Let Tor know if we're on an IPv6-only network.

bramble-android/src/main/java/org/briarproject/bramble/network/AndroidNetworkManager.java

@@ -1,11 +1,15 @@
 package org.briarproject.bramble.network;
 
+import android.annotation.TargetApi;
 import android.app.Application;
 import android.content.BroadcastReceiver;
 import android.content.Context;
 import android.content.Intent;
 import android.content.IntentFilter;
 import android.net.ConnectivityManager;
+import android.net.LinkAddress;
+import android.net.LinkProperties;
+import android.net.Network;
 import android.net.NetworkInfo;
 
 import org.briarproject.bramble.api.event.EventBus;
@@ -19,6 +23,11 @@ import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.bramble.api.system.TaskScheduler;
 import org.briarproject.bramble.api.system.TaskScheduler.Cancellable;
 
+import java.net.Inet4Address;
+import java.net.InetAddress;
+import java.net.NetworkInterface;
+import java.net.SocketException;
+import java.util.Enumeration;
 import java.util.concurrent.Executor;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
@@ -36,16 +45,22 @@ import static android.net.ConnectivityManager.TYPE_WIFI;
 import static android.net.wifi.p2p.WifiP2pManager.WIFI_P2P_THIS_DEVICE_CHANGED_ACTION;
 import static android.os.Build.VERSION.SDK_INT;
 import static android.os.PowerManager.ACTION_DEVICE_IDLE_MODE_CHANGED;
+import static java.net.NetworkInterface.getNetworkInterfaces;
+import static java.util.Collections.list;
 import static java.util.concurrent.TimeUnit.MINUTES;
 import static java.util.concurrent.TimeUnit.SECONDS;
 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.nullsafety.NullSafety.requireNonNull;
+import static org.briarproject.bramble.util.LogUtils.logException;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
 class AndroidNetworkManager implements NetworkManager, Service {
 
 	private static final Logger LOG =
-			Logger.getLogger(AndroidNetworkManager.class.getName());
+			getLogger(AndroidNetworkManager.class.getName());
 
 	// See android.net.wifi.WifiManager
 	private static final String WIFI_AP_STATE_CHANGED_ACTION =
@@ -54,7 +69,8 @@ class AndroidNetworkManager implements NetworkManager, Service {
 	private final TaskScheduler scheduler;
 	private final EventBus eventBus;
 	private final Executor eventExecutor;
-	private final Context appContext;
+	private final Application app;
+	private final ConnectivityManager connectivityManager;
 	private final AtomicReference<Cancellable> connectivityCheck =
 			new AtomicReference<>();
 	private final AtomicBoolean used = new AtomicBoolean(false);
@@ -67,7 +83,9 @@ class AndroidNetworkManager implements NetworkManager, Service {
 		this.scheduler = scheduler;
 		this.eventBus = eventBus;
 		this.eventExecutor = eventExecutor;
-		this.appContext = app.getApplicationContext();
+		this.app = app;
+		connectivityManager = (ConnectivityManager)
+				requireNonNull(app.getSystemService(CONNECTIVITY_SERVICE));
 	}
 
 	@Override
@@ -82,24 +100,82 @@ class AndroidNetworkManager implements NetworkManager, Service {
 		filter.addAction(WIFI_AP_STATE_CHANGED_ACTION);
 		filter.addAction(WIFI_P2P_THIS_DEVICE_CHANGED_ACTION);
 		if (SDK_INT >= 23) filter.addAction(ACTION_DEVICE_IDLE_MODE_CHANGED);
-		appContext.registerReceiver(networkStateReceiver, filter);
+		app.registerReceiver(networkStateReceiver, filter);
 	}
 
 	@Override
 	public void stopService() {
 		if (networkStateReceiver != null)
-			appContext.unregisterReceiver(networkStateReceiver);
+			app.unregisterReceiver(networkStateReceiver);
 	}
 
