IPNReceiver: Add intents to connect and disconnect VPN (#84)

* IPNReceiver: Add intents to connect and disconnect VPN

Added a new class IPNReceiver to listen to intents silently and connect and disconnect the VPN
Also removed unneeded comment

Fixes: https://github.com/tailscale/tailscale/issues/3547

Signed-off-by: Brett Jenkins <brett@brettjenkins.co.uk>

android/src/main/AndroidManifest.xml

@@ -55,6 +55,13 @@
 				<data android:mimeType="video/*" />
 			</intent-filter>
 		</activity>
+		<receiver android:name="IPNReceiver"
+			android:exported="true">
+			<intent-filter>
+				<action android:name="com.tailscale.ipn.CONNECT_VPN" />
+				<action android:name="com.tailscale.ipn.DISCONNECT_VPN" />
+			</intent-filter>
+		</receiver>
 		<service android:name=".IPNService"
 			android:permission="android.permission.BIND_VPN_SERVICE"
 			android:exported="false">

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

@@ -0,0 +1,20 @@
+package com.tailscale.ipn;
+
+import android.content.BroadcastReceiver;
+import android.content.Context;
+import android.content.Intent;
+
+public class IPNReceiver extends BroadcastReceiver {
+
+    @Override
+    public void onReceive(Context context, Intent intent) {
+        if (intent.getAction() == "com.tailscale.ipn.CONNECT_VPN") {
+            connect();
+        } else if (intent.getAction() == "com.tailscale.ipn.DISCONNECT_VPN") {
+            disconnect();
+        }
+    }
+
+    private native void connect();
+    private native void disconnect();
+}

cmd/tailscale/callbacks.go

@@ -102,6 +102,16 @@ func Java_com_tailscale_ipn_IPNService_disconnect(env *C.JNIEnv, this C.jobject)
 	onDisconnect <- jni.NewGlobalRef(jenv, jni.Object(this))
 }
 
+//export Java_com_tailscale_ipn_IPNReceiver_connect
+func Java_com_tailscale_ipn_IPNReceiver_connect(env *C.JNIEnv, this C.jobject) {
+    requestBackend(ConnectEvent{Enable: true})
+}
+
+//export Java_com_tailscale_ipn_IPNReceiver_disconnect
+func Java_com_tailscale_ipn_IPNReceiver_disconnect(env *C.JNIEnv, this C.jobject) {
+    requestBackend(ConnectEvent{Enable: false})
+}
+
 //export Java_com_tailscale_ipn_App_onConnectivityChanged
 func Java_com_tailscale_ipn_App_onConnectivityChanged(env *C.JNIEnv, cls C.jclass, connected C.jboolean) {
 	select {