Use reflected Bluetooth address if we don't know our own address.

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

@@ -10,6 +10,9 @@ public interface BluetoothConstants {
 	String PROP_ADDRESS = "address";
 	String PROP_UUID = "uuid";
 
+	// Local settings (not shared with contacts)
+	String PREF_ADDRESS_IS_REFLECTED = "addressIsReflected";
+
 	// Default value for PREF_PLUGIN_ENABLE
 	boolean DEFAULT_PREF_PLUGIN_ENABLE = false;
 }

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

@@ -1,6 +1,7 @@
 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;
@@ -25,6 +26,7 @@ import org.briarproject.bramble.api.plugin.event.BluetoothEnabledEvent;
 import org.briarproject.bramble.api.plugin.event.DisableBluetoothEvent;
 import org.briarproject.bramble.api.plugin.event.EnableBluetoothEvent;
 import org.briarproject.bramble.api.properties.TransportProperties;
+import org.briarproject.bramble.api.properties.event.RemoteTransportPropertiesUpdatedEvent;
 import org.briarproject.bramble.api.rendezvous.KeyMaterialSource;
 import org.briarproject.bramble.api.rendezvous.RendezvousEndpoint;
 import org.briarproject.bramble.api.settings.Settings;
@@ -48,6 +50,7 @@ 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_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.PROP_ADDRESS;
 import static org.briarproject.bramble.api.plugin.BluetoothConstants.PROP_UUID;
 import static org.briarproject.bramble.api.plugin.BluetoothConstants.UUID_BYTES;
@@ -55,6 +58,7 @@ import static org.briarproject.bramble.api.plugin.Plugin.State.ACTIVE;
 import static org.briarproject.bramble.api.plugin.Plugin.State.DISABLED;
 import static org.briarproject.bramble.api.plugin.Plugin.State.INACTIVE;
 import static org.briarproject.bramble.api.plugin.Plugin.State.STARTING_STOPPING;
+import static org.briarproject.bramble.api.properties.TransportPropertyConstants.REFLECTED_PROPERTY_PREFIX;
 import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.bramble.util.PrivacyUtils.scrubMacAddress;
 import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
@@ -205,25 +209,64 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 		TransportProperties p = callback.getLocalProperties();
 		String address = p.get(PROP_ADDRESS);
 		String uuid = p.get(PROP_UUID);
+		Settings s = callback.getSettings();
+		boolean isReflected = s.getBoolean(PREF_ADDRESS_IS_REFLECTED, false);
 		boolean changed = false;
-		if (address == null) {
+		if (address == null || isReflected) {
 			address = getBluetoothAddress();
-			if (LOG.isLoggable(INFO))
+			if (LOG.isLoggable(INFO)) {
 				LOG.info("Local address " + scrubMacAddress(address));
-			if (!isNullOrEmpty(address)) {
+			}
-				p.put(PROP_ADDRESS, address);
+			if (address == null) {
+				address = getReflectedAddress();
+				if (LOG.isLoggable(INFO)) {
+					LOG.info("Reflected address " + scrubMacAddress(address));
+				}
+				if (address != null) {
+					changed = true;
+					isReflected = true;
+				}
+			} else {
 				changed = true;
+				isReflected = false;
 			}
 		}
 		if (uuid == null) {
 			byte[] random = new byte[UUID_BYTES];
 			secureRandom.nextBytes(random);
 			uuid = UUID.nameUUIDFromBytes(random).toString();
-			p.put(PROP_UUID, uuid);
 			changed = true;
 		}
 		contactConnectionsUuid = uuid;
-		if (changed) callback.mergeLocalProperties(p);
+		if (changed) {
+			p = new TransportProperties();
+			// If we previously used a reflected address and there's no longer
+			// a reflected address with enough votes to be used, we'll continue
+			// to use the old reflected address until there's a new winner
+			if (address != null) p.put(PROP_ADDRESS, address);
+			p.put(PROP_UUID, uuid);
+			callback.mergeLocalProperties(p);
+			s = new Settings();
+			s.putBoolean(PREF_ADDRESS_IS_REFLECTED, isReflected);
+			callback.mergeSettings(s);
+		}
+	}
+
+	@Nullable
+	private String getReflectedAddress() {
+		// Count the number of votes for each reflected address
+		String key = REFLECTED_PROPERTY_PREFIX + PROP_ADDRESS;
+		Multiset<String> votes = new Multiset<>();
+		for (TransportProperties p : callback.getRemoteProperties()) {
+			String address = p.get(key);
+			if (address != null && isValidAddress(address)) votes.add(address);
+		}
+		// If an address gets more than half of the votes, accept it
+		int total = votes.getTotal();
+		for (String address : votes.keySet()) {
+			if (votes.getCount(address) * 2 > total) return address;
+		}
+		return null;
 	}
 
 	private void acceptContactConnections(SS ss) {
@@ -429,6 +472,12 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 			ioExecutor.execute(connectionLimiter::keyAgreementStarted);
 		} else if (e instanceof KeyAgreementStoppedListeningEvent) {
 			ioExecutor.execute(connectionLimiter::keyAgreementEnded);
+		} else if (e instanceof RemoteTransportPropertiesUpdatedEvent) {
+			RemoteTransportPropertiesUpdatedEvent r =
+					(RemoteTransportPropertiesUpdatedEvent) e;
+			if (r.getTransportId().equals(ID)) {
+				ioExecutor.execute(this::updateProperties);
+			}
 		}
 	}