Merge branch '2319-mailbox-version-warning' into 'master'

Show warning if own mailbox's API version is incompatible

Closes #2319

See merge request briar/briar!1651

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

@@ -2,6 +2,9 @@ package org.briarproject.bramble.api.mailbox;
 
 import org.briarproject.bramble.api.plugin.TransportId;
 
+import java.util.List;
+
+import static java.util.Collections.singletonList;
 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;
@@ -15,6 +18,27 @@ public interface MailboxConstants {
 	 */
 	TransportId ID = new TransportId("org.briarproject.bramble.mailbox");
 
+	/**
+	 * Mailbox API versions that we support as a client. This is reported to our
+	 * contacts by {@link MailboxUpdateManager}.
+	 */
+	List<MailboxVersion> CLIENT_SUPPORTS = singletonList(
+			new MailboxVersion(1, 0));
+
+	/**
+	 * The constant returned by
+	 * {@link MailboxHelper#getHighestCommonMajorVersion(List, List)}
+	 * when the server is too old to support our major version.
+	 */
+	int API_SERVER_TOO_OLD = -1;
+
+	/**
+	 * The constant returned by
+	 * {@link MailboxHelper#getHighestCommonMajorVersion(List, List)}
+	 * when we as a client are too old to support the server's major version.
+	 */
+	int API_CLIENT_TOO_OLD = -2;
+
 	/**
 	 * The maximum length of a file that can be uploaded to or downloaded from
 	 * a mailbox.

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

@@ -0,0 +1,35 @@
+package org.briarproject.bramble.api.mailbox;
+
+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;
+
+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.
+	 */
+	static int getHighestCommonMajorVersion(
+			List<MailboxVersion> client, List<MailboxVersion> server) {
+		TreeSet<Integer> clientVersions = new TreeSet<>();
+		for (MailboxVersion version : client) {
+			clientVersions.add(version.getMajor());
+		}
+		TreeSet<Integer> serverVersions = new TreeSet<>();
+		for (MailboxVersion version : server) {
+			serverVersions.add(version.getMajor());
+		}
+		for (int clientVersion : clientVersions.descendingSet()) {
+			if (serverVersions.contains(clientVersion)) return clientVersion;
+		}
+		if (clientVersions.last() < serverVersions.last()) {
+			return API_CLIENT_TOO_OLD;
+		}
+		return API_SERVER_TOO_OLD;
+	}
+
+}

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

@@ -2,10 +2,14 @@ package org.briarproject.bramble.api.mailbox;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 
+import java.util.List;
+
 import javax.annotation.concurrent.Immutable;
 
+import static org.briarproject.bramble.api.mailbox.MailboxConstants.CLIENT_SUPPORTS;
 import static org.briarproject.bramble.api.mailbox.MailboxConstants.PROBLEM_MS_SINCE_LAST_SUCCESS;
 import static org.briarproject.bramble.api.mailbox.MailboxConstants.PROBLEM_NUM_CONNECTION_FAILURES;
+import static org.briarproject.bramble.api.mailbox.MailboxHelper.getHighestCommonMajorVersion;
 
 @Immutable
 @NotNullByDefault
@@ -13,12 +17,15 @@ public class MailboxStatus {
 
 	private final long lastAttempt, lastSuccess;
 	private final int attemptsSinceSuccess;
+	private final List<MailboxVersion> serverSupports;
 
 	public MailboxStatus(long lastAttempt, long lastSuccess,
-			int attemptsSinceSuccess) {
+			int attemptsSinceSuccess,
+			List<MailboxVersion> serverSupports) {
 		this.lastAttempt = lastAttempt;
 		this.lastSuccess = lastSuccess;
 		this.attemptsSinceSuccess = attemptsSinceSuccess;
+		this.serverSupports = serverSupports;
 	}
 
 	/**
@@ -67,4 +74,13 @@ public class MailboxStatus {
 		return attemptsSinceSuccess >= PROBLEM_NUM_CONNECTION_FAILURES &&
 				(now - lastSuccess) >= PROBLEM_MS_SINCE_LAST_SUCCESS;
 	}
+
+	/**
+	 * @return a positive integer if the mailbox is compatible. Same result as
+	 * {@link MailboxHelper#getHighestCommonMajorVersion(List, List)}.
+	 */
+	public int getMailboxCompatibility() {
+		return getHighestCommonMajorVersion(CLIENT_SUPPORTS, serverSupports);
+	}
+
 }

bramble-api/src/test/java/org/briarproject/bramble/api/mailbox/MailboxHelperTest.java

