Add comment explaining relationship between constants.

.gitlab-ci.yml

@@ -98,7 +98,7 @@ bridge test:
       allow_failure: true
   script:
     - OPTIONAL_TESTS=org.briarproject.bramble.plugin.tor.BridgeTest ./gradlew --info bramble-java:test --tests BridgeTest
-  timeout: 4h
+  timeout: 3h
 
 mailbox integration test:
   extends: .optional_tests

CONTRIBUTING.md

@@ -1,10 +0,0 @@
-Folder-Description:
-===================
-* `briar-*`: Specifically for the Briar app (Phone/Desktop/Headless)
-* `bramble-*`: The protocol stack - not necessarily Briar-dependent
-
----
-
-* `*-api`: public stuff that can be referenced from other packages and modules - mostly interfaces + a few utility classes
-* `*-core`: implementations of api that are portable across Android/Desktop/Headless
-* `*-java`: implementations of api that are specific to Desktop & Headless

bramble-android/build.gradle

@@ -15,8 +15,8 @@ android {
 	defaultConfig {
 		minSdkVersion 16
 		targetSdkVersion 30
-		versionCode 10412
-		versionName "1.4.12"
+		versionCode 10408
+		versionName "1.4.8"
 		consumerProguardFiles 'proguard-rules.txt'
 
 		testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
@@ -42,10 +42,8 @@ configurations {
 
 dependencies {
 	implementation project(path: ':bramble-core', configuration: 'default')
-	implementation 'androidx.annotation:annotation:1.5.0'
 	tor "org.briarproject:tor-android:$tor_version"
 	tor "org.briarproject:obfs4proxy-android:$obfs4proxy_version"
-	tor "org.briarproject:snowflake-android:$snowflake_version"
 
 	annotationProcessor "com.google.dagger:dagger-compiler:$dagger_version"
 

bramble-android/proguard-rules.txt

@@ -18,7 +18,3 @@
 -dontnote com.google.common.**
 
 -dontwarn com.fasterxml.jackson.databind.ext.Java7SupportImpl
-
-# Keep all Jackson-serialisable classes and their members
--keep interface com.fasterxml.jackson.databind.annotation.JsonSerialize
--keep @com.fasterxml.jackson.databind.annotation.JsonSerialize class * { *; }

bramble-android/src/main/java/org/briarproject/bramble/BrambleAndroidModule.java

@@ -1,7 +1,6 @@
 package org.briarproject.bramble;
 
 import org.briarproject.bramble.battery.AndroidBatteryModule;
-import org.briarproject.bramble.io.DnsModule;
 import org.briarproject.bramble.network.AndroidNetworkModule;
 import org.briarproject.bramble.plugin.tor.CircumventionModule;
 import org.briarproject.bramble.reporting.ReportingModule;
@@ -19,7 +18,6 @@ import dagger.Module;
 		AndroidTaskSchedulerModule.class,
 		AndroidWakefulIoExecutorModule.class,
 		CircumventionModule.class,
-		DnsModule.class,
 		ReportingModule.class,
 		SocksModule.class
 })

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

@@ -86,8 +86,8 @@ public class AndroidBluetoothPluginFactory implements DuplexPluginFactory {
 		BluetoothConnectionFactory<BluetoothSocket> connectionFactory =
 				new AndroidBluetoothConnectionFactory(connectionLimiter,
 						wakeLockManager, timeoutMonitor);
-		Backoff backoff = backoffFactory.createBackoff(MIN_POLLING_INTERVAL,
-				MAX_POLLING_INTERVAL, BACKOFF_BASE);
+		Backoff backoff = backoffFactory.createBackoff(eventBus, ID,
+				MIN_POLLING_INTERVAL, MAX_POLLING_INTERVAL, BACKOFF_BASE);
 		AndroidBluetoothPlugin plugin = new AndroidBluetoothPlugin(
 				connectionLimiter, connectionFactory, ioExecutor,
 				wakefulIoExecutor, secureRandom, androidExecutor, app,

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

@@ -61,8 +61,8 @@ public class AndroidLanTcpPluginFactory implements DuplexPluginFactory {
 
 	@Override
 	public DuplexPlugin createPlugin(PluginCallback callback) {
-		Backoff backoff = backoffFactory.createBackoff(MIN_POLLING_INTERVAL,
-				MAX_POLLING_INTERVAL, BACKOFF_BASE);
+		Backoff backoff = backoffFactory.createBackoff(eventBus, ID,
+				MIN_POLLING_INTERVAL, MAX_POLLING_INTERVAL, BACKOFF_BASE);
 		AndroidLanTcpPlugin plugin = new AndroidLanTcpPlugin(ioExecutor,
 				wakefulIoExecutor, app, backoff, callback,
 				MAX_LATENCY, MAX_IDLE_TIME, CONNECTION_TIMEOUT);

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

@@ -9,7 +9,6 @@ import org.briarproject.bramble.api.battery.BatteryManager;
 import org.briarproject.bramble.api.network.NetworkManager;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
-import org.briarproject.bramble.api.plugin.Backoff;
 import org.briarproject.bramble.api.plugin.PluginCallback;
 import org.briarproject.bramble.api.system.AndroidWakeLock;
 import org.briarproject.bramble.api.system.AndroidWakeLockManager;
@@ -31,8 +30,6 @@ import java.util.zip.ZipInputStream;
 
 import javax.net.SocketFactory;
 
-import androidx.annotation.ChecksSdkIntAtLeast;
-
 import static android.os.Build.VERSION.SDK_INT;
 import static java.util.Arrays.asList;
 import static java.util.logging.Level.INFO;
@@ -47,14 +44,13 @@ class AndroidTorPlugin extends TorPlugin {
 
 	private static final String TOR_LIB_NAME = "libtor.so";
 	private static final String OBFS4_LIB_NAME = "libobfs4proxy.so";
-	private static final String SNOWFLAKE_LIB_NAME = "libsnowflake.so";
 
 	private static final Logger LOG =
 			getLogger(AndroidTorPlugin.class.getName());
 
 	private final Application app;
 	private final AndroidWakeLock wakeLock;
-	private final File torLib, obfs4Lib, snowflakeLib;
+	private final File torLib, obfs4Lib;
 
 	AndroidTorPlugin(Executor ioExecutor,
 			Executor wakefulIoExecutor,
@@ -67,7 +63,6 @@ class AndroidTorPlugin extends TorPlugin {
 			CircumventionProvider circumventionProvider,
 			BatteryManager batteryManager,
 			AndroidWakeLockManager wakeLockManager,
-			Backoff backoff,
 			TorRendezvousCrypto torRendezvousCrypto,
 			PluginCallback callback,
 			String architecture,
@@ -78,7 +73,7 @@ class AndroidTorPlugin extends TorPlugin {
 			int torControlPort) {
 		super(ioExecutor, wakefulIoExecutor, networkManager, locationUtils,
 				torSocketFactory, clock, resourceProvider,
-				circumventionProvider, batteryManager, backoff,
+				circumventionProvider, batteryManager,
 				torRendezvousCrypto, callback, architecture, maxLatency,
 				maxIdleTime, torDirectory, torSocksPort, torControlPort);
 		this.app = app;
@@ -86,7 +81,6 @@ class AndroidTorPlugin extends TorPlugin {
 		String nativeLibDir = app.getApplicationInfo().nativeLibraryDir;
 		torLib = new File(nativeLibDir, TOR_LIB_NAME);
 		obfs4Lib = new File(nativeLibDir, OBFS4_LIB_NAME);
-		snowflakeLib = new File(nativeLibDir, SNOWFLAKE_LIB_NAME);
 	}
 
 	@Override
@@ -112,12 +106,6 @@ class AndroidTorPlugin extends TorPlugin {
 		if (!enable) wakeLock.release();
 	}
 
-	@Override
-	@ChecksSdkIntAtLeast(api = 25)
-	protected boolean canVerifyLetsEncryptCerts() {
-		return SDK_INT >= 25;
-	}
-
 	@Override
 	public void stop() {
 		super.stop();
@@ -134,43 +122,39 @@ class AndroidTorPlugin extends TorPlugin {
 		return obfs4Lib.exists() ? obfs4Lib : super.getObfs4ExecutableFile();
 	}
 
-	@Override
-	protected File getSnowflakeExecutableFile() {
-		return snowflakeLib.exists()
-				? snowflakeLib : super.getSnowflakeExecutableFile();
-	}
-
 	@Override
 	protected void installTorExecutable() throws IOException {
-		installExecutable(super.getTorExecutableFile(), torLib, TOR_LIB_NAME);
+		File extracted = super.getTorExecutableFile();
+		if (torLib.exists()) {
+			// If an older version left behind a Tor binary, delete it
+			if (extracted.exists()) {
+				if (extracted.delete()) LOG.info("Deleted Tor binary");
+				else LOG.info("Failed to delete Tor binary");
+			}
+		} else if (SDK_INT < 29) {
+			// The binary wasn't extracted at install time. Try to extract it
+			extractLibraryFromApk(TOR_LIB_NAME, extracted);
+		} else {
+			// No point extracting the binary, we won't be allowed to execute it
+			throw new FileNotFoundException(torLib.getAbsolutePath());
+		}
 	}
 
 	@Override
 	protected void installObfs4Executable() throws IOException {
-		installExecutable(super.getObfs4ExecutableFile(), obfs4Lib,
-				OBFS4_LIB_NAME);
-	}
-
-	@Override
-	protected void installSnowflakeExecutable() throws IOException {
-		installExecutable(super.getSnowflakeExecutableFile(), snowflakeLib,
-				SNOWFLAKE_LIB_NAME);
-	}
-
-	private void installExecutable(File extracted, File lib, String libName)
-			throws IOException {
-		if (lib.exists()) {
-			// If an older version left behind a binary, delete it
+		File extracted = super.getObfs4ExecutableFile();
+		if (obfs4Lib.exists()) {
+			// If an older version left behind an obfs4 binary, delete it
 			if (extracted.exists()) {
-				if (extracted.delete()) LOG.info("Deleted old binary");
-				else LOG.info("Failed to delete old binary");
+				if (extracted.delete()) LOG.info("Deleted obfs4 binary");
+				else LOG.info("Failed to delete obfs4 binary");
 			}
 		} else if (SDK_INT < 29) {
 			// The binary wasn't extracted at install time. Try to extract it
-			extractLibraryFromApk(libName, extracted);
+			extractLibraryFromApk(OBFS4_LIB_NAME, extracted);
 		} else {
 			// No point extracting the binary, we won't be allowed to execute it
-			throw new FileNotFoundException(lib.getAbsolutePath());
+			throw new FileNotFoundException(obfs4Lib.getAbsolutePath());
 		}
 	}
 

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

@@ -8,8 +8,6 @@ import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.lifecycle.IoExecutor;
 import org.briarproject.bramble.api.network.NetworkManager;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-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;
@@ -44,7 +42,6 @@ public class AndroidTorPluginFactory extends TorPluginFactory {
 			LocationUtils locationUtils,
 			EventBus eventBus,
 			SocketFactory torSocketFactory,
-			BackoffFactory backoffFactory,
 			ResourceProvider resourceProvider,
 			CircumventionProvider circumventionProvider,
 			BatteryManager batteryManager,
@@ -56,7 +53,7 @@ public class AndroidTorPluginFactory extends TorPluginFactory {
 			Application app,
 			AndroidWakeLockManager wakeLockManager) {
 		super(ioExecutor, wakefulIoExecutor, networkManager, locationUtils,
-				eventBus, torSocketFactory, backoffFactory, resourceProvider,
+				eventBus, torSocketFactory, resourceProvider,
 				circumventionProvider, batteryManager, clock, crypto,
 				torDirectory, torSocksPort, torControlPort);
 		this.app = app;
@@ -76,14 +73,14 @@ public class AndroidTorPluginFactory extends TorPluginFactory {
 	}
 
 	@Override
-	TorPlugin createPluginInstance(Backoff backoff,
-			TorRendezvousCrypto torRendezvousCrypto, PluginCallback callback,
+	TorPlugin createPluginInstance(TorRendezvousCrypto torRendezvousCrypto,
+			PluginCallback callback,
 			String architecture) {
 		return new AndroidTorPlugin(ioExecutor,
 				wakefulIoExecutor, app, networkManager, locationUtils,
 				torSocketFactory, clock, resourceProvider,
 				circumventionProvider, batteryManager, wakeLockManager,
-				backoff, torRendezvousCrypto, callback, architecture,
+				torRendezvousCrypto, callback, architecture,
 				MAX_LATENCY, MAX_IDLE_TIME, torDirectory, torSocksPort,
 				torControlPort);
 	}

bramble-android/witness.gradle

@@ -1,6 +1,5 @@
 dependencyVerification {
     verify = [
-        'androidx.annotation:annotation:1.5.0:annotation-1.5.0.jar:261fb7c0210858500bab66d34354972a75166ab4182add283780b05513d6ec4a',
         'cglib:cglib:3.2.8:cglib-3.2.8.jar:3f64de999ecc5595dc84ca8ff0879d8a34c8623f9ef3c517a53ed59023fcb9db',
         'com.android.tools.analytics-library:protos:30.0.3:protos-30.0.3.jar:f62b89dcd9de719c6a7b7e15fb1dd20e45b57222e675cf633607bd0ed6bca7e7',
         'com.android.tools.analytics-library:shared:30.0.3:shared-30.0.3.jar:05aa9ba3cc890354108521fdf99802565aae5dd6ca44a6ac8bb8d594d1c1cd15',
@@ -88,9 +87,8 @@ dependencyVerification {
         'org.apache.httpcomponents:httpmime:4.5.6:httpmime-4.5.6.jar:0b2b1102c18d3c7e05a77214b9b7501a6f6056174ae5604e0e256776eda7553e',
         'org.bouncycastle:bcpkix-jdk15on:1.56:bcpkix-jdk15on-1.56.jar:7043dee4e9e7175e93e0b36f45b1ec1ecb893c5f755667e8b916eb8dd201c6ca',
         'org.bouncycastle:bcprov-jdk15on:1.56:bcprov-jdk15on-1.56.jar:963e1ee14f808ffb99897d848ddcdb28fa91ddda867eb18d303e82728f878349',
-        'org.briarproject:obfs4proxy-android:0.0.14:obfs4proxy-android-0.0.14.jar:ad9b1ee4757b05867a19e993147bbb018bddd1f26ce3da746d5f037d5991a8c8',
-        'org.briarproject:snowflake-android:2.3.1:snowflake-android-2.3.1.jar:1f83c9a070f87b7074af13627709a8b5aced5460104be7166af736b1bb73c293',
-        'org.briarproject:tor-android:0.4.5.14:tor-android-0.4.5.14.jar:7cf1beaa6c1db51fc8fac263aba9624ef289c3db29772509efcbc59f7057330a',
+        'org.briarproject:obfs4proxy-android:0.0.12:obfs4proxy-android-0.0.12.jar:84159d2a4668abc40e3fccaa1f6fa0c04892863f9eb80a866ac8928d9f9a7e89',
+        'org.briarproject:tor-android:0.4.5.12-2:tor-android-0.4.5.12-2.jar:8545dbcef2bb6aa89c32bb6f8ac51f7a64bce3ae85845b3578ffdeb9b206feb9',
         'org.checkerframework:checker-compat-qual:2.5.3:checker-compat-qual-2.5.3.jar:d76b9afea61c7c082908023f0cbc1427fab9abd2df915c8b8a3e7a509bccbc6d',
         'org.checkerframework:checker-qual:2.5.2:checker-qual-2.5.2.jar:64b02691c8b9d4e7700f8ee2e742dce7ea2c6e81e662b7522c9ee3bf568c040a',
         'org.checkerframework:checker-qual:3.5.0:checker-qual-3.5.0.jar:729990b3f18a95606fc2573836b6958bcdb44cb52bfbd1b7aa9c339cff35a5a4',
@@ -131,12 +129,10 @@ dependencyVerification {
         'org.jetbrains.kotlin:kotlin-reflect:1.4.32:kotlin-reflect-1.4.32.jar:dbf19e9cdaa9c3c170f3f6f6ce3922f38dfc1d7fa1cab5b7c23a19da8b5eec5b',
         'org.jetbrains.kotlin:kotlin-stdlib-common:1.4.20:kotlin-stdlib-common-1.4.20.jar:a7112c9b3cefee418286c9c9372f7af992bd1e6e030691d52f60cb36dbec8320',
         'org.jetbrains.kotlin:kotlin-stdlib-common:1.4.32:kotlin-stdlib-common-1.4.32.jar:e1ff6f55ee9e7591dcc633f7757bac25a7edb1cc7f738b37ec652f10f66a4145',
-        'org.jetbrains.kotlin:kotlin-stdlib-common:1.7.10:kotlin-stdlib-common-1.7.10.jar:19f102efe9629f8eabc63853ad15c533e47c47f91fca09285c5bde86e59f91d4',
         'org.jetbrains.kotlin:kotlin-stdlib-jdk7:1.4.32:kotlin-stdlib-jdk7-1.4.32.jar:5f801e75ca27d8791c14b07943c608da27620d910a8093022af57f543d5d98b6',
         'org.jetbrains.kotlin:kotlin-stdlib-jdk8:1.4.32:kotlin-stdlib-jdk8-1.4.32.jar:adc43e54757b106e0cd7b3b7aa257dff471b61efdabe067fc02b2f57e2396262',
         'org.jetbrains.kotlin:kotlin-stdlib:1.4.20:kotlin-stdlib-1.4.20.jar:b8ab1da5cdc89cb084d41e1f28f20a42bd431538642a5741c52bbfae3fa3e656',
         'org.jetbrains.kotlin:kotlin-stdlib:1.4.32:kotlin-stdlib-1.4.32.jar:13e9fd3e69dc7230ce0fc873a92a4e5d521d179bcf1bef75a6705baac3bfecba',
-        'org.jetbrains.kotlin:kotlin-stdlib:1.7.10:kotlin-stdlib-1.7.10.jar:e771fe74250a943e8f6346713201ff1d8cb95c3a5d1a91a22b65a9e04f6a8901',
         'org.jetbrains.kotlinx:kotlinx-metadata-jvm:0.1.0:kotlinx-metadata-jvm-0.1.0.jar:9753bb39efef35957c5c15df9a3cb769aabf2cdfa74b47afcb7760e5146be3b5',
         'org.jetbrains:annotations:13.0:annotations-13.0.jar:ace2a10dc8e2d5fd34925ecac03e4988b2c0f851650c94b8cef49ba1bd111478',
         'org.jmock:jmock-imposters:2.12.0:jmock-imposters-2.12.0.jar:3b836269745a137c9b2347e8d7c2104845b126ef04f012d6bfd94f1a7dea7b09',

bramble-api/src/main/java/org/briarproject/bramble/api/connection/ConnectionManager.java

@@ -7,7 +7,6 @@ import org.briarproject.bramble.api.plugin.TransportConnectionReader;
 import org.briarproject.bramble.api.plugin.TransportConnectionWriter;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
-import org.briarproject.bramble.api.sync.OutgoingSessionRecord;
 
 @NotNullByDefault
 public interface ConnectionManager {
@@ -46,14 +45,6 @@ public interface ConnectionManager {
 	void manageOutgoingConnection(ContactId c, TransportId t,
 			TransportConnectionWriter w);
 
-	/**
-	 * Manages an outgoing connection to a contact via a mailbox. The IDs of
-	 * any messages sent or acked are added to the given
-	 * {@link OutgoingSessionRecord}.
-	 */
-	void manageOutgoingConnection(ContactId c, TransportId t,
-			TransportConnectionWriter w, OutgoingSessionRecord sessionRecord);
-
 	/**
 	 * Manages an outgoing connection to a contact over a duplex transport.
 	 */

bramble-api/src/main/java/org/briarproject/bramble/api/db/DatabaseComponent.java

@@ -126,11 +126,16 @@ public interface DatabaseComponent extends TransactionManager {
 			TransportKeys k) throws DbException;
 
 	/**
-	 * Returns true if there are any acks to send to the given contact.
+	 * Returns true if there are any acks or messages to send to the given
+	 * contact over a transport with the given maximum latency.
 	 * <p/>
 	 * Read-only.
+	 *
+	 * @param eager True if messages that are not yet due for retransmission
+	 * should be included
 	 */
-	boolean containsAcksToSend(Transaction txn, ContactId c) throws DbException;
+	boolean containsAnythingToSend(Transaction txn, ContactId c,
+			long maxLatency, boolean eager) throws DbException;
 
 	/**
 	 * Returns true if the database contains the given contact for the given
@@ -156,18 +161,6 @@ public interface DatabaseComponent extends TransactionManager {
 	 */
 	boolean containsIdentity(Transaction txn, AuthorId a) throws DbException;
 
-	/**
-	 * Returns true if there are any messages to send to the given contact
-	 * over a transport with the given maximum latency.
-	 * <p/>
-	 * Read-only.
-	 *
-	 * @param eager True if messages that are not yet due for retransmission
-	 * should be included
-	 */
-	boolean containsMessagesToSend(Transaction txn, ContactId c,
-			long maxLatency, boolean eager) throws DbException;
-
 	/**
 	 * Returns true if the database contains the given pending contact.
 	 * <p/>
@@ -283,13 +276,6 @@ public interface DatabaseComponent extends TransactionManager {
 	 */
 	Group getGroup(Transaction txn, GroupId g) throws DbException;
 
-	/**
-	 * Returns the ID of the group containing the given message.
-	 * <p/>
-	 * Read-only.
-	 */
-	GroupId getGroupId(Transaction txn, MessageId m) throws DbException;
-
 	/**
 	 * Returns the metadata for the given group.
 	 * <p/>
@@ -356,13 +342,13 @@ public interface DatabaseComponent extends TransactionManager {
 			Metadata query) throws DbException;
 
 	/**
-	 * Returns the IDs of all messages received from the given contact that
-	 * need to be acknowledged.
+	 * Returns the IDs of some messages received from the given contact that
+	 * need to be acknowledged, up to the given number of messages.
 	 * <p/>
 	 * Read-only.
 	 */
-	Collection<MessageId> getMessagesToAck(Transaction txn, ContactId c)
-			throws DbException;
+	Collection<MessageId> getMessagesToAck(Transaction txn, ContactId c,
+			int maxMessages) throws DbException;
 
 	/**
 	 * Returns the IDs of some messages that are eligible to be sent to the
@@ -499,8 +485,6 @@ public interface DatabaseComponent extends TransactionManager {
 	 * Returns the message with the given ID for transmission to the given
 	 * contact over a transport with the given maximum latency. Returns null
 	 * if the message is no longer visible to the contact.
-	 * <p/>
-	 * Read-only if {@code markAsSent} is false.
 	 *
 	 * @param markAsSent True if the message should be marked as sent.
 	 * If false it can be marked as sent by calling
@@ -550,18 +534,15 @@ public interface DatabaseComponent extends TransactionManager {
 	 */
 	long getNextCleanupDeadline(Transaction txn) throws DbException;
 
-	/**
+	/*
 	 * Returns the next time (in milliseconds since the Unix epoch) when a
-	 * message is due to be sent to the given contact over a transport with
-	 * the given latency.
-	 * <p>
-	 * The returned value may be zero if a message is due to be sent
-	 * immediately, or Long.MAX_VALUE if no messages are scheduled to be sent.
+	 * message is due to be sent to the given contact. The returned value may
+	 * be zero if a message is due to be sent immediately, or Long.MAX_VALUE if
+	 * no messages are scheduled to be sent.
 	 * <p/>
 	 * Read-only.
 	 */
-	long getNextSendTime(Transaction txn, ContactId c, long maxLatency)
-			throws DbException;
+	long getNextSendTime(Transaction txn, ContactId c) throws DbException;
 
 	/**
 	 * Returns the pending contact with the given ID.

bramble-api/src/main/java/org/briarproject/bramble/api/lifecycle/LifecycleManager.java

@@ -37,14 +37,8 @@ public interface LifecycleManager {
 	 */
 	enum LifecycleState {
 
-		CREATED,
-		STARTING,
-		MIGRATING_DATABASE,
-		COMPACTING_DATABASE,
-		STARTING_SERVICES,
-		RUNNING,
-		STOPPING,
-		STOPPED;
+		STARTING, MIGRATING_DATABASE, COMPACTING_DATABASE, STARTING_SERVICES,
+		RUNNING, STOPPING;
 
 		public boolean isAfter(LifecycleState state) {
 			return ordinal() > state.ordinal();

bramble-api/src/main/java/org/briarproject/bramble/api/mailbox/MailboxConstants.java

@@ -5,7 +5,6 @@ import org.briarproject.bramble.api.plugin.TransportId;
 import java.util.List;
 
 import static java.util.Collections.singletonList;
-import static java.util.concurrent.TimeUnit.DAYS;
 import static java.util.concurrent.TimeUnit.HOURS;
 import static org.briarproject.bramble.api.transport.TransportConstants.MAX_FRAME_LENGTH;
 import static org.briarproject.bramble.api.transport.TransportConstants.MAX_PAYLOAD_LENGTH;
@@ -66,8 +65,4 @@ public interface MailboxConstants {
 	 */
 	long PROBLEM_MS_SINCE_LAST_SUCCESS = HOURS.toMillis(1);
 
-	/**
-	 * The maximum latency of the mailbox transport in milliseconds.
-	 */
-	long MAX_LATENCY = DAYS.toMillis(14);
 }

bramble-api/src/main/java/org/briarproject/bramble/api/mailbox/MailboxHelper.java

@@ -1,22 +1,19 @@
 package org.briarproject.bramble.api.mailbox;
 
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-
 import java.util.List;
 import java.util.TreeSet;
 
 import static org.briarproject.bramble.api.mailbox.MailboxConstants.API_CLIENT_TOO_OLD;
 import static org.briarproject.bramble.api.mailbox.MailboxConstants.API_SERVER_TOO_OLD;
 
-@NotNullByDefault
-public class MailboxHelper {
+class MailboxHelper {
 
 	/**
 	 * Returns the highest major version that both client and server support
 	 * or {@link MailboxConstants#API_SERVER_TOO_OLD} if the server is too old
 	 * or {@link MailboxConstants#API_CLIENT_TOO_OLD} if the client is too old.
 	 */
-	public static int getHighestCommonMajorVersion(
+	static int getHighestCommonMajorVersion(
 			List<MailboxVersion> client, List<MailboxVersion> server) {
 		TreeSet<Integer> clientVersions = new TreeSet<>();
 		for (MailboxVersion version : client) {
@@ -35,13 +32,4 @@ public class MailboxHelper {
 		return API_SERVER_TOO_OLD;
 	}
 
-	/**
-	 * Returns true if a client and server with the given API versions can
-	 * communicate with each other (ie, have any major API versions in common).
-	 */
-	public static boolean isClientCompatibleWithServer(
-			List<MailboxVersion> client, List<MailboxVersion> server) {
-		int common = getHighestCommonMajorVersion(client, server);
-		return common != API_CLIENT_TOO_OLD && common != API_SERVER_TOO_OLD;
-	}
 }

bramble-api/src/main/java/org/briarproject/bramble/api/mailbox/MailboxId.java

@@ -2,7 +2,6 @@ package org.briarproject.bramble.api.mailbox;
 
 import com.fasterxml.jackson.annotation.JsonValue;
 
-import org.briarproject.bramble.api.FormatException;
 import org.briarproject.bramble.api.UniqueId;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 
@@ -33,7 +32,7 @@ public abstract class MailboxId extends UniqueId {
 		}
 		try {
 			return fromHexString(token);
-		} catch (FormatException e) {
+		} catch (IllegalArgumentException e) {
 			throw new InvalidMailboxIdException();
 		}
 	}

bramble-api/src/main/java/org/briarproject/bramble/api/mailbox/MailboxProperties.java

@@ -1,7 +1,6 @@
 package org.briarproject.bramble.api.mailbox;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.nullsafety.NullSafety;
 
 import java.util.List;
 
@@ -12,7 +11,7 @@ import javax.annotation.concurrent.Immutable;
 @NotNullByDefault
 public class MailboxProperties {
 
-	private final String onion;
+	private final String baseUrl;
 	private final MailboxAuthToken authToken;
 	private final boolean owner;
 	private final List<MailboxVersion> serverSupports;
@@ -24,9 +23,9 @@ public class MailboxProperties {
 	/**
 	 * Constructor for properties used by the mailbox's owner.
 	 */
-	public MailboxProperties(String onion, MailboxAuthToken authToken,
+	public MailboxProperties(String baseUrl, MailboxAuthToken authToken,
 			List<MailboxVersion> serverSupports) {
-		this.onion = onion;
+		this.baseUrl = baseUrl;
 		this.authToken = authToken;
 		this.owner = true;
 		this.serverSupports = serverSupports;
@@ -37,10 +36,10 @@ public class MailboxProperties {
 	/**
 	 * Constructor for properties used by a contact of the mailbox's owner.
 	 */
-	public MailboxProperties(String onion, MailboxAuthToken authToken,
+	public MailboxProperties(String baseUrl, MailboxAuthToken authToken,
 			List<MailboxVersion> serverSupports, MailboxFolderId inboxId,
 			MailboxFolderId outboxId) {
-		this.onion = onion;
+		this.baseUrl = baseUrl;
 		this.authToken = authToken;
 		this.owner = false;
 		this.serverSupports = serverSupports;
@@ -48,11 +47,13 @@ public class MailboxProperties {
 		this.outboxId = outboxId;
 	}
 
-	/**
-	 * Returns the onion address of the mailbox, excluding the .onion suffix.
-	 */
+	public String getBaseUrl() {
+		return baseUrl;
+	}
+
 	public String getOnion() {
-		return onion;
+		return baseUrl.replaceFirst("^http://", "")
+				.replaceFirst("\\.onion$", "");
 	}
 
 	public MailboxAuthToken getAuthToken() {
@@ -76,23 +77,4 @@ public class MailboxProperties {
 	public MailboxFolderId getOutboxId() {
 		return outboxId;
 	}
-
-	@Override
-	public boolean equals(Object o) {
-		if (o instanceof MailboxProperties) {
-			MailboxProperties m = (MailboxProperties) o;
-			return owner == m.owner &&
-					onion.equals(m.onion) &&
-					authToken.equals(m.authToken) &&
-					NullSafety.equals(inboxId, m.inboxId) &&
-					NullSafety.equals(outboxId, m.outboxId) &&
-					serverSupports.equals(m.serverSupports);
-		}
-		return false;
-	}
-
-	@Override
-	public int hashCode() {
-		return authToken.hashCode();
-	}
 }

bramble-api/src/main/java/org/briarproject/bramble/api/mailbox/MailboxSettingsManager.java

@@ -32,8 +32,8 @@ public interface MailboxSettingsManager {
 
 	MailboxStatus getOwnMailboxStatus(Transaction txn) throws DbException;
 
-	void recordSuccessfulConnection(Transaction txn, long now,
-			List<MailboxVersion> versions) throws DbException;
+	void recordSuccessfulConnection(Transaction txn, long now)
+			throws DbException;
 
 	void recordFailedConnectionAttempt(Transaction txn, long now)
 			throws DbException;
@@ -46,28 +46,20 @@ public interface MailboxSettingsManager {
 
 	interface MailboxHook {
 		/**
-		 * Called when Briar is paired with a mailbox.
+		 * Called when Briar is paired with a mailbox
 		 *
 		 * @param txn A read-write transaction
+		 * @param ownOnion Our new mailbox's onion (56 base32 chars)
 		 */
-		void mailboxPaired(Transaction txn, MailboxProperties p)
+		void mailboxPaired(Transaction txn, String ownOnion,
+				List<MailboxVersion> serverSupports)
 				throws DbException;
 
 		/**
-		 * Called when the mailbox is unpaired.
+		 * Called when the mailbox is unpaired
 		 *
 		 * @param txn A read-write transaction
 		 */
 		void mailboxUnpaired(Transaction txn) throws DbException;
-
-		/**
-		 * Called when we receive our mailbox's server-supported API versions.
-		 * This happens whenever we successfully check the connectivity of
-		 * our mailbox, so this hook may be called frequently.
-		 *
-		 * @param txn A read-write transaction
-		 */
-		void serverSupportedVersionsReceived(Transaction txn,
-				List<MailboxVersion> serverSupports) throws DbException;
 	}
 }

bramble-api/src/main/java/org/briarproject/bramble/api/mailbox/MailboxStatus.java

@@ -67,13 +67,6 @@ public class MailboxStatus {
 		return attemptsSinceSuccess;
 	}
 
-	/**
-	 * Returns the mailbox's supported API versions.
-	 */
-	public List<MailboxVersion> getServerSupports() {
-		return serverSupports;
-	}
-
 	/**
 	 * @return true if this status indicates a problem with the mailbox.
 	 */

bramble-api/src/main/java/org/briarproject/bramble/api/mailbox/MailboxUpdateManager.java

@@ -29,35 +29,19 @@ public interface MailboxUpdateManager {
 
 	/**
 	 * The number of properties required for an update message with a mailbox.
-	 * <p>
-	 * The required properties are {@link #PROP_KEY_ONION},
-	 * {@link #PROP_KEY_AUTHTOKEN}, {@link #PROP_KEY_INBOXID} and
-	 * {@link #PROP_KEY_OUTBOXID}.
 	 */
 	int PROP_COUNT = 4;
 
 	/**
-	 * The onion address of the mailbox, excluding the .onion suffix.
+	 * The required properties of an update message with a mailbox.
 	 */
 	String PROP_KEY_ONION = "onion";
-
-	/**
-	 * A bearer token for accessing the mailbox (64 hex digits).
-	 */
 	String PROP_KEY_AUTHTOKEN = "authToken";
-
-	/**
-	 * A folder ID for downloading messages (64 hex digits).
-	 */
 	String PROP_KEY_INBOXID = "inboxId";
-
-	/**
-	 * A folder ID for uploading messages (64 hex digits).
-	 */
 	String PROP_KEY_OUTBOXID = "outboxId";
 
 	/**
-	 * Length of the {@link #PROP_KEY_ONION} property.
+	 * Length of the Onion property.
 	 */
 	int PROP_ONION_LENGTH = 56;
 
@@ -79,32 +63,9 @@ public interface MailboxUpdateManager {
 	 */
 	String GROUP_KEY_SENT_CLIENT_SUPPORTS = "sentClientSupports";
 
-	/**
-	 * Key in the client's local group for storing the serverSupports list that
-	 * was last sent out, if any.
-	 */
-	String GROUP_KEY_SENT_SERVER_SUPPORTS = "sentServerSupports";
-
-	/**
-	 * Returns the latest {@link MailboxUpdate} sent to the given contact.
-	 * <p>
-	 * If we have our own mailbox then the update will be a
-	 * {@link MailboxUpdateWithMailbox} containing the
-	 * {@link MailboxProperties} the contact should use for communicating with
-	 * our mailbox.
-	 */
 	MailboxUpdate getLocalUpdate(Transaction txn, ContactId c)
 			throws DbException;
 
-	/**
-	 * Returns the latest {@link MailboxUpdate} received from the given
-	 * contact, or null if no update has been received.
-	 * <p>
-	 * If the contact has a mailbox then the update will be a
-	 * {@link MailboxUpdateWithMailbox} containing the
-	 * {@link MailboxProperties} we should use for communicating with the
-	 * contact's mailbox.
-	 */
 	@Nullable
 	MailboxUpdate getRemoteUpdate(Transaction txn, ContactId c)
 			throws DbException;

bramble-api/src/main/java/org/briarproject/bramble/api/mailbox/event/MailboxPairedEvent.java

@@ -1,36 +0,0 @@
-package org.briarproject.bramble.api.mailbox.event;
-
-import org.briarproject.bramble.api.contact.ContactId;
-import org.briarproject.bramble.api.event.Event;
-import org.briarproject.bramble.api.mailbox.MailboxProperties;
-import org.briarproject.bramble.api.mailbox.MailboxUpdateWithMailbox;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-
-import java.util.Map;
-
-import javax.annotation.concurrent.Immutable;
-
-/**
- * An event that is broadcast when a mailbox is paired.
- */
-@Immutable
-@NotNullByDefault
-public class MailboxPairedEvent extends Event {
-
-	private final MailboxProperties properties;
-	private final Map<ContactId, MailboxUpdateWithMailbox> localUpdates;
-
-	public MailboxPairedEvent(MailboxProperties properties,
-			Map<ContactId, MailboxUpdateWithMailbox> localUpdates) {
-		this.properties = properties;
-		this.localUpdates = localUpdates;
-	}
-
-	public MailboxProperties getProperties() {
-		return properties;
-	}
-
-	public Map<ContactId, MailboxUpdateWithMailbox> getLocalUpdates() {
-		return localUpdates;
-	}
-}

bramble-api/src/main/java/org/briarproject/bramble/api/mailbox/event/MailboxUnpairedEvent.java

@@ -1,28 +0,0 @@
-package org.briarproject.bramble.api.mailbox.event;
-
-import org.briarproject.bramble.api.contact.ContactId;
-import org.briarproject.bramble.api.event.Event;
-import org.briarproject.bramble.api.mailbox.MailboxUpdate;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-
-import java.util.Map;
-
-import javax.annotation.concurrent.Immutable;
-
-/**
- * An event that is broadcast when a mailbox is unpaired.
- */
-@Immutable
-@NotNullByDefault
-public class MailboxUnpairedEvent extends Event {
-
-	private final Map<ContactId, MailboxUpdate> localUpdates;
-
-	public MailboxUnpairedEvent(Map<ContactId, MailboxUpdate> localUpdates) {
-		this.localUpdates = localUpdates;
-	}
-
-	public Map<ContactId, MailboxUpdate> getLocalUpdates() {
-		return localUpdates;
-	}
-}

bramble-api/src/main/java/org/briarproject/bramble/api/mailbox/event/MailboxUpdateSentToNewContactEvent.java

@@ -1,40 +0,0 @@
-package org.briarproject.bramble.api.mailbox.event;
-
-import org.briarproject.bramble.api.contact.ContactId;
-import org.briarproject.bramble.api.event.Event;
-import org.briarproject.bramble.api.mailbox.MailboxUpdate;
-import org.briarproject.bramble.api.mailbox.MailboxUpdateManager;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-
-import javax.annotation.concurrent.Immutable;
-
-/**
- * An event that is broadcast when the first mailbox update is sent to a
- * newly added contact, which happens in the same transaction in which the
- * contact is added.
- * <p>
- * This event is not broadcast when the first mailbox update is sent to an
- * existing contact when setting up the
- * {@link MailboxUpdateManager mailbox update client}.
- */
-@Immutable
-@NotNullByDefault
-public class MailboxUpdateSentToNewContactEvent extends Event {
-
-	private final ContactId contactId;
-	private final MailboxUpdate mailboxUpdate;
-
-	public MailboxUpdateSentToNewContactEvent(ContactId contactId,
-			MailboxUpdate mailboxUpdate) {
-		this.contactId = contactId;
-		this.mailboxUpdate = mailboxUpdate;
-	}
-
-	public ContactId getContactId() {
-		return contactId;
-	}
-
-	public MailboxUpdate getMailboxUpdate() {
-		return mailboxUpdate;
-	}
-}

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

@@ -1,7 +1,9 @@
 package org.briarproject.bramble.api.plugin;
 
+import org.briarproject.bramble.api.event.EventBus;
+
 public interface BackoffFactory {
 
-	Backoff createBackoff(int minInterval, int maxInterval,
-			double base);
+	Backoff createBackoff(EventBus eventBus, TransportId transportId,
+			int minInterval, int maxInterval, double base);
 }

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

@@ -56,4 +56,9 @@ public interface PluginCallback extends ConnectionHandler {
 	 * This method can safely be called while holding a lock.
 	 */
 	void pluginStateChanged(State state);
+
+	/**
+	 * Informs the callback that the plugin's polling interval has decreased.
+	 */
+	void pollingIntervalDecreased();
 }

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/event/PollingIntervalDecreasedEvent.java

@@ -0,0 +1,25 @@
+package org.briarproject.bramble.api.plugin.event;
+
+import org.briarproject.bramble.api.event.Event;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.TransportId;
+
+import javax.annotation.concurrent.Immutable;
+
+/**
+ * An event that is broadcast when a plugin's polling interval decreases.
+ */
+@Immutable
+@NotNullByDefault
+public class PollingIntervalDecreasedEvent extends Event {
+
+	private final TransportId transportId;
+
+	public PollingIntervalDecreasedEvent(TransportId transportId) {
+		this.transportId = transportId;
+	}
+
+	public TransportId getTransportId() {
+		return transportId;
+	}
+}

bramble-api/src/main/java/org/briarproject/bramble/api/sync/DeferredSendHandler.java

@@ -0,0 +1,15 @@
+package org.briarproject.bramble.api.sync;
+
+import java.util.Collection;
+
+/**
+ * An interface for holding the IDs of messages sent and acked during an
+ * outgoing {@link SyncSession} so they can be recorded in the DB as sent
+ * or acked at some later time.
+ */
+public interface DeferredSendHandler {
+
+	void onAckSent(Collection<MessageId> acked);
+
+	void onMessageSent(MessageId sent);
+}

bramble-api/src/main/java/org/briarproject/bramble/api/sync/OutgoingSessionRecord.java