 	@Override
 	public NetworkStatus getNetworkStatus() {
-		ConnectivityManager cm = (ConnectivityManager)
+		NetworkInfo net = connectivityManager.getActiveNetworkInfo();
-				appContext.getSystemService(CONNECTIVITY_SERVICE);
-		if (cm == null) throw new AssertionError();
-		NetworkInfo net = cm.getActiveNetworkInfo();
 		boolean connected = net != null && net.isConnected();
-		boolean wifi = connected && net.getType() == TYPE_WIFI;
+		boolean wifi = false, ipv6Only = false;
-		return new NetworkStatus(connected, wifi);
+		if (connected) {
+			wifi = net.getType() == TYPE_WIFI;
+			if (SDK_INT >= 23) ipv6Only = isActiveNetworkIpv6Only();
+			else ipv6Only = areAllAvailableNetworksIpv6Only();
+		}
+		return new NetworkStatus(connected, wifi, ipv6Only);
+	}
+
+	/**
+	 * Returns true if the
+	 * {@link ConnectivityManager#getActiveNetwork() active network} has an
+	 * IPv6 unicast address and no IPv4 addresses. The active network is
+	 * assumed not to be a loopback interface.
+	 */
+	@TargetApi(23)
+	private boolean isActiveNetworkIpv6Only() {
+		Network net = connectivityManager.getActiveNetwork();
+		if (net == null) {
+			LOG.info("No active network");
+			return false;
+		}
+		LinkProperties props = connectivityManager.getLinkProperties(net);
+		if (props == null) {
+			LOG.info("No link properties for active network");
+			return false;
+		}
+		boolean hasIpv6Unicast = false;
+		for (LinkAddress linkAddress : props.getLinkAddresses()) {
+			InetAddress addr = linkAddress.getAddress();
+			if (addr instanceof Inet4Address) return false;
+			if (!addr.isMulticastAddress()) hasIpv6Unicast = true;
+		}
+		return hasIpv6Unicast;
+	}
+
+	/**
+	 * Returns true if the device has at least one network interface with an
+	 * IPv6 unicast address and no interfaces with IPv4 addresses, excluding
+	 * loopback interfaces and interfaces that are
+	 * {@link NetworkInterface#isUp() down}. If this method returns true and
+	 * the device has internet access then it's via IPv6 only.
+	 */
+	private boolean areAllAvailableNetworksIpv6Only() {
+		try {
+			Enumeration<NetworkInterface> interfaces = getNetworkInterfaces();
+			if (interfaces == null) {
+				LOG.info("No network interfaces");
+				return false;
+			}
+			boolean hasIpv6Unicast = false;
+			for (NetworkInterface i : list(interfaces)) {
+				if (i.isLoopback() || !i.isUp()) continue;
+				for (InetAddress addr : list(i.getInetAddresses())) {
+					if (addr instanceof Inet4Address) return false;
+					if (!addr.isMulticastAddress()) hasIpv6Unicast = true;
+				}
+			}
+			return hasIpv6Unicast;
+		} catch (SocketException e) {
+			logException(LOG, WARNING, e);
+			return false;
+		}
 	}
 
 	private void updateConnectionStatus() {

bramble-api/src/main/java/org/briarproject/bramble/api/network/NetworkStatus.java

@@ -8,11 +8,12 @@ import javax.annotation.concurrent.Immutable;
 @NotNullByDefault
 public class NetworkStatus {
 
-	private final boolean connected, wifi;
+	private final boolean connected, wifi, ipv6Only;
 
-	public NetworkStatus(boolean connected, boolean wifi) {
+	public NetworkStatus(boolean connected, boolean wifi, boolean ipv6Only) {
 		this.connected = connected;
 		this.wifi = wifi;
+		this.ipv6Only = ipv6Only;
 	}
 
 	public boolean isConnected() {
@@ -22,4 +23,8 @@ public class NetworkStatus {
 	public boolean isWifi() {
 		return wifi;
 	}
+
+	public boolean isIpv6Only() {
+		return ipv6Only;
+	}
 }