@@ -0,0 +1,44 @@
+package org.briarproject.bramble.api.mailbox;
+
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Random;
+
+import static org.briarproject.bramble.api.mailbox.MailboxConstants.API_CLIENT_TOO_OLD;
+import static org.briarproject.bramble.api.mailbox.MailboxConstants.API_SERVER_TOO_OLD;
+import static org.briarproject.bramble.api.mailbox.MailboxHelper.getHighestCommonMajorVersion;
+import static org.junit.Assert.assertEquals;
+
+public class MailboxHelperTest {
+
+	private final Random random = new Random();
+
+	@Test
+	public void testGetHighestCommonMajorVersion() {
+		assertEquals(2, getHighestCommonMajorVersion(v(2), v(2)));
+		assertEquals(2, getHighestCommonMajorVersion(v(1, 2), v(2, 3, 4)));
+		assertEquals(2, getHighestCommonMajorVersion(v(2, 3, 4), v(2)));
+		assertEquals(2, getHighestCommonMajorVersion(v(2), v(2, 3, 4)));
+
+		assertEquals(API_CLIENT_TOO_OLD,
+				getHighestCommonMajorVersion(v(2), v(3, 4)));
+		assertEquals(API_CLIENT_TOO_OLD,
+				getHighestCommonMajorVersion(v(2), v(1, 3)));
+		assertEquals(API_SERVER_TOO_OLD,
+				getHighestCommonMajorVersion(v(3, 4, 5), v(2)));
+		assertEquals(API_SERVER_TOO_OLD,
+				getHighestCommonMajorVersion(v(1, 3), v(2)));
+	}
+
+	private List<MailboxVersion> v(int... ints) {
+		List<MailboxVersion> versions = new ArrayList<>(ints.length);
+		for (int v : ints) {
+			// minor versions should not matter
+			versions.add(new MailboxVersion(v, random.nextInt(42)));
+		}
+		return versions;
+	}
+
+}

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

@@ -7,7 +7,6 @@ import org.briarproject.bramble.api.mailbox.MailboxAuthToken;
 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.mailbox.MailboxUpdateManager;
 import org.briarproject.bramble.api.mailbox.MailboxVersion;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 
@@ -19,18 +18,9 @@ import java.util.List;
 import javax.annotation.Nonnull;
 import javax.annotation.concurrent.Immutable;
 
-import static java.util.Collections.singletonList;
-
 @NotNullByDefault
 interface MailboxApi {
 
-	/**
-	 * Mailbox API versions that we support as a client. This is reported to our
-	 * contacts by {@link MailboxUpdateManager}.
-	 */
-	List<MailboxVersion> CLIENT_SUPPORTS = singletonList(
-			new MailboxVersion(1, 0));
-
 	List<MailboxVersion> getServerSupports(MailboxProperties properties)
 			throws IOException, ApiException;
 

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

@@ -22,10 +22,10 @@ import javax.inject.Singleton;
 import dagger.Module;
 import dagger.Provides;
 
+import static org.briarproject.bramble.api.mailbox.MailboxConstants.CLIENT_SUPPORTS;
 import static org.briarproject.bramble.api.mailbox.MailboxUpdateManager.CLIENT_ID;
 import static org.briarproject.bramble.api.mailbox.MailboxUpdateManager.MAJOR_VERSION;
 import static org.briarproject.bramble.api.mailbox.MailboxUpdateManager.MINOR_VERSION;
-import static org.briarproject.bramble.mailbox.MailboxApi.CLIENT_SUPPORTS;
 
 @Module
 public class MailboxModule {

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

@@ -23,6 +23,7 @@ import javax.annotation.Nullable;
 import javax.annotation.concurrent.Immutable;
 import javax.inject.Inject;
 
+import static java.util.Collections.emptyList;
 import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
 