@@ -1,37 +0,0 @@
-package org.briarproject.bramble.api.sync;
-
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-
-import java.util.Collection;
-import java.util.concurrent.CopyOnWriteArrayList;
-
-import javax.annotation.concurrent.ThreadSafe;
-
-/**
- * A container for holding the IDs of messages sent and acked during an
- * outgoing {@link SyncSession}, so they can be recorded in the DB as sent
- * or acked at some later time.
- */
-@ThreadSafe
-@NotNullByDefault
-public class OutgoingSessionRecord {
-
-	private final Collection<MessageId> ackedIds = new CopyOnWriteArrayList<>();
-	private final Collection<MessageId> sentIds = new CopyOnWriteArrayList<>();
-
-	public void onAckSent(Collection<MessageId> acked) {
-		ackedIds.addAll(acked);
-	}
-
-	public void onMessageSent(MessageId sent) {
-		sentIds.add(sent);
-	}
-
-	public Collection<MessageId> getAckedIds() {
-		return ackedIds;
-	}
-
-	public Collection<MessageId> getSentIds() {
-		return sentIds;
-	}
-}

bramble-api/src/main/java/org/briarproject/bramble/api/sync/SyncSessionFactory.java

@@ -12,30 +12,12 @@ import javax.annotation.Nullable;
 @NotNullByDefault
 public interface SyncSessionFactory {
 
-	/**
-	 * Creates a session for receiving data from a contact.
-	 */
 	SyncSession createIncomingSession(ContactId c, InputStream in,
 			PriorityHandler handler);
 
-	/**
-	 * Creates a session for sending data to a contact over a simplex transport.
-	 *
-	 * @param eager True if messages should be sent eagerly, ie regardless of
-	 * whether they're due for retransmission.
-	 */
 	SyncSession createSimplexOutgoingSession(ContactId c, TransportId t,
 			long maxLatency, boolean eager, StreamWriter streamWriter);
 
-	/**
-	 * Creates a session for sending data to a contact via a mailbox. The IDs
-	 * of any messages sent or acked will be added to the given
-	 * {@link OutgoingSessionRecord}.
-	 */
-	SyncSession createSimplexOutgoingSession(ContactId c, TransportId t,
-			long maxLatency, StreamWriter streamWriter,
-			OutgoingSessionRecord sessionRecord);
-
 	SyncSession createDuplexOutgoingSession(ContactId c, TransportId t,
 			long maxLatency, int maxIdleTime, StreamWriter streamWriter,
 			@Nullable Priority priority);

bramble-api/src/main/java/org/briarproject/bramble/api/sync/event/GroupVisibilityUpdatedEvent.java

@@ -3,7 +3,6 @@ package org.briarproject.bramble.api.sync.event;
 import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.event.Event;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.sync.Group.Visibility;
 
 import java.util.Collection;
 
@@ -16,19 +15,12 @@ import javax.annotation.concurrent.Immutable;
 @NotNullByDefault
 public class GroupVisibilityUpdatedEvent extends Event {
 
-	private final Visibility visibility;
 	private final Collection<ContactId> affected;
 
-	public GroupVisibilityUpdatedEvent(Visibility visibility,
-			Collection<ContactId> affected) {
-		this.visibility = visibility;
+	public GroupVisibilityUpdatedEvent(Collection<ContactId> affected) {
 		this.affected = affected;
 	}
 
-	public Visibility getVisibility() {
-		return visibility;
-	}
-
 	/**
 	 * Returns the contacts affected by the update.
 	 */

bramble-api/src/main/java/org/briarproject/bramble/api/sync/event/MessageSharedEvent.java

@@ -1,14 +1,9 @@
 package org.briarproject.bramble.api.sync.event;
 
-import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.event.Event;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.sync.Group.Visibility;
-import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.MessageId;
 
-import java.util.Map;
-
 import javax.annotation.concurrent.Immutable;
 
 /**
@@ -19,32 +14,12 @@ import javax.annotation.concurrent.Immutable;
 public class MessageSharedEvent extends Event {
 
 	private final MessageId messageId;
-	private final GroupId groupId;
-	private final Map<ContactId, Boolean> groupVisibility;
 
-	public MessageSharedEvent(MessageId message, GroupId groupId,
-			Map<ContactId, Boolean> groupVisibility) {
+	public MessageSharedEvent(MessageId message) {
 		this.messageId = message;
-		this.groupId = groupId;
-		this.groupVisibility = groupVisibility;
 	}
 
 	public MessageId getMessageId() {
 		return messageId;
 	}
-
-	public GroupId getGroupId() {
-		return groupId;
-	}
-
-	/**
-	 * Returns the IDs of all contacts for which the visibility of the
-	 * message's group is either {@link Visibility#SHARED shared} or
-	 * {@link Visibility#VISIBLE visible}. The value in the map is true if the
-	 * group is {@link Visibility#SHARED shared} or false if the group is
-	 * {@link Visibility#VISIBLE visible}.
-	 */
-	public Map<ContactId, Boolean> getGroupVisibility() {
-		return groupVisibility;
-	}
 }

bramble-api/src/main/java/org/briarproject/bramble/util/IoUtils.java

@@ -40,7 +40,7 @@ public class IoUtils {
 		}
 	}
 
-	public static void delete(File f) {
+	private static void delete(File f) {
 		if (!f.delete() && LOG.isLoggable(WARNING))
 			LOG.warning("Could not delete " + f.getAbsolutePath());
 	}

bramble-api/src/main/java/org/briarproject/bramble/util/StringUtils.java

@@ -1,6 +1,5 @@
 package org.briarproject.bramble.util;
 
-import org.briarproject.bramble.api.FormatException;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 
 import java.io.UnsupportedEncodingException;
@@ -96,10 +95,10 @@ public class StringUtils {
 	/**
 	 * Converts the given hex string to a byte array.
 	 */
-	public static byte[] fromHexString(String hex) throws FormatException {
+	public static byte[] fromHexString(String hex) {
 		int len = hex.length();
 		if (len % 2 != 0)
-			throw new FormatException();
+			throw new IllegalArgumentException("Not a hex string");
 		byte[] bytes = new byte[len / 2];
 		for (int i = 0, j = 0; i < len; i += 2, j++) {
 			int high = hexDigitToInt(hex.charAt(i));
@@ -109,11 +108,11 @@ public class StringUtils {
 		return bytes;
 	}
 
-	private static int hexDigitToInt(char c) throws FormatException {
+	private static int hexDigitToInt(char c) {
 		if (c >= '0' && c <= '9') return c - '0';
 		if (c >= 'A' && c <= 'F') return c - 'A' + 10;
 		if (c >= 'a' && c <= 'f') return c - 'a' + 10;
-		throw new FormatException();
+		throw new IllegalArgumentException("Not a hex digit: " + c);
 	}
 
 	public static String trim(String s) {
@@ -131,13 +130,13 @@ public class StringUtils {
 		return MAC.matcher(mac).matches();
 	}
 
-	public static byte[] macToBytes(String mac) throws FormatException {
-		if (!MAC.matcher(mac).matches()) throw new FormatException();
+	public static byte[] macToBytes(String mac) {
+		if (!MAC.matcher(mac).matches()) throw new IllegalArgumentException();
 		return fromHexString(mac.replaceAll(":", ""));
 	}
 
-	public static String macToString(byte[] mac) throws FormatException {
-		if (mac.length != 6) throw new FormatException();
+	public static String macToString(byte[] mac) {
+		if (mac.length != 6) throw new IllegalArgumentException();
 		StringBuilder s = new StringBuilder();
 		for (byte b : mac) {
 			if (s.length() > 0) s.append(':');

bramble-api/src/test/java/org/briarproject/bramble/test/TestUtils.java

@@ -230,14 +230,14 @@ public class TestUtils {
 
 	public static MailboxProperties getMailboxProperties(boolean owner,
 			List<MailboxVersion> serverSupports) {
-		String onion = getRandomString(56);
+		String baseUrl = "http://" + getRandomString(56) + ".onion"; // TODO
 		MailboxAuthToken authToken = new MailboxAuthToken(getRandomId());
 		if (owner) {
-			return new MailboxProperties(onion, authToken, serverSupports);
+			return new MailboxProperties(baseUrl, authToken, serverSupports);
 		}
 		MailboxFolderId inboxId = new MailboxFolderId(getRandomId());
 		MailboxFolderId outboxId = new MailboxFolderId(getRandomId());
-		return new MailboxProperties(onion, authToken, serverSupports,
+		return new MailboxProperties(baseUrl, authToken, serverSupports,
 				inboxId, outboxId);
 	}
 
@@ -338,17 +338,6 @@ public class TestUtils {
 		return false;
 	}
 
-	public static <E extends Event> E getEvent(Transaction txn,
-			Class<E> eventClass) {
-		for (CommitAction action : txn.getActions()) {
-			if (action instanceof EventAction) {
-				Event event = ((EventAction) action).getEvent();
-				if (eventClass.isInstance(event)) return eventClass.cast(event);
-			}
-		}
-		throw new AssertionError();
-	}
-
 	public static boolean isCryptoStrengthUnlimited() {
 		try {
 			return Cipher.getMaxAllowedKeyLength("AES/CBC/PKCS5Padding")

bramble-core/build.gradle

@@ -16,7 +16,7 @@ dependencies {
 	implementation 'org.bitlet:weupnp:0.1.4'
 	implementation 'net.i2p.crypto:eddsa:0.2.0'
 	implementation 'org.whispersystems:curve25519-java:0.5.0'
-	implementation 'org.briarproject:jtorctl:0.5'
+	implementation 'org.briarproject:jtorctl:0.4'
 
 	//noinspection GradleDependency
 	implementation "com.squareup.okhttp3:okhttp:$okhttp_version"

bramble-core/src/main/java/org/briarproject/bramble/account/AccountManagerImpl.java

@@ -1,6 +1,5 @@
 package org.briarproject.bramble.account;
 
-import org.briarproject.bramble.api.FormatException;
 import org.briarproject.bramble.api.account.AccountManager;
 import org.briarproject.bramble.api.crypto.CryptoComponent;
 import org.briarproject.bramble.api.crypto.DecryptionException;
@@ -210,13 +209,7 @@ class AccountManagerImpl implements AccountManager {
 			LOG.warning("Failed to load encrypted database key");
 			throw new DecryptionException(INVALID_CIPHERTEXT);
 		}
-		byte[] ciphertext;
-		try {
-			ciphertext = fromHexString(hex);
-		} catch (FormatException e) {
-			LOG.warning("Encrypted database key has invalid format");
-			throw new DecryptionException(INVALID_CIPHERTEXT);
-		}
+		byte[] ciphertext = fromHexString(hex);
 		KeyStrengthener keyStrengthener = databaseConfig.getKeyStrengthener();
 		byte[] plaintext = crypto.decryptWithPassword(ciphertext, password,
 				keyStrengthener);

bramble-core/src/main/java/org/briarproject/bramble/client/ClientHelperImpl.java

@@ -52,7 +52,6 @@ import java.util.Map.Entry;
 import javax.annotation.concurrent.Immutable;
 import javax.inject.Inject;
 
-import static java.util.Collections.sort;
 import static org.briarproject.bramble.api.client.ContactGroupConstants.GROUP_KEY_CONTACT_ID;
 import static org.briarproject.bramble.api.identity.Author.FORMAT_VERSION;
 import static org.briarproject.bramble.api.identity.AuthorConstants.MAX_AUTHOR_NAME_LENGTH;
@@ -457,7 +456,8 @@ class ClientHelperImpl implements ClientHelper {
 		checkLength(inboxId, UniqueId.LENGTH);
 		byte[] outboxId = properties.getRaw(PROP_KEY_OUTBOXID);
 		checkLength(outboxId, UniqueId.LENGTH);
-		MailboxProperties props = new MailboxProperties(onion,
+		String baseUrl = "http://" + onion + ".onion"; // TODO
+		MailboxProperties props = new MailboxProperties(baseUrl,
 				new MailboxAuthToken(authToken), serverSupportsList,
 				new MailboxFolderId(inboxId), new MailboxFolderId(outboxId));
 		return new MailboxUpdateWithMailbox(clientSupportsList, props);
@@ -475,8 +475,6 @@ class ClientHelperImpl implements ClientHelper {
 			list.add(new MailboxVersion(element.getLong(0).intValue(),
 					element.getLong(1).intValue()));
 		}
-		// Sort the list of versions for easier comparison
-		sort(list);
 		return list;
 	}
 

bramble-core/src/main/java/org/briarproject/bramble/connection/ConnectionManagerImpl.java

@@ -13,7 +13,6 @@ import org.briarproject.bramble.api.plugin.TransportConnectionWriter;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
 import org.briarproject.bramble.api.properties.TransportPropertyManager;
-import org.briarproject.bramble.api.sync.OutgoingSessionRecord;
 import org.briarproject.bramble.api.sync.SyncSessionFactory;
 import org.briarproject.bramble.api.transport.KeyManager;
 import org.briarproject.bramble.api.transport.StreamReaderFactory;
@@ -101,16 +100,7 @@ class ConnectionManagerImpl implements ConnectionManager {
 			TransportConnectionWriter w) {
 		ioExecutor.execute(new OutgoingSimplexSyncConnection(keyManager,
 				connectionRegistry, streamReaderFactory, streamWriterFactory,
-				syncSessionFactory, transportPropertyManager, c, t, w, null));
-	}
-
-	@Override
-	public void manageOutgoingConnection(ContactId c, TransportId t,
-			TransportConnectionWriter w, OutgoingSessionRecord sessionRecord) {
-		ioExecutor.execute(new OutgoingSimplexSyncConnection(keyManager,
-				connectionRegistry, streamReaderFactory, streamWriterFactory,
-				syncSessionFactory, transportPropertyManager, c, t, w,
-				sessionRecord));
+				syncSessionFactory, transportPropertyManager, c, t, w));
 	}
 
 	@Override

bramble-core/src/main/java/org/briarproject/bramble/connection/OutgoingSimplexSyncConnection.java

@@ -6,7 +6,6 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.TransportConnectionWriter;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.properties.TransportPropertyManager;
-import org.briarproject.bramble.api.sync.OutgoingSessionRecord;
 import org.briarproject.bramble.api.sync.SyncSession;
 import org.briarproject.bramble.api.sync.SyncSessionFactory;
 import org.briarproject.bramble.api.transport.KeyManager;
@@ -17,8 +16,6 @@ import org.briarproject.bramble.api.transport.StreamWriterFactory;
 
 import java.io.IOException;
 
-import javax.annotation.Nullable;
-
 import static java.util.logging.Level.WARNING;
 import static org.briarproject.bramble.api.nullsafety.NullSafety.requireNonNull;
 import static org.briarproject.bramble.util.LogUtils.logException;
@@ -29,8 +26,6 @@ class OutgoingSimplexSyncConnection extends SyncConnection implements Runnable {
 	private final ContactId contactId;
 	private final TransportId transportId;
 	private final TransportConnectionWriter writer;
-	@Nullable
-	private final OutgoingSessionRecord sessionRecord;
 
 	OutgoingSimplexSyncConnection(KeyManager keyManager,
 			ConnectionRegistry connectionRegistry,
@@ -39,15 +34,13 @@ class OutgoingSimplexSyncConnection extends SyncConnection implements Runnable {
 			SyncSessionFactory syncSessionFactory,
 			TransportPropertyManager transportPropertyManager,
 			ContactId contactId, TransportId transportId,
-			TransportConnectionWriter writer,
-			@Nullable OutgoingSessionRecord sessionRecord) {
+			TransportConnectionWriter writer) {
 		super(keyManager, connectionRegistry, streamReaderFactory,
 				streamWriterFactory, syncSessionFactory,
 				transportPropertyManager);
 		this.contactId = contactId;
 		this.transportId = transportId;
 		this.writer = writer;
-		this.sessionRecord = sessionRecord;
 	}
 
 	@Override
@@ -78,16 +71,10 @@ class OutgoingSimplexSyncConnection extends SyncConnection implements Runnable {
 		StreamWriter streamWriter = streamWriterFactory.createStreamWriter(
 				w.getOutputStream(), ctx);
 		ContactId c = requireNonNull(ctx.getContactId());
-		if (sessionRecord == null) {
-			// Use eager retransmission if the transport is lossy and cheap
-			return syncSessionFactory.createSimplexOutgoingSession(c,
-					ctx.getTransportId(), w.getMaxLatency(),
-					w.isLossyAndCheap(), streamWriter);
-		} else {
-			return syncSessionFactory.createSimplexOutgoingSession(c,
-					ctx.getTransportId(), w.getMaxLatency(), streamWriter,
-					sessionRecord);
-		}
+		// Use eager retransmission if the transport is lossy and cheap
+		return syncSessionFactory.createSimplexOutgoingSession(c,
+				ctx.getTransportId(), w.getMaxLatency(), w.isLossyAndCheap(),
+				streamWriter);
 	}
 }
 

bramble-core/src/main/java/org/briarproject/bramble/db/Database.java

@@ -163,11 +163,16 @@ interface Database<T> {
 			throws DbException;
 
 	/**
-	 * Returns true if there are any acks to send to the given contact.
+	 * Returns true if there are any acks or messages to send to the given
+	 * contact over a transport with the given maximum latency.
 	 * <p/>
 	 * Read-only.
+	 *
+	 * @param eager True if messages that are not yet due for retransmission
+	 * should be included
 	 */
-	boolean containsAcksToSend(T txn, ContactId c) throws DbException;
+	boolean containsAnythingToSend(T txn, ContactId c, long maxLatency,
+			boolean eager) throws DbException;
 
 	/**
 	 * Returns true if the database contains the given contact for the given
@@ -207,18 +212,6 @@ interface Database<T> {
 	 */
 	boolean containsMessage(T txn, MessageId m) throws DbException;
 
-	/**
-	 * Returns true if there are any messages to send to the given
-	 * contact over a transport with the given maximum latency.
-	 * <p/>
-	 * Read-only.
-	 *
-	 * @param eager True if messages that are not yet due for retransmission
-	 * should be included
-	 */
-	boolean containsMessagesToSend(T txn, ContactId c, long maxLatency,
-			boolean eager) throws DbException;
-
 	/**
 	 * Returns true if the database contains the given pending contact.
 	 * <p/>
@@ -320,13 +313,6 @@ interface Database<T> {
 	 */
 	Group getGroup(T txn, GroupId g) throws DbException;
 
-	/**
-	 * Returns the ID of the group containing the given message.
-	 * <p/>
-	 * Read-only.
-	 */
-	GroupId getGroupId(T txn, MessageId m) throws DbException;
-
 	/**
 	 * Returns the metadata for the given group.
 	 * <p/>
@@ -352,11 +338,8 @@ interface Database<T> {
 			throws DbException;
 
 	/**
-	 * Returns the IDs of all contacts for which the given group's visibility
-	 * is either {@link Visibility#SHARED shared} or
-	 * {@link Visibility#VISIBLE visible}. The value in the map is true if the
-	 * group is {@link Visibility#SHARED shared} or false if the group is
-	 * {@link Visibility#VISIBLE visible}.
+	 * Returns the IDs of all contacts to which the given group's visibility is
+	 * either {@link Visibility VISIBLE} or {@link Visibility SHARED}.
 	 * <p/>
 	 * Read-only.
 	 */
@@ -597,16 +580,13 @@ interface Database<T> {
 
 	/**
 	 * Returns the next time (in milliseconds since the Unix epoch) when a
-	 * message is due to be sent to the given contact over a transport with
-	 * the given latency.
-	 * <p>
-	 * The returned value may be zero if a message is due to be sent
-	 * immediately, or Long.MAX_VALUE if no messages are scheduled to be sent.
+	 * message is due to be sent to the given contact. The returned value may
+	 * be zero if a message is due to be sent immediately, or Long.MAX_VALUE
+	 * if no messages are scheduled to be sent.
 	 * <p/>
 	 * Read-only.
 	 */
-	long getNextSendTime(T txn, ContactId c, long maxLatency)
-			throws DbException;
+	long getNextSendTime(T txn, ContactId c) throws DbException;
 
 	/**
 	 * Returns the pending contact with the given ID.

bramble-core/src/main/java/org/briarproject/bramble/db/DatabaseComponentImpl.java

@@ -287,12 +287,7 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 			transaction.attach(new MessageAddedEvent(m, null));
 			transaction.attach(new MessageStateChangedEvent(m.getId(), true,
 					DELIVERED));
-			if (shared) {
-				Map<ContactId, Boolean> visibility =
-						db.getGroupVisibility(txn, m.getGroupId());
-				transaction.attach(new MessageSharedEvent(m.getId(),
-						m.getGroupId(), visibility));
-			}
+			if (shared) transaction.attach(new MessageSharedEvent(m.getId()));
 		}
 		db.mergeMessageMetadata(txn, m.getId(), meta);
 	}
@@ -347,12 +342,12 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 	}
 
 	@Override
-	public boolean containsAcksToSend(Transaction transaction, ContactId c)
-			throws DbException {
+	public boolean containsAnythingToSend(Transaction transaction, ContactId c,
+			long maxLatency, boolean eager) throws DbException {
 		T txn = unbox(transaction);
 		if (!db.containsContact(txn, c))
 			throw new NoSuchContactException();
-		return db.containsAcksToSend(txn, c);
+		return db.containsAnythingToSend(txn, c, maxLatency, eager);
 	}
 
 	@Override
@@ -378,15 +373,6 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		return db.containsIdentity(txn, a);
 	}
 
-	@Override
-	public boolean containsMessagesToSend(Transaction transaction, ContactId c,
-			long maxLatency, boolean eager) throws DbException {
-		T txn = unbox(transaction);
-		if (!db.containsContact(txn, c))
-			throw new NoSuchContactException();
-		return db.containsMessagesToSend(txn, c, maxLatency, eager);
-	}
-
 	@Override
 	public boolean containsPendingContact(Transaction transaction,
 			PendingContactId p) throws DbException {
@@ -555,15 +541,6 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		return db.getGroup(txn, g);
 	}
 
-	@Override
-	public GroupId getGroupId(Transaction transaction, MessageId m)
-			throws DbException {
-		T txn = unbox(transaction);
-		if (!db.containsMessage(txn, m))
-			throw new NoSuchMessageException();
-		return db.getGroupId(txn, m);
-	}
-
 	@Override
 	public Metadata getGroupMetadata(Transaction transaction, GroupId g)
 			throws DbException {
@@ -634,11 +611,11 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 
 	@Override
 	public Collection<MessageId> getMessagesToAck(Transaction transaction,
-			ContactId c) throws DbException {
+			ContactId c, int maxMessages) throws DbException {
 		T txn = unbox(transaction);
 		if (!db.containsContact(txn, c))
 			throw new NoSuchContactException();
-		return db.getMessagesToAck(txn, c, Integer.MAX_VALUE);
+		return db.getMessagesToAck(txn, c, maxMessages);
 	}
 
 	@Override
@@ -760,9 +737,7 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 	public Message getMessageToSend(Transaction transaction, ContactId c,
 			MessageId m, long maxLatency, boolean markAsSent)
 			throws DbException {
-		if (markAsSent && transaction.isReadOnly()) {
-			throw new IllegalArgumentException();
-		}
+		if (transaction.isReadOnly()) throw new IllegalArgumentException();
 		T txn = unbox(transaction);
 		if (!db.containsContact(txn, c))
 			throw new NoSuchContactException();
@@ -830,10 +805,10 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 	}
 
 	@Override
-	public long getNextSendTime(Transaction transaction, ContactId c,
-			long maxLatency) throws DbException {
+	public long getNextSendTime(Transaction transaction, ContactId c)
+			throws DbException {
 		T txn = unbox(transaction);
-		return db.getNextSendTime(txn, c, maxLatency);
+		return db.getNextSendTime(txn, c);
 	}
 
 	@Override
@@ -1041,8 +1016,7 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 				db.getGroupVisibility(txn, id).keySet();
 		db.removeGroup(txn, id);
 		transaction.attach(new GroupRemovedEvent(g));
-		transaction.attach(new GroupVisibilityUpdatedEvent(INVISIBLE,
-				affected));
+		transaction.attach(new GroupVisibilityUpdatedEvent(affected));
 	}
 
 	@Override
@@ -1113,7 +1087,11 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		T txn = unbox(transaction);
 		if (!db.containsContact(txn, c))
 			throw new NoSuchContactException();
-		db.lowerAckFlag(txn, c, acked);
+		List<MessageId> visible = new ArrayList<>(acked.size());
+		for (MessageId m : acked) {
+			if (db.containsVisibleMessage(txn, c, m)) visible.add(m);
+		}
+		db.lowerAckFlag(txn, c, visible);
 	}
 
 	@Override
@@ -1163,7 +1141,7 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		else if (v == INVISIBLE) db.removeGroupVisibility(txn, c, g);
 		else db.setGroupVisibility(txn, c, g, v == SHARED);
 		List<ContactId> affected = singletonList(c);
-		transaction.attach(new GroupVisibilityUpdatedEvent(v, affected));
+		transaction.attach(new GroupVisibilityUpdatedEvent(affected));
 	}
 
 	@Override
@@ -1196,9 +1174,7 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		if (db.getMessageState(txn, m) != DELIVERED)
 			throw new IllegalArgumentException("Shared undelivered message");
 		db.setMessageShared(txn, m, true);
-		GroupId g = db.getGroupId(txn, m);
-		Map<ContactId, Boolean> visibility = db.getGroupVisibility(txn, g);
-		transaction.attach(new MessageSharedEvent(m, g, visibility));
+		transaction.attach(new MessageSharedEvent(m));
 	}
 
 	@Override

bramble-core/src/main/java/org/briarproject/bramble/db/JdbcDatabase.java

@@ -1147,8 +1147,8 @@ abstract class JdbcDatabase implements Database<Connection> {
 	}
 
 	@Override
-	public boolean containsAcksToSend(Connection txn, ContactId c)
-			throws DbException {
+	public boolean containsAnythingToSend(Connection txn, ContactId c,
+			long maxLatency, boolean eager) throws DbException {
 		PreparedStatement ps = null;
 		ResultSet rs = null;
 		try {
@@ -1160,7 +1160,34 @@ abstract class JdbcDatabase implements Database<Connection> {
 			boolean acksToSend = rs.next();
 			rs.close();
 			ps.close();
-			return acksToSend;
+			if (acksToSend) return true;
+			if (eager) {
+				sql = "SELECT NULL from statuses"
+						+ " WHERE contactId = ? AND state = ?"
+						+ " AND groupShared = TRUE AND messageShared = TRUE"
+						+ " AND deleted = FALSE AND seen = FALSE";
+				ps = txn.prepareStatement(sql);
+				ps.setInt(1, c.getInt());
+				ps.setInt(2, DELIVERED.getValue());
+			} else {
+				long now = clock.currentTimeMillis();
+				sql = "SELECT NULL FROM statuses"
+						+ " WHERE contactId = ? AND state = ?"
+						+ " AND groupShared = TRUE AND messageShared = TRUE"
+						+ " AND deleted = FALSE AND seen = FALSE"
+						+ " AND (expiry <= ? OR maxLatency IS NULL"
+						+ " OR ? < maxLatency)";
+				ps = txn.prepareStatement(sql);
+				ps.setInt(1, c.getInt());
+				ps.setInt(2, DELIVERED.getValue());
+				ps.setLong(3, now);
+				ps.setLong(4, maxLatency);
+			}
+			rs = ps.executeQuery();
+			boolean messagesToSend = rs.next();
+			rs.close();
+			ps.close();
+			return messagesToSend;
 		} catch (SQLException e) {
 			tryToClose(rs, LOG, WARNING);
 			tryToClose(ps, LOG, WARNING);
@@ -1280,46 +1307,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
-	@Override
-	public boolean containsMessagesToSend(Connection txn, ContactId c,
-			long maxLatency, boolean eager) throws DbException {
-		PreparedStatement ps = null;
-		ResultSet rs = null;
-		try {
-			if (eager) {
-				String sql = "SELECT NULL from statuses"
-						+ " WHERE contactId = ? AND state = ?"
-						+ " AND groupShared = TRUE AND messageShared = TRUE"
-						+ " AND deleted = FALSE AND seen = FALSE";
-				ps = txn.prepareStatement(sql);
-				ps.setInt(1, c.getInt());
-				ps.setInt(2, DELIVERED.getValue());
-			} else {
-				long now = clock.currentTimeMillis();
-				String sql = "SELECT NULL FROM statuses"
-						+ " WHERE contactId = ? AND state = ?"
-						+ " AND groupShared = TRUE AND messageShared = TRUE"
-						+ " AND deleted = FALSE AND seen = FALSE"
-						+ " AND (expiry <= ? OR maxLatency IS NULL"
-						+ " OR ? < maxLatency)";
-				ps = txn.prepareStatement(sql);
-				ps.setInt(1, c.getInt());
-				ps.setInt(2, DELIVERED.getValue());
-				ps.setLong(3, now);
-				ps.setLong(4, maxLatency);
-			}
-			rs = ps.executeQuery();
-			boolean messagesToSend = rs.next();
-			rs.close();
-			ps.close();
-			return messagesToSend;
-		} catch (SQLException e) {
-			tryToClose(rs, LOG, WARNING);
-			tryToClose(ps, LOG, WARNING);
-			throw new DbException(e);
-		}
-	}
-
 	@Override
 	public boolean containsPendingContact(Connection txn, PendingContactId p)
 			throws DbException {
@@ -1683,27 +1670,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
-	@Override
-	public GroupId getGroupId(Connection txn, MessageId m) throws DbException {
-		PreparedStatement ps = null;
-		ResultSet rs = null;
-		try {
-			String sql = "SELECT groupId FROM messages WHERE messageId = ?";
-			ps = txn.prepareStatement(sql);
-			ps.setBytes(1, m.getBytes());
-			rs = ps.executeQuery();
-			if (!rs.next()) throw new DbStateException();
-			GroupId g = new GroupId(rs.getBytes(1));
-			rs.close();
-			ps.close();
-			return g;
-		} catch (SQLException e) {
-			tryToClose(rs, LOG, WARNING);
-			tryToClose(ps, LOG, WARNING);
-			throw new DbException(e);
-		}
-	}
-
 	@Override
 	public Collection<Group> getGroups(Connection txn, ClientId c,
 			int majorVersion) throws DbException {
@@ -2511,28 +2477,12 @@ abstract class JdbcDatabase implements Database<Connection> {
 	}
 
 	@Override
-	public long getNextSendTime(Connection txn, ContactId c, long maxLatency)
+	public long getNextSendTime(Connection txn, ContactId c)
 			throws DbException {
 		PreparedStatement ps = null;
 		ResultSet rs = null;
 		try {
-			// Are any messages sendable immediately?
-			String sql = "SELECT NULL FROM statuses"
-					+ " WHERE contactId = ? AND state = ?"
-					+ " AND groupShared = TRUE AND messageShared = TRUE"
-					+ " AND deleted = FALSE AND seen = FALSE"
-					+ " AND (maxLatency IS NULL OR ? < maxLatency)";
-			ps = txn.prepareStatement(sql);
-			ps.setInt(1, c.getInt());
-			ps.setInt(2, DELIVERED.getValue());
-			ps.setLong(3, maxLatency);
-			rs = ps.executeQuery();
-			boolean found = rs.next();
-			rs.close();
-			ps.close();
-			if (found) return 0;
-			// When is the earliest expiry time (could be in the past)?
-			sql = "SELECT expiry FROM statuses"
+			String sql = "SELECT expiry FROM statuses"
 					+ " WHERE contactId = ? AND state = ?"
 					+ " AND groupShared = TRUE AND messageShared = TRUE"
 					+ " AND deleted = FALSE AND seen = FALSE"

bramble-core/src/main/java/org/briarproject/bramble/lifecycle/LifecycleManagerImpl.java

@@ -18,7 +18,7 @@ import java.util.List;
 import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.ExecutorService;
-import java.util.concurrent.atomic.AtomicReference;
+import java.util.concurrent.Semaphore;
 import java.util.logging.Logger;
 
 import javax.annotation.concurrent.ThreadSafe;
@@ -29,12 +29,10 @@ 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.lifecycle.LifecycleManager.LifecycleState.COMPACTING_DATABASE;
-import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState.CREATED;
 import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState.MIGRATING_DATABASE;
 import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState.RUNNING;
 import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState.STARTING;
 import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState.STARTING_SERVICES;
-import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState.STOPPED;
 import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState.STOPPING;
 import static org.briarproject.bramble.api.lifecycle.LifecycleManager.StartResult.ALREADY_RUNNING;
 import static org.briarproject.bramble.api.lifecycle.LifecycleManager.StartResult.CLOCK_ERROR;
@@ -62,11 +60,12 @@ class LifecycleManagerImpl implements LifecycleManager, MigrationListener {
 	private final List<Service> services;
 	private final List<OpenDatabaseHook> openDatabaseHooks;
 	private final List<ExecutorService> executors;
+	private final Semaphore startStopSemaphore = new Semaphore(1);
 	private final CountDownLatch dbLatch = new CountDownLatch(1);
 	private final CountDownLatch startupLatch = new CountDownLatch(1);
 	private final CountDownLatch shutdownLatch = new CountDownLatch(1);
-	private final AtomicReference<LifecycleState> state =
-			new AtomicReference<>(CREATED);
+
+	private volatile LifecycleState state = STARTING;
 
 	@Inject
 	LifecycleManagerImpl(DatabaseComponent db, EventBus eventBus,
@@ -103,8 +102,8 @@ class LifecycleManagerImpl implements LifecycleManager, MigrationListener {
 
 	@Override
 	public StartResult startServices(SecretKey dbKey) {
-		if (!state.compareAndSet(CREATED, STARTING)) {
-			LOG.warning("Already running");
+		if (!startStopSemaphore.tryAcquire()) {
+			LOG.info("Already starting or stopping");
 			return ALREADY_RUNNING;
 		}
 		long now = clock.currentTimeMillis();
@@ -136,7 +135,7 @@ class LifecycleManagerImpl implements LifecycleManager, MigrationListener {
 			});
 
 			LOG.info("Starting services");
-			state.set(STARTING_SERVICES);
+			state = STARTING_SERVICES;
 			dbLatch.countDown();
 			eventBus.broadcast(new LifecycleEvent(STARTING_SERVICES));
 
@@ -149,7 +148,7 @@ class LifecycleManagerImpl implements LifecycleManager, MigrationListener {
 				}
 			}
 
-			state.set(RUNNING);
+			state = RUNNING;
 			startupLatch.countDown();
 			eventBus.broadcast(new LifecycleEvent(RUNNING));
 			return SUCCESS;
@@ -165,58 +164,63 @@ class LifecycleManagerImpl implements LifecycleManager, MigrationListener {
 		} catch (ServiceException e) {
 			logException(LOG, WARNING, e);
 			return SERVICE_ERROR;
+		} finally {
+			startStopSemaphore.release();
 		}
 	}
 
 	@Override
 	public void onDatabaseMigration() {
-		state.set(MIGRATING_DATABASE);
+		state = MIGRATING_DATABASE;
 		eventBus.broadcast(new LifecycleEvent(MIGRATING_DATABASE));
 	}
 
 	@Override
 	public void onDatabaseCompaction() {
-		state.set(COMPACTING_DATABASE);
+		state = COMPACTING_DATABASE;
 		eventBus.broadcast(new LifecycleEvent(COMPACTING_DATABASE));
 	}
 
 	@Override
 	public void stopServices() {
-		if (!state.compareAndSet(RUNNING, STOPPING)) {
-			LOG.warning("Not running");
+		try {
+			startStopSemaphore.acquire();
+		} catch (InterruptedException e) {
+			LOG.warning("Interrupted while waiting to stop services");
 			return;
 		}
-		LOG.info("Stopping services");
-		eventBus.broadcast(new LifecycleEvent(STOPPING));
-		for (Service s : services) {
-			try {
+		try {
+			if (state == STOPPING) {
+				LOG.info("Already stopped");
+				return;
+			}
+			LOG.info("Stopping services");
+			state = STOPPING;
+			eventBus.broadcast(new LifecycleEvent(STOPPING));
+			for (Service s : services) {
 				long start = now();
 				s.stopService();
 				if (LOG.isLoggable(FINE)) {
 					logDuration(LOG, "Stopping service "
 							+ s.getClass().getSimpleName(), start);
 				}
-			} catch (ServiceException e) {
-				logException(LOG, WARNING, e);
 			}
-		}
-		for (ExecutorService e : executors) {
-			if (LOG.isLoggable(FINE)) {
-				LOG.fine("Stopping executor "
-						+ e.getClass().getSimpleName());
+			for (ExecutorService e : executors) {
+				if (LOG.isLoggable(FINE)) {
+					LOG.fine("Stopping executor "
+							+ e.getClass().getSimpleName());
+				}
+				e.shutdownNow();
 			}
-			e.shutdownNow();
-		}
-		try {
 			long start = now();
 			db.close();
 			logDuration(LOG, "Closing database", start);
-		} catch (DbException e) {
+			shutdownLatch.countDown();
+		} catch (DbException | ServiceException e) {
 			logException(LOG, WARNING, e);
+		} finally {
+			startStopSemaphore.release();
 		}
-		state.set(STOPPED);
-		shutdownLatch.countDown();
-		eventBus.broadcast(new LifecycleEvent(STOPPED));
 	}
 
 	@Override
@@ -236,6 +240,6 @@ class LifecycleManagerImpl implements LifecycleManager, MigrationListener {
 
 	@Override
 	public LifecycleState getLifecycleState() {
-		return state.get();
+		return state;
 	}
 }

bramble-core/src/main/java/org/briarproject/bramble/mailbox/ContactMailboxClient.java

@@ -1,124 +0,0 @@
-package org.briarproject.bramble.mailbox;
-
-import org.briarproject.bramble.api.contact.ContactId;
-import org.briarproject.bramble.api.mailbox.MailboxFolderId;
-import org.briarproject.bramble.api.mailbox.MailboxProperties;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-
-import java.util.logging.Logger;
-
-import javax.annotation.Nullable;
-import javax.annotation.concurrent.GuardedBy;
-import javax.annotation.concurrent.ThreadSafe;
-
-import static java.util.logging.Logger.getLogger;
-
-@ThreadSafe
-@NotNullByDefault
-class ContactMailboxClient implements MailboxClient {
-
-	private static final Logger LOG =
-			getLogger(ContactMailboxClient.class.getName());
-
-	private final MailboxWorkerFactory workerFactory;
-	private final ConnectivityChecker connectivityChecker;
-	private final TorReachabilityMonitor reachabilityMonitor;
-	private final Object lock = new Object();
-
-	@GuardedBy("lock")
-	@Nullable
-	private MailboxWorker uploadWorker = null, downloadWorker = null;
-
-	ContactMailboxClient(MailboxWorkerFactory workerFactory,
-			ConnectivityChecker connectivityChecker,
-			TorReachabilityMonitor reachabilityMonitor) {
-		this.workerFactory = workerFactory;
-		this.connectivityChecker = connectivityChecker;
-		this.reachabilityMonitor = reachabilityMonitor;
-	}
-
-	@Override
-	public void start() {
-		LOG.info("Started");
-		// Nothing to do until contact is assigned
-	}
-
-	@Override
-	public void destroy() {
-		LOG.info("Destroyed");
-		MailboxWorker uploadWorker, downloadWorker;
-		synchronized (lock) {
-			uploadWorker = this.uploadWorker;
-			this.uploadWorker = null;
-			downloadWorker = this.downloadWorker;
-			this.downloadWorker = null;
-		}
-		if (uploadWorker != null) uploadWorker.destroy();
-		if (downloadWorker != null) downloadWorker.destroy();
-		// The connectivity checker belongs to the client, so it should be
-		// destroyed. The Tor reachability monitor is shared between clients,
-		// so it should not be destroyed
-		connectivityChecker.destroy();
-	}
-
-	@Override
-	public void assignContactForUpload(ContactId contactId,
-			MailboxProperties properties, MailboxFolderId folderId) {
-		LOG.info("Contact assigned for upload");
-		if (properties.isOwner()) throw new IllegalArgumentException();
-		// For a contact's mailbox we should always be uploading to the outbox
-		// assigned to us by the contact
-		if (!folderId.equals(properties.getOutboxId())) {
-			throw new IllegalArgumentException();
-		}
-		MailboxWorker uploadWorker = workerFactory.createUploadWorker(
-				connectivityChecker, properties, folderId, contactId);
-		synchronized (lock) {
-			if (this.uploadWorker != null) throw new IllegalStateException();
-			this.uploadWorker = uploadWorker;
-		}
-		uploadWorker.start();
-	}
-
-	@Override
-	public void deassignContactForUpload(ContactId contactId) {
-		LOG.info("Contact deassigned for upload");
-		MailboxWorker uploadWorker;
-		synchronized (lock) {
-			uploadWorker = this.uploadWorker;
-			this.uploadWorker = null;
-		}
-		if (uploadWorker != null) uploadWorker.destroy();
-	}
-
-	@Override
-	public void assignContactForDownload(ContactId contactId,
-			MailboxProperties properties, MailboxFolderId folderId) {
-		LOG.info("Contact assigned for download");
-		if (properties.isOwner()) throw new IllegalArgumentException();
-		// For a contact's mailbox we should always be downloading from the
-		// inbox assigned to us by the contact
-		if (!folderId.equals(properties.getInboxId())) {
-			throw new IllegalArgumentException();
-		}
-		MailboxWorker downloadWorker =
-				workerFactory.createDownloadWorkerForContactMailbox(
-						connectivityChecker, reachabilityMonitor, properties);
-		synchronized (lock) {
-			if (this.downloadWorker != null) throw new IllegalStateException();
-			this.downloadWorker = downloadWorker;
-		}
-		downloadWorker.start();
-	}
-
-	@Override
-	public void deassignContactForDownload(ContactId contactId) {
-		LOG.info("Contact deassigned for download");
-		MailboxWorker downloadWorker;
-		synchronized (lock) {
-			downloadWorker = this.downloadWorker;
-			this.downloadWorker = null;
-		}
-		if (downloadWorker != null) downloadWorker.destroy();
-	}
-}

bramble-core/src/main/java/org/briarproject/bramble/mailbox/ContactMailboxConnectivityChecker.java