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

@@ -863,6 +863,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			if (!state.isTorRunning()) return;
 			boolean online = status.isConnected();
 			boolean wifi = status.isWifi();
+			boolean ipv6Only = status.isIpv6Only();
 			String country = locationUtils.getCurrentCountry();
 			boolean blocked =
 					circumventionProvider.isTorProbablyBlocked(country);
@@ -879,7 +880,8 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			boolean automatic = network == PREF_TOR_NETWORK_AUTOMATIC;
 
 			if (LOG.isLoggable(INFO)) {
-				LOG.info("Online: " + online + ", wifi: " + wifi);
+				LOG.info("Online: " + online + ", wifi: " + wifi
+						+ ", IPv6 only: " + ipv6Only);
 				if (country.isEmpty()) LOG.info("Country code unknown");
 				else LOG.info("Country code: " + country);
 				LOG.info("Charging: " + charging);
@@ -942,6 +944,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 				if (enableNetwork) {
 					enableBridges(enableBridges, useMeek);
 					enableConnectionPadding(enableConnectionPadding);
+					useIpv6(ipv6Only);
 				}
 				enableNetwork(enableNetwork);
 			} catch (IOException e) {
@@ -954,6 +957,11 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		controlConnection.setConf("ConnectionPadding", enable ? "1" : "0");
 	}
 
+	private void useIpv6(boolean ipv6Only) throws IOException {
+		controlConnection.setConf("ClientUseIPv4", ipv6Only ? "0" : "1");
+		controlConnection.setConf("ClientUseIPv6", ipv6Only ? "1" : "0");
+	}
+
 	@ThreadSafe
 	@NotNullByDefault
 	protected class PluginState {

bramble-java/src/main/java/org/briarproject/bramble/network/JavaNetworkManager.java

@@ -5,6 +5,8 @@ import org.briarproject.bramble.api.network.NetworkStatus;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 
+import java.net.Inet4Address;
+import java.net.InetAddress;
 import java.net.NetworkInterface;
 import java.net.SocketException;
 import java.util.Enumeration;
@@ -14,8 +16,8 @@ import javax.inject.Inject;
 
 import static java.net.NetworkInterface.getNetworkInterfaces;
 import static java.util.Collections.list;
-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.util.LogUtils.logException;
 
 @MethodsNotNullByDefault
@@ -23,7 +25,7 @@ import static org.briarproject.bramble.util.LogUtils.logException;
 class JavaNetworkManager implements NetworkManager {
 
 	private static final Logger LOG =
-			Logger.getLogger(JavaNetworkManager.class.getName());
+			getLogger(JavaNetworkManager.class.getName());
 
 	@Inject
 	JavaNetworkManager() {
@@ -31,26 +33,28 @@ class JavaNetworkManager implements NetworkManager {
 
 	@Override
 	public NetworkStatus getNetworkStatus() {
-		boolean connected = false;
+		boolean connected = false, hasIpv4 = false, hasIpv6Unicast = false;
 		try {
 			Enumeration<NetworkInterface> interfaces = getNetworkInterfaces();
-			if (interfaces != null) {
+			if (interfaces == null) {
+				LOG.info("No network interfaces");
+			} else {
 				for (NetworkInterface i : list(interfaces)) {
-					if (i.isLoopback()) continue;
+					if (i.isLoopback() || !i.isUp()) continue;
-					if (i.isUp() && i.getInetAddresses().hasMoreElements()) {
+					for (InetAddress addr : list(i.getInetAddresses())) {
-						if (LOG.isLoggable(INFO)) {
-							LOG.info("Interface " + i.getDisplayName() +
-									" is up with at least one address.");
-						}
 						connected = true;
-						break;
+						if (addr instanceof Inet4Address) {
+							hasIpv4 = true;
+						} else if (!addr.isMulticastAddress()) {
+							hasIpv6Unicast = true;
+						}
 					}
 				}
 			}
 		} catch (SocketException e) {
 			logException(LOG, WARNING, e);
 		}
-		return new NetworkStatus(connected, false);
+		return new NetworkStatus(connected, false, !hasIpv4 && hasIpv6Unicast);
 	}
 
 }