 @Immutable
@@ -60,15 +61,7 @@ class MailboxSettingsManagerImpl implements MailboxSettingsManager {
 		String onion = s.get(SETTINGS_KEY_ONION);
 		String token = s.get(SETTINGS_KEY_TOKEN);
 		if (isNullOrEmpty(onion) || isNullOrEmpty(token)) return null;
-		int[] ints = s.getIntArray(SETTINGS_KEY_SERVER_SUPPORTS);
+		List<MailboxVersion> serverSupports = parseServerSupports(s);
-		// We know we were paired, so we must have proper serverSupports
-		if (ints == null || ints.length == 0 || ints.length % 2 != 0) {
-			throw new DbException();
-		}
-		List<MailboxVersion> serverSupports = new ArrayList<>();
-		for (int i = 0; i < ints.length - 1; i += 2) {
-			serverSupports.add(new MailboxVersion(ints[i], ints[i + 1]));
-		}
 		try {
 			MailboxAuthToken tokenId = MailboxAuthToken.fromString(token);
 			return new MailboxProperties(onion, tokenId, serverSupports);
@@ -115,18 +108,28 @@ class MailboxSettingsManagerImpl implements MailboxSettingsManager {
 		long lastAttempt = s.getLong(SETTINGS_KEY_LAST_ATTEMPT, -1);
 		long lastSuccess = s.getLong(SETTINGS_KEY_LAST_SUCCESS, -1);
 		int attempts = s.getInt(SETTINGS_KEY_ATTEMPTS, 0);
-		return new MailboxStatus(lastAttempt, lastSuccess, attempts);
+		List<MailboxVersion> serverSupports;
+		try {
+			serverSupports = parseServerSupports(s);
+		} catch (DbException e) {
+			serverSupports = emptyList();
+		}
+		return new MailboxStatus(lastAttempt, lastSuccess, attempts,
+				serverSupports);
 	}
 
 	@Override
 	public void recordSuccessfulConnection(Transaction txn, long now)
 			throws DbException {
+		Settings oldSettings =
+				settingsManager.getSettings(txn, SETTINGS_NAMESPACE);
 		Settings s = new Settings();
 		s.putLong(SETTINGS_KEY_LAST_ATTEMPT, now);
 		s.putLong(SETTINGS_KEY_LAST_SUCCESS, now);
 		s.putInt(SETTINGS_KEY_ATTEMPTS, 0);
 		settingsManager.mergeSettings(txn, s, SETTINGS_NAMESPACE);
-		MailboxStatus status = new MailboxStatus(now, now, 0);
+		List<MailboxVersion> serverSupports = parseServerSupports(oldSettings);
+		MailboxStatus status = new MailboxStatus(now, now, 0, serverSupports);
 		txn.attach(new OwnMailboxConnectionStatusEvent(status));
 	}
 
@@ -141,7 +144,9 @@ class MailboxSettingsManagerImpl implements MailboxSettingsManager {
 		newSettings.putLong(SETTINGS_KEY_LAST_ATTEMPT, now);
 		newSettings.putInt(SETTINGS_KEY_ATTEMPTS, newAttempts);
 		settingsManager.mergeSettings(txn, newSettings, SETTINGS_NAMESPACE);
-		MailboxStatus status = new MailboxStatus(now, lastSuccess, newAttempts);
+		List<MailboxVersion> serverSupports = parseServerSupports(oldSettings);
+		MailboxStatus status = new MailboxStatus(now, lastSuccess, newAttempts,
+				serverSupports);
 		txn.attach(new OwnMailboxConnectionStatusEvent(status));
 		if (status.hasProblem(now)) txn.attach(new MailboxProblemEvent());
 	}
@@ -165,4 +170,19 @@ class MailboxSettingsManagerImpl implements MailboxSettingsManager {
 		if (isNullOrEmpty(filename)) return null;
 		return filename;
 	}
+
+	private List<MailboxVersion> parseServerSupports(Settings s)
+			throws DbException {
+		if (!s.containsKey(SETTINGS_KEY_SERVER_SUPPORTS)) return emptyList();
+		int[] ints = s.getIntArray(SETTINGS_KEY_SERVER_SUPPORTS);
+		// We know we were paired, so we must have proper serverSupports
+		if (ints == null || ints.length == 0 || ints.length % 2 != 0) {
+			throw new DbException();
+		}
+		List<MailboxVersion> serverSupports = new ArrayList<>();
+		for (int i = 0; i < ints.length - 1; i += 2) {
+			serverSupports.add(new MailboxVersion(ints[i], ints[i + 1]));
+		}
+		return serverSupports;
+	}
 }

bramble-core/src/test/java/org/briarproject/bramble/mailbox/ConnectivityCheckerImplTest.java