@@ -5,23 +5,14 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.mailbox.MailboxApi.ApiException;
 
-import java.util.logging.Logger;
-
 import javax.annotation.concurrent.ThreadSafe;
-import javax.inject.Inject;
-
-import static java.util.logging.Logger.getLogger;
 
 @ThreadSafe
 @NotNullByDefault
 class ContactMailboxConnectivityChecker extends ConnectivityCheckerImpl {
 
-	private static final Logger LOG =
-			getLogger(ContactMailboxConnectivityChecker.class.getName());
-
 	private final MailboxApi mailboxApi;
 
-	@Inject
 	ContactMailboxConnectivityChecker(Clock clock,
 			MailboxApiCaller mailboxApiCaller, MailboxApi mailboxApi) {
 		super(clock, mailboxApiCaller);
@@ -32,9 +23,7 @@ class ContactMailboxConnectivityChecker extends ConnectivityCheckerImpl {
 	ApiCall createConnectivityCheckTask(MailboxProperties properties) {
 		if (properties.isOwner()) throw new IllegalArgumentException();
 		return new SimpleApiCall(() -> {
-			LOG.info("Checking connectivity of contact's mailbox");
 			if (!mailboxApi.checkStatus(properties)) throw new ApiException();
-			LOG.info("Contact's mailbox is reachable");
 			// Call the observers and cache the result
 			onConnectivityCheckSucceeded(clock.currentTimeMillis());
 		});

bramble-core/src/main/java/org/briarproject/bramble/mailbox/ContactMailboxDownloadWorker.java

@@ -1,25 +1,73 @@
 package org.briarproject.bramble.mailbox;
 
-import org.briarproject.bramble.api.mailbox.MailboxFolderId;
+import org.briarproject.bramble.api.Cancellable;
 import org.briarproject.bramble.api.mailbox.MailboxProperties;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.mailbox.ConnectivityChecker.ConnectivityObserver;
 import org.briarproject.bramble.mailbox.MailboxApi.ApiException;
 import org.briarproject.bramble.mailbox.MailboxApi.MailboxFile;
 import org.briarproject.bramble.mailbox.MailboxApi.TolerableFailureException;
+import org.briarproject.bramble.mailbox.TorReachabilityMonitor.TorReachabilityObserver;
 
+import java.io.File;
 import java.io.IOException;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Queue;
+import java.util.logging.Logger;
 
+import javax.annotation.Nullable;
+import javax.annotation.concurrent.GuardedBy;
 import javax.annotation.concurrent.ThreadSafe;
 
-import static java.util.Collections.emptyList;
+import static java.util.logging.Level.INFO;
+import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.api.nullsafety.NullSafety.requireNonNull;
+import static org.briarproject.bramble.util.LogUtils.logException;
 
 @ThreadSafe
 @NotNullByDefault
-class ContactMailboxDownloadWorker extends MailboxDownloadWorker {
+class ContactMailboxDownloadWorker implements MailboxWorker,
+		ConnectivityObserver, TorReachabilityObserver {
+
+	/**
+	 * When the worker is started it waits for a connectivity check, then
+	 * starts its first download cycle: checking the inbox, downloading and
+	 * deleting any files, and checking again until the inbox is empty.
+	 * <p>
+	 * The worker then waits for our Tor hidden service to be reachable before
+	 * starting its second download cycle. This ensures that if a contact
+	 * tried and failed to connect to our hidden service before it was
+	 * reachable, and therefore uploaded a file to the mailbox instead, we'll
+	 * find the file in the second download cycle.
+	 */
+	private enum State {
+		CREATED,
+		CONNECTIVITY_CHECK,
+		DOWNLOAD_CYCLE_1,
+		WAITING_FOR_TOR,
+		DOWNLOAD_CYCLE_2,
+		FINISHED,
+		DESTROYED
+	}
+
+	private static final Logger LOG =
+			getLogger(ContactMailboxDownloadWorker.class.getName());
+
+	private final ConnectivityChecker connectivityChecker;
+	private final TorReachabilityMonitor torReachabilityMonitor;
+	private final MailboxApiCaller mailboxApiCaller;
+	private final MailboxApi mailboxApi;
+	private final MailboxFileManager mailboxFileManager;
+	private final MailboxProperties mailboxProperties;
+	private final Object lock = new Object();
+
+	@GuardedBy("lock")
+	private State state = State.CREATED;
+
+	@GuardedBy("lock")
+	@Nullable
+	private Cancellable apiCall = null;
 
 	ContactMailboxDownloadWorker(
 			ConnectivityChecker connectivityChecker,
@@ -28,14 +76,57 @@ class ContactMailboxDownloadWorker extends MailboxDownloadWorker {
 			MailboxApi mailboxApi,
 			MailboxFileManager mailboxFileManager,
 			MailboxProperties mailboxProperties) {
-		super(connectivityChecker, torReachabilityMonitor, mailboxApiCaller,
-				mailboxApi, mailboxFileManager, mailboxProperties);
 		if (mailboxProperties.isOwner()) throw new IllegalArgumentException();
+		this.connectivityChecker = connectivityChecker;
+		this.torReachabilityMonitor = torReachabilityMonitor;
+		this.mailboxApiCaller = mailboxApiCaller;
+		this.mailboxApi = mailboxApi;
+		this.mailboxFileManager = mailboxFileManager;
+		this.mailboxProperties = mailboxProperties;
 	}
 
 	@Override
-	protected ApiCall createApiCallForDownloadCycle() {
-		return new SimpleApiCall(this::apiCallListInbox);
+	public void start() {
+		LOG.info("Started");
+		synchronized (lock) {
+			// Don't allow the worker to be reused
+			if (state != State.CREATED) throw new IllegalStateException();
+			state = State.CONNECTIVITY_CHECK;
+		}
+		// Avoid leaking observer in case destroy() is called concurrently
+		// before observer is added
+		connectivityChecker.checkConnectivity(mailboxProperties, this);
+		boolean destroyed;
+		synchronized (lock) {
+			destroyed = state == State.DESTROYED;
+		}
+		if (destroyed) connectivityChecker.removeObserver(this);
+	}
+
+	@Override
+	public void destroy() {
+		LOG.info("Destroyed");
+		Cancellable apiCall;
+		synchronized (lock) {
+			state = State.DESTROYED;
+			apiCall = this.apiCall;
+			this.apiCall = null;
+		}
+		if (apiCall != null) apiCall.cancel();
+		connectivityChecker.removeObserver(this);
+		torReachabilityMonitor.removeObserver(this);
+	}
+
+	@Override
+	public void onConnectivityCheckSucceeded() {
+		LOG.info("Connectivity check succeeded");
+		synchronized (lock) {
+			if (state != State.CONNECTIVITY_CHECK) return;
+			state = State.DOWNLOAD_CYCLE_1;
+			// Start first download cycle
+			apiCall = mailboxApiCaller.retryWithBackoff(
+					new SimpleApiCall(this::apiCallListInbox));
+		}
 	}
 
 	private void apiCallListInbox() throws IOException, ApiException {
@@ -43,23 +134,108 @@ class ContactMailboxDownloadWorker extends MailboxDownloadWorker {
 			if (state == State.DESTROYED) return;
 		}
 		LOG.info("Listing inbox");
-		MailboxFolderId folderId =
-				requireNonNull(mailboxProperties.getInboxId());
-		List<MailboxFile> files;
-		try {
-			files = mailboxApi.getFiles(mailboxProperties, folderId);
-		} catch (TolerableFailureException e) {
-			LOG.warning("Inbox folder does not exist");
-			files = emptyList();
-		}
-		if (files.isEmpty()) {
-			onDownloadCycleFinished();
-		} else {
-			Queue<FolderFile> queue = new LinkedList<>();
-			for (MailboxFile file : files) {
-				queue.add(new FolderFile(folderId, file.name));
+		List<MailboxFile> files = mailboxApi.getFiles(mailboxProperties,
+				requireNonNull(mailboxProperties.getInboxId()));
+		if (files.isEmpty()) onDownloadCycleFinished();
+		else downloadNextFile(new LinkedList<>(files));
+	}
+
+	private void onDownloadCycleFinished() {
+		boolean addObserver = false;
+		synchronized (lock) {
+			if (state == State.DOWNLOAD_CYCLE_1) {
+				LOG.info("First download cycle finished");
+				state = State.WAITING_FOR_TOR;
+				addObserver = true;
+			} else if (state == State.DOWNLOAD_CYCLE_2) {
+				LOG.info("Second download cycle finished");
+				state = State.FINISHED;
 			}
+		}
+		if (addObserver) {
+			// Avoid leaking observer in case destroy() is called concurrently
+			// before observer is added
+			torReachabilityMonitor.addOneShotObserver(this);
+			boolean destroyed;
+			synchronized (lock) {
+				destroyed = state == State.DESTROYED;
+			}
+			if (destroyed) torReachabilityMonitor.removeObserver(this);
+		}
+	}
+
+	private void downloadNextFile(Queue<MailboxFile> queue) {
+		synchronized (lock) {
+			if (state == State.DESTROYED) return;
+			MailboxFile file = queue.remove();
+			apiCall = mailboxApiCaller.retryWithBackoff(
+					new SimpleApiCall(() -> apiCallDownloadFile(file, queue)));
+		}
+	}
+
+	private void apiCallDownloadFile(MailboxFile file,
+			Queue<MailboxFile> queue) throws IOException, ApiException {
+		synchronized (lock) {
+			if (state == State.DESTROYED) return;
+		}
+		LOG.info("Downloading file");
+		File tempFile = mailboxFileManager.createTempFileForDownload();
+		try {
+			mailboxApi.getFile(mailboxProperties,
+					requireNonNull(mailboxProperties.getInboxId()),
+					file.name, tempFile);
+		} catch (IOException | ApiException e) {
+			if (!tempFile.delete()) {
+				LOG.warning("Failed to delete temporary file");
+			}
+			throw e;
+		}
+		mailboxFileManager.handleDownloadedFile(tempFile);
+		deleteFile(file, queue);
+	}
+
+	private void deleteFile(MailboxFile file, Queue<MailboxFile> queue) {
+		synchronized (lock) {
+			if (state == State.DESTROYED) return;
+			apiCall = mailboxApiCaller.retryWithBackoff(
+					new SimpleApiCall(() -> apiCallDeleteFile(file, queue)));
+		}
+	}
+
+	private void apiCallDeleteFile(MailboxFile file, Queue<MailboxFile> queue)
+			throws IOException, ApiException {
+		synchronized (lock) {
+			if (state == State.DESTROYED) return;
+		}
+		try {
+			mailboxApi.deleteFile(mailboxProperties,
+					requireNonNull(mailboxProperties.getInboxId()), file.name);
+		} catch (TolerableFailureException e) {
+			// Catch this so we can continue to the next file
+			logException(LOG, INFO, e);
+		}
+		if (queue.isEmpty()) {
+			// List the inbox again to check for files that may have arrived
+			// while we were downloading
+			synchronized (lock) {
+				if (state == State.DESTROYED) return;
+				apiCall = mailboxApiCaller.retryWithBackoff(
+						new SimpleApiCall(this::apiCallListInbox));
+			}
+		} else {
 			downloadNextFile(queue);
 		}
 	}
+
+	@Override
+	public void onTorReachable() {
+		LOG.info("Our Tor hidden service is reachable");
+		synchronized (lock) {
+			if (state != State.WAITING_FOR_TOR) return;
+			state = State.DOWNLOAD_CYCLE_2;
+			// Start second download cycle
+			apiCall = mailboxApiCaller.retryWithBackoff(
+					new SimpleApiCall(this::apiCallListInbox));
+		}
+	}
 }

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxApi.java

@@ -91,13 +91,9 @@ interface MailboxApi {
 	 * Used by owner and contacts to list their files to retrieve.
 	 * <p>
 	 * Returns 200 OK with the list of files in JSON.
-	 *
-	 * @throws TolerableFailureException if response code is 404 (folder does
-	 * not exist or client is not authorised to download from it)
 	 */
 	List<MailboxFile> getFiles(MailboxProperties properties,
-			MailboxFolderId folderId)
-			throws IOException, ApiException, TolerableFailureException;
+			MailboxFolderId folderId) throws IOException, ApiException;
 
 	/**
 	 * Used by owner and contacts to retrieve a file.
@@ -106,22 +102,17 @@ interface MailboxApi {
 	 * in the response body.
 	 *
 	 * @param file the empty file the response bytes will be written into.
-	 * @throws TolerableFailureException if response code is 404 (folder does
-	 * not exist, client is not authorised to download from folder, or file
-	 * does not exist)
 	 */
 	void getFile(MailboxProperties properties, MailboxFolderId folderId,
-			MailboxFileId fileId, File file)
-			throws IOException, ApiException, TolerableFailureException;
+			MailboxFileId fileId, File file) throws IOException, ApiException;
 
 	/**
 	 * Used by owner and contacts to delete files.
 	 * <p>
 	 * Returns 200 OK (no exception) if deletion was successful.
 	 *
-	 * @throws TolerableFailureException if response code is 404 (folder does
-	 * not exist, client is not authorised to download from folder, or file
-	 * does not exist)
+	 * @throws TolerableFailureException on 404 response,
+	 * because file was most likely deleted already.
 	 */
 	void deleteFile(MailboxProperties properties, MailboxFolderId folderId,
 			MailboxFileId fileId)

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxApiImpl.java

@@ -22,6 +22,7 @@ import java.io.FileOutputStream;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.List;
 
 import javax.inject.Inject;
@@ -34,7 +35,6 @@ import okhttp3.Response;
 import okhttp3.ResponseBody;
 
 import static com.fasterxml.jackson.databind.MapperFeature.BLOCK_UNSAFE_POLYMORPHIC_BASE_TYPES;
-import static java.util.Collections.sort;
 import static java.util.Objects.requireNonNull;
 import static okhttp3.internal.Util.EMPTY_REQUEST;
 import static org.briarproject.bramble.util.IoUtils.copyAndClose;
@@ -42,22 +42,18 @@ import static org.briarproject.bramble.util.IoUtils.copyAndClose;
 @NotNullByDefault
 class MailboxApiImpl implements MailboxApi {
 
+	private final WeakSingletonProvider<OkHttpClient> httpClientProvider;
+	private final JsonMapper mapper = JsonMapper.builder()
+			.enable(BLOCK_UNSAFE_POLYMORPHIC_BASE_TYPES)
+			.build();
 	private static final MediaType JSON =
 			requireNonNull(MediaType.parse("application/json; charset=utf-8"));
 	private static final MediaType FILE =
 			requireNonNull(MediaType.parse("application/octet-stream"));
 
-	private final WeakSingletonProvider<OkHttpClient> httpClientProvider;
-	private final JsonMapper mapper = JsonMapper.builder()
-			.enable(BLOCK_UNSAFE_POLYMORPHIC_BASE_TYPES)
-			.build();
-	private final UrlConverter urlConverter;
-
 	@Inject
-	MailboxApiImpl(WeakSingletonProvider<OkHttpClient> httpClientProvider,
-			UrlConverter urlConverter) {
+	MailboxApiImpl(WeakSingletonProvider<OkHttpClient> httpClientProvider) {
 		this.httpClientProvider = httpClientProvider;
-		this.urlConverter = urlConverter;
 	}
 
 	@Override
@@ -82,7 +78,7 @@ class MailboxApiImpl implements MailboxApi {
 			throws IOException, ApiException {
 		if (!properties.isOwner()) throw new IllegalArgumentException();
 		Request request = getRequestBuilder(properties.getAuthToken())
-				.url(getBaseUrl(properties) + "/setup")
+				.url(properties.getBaseUrl() + "/setup")
 				.put(EMPTY_REQUEST)
 				.build();
 		OkHttpClient client = httpClientProvider.get();
@@ -97,7 +93,7 @@ class MailboxApiImpl implements MailboxApi {
 			if (tokenNode == null) {
 				throw new ApiException();
 			}
-			return new MailboxProperties(properties.getOnion(),
+			return new MailboxProperties(properties.getBaseUrl(),
 					MailboxAuthToken.fromString(tokenNode.textValue()),
 					parseServerSupports(node));
 		} catch (JacksonException | InvalidMailboxIdException e) {
@@ -125,8 +121,6 @@ class MailboxApiImpl implements MailboxApi {
 			if (major < 0 || minor < 0) throw new ApiException();
 			serverSupports.add(new MailboxVersion(major, minor));
 		}
-		// Sort the list of versions for easier comparison
-		sort(serverSupports);
 		return serverSupports;
 	}
 
@@ -143,7 +137,7 @@ class MailboxApiImpl implements MailboxApi {
 			throws IOException, ApiException {
 		if (!properties.isOwner()) throw new IllegalArgumentException();
 		Request request = getRequestBuilder(properties.getAuthToken())
-				.url(getBaseUrl(properties) + "/")
+				.url(properties.getBaseUrl() + "/")
 				.delete()
 				.build();
 		OkHttpClient client = httpClientProvider.get();
@@ -168,7 +162,7 @@ class MailboxApiImpl implements MailboxApi {
 	public void deleteContact(MailboxProperties properties, ContactId contactId)
 			throws IOException, ApiException, TolerableFailureException {
 		if (!properties.isOwner()) throw new IllegalArgumentException();
-		String url = getBaseUrl(properties) + "/contacts/" +
+		String url = properties.getBaseUrl() + "/contacts/" +
 				contactId.getInt();
 		Request request = getRequestBuilder(properties.getAuthToken())
 				.delete()
@@ -218,11 +212,9 @@ class MailboxApiImpl implements MailboxApi {
 
 	@Override
 	public List<MailboxFile> getFiles(MailboxProperties properties,
-			MailboxFolderId folderId)
-			throws IOException, ApiException, TolerableFailureException {
+			MailboxFolderId folderId) throws IOException, ApiException {
 		String path = "/files/" + folderId;
 		Response response = sendGetRequest(properties, path);
-		if (response.code() == 404) throw new TolerableFailureException();
 		if (response.code() != 200) throw new ApiException();
 
 		ResponseBody body = response.body();
@@ -247,7 +239,7 @@ class MailboxApiImpl implements MailboxApi {
 				if (time < 1) throw new ApiException();
 				list.add(new MailboxFile(MailboxFileId.fromString(name), time));
 			}
-			sort(list);
+			Collections.sort(list);
 			return list;
 		} catch (JacksonException | InvalidMailboxIdException e) {
 			throw new ApiException();
@@ -256,11 +248,9 @@ class MailboxApiImpl implements MailboxApi {
 
 	@Override
 	public void getFile(MailboxProperties properties, MailboxFolderId folderId,
-			MailboxFileId fileId, File file)
-			throws IOException, ApiException, TolerableFailureException {
+			MailboxFileId fileId, File file) throws IOException, ApiException {
 		String path = "/files/" + folderId + "/" + fileId;
 		Response response = sendGetRequest(properties, path);
-		if (response.code() == 404) throw new TolerableFailureException();
 		if (response.code() != 200) throw new ApiException();
 
 		ResponseBody body = response.body();
@@ -276,7 +266,7 @@ class MailboxApiImpl implements MailboxApi {
 		String path = "/files/" + folderId + "/" + fileId;
 		Request request = getRequestBuilder(properties.getAuthToken())
 				.delete()
-				.url(getBaseUrl(properties) + path)
+				.url(properties.getBaseUrl() + path)
 				.build();
 		OkHttpClient client = httpClientProvider.get();
 		Response response = client.newCall(request).execute();
@@ -318,7 +308,7 @@ class MailboxApiImpl implements MailboxApi {
 	private Response sendGetRequest(MailboxProperties properties, String path)
 			throws IOException {
 		Request request = getRequestBuilder(properties.getAuthToken())
-				.url(getBaseUrl(properties) + path)
+				.url(properties.getBaseUrl() + path)
 				.build();
 		OkHttpClient client = httpClientProvider.get();
 		return client.newCall(request).execute();
@@ -327,7 +317,7 @@ class MailboxApiImpl implements MailboxApi {
 	private Response sendPostRequest(MailboxProperties properties, String path,
 			RequestBody body) throws IOException {
 		Request request = getRequestBuilder(properties.getAuthToken())
-				.url(getBaseUrl(properties) + path)
+				.url(properties.getBaseUrl() + path)
 				.post(body)
 				.build();
 		OkHttpClient client = httpClientProvider.get();
@@ -349,7 +339,4 @@ class MailboxApiImpl implements MailboxApi {
 		return (ArrayNode) arrayNode;
 	}
 
-	private String getBaseUrl(MailboxProperties properties) {
-		return urlConverter.convertOnionToBaseUrl(properties.getOnion());
-	}
 }

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxClient.java

@@ -1,55 +0,0 @@
-package org.briarproject.bramble.mailbox;
-
-import org.briarproject.bramble.api.contact.ContactId;
-import org.briarproject.bramble.api.mailbox.MailboxFolderId;
-import org.briarproject.bramble.api.mailbox.MailboxProperties;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-
-import javax.annotation.concurrent.ThreadSafe;
-
-@ThreadSafe
-@NotNullByDefault
-interface MailboxClient {
-
-	/**
-	 * Asynchronously starts the client.
-	 */
-	void start();
-
-	/**
-	 * Destroys the client and its workers, cancelling any pending tasks or
-	 * retries.
-	 */
-	void destroy();
-
-	/**
-	 * Assigns a contact to the client for upload.
-	 *
-	 * @param properties Properties for communicating with the mailbox
-	 * managed by this client.
-	 * @param folderId The ID of the folder to which files will be uploaded.
-	 */
-	void assignContactForUpload(ContactId c, MailboxProperties properties,
-			MailboxFolderId folderId);
-
-	/**
-	 * Deassigns a contact from the client for upload.
-	 */
-	void deassignContactForUpload(ContactId c);
-
-	/**
-	 * Assigns a contact to the client for download.
-	 *
-	 * @param properties Properties for communicating with the mailbox
-	 * managed by this client.
-	 * @param folderId The ID of the folder from which files will be
-	 * downloaded.
-	 */
-	void assignContactForDownload(ContactId c, MailboxProperties properties,
-			MailboxFolderId folderId);
-
-	/**
-	 * Deassigns a contact from the client for download.
-	 */
-	void deassignContactForDownload(ContactId c);
-}

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxClientFactory.java

@@ -1,21 +0,0 @@
-package org.briarproject.bramble.mailbox;
-
-import org.briarproject.bramble.api.mailbox.MailboxProperties;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-
-@NotNullByDefault
-interface MailboxClientFactory {
-
-	/**
-	 * Creates a client for communicating with a contact's mailbox.
-	 */
-	MailboxClient createContactMailboxClient(
-			TorReachabilityMonitor reachabilityMonitor);
-
-	/**
-	 * Creates a client for communicating with our own mailbox.
-	 */
-	MailboxClient createOwnMailboxClient(
-			TorReachabilityMonitor reachabilityMonitor,
-			MailboxProperties properties);
-}

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxClientFactoryImpl.java

@@ -1,52 +0,0 @@
-package org.briarproject.bramble.mailbox;
-
-import org.briarproject.bramble.api.lifecycle.IoExecutor;
-import org.briarproject.bramble.api.mailbox.MailboxProperties;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.system.TaskScheduler;
-
-import java.util.concurrent.Executor;
-
-import javax.inject.Inject;
-import javax.inject.Provider;
-
-@NotNullByDefault
-class MailboxClientFactoryImpl implements MailboxClientFactory {
-
-	private final MailboxWorkerFactory workerFactory;
-	private final TaskScheduler taskScheduler;
-	private final Executor ioExecutor;
-	private final Provider<ContactMailboxConnectivityChecker>
-			contactCheckerProvider;
-	private final Provider<OwnMailboxConnectivityChecker> ownCheckerProvider;
-
-	@Inject
-	MailboxClientFactoryImpl(MailboxWorkerFactory workerFactory,
-			TaskScheduler taskScheduler,
-			@IoExecutor Executor ioExecutor,
-			Provider<ContactMailboxConnectivityChecker> contactCheckerProvider,
-			Provider<OwnMailboxConnectivityChecker> ownCheckerProvider) {
-		this.workerFactory = workerFactory;
-		this.taskScheduler = taskScheduler;
-		this.ioExecutor = ioExecutor;
-		this.contactCheckerProvider = contactCheckerProvider;
-		this.ownCheckerProvider = ownCheckerProvider;
-	}
-
-	@Override
-	public MailboxClient createContactMailboxClient(
-			TorReachabilityMonitor reachabilityMonitor) {
-		ConnectivityChecker connectivityChecker = contactCheckerProvider.get();
-		return new ContactMailboxClient(workerFactory, connectivityChecker,
-				reachabilityMonitor);
-	}
-
-	@Override
-	public MailboxClient createOwnMailboxClient(
-			TorReachabilityMonitor reachabilityMonitor,
-			MailboxProperties properties) {
-		ConnectivityChecker connectivityChecker = ownCheckerProvider.get();
-		return new OwnMailboxClient(workerFactory, connectivityChecker,
-				reachabilityMonitor, taskScheduler, ioExecutor, properties);
-	}
-}

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxClientManager.java

@@ -1,667 +0,0 @@
-package org.briarproject.bramble.mailbox;
-
-import org.briarproject.bramble.api.contact.Contact;
-import org.briarproject.bramble.api.contact.ContactId;
-import org.briarproject.bramble.api.contact.ContactManager;
-import org.briarproject.bramble.api.contact.event.ContactRemovedEvent;
-import org.briarproject.bramble.api.db.DatabaseExecutor;
-import org.briarproject.bramble.api.db.DbException;
-import org.briarproject.bramble.api.db.TransactionManager;
-import org.briarproject.bramble.api.event.Event;
-import org.briarproject.bramble.api.event.EventExecutor;
-import org.briarproject.bramble.api.event.EventListener;
-import org.briarproject.bramble.api.lifecycle.Service;
-import org.briarproject.bramble.api.lifecycle.ServiceException;
-import org.briarproject.bramble.api.mailbox.MailboxProperties;
-import org.briarproject.bramble.api.mailbox.MailboxSettingsManager;
-import org.briarproject.bramble.api.mailbox.MailboxStatus;
-import org.briarproject.bramble.api.mailbox.MailboxUpdate;
-import org.briarproject.bramble.api.mailbox.MailboxUpdateManager;
-import org.briarproject.bramble.api.mailbox.MailboxUpdateWithMailbox;
-import org.briarproject.bramble.api.mailbox.MailboxVersion;
-import org.briarproject.bramble.api.mailbox.event.MailboxPairedEvent;
-import org.briarproject.bramble.api.mailbox.event.MailboxUnpairedEvent;
-import org.briarproject.bramble.api.mailbox.event.MailboxUpdateSentToNewContactEvent;
-import org.briarproject.bramble.api.mailbox.event.OwnMailboxConnectionStatusEvent;
-import org.briarproject.bramble.api.mailbox.event.RemoteMailboxUpdateEvent;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.plugin.Plugin;
-import org.briarproject.bramble.api.plugin.PluginManager;
-import org.briarproject.bramble.api.plugin.event.TransportActiveEvent;
-import org.briarproject.bramble.api.plugin.event.TransportInactiveEvent;
-
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
-import java.util.Map.Entry;
-import java.util.concurrent.CountDownLatch;
-import java.util.concurrent.Executor;
-import java.util.concurrent.atomic.AtomicBoolean;
-import java.util.logging.Logger;
-
-import javax.annotation.Nullable;
-import javax.annotation.concurrent.ThreadSafe;
-import javax.inject.Inject;
-
-import static java.util.logging.Level.WARNING;
-import static java.util.logging.Logger.getLogger;
-import static org.briarproject.bramble.api.mailbox.MailboxConstants.CLIENT_SUPPORTS;
-import static org.briarproject.bramble.api.mailbox.MailboxHelper.isClientCompatibleWithServer;
-import static org.briarproject.bramble.api.nullsafety.NullSafety.requireNonNull;
-import static org.briarproject.bramble.api.plugin.Plugin.State.ACTIVE;
-import static org.briarproject.bramble.api.plugin.TorConstants.ID;
-import static org.briarproject.bramble.util.LogUtils.logException;
-
-/**
- * This component manages a {@link MailboxClient} for each mailbox we know
- * about and are able to use (our own mailbox and/or contacts' mailboxes).
- * The clients are created when we come online (i.e. when the Tor plugin
- * becomes {@link Plugin.State#ACTIVE active}) and destroyed when we go
- * offline.
- * <p/>
- * The manager keeps track of the latest {@link MailboxUpdate} sent to and
- * received from each contact. These updates are used to decide which
- * mailboxes the manager needs clients for, and which mailbox (if any) should
- * be used for uploading data to and/or downloading data from each contact.
- * <p/>
- * The assignments of contacts to mailboxes for upload and/or download may
- * change when the following events happen:
- * <ul>
- *     <li> A mailbox is paired or unpaired </li>
- *     <li> A contact is added or removed </li>
- *     <li> A {@link MailboxUpdate} is received from a contact </li>
- *     <li> We discover that our own mailbox's supported API versions have
- *     changed </li>
- * </ul>
- * <p/>
- * The manager keeps its mutable state consistent with the state in the DB by
- * using commit actions and events to update the manager's state on the event
- * thread.
- */
-@ThreadSafe
-@NotNullByDefault
-class MailboxClientManager implements Service, EventListener {
-
-	private static final Logger LOG =
-			getLogger(MailboxClientManager.class.getName());
-
-	private final Executor eventExecutor, dbExecutor;
-	private final TransactionManager db;
-	private final ContactManager contactManager;
-	private final PluginManager pluginManager;
-	private final MailboxSettingsManager mailboxSettingsManager;
-	private final MailboxUpdateManager mailboxUpdateManager;
-	private final MailboxClientFactory mailboxClientFactory;
-	private final TorReachabilityMonitor reachabilityMonitor;
-	private final AtomicBoolean used = new AtomicBoolean(false);
-
-	// All of the following mutable state must only be accessed on the
-	// event thread
-	private final Map<ContactId, Updates> contactUpdates = new HashMap<>();
-	private final Map<ContactId, MailboxClient> contactClients =
-			new HashMap<>();
-	@Nullable
-	private MailboxProperties ownProperties = null;
-	@Nullable
-	private MailboxClient ownClient = null;
-	private boolean online = false, handleEvents = false;
-
-	@Inject
-	MailboxClientManager(@EventExecutor Executor eventExecutor,
-			@DatabaseExecutor Executor dbExecutor,
-			TransactionManager db,
-			ContactManager contactManager,
-			PluginManager pluginManager,
-			MailboxSettingsManager mailboxSettingsManager,
-			MailboxUpdateManager mailboxUpdateManager,
-			MailboxClientFactory mailboxClientFactory,
-			TorReachabilityMonitor reachabilityMonitor) {
-		this.eventExecutor = eventExecutor;
-		this.dbExecutor = dbExecutor;
-		this.db = db;
-		this.contactManager = contactManager;
-		this.pluginManager = pluginManager;
-		this.mailboxSettingsManager = mailboxSettingsManager;
-		this.mailboxUpdateManager = mailboxUpdateManager;
-		this.mailboxClientFactory = mailboxClientFactory;
-		this.reachabilityMonitor = reachabilityMonitor;
-	}
-
-	@Override
-	public void startService() throws ServiceException {
-		if (used.getAndSet(true)) throw new IllegalStateException();
-		reachabilityMonitor.start();
-		dbExecutor.execute(this::loadMailboxProperties);
-	}
-
-	@DatabaseExecutor
-	private void loadMailboxProperties() {
-		LOG.info("Loading mailbox properties");
-		try {
-			db.transaction(true, txn -> {
-				Map<ContactId, Updates> updates = new HashMap<>();
-				for (Contact c : contactManager.getContacts(txn)) {
-					MailboxUpdate local = mailboxUpdateManager
-							.getLocalUpdate(txn, c.getId());
-					MailboxUpdate remote = mailboxUpdateManager
-							.getRemoteUpdate(txn, c.getId());
-					updates.put(c.getId(), new Updates(local, remote));
-				}
-				MailboxProperties ownProps =
-						mailboxSettingsManager.getOwnMailboxProperties(txn);
-				// Use a commit action so the state in memory remains
-				// consistent with the state in the DB
-				txn.attach(() -> initialiseState(updates, ownProps));
-			});
-		} catch (DbException e) {
-			logException(LOG, WARNING, e);
-		}
-	}
-
-	@EventExecutor
-	private void initialiseState(Map<ContactId, Updates> updates,
-			@Nullable MailboxProperties ownProps) {
-		contactUpdates.putAll(updates);
-		ownProperties = ownProps;
-		Plugin tor = pluginManager.getPlugin(ID);
-		if (tor != null && tor.getState() == ACTIVE) {
-			LOG.info("Online");
-			online = true;
-			createClients();
-		}
-		// Now that the mutable state has been initialised we can start
-		// handling events. This is done in a commit action so that we don't
-		// miss any changes to the DB state or handle events for any changes
-		// that were already reflected in the initial load
-		handleEvents = true;
-	}
-
-	@EventExecutor
-	private void createClients() {
-		LOG.info("Creating clients");
-		for (Entry<ContactId, Updates> e : contactUpdates.entrySet()) {
-			ContactId c = e.getKey();
-			Updates u = e.getValue();
-			if (isContactMailboxUsable(u.remote)) {
-				// Create and start a client for the contact's mailbox
-				MailboxClient contactClient = createAndStartClient(c);
-				// Assign the contact to the contact's mailbox for upload
-				assignContactToContactMailboxForUpload(c, contactClient, u);
-				if (!isOwnMailboxUsable(ownProperties, u.remote)) {
-					// We don't have a usable mailbox, so assign the contact to
-					// the contact's mailbox for download too
-					assignContactToContactMailboxForDownload(c,
-							contactClient, u);
-				}
-			}
-		}
-		if (ownProperties == null) return;
-		if (!isOwnMailboxUsable(ownProperties)) {
-			LOG.warning("We have a mailbox but we can't use it");
-			return;
-		}
-		// Create and start a client for our mailbox
-		createAndStartClientForOwnMailbox();
-		// Assign contacts to our mailbox for upload/download
-		for (Entry<ContactId, Updates> e : contactUpdates.entrySet()) {
-			ContactId c = e.getKey();
-			Updates u = e.getValue();
-			if (isOwnMailboxUsable(ownProperties, u.remote)) {
-				// Assign the contact to our mailbox for download
-				assignContactToOwnMailboxForDownload(c, u);
-				if (!isContactMailboxUsable(u.remote)) {
-					// The contact doesn't have a usable mailbox, so assign
-					// the contact to our mailbox for upload too
-					assignContactToOwnMailboxForUpload(c, u);
-				}
-			}
-		}
-	}
-
-	@Override
-	public void stopService() throws ServiceException {
-		CountDownLatch latch = new CountDownLatch(1);
-		eventExecutor.execute(() -> {
-			handleEvents = false;
-			if (online) destroyClients();
-			latch.countDown();
-		});
-		reachabilityMonitor.destroy();
-		try {
-			latch.await();
-		} catch (InterruptedException e) {
-			throw new ServiceException(e);
-		}
-	}
-
-	@EventExecutor
-	private void destroyClients() {
-		LOG.info("Destroying clients");
-		for (MailboxClient client : contactClients.values()) {
-			client.destroy();
-		}
-		contactClients.clear();
-		destroyOwnClient();
-	}
-
-	@EventExecutor
-	private void destroyOwnClient() {
-		if (ownClient != null) {
-			ownClient.destroy();
-			ownClient = null;
-		}
-	}
-
-	@Override
-	public void eventOccurred(Event e) {
-		if (!handleEvents) return;
-		if (e instanceof TransportActiveEvent) {
-			TransportActiveEvent t = (TransportActiveEvent) e;
-			if (t.getTransportId().equals(ID)) onTorActive();
-		} else if (e instanceof TransportInactiveEvent) {
-			TransportInactiveEvent t = (TransportInactiveEvent) e;
-			if (t.getTransportId().equals(ID)) onTorInactive();
-		} else if (e instanceof MailboxPairedEvent) {
-			LOG.info("Mailbox paired");
-			MailboxPairedEvent m = (MailboxPairedEvent) e;
-			onMailboxPaired(m.getProperties(), m.getLocalUpdates());
-		} else if (e instanceof MailboxUnpairedEvent) {
-			LOG.info("Mailbox unpaired");
-			MailboxUnpairedEvent m = (MailboxUnpairedEvent) e;
-			onMailboxUnpaired(m.getLocalUpdates());
-		} else if (e instanceof MailboxUpdateSentToNewContactEvent) {
-			LOG.info("Contact added");
-			MailboxUpdateSentToNewContactEvent
-					m = (MailboxUpdateSentToNewContactEvent) e;
-			onContactAdded(m.getContactId(), m.getMailboxUpdate());
-		} else if (e instanceof ContactRemovedEvent) {
-			LOG.info("Contact removed");
-			ContactRemovedEvent c = (ContactRemovedEvent) e;
-			onContactRemoved(c.getContactId());
-		} else if (e instanceof RemoteMailboxUpdateEvent) {
-			LOG.info("Remote mailbox update");
-			RemoteMailboxUpdateEvent r = (RemoteMailboxUpdateEvent) e;
-			onRemoteMailboxUpdate(r.getContact(), r.getMailboxUpdate());
-		} else if (e instanceof OwnMailboxConnectionStatusEvent) {
-			OwnMailboxConnectionStatusEvent o =
-					(OwnMailboxConnectionStatusEvent) e;
-			onOwnMailboxConnectionStatusChanged(o.getStatus());
-		}
-	}
-
-	@EventExecutor
-	private void onTorActive() {
-		// If we checked the plugin at startup concurrently with the plugin
-		// becoming active then `online` may already be true when we receive
-		// the first TransportActiveEvent, in which case ignore it
-		if (online) return;
-		LOG.info("Online");
-		online = true;
-		createClients();
-	}
-
-	@EventExecutor
-	private void onTorInactive() {
-		// If we checked the plugin at startup concurrently with the plugin
-		// becoming inactive then `online` may already be false when we
-		// receive the first TransportInactiveEvent, in which case ignore it
-		if (!online) return;
-		LOG.info("Offline");
-		online = false;
-		destroyClients();
-	}
-
-	@EventExecutor
-	private void onMailboxPaired(MailboxProperties ownProps,
-			Map<ContactId, MailboxUpdateWithMailbox> localUpdates) {
-		for (Entry<ContactId, MailboxUpdateWithMailbox> e :
-				localUpdates.entrySet()) {
-			ContactId c = e.getKey();
-			Updates u = contactUpdates.get(c);
-			contactUpdates.put(c, new Updates(e.getValue(), u.remote));
-		}
-		ownProperties = ownProps;
-		if (!online) return;
-		if (!isOwnMailboxUsable(ownProperties)) {
-			LOG.warning("We have a mailbox but we can't use it");
-			return;
-		}
-		// Create and start a client for our mailbox
-		createAndStartClientForOwnMailbox();
-		// Assign contacts to our mailbox for upload/download
-		for (Entry<ContactId, Updates> e : contactUpdates.entrySet()) {
-			ContactId c = e.getKey();
-			Updates u = e.getValue();
-			if (!isOwnMailboxUsable(ownProperties, u.remote)) {
-				// Our mailbox isn't usable for communicating with this
-				// contact, so don't assign/reassign this contact
-				continue;
-			}
-			if (isContactMailboxUsable(u.remote)) {
-				// The contact has a usable mailbox, so the contact should
-				// currently be assigned to the contact's mailbox for upload
-				// and download. Reassign the contact to our mailbox for
-				// download
-				MailboxClient contactClient =
-						requireNonNull(contactClients.get(c));
-				contactClient.deassignContactForDownload(c);
-			} else {
-				// The contact doesn't have a usable mailbox, so assign the
-				// contact to our mailbox for upload
-				assignContactToOwnMailboxForUpload(c, u);
-			}
-			assignContactToOwnMailboxForDownload(c, u);
-		}
-	}
-
-	@EventExecutor
-	private void onMailboxUnpaired(Map<ContactId, MailboxUpdate> localUpdates) {
-		for (Entry<ContactId, MailboxUpdate> e : localUpdates.entrySet()) {
-			ContactId c = e.getKey();
-			Updates updates = contactUpdates.get(c);
-			contactUpdates.put(c, new Updates(e.getValue(), updates.remote));
-		}
-		MailboxProperties oldOwnProperties = ownProperties;
-		ownProperties = null;
-		if (!online) return;
-		// Destroy the client for our own mailbox, if any
-		destroyOwnClient();
-		// Reassign contacts to their own mailboxes for download where possible
-		for (Entry<ContactId, Updates> e : contactUpdates.entrySet()) {
-			ContactId c = e.getKey();
-			Updates u = e.getValue();
-			if (isContactMailboxUsable(u.remote) &&
-					isOwnMailboxUsable(oldOwnProperties, u.remote)) {
-				// The contact should currently be assigned to our mailbox
-				// for download. Reassign the contact to the contact's
-				// mailbox for download
-				MailboxClient contactClient =
-						requireNonNull(contactClients.get(c));
-				assignContactToContactMailboxForDownload(c, contactClient, u);
-			}
-		}
-	}
-
-	@EventExecutor
-	private void onContactAdded(ContactId c, MailboxUpdate u) {
-		Updates old = contactUpdates.put(c, new Updates(u, null));
-		if (old != null) throw new IllegalStateException();
-		// We haven't yet received an update from the newly added contact,
-		// so at this stage we don't need to assign the contact to any
-		// mailboxes for upload or download
-	}
-
-	@EventExecutor
-	private void onContactRemoved(ContactId c) {
-		Updates updates = requireNonNull(contactUpdates.remove(c));
-		if (!online) return;
-		// Destroy the client for the contact's mailbox, if any
-		MailboxClient client = contactClients.remove(c);
-		if (client != null) client.destroy();
-		// If we have a mailbox and the contact is assigned to it for upload
-		// and/or download, deassign the contact
-		if (ownProperties == null) return;
-		if (isOwnMailboxUsable(ownProperties, updates.remote)) {
-			// We have a usable mailbox, so the contact should currently be
-			// assigned to our mailbox for download. Deassign the contact from
-			// our mailbox for download
-			requireNonNull(ownClient).deassignContactForDownload(c);
-			if (!isContactMailboxUsable(updates.remote)) {
-				// The contact doesn't have a usable mailbox, so the contact
-				// should currently be assigned to our mailbox for upload.
-				// Deassign the contact from our mailbox for upload
-				requireNonNull(ownClient).deassignContactForUpload(c);
-			}
-		}
-	}
-
-	@EventExecutor
-	private void onRemoteMailboxUpdate(ContactId c, MailboxUpdate remote) {
-		Updates old = contactUpdates.get(c);
-		MailboxUpdate oldRemote = old.remote;
-		Updates u = new Updates(old.local, remote);
-		contactUpdates.put(c, u);
-		if (!online) return;
-		// What may have changed?
-		// * Contact's mailbox may be usable now, was unusable before
-		// * Contact's mailbox may be unusable now, was usable before
-		// * Contact's mailbox may have been replaced
-		// * Contact's mailbox may have changed its API versions
-		// * Contact may be able to use our mailbox now, was unable before
-		// * Contact may be unable to use our mailbox now, was able before
-		boolean wasContactMailboxUsable = isContactMailboxUsable(oldRemote);
-		boolean isContactMailboxUsable = isContactMailboxUsable(remote);
-		boolean wasOwnMailboxUsable =
-				isOwnMailboxUsable(ownProperties, oldRemote);
-		boolean isOwnMailboxUsable = isOwnMailboxUsable(ownProperties, remote);
-
-		// Create/destroy/replace the client for the contact's mailbox if needed
-		MailboxClient contactClient = null;
-		boolean clientReplaced = false;
-		if (isContactMailboxUsable) {
-			if (wasContactMailboxUsable) {
-				MailboxProperties oldProps = getMailboxProperties(oldRemote);
-				MailboxProperties newProps = getMailboxProperties(remote);
-				if (oldProps.equals(newProps)) {
-					// The contact previously had a usable mailbox, now has
-					// a usable mailbox, it's the same mailbox, and its API
-					// versions haven't changed. Keep using the existing client
-					contactClient = requireNonNull(contactClients.get(c));
-				} else {
-					// The contact previously had a usable mailbox and now has
-					// a usable mailbox, but either it's a new mailbox or its
-					// API versions have changed. Replace the client
-					requireNonNull(contactClients.remove(c)).destroy();
-					contactClient = createAndStartClient(c);
-					clientReplaced = true;
-				}
-			} else {
-				// The client didn't previously have a usable mailbox but now
-				// has one. Create and start a client
-				contactClient = createAndStartClient(c);
-			}
-		} else if (wasContactMailboxUsable) {
-			// The client previously had a usable mailbox but no longer does.
-			// Destroy the existing client
-			requireNonNull(contactClients.remove(c)).destroy();
-		}
-
-		boolean wasAssignedToOwnMailboxForUpload =
-				wasOwnMailboxUsable && !wasContactMailboxUsable;
-		boolean willBeAssignedToOwnMailboxForUpload =
-				isOwnMailboxUsable && !isContactMailboxUsable;
-
-		boolean wasAssignedToContactMailboxForDownload =
-				!wasOwnMailboxUsable && wasContactMailboxUsable;
-		boolean willBeAssignedToContactMailboxForDownload =
-				!isOwnMailboxUsable && isContactMailboxUsable;
-
-		// Deassign the contact for upload/download if needed
-		if (wasAssignedToOwnMailboxForUpload &&
-				!willBeAssignedToOwnMailboxForUpload) {
-			requireNonNull(ownClient).deassignContactForUpload(c);
-		}
-		if (wasOwnMailboxUsable && !isOwnMailboxUsable) {
-			requireNonNull(ownClient).deassignContactForDownload(c);
-		}
-		// If the client for the contact's mailbox was replaced or destroyed
-		// above then we don't need to deassign the contact for download
-		if (wasAssignedToContactMailboxForDownload &&
-				!willBeAssignedToContactMailboxForDownload &&
-				!clientReplaced && isContactMailboxUsable) {
-			requireNonNull(contactClient).deassignContactForDownload(c);
-		}
-		// We never need to deassign the contact from the contact's mailbox for
-		// upload: this would only be needed if the contact's mailbox were no
-		// longer usable, in which case the client would already have been
-		// destroyed above. Thanks to the linter for spotting this
-
-		// Assign the contact for upload/download if needed
-		if (!wasAssignedToOwnMailboxForUpload &&
-				willBeAssignedToOwnMailboxForUpload) {
-			assignContactToOwnMailboxForUpload(c, u);
-		}
-		if (!wasOwnMailboxUsable && isOwnMailboxUsable) {
-			assignContactToOwnMailboxForDownload(c, u);
-		}
-		if ((!wasContactMailboxUsable || clientReplaced) &&
-				isContactMailboxUsable) {
-			assignContactToContactMailboxForUpload(c, contactClient, u);
-		}
-		if ((!wasAssignedToContactMailboxForDownload || clientReplaced) &&
-				willBeAssignedToContactMailboxForDownload) {
-			assignContactToContactMailboxForDownload(c, contactClient, u);
-		}
-	}
-
-	@EventExecutor
-	private void onOwnMailboxConnectionStatusChanged(MailboxStatus status) {
-		if (!online || ownProperties == null) return;
-		List<MailboxVersion> oldServerSupports =
-				ownProperties.getServerSupports();
-		List<MailboxVersion> newServerSupports = status.getServerSupports();
-		if (!oldServerSupports.equals(newServerSupports)) {
-			LOG.info("Our mailbox's supported API versions have changed");
-			// This potentially affects every assignment of contacts to
-			// mailboxes for upload and download, so just rebuild the clients
-			// and assignments from scratch
-			destroyClients();
-			createClients();
-		}
-	}
-
-	@EventExecutor
-	private void createAndStartClientForOwnMailbox() {
-		if (ownClient != null) throw new IllegalStateException();
-		ownClient = mailboxClientFactory.createOwnMailboxClient(
-				reachabilityMonitor, requireNonNull(ownProperties));
-		ownClient.start();
-	}
-
-	@EventExecutor
-	private MailboxClient createAndStartClient(ContactId c) {
-		MailboxClient client = mailboxClientFactory
-				.createContactMailboxClient(reachabilityMonitor);
-		MailboxClient old = contactClients.put(c, client);
-		if (old != null) throw new IllegalStateException();
-		client.start();
-		return client;
-	}
-
-	@EventExecutor
-	private void assignContactToOwnMailboxForDownload(ContactId c, Updates u) {
-		MailboxProperties localProps = getMailboxProperties(u.local);
-		requireNonNull(ownClient).assignContactForDownload(c,
-				requireNonNull(ownProperties),
-				requireNonNull(localProps.getOutboxId()));
-	}
-
-	@EventExecutor
-	private void assignContactToOwnMailboxForUpload(ContactId c, Updates u) {
-		MailboxProperties localProps = getMailboxProperties(u.local);
-		requireNonNull(ownClient).assignContactForUpload(c,
-				requireNonNull(ownProperties),
-				requireNonNull(localProps.getInboxId()));
-	}
-
-	@EventExecutor
-	private void assignContactToContactMailboxForDownload(ContactId c,
-			MailboxClient contactClient, Updates u) {
-		MailboxProperties remoteProps =
-				getMailboxProperties(requireNonNull(u.remote));
-		contactClient.assignContactForDownload(c, remoteProps,
-				requireNonNull(remoteProps.getInboxId()));
-	}
-
-	@EventExecutor
-	private void assignContactToContactMailboxForUpload(ContactId c,
-			MailboxClient contactClient, Updates u) {
-		MailboxProperties remoteProps =
-				getMailboxProperties(requireNonNull(u.remote));
-		contactClient.assignContactForUpload(c, remoteProps,
-				requireNonNull(remoteProps.getOutboxId()));
-	}
-
-	/**
-	 * Returns the {@link MailboxProperties} included in the given update,
-	 * which must be a {@link MailboxUpdateWithMailbox}.
-	 */
-	private MailboxProperties getMailboxProperties(MailboxUpdate update) {
-		if (!(update instanceof MailboxUpdateWithMailbox)) {
-			throw new IllegalArgumentException();
-		}
-		MailboxUpdateWithMailbox mailbox = (MailboxUpdateWithMailbox) update;
-		return mailbox.getMailboxProperties();
-	}
-
-	/**
-	 * Returns true if we can use our own mailbox to communicate with the
-	 * contact that sent the given update.
-	 */
-	private boolean isOwnMailboxUsable(
-			@Nullable MailboxProperties ownProperties,
-			@Nullable MailboxUpdate remote) {
-		if (ownProperties == null || remote == null) return false;
-		return isMailboxUsable(remote.getClientSupports(),
-				ownProperties.getServerSupports());
-	}
-
-	/**
-	 * Returns true if we can use the contact's mailbox to communicate with
-	 * the contact that sent the given update.
-	 */
-	private boolean isContactMailboxUsable(@Nullable MailboxUpdate remote) {
-		if (remote instanceof MailboxUpdateWithMailbox) {
-			MailboxUpdateWithMailbox remoteMailbox =
-					(MailboxUpdateWithMailbox) remote;
-			return isMailboxUsable(remoteMailbox.getClientSupports(),
-					remoteMailbox.getMailboxProperties().getServerSupports());
-		}
-		return false;
-	}
-
-	/**
-	 * Returns true if we can communicate with a contact that has the given
-	 * client-supported API versions via a mailbox with the given
-	 * server-supported API versions.
-	 */
-	private boolean isMailboxUsable(List<MailboxVersion> contactClient,
-			List<MailboxVersion> server) {
-		return isClientCompatibleWithServer(contactClient, server)
-				&& isClientCompatibleWithServer(CLIENT_SUPPORTS, server);
-	}
-
-	/**
-	 * Returns true if our client-supported API versions are compatible with
-	 * our own mailbox's server-supported API versions.
-	 */
-	@SuppressWarnings("BooleanMethodIsAlwaysInverted")
-	private boolean isOwnMailboxUsable(MailboxProperties ownProperties) {
-		return isClientCompatibleWithServer(CLIENT_SUPPORTS,
-				ownProperties.getServerSupports());
-	}
-
-	/**
-	 * A container for the latest {@link MailboxUpdate updates} sent to and
-	 * received from a given contact.
-	 */
-	private static class Updates {
-
-		/**
-		 * The latest update sent to the contact.
-		 */
-		private final MailboxUpdate local;
-
-		/**
-		 * The latest update received from the contact, or null if no update
-		 * has been received.
-		 */
-		@Nullable
-		private final MailboxUpdate remote;
-
-		private Updates(MailboxUpdate local, @Nullable MailboxUpdate remote) {
-			this.local = local;
-			this.remote = remote;
-		}
-	}
-}

