Server rotation fix

android/app/src/main/kotlin/org/getlantern/lantern/handler/MethodHandler.kt

@@ -36,6 +36,7 @@ enum class Methods(val method: String) {
     Stop("stopVPN"),
     ConnectToServer("connectToServer"),
     IsVpnConnected("isVPNConnected"),
+    IsTagAvailable("isTagAvailable"),
 
     //Payment methods
     StripeSubscription("stripeSubscription"),
@@ -195,6 +196,23 @@ class MethodHandler : FlutterPlugin,
                 }
             }
 
+            Methods.IsTagAvailable.method -> {
+                scope.launch {
+                    try {
+                        val tag = call.arguments as? String
+                            ?: throw IllegalArgumentException("Missing or invalid tag")
+                        val available = Mobile.isTagAvailable(tag)
+                        withContext(Dispatchers.Main) {
+                            result.success(available)
+                        }
+                    } catch (e: Throwable) {
+                        withContext(Dispatchers.Main) {
+                            result.error("tag_check_failed", e.localizedMessage ?: "Error", e)
+                        }
+                    }
+                }
+            }
+
             Methods.IsVpnConnected.method -> {
                 scope.launch {
                     runCatching {

ios/Runner/Handlers/MethodHandler.swift

@@ -32,6 +32,12 @@ class MethodHandler {
       case "startVPN":
         self.startVPN(result: result)
 
+      case "isTagAvailable":
+        guard let tag: String = self.decodeValue(from: call.arguments, result: result) else {
+          return
+        }
+        self.isTagAvailable(result: result, tag: tag)
+
       case "connectToServer":
         guard let data = self.decodeDict(from: call.arguments, result: result) else { return }
         self.connectToServer(result: result, data: data)
@@ -301,6 +307,11 @@ class MethodHandler {
     }
   }
 
+  private func isTagAvailable(result: @escaping FlutterResult, tag: String) {
+    let available = MobileIsTagAvailable(tag)
+    result(available)
+  }
+
   private func connectToServer(result: @escaping FlutterResult, data: [String: Any]) {
     Task {
       do {

lantern-core/ffi/ffi.go

@@ -277,6 +277,30 @@ func getAutoLocation() *C.char {
 	return C.CString(string(jsonBytes))
 }
 
+// isTagAvailable checks if a server with the given tag exists in the server list.
+// Returns "true" if found, "false" if not found, or "true" when the check cannot be
+// performed (fail-open: allows connection attempts to proceed normally).
+//
+//export isTagAvailable
+func isTagAvailable(_tag *C.char) *C.char {
+	tag := C.GoString(_tag)
+	c, errStr := requireCore()
+	if errStr != nil {
+		slog.Warn("Unable to check tag availability (core not ready), assuming available", "tag", tag)
+		C.free(unsafe.Pointer(errStr))
+		return C.CString("true")
+	}
+	_, found, err := c.GetServerByTagJSON(tag)
+	if err != nil {
+		slog.Warn("Error checking tag availability, assuming available", "tag", tag, "error", err)
+		return C.CString("true")
+	}
+	if found {
+		return C.CString("true")
+	}
+	return C.CString("false")
+}
+
 // startAutoLocationListener starts the auto location listener.
 //
 //export startAutoLocationListener

lantern-core/mobile/mobile.go

@@ -180,6 +180,21 @@ func CloseIPC() error {
 	return vpn_tunnel.CloseIPC()
 }
 
+// IsTagAvailable checks if a server with the given tag exists in the server list.
+// Returns true if the tag is found. Returns true when the check cannot be performed
+// (fail-open: allows connection attempts to proceed normally).
+func IsTagAvailable(tag string) bool {
+	found, err := withCoreR(func(c lanterncore.Core) (bool, error) {
+		_, ok, err := c.GetServerByTagJSON(tag)
+		return ok, err
+	})
+	if err != nil {
+		slog.Warn("Unable to check tag availability, assuming available", "tag", tag, "error", err)
+		return true
+	}
+	return found
+}
+
 // ConnectToServer connects to a server using the provided location type and tag.
 // It works with private servers and lantern location servers.
 func ConnectToServer(locationType, tag string, platIfce utils.PlatformInterface, options *utils.Opts) error {

lantern-core/vpn_tunnel/vpn_tunnel.go

@@ -35,7 +35,7 @@ func StartVPN(platform rvpn.PlatformInterface, opts *utils.Opts) error {
 	}
 	// it should use InternalTagLantern so it will connect to best lantern server by default.
 	// if you want to connect to user server, use ConnectToServer with InternalTagUser
-	err := vpn.QuickConnect("", platform)
+	err := vpn.AutoConnect("")
 	if err != nil {
 		return fmt.Errorf("failed to start VPN: %w", err)
 	}

lib/features/vpn/provider/vpn_notifier.dart

@@ -18,45 +18,42 @@ class VpnNotifier extends _$VpnNotifier {
   @override
   VPNStatus build() {
     ref.read(lanternServiceProvider).isVPNConnected();
-    ref.listen(
-      vPNStatusProvider,
-      (previous, next) {
-        final previousStatus = previous?.value?.status;
-        final nextStatus = next.value!.status;
+    ref.listen(vPNStatusProvider, (previous, next) {
+      final previousStatus = previous?.value?.status;
+      final nextStatus = next.value!.status;
 
