android: implement VpnService

android/yass/src/main/AndroidManifest.xml

@@ -27,6 +27,19 @@
                 <category android:name="android.intent.category.LAUNCHER" />
             </intent-filter>
         </activity>
+
+        <service
+            android:name=".YassVpnService"
+            android:directBootAware="true"
+            android:exported="false"
+            android:label="@string/app_name"
+            android:permission="android.permission.BIND_VPN_SERVICE"
+            android:process=":bg">
+
+            <intent-filter>
+                <action android:name="android.net.VpnService" />
+            </intent-filter>
+        </service>
     </application>
 
 </manifest>

android/yass/src/main/java/it/gui/yass/MainActivity.java

@@ -4,18 +4,21 @@
 
 import android.app.Activity;
 import android.content.Context;
+import android.content.Intent;
 import android.content.pm.ApplicationInfo;
 import android.content.res.Resources;
 import android.net.ConnectivityManager;
 import android.net.wifi.WifiManager;
 import android.os.Bundle;
+import android.os.ParcelFileDescriptor;
 import android.view.View;
 import android.widget.ArrayAdapter;
 import android.widget.Button;
 import android.widget.EditText;
 import android.widget.Spinner;
 import android.widget.TextView;
 
+import java.io.IOException;
 import java.net.InetAddress;
 import java.net.UnknownHostException;
 import java.nio.ByteBuffer;
@@ -50,6 +53,7 @@ protected void onCreate(Bundle savedInstanceState) {
     @Override
     protected void onDestroy() {
         stopRefreshPoll();
+        tun2ProxyStop();
         onNativeDestroy();
         super.onDestroy();
     }
@@ -142,37 +146,82 @@ private void saveSettingsIntoNative() {
         setTimeout(Integer.parseInt(timeoutEditText.getText().toString()));
     }
 
+    private final YassVpnService vpnService = new YassVpnService();
+
+    private ParcelFileDescriptor tunFd = null;
+
+    @Override
+    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
+        if (requestCode == VPN_SERVICE_CODE && resultCode == RESULT_OK) {
+            onStartVpn();
+            return;
+        }
+        super.onActivityResult(requestCode, resultCode, data);
+    }
+
+    private final int VPN_SERVICE_CODE = 10000;
+    private Thread tun2proxyThread;
+    private void onStartVpn() {
+        tunFd = vpnService.connect(getApplicationContext());
+        if (tunFd == null) {
+            return;
+        }
+        tun2proxyThread = new Thread(){
+            public void run() {
+                tun2ProxyStart("socks5://127.0.0.1:3000", tunFd.getFd(), vpnService.DEFAULT_MTU, true, true);
+            }
+        };
+        tun2proxyThread.start();
+
+        Button startButton = findViewById(R.id.startButton);
+        startButton.setEnabled(false);
+
+        TextView statusTextView = findViewById(R.id.statusTextView);
+        statusTextView.setText(R.string.status_starting);
+        state = NativeMachineState.STARTING;
+        nativeStart();
+    }
+
     public void onStartClicked(View view) {
         if (state == NativeMachineState.STOPPED) {
             saveSettingsIntoNative();
 
-            if (tun2ProxyStart("socks5://127.0.0.1:3000", -1, 1500, true, true) != 0) {
-                return;
+            Intent intent = YassVpnService.prepare(getApplicationContext());
+            if (intent == null) {
+                onActivityResult(VPN_SERVICE_CODE, RESULT_OK, null);
+            } else {
+                startActivityForResult(intent, VPN_SERVICE_CODE);
             }
+        }
+    }
 
-            Button startButton = findViewById(R.id.startButton);
-            startButton.setEnabled(false);
+    private void onStopVpn() {
+        try {
+            tunFd.close();
+        } catch (IOException e) {
+            //nop
+        }
+        tunFd = null;
 
-            TextView statusTextView = findViewById(R.id.statusTextView);
-            statusTextView.setText(R.string.status_starting);
-            state = NativeMachineState.STARTING;
-            nativeStart();
+        tun2ProxyStop();
+        try {
+            tun2proxyThread.join();
+        } catch (InterruptedException e) {
+            throw new RuntimeException(e);
         }
+        nativeStop();
 
-    }
+        Button stopButton = findViewById(R.id.stopButton);
+        stopButton.setEnabled(false);
 
+        TextView statusTextView = findViewById(R.id.statusTextView);
+        statusTextView.setText(R.string.status_stopping);
+        state = NativeMachineState.STOPPING;
+    }
     public void onStopClicked(View view) {
         if (state == NativeMachineState.STARTED) {
             stopRefreshPoll();
-            tun2ProxyStop();
-
-            Button stopButton = findViewById(R.id.stopButton);
-            stopButton.setEnabled(false);
-
-            TextView statusTextView = findViewById(R.id.statusTextView);
-            statusTextView.setText(R.string.status_stopping);
-            state = NativeMachineState.STOPPING;
-            nativeStop();
+            onStopVpn();
         }
     }
 

android/yass/src/main/java/it/gui/yass/YassVpnService.java

@@ -0,0 +1,46 @@
+package it.gui.yass;
+
+import android.app.PendingIntent;
+import android.content.Context;
+import android.content.Intent;
+import android.content.pm.PackageManager;
+import android.net.ProxyInfo;
+import android.net.VpnService;
+import android.os.Build;
+import android.os.ParcelFileDescriptor;
+
+public class YassVpnService extends VpnService {
+    public int DEFAULT_MTU = 1500;
+    private String PRIVATE_VLAN4_CLIENT = "172.19.0.1";
+    private String PRIVATE_VLAN4_GATEWAY = "172.19.0.2";
+    private String PRIVATE_VLAN6_CLIENT = "fdfe:dcba:9876::1";
+    private String PRIVATE_VLAN6_GATEWAY = "fdfe:dcba:9876::2";
+
+    public ParcelFileDescriptor connect(Context context) {
+        Builder builder = new Builder();
+
+        builder.setConfigureIntent(PendingIntent.getActivity(context, 0,
+                new Intent(context, MainActivity.class).setFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT),
+                PendingIntent.FLAG_IMMUTABLE));
+        builder.setSession("session");
+        builder.setMtu(DEFAULT_MTU);
+        builder.addAddress(PRIVATE_VLAN4_CLIENT, 30);
+        builder.addAddress(PRIVATE_VLAN6_CLIENT, 126);
+        builder.addRoute("0.0.0.0", 0);
+        builder.addRoute("::", 0);
+        // builder.setUnderlyingNetworks(underlyingNetworks);
+        // builder.setMetered(metered);
+        builder.addDnsServer(PRIVATE_VLAN4_GATEWAY);
+        builder.addDnsServer(PRIVATE_VLAN6_GATEWAY);
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
+            builder.setHttpProxy(ProxyInfo.buildDirectProxy("127.0.0.1", 3000));
+        }
+        try {
+            builder.addDisallowedApplication("it.gui.yass");
+        } catch (PackageManager.NameNotFoundException e) {
+            // nop
+        }
+
+        return builder.establish();
+    }
+}

src/android/jni.cpp

@@ -101,6 +101,8 @@ CIPHER_METHOD_VALID_MAP(XX)
   };
   DCHECK_LT((uint32_t)value, methods_idxes.size());
   absl::SetFlag(&FLAGS_method, methods_idxes[value]);
+  absl::SetFlag(&FLAGS_local_host, "0.0.0.0");
+  absl::SetFlag(&FLAGS_local_port, 3000);
 }
 
 JNIEXPORT void JNICALL Java_it_gui_yass_MainActivity_setTimeout(JNIEnv *env, jobject obj, jint value) {