How to create a simple VPN connection?

[xinlake]

Hi, Developer

I am trying to create a simple VPN connection on Android and use your native program to forward the traffic, The following code inherits the Android VpnService. I call the native programs in onStartCommand finally start a thread to receive sslocal's file descriptor and protect it, The value of protected is true but the browser cannot open any website.

Am I missing something? Need your help, Thank you!

private static final int VPN_MTU = 1500;
private static final String PRIVATE_VLAN4_CLIENT = "172.19.0.1";
private static final String PRIVATE_VLAN4_ROUTER = "172.19.0.2";
private static final String PRIVATE_VLAN6_CLIENT = "fdfe:dcba:9876::1";
private static final String PRIVATE_VLAN6_ROUTER = "fdfe:dcba:9876::2";

int portLocalDns = 5450;
int portProxy = 1080;

// start shadowsocks
Process startShadowsocks() {
    try {
        String cmd = new File(getApplicationInfo().nativeLibraryDir, "libsslocal.so").getAbsolutePath()
            + " --local-addr 127.0.0.1:1080"
            + " --udp-bind-addr 127.0.0.1:1080"
            + " --server-addr 123.123.123.123:1234"     // server address and port
            + " -k password"                            // server password
            + " -m rc4-md5"
            + " --dns-addr 127.0.0.1:" + portLocalDns
            + " --local-dns-addr local_dns_path"
            + " --remote-dns-addr 8.8.8.8:53"
            + " --vpn"
            + " -U";
        return Runtime.getRuntime().exec(cmd, null, getApplicationContext().getNoBackupFilesDir());
    } catch (Exception exception) {
    }

    return null;
}

ParcelFileDescriptor startVpn() {
    try {
        Builder builder = new Builder()
            .setSession("session")
            .setMtu(VPN_MTU)
            .addAddress(PRIVATE_VLAN4_CLIENT, 30)
            .addDnsServer(PRIVATE_VLAN4_ROUTER)
            .addRoute(PRIVATE_VLAN4_ROUTER, 32);

        ParcelFileDescriptor pfd = builder.establish();
        setUnderlyingNetworks(null);

        // start tun2socks
        String cmd = new File(getApplicationInfo().nativeLibraryDir, "libtun2socks.so").getAbsolutePath()
            + " --netif-ipaddr " + PRIVATE_VLAN4_ROUTER
            + " --socks-server-addr 127.0.0.1:" + portProxy
            + " --tunmtu " + VPN_MTU
            + " --sock-path sock_path"
            + " --dnsgw 127.0.0.1:" + portLocalDns
            + " --loglevel warning"
            + " --enable-udprelay";

        Runtime.getRuntime().exec(cmd, null, getApplicationContext().getNoBackupFilesDir());
        return pfd;
    } catch (Exception exception) {
    }

    return null;
}

private boolean sendFd(FileDescriptor fd) {
    int tries = 0;
    String path = new File(getApplicationContext().getNoBackupFilesDir(), "sock_path").getAbsolutePath();
    while (true) {
        try {
            Thread.sleep(100);
            LocalSocket localSocket = new LocalSocket();
            localSocket.connect(new LocalSocketAddress(path, LocalSocketAddress.Namespace.FILESYSTEM));
            localSocket.setFileDescriptorsForSend(new FileDescriptor[]{fd});
            localSocket.getOutputStream().write(42);

            return true;
        } catch (Exception exception) {
            if (tries > 5) {
                return false;
            }
            tries += 1;
        }
    }
}

@Override
public int onStartCommand(Intent intent, int flags, int startId) {
    if (startShadowsocks() == null) {
        stopSelf();
        return START_NOT_STICKY;
    }

    ParcelFileDescriptor vpnInterface = startVpn();
    if (vpnInterface == null) {
        stopSelf();
        return START_NOT_STICKY;
    }

    if (!sendFd(vpnInterface.getFileDescriptor())) {
        stopSelf();
        return START_NOT_STICKY;
    }

    // protect ss traffic
    new Thread(() -> {
        try {
            File socketFile = new File(getApplicationContext().getNoBackupFilesDir(), "protect_path");
            LocalSocket localSocket = new LocalSocket();
            localSocket.bind(new LocalSocketAddress(socketFile.getAbsolutePath(), LocalSocketAddress.Namespace.FILESYSTEM));

            LocalServerSocket serverSocket = new LocalServerSocket(localSocket.getFileDescriptor());
            LocalSocket socket = serverSocket.accept();
            if (socket.getInputStream().read() == -1) {
                return;
            }

            FileDescriptor[] fileDescriptors = socket.getAncillaryFileDescriptors();
            FileDescriptor fd = fileDescriptors[0];

            @SuppressLint("DiscouragedPrivateApi")
            Method getInt = FileDescriptor.class.getDeclaredMethod("getInt$");
            int fdsslocal = (Integer) getInt.invoke(fd);

            boolean protected = protect(fdsslocal);      // returns true
        } catch (Exception exception) {
        }
    }).start();

    return START_STICKY;
}

[xinlake]

This problem has been resolved and it is related to DNS. Thank you.

[IkramulMurad]

```String cmd = new File(getApplicationInfo().nativeLibraryDir, "libsslocal.so").getAbsolutePath()
        + " --local-addr 127.0.0.1:1080"
        + " --udp-bind-addr 127.0.0.1:1080"
        + " --server-addr 123.123.123.123:1234"     // server address and port
        + " -k password"                            // server password
        + " -m rc4-md5"
        + " --dns-addr 127.0.0.1:" + portLocalDns
        + " --local-dns-addr local_dns_path"
        + " --remote-dns-addr 8.8.8.8:53"
        + " --vpn"
        + " -U";
    return Runtime.getRuntime().exec(cmd, null, getApplicationContext().getNoBackupFilesDir());```

The above code is about how to turn on shadowsocks. Could you please tell how to turn off shadowsocks?