-        if (previous != null &&
-            previous.value != null &&
-            previousStatus != nextStatus) {
-          if (previousStatus != VPNStatus.connecting &&
-              nextStatus == VPNStatus.disconnected) {
-            sl<NotificationService>().showNotification(
-              id: NotificationEvent.vpnDisconnected.id,
-              title: 'app_name'.i18n,
-              body: 'vpn_disconnected'.i18n,
-            );
-          } else if (nextStatus == VPNStatus.connected) {
-            if (PlatformUtils.isMobile) {
-              HapticFeedback.mediumImpact();
-            }
+      if (previous != null &&
+          previous.value != null &&
+          previousStatus != nextStatus) {
+        if (previousStatus != VPNStatus.connecting &&
+            nextStatus == VPNStatus.disconnected) {
+          sl<NotificationService>().showNotification(
+            id: NotificationEvent.vpnDisconnected.id,
+            title: 'app_name'.i18n,
+            body: 'vpn_disconnected'.i18n,
+          );
+        } else if (nextStatus == VPNStatus.connected) {
+          if (PlatformUtils.isMobile) {
+            HapticFeedback.mediumImpact();
+          }
 
-            /// Mark successful connection in app settings
-            ref.read(appSettingProvider.notifier).setSuccessfulConnection(true);
+          /// Mark successful connection in app settings
+          ref.read(appSettingProvider.notifier).setSuccessfulConnection(true);
 
-            // Server location is updated via the "server-location" push event
-            // from the Go side (handled by AppEventNotifier), not by polling
-            // getAutoServerLocation here. This avoids a race where the NE
-            // reports "connected" before the Go tunnel is fully ready.
+          // Server location is updated via the "server-location" push event
+          // from the Go side (handled by AppEventNotifier), not by polling
+          // getAutoServerLocation here. This avoids a race where the NE
+          // reports "connected" before the Go tunnel is fully ready.
 
-            sl<NotificationService>().showNotification(
-              id: NotificationEvent.vpnConnected.id,
-              title: 'app_name'.i18n,
-              body: 'vpn_connected'.i18n,
-            );
-          }
+          sl<NotificationService>().showNotification(
+            id: NotificationEvent.vpnConnected.id,
+            title: 'app_name'.i18n,
+            body: 'vpn_connected'.i18n,
+          );
         }
-        state = nextStatus;
-      },
-    );
+      }
+      state = nextStatus;
+    });
     return VPNStatus.disconnected;
   }
 
@@ -81,14 +78,17 @@ class VpnNotifier extends _$VpnNotifier {
     final type = serverLocation.serverType.toServerLocationType;
     if (type == ServerLocationType.auto || force) {
       appLogger.debug(
-          'Got server location with type auto or force is true, starting VPN with auto');
+        'Got server location with type auto or force is true, starting VPN with auto',
+      );
       return lantern.startVPN();
     }
 
     final tag = serverLocation.serverName;
     final tagAvailable = await lantern.isTagAvailable(tag);
     if (!tagAvailable) {
-      appLogger.debug('Server tag "$tag" not available, falling back to auto VPN');
+      appLogger.debug(
+        'Server tag "$tag" not available, falling back to auto VPN',
+      );
       return lantern.startVPN();
     }
     return connectToServer(type, tag);
@@ -97,7 +97,9 @@ class VpnNotifier extends _$VpnNotifier {
   /// Connects to a specific server location.
   /// it supports lantern locations and private servers.
   Future<Either<Failure, String>> connectToServer(
-      ServerLocationType location, String tag) async {
+    ServerLocationType location,
+    String tag,
+  ) async {
     appLogger.debug("Connecting to server: $location with tag: $tag");
     final result = await ref
         .read(lanternServiceProvider)

lib/lantern/lantern_ffi_service.dart

@@ -192,7 +192,8 @@ class LanternFFIService implements LanternCoreService {
       final dataDir = await AppStorageUtils.getAppDirectory();
       final logDir = await AppStorageUtils.getAppLogDirectory();
       appLogger.info(
-          "Radiance configuration - env: $env, dataDir: ${dataDir.path}, logDir: $logDir, telemetryConsent: $consent");
+        "Radiance configuration - env: $env, dataDir: ${dataDir.path}, logDir: $logDir, telemetryConsent: $consent",
+      );
 
       final dataDirPtr = dataDir.path.toCharPtr;
       final logDirPtr = logDir.toCharPtr;
@@ -218,10 +219,7 @@ class LanternFFIService implements LanternCoreService {
 
       checkAPIError(result);
       if (result != 'ok' && result != 'true') {
-        throw PlatformException(
-          code: 'radiance_setup_failed',
-          message: result,
-        );
+        throw PlatformException(code: 'radiance_setup_failed', message: result);
       }
       return right(unit);
     } catch (e, st) {
@@ -340,8 +338,9 @@ class LanternFFIService implements LanternCoreService {
       });
       checkAPIError(enabledJson);
 
