cmd/tailscale, tailscale/ipn: fix alway-on VPN (#168)

=If a ConnectEvent is received before the first notification, (as happens when a connection is attempted due to always-on after device reboot) create state.Prefs.
-Create an intent to start the VPN worker in the case of an always-on intent received on device reboot
-Rename onConnect channel to onVPNRequested, since this isn't doing the actual connecting

Fixes tailscale/tailscale#2481

Signed-off-by: kari-ts <kari@tailscale.com>

android/src/main/java/com/tailscale/ipn/App.java

@@ -138,13 +138,13 @@ public class App extends Application {
 
 	public void startVPN() {
 		Intent intent = new Intent(this, IPNService.class);
-		intent.setAction(IPNService.ACTION_CONNECT);
+		intent.setAction(IPNService.ACTION_REQUEST_VPN);
 		startService(intent);
 	}
 
 	public void stopVPN() {
 		Intent intent = new Intent(this, IPNService.class);
-		intent.setAction(IPNService.ACTION_DISCONNECT);
+		intent.setAction(IPNService.ACTION_STOP_VPN);
 		startService(intent);
 	}
 

android/src/main/java/com/tailscale/ipn/IPNService.java

@@ -10,6 +10,8 @@ import android.content.Intent;
 import android.content.pm.PackageManager;
 import android.net.VpnService;
 import android.system.OsConstants;
+import androidx.work.WorkManager;
+import androidx.work.OneTimeWorkRequest;
 
 import org.gioui.GioActivity;
 
@@ -17,19 +19,29 @@ import androidx.core.app.NotificationCompat;
 import androidx.core.app.NotificationManagerCompat;
 
 public class IPNService extends VpnService {
-	public static final String ACTION_CONNECT = "com.tailscale.ipn.CONNECT";
-	public static final String ACTION_DISCONNECT = "com.tailscale.ipn.DISCONNECT";
+	public static final String ACTION_REQUEST_VPN = "com.tailscale.ipn.REQUEST_VPN";
+	public static final String ACTION_STOP_VPN = "com.tailscale.ipn.STOP_VPN";
 
 	@Override public int onStartCommand(Intent intent, int flags, int startId) {
-		if (intent != null && ACTION_DISCONNECT.equals(intent.getAction())) {
+		if (intent != null && ACTION_STOP_VPN.equals(intent.getAction())) {
 			((App)getApplicationContext()).autoConnect = false;
 			close();
 			return START_NOT_STICKY;
+		} 
+		if (intent != null && "android.net.VpnService".equals(intent.getAction())) {
+			// Start VPN and connect to it due to Always-on VPN
+			Intent i = new Intent(IPNReceiver.INTENT_CONNECT_VPN);
+			i.setPackage(getPackageName());
+			i.setClass(getApplicationContext(), com.tailscale.ipn.IPNReceiver.class);
+			sendBroadcast(i);
+			requestVPN();
+			connect();
+			return START_STICKY;
 		}
-		connect();
+		requestVPN();
 		App app = ((App)getApplicationContext());
 		if (app.vpnReady && app.autoConnect) {
-			directConnect();
+			connect();
 		}
 		return START_STICKY;
 	}
@@ -119,8 +131,8 @@ public class IPNService extends VpnService {
 		startForeground(App.STATUS_NOTIFICATION_ID, builder.build());
 	}
 
-	private native void connect();
-	private native void disconnect();
+	private native void requestVPN();
 
-	public native void directConnect();
+	private native void disconnect();
+	private native void connect();
 }

cmd/tailscale/callbacks.go

@@ -24,9 +24,9 @@ var (
 	// onVPNRevoked is notified whenever the VPN service is revoked.
 	onVPNRevoked = make(chan struct{}, 1)
 
-	// onConnect receives global IPNService references when
+	// onVPNRequested receives global IPNService references when
 	// a VPN connection is requested.
-	onConnect = make(chan jni.Object)
+	onVPNRequested = make(chan jni.Object)
 	// onDisconnect receives global IPNService references when
 	// disconnecting.
 	onDisconnect = make(chan jni.Object)
@@ -90,14 +90,14 @@ func notifyVPNClosed() {
 	}
 }
 
-//export Java_com_tailscale_ipn_IPNService_connect
-func Java_com_tailscale_ipn_IPNService_connect(env *C.JNIEnv, this C.jobject) {
+//export Java_com_tailscale_ipn_IPNService_requestVPN
+func Java_com_tailscale_ipn_IPNService_requestVPN(env *C.JNIEnv, this C.jobject) {
 	jenv := (*jni.Env)(unsafe.Pointer(env))
-	onConnect <- jni.NewGlobalRef(jenv, jni.Object(this))
+	onVPNRequested <- jni.NewGlobalRef(jenv, jni.Object(this))
 }
 
-//export Java_com_tailscale_ipn_IPNService_directConnect
-func Java_com_tailscale_ipn_IPNService_directConnect(env *C.JNIEnv, this C.jobject) {
+//export Java_com_tailscale_ipn_IPNService_connect
+func Java_com_tailscale_ipn_IPNService_connect(env *C.JNIEnv, this C.jobject) {
 	requestBackend(ConnectEvent{Enable: true})
 }
 

cmd/tailscale/main.go

@@ -493,6 +493,12 @@ func (a *App) runBackend(ctx context.Context) error {
 			case LogoutEvent:
 				go a.localAPI.Logout(ctx, a.backend)
 			case ConnectEvent:
+				first := state.Prefs == nil
+				// A ConnectEvent might be sent before the first notification
+				// arrives, such as in the case of Always-on VPN.
+				if first {
+					state.Prefs = ipn.NewPrefs()
+				}
 				state.Prefs.WantRunning = e.Enable
 				go b.backend.SetPrefs(state.Prefs)
 			case RouteAllEvent:
@@ -504,7 +510,7 @@ func (a *App) runBackend(ctx context.Context) error {
 					a.updateNotification(service, state.State, state.ExitStatus, state.Exit)
 				}
 			}
-		case s := <-onConnect:
+		case s := <-onVPNRequested:
 			jni.Do(a.jvm, func(env *jni.Env) error {
 				if jni.IsSameObject(env, s, service) {
 					// We already have a reference.
@@ -535,7 +541,7 @@ func (a *App) runBackend(ctx context.Context) error {
 						return nil // even on error. see big TODO above.
 					})
 				})
-				log.Printf("onConnect: rebind required")
+				log.Printf("onVPNRequested: rebind required")
 				// TODO(catzkorn): When we start the android application
 				// we bind sockets before we have access to the VpnService.protect()
 				// function which is needed to avoid routing loops. When we activate