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxDownloadWorker.java

@@ -1,250 +0,0 @@
-package org.briarproject.bramble.mailbox;
-
-import org.briarproject.bramble.api.Cancellable;
-import org.briarproject.bramble.api.mailbox.MailboxFileId;
-import org.briarproject.bramble.api.mailbox.MailboxFolderId;
-import org.briarproject.bramble.api.mailbox.MailboxProperties;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.mailbox.ConnectivityChecker.ConnectivityObserver;
-import org.briarproject.bramble.mailbox.MailboxApi.ApiException;
-import org.briarproject.bramble.mailbox.MailboxApi.TolerableFailureException;
-import org.briarproject.bramble.mailbox.TorReachabilityMonitor.TorReachabilityObserver;
-
-import java.io.File;
-import java.io.IOException;
-import java.util.Queue;
-import java.util.logging.Logger;
-
-import javax.annotation.Nullable;
-import javax.annotation.concurrent.GuardedBy;
-import javax.annotation.concurrent.ThreadSafe;
-
-import static java.util.logging.Logger.getLogger;
-
-@ThreadSafe
-@NotNullByDefault
-abstract class MailboxDownloadWorker implements MailboxWorker,
-		ConnectivityObserver, TorReachabilityObserver {
-
-	/**
-	 * When the worker is started it waits for a connectivity check, then
-	 * starts its first download cycle: checking for files to download,
-	 * downloading and deleting the files, and checking again until all files
-	 * have been downloaded and deleted.
-	 * <p>
-	 * The worker then waits for our Tor hidden service to be reachable before
-	 * starting its second download cycle. This ensures that if a contact
-	 * tried and failed to connect to our hidden service before it was
-	 * reachable, and therefore uploaded a file to the mailbox instead, we'll
-	 * find the file in the second download cycle.
-	 */
-	protected enum State {
-		CREATED,
-		CONNECTIVITY_CHECK,
-		DOWNLOAD_CYCLE_1,
-		WAITING_FOR_TOR,
-		DOWNLOAD_CYCLE_2,
-		FINISHED,
-		DESTROYED
-	}
-
-	protected static final Logger LOG =
-			getLogger(MailboxDownloadWorker.class.getName());
-
-	private final ConnectivityChecker connectivityChecker;
-	private final TorReachabilityMonitor torReachabilityMonitor;
-	protected final MailboxApiCaller mailboxApiCaller;
-	protected final MailboxApi mailboxApi;
-	private final MailboxFileManager mailboxFileManager;
-	protected final MailboxProperties mailboxProperties;
-	protected final Object lock = new Object();
-
-	@GuardedBy("lock")
-	protected State state = State.CREATED;
-
-	@GuardedBy("lock")
-	@Nullable
-	protected Cancellable apiCall = null;
-
-	/**
-	 * Creates the API call that starts the worker's download cycle.
-	 */
-	protected abstract ApiCall createApiCallForDownloadCycle();
-
-	MailboxDownloadWorker(
-			ConnectivityChecker connectivityChecker,
-			TorReachabilityMonitor torReachabilityMonitor,
-			MailboxApiCaller mailboxApiCaller,
-			MailboxApi mailboxApi,
-			MailboxFileManager mailboxFileManager,
-			MailboxProperties mailboxProperties) {
-		this.connectivityChecker = connectivityChecker;
-		this.torReachabilityMonitor = torReachabilityMonitor;
-		this.mailboxApiCaller = mailboxApiCaller;
-		this.mailboxApi = mailboxApi;
-		this.mailboxFileManager = mailboxFileManager;
-		this.mailboxProperties = mailboxProperties;
-	}
-
-	@Override
-	public void start() {
-		LOG.info("Started");
-		synchronized (lock) {
-			// Don't allow the worker to be reused
-			if (state != State.CREATED) return;
-			state = State.CONNECTIVITY_CHECK;
-		}
-		// Avoid leaking observer in case destroy() is called concurrently
-		// before observer is added
-		connectivityChecker.checkConnectivity(mailboxProperties, this);
-		boolean destroyed;
-		synchronized (lock) {
-			destroyed = state == State.DESTROYED;
-		}
-		if (destroyed) connectivityChecker.removeObserver(this);
-	}
-
-	@Override
-	public void destroy() {
-		LOG.info("Destroyed");
-		Cancellable apiCall;
-		synchronized (lock) {
-			state = State.DESTROYED;
-			apiCall = this.apiCall;
-			this.apiCall = null;
-		}
-		if (apiCall != null) apiCall.cancel();
-		connectivityChecker.removeObserver(this);
-		torReachabilityMonitor.removeObserver(this);
-	}
-
-	@Override
-	public void onConnectivityCheckSucceeded() {
-		LOG.info("Connectivity check succeeded");
-		synchronized (lock) {
-			if (state != State.CONNECTIVITY_CHECK) return;
-			state = State.DOWNLOAD_CYCLE_1;
-			// Start first download cycle
-			apiCall = mailboxApiCaller.retryWithBackoff(
-					createApiCallForDownloadCycle());
-		}
-	}
-
-	void onDownloadCycleFinished() {
-		boolean addObserver = false;
-		synchronized (lock) {
-			if (state == State.DOWNLOAD_CYCLE_1) {
-				LOG.info("First download cycle finished");
-				state = State.WAITING_FOR_TOR;
-				apiCall = null;
-				addObserver = true;
-			} else if (state == State.DOWNLOAD_CYCLE_2) {
-				LOG.info("Second download cycle finished");
-				state = State.FINISHED;
-				apiCall = null;
-			}
-		}
-		if (addObserver) {
-			// Avoid leaking observer in case destroy() is called concurrently
-			// before observer is added
-			torReachabilityMonitor.addOneShotObserver(this);
-			boolean destroyed;
-			synchronized (lock) {
-				destroyed = state == State.DESTROYED;
-			}
-			if (destroyed) torReachabilityMonitor.removeObserver(this);
-		}
-	}
-
-	void downloadNextFile(Queue<FolderFile> queue) {
-		synchronized (lock) {
-			if (state == State.DESTROYED) return;
-			if (queue.isEmpty()) {
-				// Check for files again, as new files may have arrived while
-				// we were downloading
-				apiCall = mailboxApiCaller.retryWithBackoff(
-						createApiCallForDownloadCycle());
-			} else {
-				FolderFile file = queue.remove();
-				apiCall = mailboxApiCaller.retryWithBackoff(
-						new SimpleApiCall(() ->
-								apiCallDownloadFile(file, queue)));
-			}
-		}
-	}
-
-	private void apiCallDownloadFile(FolderFile file, Queue<FolderFile> queue)
-			throws IOException, ApiException {
-		synchronized (lock) {
-			if (state == State.DESTROYED) return;
-		}
-		LOG.info("Downloading file");
-		File tempFile = mailboxFileManager.createTempFileForDownload();
-		try {
-			mailboxApi.getFile(mailboxProperties, file.folderId, file.fileId,
-					tempFile);
-		} catch (IOException | ApiException e) {
-			if (!tempFile.delete()) {
-				LOG.warning("Failed to delete temporary file");
-			}
-			throw e;
-		} catch (TolerableFailureException e) {
-			// File not found - continue to the next file
-			LOG.warning("File does not exist");
-			if (!tempFile.delete()) {
-				LOG.warning("Failed to delete temporary file");
-			}
-			downloadNextFile(queue);
-			return;
-		}
-		mailboxFileManager.handleDownloadedFile(tempFile);
-		deleteFile(file, queue);
-	}
-
-	private void deleteFile(FolderFile file, Queue<FolderFile> queue) {
-		synchronized (lock) {
-			if (state == State.DESTROYED) return;
-			apiCall = mailboxApiCaller.retryWithBackoff(
-					new SimpleApiCall(() -> apiCallDeleteFile(file, queue)));
-		}
-	}
-
-	private void apiCallDeleteFile(FolderFile file, Queue<FolderFile> queue)
-			throws IOException, ApiException {
-		synchronized (lock) {
-			if (state == State.DESTROYED) return;
-		}
-		try {
-			mailboxApi.deleteFile(mailboxProperties, file.folderId,
-					file.fileId);
-		} catch (TolerableFailureException e) {
-			// File not found - continue to the next file
-			LOG.warning("File does not exist");
-		}
-		downloadNextFile(queue);
-	}
-
-	@Override
-	public void onTorReachable() {
-		LOG.info("Our Tor hidden service is reachable");
-		synchronized (lock) {
-			if (state != State.WAITING_FOR_TOR) return;
-			state = State.DOWNLOAD_CYCLE_2;
-			// Start second download cycle
-			apiCall = mailboxApiCaller.retryWithBackoff(
-					createApiCallForDownloadCycle());
-		}
-	}
-
-	// Package access for testing
-	static class FolderFile {
-
-		final MailboxFolderId folderId;
-		final MailboxFileId fileId;
-
-		FolderFile(MailboxFolderId folderId, MailboxFileId fileId) {
-			this.folderId = folderId;
-			this.fileId = fileId;
-		}
-	}
-}

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxFileManager.java

@@ -1,8 +1,6 @@
 package org.briarproject.bramble.mailbox;
 
-import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.sync.OutgoingSessionRecord;
 
 import java.io.File;
 import java.io.IOException;
@@ -18,14 +16,6 @@ interface MailboxFileManager {
 	 */
 	File createTempFileForDownload() throws IOException;
 
-	/**
-	 * Creates a file to be uploaded to the given contact and writes any
-	 * waiting data to the file. The IDs of any messages sent or acked will
-	 * be added to the given {@link OutgoingSessionRecord}.
-	 */
-	File createAndWriteTempFileForUpload(ContactId contactId,
-			OutgoingSessionRecord sessionRecord) throws IOException;
-
 	/**
 	 * Handles a file that has been downloaded. The file should be created
 	 * with {@link #createTempFileForDownload()}.

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxFileManagerImpl.java

@@ -1,7 +1,6 @@
 package org.briarproject.bramble.mailbox;
 
 import org.briarproject.bramble.api.connection.ConnectionManager;
-import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.event.Event;
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.event.EventListener;
@@ -11,18 +10,13 @@ import org.briarproject.bramble.api.mailbox.MailboxDirectory;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.PluginManager;
 import org.briarproject.bramble.api.plugin.TransportConnectionReader;
-import org.briarproject.bramble.api.plugin.TransportConnectionWriter;
 import org.briarproject.bramble.api.plugin.event.TransportActiveEvent;
 import org.briarproject.bramble.api.plugin.simplex.SimplexPlugin;
 import org.briarproject.bramble.api.properties.TransportProperties;
-import org.briarproject.bramble.api.sync.OutgoingSessionRecord;
 
 import java.io.File;
 import java.io.IOException;
 import java.io.InputStream;
-import java.io.OutputStream;
-import java.util.concurrent.ArrayBlockingQueue;
-import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.Executor;
 import java.util.logging.Logger;
@@ -36,7 +30,6 @@ import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleS
 import static org.briarproject.bramble.api.mailbox.MailboxConstants.ID;
 import static org.briarproject.bramble.api.nullsafety.NullSafety.requireNonNull;
 import static org.briarproject.bramble.api.plugin.file.FileConstants.PROP_PATH;
-import static org.briarproject.bramble.util.IoUtils.delete;
 import static org.briarproject.bramble.util.LogUtils.logException;
 
 @ThreadSafe
@@ -48,7 +41,6 @@ class MailboxFileManagerImpl implements MailboxFileManager, EventListener {
 
 	// Package access for testing
 	static final String DOWNLOAD_DIR_NAME = "downloads";
-	static final String UPLOAD_DIR_NAME = "uploads";
 
 	private final Executor ioExecutor;
 	private final PluginManager pluginManager;
@@ -75,44 +67,14 @@ class MailboxFileManagerImpl implements MailboxFileManager, EventListener {
 
 	@Override
 	public File createTempFileForDownload() throws IOException {
-		return createTempFile(DOWNLOAD_DIR_NAME);
-	}
-
-	@Override
-	public File createAndWriteTempFileForUpload(ContactId contactId,
-			OutgoingSessionRecord sessionRecord) throws IOException {
-		File f = createTempFile(UPLOAD_DIR_NAME);
-		// We shouldn't reach this point until the plugin has been started
-		SimplexPlugin plugin =
-				(SimplexPlugin) requireNonNull(pluginManager.getPlugin(ID));
-		TransportProperties p = new TransportProperties();
-		p.put(PROP_PATH, f.getAbsolutePath());
-		TransportConnectionWriter writer = plugin.createWriter(p);
-		if (writer == null) {
-			delete(f);
-			throw new IOException();
-		}
-		MailboxFileWriter decorated = new MailboxFileWriter(writer);
-		LOG.info("Writing file for upload");
-		connectionManager.manageOutgoingConnection(contactId, ID, decorated,
-				sessionRecord);
-		if (decorated.awaitDisposal()) {
-			// An exception was thrown during the session - delete the file
-			delete(f);
-			throw new IOException();
-		}
-		return f;
-	}
-
-	private File createTempFile(String dirName) throws IOException {
 		// Wait for orphaned files to be handled before creating new files
 		try {
 			orphanLatch.await();
 		} catch (InterruptedException e) {
 			throw new IOException(e);
 		}
-		File dir = createDirectoryIfNeeded(dirName);
-		return File.createTempFile("mailbox", ".tmp", dir);
+		File downloadDir = createDirectoryIfNeeded(DOWNLOAD_DIR_NAME);
+		return File.createTempFile("mailbox", ".tmp", downloadDir);
 	}
 
 	private File createDirectoryIfNeeded(String name) throws IOException {
@@ -154,8 +116,6 @@ class MailboxFileManagerImpl implements MailboxFileManager, EventListener {
 
 	@Override
 	public void eventOccurred(Event e) {
-		// Wait for the transport to become active before handling orphaned
-		// files so that we can get the plugin from the plugin manager
 		if (e instanceof TransportActiveEvent) {
 			TransportActiveEvent t = (TransportActiveEvent) e;
 			if (t.getTransportId().equals(ID)) {
@@ -167,25 +127,17 @@ class MailboxFileManagerImpl implements MailboxFileManager, EventListener {
 
 	/**
 	 * This method is called at startup, as soon as the plugin is started, to
-	 * delete any files that were left in the upload directory at the last
-	 * shutdown and handle any files that were left in the download directory.
+	 * handle any files that were left in the download directory at the last
+	 * shutdown.
 	 */
 	@IoExecutor
 	private void handleOrphanedFiles() {
 		try {
-			File uploadDir = createDirectoryIfNeeded(UPLOAD_DIR_NAME);
-			File[] orphanedUploads = uploadDir.listFiles();
-			if (orphanedUploads != null) {
-				for (File f : orphanedUploads) delete(f);
-			}
 			File downloadDir = createDirectoryIfNeeded(DOWNLOAD_DIR_NAME);
-			File[] orphanedDownloads = downloadDir.listFiles();
-			// Now that we've got the list of orphaned downloads, new files
-			// can be created in the download directory
+			File[] orphans = downloadDir.listFiles();
+			// Now that we've got the list of orphans, new files can be created
 			orphanLatch.countDown();
-			if (orphanedDownloads != null) {
-				for (File f : orphanedDownloads) handleDownloadedFile(f);
-			}
+			if (orphans != null) for (File f : orphans) handleDownloadedFile(f);
 		} catch (IOException e) {
 			logException(LOG, WARNING, e);
 		}
@@ -213,58 +165,9 @@ class MailboxFileManagerImpl implements MailboxFileManager, EventListener {
 			delegate.dispose(exception, recognised);
 			if (isHandlingComplete(exception, recognised)) {
 				LOG.info("Deleting downloaded file");
-				delete(file);
-			}
-		}
-	}
-
-	private static class MailboxFileWriter
-			implements TransportConnectionWriter {
-
-		private final TransportConnectionWriter delegate;
-		private final BlockingQueue<Boolean> disposalResult =
-				new ArrayBlockingQueue<>(1);
-
-		private MailboxFileWriter(TransportConnectionWriter delegate) {
-			this.delegate = delegate;
-		}
-
-		@Override
-		public long getMaxLatency() {
-			return delegate.getMaxLatency();
-		}
-
-		@Override
-		public int getMaxIdleTime() {
-			return delegate.getMaxIdleTime();
-		}
-
-		@Override
-		public boolean isLossyAndCheap() {
-			return delegate.isLossyAndCheap();
-		}
-
-		@Override
-		public OutputStream getOutputStream() throws IOException {
-			return delegate.getOutputStream();
-		}
-
-		@Override
-		public void dispose(boolean exception) throws IOException {
-			delegate.dispose(exception);
-			disposalResult.add(exception);
-		}
-
-		/**
-		 * Waits for the delegate to be disposed and returns true if an
-		 * exception occurred.
-		 */
-		private boolean awaitDisposal() {
-			try {
-				return disposalResult.take();
-			} catch (InterruptedException e) {
-				LOG.info("Interrupted while waiting for disposal");
-				return true;
+				if (!file.delete()) {
+					LOG.warning("Failed to delete downloaded file");
+				}
 			}
 		}
 	}

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxManagerImpl.java

@@ -9,12 +9,10 @@ import org.briarproject.bramble.api.mailbox.MailboxPairingTask;
 import org.briarproject.bramble.api.mailbox.MailboxProperties;
 import org.briarproject.bramble.api.mailbox.MailboxSettingsManager;
 import org.briarproject.bramble.api.mailbox.MailboxStatus;
-import org.briarproject.bramble.api.mailbox.MailboxVersion;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.system.Clock;
 
 import java.io.IOException;
-import java.util.List;
 import java.util.concurrent.Executor;
 import java.util.logging.Logger;
 
@@ -100,35 +98,34 @@ class MailboxManagerImpl implements MailboxManager {
 
 	@Override
 	public boolean checkConnection() {
-		List<MailboxVersion> versions = null;
+		boolean success;
 		try {
 			MailboxProperties props = db.transactionWithNullableResult(true,
 					mailboxSettingsManager::getOwnMailboxProperties);
 			if (props == null) throw new DbException();
-			versions = api.getServerSupports(props);
+			success = api.checkStatus(props);
 		} catch (DbException e) {
 			logException(LOG, WARNING, e);
 			// we don't treat this is a failure to record
 			return false;
 		} catch (IOException | MailboxApi.ApiException e) {
 			// we record this as a failure
+			success = false;
 			logException(LOG, WARNING, e);
 		}
 		try {
-			recordCheckResult(versions);
+			recordCheckResult(success);
 		} catch (DbException e) {
 			logException(LOG, WARNING, e);
 		}
-		return versions != null;
+		return success;
 	}
 
-	private void recordCheckResult(@Nullable List<MailboxVersion> versions)
-			throws DbException {
+	private void recordCheckResult(boolean success) throws DbException {
 		long now = clock.currentTimeMillis();
 		db.transaction(false, txn -> {
-			if (versions != null) {
-				mailboxSettingsManager
-						.recordSuccessfulConnection(txn, now, versions);
+			if (success) {
+				mailboxSettingsManager.recordSuccessfulConnection(txn, now);
 			} else {
 				mailboxSettingsManager.recordFailedConnectionAttempt(txn, now);
 			}

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxModule.java

@@ -4,22 +4,17 @@ import org.briarproject.bramble.api.FeatureFlags;
 import org.briarproject.bramble.api.client.ClientHelper;
 import org.briarproject.bramble.api.contact.ContactManager;
 import org.briarproject.bramble.api.data.MetadataEncoder;
-import org.briarproject.bramble.api.db.DatabaseExecutor;
-import org.briarproject.bramble.api.db.TransactionManager;
 import org.briarproject.bramble.api.event.EventBus;
-import org.briarproject.bramble.api.event.EventExecutor;
 import org.briarproject.bramble.api.lifecycle.LifecycleManager;
 import org.briarproject.bramble.api.mailbox.MailboxManager;
 import org.briarproject.bramble.api.mailbox.MailboxSettingsManager;
 import org.briarproject.bramble.api.mailbox.MailboxUpdateManager;
 import org.briarproject.bramble.api.mailbox.MailboxVersion;
-import org.briarproject.bramble.api.plugin.PluginManager;
 import org.briarproject.bramble.api.sync.validation.ValidationManager;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.api.versioning.ClientVersioningManager;
 
 import java.util.List;
-import java.util.concurrent.Executor;
 
 import javax.inject.Inject;
 import javax.inject.Singleton;
@@ -42,8 +37,6 @@ public class MailboxModule {
 		MailboxUpdateManager mailboxUpdateManager;
 		@Inject
 		MailboxFileManager mailboxFileManager;
-		@Inject
-		MailboxClientManager mailboxClientManager;
 	}
 
 	@Provides
@@ -59,19 +52,13 @@ public class MailboxModule {
 	}
 
 	@Provides
-	@Singleton
 	MailboxSettingsManager provideMailboxSettingsManager(
 			MailboxSettingsManagerImpl mailboxSettingsManager) {
 		return mailboxSettingsManager;
 	}
 
 	@Provides
-	UrlConverter provideUrlConverter(UrlConverterImpl urlConverter) {
-		return urlConverter;
-	}
-
-	@Provides
-	MailboxApi provideMailboxApi(MailboxApiImpl mailboxApi) {
+	MailboxApi providesMailboxApi(MailboxApiImpl mailboxApi) {
 		return mailboxApi;
 	}
 
@@ -127,55 +114,4 @@ public class MailboxModule {
 		}
 		return mailboxFileManager;
 	}
-
-	@Provides
-	MailboxWorkerFactory provideMailboxWorkerFactory(
-			MailboxWorkerFactoryImpl mailboxWorkerFactory) {
-		return mailboxWorkerFactory;
-	}
-
-	@Provides
-	MailboxClientFactory provideMailboxClientFactory(
-			MailboxClientFactoryImpl mailboxClientFactory) {
-		return mailboxClientFactory;
-	}
-
-	@Provides
-	MailboxApiCaller provideMailboxApiCaller(
-			MailboxApiCallerImpl mailboxApiCaller) {
-		return mailboxApiCaller;
-	}
-
-	@Provides
-	@Singleton
-	TorReachabilityMonitor provideTorReachabilityMonitor(
-			TorReachabilityMonitorImpl reachabilityMonitor) {
-		return reachabilityMonitor;
-	}
-
-	@Provides
-	@Singleton
-	MailboxClientManager provideMailboxClientManager(
-			@EventExecutor Executor eventExecutor,
-			@DatabaseExecutor Executor dbExecutor,
-			TransactionManager db,
-			ContactManager contactManager,
-			PluginManager pluginManager,
-			MailboxSettingsManager mailboxSettingsManager,
-			MailboxUpdateManager mailboxUpdateManager,
-			MailboxClientFactory mailboxClientFactory,
-			TorReachabilityMonitor reachabilityMonitor,
-			FeatureFlags featureFlags,
-			LifecycleManager lifecycleManager,
-			EventBus eventBus) {
-		MailboxClientManager manager = new MailboxClientManager(eventExecutor,
-				dbExecutor, db, contactManager, pluginManager,
-				mailboxSettingsManager, mailboxUpdateManager,
-				mailboxClientFactory, reachabilityMonitor);
-		if (featureFlags.shouldEnableMailbox()) {
-			lifecycleManager.registerService(manager);
-			eventBus.addListener(manager);
-		}
-		return manager;
-	}
 }

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxPairingTaskImpl.java

@@ -120,8 +120,7 @@ class MailboxPairingTaskImpl implements MailboxPairingTask {
 		db.transaction(false, txn -> {
 			mailboxSettingsManager
 					.setOwnMailboxProperties(txn, ownerProperties);
-			mailboxSettingsManager.recordSuccessfulConnection(txn, time,
-					ownerProperties.getServerSupports());
+			mailboxSettingsManager.recordSuccessfulConnection(txn, time);
 			// A (possibly new) mailbox is paired. Reset message retransmission
 			// timers for contacts who doesn't have their own mailbox. This way,
 			// data stranded on our old mailbox will be re-uploaded to our new.
@@ -178,9 +177,10 @@ class MailboxPairingTaskImpl implements MailboxPairingTask {
 		LOG.info("QR code is valid");
 		byte[] onionPubKey = Arrays.copyOfRange(bytes, 1, 33);
 		String onion = crypto.encodeOnion(onionPubKey);
+		String baseUrl = "http://" + onion + ".onion"; // TODO
 		byte[] tokenBytes = Arrays.copyOfRange(bytes, 33, 65);
 		MailboxAuthToken setupToken = new MailboxAuthToken(tokenBytes);
-		return new MailboxProperties(onion, setupToken, new ArrayList<>());
+		return new MailboxProperties(baseUrl, setupToken, new ArrayList<>());
 	}
 
 }

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxSettingsManagerImpl.java

@@ -20,13 +20,13 @@ import java.util.List;
 import java.util.concurrent.CopyOnWriteArrayList;
 
 import javax.annotation.Nullable;
-import javax.annotation.concurrent.ThreadSafe;
+import javax.annotation.concurrent.Immutable;
 import javax.inject.Inject;
 
 import static java.util.Collections.emptyList;
 import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
 
-@ThreadSafe
+@Immutable
 @NotNullByDefault
 class MailboxSettingsManagerImpl implements MailboxSettingsManager {
 
@@ -74,13 +74,19 @@ class MailboxSettingsManagerImpl implements MailboxSettingsManager {
 	public void setOwnMailboxProperties(Transaction txn, MailboxProperties p)
 			throws DbException {
 		Settings s = new Settings();
-		s.put(SETTINGS_KEY_ONION, p.getOnion());
+		s.put(SETTINGS_KEY_ONION, p.getBaseUrl());
 		s.put(SETTINGS_KEY_TOKEN, p.getAuthToken().toString());
 		List<MailboxVersion> serverSupports = p.getServerSupports();
-		encodeServerSupports(serverSupports, s);
+		int[] ints = new int[serverSupports.size() * 2];
+		int i = 0;
+		for (MailboxVersion v : serverSupports) {
+			ints[i++] = v.getMajor();
+			ints[i++] = v.getMinor();
+		}
+		s.putIntArray(SETTINGS_KEY_SERVER_SUPPORTS, ints);
 		settingsManager.mergeSettings(txn, s, SETTINGS_NAMESPACE);
 		for (MailboxHook hook : hooks) {
-			hook.mailboxPaired(txn, p);
+			hook.mailboxPaired(txn, p.getOnion(), p.getServerSupports());
 		}
 	}
 
@@ -89,10 +95,6 @@ class MailboxSettingsManagerImpl implements MailboxSettingsManager {
 		Settings s = new Settings();
 		s.put(SETTINGS_KEY_ONION, "");
 		s.put(SETTINGS_KEY_TOKEN, "");
-		s.put(SETTINGS_KEY_ATTEMPTS, "");
-		s.put(SETTINGS_KEY_LAST_ATTEMPT, "");
-		s.put(SETTINGS_KEY_LAST_SUCCESS, "");
-		s.put(SETTINGS_KEY_SERVER_SUPPORTS, "");
 		settingsManager.mergeSettings(txn, s, SETTINGS_NAMESPACE);
 		for (MailboxHook hook : hooks) {
 			hook.mailboxUnpaired(txn);
@@ -117,38 +119,25 @@ class MailboxSettingsManagerImpl implements MailboxSettingsManager {
 	}
 
