Support read from FileDescriptor

[kaisar945]

I don't know how to use this project in android please help me thanks

[xjasonlyu]

I'm not familiar with Android, but try to use tun instead of fd.

[nicolas-yangli]

I'm not familiar with Android, but try to use tun instead of fd.

tun cannot be open(2) directly in android without root privilege, but an fd to tun can be obtained from android framework.

[xjasonlyu]

@kaisar945 FD based device has been added experimentally but not fully tested, see f6ba31f for details.

Keep me updated if you encounter any problems.

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[marco20240618]

@kaisar945 FD based device has been added experimentally but not fully tested, see f6ba31f for details.

Keep me updated if you encounter any problems.

But how to use it?

In badvpn(https://github.com/ambrop72/badvpn), I see this command
tun2socks --netif-ipaddr 26.26.26.2 --netif-netmask 255.255.255.0 --socks-server-addr 127.0.0.1:1080 --tunmtu 1500 --loglevel notice --enable-udprelay --sock-path /tmp/sock_path

and then send the file desriptor of the tun0 device to --sock-path

To be more specific, this is how badvpn-tun2socks works in Android.

1. create a tun device

android.net.VpnService.Builder builder = new android.net.VpnService.Builder()
                    .setMtu(1500)
                    .addAddress("26.26.26.1", 24)
                    .addDnsServer("8.8.8.8")
                    .addRoute("0.0.0.0", 0);
mInterface = builder.establish();

2. run tun2socks

String tun2socks_command = String.format(java.util.Locale.US, "%s/libtun2socks.so --netif-ipaddr 26.26.26.2 --netif-netmask 255.255.255.0 --socks-server-addr 127.0.0.1:1080 --tunmtu 1500 --loglevel notice --enable-udprelay --sock-path %s/sock_path", this.getApplicationInfo().nativeLibraryDir, this.getApplicationInfo().dataDir);
Runtime.getRuntime().exec(tun2socks_command);

3. send file descriptor of tun0 to sock-path

            int tries = 0;
            while (true) {
                try {
                    Thread.sleep(1000L * tries);
                    android.net.LocalSocket ls = new android.net.LocalSocket();
                    ls.connect(new android.net.LocalSocketAddress(getApplicationInfo().dataDir + "/sock_path", android.net.LocalSocketAddress.Namespace.FILESYSTEM));
                    ls.setFileDescriptorsForSend(new java.io.FileDescriptor[]{mInterface.getFileDescriptor()});
                    ls.getOutputStream().write(42);
                    android.widget.Toast.makeText(getApplicationContext(), "Start Service", android.widget.Toast.LENGTH_SHORT).show();
                    break;
                } catch (Exception e) {
                    if (tries > 5) {
                        break;
                    }
                    ++tries;
                    Util.myLog(this, "fd send error, tries: " + tries);
                }
            }

[kaisar945]

Thanks friend😄

[huqiyu]

Engine.stop() will report an error when restarted after disconnection
GoLog: fdsan: attempted to close file descriptor 160, expected to be unowned, actually owned by ParcelFileDescriptor 0xe4afcec