@@ -10,8 +10,8 @@ import org.junit.Test;
 
 import javax.annotation.Nonnull;
 
+import static org.briarproject.bramble.api.mailbox.MailboxConstants.CLIENT_SUPPORTS;
 import static org.briarproject.bramble.mailbox.ConnectivityCheckerImpl.CONNECTIVITY_CHECK_FRESHNESS_MS;
-import static org.briarproject.bramble.mailbox.MailboxApi.CLIENT_SUPPORTS;
 import static org.briarproject.bramble.test.TestUtils.getMailboxProperties;
 
 public class ConnectivityCheckerImplTest extends BrambleMockTestCase {

bramble-core/src/test/java/org/briarproject/bramble/mailbox/ContactMailboxConnectivityCheckerTest.java

@@ -13,7 +13,7 @@ import org.junit.Test;
 import java.io.IOException;
 import java.util.concurrent.atomic.AtomicReference;
 
-import static org.briarproject.bramble.mailbox.MailboxApi.CLIENT_SUPPORTS;
+import static org.briarproject.bramble.api.mailbox.MailboxConstants.CLIENT_SUPPORTS;
 import static org.briarproject.bramble.test.TestUtils.getMailboxProperties;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;

bramble-core/src/test/java/org/briarproject/bramble/mailbox/MailboxApiTest.java

@@ -35,7 +35,7 @@ import okio.Buffer;
 
 import static java.util.Collections.singletonList;
 import static java.util.concurrent.TimeUnit.MILLISECONDS;
-import static org.briarproject.bramble.mailbox.MailboxApi.CLIENT_SUPPORTS;
+import static org.briarproject.bramble.api.mailbox.MailboxConstants.CLIENT_SUPPORTS;
 import static org.briarproject.bramble.test.TestUtils.getContactId;
 import static org.briarproject.bramble.test.TestUtils.getMailboxProperties;
 import static org.briarproject.bramble.test.TestUtils.getRandomBytes;

bramble-core/src/test/java/org/briarproject/bramble/mailbox/MailboxSettingsManagerImplTest.java

@@ -146,12 +146,17 @@ public class MailboxSettingsManagerImplTest extends BrambleMockTestCase {
 	@Test
 	public void testRecordsSuccess() throws Exception {
 		Transaction txn = new Transaction(null, false);
+		Settings oldSettings = new Settings();
+		oldSettings
+				.putIntArray(SETTINGS_KEY_SERVER_SUPPORTS, serverSupportsInts);
 		Settings expectedSettings = new Settings();
 		expectedSettings.putLong(SETTINGS_KEY_LAST_ATTEMPT, now);
 		expectedSettings.putLong(SETTINGS_KEY_LAST_SUCCESS, now);
 		expectedSettings.putInt(SETTINGS_KEY_ATTEMPTS, 0);
 
 		context.checking(new Expectations() {{
+			oneOf(settingsManager).getSettings(txn, SETTINGS_NAMESPACE);
+			will(returnValue(oldSettings));
 			oneOf(settingsManager).mergeSettings(txn, expectedSettings,
 					SETTINGS_NAMESPACE);
 		}});

bramble-core/src/test/java/org/briarproject/bramble/mailbox/OwnMailboxConnectivityCheckerTest.java

@@ -17,7 +17,7 @@ import org.junit.Test;
 import java.io.IOException;
 import java.util.concurrent.atomic.AtomicReference;
 
-import static org.briarproject.bramble.mailbox.MailboxApi.CLIENT_SUPPORTS;
+import static org.briarproject.bramble.api.mailbox.MailboxConstants.CLIENT_SUPPORTS;
 import static org.briarproject.bramble.test.TestUtils.getMailboxProperties;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;

briar-android/src/main/java/org/briarproject/briar/android/mailbox/MailboxStatusFragment.java

@@ -36,6 +36,7 @@ import static android.view.View.VISIBLE;
 import static androidx.core.content.ContextCompat.getColor;
 import static androidx.core.widget.ImageViewCompat.setImageTintList;
 import static androidx.transition.TransitionManager.beginDelayedTransition;
+import static org.briarproject.bramble.api.mailbox.MailboxConstants.API_CLIENT_TOO_OLD;
 import static org.briarproject.briar.android.AppModule.getAndroidComponent;
 import static org.briarproject.briar.android.util.UiUtils.MIN_DATE_RESOLUTION;
 import static org.briarproject.briar.android.util.UiUtils.formatDate;
@@ -47,7 +48,6 @@ import static org.briarproject.briar.android.util.UiUtils.showFragment;
 public class MailboxStatusFragment extends Fragment {
 
 	static final String TAG = MailboxStatusFragment.class.getName();
-	private static final int NUM_FAILURES = 4;
 