 	@Override
-	public void recordSuccessfulConnection(Transaction txn, long now,
-			List<MailboxVersion> versions) throws DbException {
-		// if we no longer have a paired mailbox, return
+	public void recordSuccessfulConnection(Transaction txn, long now)
+			throws DbException {
 		Settings oldSettings =
 				settingsManager.getSettings(txn, SETTINGS_NAMESPACE);
-		String onion = oldSettings.get(SETTINGS_KEY_ONION);
-		String token = oldSettings.get(SETTINGS_KEY_TOKEN);
-		if (isNullOrEmpty(onion) || isNullOrEmpty(token)) return;
 		Settings s = new Settings();
-		// record the successful connection
 		s.putLong(SETTINGS_KEY_LAST_ATTEMPT, now);
 		s.putLong(SETTINGS_KEY_LAST_SUCCESS, now);
 		s.putInt(SETTINGS_KEY_ATTEMPTS, 0);
-		encodeServerSupports(versions, s);
 		settingsManager.mergeSettings(txn, s, SETTINGS_NAMESPACE);
-		for (MailboxHook hook : hooks) {
-			hook.serverSupportedVersionsReceived(txn, versions);
-		}
-		// broadcast status event
-		MailboxStatus status = new MailboxStatus(now, now, 0, versions);
+		List<MailboxVersion> serverSupports = parseServerSupports(oldSettings);
+		MailboxStatus status = new MailboxStatus(now, now, 0, serverSupports);
 		txn.attach(new OwnMailboxConnectionStatusEvent(status));
 	}
 
 	@Override
 	public void recordFailedConnectionAttempt(Transaction txn, long now)
 			throws DbException {
-		// if we no longer have a paired mailbox, return
 		Settings oldSettings =
 				settingsManager.getSettings(txn, SETTINGS_NAMESPACE);
-		String onion = oldSettings.get(SETTINGS_KEY_ONION);
-		String token = oldSettings.get(SETTINGS_KEY_TOKEN);
-		if (isNullOrEmpty(onion) || isNullOrEmpty(token)) return;
 		int newAttempts = 1 + oldSettings.getInt(SETTINGS_KEY_ATTEMPTS, 0);
 		long lastSuccess = oldSettings.getLong(SETTINGS_KEY_LAST_SUCCESS, 0);
 		Settings newSettings = new Settings();
@@ -182,17 +171,6 @@ class MailboxSettingsManagerImpl implements MailboxSettingsManager {
 		return filename;
 	}
 
-	private void encodeServerSupports(List<MailboxVersion> serverSupports,
-			Settings s) {
-		int[] ints = new int[serverSupports.size() * 2];
-		int i = 0;
-		for (MailboxVersion v : serverSupports) {
-			ints[i++] = v.getMajor();
-			ints[i++] = v.getMinor();
-		}
-		s.putIntArray(SETTINGS_KEY_SERVER_SUPPORTS, ints);
-	}
-
 	private List<MailboxVersion> parseServerSupports(Settings s)
 			throws DbException {
 		if (!s.containsKey(SETTINGS_KEY_SERVER_SUPPORTS)) return emptyList();

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxUpdateManagerImpl.java

@@ -25,9 +25,6 @@ import org.briarproject.bramble.api.mailbox.MailboxUpdate;
 import org.briarproject.bramble.api.mailbox.MailboxUpdateManager;
 import org.briarproject.bramble.api.mailbox.MailboxUpdateWithMailbox;
 import org.briarproject.bramble.api.mailbox.MailboxVersion;
-import org.briarproject.bramble.api.mailbox.event.MailboxPairedEvent;
-import org.briarproject.bramble.api.mailbox.event.MailboxUnpairedEvent;
-import org.briarproject.bramble.api.mailbox.event.MailboxUpdateSentToNewContactEvent;
 import org.briarproject.bramble.api.mailbox.event.RemoteMailboxUpdateEvent;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.Group;
@@ -41,7 +38,6 @@ import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.api.versioning.ClientVersioningManager;
 import org.briarproject.bramble.api.versioning.ClientVersioningManager.ClientVersioningHook;
 
-import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
@@ -49,9 +45,6 @@ import java.util.Map.Entry;
 import javax.annotation.Nullable;
 import javax.inject.Inject;
 
-import static java.util.Collections.emptyList;
-import static org.briarproject.bramble.api.data.BdfDictionary.NULL_VALUE;
-import static org.briarproject.bramble.api.nullsafety.NullSafety.requireNonNull;
 import static org.briarproject.bramble.api.sync.validation.IncomingMessageHook.DeliveryAction.ACCEPT_DO_NOT_SHARE;
 
 @NotNullByDefault
@@ -123,7 +116,7 @@ class MailboxUpdateManagerImpl implements MailboxUpdateManager,
 			db.addGroup(txn, localGroup);
 			// Set things up for any pre-existing contacts
 			for (Contact c : db.getContacts(txn)) {
-				addingContact(txn, c, false);
+				addingContact(txn, c);
 			}
 		}
 
@@ -139,17 +132,6 @@ class MailboxUpdateManagerImpl implements MailboxUpdateManager,
 
 	@Override
 	public void addingContact(Transaction txn, Contact c) throws DbException {
-		addingContact(txn, c, true);
-	}
-
-	/**
-	 * @param attachEvent True if a {@link MailboxUpdateSentToNewContactEvent}
-	 * should be attached to the transaction. We should only do this when
-	 * adding a new contact, not when setting up this client for an existing
-	 * contact.
-	 */
-	private void addingContact(Transaction txn, Contact c, boolean attachEvent)
-			throws DbException {
 		// Create a group to share with the contact
 		Group g = getContactGroup(c);
 		db.addGroup(txn, g);
@@ -161,17 +143,13 @@ class MailboxUpdateManagerImpl implements MailboxUpdateManager,
 		clientHelper.setContactId(txn, g.getId(), c.getId());
 		MailboxProperties ownProps =
 				mailboxSettingsManager.getOwnMailboxProperties(txn);
-		MailboxUpdate u;
 		if (ownProps != null) {
 			// We are paired, create and send props to the newly added contact
-			u = createAndSendUpdateWithMailbox(txn, c,
-					ownProps.getServerSupports(), ownProps.getOnion());
+			createAndSendUpdateWithMailbox(txn, c, ownProps.getServerSupports(),
+					ownProps.getOnion());
 		} else {
 			// Not paired, but we still want to get our clientSupports sent
-			u = sendUpdateNoMailbox(txn, c);
-		}
-		if (attachEvent) {
-			txn.attach(new MailboxUpdateSentToNewContactEvent(c.getId(), u));
+			sendUpdateNoMailbox(txn, c);
 		}
 	}
 
@@ -181,103 +159,18 @@ class MailboxUpdateManagerImpl implements MailboxUpdateManager,
 	}
 
 	@Override
-	public void mailboxPaired(Transaction txn, MailboxProperties p)
-			throws DbException {
-		Map<ContactId, MailboxUpdateWithMailbox> localUpdates = new HashMap<>();
+	public void mailboxPaired(Transaction txn, String ownOnion,
+			List<MailboxVersion> serverSupports) throws DbException {
 		for (Contact c : db.getContacts(txn)) {
-			MailboxUpdateWithMailbox u = createAndSendUpdateWithMailbox(txn, c,
-					p.getServerSupports(), p.getOnion());
-			localUpdates.put(c.getId(), u);
-		}
-		txn.attach(new MailboxPairedEvent(p, localUpdates));
-		// Store the list of server-supported versions
-		try {
-			storeSentServerSupports(txn, p.getServerSupports());
-		} catch (FormatException e) {
-			throw new DbException();
+			createAndSendUpdateWithMailbox(txn, c, serverSupports, ownOnion);
 		}
 	}
 
 	@Override
 	public void mailboxUnpaired(Transaction txn) throws DbException {
-		Map<ContactId, MailboxUpdate> localUpdates = new HashMap<>();
 		for (Contact c : db.getContacts(txn)) {
-			MailboxUpdate u = sendUpdateNoMailbox(txn, c);
-			localUpdates.put(c.getId(), u);
+			sendUpdateNoMailbox(txn, c);
 		}
-		txn.attach(new MailboxUnpairedEvent(localUpdates));
-		// Remove the list of server-supported versions
-		try {
-			BdfDictionary meta = BdfDictionary.of(new BdfEntry(
-					GROUP_KEY_SENT_SERVER_SUPPORTS, NULL_VALUE));
-			clientHelper.mergeGroupMetadata(txn, localGroup.getId(), meta);
-		} catch (FormatException e) {
-			throw new DbException();
-		}
-	}
-
-	@Override
-	public void serverSupportedVersionsReceived(Transaction txn,
-			List<MailboxVersion> serverSupports) throws DbException {
-		try {
-			List<MailboxVersion> oldServerSupports =
-					loadSentServerSupports(txn);
-			if (serverSupports.equals(oldServerSupports)) return;
-			storeSentServerSupports(txn, serverSupports);
-			for (Contact c : db.getContacts(txn)) {
-				Group contactGroup = getContactGroup(c);
-				LatestUpdate latest =
-						findLatest(txn, contactGroup.getId(), true);
-				// This method should only be called when we have a mailbox,
-				// in which case we should have sent a local update to every
-				// contact
-				if (latest == null) throw new DbException();
-				BdfList body =
-						clientHelper.getMessageAsList(txn, latest.messageId);
-				MailboxUpdate oldUpdate = parseUpdate(body);
-				if (!oldUpdate.hasMailbox()) throw new DbException();
-				MailboxUpdateWithMailbox newUpdate = updateServerSupports(
-						(MailboxUpdateWithMailbox) oldUpdate, serverSupports);
-				storeMessageReplaceLatest(txn, contactGroup.getId(), newUpdate,
-						latest);
-			}
-		} catch (FormatException e) {
-			throw new DbException();
-		}
-	}
-
-	private void storeSentServerSupports(Transaction txn,
-			List<MailboxVersion> serverSupports)
-			throws DbException, FormatException {
-		BdfDictionary meta = BdfDictionary.of(new BdfEntry(
-				GROUP_KEY_SENT_SERVER_SUPPORTS,
-				encodeSupportsList(serverSupports)));
-		clientHelper.mergeGroupMetadata(txn, localGroup.getId(), meta);
-	}
-
-	private List<MailboxVersion> loadSentServerSupports(Transaction txn)
-			throws DbException, FormatException {
-		BdfDictionary meta = clientHelper.getGroupMetadataAsDictionary(txn,
-				localGroup.getId());
-		BdfList serverSupports =
-				meta.getOptionalList(GROUP_KEY_SENT_SERVER_SUPPORTS);
-		if (serverSupports == null) return emptyList();
-		return clientHelper.parseMailboxVersionList(serverSupports);
-	}
-
-	/**
-	 * Returns a new {@link MailboxUpdateWithMailbox} that updates the list
-	 * of server-supported API versions in the given
-	 * {@link MailboxUpdateWithMailbox}.
-	 */
-	private MailboxUpdateWithMailbox updateServerSupports(
-			MailboxUpdateWithMailbox old, List<MailboxVersion> serverSupports) {
-		MailboxProperties oldProps = old.getMailboxProperties();
-		MailboxProperties newProps = new MailboxProperties(oldProps.getOnion(),
-				oldProps.getAuthToken(), serverSupports,
-				requireNonNull(oldProps.getInboxId()),
-				requireNonNull(oldProps.getOutboxId()));
-		return new MailboxUpdateWithMailbox(old.getClientSupports(), newProps);
 	}
 
 	@Override
@@ -346,19 +239,19 @@ class MailboxUpdateManagerImpl implements MailboxUpdateManager,
 	 * supported Mailbox API version(s). All of which the contact needs to
 	 * communicate with our Mailbox.
 	 */
-	private MailboxUpdateWithMailbox createAndSendUpdateWithMailbox(
-			Transaction txn, Contact c, List<MailboxVersion> serverSupports,
-			String ownOnion) throws DbException {
-		MailboxProperties properties = new MailboxProperties(ownOnion,
+	private void createAndSendUpdateWithMailbox(Transaction txn, Contact c,
+			List<MailboxVersion> serverSupports, String ownOnion)
+			throws DbException {
+		String baseUrl = "http://" + ownOnion + ".onion"; // TODO
+		MailboxProperties properties = new MailboxProperties(baseUrl,
 				new MailboxAuthToken(crypto.generateUniqueId().getBytes()),
 				serverSupports,
 				new MailboxFolderId(crypto.generateUniqueId().getBytes()),
 				new MailboxFolderId(crypto.generateUniqueId().getBytes()));
-		MailboxUpdateWithMailbox u =
+		MailboxUpdate u =
 				new MailboxUpdateWithMailbox(clientSupports, properties);
 		Group g = getContactGroup(c);
 		storeMessageReplaceLatest(txn, g.getId(), u);
-		return u;
 	}
 
 	/**
@@ -367,12 +260,11 @@ class MailboxUpdateManagerImpl implements MailboxUpdateManager,
 	 * Mailbox that they can use. It still includes the list of Mailbox API
 	 * version(s) that we support as a client.
 	 */
-	private MailboxUpdate sendUpdateNoMailbox(Transaction txn, Contact c)
+	private void sendUpdateNoMailbox(Transaction txn, Contact c)
 			throws DbException {
 		Group g = getContactGroup(c);
 		MailboxUpdate u = new MailboxUpdate(clientSupports);
 		storeMessageReplaceLatest(txn, g.getId(), u);
-		return u;
 	}
 
 	@Nullable
@@ -397,27 +289,21 @@ class MailboxUpdateManagerImpl implements MailboxUpdateManager,
 			MailboxUpdate u) throws DbException {
 		try {
 			LatestUpdate latest = findLatest(txn, g, true);
-			storeMessageReplaceLatest(txn, g, u, latest);
+			long version = latest == null ? 1 : latest.version + 1;
+			Message m = clientHelper.createMessage(g, clock.currentTimeMillis(),
+					encodeProperties(version, u));
+			BdfDictionary meta = new BdfDictionary();
+			meta.put(MSG_KEY_VERSION, version);
+			meta.put(MSG_KEY_LOCAL, true);
+			clientHelper.addLocalMessage(txn, m, meta, true, false);
+			if (latest != null) {
+				db.removeMessage(txn, latest.messageId);
+			}
 		} catch (FormatException e) {
 			throw new DbException(e);
 		}
 	}
 
-	private void storeMessageReplaceLatest(Transaction txn, GroupId g,
-			MailboxUpdate u, @Nullable LatestUpdate latest)
-			throws DbException, FormatException {
-		long version = latest == null ? 1 : latest.version + 1;
-		Message m = clientHelper.createMessage(g, clock.currentTimeMillis(),
-				encodeProperties(version, u));
-		BdfDictionary meta = new BdfDictionary();
-		meta.put(MSG_KEY_VERSION, version);
-		meta.put(MSG_KEY_LOCAL, true);
-		clientHelper.addLocalMessage(txn, m, meta, true, false);
-		if (latest != null) {
-			db.removeMessage(txn, latest.messageId);
-		}
-	}
-
 	@Nullable
 	private LatestUpdate findLatest(Transaction txn, GroupId g, boolean local)
 			throws DbException, FormatException {

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxUploadWorker.java

@@ -1,464 +0,0 @@
-package org.briarproject.bramble.mailbox;
-
-import org.briarproject.bramble.api.Cancellable;
-import org.briarproject.bramble.api.connection.ConnectionRegistry;
-import org.briarproject.bramble.api.contact.ContactId;
-import org.briarproject.bramble.api.db.DatabaseComponent;
-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.EventExecutor;
-import org.briarproject.bramble.api.event.EventListener;
-import org.briarproject.bramble.api.lifecycle.IoExecutor;
-import org.briarproject.bramble.api.mailbox.MailboxFolderId;
-import org.briarproject.bramble.api.mailbox.MailboxProperties;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.plugin.event.ContactConnectedEvent;
-import org.briarproject.bramble.api.plugin.event.ContactDisconnectedEvent;
-import org.briarproject.bramble.api.sync.MessageId;
-import org.briarproject.bramble.api.sync.OutgoingSessionRecord;
-import org.briarproject.bramble.api.sync.event.GroupVisibilityUpdatedEvent;
-import org.briarproject.bramble.api.sync.event.MessageSharedEvent;
-import org.briarproject.bramble.api.sync.event.MessageToAckEvent;
-import org.briarproject.bramble.api.system.Clock;
-import org.briarproject.bramble.api.system.TaskScheduler;
-import org.briarproject.bramble.mailbox.ConnectivityChecker.ConnectivityObserver;
-import org.briarproject.bramble.mailbox.MailboxApi.ApiException;
-
-import java.io.File;
-import java.io.IOException;
-import java.util.Collection;
-import java.util.concurrent.Executor;
-import java.util.logging.Logger;
-
-import javax.annotation.Nullable;
-import javax.annotation.concurrent.GuardedBy;
-import javax.annotation.concurrent.ThreadSafe;
-
-import static java.lang.Boolean.TRUE;
-import static java.util.concurrent.TimeUnit.MILLISECONDS;
-import static java.util.concurrent.TimeUnit.MINUTES;
-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.mailbox.MailboxConstants.MAX_LATENCY;
-import static org.briarproject.bramble.api.sync.Group.Visibility.SHARED;
-import static org.briarproject.bramble.util.IoUtils.delete;
-import static org.briarproject.bramble.util.LogUtils.logException;
-
-@ThreadSafe
-@NotNullByDefault
-class MailboxUploadWorker implements MailboxWorker, ConnectivityObserver,
-		EventListener {
-
-	/**
-	 * When the worker is started it checks for data to send. If data is ready
-	 * to send, the worker waits for a connectivity check, then writes and
-	 * uploads a file and checks again for data to send.
-	 * <p>
-	 * If data is due to be sent at some time in the future, the worker
-	 * schedules a wakeup for that time and also listens for events indicating
-	 * that new data may be ready to send.
-	 * <p>
-	 * If there's no data to send, the worker listens for events indicating
-	 * that new data may be ready to send.
-	 * <p>
-	 * Whenever we're directly connected to the contact, the worker doesn't
-	 * check for data to send or start connectivity checks until the contact
-	 * disconnects. However, if the worker has already started writing and
-	 * uploading a file when the contact connects, the worker will finish the
-	 * upload.
-	 */
-	private enum State {
-		CREATED,
-		CONNECTED_TO_CONTACT,
-		CHECKING_FOR_DATA,
-		WAITING_FOR_DATA,
-		CONNECTIVITY_CHECK,
-		WRITING_UPLOADING,
-		DESTROYED
-	}
-
-	private static final Logger LOG =
-			getLogger(MailboxUploadWorker.class.getName());
-
-	/**
-	 * When we're waiting for data to send and an event indicates that new data
-	 * may have become available, wait this long before checking the DB. This
-	 * should help to avoid creating lots of small files when several acks or
-	 * messages become available to send in a short period (eg when reading a
-	 * file downloaded from a mailbox).
-	 * <p>
-	 * Package access for testing.
-	 */
-	static final long CHECK_DELAY_MS = 5_000;
-
-	/**
-	 * How long to wait before retrying when an exception occurs while writing
-	 * a file.
-	 * <p>
-	 * Package access for testing.
-	 */
-	static final long RETRY_DELAY_MS = MINUTES.toMillis(1);
-
-	private final Executor ioExecutor;
-	private final DatabaseComponent db;
-	private final Clock clock;
-	private final TaskScheduler taskScheduler;
-	private final EventBus eventBus;
-	private final ConnectionRegistry connectionRegistry;
-	private final ConnectivityChecker connectivityChecker;
-	private final MailboxApiCaller mailboxApiCaller;
-	private final MailboxApi mailboxApi;
-	private final MailboxFileManager mailboxFileManager;
-	private final MailboxProperties mailboxProperties;
-	private final MailboxFolderId folderId;
-	private final ContactId contactId;
-
-	private final Object lock = new Object();
-
-	@GuardedBy("lock")
-	private State state = State.CREATED;
-
-	@GuardedBy("lock")
-	@Nullable
-	private Cancellable wakeupTask = null, checkTask = null, apiCall = null;
-
-	@GuardedBy("lock")
-	@Nullable
-	private File file = null;
-
-	MailboxUploadWorker(@IoExecutor Executor ioExecutor,
-			DatabaseComponent db,
-			Clock clock,
-			TaskScheduler taskScheduler,
-			EventBus eventBus,
-			ConnectionRegistry connectionRegistry,
-			ConnectivityChecker connectivityChecker,
-			MailboxApiCaller mailboxApiCaller,
-			MailboxApi mailboxApi,
-			MailboxFileManager mailboxFileManager,
-			MailboxProperties mailboxProperties,
-			MailboxFolderId folderId,
-			ContactId contactId) {
-		this.ioExecutor = ioExecutor;
-		this.db = db;
-		this.clock = clock;
-		this.taskScheduler = taskScheduler;
-		this.eventBus = eventBus;
-		this.connectionRegistry = connectionRegistry;
-		this.connectivityChecker = connectivityChecker;
-		this.mailboxApiCaller = mailboxApiCaller;
-		this.mailboxApi = mailboxApi;
-		this.mailboxFileManager = mailboxFileManager;
-		this.mailboxProperties = mailboxProperties;
-		this.folderId = folderId;
-		this.contactId = contactId;
-	}
-
-	@Override
-	public void start() {
-		LOG.info("Started");
-		synchronized (lock) {
-			// Don't allow the worker to be reused
-			if (state != State.CREATED) return;
-			state = State.CHECKING_FOR_DATA;
-		}
-		ioExecutor.execute(this::checkForDataToSend);
-	}
-
-	@Override
-	public void destroy() {
-		LOG.info("Destroyed");
-		Cancellable wakeupTask, checkTask, apiCall;
-		File file;
-		synchronized (lock) {
-			state = State.DESTROYED;
-			wakeupTask = this.wakeupTask;
-			this.wakeupTask = null;
-			checkTask = this.checkTask;
-			this.checkTask = null;
-			apiCall = this.apiCall;
-			this.apiCall = null;
-			file = this.file;
-			this.file = null;
-		}
-		if (wakeupTask != null) wakeupTask.cancel();
-		if (checkTask != null) checkTask.cancel();
-		if (apiCall != null) apiCall.cancel();
-		if (file != null) delete(file);
-		connectivityChecker.removeObserver(this);
-		eventBus.removeListener(this);
-	}
-
-	@IoExecutor
-	private void checkForDataToSend() {
-		synchronized (lock) {
-			checkTask = null;
-			if (state != State.CHECKING_FOR_DATA) return;
-			// Check whether we're directly connected to the contact. Calling
-			// this while holding the lock isn't ideal, but it avoids races
-			if (connectionRegistry.isConnected(contactId)) {
-				state = State.CONNECTED_TO_CONTACT;
-				return;
-			}
-		}
-		LOG.info("Checking for data to send");
-		try {
-			db.transaction(true, txn -> {
-				long nextSendTime;
-				if (db.containsAcksToSend(txn, contactId)) {
-					nextSendTime = 0L;
-				} else {
-					nextSendTime = db.getNextSendTime(txn, contactId,
-							MAX_LATENCY);
-				}
-				// Handle the result on the event executor to avoid races with
-				// incoming events
-				txn.attach(() -> handleNextSendTime(nextSendTime));
-			});
-		} catch (DbException e) {
-			logException(LOG, WARNING, e);
-		}
-	}
-
-	@EventExecutor
-	private void handleNextSendTime(long nextSendTime) {
-		if (nextSendTime == Long.MAX_VALUE) {
-			// Nothing is sendable now or due to be sent in the future. Wait
-			// for an event indicating that new data may be ready to send
-			waitForDataToSend();
-		} else {
-			// Work out the delay until data's ready to send (may be negative)
-			long delay = nextSendTime - clock.currentTimeMillis();
-			if (delay > 0) {
-				// Schedule a wakeup when data will be ready to send. If an
-				// event is received in the meantime indicating that new data
-				// may be ready to send, we'll cancel the wakeup
-				scheduleWakeup(delay);
-			} else {
-				// Data is ready to send now
-				checkConnectivity();
-			}
-		}
-	}
-
-	@EventExecutor
-	private void waitForDataToSend() {
-		synchronized (lock) {
-			if (state != State.CHECKING_FOR_DATA) return;
-			state = State.WAITING_FOR_DATA;
-			LOG.info("Waiting for data to send");
-		}
-	}
-
-	@EventExecutor
-	private void scheduleWakeup(long delay) {
-		synchronized (lock) {
-			if (state != State.CHECKING_FOR_DATA) return;
-			state = State.WAITING_FOR_DATA;
-			if (LOG.isLoggable(INFO)) {
-				LOG.info("Scheduling wakeup in " + delay + " ms");
-			}
-			wakeupTask = taskScheduler.schedule(this::wakeUp, ioExecutor,
-					delay, MILLISECONDS);
-		}
-	}
-
-	@IoExecutor
-	private void wakeUp() {
-		LOG.info("Woke up");
-		synchronized (lock) {
-			wakeupTask = null;
-			if (state != State.WAITING_FOR_DATA) return;
-			state = State.CHECKING_FOR_DATA;
-		}
-		checkForDataToSend();
-	}
-
-	@EventExecutor
-	private void checkConnectivity() {
-		synchronized (lock) {
-			if (state != State.CHECKING_FOR_DATA) return;
-			state = State.CONNECTIVITY_CHECK;
-		}
-		LOG.info("Checking connectivity");
-		// Avoid leaking observer in case destroy() is called concurrently
-		// before observer is added
-		connectivityChecker.checkConnectivity(mailboxProperties, this);
-		boolean destroyed;
-		synchronized (lock) {
-			destroyed = state == State.DESTROYED;
-		}
-		if (destroyed) connectivityChecker.removeObserver(this);
-	}
-
-	@Override
-	public void onConnectivityCheckSucceeded() {
-		LOG.info("Connectivity check succeeded");
-		synchronized (lock) {
-			if (state != State.CONNECTIVITY_CHECK) return;
-			state = State.WRITING_UPLOADING;
-		}
-		ioExecutor.execute(this::writeAndUploadFile);
-	}
-
-	@IoExecutor
-	private void writeAndUploadFile() {
-		synchronized (lock) {
-			if (state != State.WRITING_UPLOADING) return;
-		}
-		OutgoingSessionRecord sessionRecord = new OutgoingSessionRecord();
-		File file;
-		try {
-			file = mailboxFileManager.createAndWriteTempFileForUpload(
-					contactId, sessionRecord);
-		} catch (IOException e) {
-			logException(LOG, WARNING, e);
-			// Try again after a delay
-			synchronized (lock) {
-				if (state != State.WRITING_UPLOADING) return;
-				state = State.CHECKING_FOR_DATA;
-				checkTask = taskScheduler.schedule(this::checkForDataToSend,
-						ioExecutor, RETRY_DELAY_MS, MILLISECONDS);
-			}
-			return;
-		}
-		boolean deleteFile = false;
-		synchronized (lock) {
-			if (state == State.WRITING_UPLOADING) {
-				this.file = file;
-				apiCall = mailboxApiCaller.retryWithBackoff(
-						new SimpleApiCall(() -> apiCallUploadFile(file,
-								sessionRecord)));
-			} else {
-				deleteFile = true;
-			}
-		}
-		if (deleteFile) delete(file);
-	}
-
-	@IoExecutor
-	private void apiCallUploadFile(File file,
-			OutgoingSessionRecord sessionRecord)
-			throws IOException, ApiException {
-		synchronized (lock) {
-			if (state != State.WRITING_UPLOADING) return;
-		}
-		LOG.info("Uploading file");
-		mailboxApi.addFile(mailboxProperties, folderId, file);
-		markMessagesSentOrAcked(sessionRecord);
-		delete(file);
-		synchronized (lock) {
-			if (state != State.WRITING_UPLOADING) return;
-			state = State.CHECKING_FOR_DATA;
-			apiCall = null;
-			this.file = null;
-		}
-		checkForDataToSend();
-	}
-
-	private void markMessagesSentOrAcked(OutgoingSessionRecord sessionRecord) {
-		Collection<MessageId> acked = sessionRecord.getAckedIds();
-		Collection<MessageId> sent = sessionRecord.getSentIds();
-		try {
-			db.transaction(false, txn -> {
-				if (!acked.isEmpty()) {
-					db.setAckSent(txn, contactId, acked);
-				}
-				if (!sent.isEmpty()) {
-					db.setMessagesSent(txn, contactId, sent, MAX_LATENCY);
-				}
-			});
-		} catch (DbException e) {
-			logException(LOG, WARNING, e);
-		}
-	}
-
-	@Override
-	public void eventOccurred(Event e) {
-		if (e instanceof MessageToAckEvent) {
-			MessageToAckEvent m = (MessageToAckEvent) e;
-			if (m.getContactId().equals(contactId)) {
-				LOG.info("Message to ack");
-				onDataToSend();
-			}
-		} else if (e instanceof MessageSharedEvent) {
-			MessageSharedEvent m = (MessageSharedEvent) e;
-			// If the contact is present in the map (ie the value is not null)
-			// and the value is true, the message's group is shared with the
-			// contact and therefore the message may now be sendable
-			if (m.getGroupVisibility().get(contactId) == TRUE) {
-				LOG.info("Message shared");
-				onDataToSend();
-			}
-		} else if (e instanceof GroupVisibilityUpdatedEvent) {
-			GroupVisibilityUpdatedEvent g = (GroupVisibilityUpdatedEvent) e;
-			if (g.getVisibility() == SHARED &&
-					g.getAffectedContacts().contains(contactId)) {
-				LOG.info("Group shared");
-				onDataToSend();
-			}
-		} else if (e instanceof ContactConnectedEvent) {
-			ContactConnectedEvent c = (ContactConnectedEvent) e;
-			if (c.getContactId().equals(contactId)) {
-				LOG.info("Contact connected");
-				onContactConnected();
-			}
-		} else if (e instanceof ContactDisconnectedEvent) {
-			ContactDisconnectedEvent c = (ContactDisconnectedEvent) e;
-			if (c.getContactId().equals(contactId)) {
-				LOG.info("Contact disconnected");
-				onContactDisconnected();
-			}
-		}
-	}
-
-	@EventExecutor
-	private void onDataToSend() {
-		Cancellable wakeupTask;
-		synchronized (lock) {
-			if (state != State.WAITING_FOR_DATA) return;
-			state = State.CHECKING_FOR_DATA;
-			wakeupTask = this.wakeupTask;
-			this.wakeupTask = null;
-			// Delay the check to avoid creating lots of small files
-			checkTask = taskScheduler.schedule(this::checkForDataToSend,
-					ioExecutor, CHECK_DELAY_MS, MILLISECONDS);
-		}
-		// If we had scheduled a wakeup when data was due to be sent, cancel it
-		if (wakeupTask != null) wakeupTask.cancel();
-	}
-
-	@EventExecutor
-	private void onContactConnected() {
-		Cancellable wakeupTask = null, checkTask = null;
-		synchronized (lock) {
-			if (state == State.DESTROYED) return;
-			// If we're checking for data to send, waiting for data to send,
-			// or checking connectivity then wait until we disconnect from
-			// the contact before proceeding. If we're writing or uploading
-			// a file then continue
-			if (state == State.CHECKING_FOR_DATA ||
-					state == State.WAITING_FOR_DATA ||
-					state == State.CONNECTIVITY_CHECK) {
-				state = State.CONNECTED_TO_CONTACT;
-				wakeupTask = this.wakeupTask;
-				this.wakeupTask = null;
-				checkTask = this.checkTask;
-				this.checkTask = null;
-			}
-		}
-		if (wakeupTask != null) wakeupTask.cancel();
-		if (checkTask != null) checkTask.cancel();
-	}
-
-	@EventExecutor
-	private void onContactDisconnected() {
-		synchronized (lock) {
-			if (state != State.CONNECTED_TO_CONTACT) return;
-			state = State.CHECKING_FOR_DATA;
-		}
-		ioExecutor.execute(this::checkForDataToSend);
-	}
-}

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxWorkerFactory.java

@@ -1,31 +0,0 @@
-package org.briarproject.bramble.mailbox;
-
-import org.briarproject.bramble.api.contact.ContactId;
-import org.briarproject.bramble.api.mailbox.MailboxFolderId;
-import org.briarproject.bramble.api.mailbox.MailboxProperties;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-
-import javax.annotation.concurrent.ThreadSafe;
-
-@ThreadSafe
-@NotNullByDefault
-interface MailboxWorkerFactory {
-
-	MailboxWorker createUploadWorker(ConnectivityChecker connectivityChecker,
-			MailboxProperties properties, MailboxFolderId folderId,
-			ContactId contactId);
-
-	MailboxWorker createDownloadWorkerForContactMailbox(
-			ConnectivityChecker connectivityChecker,
-			TorReachabilityMonitor reachabilityMonitor,
-			MailboxProperties properties);
-
-	MailboxWorker createDownloadWorkerForOwnMailbox(
-			ConnectivityChecker connectivityChecker,
-			TorReachabilityMonitor reachabilityMonitor,
-			MailboxProperties properties);
-
-	MailboxWorker createContactListWorkerForOwnMailbox(
-			ConnectivityChecker connectivityChecker,
-			MailboxProperties properties);
-}

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxWorkerFactoryImpl.java

@@ -1,101 +0,0 @@
-package org.briarproject.bramble.mailbox;
-
-import org.briarproject.bramble.api.connection.ConnectionRegistry;
-import org.briarproject.bramble.api.contact.ContactId;
-import org.briarproject.bramble.api.db.DatabaseComponent;
-import org.briarproject.bramble.api.event.EventBus;
-import org.briarproject.bramble.api.lifecycle.IoExecutor;
-import org.briarproject.bramble.api.mailbox.MailboxFolderId;
-import org.briarproject.bramble.api.mailbox.MailboxProperties;
-import org.briarproject.bramble.api.mailbox.MailboxUpdateManager;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.system.Clock;
-import org.briarproject.bramble.api.system.TaskScheduler;
-
-import java.util.concurrent.Executor;
-
-import javax.annotation.concurrent.Immutable;
-import javax.inject.Inject;
-
-@Immutable
-@NotNullByDefault
-class MailboxWorkerFactoryImpl implements MailboxWorkerFactory {
-
-	private final Executor ioExecutor;
-	private final DatabaseComponent db;
-	private final Clock clock;
-	private final TaskScheduler taskScheduler;
-	private final EventBus eventBus;
-	private final ConnectionRegistry connectionRegistry;
-	private final MailboxApiCaller mailboxApiCaller;
-	private final MailboxApi mailboxApi;
-	private final MailboxFileManager mailboxFileManager;
-	private final MailboxUpdateManager mailboxUpdateManager;
-
-	@Inject
-	MailboxWorkerFactoryImpl(@IoExecutor Executor ioExecutor,
-			DatabaseComponent db,
-			Clock clock,
-			TaskScheduler taskScheduler,
-			EventBus eventBus,
-			ConnectionRegistry connectionRegistry,
-			MailboxApiCaller mailboxApiCaller,
-			MailboxApi mailboxApi,
-			MailboxFileManager mailboxFileManager,
-			MailboxUpdateManager mailboxUpdateManager) {
-		this.ioExecutor = ioExecutor;
-		this.db = db;
-		this.clock = clock;
-		this.taskScheduler = taskScheduler;
-		this.eventBus = eventBus;
-		this.connectionRegistry = connectionRegistry;
-		this.mailboxApiCaller = mailboxApiCaller;
-		this.mailboxApi = mailboxApi;
-		this.mailboxFileManager = mailboxFileManager;
-		this.mailboxUpdateManager = mailboxUpdateManager;
-	}
-
-	@Override
-	public MailboxWorker createUploadWorker(
-			ConnectivityChecker connectivityChecker,
-			MailboxProperties properties, MailboxFolderId folderId,
-			ContactId contactId) {
-		MailboxUploadWorker worker = new MailboxUploadWorker(ioExecutor, db,
-				clock, taskScheduler, eventBus, connectionRegistry,
-				connectivityChecker, mailboxApiCaller, mailboxApi,
-				mailboxFileManager, properties, folderId, contactId);
-		eventBus.addListener(worker);
-		return worker;
-	}
-
-	@Override
-	public MailboxWorker createDownloadWorkerForContactMailbox(
-			ConnectivityChecker connectivityChecker,
-			TorReachabilityMonitor reachabilityMonitor,
-			MailboxProperties properties) {
-		return new ContactMailboxDownloadWorker(connectivityChecker,
-				reachabilityMonitor, mailboxApiCaller, mailboxApi,
-				mailboxFileManager, properties);
-	}
-
-	@Override
-	public MailboxWorker createDownloadWorkerForOwnMailbox(
-			ConnectivityChecker connectivityChecker,
-			TorReachabilityMonitor reachabilityMonitor,
-			MailboxProperties properties) {
-		return new OwnMailboxDownloadWorker(connectivityChecker,
-				reachabilityMonitor, mailboxApiCaller, mailboxApi,
-				mailboxFileManager, properties);
-	}
-
-	@Override
-	public MailboxWorker createContactListWorkerForOwnMailbox(
-			ConnectivityChecker connectivityChecker,
-			MailboxProperties properties) {
-		OwnMailboxContactListWorker worker = new OwnMailboxContactListWorker(
-				ioExecutor, db, eventBus, connectivityChecker, mailboxApiCaller,
-				mailboxApi, mailboxUpdateManager, properties);
-		eventBus.addListener(worker);
-		return worker;
-	}
-}

bramble-core/src/main/java/org/briarproject/bramble/mailbox/OwnMailboxClient.java

@@ -1,222 +0,0 @@
-package org.briarproject.bramble.mailbox;
-
-import org.briarproject.bramble.api.Cancellable;
-import org.briarproject.bramble.api.contact.ContactId;
-import org.briarproject.bramble.api.lifecycle.IoExecutor;
-import org.briarproject.bramble.api.mailbox.MailboxFolderId;
-import org.briarproject.bramble.api.mailbox.MailboxProperties;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.system.TaskScheduler;
-import org.briarproject.bramble.mailbox.ConnectivityChecker.ConnectivityObserver;
-
-import java.util.ArrayList;
-import java.util.HashMap;
-import java.util.HashSet;
-import java.util.List;
-import java.util.Map;
-import java.util.Set;
-import java.util.concurrent.Executor;
-import java.util.logging.Logger;
-
-import javax.annotation.Nullable;
-import javax.annotation.concurrent.GuardedBy;
-import javax.annotation.concurrent.ThreadSafe;
-
-import static java.util.concurrent.TimeUnit.HOURS;
-import static java.util.concurrent.TimeUnit.MILLISECONDS;
-import static java.util.logging.Logger.getLogger;
-
-@ThreadSafe
-@NotNullByDefault
-class OwnMailboxClient implements MailboxClient, ConnectivityObserver {
-
-	/**
-	 * How often to check our own mailbox's connectivity.
-	 * <p>
-	 * Package access for testing.
-	 */
-	static final long CONNECTIVITY_CHECK_INTERVAL_MS = HOURS.toMillis(1);
-
-	private static final Logger LOG =
-			getLogger(OwnMailboxClient.class.getName());
-
-	private final MailboxWorkerFactory workerFactory;
-	private final ConnectivityChecker connectivityChecker;
-	private final TorReachabilityMonitor reachabilityMonitor;
-	private final TaskScheduler taskScheduler;
-	private final Executor ioExecutor;
-	private final MailboxProperties properties;
-	private final MailboxWorker contactListWorker;
-	private final Object lock = new Object();
-
-	/**
-	 * Upload workers: one worker per contact assigned for upload.
-	 */
-	@GuardedBy("lock")
-	private final Map<ContactId, MailboxWorker> uploadWorkers = new HashMap<>();
-
-	/**
-	 * Download worker: shared between all contacts assigned for download.
-	 * Null if no contacts are assigned for download.
-	 */
-	@GuardedBy("lock")
-	@Nullable
-	private MailboxWorker downloadWorker = null;
-
-	/**
-	 * IDs of contacts assigned for download, so that we know when to
-	 * create/destroy the download worker.
-	 */
-	@GuardedBy("lock")
-	private final Set<ContactId> assignedForDownload = new HashSet<>();
-
-	/**
-	 * Scheduled task for periodically checking whether the mailbox is
-	 * reachable.
-	 */
-	@GuardedBy("lock")
-	@Nullable
-	private Cancellable connectivityTask = null;
-
-	@GuardedBy("lock")
-	private boolean destroyed = false;
-
-	OwnMailboxClient(MailboxWorkerFactory workerFactory,
-			ConnectivityChecker connectivityChecker,
-			TorReachabilityMonitor reachabilityMonitor,
-			TaskScheduler taskScheduler,
-			@IoExecutor Executor ioExecutor,
-			MailboxProperties properties) {
-		if (!properties.isOwner()) throw new IllegalArgumentException();
-		this.workerFactory = workerFactory;
-		this.connectivityChecker = connectivityChecker;
-		this.reachabilityMonitor = reachabilityMonitor;
-		this.taskScheduler = taskScheduler;
-		this.ioExecutor = ioExecutor;
-		this.properties = properties;
-		contactListWorker = workerFactory.createContactListWorkerForOwnMailbox(
-				connectivityChecker, properties);
-	}
-
-	@Override
-	public void start() {
-		LOG.info("Started");
-		checkConnectivity();
-		contactListWorker.start();
-	}
-
-	@Override
-	public void destroy() {
-		LOG.info("Destroyed");
-		List<MailboxWorker> uploadWorkers;
-		MailboxWorker downloadWorker;
-		Cancellable connectivityTask;
-		synchronized (lock) {
-			uploadWorkers = new ArrayList<>(this.uploadWorkers.values());
-			this.uploadWorkers.clear();
-			downloadWorker = this.downloadWorker;
-			this.downloadWorker = null;
-			connectivityTask = this.connectivityTask;
-			this.connectivityTask = null;
-			destroyed = true;
-		}
-		// Destroy the workers (with apologies to Mr Marx and Mr Engels)
-		for (MailboxWorker worker : uploadWorkers) worker.destroy();
-		if (downloadWorker != null) downloadWorker.destroy();
-		// If a connectivity check is scheduled, cancel it
-		if (connectivityTask != null) connectivityTask.cancel();
-		contactListWorker.destroy();
-		// The connectivity checker belongs to the client, so it should be
-		// destroyed. The Tor reachability monitor is shared between clients,
-		// so it should not be destroyed
-		connectivityChecker.destroy();
-	}
-
-	@Override
-	public void assignContactForUpload(ContactId contactId,
-			MailboxProperties properties, MailboxFolderId folderId) {
-		LOG.info("Contact assigned for upload");
-		if (!properties.isOwner()) throw new IllegalArgumentException();
-		MailboxWorker uploadWorker = workerFactory.createUploadWorker(
-				connectivityChecker, properties, folderId, contactId);
-		synchronized (lock) {
-			MailboxWorker old = uploadWorkers.put(contactId, uploadWorker);
-			if (old != null) throw new IllegalStateException();
-		}
-		uploadWorker.start();
-	}
-
-	@Override
-	public void deassignContactForUpload(ContactId contactId) {
-		LOG.info("Contact deassigned for upload");
-		MailboxWorker uploadWorker;
-		synchronized (lock) {
-			uploadWorker = uploadWorkers.remove(contactId);
-		}
-		if (uploadWorker != null) uploadWorker.destroy();
-	}
-
-	@Override
-	public void assignContactForDownload(ContactId contactId,
-			MailboxProperties properties, MailboxFolderId folderId) {
-		LOG.info("Contact assigned for download");
-		if (!properties.isOwner()) throw new IllegalArgumentException();
-		// Create a download worker if we don't already have one. The worker
-		// will use the API to discover which folders have files to download,
-		// so it doesn't need to track the set of assigned contacts
-		MailboxWorker toStart = null;
-		synchronized (lock) {
-			if (!assignedForDownload.add(contactId)) {
-				throw new IllegalStateException();
-			}
-			if (downloadWorker == null) {
-				toStart = workerFactory.createDownloadWorkerForOwnMailbox(
-						connectivityChecker, reachabilityMonitor, properties);
-				downloadWorker = toStart;
-			}
-		}
-		if (toStart != null) toStart.start();
-	}
-
-	@Override
-	public void deassignContactForDownload(ContactId contactId) {
-		LOG.info("Contact deassigned for download");
-		// If there are no more contacts assigned for download, destroy the
-		// download worker
-		MailboxWorker toDestroy = null;
-		synchronized (lock) {
-			if (!assignedForDownload.remove(contactId)) {
-				throw new IllegalStateException();
-			}
-			if (assignedForDownload.isEmpty()) {
-				toDestroy = downloadWorker;
-				downloadWorker = null;
-			}
-		}
-		if (toDestroy != null) toDestroy.destroy();
-	}
-
-	private void checkConnectivity() {
-		synchronized (lock) {
-			if (destroyed) return;
-			connectivityTask = null;
-		}
-		connectivityChecker.checkConnectivity(properties, this);
-		// Avoid leaking observer in case destroy() is called concurrently
-		// before observer is added
-		boolean removeObserver;
-		synchronized (lock) {
-			removeObserver = destroyed;
-		}
-		if (removeObserver) connectivityChecker.removeObserver(this);
-	}
-
-	@Override
-	public void onConnectivityCheckSucceeded() {
-		synchronized (lock) {
-			if (destroyed) return;
-			connectivityTask = taskScheduler.schedule(this::checkConnectivity,
-					ioExecutor, CONNECTIVITY_CHECK_INTERVAL_MS, MILLISECONDS);
-		}
-	}
-}

bramble-core/src/main/java/org/briarproject/bramble/mailbox/OwnMailboxConnectivityChecker.java

