Protecting Socket when using Netty4 on Android with VPNservice

Question

I am trying to use the built-in VpnService in Android to capture traffic and send it to a remote server. I am trying to use Netty, but it seems that I have come to an impasse.

In order to send data from the phone to the server I need to call Protect() on the socket otherwise all the data I transmit will just be looped back into the VpnService. However I am not sure if it's possible to get a hold of a Socket object or its filedescriptor when using Netty4.

Answer 1

you need to extends NioSocketChannel and override doConnect method:

public class ProtectedNioSocketChannel extends NioSocketChannel {
@Override
protected boolean doConnect(SocketAddress remoteAddress, SocketAddress localAddress) throws Exception {
    SocketChannel ch = javaChannel();
    if(!VpnServiceHelper.protect(ch.socket())){
        Log.i(Tag, "Can't protect Socket");
        return false;
    }
    return super.doConnect(remoteAddress, localAddress);
}

and:

Bootstrap b = new Bootstrap();
    b.group(localChannel.eventLoop())
            .channel(ProtectedNioSocketChannel.class)
            .handler(new ProxyRemoteHandler(localChannel, session))
            .option(ChannelOption.AUTO_READ, false);
    ChannelFuture f = b.connect(address);