 	@Inject
 	ViewModelProvider.Factory viewModelFactory;
@@ -59,8 +59,7 @@ public class MailboxStatusFragment extends Fragment {
 	private boolean showUnlinkWarning = true;
 
 	private ImageView imageView;
-	private TextView statusTitleView;
+	private TextView statusTitleView, statusMessageView, statusInfoView;
-	private TextView statusInfoView;
 	private Button wizardButton;
 	private Button unlinkButton;
 	private ProgressBar unlinkProgress;
@@ -95,6 +94,7 @@ public class MailboxStatusFragment extends Fragment {
 
 		imageView = v.findViewById(R.id.imageView);
 		statusTitleView = v.findViewById(R.id.statusTitleView);
+		statusMessageView = v.findViewById(R.id.statusMessageView);
 		statusInfoView = v.findViewById(R.id.statusInfoView);
 		viewModel.getStatus()
 				.observe(getViewLifecycleOwner(), this::onMailboxStateChanged);
@@ -133,29 +133,51 @@ public class MailboxStatusFragment extends Fragment {
 		@ColorRes int tintRes;
 		@DrawableRes int iconRes;
 		String title;
-		if (status.getAttemptsSinceSuccess() == 0) {
+		String message = null;
-			iconRes = R.drawable.ic_check_circle_outline;
+		if (status.hasProblem(System.currentTimeMillis())) {
-			title = getString(R.string.mailbox_status_connected_title);
-			tintRes = R.color.briar_brand_green;
-			showUnlinkWarning = true;
-			wizardButton.setVisibility(GONE);
-		} else if (!status.hasProblem(System.currentTimeMillis())) {
-			iconRes = R.drawable.ic_help_outline_white;
-			title = getString(R.string.mailbox_status_problem_title);
-			tintRes = R.color.briar_orange_500;
-			showUnlinkWarning = false;
-			wizardButton.setVisibility(VISIBLE);
-		} else {
 			tintRes = R.color.briar_red_500;
 			title = getString(R.string.mailbox_status_failure_title);
 			iconRes = R.drawable.alerts_and_states_error;
 			showUnlinkWarning = false;
 			wizardButton.setVisibility(VISIBLE);
+		} else if (status.getAttemptsSinceSuccess() > 0) {
+			iconRes = R.drawable.ic_help_outline_white;
+			title = getString(R.string.mailbox_status_problem_title);
+			tintRes = R.color.briar_orange_500;
+			showUnlinkWarning = false;
+			wizardButton.setVisibility(VISIBLE);
+		} else if (status.getMailboxCompatibility() < 0) {
+			tintRes = R.color.briar_red_500;
+			if (status.getMailboxCompatibility() == API_CLIENT_TOO_OLD) {
+				title = getString(R.string.mailbox_status_app_too_old_title);
+				message =
+						getString(R.string.mailbox_status_app_too_old_message);
+			} else {
+				title = getString(
+						R.string.mailbox_status_mailbox_too_old_title);
+				message = getString(
+						R.string.mailbox_status_mailbox_too_old_message);
+			}
+			iconRes = R.drawable.alerts_and_states_error;
+			showUnlinkWarning = true;
+			wizardButton.setVisibility(GONE);
+		} else {
+			iconRes = R.drawable.ic_check_circle_outline;
+			title = getString(R.string.mailbox_status_connected_title);
+			tintRes = R.color.briar_brand_green;
+			showUnlinkWarning = true;
+			wizardButton.setVisibility(GONE);
 		}
 		imageView.setImageResource(iconRes);
 		int color = getColor(requireContext(), tintRes);
 		setImageTintList(imageView, ColorStateList.valueOf(color));
 		statusTitleView.setText(title);
+		if (message == null) {
+			statusMessageView.setVisibility(GONE);
+		} else {
+			statusMessageView.setVisibility(VISIBLE);
+			statusMessageView.setText(message);
+		}
 
 		long lastSuccess = status.getTimeOfLastSuccess();
 		String lastConnectionText;

briar-android/src/main/java/org/briarproject/briar/android/mailbox/MailboxViewModel.java