@@ -4,17 +4,14 @@ import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.TransactionManager;
 import org.briarproject.bramble.api.mailbox.MailboxProperties;
 import org.briarproject.bramble.api.mailbox.MailboxSettingsManager;
-import org.briarproject.bramble.api.mailbox.MailboxVersion;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.mailbox.MailboxApi.ApiException;
 
 import java.io.IOException;
-import java.util.List;
 import java.util.logging.Logger;
 
 import javax.annotation.concurrent.ThreadSafe;
-import javax.inject.Inject;
 
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
@@ -31,7 +28,6 @@ class OwnMailboxConnectivityChecker extends ConnectivityCheckerImpl {
 	private final TransactionManager db;
 	private final MailboxSettingsManager mailboxSettingsManager;
 
-	@Inject
 	OwnMailboxConnectivityChecker(Clock clock,
 			MailboxApiCaller mailboxApiCaller,
 			MailboxApi mailboxApi,
@@ -59,13 +55,11 @@ class OwnMailboxConnectivityChecker extends ConnectivityCheckerImpl {
 	private boolean checkConnectivityAndStoreResult(
 			MailboxProperties properties) throws DbException {
 		try {
-			LOG.info("Checking whether own mailbox is reachable");
-			List<MailboxVersion> serverSupports =
-					mailboxApi.getServerSupports(properties);
+			if (!mailboxApi.checkStatus(properties)) throw new ApiException();
 			LOG.info("Own mailbox is reachable");
 			long now = clock.currentTimeMillis();
 			db.transaction(false, txn -> mailboxSettingsManager
-					.recordSuccessfulConnection(txn, now, serverSupports));
+					.recordSuccessfulConnection(txn, now));
 			// Call the observers and cache the result
 			onConnectivityCheckSucceeded(now);
 			return false; // Don't retry

bramble-core/src/main/java/org/briarproject/bramble/mailbox/OwnMailboxContactListWorker.java

@@ -1,369 +0,0 @@
-package org.briarproject.bramble.mailbox;
-
-import org.briarproject.bramble.api.Cancellable;
-import org.briarproject.bramble.api.contact.Contact;
-import org.briarproject.bramble.api.contact.ContactId;
-import org.briarproject.bramble.api.contact.event.ContactAddedEvent;
-import org.briarproject.bramble.api.contact.event.ContactRemovedEvent;
-import org.briarproject.bramble.api.db.DatabaseComponent;
-import org.briarproject.bramble.api.db.DbException;
-import org.briarproject.bramble.api.db.NoSuchContactException;
-import org.briarproject.bramble.api.event.Event;
-import org.briarproject.bramble.api.event.EventBus;
-import org.briarproject.bramble.api.event.EventExecutor;
-import org.briarproject.bramble.api.event.EventListener;
-import org.briarproject.bramble.api.lifecycle.IoExecutor;
-import org.briarproject.bramble.api.mailbox.MailboxProperties;
-import org.briarproject.bramble.api.mailbox.MailboxUpdate;
-import org.briarproject.bramble.api.mailbox.MailboxUpdateManager;
-import org.briarproject.bramble.api.mailbox.MailboxUpdateWithMailbox;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.mailbox.ConnectivityChecker.ConnectivityObserver;
-import org.briarproject.bramble.mailbox.MailboxApi.ApiException;
-import org.briarproject.bramble.mailbox.MailboxApi.MailboxContact;
-import org.briarproject.bramble.mailbox.MailboxApi.TolerableFailureException;
-
-import java.io.IOException;
-import java.util.Collection;
-import java.util.HashSet;
-import java.util.LinkedList;
-import java.util.Queue;
-import java.util.Set;
-import java.util.concurrent.Executor;
-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.nullsafety.NullSafety.requireNonNull;
-import static org.briarproject.bramble.util.LogUtils.logException;
-
-@ThreadSafe
-@NotNullByDefault
-class OwnMailboxContactListWorker
-		implements MailboxWorker, ConnectivityObserver, EventListener {
-
-	/**
-	 * When the worker is started it waits for a connectivity check, then
-	 * fetches the remote contact list and compares it to the local contact
-	 * list.
-	 * <p>
-	 * Any contacts that are missing from the remote list are added to the
-	 * mailbox's contact list, while any contacts that are missing from the
-	 * local list are removed from the mailbox's contact list.
-	 * <p>
-	 * Once the remote contact list has been brought up to date, the worker
-	 * waits for events indicating that contacts have been added or removed.
-	 * Each time an event is received, the worker updates the mailbox's
-	 * contact list and then goes back to waiting.
-	 */
-	private enum State {
-		CREATED,
-		CONNECTIVITY_CHECK,
-		FETCHING_CONTACT_LIST,
-		UPDATING_CONTACT_LIST,
-		WAITING_FOR_CHANGES,
-		DESTROYED
-	}
-
-	private static final Logger LOG =
-			getLogger(OwnMailboxContactListWorker.class.getName());
-
-	private final Executor ioExecutor;
-	private final DatabaseComponent db;
-	private final EventBus eventBus;
-	private final ConnectivityChecker connectivityChecker;
-	private final MailboxApiCaller mailboxApiCaller;
-	private final MailboxApi mailboxApi;
-	private final MailboxUpdateManager mailboxUpdateManager;
-	private final MailboxProperties mailboxProperties;
-	private final Object lock = new Object();
-
-	@GuardedBy("lock")
-	private State state = State.CREATED;
-
-	@GuardedBy("lock")
-	@Nullable
-	private Cancellable apiCall = null;
-
-	/**
-	 * A queue of updates waiting to be applied to the remote contact list.
-	 */
-	@GuardedBy("lock")
-	private final Queue<Update> updates = new LinkedList<>();
-
-	OwnMailboxContactListWorker(@IoExecutor Executor ioExecutor,
-			DatabaseComponent db,
-			EventBus eventBus,
-			ConnectivityChecker connectivityChecker,
-			MailboxApiCaller mailboxApiCaller,
-			MailboxApi mailboxApi,
-			MailboxUpdateManager mailboxUpdateManager,
-			MailboxProperties mailboxProperties) {
-		if (!mailboxProperties.isOwner()) throw new IllegalArgumentException();
-		this.ioExecutor = ioExecutor;
-		this.db = db;
-		this.connectivityChecker = connectivityChecker;
-		this.mailboxApiCaller = mailboxApiCaller;
-		this.mailboxApi = mailboxApi;
-		this.mailboxUpdateManager = mailboxUpdateManager;
-		this.mailboxProperties = mailboxProperties;
-		this.eventBus = eventBus;
-	}
-
-	@Override
-	public void start() {
-		LOG.info("Started");
-		synchronized (lock) {
-			if (state != State.CREATED) return;
-			state = State.CONNECTIVITY_CHECK;
-		}
-		// Avoid leaking observer in case destroy() is called concurrently
-		// before observer is added
-		connectivityChecker.checkConnectivity(mailboxProperties, this);
-		boolean destroyed;
-		synchronized (lock) {
-			destroyed = state == State.DESTROYED;
-		}
-		if (destroyed) connectivityChecker.removeObserver(this);
-	}
-
-	@Override
-	public void destroy() {
-		LOG.info("Destroyed");
-		Cancellable apiCall;
-		synchronized (lock) {
-			state = State.DESTROYED;
-			apiCall = this.apiCall;
-			this.apiCall = null;
-		}
-		if (apiCall != null) apiCall.cancel();
-		connectivityChecker.removeObserver(this);
-		eventBus.removeListener(this);
-	}
-
-	@Override
-	public void onConnectivityCheckSucceeded() {
-		LOG.info("Connectivity check succeeded");
-		synchronized (lock) {
-			if (state != State.CONNECTIVITY_CHECK) return;
-			state = State.FETCHING_CONTACT_LIST;
-			apiCall = mailboxApiCaller.retryWithBackoff(
-					new SimpleApiCall(this::apiCallFetchContactList));
-		}
-	}
-
-	@IoExecutor
-	private void apiCallFetchContactList() throws IOException, ApiException {
-		synchronized (lock) {
-			if (state != State.FETCHING_CONTACT_LIST) return;
-		}
-		LOG.info("Fetching remote contact list");
-		Collection<ContactId> remote =
-				mailboxApi.getContacts(mailboxProperties);
-		ioExecutor.execute(() -> loadLocalContactList(remote));
-	}
-
-	@IoExecutor
-	private void loadLocalContactList(Collection<ContactId> remote) {
-		synchronized (lock) {
-			if (state != State.FETCHING_CONTACT_LIST) return;
-			apiCall = null;
-		}
-		LOG.info("Loading local contact list");
-		try {
-			db.transaction(true, txn -> {
-				Collection<Contact> local = db.getContacts(txn);
-				// Handle the result on the event executor to avoid races with
-				// incoming events
-				txn.attach(() -> reconcileContactLists(local, remote));
-			});
-		} catch (DbException e) {
-			logException(LOG, WARNING, e);
-		}
-	}
-
-	@EventExecutor
-	private void reconcileContactLists(Collection<Contact> local,
-			Collection<ContactId> remote) {
-		Set<ContactId> localIds = new HashSet<>();
-		for (Contact c : local) localIds.add(c.getId());
-		remote = new HashSet<>(remote);
-		synchronized (lock) {
-			if (state != State.FETCHING_CONTACT_LIST) return;
-			for (ContactId c : localIds) {
-				if (!remote.contains(c)) updates.add(new Update(true, c));
-			}
-			for (ContactId c : remote) {
-				if (!localIds.contains(c)) updates.add(new Update(false, c));
-			}
-			if (updates.isEmpty()) {
-				LOG.info("Contact list is up to date");
-				state = State.WAITING_FOR_CHANGES;
-			} else {
-				if (LOG.isLoggable(INFO)) {
-					LOG.info(updates.size() + " updates to apply");
-				}
-				state = State.UPDATING_CONTACT_LIST;
-				ioExecutor.execute(this::updateContactList);
-			}
-		}
-	}
-
-	@IoExecutor
-	private void updateContactList() {
-		Update update;
-		synchronized (lock) {
-			if (state != State.UPDATING_CONTACT_LIST) return;
-			update = updates.poll();
-			if (update == null) {
-				LOG.info("No more updates to process");
-				state = State.WAITING_FOR_CHANGES;
-				apiCall = null;
-				return;
-			}
-		}
-		if (update.add) loadMailboxProperties(update.contactId);
-		else removeContact(update.contactId);
-	}
-
-	@IoExecutor
-	private void loadMailboxProperties(ContactId c) {
-		synchronized (lock) {
-			if (state != State.UPDATING_CONTACT_LIST) return;
-		}
-		LOG.info("Loading mailbox properties for contact");
-		try {
-			MailboxUpdate mailboxUpdate = db.transactionWithResult(true, txn ->
-					mailboxUpdateManager.getLocalUpdate(txn, c));
-			if (mailboxUpdate instanceof MailboxUpdateWithMailbox) {
-				addContact(c, (MailboxUpdateWithMailbox) mailboxUpdate);
-			} else {
-				// Our own mailbox was concurrently unpaired. This worker will
-				// be destroyed soon, so we can stop here
-				LOG.info("Own mailbox was unpaired");
-			}
-		} catch (NoSuchContactException e) {
-			// Contact was removed concurrently. Move on to the next update.
-			// Later we may process a removal update for this contact, which
-			// was never added to the mailbox's contact list. The removal API
-			// call should fail safely with a TolerableFailureException
-			LOG.info("No such contact");
-			updateContactList();
-		} catch (DbException e) {
-			logException(LOG, WARNING, e);
-		}
-	}
-
-	@IoExecutor
-	private void addContact(ContactId c, MailboxUpdateWithMailbox withMailbox) {
-		MailboxProperties props = withMailbox.getMailboxProperties();
-		MailboxContact contact = new MailboxContact(c, props.getAuthToken(),
-				requireNonNull(props.getInboxId()),
-				requireNonNull(props.getOutboxId()));
-		synchronized (lock) {
-			if (state != State.UPDATING_CONTACT_LIST) return;
-			apiCall = mailboxApiCaller.retryWithBackoff(new SimpleApiCall(() ->
-					apiCallAddContact(contact)));
-		}
-	}
-
-	@IoExecutor
-	private void apiCallAddContact(MailboxContact contact)
-			throws IOException, ApiException, TolerableFailureException {
-		synchronized (lock) {
-			if (state != State.UPDATING_CONTACT_LIST) return;
-		}
-		LOG.info("Adding contact to remote contact list");
-		mailboxApi.addContact(mailboxProperties, contact);
-		updateContactList();
-	}
-
-	@IoExecutor
-	private void removeContact(ContactId c) {
-		synchronized (lock) {
-			if (state != State.UPDATING_CONTACT_LIST) return;
-			apiCall = mailboxApiCaller.retryWithBackoff(new SimpleApiCall(() ->
-					apiCallRemoveContact(c)));
-		}
-	}
-
-	@IoExecutor
-	private void apiCallRemoveContact(ContactId c)
-			throws IOException, ApiException {
-		synchronized (lock) {
-			if (state != State.UPDATING_CONTACT_LIST) return;
-		}
-		LOG.info("Removing contact from remote contact list");
-		try {
-			mailboxApi.deleteContact(mailboxProperties, c);
-		} catch (TolerableFailureException e) {
-			// Catch this so we can continue to the next update
-			LOG.warning("Contact does not exist");
-		}
-		updateContactList();
-	}
-
-	@Override
-	public void eventOccurred(Event e) {
-		if (e instanceof ContactAddedEvent) {
-			LOG.info("Contact added");
-			onContactAdded(((ContactAddedEvent) e).getContactId());
-		} else if (e instanceof ContactRemovedEvent) {
-			LOG.info("Contact removed");
-			onContactRemoved(((ContactRemovedEvent) e).getContactId());
-		}
-	}
-
-	@EventExecutor
-	private void onContactAdded(ContactId c) {
-		synchronized (lock) {
-			if (state != State.UPDATING_CONTACT_LIST &&
-					state != State.WAITING_FOR_CHANGES) {
-				return;
-			}
-			updates.add(new Update(true, c));
-			if (state == State.WAITING_FOR_CHANGES) {
-				state = State.UPDATING_CONTACT_LIST;
-				ioExecutor.execute(this::updateContactList);
-			}
-		}
-	}
-
-	@EventExecutor
-	private void onContactRemoved(ContactId c) {
-		synchronized (lock) {
-			if (state != State.UPDATING_CONTACT_LIST &&
-					state != State.WAITING_FOR_CHANGES) {
-				return;
-			}
-			updates.add(new Update(false, c));
-			if (state == State.WAITING_FOR_CHANGES) {
-				state = State.UPDATING_CONTACT_LIST;
-				ioExecutor.execute(this::updateContactList);
-			}
-		}
-	}
-
-	/**
-	 * An update that should be applied to the remote contact list.
-	 */
-	private static class Update {
-
-		/**
-		 * True if the contact should be added, false if the contact should be
-		 * removed.
-		 */
-		private final boolean add;
-		private final ContactId contactId;
-
-		private Update(boolean add, ContactId contactId) {
-			this.add = add;
-			this.contactId = contactId;
-		}
-	}
-}

bramble-core/src/main/java/org/briarproject/bramble/mailbox/OwnMailboxDownloadWorker.java

@@ -1,148 +0,0 @@
-package org.briarproject.bramble.mailbox;
-
-import org.briarproject.bramble.api.mailbox.MailboxFolderId;
-import org.briarproject.bramble.api.mailbox.MailboxProperties;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.mailbox.MailboxApi.ApiException;
-import org.briarproject.bramble.mailbox.MailboxApi.MailboxFile;
-import org.briarproject.bramble.mailbox.MailboxApi.TolerableFailureException;
-
-import java.io.IOException;
-import java.util.ArrayList;
-import java.util.HashMap;
-import java.util.Iterator;
-import java.util.LinkedList;
-import java.util.List;
-import java.util.Map;
-import java.util.Queue;
-
-import javax.annotation.concurrent.ThreadSafe;
-
-import static java.util.Collections.shuffle;
-import static java.util.logging.Level.INFO;
-
-@ThreadSafe
-@NotNullByDefault
-class OwnMailboxDownloadWorker extends MailboxDownloadWorker {
-
-	/**
-	 * The maximum number of files that will be downloaded before checking
-	 * again for folders with available files. This ensures that if a file
-	 * arrives during a download cycle, its folder will be checked within a
-	 * reasonable amount of time even if some other folder has a very large
-	 * number of files.
-	 * <p>
-	 * Package access for testing.
-	 */
-	static final int MAX_ROUND_ROBIN_FILES = 1000;
-
-	OwnMailboxDownloadWorker(
-			ConnectivityChecker connectivityChecker,
-			TorReachabilityMonitor torReachabilityMonitor,
-			MailboxApiCaller mailboxApiCaller,
-			MailboxApi mailboxApi,
-			MailboxFileManager mailboxFileManager,
-			MailboxProperties mailboxProperties) {
-		super(connectivityChecker, torReachabilityMonitor, mailboxApiCaller,
-				mailboxApi, mailboxFileManager, mailboxProperties);
-		if (!mailboxProperties.isOwner()) throw new IllegalArgumentException();
-	}
-
-	@Override
-	protected ApiCall createApiCallForDownloadCycle() {
-		return new SimpleApiCall(this::apiCallListFolders);
-	}
-
-	private void apiCallListFolders() throws IOException, ApiException {
-		synchronized (lock) {
-			if (state == State.DESTROYED) return;
-		}
-		LOG.info("Listing folders with available files");
-		List<MailboxFolderId> folders =
-				mailboxApi.getFolders(mailboxProperties);
-		if (folders.isEmpty()) onDownloadCycleFinished();
-		else listNextFolder(new LinkedList<>(folders), new HashMap<>());
-	}
-
-	/**
-	 * Removes the next folder from `queue` and starts a task to list the
-	 * files in the folder and add them to `available`.
-	 */
-	private void listNextFolder(Queue<MailboxFolderId> queue,
-			Map<MailboxFolderId, Queue<MailboxFile>> available) {
-		synchronized (lock) {
-			if (state == State.DESTROYED) return;
-			MailboxFolderId folder = queue.remove();
-			apiCall = mailboxApiCaller.retryWithBackoff(new SimpleApiCall(() ->
-					apiCallListFolder(folder, queue, available)));
-		}
-	}
-
-	private void apiCallListFolder(MailboxFolderId folder,
-			Queue<MailboxFolderId> queue,
-			Map<MailboxFolderId, Queue<MailboxFile>> available)
-			throws IOException, ApiException {
-		synchronized (lock) {
-			if (state == State.DESTROYED) return;
-		}
-		LOG.info("Listing folder");
-		try {
-			List<MailboxFile> files =
-					mailboxApi.getFiles(mailboxProperties, folder);
-			if (!files.isEmpty()) {
-				available.put(folder, new LinkedList<>(files));
-			}
-		} catch (TolerableFailureException e) {
-			LOG.warning("Folder does not exist");
-		}
-		if (queue.isEmpty()) {
-			LOG.info("Finished listing folders");
-			if (available.isEmpty()) onDownloadCycleFinished();
-			else createDownloadQueue(available);
-		} else {
-			listNextFolder(queue, available);
-		}
-	}
-
-	/**
-	 * Visits the given folders in round-robin order to create a queue of up to
-	 * {@link #MAX_ROUND_ROBIN_FILES} to download.
-	 */
-	private void createDownloadQueue(
-			Map<MailboxFolderId, Queue<MailboxFile>> available) {
-		synchronized (lock) {
-			if (state == State.DESTROYED) return;
-		}
-		if (LOG.isLoggable(INFO)) {
-			LOG.info(available.size() + " folders have available files");
-		}
-		Queue<FolderFile> queue = createRoundRobinQueue(available);
-		if (LOG.isLoggable(INFO)) {
-			LOG.info("Downloading " + queue.size() + " files");
-		}
-		downloadNextFile(queue);
-	}
-
-	// Package access for testing
-	Queue<FolderFile> createRoundRobinQueue(
-			Map<MailboxFolderId, Queue<MailboxFile>> available) {
-		List<MailboxFolderId> roundRobin = new ArrayList<>(available.keySet());
-		// Shuffle the folders so we don't always favour the same folders
-		shuffle(roundRobin);
-		Queue<FolderFile> queue = new LinkedList<>();
-		while (queue.size() < MAX_ROUND_ROBIN_FILES && !available.isEmpty()) {
-			Iterator<MailboxFolderId> it = roundRobin.iterator();
-			while (queue.size() < MAX_ROUND_ROBIN_FILES && it.hasNext()) {
-				MailboxFolderId folder = it.next();
-				Queue<MailboxFile> files = available.get(folder);
-				MailboxFile file = files.remove();
-				queue.add(new FolderFile(folder, file.name));
-				if (files.isEmpty()) {
-					available.remove(folder);
-					it.remove();
-				}
-			}
-		}
-		return queue;
-	}
-}

bramble-core/src/main/java/org/briarproject/bramble/mailbox/UrlConverter.java

@@ -1,17 +0,0 @@
-package org.briarproject.bramble.mailbox;
-
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-
-/**
- * An interface for converting an onion address to an HTTP URL, allowing the
- * conversion to be customised for integration tests.
- */
-@NotNullByDefault
-interface UrlConverter {
-
-   /**
-    * Converts a raw onion address, excluding the .onion suffix, into an
-    * HTTP URL.
-    */
-   String convertOnionToBaseUrl(String onion);
-}

bramble-core/src/main/java/org/briarproject/bramble/mailbox/UrlConverterImpl.java

@@ -1,18 +0,0 @@
-package org.briarproject.bramble.mailbox;
-
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-
-import javax.inject.Inject;
-
-@NotNullByDefault
-class UrlConverterImpl implements UrlConverter {
-
-	@Inject
-	UrlConverterImpl() {
-	}
-
-	@Override
-	public String convertOnionToBaseUrl(String onion) {
-		return "http://" + onion + ".onion";
-	}
-}

bramble-core/src/main/java/org/briarproject/bramble/plugin/BackoffFactoryImpl.java

@@ -1,8 +1,10 @@
 package org.briarproject.bramble.plugin;
 
+import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.Backoff;
 import org.briarproject.bramble.api.plugin.BackoffFactory;
+import org.briarproject.bramble.api.plugin.TransportId;
 
 import javax.annotation.concurrent.Immutable;
 
@@ -11,8 +13,9 @@ import javax.annotation.concurrent.Immutable;
 class BackoffFactoryImpl implements BackoffFactory {
 
 	@Override
-	public Backoff createBackoff(int minInterval, int maxInterval,
-			double base) {
-		return new BackoffImpl(minInterval, maxInterval, base);
+	public Backoff createBackoff(EventBus eventBus, TransportId transportId,
+			int minInterval, int maxInterval, double base) {
+		return new BackoffImpl(eventBus, transportId, minInterval, maxInterval,
+				base);
 	}
 }

bramble-core/src/main/java/org/briarproject/bramble/plugin/BackoffImpl.java

@@ -1,7 +1,10 @@
 package org.briarproject.bramble.plugin;
 
+import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.Backoff;
+import org.briarproject.bramble.api.plugin.TransportId;
+import org.briarproject.bramble.api.plugin.event.PollingIntervalDecreasedEvent;
 
 import java.util.concurrent.atomic.AtomicInteger;
 
@@ -11,11 +14,16 @@ import javax.annotation.concurrent.ThreadSafe;
 @NotNullByDefault
 class BackoffImpl implements Backoff {
 
+	private final EventBus eventBus;
+	private final TransportId transportId;
 	private final int minInterval, maxInterval;
 	private final double base;
 	private final AtomicInteger backoff;
 
-	BackoffImpl(int minInterval, int maxInterval, double base) {
+	BackoffImpl(EventBus eventBus, TransportId transportId,
+			int minInterval, int maxInterval, double base) {
+		this.eventBus = eventBus;
+		this.transportId = transportId;
 		this.minInterval = minInterval;
 		this.maxInterval = maxInterval;
 		this.base = base;
@@ -37,6 +45,9 @@ class BackoffImpl implements Backoff {
 
 	@Override
 	public void reset() {
-		backoff.set(0);
+		int old = backoff.getAndSet(0);
+		if (old > 0) {
+			eventBus.broadcast(new PollingIntervalDecreasedEvent(transportId));
+		}
 	}
 }

bramble-core/src/main/java/org/briarproject/bramble/plugin/PluginManagerImpl.java

@@ -20,6 +20,7 @@ import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPluginFactory;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
+import org.briarproject.bramble.api.plugin.event.PollingIntervalDecreasedEvent;
 import org.briarproject.bramble.api.plugin.event.TransportActiveEvent;
 import org.briarproject.bramble.api.plugin.event.TransportInactiveEvent;
 import org.briarproject.bramble.api.plugin.event.TransportStateEvent;
@@ -362,6 +363,11 @@ class PluginManagerImpl implements PluginManager, Service {
 			}
 		}
 
+		@Override
+		public void pollingIntervalDecreased() {
+			eventBus.broadcast(new PollingIntervalDecreasedEvent(id));
+		}
+
 		@Override
 		public void handleConnection(DuplexTransportConnection d) {
 			connectionManager.manageIncomingConnection(id, d);

bramble-core/src/main/java/org/briarproject/bramble/plugin/PollerImpl.java

@@ -20,7 +20,7 @@ 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.plugin.event.ConnectionClosedEvent;
-import org.briarproject.bramble.api.plugin.event.ConnectionOpenedEvent;
+import org.briarproject.bramble.api.plugin.event.PollingIntervalDecreasedEvent;
 import org.briarproject.bramble.api.plugin.event.TransportActiveEvent;
 import org.briarproject.bramble.api.plugin.event.TransportInactiveEvent;
 import org.briarproject.bramble.api.plugin.simplex.SimplexPlugin;
@@ -107,10 +107,14 @@ class PollerImpl implements Poller, EventListener {
 			if (!c.isIncoming() && c.isException()) {
 				connectToContact(c.getContactId(), c.getTransportId());
 			}
-		} else if (e instanceof ConnectionOpenedEvent) {
-			ConnectionOpenedEvent c = (ConnectionOpenedEvent) e;
-			// Reschedule polling, the polling interval may have decreased
-			reschedule(c.getTransportId());
+		} else if (e instanceof PollingIntervalDecreasedEvent) {
+			PollingIntervalDecreasedEvent p = (PollingIntervalDecreasedEvent) e;
+			TransportId t = p.getTransportId();
+			if (LOG.isLoggable(INFO)) {
+				LOG.info("Polling interval decreased for " + t);
+			}
+			// Reschedule polling
+			reschedule(t);
 		} else if (e instanceof TransportActiveEvent) {
 			TransportActiveEvent t = (TransportActiveEvent) e;
 			// Poll the newly activated transport
@@ -228,7 +232,7 @@ class PollerImpl implements Poller, EventListener {
 				if (!connected.contains(c))
 					properties.add(new Pair<>(e.getValue(), new Handler(c, t)));
 			}
-			if (!properties.isEmpty()) p.poll(properties);
+			p.poll(properties);
 		} catch (DbException e) {
 			logException(LOG, WARNING, e);
 		}

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

@@ -335,7 +335,7 @@ abstract class AbstractBluetoothPlugin<S, SS> implements BluetoothPlugin,
 	@Override
 	public void poll(Collection<Pair<TransportProperties, ConnectionHandler>>
 			properties) {
-		if (getState() != ACTIVE) return;
+		if (properties.isEmpty() || getState() != ACTIVE) return;
 		backoff.increment();
 		for (Pair<TransportProperties, ConnectionHandler> p : properties) {
 			connect(p.getFirst(), p.getSecond());
@@ -427,13 +427,7 @@ abstract class AbstractBluetoothPlugin<S, SS> implements BluetoothPlugin,
 		BdfList descriptor = new BdfList();
 		descriptor.add(TRANSPORT_ID_BLUETOOTH);
 		String address = getBluetoothAddress();
-		if (address != null) {
-			try {
-				descriptor.add(macToBytes(address));
-			} catch (FormatException e) {
-				throw new RuntimeException();
-			}
-		}
+		if (address != null) descriptor.add(macToBytes(address));
 		return new BluetoothKeyAgreementListener(descriptor, ss);
 	}
 

bramble-core/src/main/java/org/briarproject/bramble/plugin/file/MailboxPluginFactory.java

@@ -9,12 +9,14 @@ import org.briarproject.bramble.api.plugin.simplex.SimplexPluginFactory;
 import javax.annotation.Nullable;
 import javax.inject.Inject;
 
+import static java.util.concurrent.TimeUnit.DAYS;
 import static org.briarproject.bramble.api.mailbox.MailboxConstants.ID;
-import static org.briarproject.bramble.api.mailbox.MailboxConstants.MAX_LATENCY;
 
 @NotNullByDefault
 public class MailboxPluginFactory implements SimplexPluginFactory {
 
+	private static final long MAX_LATENCY = DAYS.toMillis(14);
+
 	@Inject
 	MailboxPluginFactory() {
 	}

bramble-core/src/main/java/org/briarproject/bramble/plugin/file/RemovableDriveManagerImpl.java

@@ -106,8 +106,7 @@ class RemovableDriveManagerImpl
 	@Override
 	public boolean isWriterTaskNeeded(ContactId c) throws DbException {
 		return db.transactionWithResult(true, txn ->
-				db.containsAcksToSend(txn, c) ||
-						db.containsMessagesToSend(txn, c, MAX_LATENCY, true));
+				db.containsAnythingToSend(txn, c, MAX_LATENCY, true));
 	}
 
 	@Override

bramble-core/src/main/java/org/briarproject/bramble/plugin/tcp/LanTcpPlugin.java

@@ -285,7 +285,7 @@ class LanTcpPlugin extends TcpPlugin {
 				if (ip.length == 16) addrs.add(InetAddress.getByAddress(ip));
 			}
 			return addrs;
-		} catch (FormatException | UnknownHostException e) {
+		} catch (IllegalArgumentException | UnknownHostException e) {
 			return emptyList();
 		}
 	}

bramble-core/src/main/java/org/briarproject/bramble/plugin/tcp/LanTcpPluginFactory.java

@@ -56,8 +56,8 @@ public class LanTcpPluginFactory implements DuplexPluginFactory {
 
 	@Override
 	public DuplexPlugin createPlugin(PluginCallback callback) {
-		Backoff backoff = backoffFactory.createBackoff(MIN_POLLING_INTERVAL,
-				MAX_POLLING_INTERVAL, BACKOFF_BASE);
+		Backoff backoff = backoffFactory.createBackoff(eventBus, ID,
+				MIN_POLLING_INTERVAL, MAX_POLLING_INTERVAL, BACKOFF_BASE);
 		LanTcpPlugin plugin = new LanTcpPlugin(ioExecutor, wakefulIoExecutor,
 				backoff, callback, MAX_LATENCY, MAX_IDLE_TIME,
 				CONNECTION_TIMEOUT);

bramble-core/src/main/java/org/briarproject/bramble/plugin/tcp/TcpPlugin.java

@@ -246,7 +246,7 @@ abstract class TcpPlugin implements DuplexPlugin, EventListener {
 	@Override
 	public void poll(Collection<Pair<TransportProperties, ConnectionHandler>>
 			properties) {
-		if (getState() != ACTIVE) return;
+		if (properties.isEmpty() || getState() != ACTIVE) return;
 		backoff.increment();
 		for (Pair<TransportProperties, ConnectionHandler> p : properties) {
 			connect(p.getFirst(), p.getSecond());

bramble-core/src/main/java/org/briarproject/bramble/plugin/tcp/WanTcpPluginFactory.java

@@ -60,8 +60,8 @@ public class WanTcpPluginFactory implements DuplexPluginFactory {
 
 	@Override
 	public DuplexPlugin createPlugin(PluginCallback callback) {
-		Backoff backoff = backoffFactory.createBackoff(MIN_POLLING_INTERVAL,
-				MAX_POLLING_INTERVAL, BACKOFF_BASE);
+		Backoff backoff = backoffFactory.createBackoff(eventBus, ID,
+				MIN_POLLING_INTERVAL, MAX_POLLING_INTERVAL, BACKOFF_BASE);
 		PortMapper portMapper = new PortMapperImpl(shutdownManager);
 		WanTcpPlugin plugin = new WanTcpPlugin(ioExecutor, wakefulIoExecutor,
 				backoff, portMapper, callback, MAX_LATENCY, MAX_IDLE_TIME,

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

@@ -12,8 +12,7 @@ public interface CircumventionProvider {
 		DEFAULT_OBFS4,
 		NON_DEFAULT_OBFS4,
 		VANILLA,
-		MEEK,
-		SNOWFLAKE
+		MEEK
 	}
 
 	/**
@@ -42,14 +41,13 @@ public interface CircumventionProvider {
 	 * Countries where non-default obfs4 or vanilla bridges are likely to work.
 	 * Should be a subset of {@link #BRIDGES}.
 	 */
-	String[] NON_DEFAULT_BRIDGES = {"BY", "RU"};
+	String[] NON_DEFAULT_BRIDGES = {"BY", "RU", "TM"};
 
 	/**
 	 * Countries where vanilla bridges are blocked via DPI but non-default
-	 * obfs4 bridges, meek and snowflake may work. Should be a subset of
-	 * {@link #BRIDGES}.
+	 * obfs4 bridges and meek may work. Should be a subset of {@link #BRIDGES}.
 	 */
-	String[] DPI_BRIDGES = {"CN", "IR", "TM"};
+	String[] DPI_BRIDGES = {"CN", "IR"};
 
 	/**
 	 * Returns true if vanilla Tor connections are blocked in the given country.
@@ -70,6 +68,6 @@ public interface CircumventionProvider {
 	List<BridgeType> getSuitableBridgeTypes(String countryCode);
 
 	@IoExecutor
-	List<String> getBridges(BridgeType type, String countryCode,
-			boolean letsEncrypt);
+	List<String> getBridges(BridgeType type);
+
 }

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

@@ -7,10 +7,8 @@ import java.io.InputStream;
 import java.util.ArrayList;
 import java.util.HashSet;
 import java.util.List;
-import java.util.Map;
 import java.util.Scanner;
 import java.util.Set;
-import java.util.TreeMap;
 
 import javax.annotation.concurrent.Immutable;
 import javax.inject.Inject;
@@ -20,7 +18,6 @@ import static org.briarproject.bramble.api.nullsafety.NullSafety.requireNonNull;
 import static org.briarproject.bramble.plugin.tor.CircumventionProvider.BridgeType.DEFAULT_OBFS4;
 import static org.briarproject.bramble.plugin.tor.CircumventionProvider.BridgeType.MEEK;
 import static org.briarproject.bramble.plugin.tor.CircumventionProvider.BridgeType.NON_DEFAULT_OBFS4;
-import static org.briarproject.bramble.plugin.tor.CircumventionProvider.BridgeType.SNOWFLAKE;
 import static org.briarproject.bramble.plugin.tor.CircumventionProvider.BridgeType.VANILLA;
 
 @Immutable
@@ -28,8 +25,6 @@ import static org.briarproject.bramble.plugin.tor.CircumventionProvider.BridgeTy
 class CircumventionProviderImpl implements CircumventionProvider {
 
 	private final static String BRIDGE_FILE_NAME = "bridges";
-	private final static String SNOWFLAKE_PARAMS_FILE_NAME = "snowflake-params";
-	private final static String DEFAULT_COUNTRY_CODE = "ZZ";
 
 	private static final Set<String> BLOCKED_IN_COUNTRIES =
 			new HashSet<>(asList(BLOCKED));
@@ -63,7 +58,7 @@ class CircumventionProviderImpl implements CircumventionProvider {
 		} else if (NON_DEFAULT_BRIDGE_COUNTRIES.contains(countryCode)) {
 			return asList(NON_DEFAULT_OBFS4, VANILLA);
 		} else if (DPI_COUNTRIES.contains(countryCode)) {
-			return asList(NON_DEFAULT_OBFS4, MEEK, SNOWFLAKE);
+			return asList(NON_DEFAULT_OBFS4, MEEK);
 		} else {
 			return asList(DEFAULT_OBFS4, VANILLA);
 		}
@@ -71,8 +66,7 @@ class CircumventionProviderImpl implements CircumventionProvider {
 
 	@Override
 	@IoExecutor
-	public List<String> getBridges(BridgeType type, String countryCode,
-			boolean letsEncrypt) {
+	public List<String> getBridges(BridgeType type) {
 		InputStream is = requireNonNull(getClass().getClassLoader()
 				.getResourceAsStream(BRIDGE_FILE_NAME));
 		Scanner scanner = new Scanner(is);
@@ -85,45 +79,10 @@ class CircumventionProviderImpl implements CircumventionProvider {
 					(type == VANILLA && line.startsWith("v ")) ||
 					(type == MEEK && line.startsWith("m "))) {
 				bridges.add(line.substring(2));
-			} else if (type == SNOWFLAKE && line.startsWith("s ")) {
-				String params = getSnowflakeParams(countryCode, letsEncrypt);
-				bridges.add(line.substring(2) + " " + params);
 			}
 		}
 		scanner.close();
 		return bridges;
 	}
 
