlugin(BluetoothConnectionManager connectionManager,
+			Executor ioExecutor, SecureRandom secureRandom,
 			Backoff backoff, DuplexPluginCallback callback, int maxLatency) {
-		super(ioExecutor, secureRandom, backoff, callback, maxLatency);
+		super(connectionManager, ioExecutor, secureRandom, backoff, callback,
+				maxLatency);
 	}
 
 	@Override
@@ -110,6 +112,6 @@ class JavaBluetoothPlugin extends BluetoothPlugin<StreamConnectionNotifier> {
 	}
 
 	private DuplexTransportConnection wrapSocket(StreamConnection s) {
-		return new JavaBluetoothTransportConnection(this, s);
+		return new JavaBluetoothTransportConnection(this, connectionManager, s);
 	}
 }

bramble-j2se/src/main/java/org/briarproject/bramble/plugin/bluetooth/JavaBluetoothPluginFactory.java

@@ -51,10 +51,12 @@ public class JavaBluetoothPluginFactory implements DuplexPluginFactory {
 
 	@Override
 	public DuplexPlugin createPlugin(DuplexPluginCallback callback) {
+		BluetoothConnectionManager connectionManager =
+				new BluetoothConnectionManagerImpl();
 		Backoff backoff = backoffFactory.createBackoff(MIN_POLLING_INTERVAL,
 				MAX_POLLING_INTERVAL, BACKOFF_BASE);
-		JavaBluetoothPlugin plugin = new JavaBluetoothPlugin(ioExecutor,
+		JavaBluetoothPlugin plugin = new JavaBluetoothPlugin(connectionManager,
-				secureRandom, backoff, callback, MAX_LATENCY);
+				ioExecutor, secureRandom, backoff, callback, MAX_LATENCY);
 		eventBus.addListener(plugin);
 		return plugin;
 	}

bramble-j2se/src/main/java/org/briarproject/bramble/plugin/bluetooth/JavaBluetoothTransportConnection.java

@@ -14,11 +14,15 @@ import javax.microedition.io.StreamConnection;
 class JavaBluetoothTransportConnection
 		extends AbstractDuplexTransportConnection {
 
+	private final BluetoothConnectionManager connectionManager;
 	private final StreamConnection stream;
 
-	JavaBluetoothTransportConnection(Plugin plugin, StreamConnection stream) {
+	JavaBluetoothTransportConnection(Plugin plugin,
+			BluetoothConnectionManager connectionManager,
+			StreamConnection stream) {
 		super(plugin);
 		this.stream = stream;
+		this.connectionManager = connectionManager;
 	}
 
 	@Override
@@ -33,6 +37,10 @@ class JavaBluetoothTransportConnection
 
 	@Override
 	protected void closeConnection(boolean exception) throws IOException {
-		stream.close();
+		try {
+			stream.close();
+		} finally {
+			connectionManager.connectionClosed();
+		}
 	}
 }