@@ -208,16 +208,12 @@ class MailboxViewModel extends DbViewModel
 
 	LiveData<Boolean> checkConnection() {
 		MutableLiveData<Boolean> liveData = new MutableLiveData<>();
-		checkConnection(success -> {
+		checkConnection(liveData::postValue);
-			liveData.postValue(success);
-			if (!success) onConnectionCheckFailure();
-		});
 		return liveData;
 	}
 
 	void checkConnectionFromWizard() {
 		checkConnection(success -> {
-			if (!success) onConnectionCheckFailure();
 			boolean isOnline = isTorActive();
 			// make UI move back to status fragment by changing pairingState
 			pairingState.postEvent(new MailboxState.IsPaired(isOnline));
@@ -234,15 +230,6 @@ class MailboxViewModel extends DbViewModel
 		});
 	}
 
-	private void onConnectionCheckFailure() {
-		MailboxStatus lastStatus = status.getValue();
-		long lastSuccess = lastStatus == null ?
-				-1 : lastStatus.getTimeOfLastSuccess();
-		long now = System.currentTimeMillis();
-		// force failure screen
-		status.postValue(new MailboxStatus(now, lastSuccess, 999));
-	}
-
 	@UiThread
 	void unlink() {
 		ioExecutor.execute(() -> {

briar-android/src/main/res/layout/fragment_mailbox_status.xml

@@ -31,12 +31,29 @@
 		android:gravity="center"
 		android:textAppearance="@style/TextAppearance.MaterialComponents.Headline6"
 		app:layout_constrainedWidth="true"
-		app:layout_constraintBottom_toTopOf="@+id/checkButton"
+		app:layout_constraintBottom_toTopOf="@+id/statusMessageView"
 		app:layout_constraintEnd_toEndOf="parent"
 		app:layout_constraintStart_toStartOf="parent"
 		app:layout_constraintTop_toBottomOf="@+id/imageView"
 		tools:text="@string/mailbox_status_problem_title" />
 
+	<TextView
+		android:id="@+id/statusMessageView"
+		android:layout_width="wrap_content"
+		android:layout_height="wrap_content"
+		android:layout_marginHorizontal="16dp"
+		android:layout_marginBottom="16dp"
+		android:gravity="center"
+		android:textAppearance="@style/TextAppearance.MaterialComponents.Body1"
+		android:visibility="gone"
+		app:layout_constrainedWidth="true"
+		app:layout_constraintBottom_toTopOf="@+id/checkButton"
+		app:layout_constraintEnd_toEndOf="parent"
+		app:layout_constraintStart_toStartOf="parent"
+		app:layout_constraintTop_toBottomOf="@+id/statusTitleView"
+		tools:text="@string/mailbox_status_mailbox_too_old_message"
+		tools:visibility="visible" />
+
 	<org.briarproject.briar.android.view.BriarButton
 		android:id="@+id/checkButton"
 		android:layout_width="wrap_content"
@@ -46,7 +63,7 @@
 		app:layout_constraintBottom_toTopOf="@+id/statusInfoView"
 		app:layout_constraintEnd_toEndOf="parent"
 		app:layout_constraintStart_toStartOf="parent"
-		app:layout_constraintTop_toBottomOf="@+id/statusTitleView"
+		app:layout_constraintTop_toBottomOf="@+id/statusMessageView"
 		app:text="@string/mailbox_status_check_button" />
 
 	<TextView

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

@@ -640,6 +640,10 @@
 	<string name="mailbox_status_connected_title">Mailbox is running</string>
 	<string name="mailbox_status_problem_title">Briar is having trouble connecting to the Mailbox</string>
 	<string name="mailbox_status_failure_title">Mailbox is unavailable</string>
+	<string name="mailbox_status_app_too_old_title">Briar is too old</string>
+	<string name="mailbox_status_app_too_old_message">Update Briar to the latest version of the app and try again.</string>
+	<string name="mailbox_status_mailbox_too_old_title">Mailbox is too old</string>
+	<string name="mailbox_status_mailbox_too_old_message">Update your Mailbox to the latest version of the app and try again.</string>
 	<string name="mailbox_status_check_button">Check Connection</string>
 	<!-- Example for string substitution: Last connection: 3min ago-->
 	<string name="mailbox_status_connected_info">Last connection: %s</string>