-	// Package access for testing
-	@SuppressWarnings("WeakerAccess")
-	String getSnowflakeParams(String countryCode, boolean letsEncrypt) {
-		Map<String, String> params = loadSnowflakeParams();
-		if (countryCode.isEmpty()) countryCode = DEFAULT_COUNTRY_CODE;
-		// If we have parameters for this country code, return them
-		String value = params.get(makeKey(countryCode, letsEncrypt));
-		if (value != null) return value;
-		// Return the default parameters
-		value = params.get(makeKey(DEFAULT_COUNTRY_CODE, letsEncrypt));
-		return requireNonNull(value);
-	}
-
-	private Map<String, String> loadSnowflakeParams() {
-		InputStream is = requireNonNull(getClass().getClassLoader()
-				.getResourceAsStream(SNOWFLAKE_PARAMS_FILE_NAME));
-		Scanner scanner = new Scanner(is);
-		Map<String, String> params = new TreeMap<>();
-		while (scanner.hasNextLine()) {
-			String line = scanner.nextLine();
-			if (line.length() < 5) continue;
-			String key = line.substring(0, 4); // Country code, space, digit
-			String value = line.substring(5);
-			params.put(key, value);
-		}
-		scanner.close();
-		return params;
-	}
-
-	private String makeKey(String countryCode, boolean letsEncrypt) {
-		return countryCode + " " + (letsEncrypt ? "1" : "0");
-	}
 }

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

@@ -18,7 +18,6 @@ import org.briarproject.bramble.api.network.event.NetworkStatusEvent;
 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;
@@ -26,6 +25,7 @@ import org.briarproject.bramble.api.plugin.TorConstants;
 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.plugin.event.ConnectionClosedEvent;
 import org.briarproject.bramble.api.properties.TransportProperties;
 import org.briarproject.bramble.api.rendezvous.KeyMaterialSource;
 import org.briarproject.bramble.api.rendezvous.RendezvousEndpoint;
@@ -65,9 +65,9 @@ import javax.annotation.concurrent.ThreadSafe;
 import javax.net.SocketFactory;
 
 import static java.util.Arrays.asList;
-import static java.util.Collections.emptyList;
 import static java.util.Collections.singletonList;
 import static java.util.Collections.singletonMap;
+import static java.util.concurrent.TimeUnit.MINUTES;
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
@@ -94,8 +94,9 @@ import static org.briarproject.bramble.api.plugin.TorConstants.PROP_ONION_V3;
 import static org.briarproject.bramble.api.plugin.TorConstants.REASON_BATTERY;
 import static org.briarproject.bramble.api.plugin.TorConstants.REASON_COUNTRY_BLOCKED;
 import static org.briarproject.bramble.api.plugin.TorConstants.REASON_MOBILE_DATA;
+import static org.briarproject.bramble.plugin.tor.CircumventionProvider.BridgeType.DEFAULT_OBFS4;
 import static org.briarproject.bramble.plugin.tor.CircumventionProvider.BridgeType.MEEK;
-import static org.briarproject.bramble.plugin.tor.CircumventionProvider.BridgeType.SNOWFLAKE;
+import static org.briarproject.bramble.plugin.tor.CircumventionProvider.BridgeType.NON_DEFAULT_OBFS4;
 import static org.briarproject.bramble.plugin.tor.TorRendezvousCrypto.SEED_BYTES;
 import static org.briarproject.bramble.util.IoUtils.copyAndClose;
 import static org.briarproject.bramble.util.IoUtils.tryToClose;
@@ -124,6 +125,45 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	private static final int COOKIE_POLLING_INTERVAL_MS = 200;
 	private static final Pattern ONION_V3 = Pattern.compile("[a-z2-7]{56}");
 
+	/**
+	 * After this many consecutive successful connections to our own hidden
+	 * service we consider the network to be stable.
+	 * <p>
+	 * This constant times {@link #POLLING_INTERVAL_UNSTABLE} should be
+	 * greater than {@link #POLLING_INTERVAL_STABLE}. This ensures that if
+	 * we experience a network outage that isn't detected by the
+	 * {@link NetworkManager}, and if one of our contacts comes online during
+	 * the outage, then either the outage lasts longer than
+	 * {@link #POLLING_INTERVAL_STABLE}, in which case we detect the outage
+	 * by failing to connect to our own hidden service, or the outage ends
+	 * before the contact considers their own network connection to be stable,
+	 * in which case the contact is still trying to connect to us when the
+	 * outage ends. Either way, we don't end up in a situation where both we
+	 * and the contact consider our network connections to be stable and stop
+	 * trying to connect to each other, despite both being online.
+	 */
+	private static final int STABLE_NETWORK_THRESHOLD = 10;
+
+	/**
+	 * After this many consecutive failed connections to our own hidden service
+	 * we consider our connection to the Tor network to be broken.
+	 */
+	private static final int BROKEN_NETWORK_THRESHOLD = 3;
+
+	/**
+	 * How often to poll our own hidden service when the network is considered
+	 * to be stable.
+	 */
+	private static final int POLLING_INTERVAL_STABLE =
+			(int) MINUTES.toMillis(10);
+
+	/**
+	 * How often to poll our own hidden service and our contacts' hidden
+	 * services when the network is considered to be unstable.
+	 */
+	private static final int POLLING_INTERVAL_UNSTABLE =
+			(int) MINUTES.toMillis(2);
+
 	protected final Executor ioExecutor;
 	private final Executor wakefulIoExecutor;
 	private final Executor connectionStatusExecutor;
@@ -132,7 +172,6 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	private final SocketFactory torSocketFactory;
 	private final Clock clock;
 	private final BatteryManager batteryManager;
-	private final Backoff backoff;
 	private final TorRendezvousCrypto torRendezvousCrypto;
 	private final PluginCallback callback;
 	private final String architecture;
@@ -152,6 +191,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	private volatile Socket controlSocket = null;
 	private volatile TorControlConnection controlConnection = null;
 	private volatile Settings settings = null;
+	private volatile String ownOnion = null;
 
 	protected abstract int getProcessId();
 
@@ -166,7 +206,6 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			ResourceProvider resourceProvider,
 			CircumventionProvider circumventionProvider,
 			BatteryManager batteryManager,
-			Backoff backoff,
 			TorRendezvousCrypto torRendezvousCrypto,
 			PluginCallback callback,
 			String architecture,
@@ -184,7 +223,6 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		this.resourceProvider = resourceProvider;
 		this.circumventionProvider = circumventionProvider;
 		this.batteryManager = batteryManager;
-		this.backoff = backoff;
 		this.torRendezvousCrypto = torRendezvousCrypto;
 		this.callback = callback;
 		this.architecture = architecture;
@@ -213,10 +251,6 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		return new File(torDirectory, "obfs4proxy");
 	}
 
-	protected File getSnowflakeExecutableFile() {
-		return new File(torDirectory, "snowflake");
-	}
-
 	@Override
 	public TransportId getId() {
 		return TorConstants.ID;
@@ -243,14 +277,8 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		}
 		// Load the settings
 		settings = callback.getSettings();
-		try {
-			// Install or update the assets if necessary
-			if (!assetsAreUpToDate()) installAssets();
-			// Start from the default config every time
-			extract(getConfigInputStream(), configFile);
-		} catch (IOException e) {
-			throw new PluginException(e);
-		}
+		// Install or update the assets if necessary
+		if (!assetsAreUpToDate()) installAssets();
 		if (cookieFile.exists() && !cookieFile.delete())
 			LOG.warning("Old auth cookie not deleted");
 		// Start a new Tor process
@@ -312,7 +340,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			info = controlConnection.getInfo("status/circuit-established");
 			if ("1".equals(info)) {
 				LOG.info("Tor has already built a circuit");
-				state.setCircuitBuilt(true);
+				state.getAndSetCircuitBuilt(true);
 			}
 		} catch (TorNotRunningException e) {
 			throw new RuntimeException(e);
@@ -331,21 +359,25 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		return doneFile.lastModified() > getLastUpdateTime();
 	}
 
-	private void installAssets() throws IOException {
-		// The done file may already exist from a previous installation
-		//noinspection ResultOfMethodCallIgnored
-		doneFile.delete();
-		// The GeoIP file may exist from a previous installation - we can
-		// save some space by deleting it.
-		// TODO: Remove after a reasonable migration period
-		//  (added 2022-03-29)
-		//noinspection ResultOfMethodCallIgnored
-		geoIpFile.delete();
-		installTorExecutable();
-		installObfs4Executable();
-		installSnowflakeExecutable();
-		if (!doneFile.createNewFile())
-			LOG.warning("Failed to create done file");
+	private void installAssets() throws PluginException {
+		try {
+			// The done file may already exist from a previous installation
+			//noinspection ResultOfMethodCallIgnored
+			doneFile.delete();
+			// The GeoIP file may exist from a previous installation - we can
+			// save some space by deleting it.
+			// TODO: Remove after a reasonable migration period
+			//  (added 2022-03-29)
+			//noinspection ResultOfMethodCallIgnored
+			geoIpFile.delete();
+			installTorExecutable();
+			installObfs4Executable();
+			extract(getConfigInputStream(), configFile);
+			if (!doneFile.createNewFile())
+				LOG.warning("Failed to create done file");
+		} catch (IOException e) {
+			throw new PluginException(e);
+		}
 	}
 
 	protected void extract(InputStream in, File dest) throws IOException {
@@ -369,29 +401,17 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		if (!obfs4File.setExecutable(true, true)) throw new IOException();
 	}
 
-	protected void installSnowflakeExecutable() throws IOException {
-		if (LOG.isLoggable(INFO))
-			LOG.info("Installing snowflake binary for " + architecture);
-		File snowflakeFile = getSnowflakeExecutableFile();
-		extract(getSnowflakeInputStream(), snowflakeFile);
-		if (!snowflakeFile.setExecutable(true, true)) throw new IOException();
-	}
-
 	private InputStream getTorInputStream() throws IOException {
-		return getZipInputStream("tor");
+		InputStream in = resourceProvider
+				.getResourceInputStream("tor_" + architecture, ".zip");
+		ZipInputStream zin = new ZipInputStream(in);
+		if (zin.getNextEntry() == null) throw new IOException();
+		return zin;
 	}
 
 	private InputStream getObfs4InputStream() throws IOException {
-		return getZipInputStream("obfs4proxy");
-	}
-
-	private InputStream getSnowflakeInputStream() throws IOException {
-		return getZipInputStream("snowflake");
-	}
-
-	private InputStream getZipInputStream(String basename) throws IOException {
 		InputStream in = resourceProvider
-				.getResourceInputStream(basename + "_" + architecture, ".zip");
+				.getResourceInputStream("obfs4proxy_" + architecture, ".zip");
 		ZipInputStream zin = new ZipInputStream(in);
 		if (zin.getNextEntry() == null) throw new IOException();
 		return zin;
@@ -416,12 +436,6 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		append(strb, "SocksPort", torSocksPort);
 		strb.append("GeoIPFile\n");
 		strb.append("GeoIPv6File\n");
-		append(strb, "ConnectionPadding", 0);
-		String obfs4Path = getObfs4ExecutableFile().getAbsolutePath();
-		append(strb, "ClientTransportPlugin obfs4 exec", obfs4Path);
-		append(strb, "ClientTransportPlugin meek_lite exec", obfs4Path);
-		String snowflakePath = getSnowflakeExecutableFile().getAbsolutePath();
-		append(strb, "ClientTransportPlugin snowflake exec", snowflakePath);
 		//noinspection CharsetObjectCanBeUsed
 		return new ByteArrayInputStream(
 				strb.toString().getBytes(Charset.forName("UTF-8")));
@@ -498,7 +512,6 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			callback.mergeSettings(s);
 			// Create a hidden service if necessary
 			ioExecutor.execute(() -> publishHiddenService(localPort));
-			backoff.reset();
 			// Accept incoming hidden service connections from Tor
 			acceptContactConnections(ss);
 		});
@@ -537,6 +550,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			return;
 		}
 		String onion3 = response.get(HS_ADDRESS);
+		ownOnion = onion3;
 		if (LOG.isLoggable(INFO)) {
 			LOG.info("V3 hidden service " + scrubOnion(onion3));
 		}
@@ -565,13 +579,12 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 				return;
 			}
 			LOG.info("Connection received");
-			backoff.reset();
 			callback.handleConnection(new TorTransportConnection(this, s));
 		}
 	}
 
 	protected void enableNetwork(boolean enable) throws IOException {
-		if (!state.enableNetwork(enable)) return; // Unchanged
+		state.enableNetwork(enable);
 		try {
 			controlConnection.setConf("DisableNetwork", enable ? "0" : "1");
 		} catch (TorNotRunningException e) {
@@ -579,37 +592,34 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		}
 	}
 
-	private void enableBridges(List<BridgeType> bridgeTypes, String countryCode)
+	private void enableBridges(boolean enable, List<BridgeType> bridgeTypes)
 			throws IOException {
-		if (!state.setBridgeTypes(bridgeTypes)) return; // Unchanged
 		try {
-			if (bridgeTypes.isEmpty()) {
-				controlConnection.setConf("UseBridges", "0");
-				controlConnection.resetConf(singletonList("Bridge"));
-			} else {
+			if (enable) {
 				Collection<String> conf = new ArrayList<>();
 				conf.add("UseBridges 1");
-				boolean letsEncrypt = canVerifyLetsEncryptCerts();
+				File obfs4File = getObfs4ExecutableFile();
+				if (bridgeTypes.contains(MEEK)) {
+					conf.add("ClientTransportPlugin meek_lite exec " +
+							obfs4File.getAbsolutePath());
+				}
+				if (bridgeTypes.contains(DEFAULT_OBFS4) ||
+						bridgeTypes.contains(NON_DEFAULT_OBFS4)) {
+					conf.add("ClientTransportPlugin obfs4 exec " +
+							obfs4File.getAbsolutePath());
+				}
 				for (BridgeType bridgeType : bridgeTypes) {
-					conf.addAll(circumventionProvider
-							.getBridges(bridgeType, countryCode, letsEncrypt));
+					conf.addAll(circumventionProvider.getBridges(bridgeType));
 				}
 				controlConnection.setConf(conf);
+			} else {
+				controlConnection.setConf("UseBridges", "0");
 			}
 		} catch (TorNotRunningException e) {
 			throw new RuntimeException(e);
 		}
 	}
 
-	/**
-	 * Returns true if this device can verify Let's Encrypt certificates signed
-	 * with the IdentTrust DST Root X3 certificate, which expired at the end of
-	 * September 2021.
-	 */
-	protected boolean canVerifyLetsEncryptCerts() {
-		return true;
-	}
-
 	@Override
 	public void stop() {
 		ServerSocket ss = state.setStopped();
@@ -617,6 +627,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		if (controlSocket != null && controlConnection != null) {
 			try {
 				LOG.info("Stopping Tor");
+				controlConnection.setConf("DisableNetwork", "1");
 				controlConnection.shutdownTor("TERM");
 				controlSocket.close();
 			} catch (TorNotRunningException e) {
@@ -644,14 +655,58 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 
 	@Override
 	public int getPollingInterval() {
-		return backoff.getPollingInterval();
+		if (state.isNetworkStable()) {
+			LOG.info("Using stable polling interval");
+			return POLLING_INTERVAL_STABLE;
+		} else {
+			LOG.info("Using unstable polling interval");
+			return POLLING_INTERVAL_UNSTABLE;
+		}
 	}
 
 	@Override
 	public void poll(Collection<Pair<TransportProperties, ConnectionHandler>>
 			properties) {
 		if (getState() != ACTIVE) return;
-		backoff.increment();
+		String ownOnion = this.ownOnion;
+		if (ownOnion == null) {
+			// Our own hidden service hasn't been created yet
+			pollContacts(properties);
+		} else {
+			// If the network is unstable, poll our contacts
+			boolean stable = state.isNetworkStable();
+			if (!stable) pollContacts(properties);
+			// Poll our own hidden service to check if the network is stable
+			wakefulIoExecutor.execute(() -> {
+				LOG.info("Connecting to own hidden service");
+				TransportProperties p = new TransportProperties();
+				p.put(PROP_ONION_V3, ownOnion);
+				DuplexTransportConnection d = createConnection(p);
+				if (d == null) {
+					LOG.info("Could not connect to own hidden service");
+					state.onStabilityCheckFailed();
+					// If the network was previously considered stable then
+					// we didn't poll our contacts above, so poll them now
+					if (stable) pollContacts(properties);
+				} else {
+					LOG.info("Connected to own hidden service");
+					// Close the connection (this will cause the other end of
+					// the connection to log an EOFException)
+					try {
+						d.getWriter().dispose(false);
+						d.getReader().dispose(false, false);
+					} catch (IOException e) {
+						logException(LOG, WARNING, e);
+					}
+					state.onStabilityCheckSucceeded();
+				}
+			});
+		}
+	}
+
+	private void pollContacts(
+			Collection<Pair<TransportProperties, ConnectionHandler>> properties) {
+		if (properties.isEmpty() || getState() != ACTIVE) return;
 		for (Pair<TransportProperties, ConnectionHandler> p : properties) {
 			connect(p.getFirst(), p.getSecond());
 		}
@@ -660,10 +715,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	private void connect(TransportProperties p, ConnectionHandler h) {
 		wakefulIoExecutor.execute(() -> {
 			DuplexTransportConnection d = createConnection(p);
-			if (d != null) {
-				backoff.reset();
-				h.handleConnection(d);
-			}
+			if (d != null) h.handleConnection(d);
 		});
 	}
 
@@ -784,9 +836,8 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	public void circuitStatus(String status, String id, String path) {
 		// In case of races between receiving CIRCUIT_ESTABLISHED and setting
 		// DisableNetwork, set our circuitBuilt flag if not already set
-		if (status.equals("BUILT") && state.setCircuitBuilt(true)) {
+		if (status.equals("BUILT") && !state.getAndSetCircuitBuilt(true)) {
 			LOG.info("Circuit built");
-			backoff.reset();
 		}
 	}
 
@@ -813,6 +864,9 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	@Override
 	public void message(String severity, String msg) {
 		if (LOG.isLoggable(INFO)) LOG.info(severity + " " + msg);
+		if (msg.startsWith("Switching to guard context")) {
+			state.resetNetworkStability();
+		}
 	}
 
 	@Override
@@ -831,13 +885,6 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		}
 	}
 
-	@Override
-	public void controlConnectionClosed() {
-		if (state.isTorRunning()) {
-			throw new RuntimeException("Control connection closed");
-		}
-	}
-
 	private String removeSeverity(String msg) {
 		return msg.replaceFirst("[^ ]+ ", "");
 	}
@@ -846,14 +893,10 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		if (msg.startsWith("BOOTSTRAP PROGRESS=100")) {
 			LOG.info("Bootstrapped");
 			state.setBootstrapped();
-			backoff.reset();
 		} else if (msg.startsWith("CIRCUIT_ESTABLISHED")) {
-			if (state.setCircuitBuilt(true)) {
-				LOG.info("Circuit built");
-				backoff.reset();
-			}
+			if (!state.getAndSetCircuitBuilt(true)) LOG.info("Circuit built");
 		} else if (msg.startsWith("CIRCUIT_NOT_ESTABLISHED")) {
-			if (state.setCircuitBuilt(false)) {
+			if (state.getAndSetCircuitBuilt(false)) {
 				LOG.info("Circuit not built");
 				// TODO: Disable and re-enable network to prompt Tor to rebuild
 				//  its guard/bridge connections? This will also close any
@@ -896,7 +939,15 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 
 	@Override
 	public void eventOccurred(Event e) {
-		if (e instanceof SettingsUpdatedEvent) {
+		if (e instanceof ConnectionClosedEvent) {
+			ConnectionClosedEvent c = (ConnectionClosedEvent) e;
+			if (c.getTransportId().equals(getId())
+					&& !c.isIncoming() && c.isException()) {
+				LOG.info("Outgoing connection closed with exception");
+				// The failure may indicate that the network is unstable
+				state.resetNetworkStability();
+			}
+		} else if (e instanceof SettingsUpdatedEvent) {
 			SettingsUpdatedEvent s = (SettingsUpdatedEvent) e;
 			if (s.getNamespace().equals(ID.getString())) {
 				LOG.info("Tor settings updated");
@@ -913,6 +964,18 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		}
 	}
 
+	private void disableAndReenableNetwork() {
+		connectionStatusExecutor.execute(() -> {
+			try {
+				if (state.isTorRunning()) enableNetwork(false);
+			} catch (IOException ex) {
+				logException(LOG, WARNING, ex);
+			}
+		});
+		updateConnectionStatus(networkManager.getNetworkStatus(),
+				batteryManager.isCharging());
+	}
+
 	private void updateConnectionStatus(NetworkStatus status,
 			boolean charging) {
 		connectionStatusExecutor.execute(() -> {
@@ -944,8 +1007,10 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			}
 
 			int reasonsDisabled = 0;
-			boolean enableNetwork = false, enableConnectionPadding = false;
-			List<BridgeType> bridgeTypes = emptyList();
+			boolean enableNetwork = false, enableBridges = false;
+			boolean enableConnectionPadding = false;
+			List<BridgeType> bridgeTypes =
+					circumventionProvider.getSuitableBridgeTypes(country);
 
 			if (!online) {
 				LOG.info("Disabling network, device is offline");
@@ -974,12 +1039,8 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 					enableNetwork = true;
 					if (network == PREF_TOR_NETWORK_WITH_BRIDGES ||
 							(automatic && bridgesWork)) {
-						if (ipv6Only) {
-							bridgeTypes = asList(MEEK, SNOWFLAKE);
-						} else {
-							bridgeTypes = circumventionProvider
-									.getSuitableBridgeTypes(country);
-						}
+						if (ipv6Only) bridgeTypes = singletonList(MEEK);
+						enableBridges = true;
 						if (LOG.isLoggable(INFO)) {
 							LOG.info("Using bridge types " + bridgeTypes);
 						}
@@ -999,9 +1060,9 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 
 			try {
 				if (enableNetwork) {
-					enableBridges(bridgeTypes, country);
+					enableBridges(enableBridges, bridgeTypes);
 					enableConnectionPadding(enableConnectionPadding);
-					enableIpv6(ipv6Only);
+					useIpv6(ipv6Only);
 				}
 				enableNetwork(enableNetwork);
 			} catch (IOException e) {
@@ -1011,7 +1072,6 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	}
 
 	private void enableConnectionPadding(boolean enable) throws IOException {
-		if (!state.enableConnectionPadding(enable)) return; // Unchanged
 		try {
 			controlConnection.setConf("ConnectionPadding", enable ? "1" : "0");
 		} catch (TorNotRunningException e) {
@@ -1019,11 +1079,10 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		}
 	}
 
-	private void enableIpv6(boolean enable) throws IOException {
-		if (!state.enableIpv6(enable)) return; // Unchanged
+	private void useIpv6(boolean ipv6Only) throws IOException {
 		try {
-			controlConnection.setConf("ClientUseIPv4", enable ? "0" : "1");
-			controlConnection.setConf("ClientUseIPv6", enable ? "1" : "0");
+			controlConnection.setConf("ClientUseIPv4", ipv6Only ? "0" : "1");
+			controlConnection.setConf("ClientUseIPv6", ipv6Only ? "1" : "0");
 		} catch (TorNotRunningException e) {
 			throw new RuntimeException(e);
 		}
@@ -1038,8 +1097,6 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 				stopped = false,
 				networkInitialised = false,
 				networkEnabled = false,
-				paddingEnabled = false,
-				ipv6Enabled = false,
 				bootstrapped = false,
 				circuitBuilt = false,
 				settingsChecked = false;
@@ -1047,6 +1104,13 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		@GuardedBy("this")
 		private int reasonsDisabled = 0;
 
+		/**
+		 * The number of consecutive successful (positive) or failed (negative)
+		 * connections to our own hidden service.
+		 */
+		@GuardedBy("this")
+		private int networkStability = 0;
+
 		@GuardedBy("this")
 		@Nullable
 		private ServerSocket serverSocket = null;
@@ -1054,9 +1118,6 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		@GuardedBy("this")
 		private int orConnectionsConnected = 0;
 
-		@GuardedBy("this")
-		private List<BridgeType> bridgeTypes = emptyList();
-
 		private synchronized void setStarted() {
 			started = true;
 			callback.pluginStateChanged(getState());
@@ -1077,66 +1138,28 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		}
 
 		private synchronized void setBootstrapped() {
-			boolean wasBootstrapped = bootstrapped;
 			bootstrapped = true;
-			if (!wasBootstrapped) callback.pluginStateChanged(getState());
-		}
-
-		/**
-		 * Sets the `circuitBuilt` flag and returns true if the flag has
-		 * changed.
-		 */
-		private synchronized boolean setCircuitBuilt(boolean built) {
-			if (built == circuitBuilt) return false; // Unchanged
-			circuitBuilt = built;
 			callback.pluginStateChanged(getState());
-			return true; // Changed
 		}
 
-		/**
-		 * Sets the `networkEnabled` flag and returns true if the flag has
-		 * changed.
-		 */
-		private synchronized boolean enableNetwork(boolean enable) {
-			boolean wasInitialised = networkInitialised;
-			boolean wasEnabled = networkEnabled;
+		private synchronized boolean getAndSetCircuitBuilt(boolean built) {
+			boolean old = circuitBuilt;
+			circuitBuilt = built;
+			if (built != old) callback.pluginStateChanged(getState());
+			return old;
+		}
+
+		private synchronized void enableNetwork(boolean enable) {
 			networkInitialised = true;
 			networkEnabled = enable;
 			if (!enable) circuitBuilt = false;
-			if (!wasInitialised || enable != wasEnabled) {
-				callback.pluginStateChanged(getState());
-			}
-			return enable != wasEnabled;
+			callback.pluginStateChanged(getState());
 		}
 
-		/**
-		 * Sets the `paddingEnabled` flag and returns true if the flag has
-		 * changed. Doesn't affect getState().
-		 */
-		private synchronized boolean enableConnectionPadding(boolean enable) {
-			if (enable == paddingEnabled) return false; // Unchanged
-			paddingEnabled = enable;
-			return true; // Changed
-		}
-
-		/**
-		 * Sets the `ipv6Enabled` flag and returns true if the flag has
-		 * changed. Doesn't affect getState().
-		 */
-		private synchronized boolean enableIpv6(boolean enable) {
-			if (enable == ipv6Enabled) return false; // Unchanged
-			ipv6Enabled = enable;
-			return true; // Changed
-		}
-
-		private synchronized void setReasonsDisabled(int reasons) {
-			boolean wasChecked = settingsChecked;
+		private synchronized void setReasonsDisabled(int reasonsDisabled) {
 			settingsChecked = true;
-			int oldReasons = reasonsDisabled;
-			reasonsDisabled = reasons;
-			if (!wasChecked || reasons != oldReasons) {
-				callback.pluginStateChanged(getState());
-			}
+			this.reasonsDisabled = reasonsDisabled;
+			callback.pluginStateChanged(getState());
 		}
 
 		// Doesn't affect getState()
@@ -1151,17 +1174,6 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			if (serverSocket == ss) serverSocket = null;
 		}
 
-		/**
-		 * Sets the list of bridge types being used and returns true if the
-		 * list has changed. The list is empty if bridges are disabled.
-		 * Doesn't affect getState().
-		 */
-		private synchronized boolean setBridgeTypes(List<BridgeType> types) {
-			if (types.equals(bridgeTypes)) return false; // Unchanged
-			bridgeTypes = types;
-			return true; // Changed
-		}
-
 		private synchronized State getState() {
 			if (!started || stopped || !settingsChecked) {
 				return STARTING_STOPPING;
@@ -1193,6 +1205,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			}
 			logOrConnections();
 			if (orConnectionsConnected == 0 && oldConnected != 0) {
+				resetNetworkStability();
 				callback.pluginStateChanged(getState());
 			}
 		}
@@ -1203,5 +1216,43 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 				LOG.info(orConnectionsConnected + " OR connections connected");
 			}
 		}
+
+		private synchronized boolean isNetworkStable() {
+			return networkStability >= STABLE_NETWORK_THRESHOLD;
+		}
+
+		private synchronized void onStabilityCheckSucceeded() {
+			if (networkStability <= 0) networkStability = 1;
+			else networkStability++;
+			logNetworkStability();
+		}
+
+		private synchronized void onStabilityCheckFailed() {
+			if (networkStability >= 0) networkStability = -1;
+			else networkStability--;
+			if (networkStability <= -BROKEN_NETWORK_THRESHOLD) {
+				LOG.warning("Connection to Tor appears to be broken");
+				resetNetworkStability();
+				disableAndReenableNetwork();
+			} else {
+				logNetworkStability();
+			}
+		}
+
+		private synchronized void resetNetworkStability() {
+			int old = networkStability;
+			networkStability = 0;
+			logNetworkStability();
+			if (old >= STABLE_NETWORK_THRESHOLD) {
+				callback.pollingIntervalDecreased();
+			}
+		}
+
+		@GuardedBy("this")
+		private void logNetworkStability() {
+			if (LOG.isLoggable(INFO)) {
+				LOG.info("Network stability score " + networkStability);
+			}
+		}
 	}
 }

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

@@ -6,8 +6,6 @@ import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.lifecycle.IoExecutor;
 import org.briarproject.bramble.api.network.NetworkManager;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-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.TorConstants;
 import org.briarproject.bramble.api.plugin.TorControlPort;
@@ -41,16 +39,12 @@ abstract class TorPluginFactory implements DuplexPluginFactory {
 
 	protected static final int MAX_LATENCY = 30 * 1000; // 30 seconds
 	protected 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;
 
 	protected final Executor ioExecutor, wakefulIoExecutor;
 	protected final NetworkManager networkManager;
 	protected final LocationUtils locationUtils;
 	protected final EventBus eventBus;
 	protected final SocketFactory torSocketFactory;
-	protected final BackoffFactory backoffFactory;
 	protected final ResourceProvider resourceProvider;
 	protected final CircumventionProvider circumventionProvider;
 	protected final BatteryManager batteryManager;
@@ -66,7 +60,6 @@ abstract class TorPluginFactory implements DuplexPluginFactory {
 			LocationUtils locationUtils,
 			EventBus eventBus,
 			SocketFactory torSocketFactory,
-			BackoffFactory backoffFactory,
 			ResourceProvider resourceProvider,
 			CircumventionProvider circumventionProvider,
 			BatteryManager batteryManager,
@@ -81,7 +74,6 @@ abstract class TorPluginFactory implements DuplexPluginFactory {
 		this.locationUtils = locationUtils;
 		this.eventBus = eventBus;
 		this.torSocketFactory = torSocketFactory;
-		this.backoffFactory = backoffFactory;
 		this.resourceProvider = resourceProvider;
 		this.circumventionProvider = circumventionProvider;
 		this.batteryManager = batteryManager;
@@ -95,7 +87,7 @@ abstract class TorPluginFactory implements DuplexPluginFactory {
 	@Nullable
 	abstract String getArchitectureForTorBinary();
 
-	abstract TorPlugin createPluginInstance(Backoff backoff,
+	abstract TorPlugin createPluginInstance(
 			TorRendezvousCrypto torRendezvousCrypto, PluginCallback callback,
 			String architecture);
 
@@ -122,11 +114,9 @@ abstract class TorPluginFactory implements DuplexPluginFactory {
 			LOG.info("The selected architecture for Tor is " + architecture);
 		}
 
-		Backoff backoff = backoffFactory.createBackoff(MIN_POLLING_INTERVAL,
-				MAX_POLLING_INTERVAL, BACKOFF_BASE);
 		TorRendezvousCrypto torRendezvousCrypto =
 				new TorRendezvousCryptoImpl(crypto);
-		TorPlugin plugin = createPluginInstance(backoff, torRendezvousCrypto,
+		TorPlugin plugin = createPluginInstance(torRendezvousCrypto,
 				callback, architecture);
 		eventBus.addListener(plugin);
 		return plugin;

bramble-core/src/main/java/org/briarproject/bramble/sync/DuplexOutgoingSession.java

@@ -44,14 +44,12 @@ import java.util.logging.Logger;
 import javax.annotation.Nullable;
 import javax.annotation.concurrent.ThreadSafe;
 
-import static java.lang.Boolean.TRUE;
 import static java.util.concurrent.TimeUnit.MILLISECONDS;
 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.lifecycle.LifecycleManager.LifecycleState.STOPPING;
 import static org.briarproject.bramble.api.record.Record.RECORD_HEADER_BYTES;
-import static org.briarproject.bramble.api.sync.Group.Visibility.SHARED;
 import static org.briarproject.bramble.api.sync.SyncConstants.MAX_MESSAGE_IDS;
 import static org.briarproject.bramble.api.sync.SyncConstants.MAX_MESSAGE_LENGTH;
 import static org.briarproject.bramble.api.sync.SyncConstants.SUPPORTED_VERSIONS;
@@ -234,19 +232,11 @@ class DuplexOutgoingSession implements SyncSession, EventListener {
 			ContactRemovedEvent c = (ContactRemovedEvent) e;
 			if (c.getContactId().equals(contactId)) interrupt();
 		} else if (e instanceof MessageSharedEvent) {
-			MessageSharedEvent m = (MessageSharedEvent) e;
-			// If the contact is present in the map (ie the value is not null)
-			// and the value is true, the message's group is shared with the
-			// contact and therefore the message may now be sendable
-			if (m.getGroupVisibility().get(contactId) == TRUE) {
-				generateOffer();
-			}
+			generateOffer();
 		} else if (e instanceof GroupVisibilityUpdatedEvent) {
 			GroupVisibilityUpdatedEvent g = (GroupVisibilityUpdatedEvent) e;
-			if (g.getVisibility() == SHARED &&
-					g.getAffectedContacts().contains(contactId)) {
+			if (g.getAffectedContacts().contains(contactId))
 				generateOffer();
-			}
 		} else if (e instanceof MessageRequestedEvent) {
 			if (((MessageRequestedEvent) e).getContactId().equals(contactId))
 				generateBatch();
@@ -320,8 +310,7 @@ class DuplexOutgoingSession implements SyncSession, EventListener {
 							Collection<Message> batch =
 									db.generateRequestedBatch(txn, contactId,
 											BATCH_CAPACITY, maxLatency);
-							setNextSendTime(db.getNextSendTime(txn, contactId,
-									maxLatency));
+							setNextSendTime(db.getNextSendTime(txn, contactId));
 							return batch;
 						});
 				if (LOG.isLoggable(INFO))
@@ -364,8 +353,7 @@ class DuplexOutgoingSession implements SyncSession, EventListener {
 				Offer o = db.transactionWithNullableResult(false, txn -> {
 					Offer offer = db.generateOffer(txn, contactId,
 							MAX_MESSAGE_IDS, maxLatency);
-					setNextSendTime(db.getNextSendTime(txn, contactId,
-							maxLatency));
+					setNextSendTime(db.getNextSendTime(txn, contactId));
 					return offer;
 				});
 				if (LOG.isLoggable(INFO))

bramble-core/src/main/java/org/briarproject/bramble/sync/MailboxOutgoingSession.java

@@ -7,16 +7,14 @@ import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.sync.Ack;
+import org.briarproject.bramble.api.sync.DeferredSendHandler;
 import org.briarproject.bramble.api.sync.Message;
 import org.briarproject.bramble.api.sync.MessageId;
-import org.briarproject.bramble.api.sync.OutgoingSessionRecord;
 import org.briarproject.bramble.api.sync.SyncRecordWriter;
 import org.briarproject.bramble.api.transport.StreamWriter;
 
 import java.io.IOException;
-import java.util.ArrayList;
 import java.util.Collection;
-import java.util.List;
 import java.util.logging.Logger;
 
 import javax.annotation.concurrent.ThreadSafe;
@@ -31,7 +29,7 @@ import static org.briarproject.bramble.api.sync.SyncConstants.MESSAGE_HEADER_LEN
 
 /**
  * A {@link SimplexOutgoingSession} for sending and acking messages via a
- * mailbox. The session uses a {@link OutgoingSessionRecord} to record the IDs
+ * mailbox. The session uses a {@link DeferredSendHandler} to record the IDs
  * of the messages sent and acked during the session so that they can be
  * recorded in the DB as sent or acked after the file has been successfully
  * uploaded to the mailbox.
@@ -43,7 +41,7 @@ class MailboxOutgoingSession extends SimplexOutgoingSession {
 	private static final Logger LOG =
 			getLogger(MailboxOutgoingSession.class.getName());
 
-	private final OutgoingSessionRecord sessionRecord;
+	private final DeferredSendHandler deferredSendHandler;
 	private final long initialCapacity;
 
 	MailboxOutgoingSession(DatabaseComponent db,
@@ -53,42 +51,36 @@ class MailboxOutgoingSession extends SimplexOutgoingSession {
 			long maxLatency,
 			StreamWriter streamWriter,
 			SyncRecordWriter recordWriter,
-			OutgoingSessionRecord sessionRecord,
+			DeferredSendHandler deferredSendHandler,
 			long capacity) {
 		super(db, eventBus, contactId, transportId, maxLatency, streamWriter,
 				recordWriter);
-		this.sessionRecord = sessionRecord;
+		this.deferredSendHandler = deferredSendHandler;
 		this.initialCapacity = capacity;
 	}
 
 	@Override
 	void sendAcks() throws DbException, IOException {
-		List<MessageId> idsToAck = loadMessageIdsToAck();
-		int idsSent = 0;
-		while (idsSent < idsToAck.size() && !isInterrupted()) {
-			int idsRemaining = idsToAck.size() - idsSent;
-			long capacity = getRemainingCapacity();
-			long idCapacity =
-					(capacity - RECORD_HEADER_BYTES) / MessageId.LENGTH;
-			if (idCapacity == 0) break; // Out of capacity
-			int idsInRecord = (int) min(idCapacity, MAX_MESSAGE_IDS);
-			int idsToSend = min(idsRemaining, idsInRecord);
-			List<MessageId> acked =
-					idsToAck.subList(idsSent, idsSent + idsToSend);
-			recordWriter.writeAck(new Ack(acked));
-			sessionRecord.onAckSent(acked);
+		while (!isInterrupted()) {
+			Collection<MessageId> idsToAck = loadMessageIdsToAck();
+			if (idsToAck.isEmpty()) break;
+			recordWriter.writeAck(new Ack(idsToAck));
+			deferredSendHandler.onAckSent(idsToAck);
 			LOG.info("Sent ack");
-			idsSent += idsToSend;
 		}
 	}
 
-	private List<MessageId> loadMessageIdsToAck() throws DbException {
+	private Collection<MessageId> loadMessageIdsToAck() throws DbException {
+		long idCapacity = (getRemainingCapacity() - RECORD_HEADER_BYTES)
+				/ MessageId.LENGTH;
+		if (idCapacity <= 0) return emptyList(); // Out of capacity
+		int maxMessageIds = (int) min(idCapacity, MAX_MESSAGE_IDS);
 		Collection<MessageId> ids = db.transactionWithResult(true, txn ->
-				db.getMessagesToAck(txn, contactId));
+				db.getMessagesToAck(txn, contactId, maxMessageIds));
 		if (LOG.isLoggable(INFO)) {
 			LOG.info(ids.size() + " messages to ack");
 		}
-		return new ArrayList<>(ids);
+		return ids;
 	}
 
 	private long getRemainingCapacity() {
@@ -104,7 +96,7 @@ class MailboxOutgoingSession extends SimplexOutgoingSession {
 					db.getMessageToSend(txn, contactId, m, maxLatency, false));
 			if (message == null) continue; // No longer shared
 			recordWriter.writeMessage(message);
-			sessionRecord.onMessageSent(m);
+			deferredSendHandler.onMessageSent(m);
 			LOG.info("Sent message");
 		}
 	}

bramble-core/src/main/java/org/briarproject/bramble/sync/SyncSessionFactoryImpl.java

@@ -6,7 +6,6 @@ import org.briarproject.bramble.api.db.DatabaseExecutor;
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.TransportId;
-import org.briarproject.bramble.api.sync.OutgoingSessionRecord;
 import org.briarproject.bramble.api.sync.Priority;
 import org.briarproject.bramble.api.sync.PriorityHandler;
 import org.briarproject.bramble.api.sync.SyncRecordReader;
@@ -26,8 +25,6 @@ import javax.annotation.Nullable;
 import javax.annotation.concurrent.Immutable;
 import javax.inject.Inject;
 
-import static org.briarproject.bramble.api.mailbox.MailboxConstants.MAX_FILE_PAYLOAD_BYTES;
-
 @Immutable
 @NotNullByDefault
 class SyncSessionFactoryImpl implements SyncSessionFactory {
@@ -76,18 +73,6 @@ class SyncSessionFactoryImpl implements SyncSessionFactory {
 		}
 	}
 