-      final enabledKeys =
-          (jsonDecode(enabledJson) as List).cast<String>().toSet();
+      final enabledKeys = (jsonDecode(enabledJson) as List)
+          .cast<String>()
+          .toSet();
 
       final decoded = jsonDecode(jsonApps) as List<dynamic>;
       final rawApps = decoded.cast<Map<String, dynamic>>();
@@ -429,7 +428,8 @@ class LanternFFIService implements LanternCoreService {
       return left(
         Failure(
           error: result['error'] ?? 'Unknown error',
-          localizedErrorMessage: result['localizedErrorMessage'] ??
+          localizedErrorMessage:
+              result['localizedErrorMessage'] ??
               result['error'] ??
               'Unknown error',
         ),
@@ -525,8 +525,9 @@ class LanternFFIService implements LanternCoreService {
       return left(
         Failure(
           error: e.toString(),
-          localizedErrorMessage:
-              (e is Exception) ? e.localizedDescription : e.toString(),
+          localizedErrorMessage: (e is Exception)
+              ? e.localizedDescription
+              : e.toString(),
         ),
       );
     } finally {
@@ -623,11 +624,28 @@ class LanternFFIService implements LanternCoreService {
   Future<bool> isTagAvailable(String tag) async {
     try {
       final result = await runInBackground<String>(() async {
-        return _ffiService.isTagAvailable(tag.toCharPtr).toDartString();
+        final tagPtr = tag.toCharPtr;
+        try {
+          final resultPtr = _ffiService.isTagAvailable(tagPtr);
+          if (resultPtr == nullptr) {
+            return 'true';
+          }
+          try {
+            return resultPtr.toDartString();
+          } finally {
+            _ffiService.freeCString(resultPtr);
+          }
+        } finally {
+          malloc.free(tagPtr);
+        }
       });
       return result == 'true';
     } catch (e, st) {
-      appLogger.error('Error checking tag availability, assuming available', e, st);
+      appLogger.error(
+        'Error checking tag availability, assuming available',
+        e,
+        st,
+      );
       return true;
     }
   }
@@ -1253,19 +1271,21 @@ class LanternFFIService implements LanternCoreService {
   }
 
   @override
-  Future<Either<Failure, Unit>> addServerBasedOnURLs(
-      {required String urls,
-      required bool skipCertVerification,
-      required String serverName}) async {
+  Future<Either<Failure, Unit>> addServerBasedOnURLs({
+    required String urls,
+    required bool skipCertVerification,
+    required String serverName,
+  }) async {
     try {
-      final result = await runInBackground<String>(
-        () async {
-          return _ffiService
-              .addServerBasedOnURLs(urls.toCharPtr,
-                  skipCertVerification ? 1 : 0, serverName.toCharPtr)
-              .toDartString();
-        },
-      );
+      final result = await runInBackground<String>(() async {
+        return _ffiService
+            .addServerBasedOnURLs(
+              urls.toCharPtr,
+              skipCertVerification ? 1 : 0,
+              serverName.toCharPtr,
+            )
+            .toDartString();
+      });
       checkAPIError(result);
       return Right(unit);
     } catch (e, stackTrace) {
@@ -1275,11 +1295,12 @@ class LanternFFIService implements LanternCoreService {
   }
 
   @override
-  Future<Either<Failure, String>> inviteToServerManagerInstance(
-      {required String ip,
-      required String port,
-      required String accessToken,
-      required String inviteName}) async {
+  Future<Either<Failure, String>> inviteToServerManagerInstance({
+    required String ip,
+    required String port,
+    required String accessToken,
+    required String inviteName,
+  }) async {
     try {
       final result = await runInBackground<String>(() async {
         return _ffiService

lib/lantern/lantern_generated_bindings.dart

@@ -2602,6 +2602,19 @@ class LanternBindings {
   late final _getAutoLocation =
       _getAutoLocationPtr.asFunction<ffi.Pointer<ffi.Char> Function()>();
 
+  ffi.Pointer<ffi.Char> isTagAvailable(
+    ffi.Pointer<ffi.Char> _tag,
+  ) {
+    return _isTagAvailable(_tag);
+  }
+
+  late final _isTagAvailablePtr = _lookup<
+      ffi.NativeFunction<
+          ffi.Pointer<ffi.Char> Function(
+              ffi.Pointer<ffi.Char>)>>('isTagAvailable');
+  late final _isTagAvailable = _isTagAvailablePtr
+      .asFunction<ffi.Pointer<ffi.Char> Function(ffi.Pointer<ffi.Char>)>();
+
   ffi.Pointer<ffi.Char> startAutoLocationListener() {
     return _startAutoLocationListener();
   }