-	@Override
-	public SyncSession createSimplexOutgoingSession(ContactId c, TransportId t,
-			long maxLatency, StreamWriter streamWriter,
-			OutgoingSessionRecord sessionRecord) {
-		OutputStream out = streamWriter.getOutputStream();
-		SyncRecordWriter recordWriter =
-				recordWriterFactory.createRecordWriter(out);
-		return new MailboxOutgoingSession(db, eventBus, c, t, maxLatency,
-				streamWriter, recordWriter, sessionRecord,
-				MAX_FILE_PAYLOAD_BYTES);
-	}
-
 	@Override
 	public SyncSession createDuplexOutgoingSession(ContactId c, TransportId t,
 			long maxLatency, int maxIdleTime, StreamWriter streamWriter,

bramble-core/src/main/resources/bridges

@@ -11,26 +11,23 @@ d Bridge obfs4 209.148.46.65:443 74FAD13168806246602538555B5521A0383A1875 cert=s
 d Bridge obfs4 146.57.248.225:22 10A6CD36A537FCE513A322361547444B393989F0 cert=K1gDtDAIcUfeLqbstggjIw2rtgIKqdIhUlHp82XRqNSq/mtAjp1BIC9vHKJ2FAEpGssTPw iat-mode=0
 d Bridge obfs4 45.145.95.6:27015 C5B7CD6946FF10C5B3E89691A7D3F2C122D2117C cert=TD7PbUO0/0k6xYHMPW3vJxICfkMZNdkRrb63Zhl5j9dW3iRGiCx0A7mPhe5T2EDzQ35+Zw iat-mode=0
 d Bridge obfs4 51.222.13.177:80 5EDAC3B810E12B01F6FD8050D2FD3E277B289A08 cert=2uplIpLQ0q9+0qMFrK5pkaYRDOe460LL9WHBvatgkuRr/SL31wBOEupaMMJ6koRE6Ld0ew iat-mode=0
+n Bridge obfs4 46.226.107.197:10300 A38FD6BDFD902882F5F5B9B7CCC95602A20B0BC4 cert=t8tA9q2AeGlmp/dO6oW9bkY5RqqmvqjArCEM9wjJoDnk6XtnaejkF0JTA7VamdyOzcvuBg iat-mode=0
 n Bridge obfs4 185.181.11.86:443 A961609729E7FDF520B4E81F1F1B8FA1045285C3 cert=e5faG9Zk4Ni+e7z2YgGfevyKPQlMvkVGi4ublSsHYjaBovKeNXpOhbeFxzbZZoAzxAoGUQ iat-mode=0
+n Bridge obfs4 85.242.211.221:8042 A36A938DD7FDB8BACC846BA326EE0BA0D89A9252 cert=1AN6Pt1eFca3Y/WYD2TGAU3Al9cO4eouXE9SX63s66Z/ks3tVmgQ5GeXi1B5DOvx6Il7Zw iat-mode=0
+n Bridge obfs4 74.104.165.202:9002 EF432018A6AA5D970B2F84E39CD30A147030141C cert=PhppfUusY85dHGvWtGTybZ1fED4DtbHmALkNMIOIYrAz1B4xN7/2a5gyiZe1epju1BOHVg iat-mode=0
 n Bridge obfs4 93.95.226.151:41185 460B0CFFC0CF1D965F3DE064E08BA1915E7C916A cert=inluPzp5Jp5OzZar1eQb4dcQ/YlAj/v0kHAUCoCr3rmLt03+pVuVTjoH4mRy4+acXpn+Gw iat-mode=0
 n Bridge obfs4 120.29.217.52:5223 40FE3DB9800272F9CDC76422F8ED7883280EE96D cert=/71PS4l8c/XJ4DIItlH9xMqNvPFg2RUTrHvPlQWh48u5et8h/yyyjCcYphUadDsfBWpaGQ iat-mode=0
-n Bridge obfs4 185.177.207.138:8443 53716FE26F23C8C6A71A2BC5D9D8DC64747278C7 cert=6jcYVilMEzxdsWghSrQFpYYJlkkir/GPIXw/EnddUK3S8ToVpMG8u1SwMOEdEs735RrMHw iat-mode=0
-n Bridge obfs4 87.121.72.109:9002 C8081D4731C953FA4AE166946E72B29153351E34 cert=bikAqxKV6Ch5gFCBTdPI28VeShYa1ZgkLmvc7YZNLWFsFZoaCULL/3AQKjpIfvSiJs5jGQ iat-mode=0
-n Bridge obfs4 70.34.249.113:443 F441B16ABB1055794C2CE01821FC05047B2C8CFC cert=MauLNoyq8EwjY4Qe0oASYzs2hXdSjNgy+BtP9oo1naHhRsyKTtAZzeNv08RnzWjMJrTwcg iat-mode=0
-n Bridge obfs4 104.168.68.90:443 ED55B3C321E44EA7E50EF568C8A63CF75E89A58C cert=fgonxDvltTp8nmcOE9sUG94eOAALxETVVXAwnTZJLPpf7rjPuTp+abKl4VyFkxfcLRr5KQ iat-mode=0
-n Bridge obfs4 158.247.207.151:443 6170ADBBB6C1859A8E7E4416BB8AB3AF471AE47F cert=Od4izlwLnXcq7LMSOJtnZLtklaUn+X+gPcBwN7RUEkk9rqxRRYNHW7as8g6+jheDsazxAQ iat-mode=0
-n Bridge obfs4 45.142.181.131:42069 6EBCF6B02DA2B982F4080A7119D737366AFB74FA cert=9HyWH/BCwWzNirZdTQtluCgJk+gFhpOqydIuyQ1iDvpnqsAynKF+zcPE/INZFefm86UlBg iat-mode=0
-n Bridge obfs4 85.214.28.204:47111 78A36E46BB082A471848239D3F4390A8F8C6084D cert=96sr3eaUFBDu4wFVAQIfNFElh0UNuutJ/3/Fh2Vu2PHfacQ8bwfY02bwG351U8BZpLnfUQ iat-mode=0
-n Bridge obfs4 152.67.77.101:4096 B82DB9CDDF887AB8A859420E07DF298E30AF8A6E cert=21OWn3yFo+hulmQNAOtF5uwwOqWtdT5PrLhk8BG9DpOd0/k5DEkQEYPyDdXbS9nZ0E5BJA iat-mode=0
-n Bridge obfs4 82.39.132.97:6969 F505EF4C41C77FFDC0C440C122A02129FBE25823 cert=bwNWuL7UYB9aiKajE1gkffylYx/EM4FjSZxIJ0pVT/xaR21xXlIdaXw7l+EYmC4nVIh2HQ iat-mode=0
-n Bridge obfs4 185.103.252.72:443 75F15E9339FF572F88F5588D429FEA379744BC53 cert=nOZ/SaRE3L1dChvjfe0Ks/wM/F8iFhwd3g2G5zgtcLB8x+wiZRWCwjRrbbiQyb3Gh2mxRQ iat-mode=0
-n Bridge obfs4 185.177.207.13:22662 928C1E4289A01F34C8FB423FC32C0E77EE0F8736 cert=p9L6+25s8bnfkye1ZxFeAE4mAGY7DH4Gaj7dxngIIzP9BtqrHHwZXdjMK0RVIQ34C7aqZw iat-mode=2
-n Bridge obfs4 207.181.229.55:40132 37FE8D782F5DD2BAEEDAAB8257B701344676B6DD cert=f5Hbfn3ToMzH170cV8DfLly3vRynveidfOfDcbradIDtbLDX15V2yQ8eEH2CPKQJmQR2Hg iat-mode=0
+n Bridge obfs4 83.97.179.29:1199 D83068BFAA28E71DB024B786E1E803BE14257127 cert=IduGtt05tM59Xmvo0oVNWgIRgY4OGPJjFP+y2oa6RMDHQBL/GRyFOOgX70iiazNAIJNkPw iat-mode=0
+n Bridge obfs4 207.181.244.13:40132 37FE8D782F5DD2BAEEDAAB8257B701344676B6DD cert=f5Hbfn3ToMzH170cV8DfLly3vRynveidfOfDcbradIDtbLDX15V2yQ8eEH2CPKQJmQR2Hg iat-mode=0
 n Bridge obfs4 76.255.201.112:8888 96CF36C2ECCFB7376AB6BE905BECD2C2AE8AEFCD cert=+q0pjaiM0JMqHL/BKqCRD+pjflaw/S406eUDF7CnFgamvQW3l2HVLJhQ6uX9P8zff0PLGg iat-mode=0
+n Bridge obfs4 65.108.159.114:14174 E1AD374BA9F34BD98862D128AC54D40C7DC138AE cert=YMkxMSBN2OOd99AkJpFaEUyKkdqZgJt9oVJEgO1QnT37n/Vc2yR4nhx4k4VkPLfEP1f4eg iat-mode=0
+n Bridge obfs4 185.177.207.138:8443 53716FE26F23C8C6A71A2BC5D9D8DC64747278C7 cert=6jcYVilMEzxdsWghSrQFpYYJlkkir/GPIXw/EnddUK3S8ToVpMG8u1SwMOEdEs735RrMHw iat-mode=0
+n Bridge obfs4 176.123.2.253:1933 B855D141CE6C4DE0F7EA4AAED83EBA8373FA8191 cert=1rOoSaRagc6PPR//paIl+ukv1N+xWKCdBXMFxK0k/moEwH0lk5bURBrUDzIX35fVzaiicQ iat-mode=0
+n Bridge obfs4 5.252.176.61:9418 3E61130100AD827AB9CB33DAC052D9BC49A39509 cert=/aMyBPnKbQFISithD3i1KHUdpWeMpWG3SvUpq1YWCf2EQohFxQfw+646gW1knm4BI/DLRA iat-mode=0
+n Bridge obfs4 70.34.213.156:12345 BC1C79ABBAE085D305346E7A2B0E838953B4B4D3 cert=3Sk4uA3/NiAsn4ObOUzjIzARclGmkiEUrku8o8bkq4ZL+dek9uLj/d5LZ5nAXT6L9S0CZA iat-mode=0
+n Bridge obfs4 202.61.224.111:6902 A4F91299763DB925AE3BD29A0FC1A9821E5D9BAE cert=NBKm2MJ83wMvYShkqpD5RrbDtW5YpIZrFNnMw7Dj1XOM3plU60Bh4eziaQXe8fGtb8ZqKg iat-mode=0
+v Bridge 135.181.113.164:54444 74AF4CCA614C454B7D3E81FF8BACD78CEBC7D7DE
 v Bridge 92.243.15.235:9001 477EAD3C04036B48235F1F27FC91420A286A4B7F
+v Bridge 77.96.91.103:443 ED000A75B79A58F1D83A4D1675C2A9395B71BE8E
 v Bridge 213.108.108.145:17674 A39C0FE47963B6E8CFE9815549864DE544935A31
-v Bridge 185.189.195.124:8199 A1F3EE78F9C2343668E68FEB84358A4C742831A5
-v Bridge 213.196.191.96:9060 05E222E2A8C234234FE0CEB58B08A93B8FC360DB
-v Bridge 75.100.92.154:22815 465E990FA8A752DDE861EDF31E42454ACC037AB4
-m Bridge meek_lite 192.0.2.2:80 97700DFE9F483596DDA6264C4D7DF7641E1E39CE url=https://meek.azureedge.net/ front=ajax.aspnetcdn.com
-s Bridge snowflake 192.0.2.3:80 2B280B23E1107BB62ABFC40DDCC8824814F80A72
+m Bridge meek_lite 192.0.2.2:2 97700DFE9F483596DDA6264C4D7DF7641E1E39CE url=https://meek.azureedge.net/ front=ajax.aspnetcdn.com

bramble-core/src/main/resources/snowflake-params

@@ -1,4 +0,0 @@
-ZZ 1 url=https://snowflake-broker.torproject.net.global.prod.fastly.net/ front=cdn.sstatic.net ice=stun:stun.l.google.com:19302,stun:stun.voip.blackberry.com:3478,stun:stun.altar.com.pl:3478,stun:stun.antisip.com:3478,stun:stun.bluesip.net:3478,stun:stun.dus.net:3478,stun:stun.epygi.com:3478,stun:stun.sonetel.com:3478,stun:stun.sonetel.net:3478,stun:stun.stunprotocol.org:3478,stun:stun.uls.co.za:3478,stun:stun.voipgate.com:3478,stun:stun.voys.nl:3478
-ZZ 0 url=https://snowflake-broker.azureedge.net/ front=ajax.aspnetcdn.com ice=stun:stun.l.google.com:19302,stun:stun.voip.blackberry.com:3478,stun:stun.altar.com.pl:3478,stun:stun.antisip.com:3478,stun:stun.bluesip.net:3478,stun:stun.dus.net:3478,stun:stun.epygi.com:3478,stun:stun.sonetel.com:3478,stun:stun.sonetel.net:3478,stun:stun.stunprotocol.org:3478,stun:stun.uls.co.za:3478,stun:stun.voipgate.com:3478,stun:stun.voys.nl:3478
-TM 1 url=https://snowflake-broker.azureedge.net/ front=ajax.aspnetcdn.com ice=stun:206.53.159.130:3479,stun:176.119.42.11:3479,stun:94.23.17.185:3479,stun:217.74.179.29:3479,stun:83.125.8.47:3479,stun:23.253.102.137:3479,stun:52.26.251.34:3479,stun:52.26.251.34:3479,stun:18.191.223.12:3479,stun:154.73.34.8:3479,stun:185.125.180.70:3479,stun:195.35.115.37:3479
-TM 0 url=https://snowflake-broker.azureedge.net/ front=ajax.aspnetcdn.com ice=stun:206.53.159.130:3479,stun:176.119.42.11:3479,stun:94.23.17.185:3479,stun:217.74.179.29:3479,stun:83.125.8.47:3479,stun:23.253.102.137:3479,stun:52.26.251.34:3479,stun:52.26.251.34:3479,stun:18.191.223.12:3479,stun:154.73.34.8:3479,stun:185.125.180.70:3479,stun:195.35.115.37:3479

bramble-core/src/test/java/org/briarproject/bramble/connection/ConnectionRegistryImplTest.java

@@ -1,6 +1,5 @@
 package org.briarproject.bramble.connection;
 
-import org.briarproject.bramble.api.FormatException;
 import org.briarproject.bramble.api.connection.ConnectionRegistry;
 import org.briarproject.bramble.api.connection.InterruptibleConnection;
 import org.briarproject.bramble.api.contact.ContactId;
@@ -58,10 +57,6 @@ public class ConnectionRegistryImplTest extends BrambleMockTestCase {
 	private final Priority high =
 			new Priority(fromHexString("FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF"));
 
-	public ConnectionRegistryImplTest() throws FormatException {
-		// required for throws declaration
-	}
-
 	@Test
 	public void testRegisterMultipleConnections() {
 		context.checking(new Expectations() {{

bramble-core/src/test/java/org/briarproject/bramble/contact/ContactExchangeIntegrationTestComponent.java

@@ -10,8 +10,6 @@ import org.briarproject.bramble.api.identity.IdentityManager;
 import org.briarproject.bramble.api.lifecycle.IoExecutor;
 import org.briarproject.bramble.api.lifecycle.LifecycleManager;
 import org.briarproject.bramble.test.BrambleCoreIntegrationTestModule;
-import org.briarproject.bramble.test.TestDnsModule;
-import org.briarproject.bramble.test.TestSocksModule;
 
 import java.util.concurrent.Executor;
 
@@ -22,9 +20,7 @@ import dagger.Component;
 @Singleton
 @Component(modules = {
 		BrambleCoreIntegrationTestModule.class,
-		BrambleCoreModule.class,
-		TestDnsModule.class,
-		TestSocksModule.class
+		BrambleCoreModule.class
 })
 interface ContactExchangeIntegrationTestComponent
 		extends BrambleCoreIntegrationTestEagerSingletons {

bramble-core/src/test/java/org/briarproject/bramble/contact/ContactManagerImplTest.java

@@ -17,6 +17,7 @@ import org.briarproject.bramble.api.identity.LocalAuthor;
 import org.briarproject.bramble.api.transport.KeyManager;
 import org.briarproject.bramble.test.BrambleMockTestCase;
 import org.briarproject.bramble.test.DbExpectations;
+import org.junit.Before;
 import org.junit.Test;
 
 import java.util.Collection;
@@ -62,9 +63,13 @@ public class ContactManagerImplTest extends BrambleMockTestCase {
 	private final long timestamp = System.currentTimeMillis();
 	private final boolean alice = new Random().nextBoolean();
 
-	private final ContactManagerImpl contactManager =
-			new ContactManagerImpl(db, keyManager, identityManager,
-					pendingContactFactory);
+	private ContactManagerImpl contactManager;
+
+	@Before
+	public void setUp() {
+		contactManager = new ContactManagerImpl(db, keyManager,
+				identityManager, pendingContactFactory);
+	}
 
 	@Test
 	public void testAddContact() throws Exception {

bramble-core/src/test/java/org/briarproject/bramble/crypto/Blake2bDigestTest.java

@@ -1,7 +1,6 @@
 package org.briarproject.bramble.crypto;
 
 import org.bouncycastle.crypto.digests.Blake2bDigest;
-import org.briarproject.bramble.api.FormatException;
 import org.briarproject.bramble.test.BrambleTestCase;
 import org.briarproject.bramble.util.StringUtils;
 import org.junit.Test;
@@ -48,7 +47,7 @@ public class Blake2bDigestTest extends BrambleTestCase {
 	};
 
 	@Test
-	public void testDigestWithKeyedTestVectors() throws FormatException {
+	public void testDigestWithKeyedTestVectors() {
 		for (String[] keyedTestVector : KEYED_TEST_VECTORS) {
 			byte[] input = StringUtils.fromHexString(keyedTestVector[0]);
 			byte[] key = StringUtils.fromHexString(keyedTestVector[1]);
@@ -64,8 +63,7 @@ public class Blake2bDigestTest extends BrambleTestCase {
 	}
 
 	@Test
-	public void testDigestWithKeyedTestVectorsAndRandomUpdate()
-			throws FormatException {
+	public void testDigestWithKeyedTestVectorsAndRandomUpdate() {
 		Random random = new Random();
 		for (int i = 0; i < 100; i++) {
 			for (String[] keyedTestVector : KEYED_TEST_VECTORS) {
@@ -140,7 +138,7 @@ public class Blake2bDigestTest extends BrambleTestCase {
 	}
 
 	@Test
-	public void runSelfTest() throws FormatException {
+	public void runSelfTest() {
 		Blake2bDigest testDigest = new Blake2bDigest(256);
 		byte[] md = new byte[64];
 

bramble-core/src/test/java/org/briarproject/bramble/crypto/KeyAgreementTest.java

@@ -1,6 +1,5 @@
 package org.briarproject.bramble.crypto;
 
-import org.briarproject.bramble.api.FormatException;
 import org.briarproject.bramble.api.crypto.AgreementPublicKey;
 import org.briarproject.bramble.api.crypto.CryptoComponent;
 import org.briarproject.bramble.api.crypto.KeyPair;
@@ -84,7 +83,7 @@ public class KeyAgreementTest extends BrambleTestCase {
 	}
 
 	@Test
-	public void testRfc7748TestVector() throws FormatException {
+	public void testRfc7748TestVector() {
 		byte[] aPriv = parsePrivateKey(ALICE_PRIVATE);
 		byte[] aPub = fromHexString(ALICE_PUBLIC);
 		byte[] bPriv = parsePrivateKey(BOB_PRIVATE);
@@ -98,8 +97,7 @@ public class KeyAgreementTest extends BrambleTestCase {
 	}
 
 	@Test
-	public void testDerivesSameSharedSecretFromEquivalentPublicKey()
-			throws FormatException {
+	public void testDerivesSameSharedSecretFromEquivalentPublicKey() {
 		byte[] aPub = fromHexString(ALICE_PUBLIC);
 		byte[] bPriv = parsePrivateKey(BOB_PRIVATE);
 		byte[] sharedSecret = fromHexString(SHARED_SECRET);
@@ -170,7 +168,7 @@ public class KeyAgreementTest extends BrambleTestCase {
 		return crypto.deriveSharedSecret(label, publicKey, keyPair, inputs);
 	}
 
-	private byte[] parsePrivateKey(String hex) throws FormatException {
+	private byte[] parsePrivateKey(String hex) {
 		// Private keys need to be clamped because curve25519-java does the
 		// clamping at key generation time, not multiplication time
 		return AgreementKeyParser.clamp(fromHexString(hex));

bramble-core/src/test/java/org/briarproject/bramble/crypto/XSalsa20Poly1305AuthenticatedCipherTest.java

@@ -1,6 +1,5 @@
 package org.briarproject.bramble.crypto;
 
-import org.briarproject.bramble.api.FormatException;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.test.BrambleTestCase;
 import org.briarproject.bramble.util.StringUtils;
@@ -16,11 +15,11 @@ public class XSalsa20Poly1305AuthenticatedCipherTest extends BrambleTestCase {
 
 	// Test vectors from the NaCl paper
 	// http://cr.yp.to/highspeed/naclcrypto-20090310.pdf
-	private final byte[] TEST_KEY = StringUtils.fromHexString(
+	private static final byte[] TEST_KEY = StringUtils.fromHexString(
 			"1b27556473e985d462cd51197a9a46c76009549eac6474f206c4ee0844f68389");
-	private final byte[] TEST_IV = StringUtils.fromHexString(
+	private static final byte[] TEST_IV = StringUtils.fromHexString(
 			"69696ee955b62b73cd62bda875fc73d68219e0036b7a0b37");
-	private final byte[] TEST_PLAINTEXT = StringUtils.fromHexString(
+	private static final byte[] TEST_PLAINTEXT = StringUtils.fromHexString(
 					"be075fc53c81f2d5cf141316" +
 					"ebeb0c7b5228c52a4c62cbd4" +
 					"4b66849b64244ffce5ecbaaf" +
@@ -32,7 +31,7 @@ public class XSalsa20Poly1305AuthenticatedCipherTest extends BrambleTestCase {
 					"048977eb48f59ffd4924ca1c" +
 					"60902e52f0a089bc76897040" +
 					"e082f937763848645e0705");
-	private final byte[] TEST_CIPHERTEXT = StringUtils.fromHexString(
+	private static final byte[] TEST_CIPHERTEXT = StringUtils.fromHexString(
 					"f3ffc7703f9400e52a7dfb4b" +
 					"3d3305d98e993b9f48681273" +
 					"c29650ba32fc76ce48332ea7" +
@@ -47,10 +46,6 @@ public class XSalsa20Poly1305AuthenticatedCipherTest extends BrambleTestCase {
 					"a43d14a6599b1f654cb45a74" +
 					"e355a5");
 
-	public XSalsa20Poly1305AuthenticatedCipherTest() throws FormatException {
-		// required for throws declaration
-	}
-
 	@Test
 	public void testEncrypt() throws Exception {
 		SecretKey k = new SecretKey(TEST_KEY);

bramble-core/src/test/java/org/briarproject/bramble/data/BdfReaderImplTest.java

@@ -618,12 +618,11 @@ public class BdfReaderImplTest extends BrambleTestCase {
 		r.readDictionary();
 	}
 
-	private void setContents(String hex) throws FormatException {
+	private void setContents(String hex) {
 		setContents(hex, DEFAULT_MAX_BUFFER_SIZE);
 	}
 
-	private void setContents(String hex, int maxBufferSize)
-			throws FormatException {
+	private void setContents(String hex, int maxBufferSize) {
 		ByteArrayInputStream in = new ByteArrayInputStream(fromHexString(hex));
 		r = new BdfReaderImpl(in, DEFAULT_NESTED_LIMIT, maxBufferSize);
 	}

bramble-core/src/test/java/org/briarproject/bramble/data/BdfWriterImplTest.java

@@ -2,6 +2,7 @@ package org.briarproject.bramble.data;
 
 import org.briarproject.bramble.test.BrambleTestCase;
 import org.briarproject.bramble.util.StringUtils;
+import org.junit.Before;
 import org.junit.Test;
 
 import java.io.ByteArrayOutputStream;
@@ -16,8 +17,14 @@ import static org.junit.Assert.assertArrayEquals;
 
 public class BdfWriterImplTest extends BrambleTestCase {
 
-	private final ByteArrayOutputStream out = new ByteArrayOutputStream();
-	private final BdfWriterImpl w = new BdfWriterImpl(out);
+	private ByteArrayOutputStream out = null;
+	private BdfWriterImpl w = null;
+
+	@Before
+	public void setUp() {
+		out = new ByteArrayOutputStream();
+		w = new BdfWriterImpl(out);
+	}
 
 	@Test
 	public void testWriteNull() throws IOException {

bramble-core/src/test/java/org/briarproject/bramble/db/DatabaseComponentImplTest.java

@@ -70,7 +70,6 @@ import static java.util.Arrays.asList;
 import static java.util.Collections.emptyList;
 import static java.util.Collections.emptyMap;
 import static java.util.Collections.singletonList;
-import static java.util.Collections.singletonMap;
 import static java.util.concurrent.TimeUnit.HOURS;
 import static org.briarproject.bramble.api.db.DatabaseComponent.TIMER_NOT_STARTED;
 import static org.briarproject.bramble.api.record.Record.RECORD_HEADER_BYTES;
@@ -284,16 +283,12 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 					temporary, null);
 			oneOf(database).mergeMessageMetadata(txn, messageId, metadata);
 			oneOf(database).commitTransaction(txn);
-			// Broadcast events for message being added and changing state
+			// The message was added, so the listeners should be called
 			oneOf(eventBus).broadcast(with(any(MessageAddedEvent.class)));
 			oneOf(eventBus).broadcast(with(any(
 					MessageStateChangedEvent.class)));
-			// If message is shared, get group visibility and broadcast event
-			if (shared) {
-				oneOf(database).getGroupVisibility(txn, groupId);
-				will(returnValue(singletonMap(contactId, true)));
+			if (shared)
 				oneOf(eventBus).broadcast(with(any(MessageSharedEvent.class)));
-			}
 		}});
 		DatabaseComponent db = createDatabaseComponent(database, eventBus,
 				eventExecutor, shutdownManager);
@@ -308,11 +303,11 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 			throws Exception {
 		context.checking(new Expectations() {{
 			// Check whether the contact is in the DB (which it's not)
-			exactly(27).of(database).startTransaction();
+			exactly(25).of(database).startTransaction();
 			will(returnValue(txn));
-			exactly(27).of(database).containsContact(txn, contactId);
+			exactly(25).of(database).containsContact(txn, contactId);
 			will(returnValue(false));
-			exactly(27).of(database).abortTransaction(txn);
+			exactly(25).of(database).abortTransaction(txn);
 		}});
 		DatabaseComponent db = createDatabaseComponent(database, eventBus,
 				eventExecutor, shutdownManager);
@@ -326,23 +321,6 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 			// Expected
 		}
 
-		try {
-			db.transaction(true, transaction ->
-					db.containsAcksToSend(transaction, contactId));
-			fail();
-		} catch (NoSuchContactException expected) {
-			// Expected
-		}
-
-		try {
-			db.transaction(true, transaction ->
-					db.containsMessagesToSend(transaction, contactId,
-							123, true));
-			fail();
-		} catch (NoSuchContactException expected) {
-			// Expected
-		}
-
 		try {
 			db.transaction(false, transaction ->
 					db.generateAck(transaction, contactId, 123));
@@ -394,7 +372,7 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 
 		try {
 			db.transaction(true, transaction ->
-					db.getMessagesToAck(transaction, contactId));
+					db.getMessagesToAck(transaction, contactId, 123));
 			fail();
 		} catch (NoSuchContactException expected) {
 			// Expected
@@ -699,11 +677,11 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 			throws Exception {
 		context.checking(new Expectations() {{
 			// Check whether the message is in the DB (which it's not)
-			exactly(16).of(database).startTransaction();
+			exactly(15).of(database).startTransaction();
 			will(returnValue(txn));
-			exactly(16).of(database).containsMessage(txn, messageId);
+			exactly(15).of(database).containsMessage(txn, messageId);
 			will(returnValue(false));
-			exactly(16).of(database).abortTransaction(txn);
+			exactly(15).of(database).abortTransaction(txn);
 			// Allow other checks to pass
 			allowing(database).containsContact(txn, contactId);
 			will(returnValue(true));
@@ -727,14 +705,6 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 			// Expected
 		}
 
-		try {
-			db.transaction(true, transaction ->
-					db.getGroupId(transaction, messageId));
-			fail();
-		} catch (NoSuchMessageException expected) {
-			// Expected
-		}
-
 		try {
 			db.transaction(true, transaction ->
 					db.getMessage(transaction, messageId));
@@ -1409,7 +1379,14 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 			will(returnValue(txn));
 			oneOf(database).containsContact(txn, contactId);
 			will(returnValue(true));
-			oneOf(database).lowerAckFlag(txn, contactId, acked);
+			// First message is still visible to the contact - flag lowered
+			oneOf(database).containsVisibleMessage(txn, contactId, messageId);
+			will(returnValue(true));
+			// Second message is no longer visible - flag not lowered
+			oneOf(database).containsVisibleMessage(txn, contactId, messageId1);
+			will(returnValue(false));
+			oneOf(database)
+					.lowerAckFlag(txn, contactId, singletonList(messageId));
 			oneOf(database).commitTransaction(txn);
 		}});
 		DatabaseComponent db = createDatabaseComponent(database, eventBus,
@@ -1886,16 +1863,12 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 			oneOf(database).containsMessage(txn, messageId);
 			will(returnValue(true));
 			oneOf(database).getMessageDependents(txn, messageId);
-			// Broadcast events for message being added and changing state
+			// broadcast for message added event
 			oneOf(eventBus).broadcast(with(any(MessageAddedEvent.class)));
 			oneOf(eventBus).broadcast(with(any(
 					MessageStateChangedEvent.class)));
-			// If message is shared, get group visibility and broadcast event
-			if (shared) {
-				oneOf(database).getGroupVisibility(txn, groupId);
-				will(returnValue(singletonMap(contactId, true)));
+			if (shared)
 				oneOf(eventBus).broadcast(with(any(MessageSharedEvent.class)));
-			}
 			// endTransaction()
 			oneOf(database).commitTransaction(txn);
 			// close()

bramble-core/src/test/java/org/briarproject/bramble/db/JdbcDatabaseTest.java

@@ -168,7 +168,6 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		assertTrue(db.containsContact(txn, contactId));
 		assertTrue(db.containsGroup(txn, groupId));
 		assertTrue(db.containsMessage(txn, messageId));
-		assertEquals(groupId, db.getGroupId(txn, messageId));
 		assertArrayEquals(message.getBody(),
 				db.getMessage(txn, messageId).getBody());
 
@@ -379,9 +378,9 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 
 		// Initially there should be nothing to send
 		assertFalse(
-				db.containsMessagesToSend(txn, contactId, MAX_LATENCY, false));
+				db.containsAnythingToSend(txn, contactId, MAX_LATENCY, false));
 		assertFalse(
-				db.containsMessagesToSend(txn, contactId, MAX_LATENCY, true));
+				db.containsAnythingToSend(txn, contactId, MAX_LATENCY, true));
 
 		// Add some messages to ack
 		Message message1 = getMessage(groupId);
@@ -390,7 +389,10 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		db.addMessage(txn, message1, DELIVERED, true, false, contactId);
 
 		// Both message IDs should be returned
-		assertTrue(db.containsAcksToSend(txn, contactId));
+		assertTrue(
+				db.containsAnythingToSend(txn, contactId, MAX_LATENCY, false));
+		assertTrue(
+				db.containsAnythingToSend(txn, contactId, MAX_LATENCY, true));
 		Collection<MessageId> ids = db.getMessagesToAck(txn, contactId, 1234);
 		assertEquals(asList(messageId, messageId1), ids);
 
@@ -398,7 +400,10 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		db.lowerAckFlag(txn, contactId, asList(messageId, messageId1));
 
 		// No message IDs should be returned
-		assertFalse(db.containsAcksToSend(txn, contactId));
+		assertFalse(
+				db.containsAnythingToSend(txn, contactId, MAX_LATENCY, false));
+		assertFalse(
+				db.containsAnythingToSend(txn, contactId, MAX_LATENCY, true));
 		assertEquals(emptyList(), db.getMessagesToAck(txn, contactId, 1234));
 
 		// Raise the ack flag again
@@ -406,7 +411,10 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		db.raiseAckFlag(txn, contactId, messageId1);
 
 		// Both message IDs should be returned
-		assertTrue(db.containsAcksToSend(txn, contactId));
+		assertTrue(
+				db.containsAnythingToSend(txn, contactId, MAX_LATENCY, false));
+		assertTrue(
+				db.containsAnythingToSend(txn, contactId, MAX_LATENCY, true));
 		ids = db.getMessagesToAck(txn, contactId, 1234);
 		assertEquals(asList(messageId, messageId1), ids);
 
@@ -2021,51 +2029,37 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		db.addMessage(txn, message, UNKNOWN, false, false, null);
 
 		// There should be no messages to send
-		assertEquals(Long.MAX_VALUE,
-				db.getNextSendTime(txn, contactId, MAX_LATENCY));
+		assertEquals(Long.MAX_VALUE, db.getNextSendTime(txn, contactId));
 
 		// Share the group with the contact - still no messages to send
 		db.addGroupVisibility(txn, contactId, groupId, true);
-		assertEquals(Long.MAX_VALUE,
-				db.getNextSendTime(txn, contactId, MAX_LATENCY));
+		assertEquals(Long.MAX_VALUE, db.getNextSendTime(txn, contactId));
 
 		// Set the message's state to DELIVERED - still no messages to send
 		db.setMessageState(txn, messageId, DELIVERED);
-		assertEquals(Long.MAX_VALUE,
-				db.getNextSendTime(txn, contactId, MAX_LATENCY));
+		assertEquals(Long.MAX_VALUE, db.getNextSendTime(txn, contactId));
 
 		// Share the message - now it should be sendable immediately
 		db.setMessageShared(txn, messageId, true);
-		assertEquals(0, db.getNextSendTime(txn, contactId, MAX_LATENCY));
+		assertEquals(0, db.getNextSendTime(txn, contactId));
 
 		// Mark the message as requested - it should still be sendable
 		db.raiseRequestedFlag(txn, contactId, messageId);
-		assertEquals(0, db.getNextSendTime(txn, contactId, MAX_LATENCY));
+		assertEquals(0, db.getNextSendTime(txn, contactId));
 
 		// Update the message's expiry time as though we sent it - now the
 		// message should be sendable after one round-trip
-		db.updateRetransmissionData(txn, contactId, messageId, MAX_LATENCY);
-		assertEquals(now + MAX_LATENCY * 2,
-				db.getNextSendTime(txn, contactId, MAX_LATENCY));
-
-		// The message should be sendable immediately over a transport with
-		// lower latency
-		assertEquals(0L, db.getNextSendTime(txn, contactId, MAX_LATENCY - 1));
+		db.updateRetransmissionData(txn, contactId, messageId, 1000);
+		assertEquals(now + 2000, db.getNextSendTime(txn, contactId));
 
 		// Update the message's expiry time again - now it should be sendable
 		// after two round-trips
-		db.updateRetransmissionData(txn, contactId, messageId, MAX_LATENCY);
-		assertEquals(now + MAX_LATENCY * 4,
-				db.getNextSendTime(txn, contactId, MAX_LATENCY));
-
-		// The message should be sendable immediately over a transport with
-		// lower latency
-		assertEquals(0L, db.getNextSendTime(txn, contactId, MAX_LATENCY - 1));
+		db.updateRetransmissionData(txn, contactId, messageId, 1000);
+		assertEquals(now + 4000, db.getNextSendTime(txn, contactId));
 
 		// Delete the message - there should be no messages to send
 		db.deleteMessage(txn, messageId);
-		assertEquals(Long.MAX_VALUE,
-				db.getNextSendTime(txn, contactId, MAX_LATENCY));
+		assertEquals(Long.MAX_VALUE, db.getNextSendTime(txn, contactId));
 
 		db.commitTransaction(txn);
 		db.close();
@@ -2130,8 +2124,7 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		db.updateRetransmissionData(txn, contactId, messageId, MAX_LATENCY);
 
 		// The message should expire after 2 * MAX_LATENCY
-		assertEquals(now + MAX_LATENCY * 2,
-				db.getNextSendTime(txn, contactId, MAX_LATENCY));
+		assertEquals(now + MAX_LATENCY * 2, db.getNextSendTime(txn, contactId));
 
 		// Time: now + MAX_LATENCY * 2 - 1
 		// The message should not yet be sendable
@@ -2174,8 +2167,7 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		db.updateRetransmissionData(txn, contactId, messageId, MAX_LATENCY);
 
 		// The message should expire after 2 * MAX_LATENCY
-		assertEquals(now + MAX_LATENCY * 2,
-				db.getNextSendTime(txn, contactId, MAX_LATENCY));
+		assertEquals(now + MAX_LATENCY * 2, db.getNextSendTime(txn, contactId));
 
 		// The message should not be sendable via the same transport
 		ids = db.getMessagesToSend(txn, contactId, ONE_MEGABYTE, MAX_LATENCY);
@@ -2222,8 +2214,7 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		db.updateRetransmissionData(txn, contactId, messageId, MAX_LATENCY);
 
 		// The message should expire after 2 * MAX_LATENCY
-		assertEquals(now + MAX_LATENCY * 2,
-				db.getNextSendTime(txn, contactId, MAX_LATENCY));
+		assertEquals(now + MAX_LATENCY * 2, db.getNextSendTime(txn, contactId));
 
 		// Time: now + MAX_LATENCY * 2 - 1
 		// The message should not yet be sendable
@@ -2234,8 +2225,8 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		// Reset the retransmission times
 		db.resetUnackedMessagesToSend(txn, contactId);
 
-		// The message should be sendable immediately
-		assertEquals(0, db.getNextSendTime(txn, contactId, MAX_LATENCY));
+		// The message should have infinitely short expiry
+		assertEquals(0, db.getNextSendTime(txn, contactId));
 
 		// The message should be sendable
 		ids = db.getMessagesToSend(txn, contactId, ONE_MEGABYTE, MAX_LATENCY);
@@ -2588,7 +2579,7 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 	private void assertNothingToSendLazily(Database<Connection> db,
 			Connection txn) throws Exception {
 		assertFalse(
-				db.containsMessagesToSend(txn, contactId, MAX_LATENCY, false));
+				db.containsAnythingToSend(txn, contactId, MAX_LATENCY, false));
 		Collection<MessageId> ids =
 				db.getMessagesToSend(txn, contactId, ONE_MEGABYTE, MAX_LATENCY);
 		assertTrue(ids.isEmpty());
@@ -2599,7 +2590,7 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 	private void assertOneMessageToSendLazily(Database<Connection> db,
 			Connection txn) throws Exception {
 		assertTrue(
-				db.containsMessagesToSend(txn, contactId, MAX_LATENCY, false));
+				db.containsAnythingToSend(txn, contactId, MAX_LATENCY, false));
 		Collection<MessageId> ids =
 				db.getMessagesToSend(txn, contactId, ONE_MEGABYTE, MAX_LATENCY);
 		assertEquals(singletonList(messageId), ids);
@@ -2610,7 +2601,7 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 	private void assertNothingToSendEagerly(Database<Connection> db,
 			Connection txn) throws Exception {
 		assertFalse(
-				db.containsMessagesToSend(txn, contactId, MAX_LATENCY, true));
+				db.containsAnythingToSend(txn, contactId, MAX_LATENCY, true));
 		Collection<MessageId> unacked =
 				db.getUnackedMessagesToSend(txn, contactId);
 		assertTrue(unacked.isEmpty());
@@ -2620,7 +2611,7 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 	private void assertOneMessageToSendEagerly(Database<Connection> db,
 			Connection txn) throws Exception {
 		assertTrue(
-				db.containsMessagesToSend(txn, contactId, MAX_LATENCY, true));
+				db.containsAnythingToSend(txn, contactId, MAX_LATENCY, true));
 		Collection<MessageId> unacked =
 				db.getUnackedMessagesToSend(txn, contactId);
 		assertEquals(singletonList(messageId), unacked);

bramble-core/src/test/java/org/briarproject/bramble/identity/IdentityManagerImplTest.java

@@ -14,6 +14,7 @@ import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.test.BrambleMockTestCase;
 import org.briarproject.bramble.test.DbExpectations;
 import org.jmock.Expectations;
+import org.junit.Before;
 import org.junit.Test;
 
 import static java.util.Collections.singletonList;
@@ -40,8 +41,13 @@ public class IdentityManagerImplTest extends BrambleMockTestCase {
 	private final KeyPair handshakeKeyPair =
 			new KeyPair(handshakePublicKey, handshakePrivateKey);
 
-	private final IdentityManagerImpl identityManager =
-			new IdentityManagerImpl(db, crypto, authorFactory, clock);
+	private IdentityManagerImpl identityManager;
+
+	@Before
+	public void setUp() {
+		identityManager =
+				new IdentityManagerImpl(db, crypto, authorFactory, clock);
+	}
 
 	@Test
 	public void testOpenDatabaseIdentityRegistered() throws Exception {