Feat: add option to disable UDP functionality

[SuzukiHonoka]

Some proxy server may not support udp, the udp processing logic may slow down performance, we can explicitly disable it before letting program to detect if the proxy server supports it.

[xjasonlyu]

Would it be possible to disable UDP at the stack level instead of at the tunnel/transportation level?

e.g.,

tun2socks/core/stack.go

Lines 48 to 52 in 61d8269

	TransportProtocols: []stack.TransportProtocolFactory{
	tcp.NewProtocol,
	udp.NewProtocol,
	icmp.NewProtocol4,
	icmp.NewProtocol6,

or,

tun2socks/core/udp.go

Lines 14 to 38 in 61d8269

	func withUDPHandler(handle func(adapter.UDPConn)) option.Option {
	return func(s *stack.Stack) error {
	udpForwarder := udp.NewForwarder(s, func(r *udp.ForwarderRequest) bool {
	var (
	wq waiter.Queue
	id = r.ID()
	)
	ep, err := r.CreateEndpoint(&wq)
	if err != nil {
	glog.Debugf("forward udp request: %s:%d->%s:%d: %s",
	id.RemoteAddress, id.RemotePort, id.LocalAddress, id.LocalPort, err)
	return false
	}
	conn := &udpConn{
	UDPConn: gonet.NewUDPConn(&wq, ep),
	id: id,
	}
	handle(conn)
	return true
	})
	s.SetTransportProtocolHandler(udp.ProtocolNumber, udpForwarder.HandlePacket)
	return nil
	}
	}

IMO if we only disable UDP at the tunnel level, the gvisor stack would still have to handle the UDP "connection", which would lead to unnecessary overhead.

[SuzukiHonoka]

Would it be possible to disable UDP at the stack level instead of at the tunnel/transportation level?

e.g.,

tun2socks/core/stack.go

Lines 48 to 52 in 61d8269

	TransportProtocols: []stack.TransportProtocolFactory{
	tcp.NewProtocol,
	udp.NewProtocol,
	icmp.NewProtocol4,
	icmp.NewProtocol6,

or,

tun2socks/core/udp.go

Lines 14 to 38 in 61d8269

	func withUDPHandler(handle func(adapter.UDPConn)) option.Option {
	return func(s *stack.Stack) error {
	udpForwarder := udp.NewForwarder(s, func(r *udp.ForwarderRequest) bool {
	var (
	wq waiter.Queue
	id = r.ID()
	)
	ep, err := r.CreateEndpoint(&wq)
	if err != nil {
	glog.Debugf("forward udp request: %s:%d->%s:%d: %s",
	id.RemoteAddress, id.RemotePort, id.LocalAddress, id.LocalPort, err)
	return false
	}
	conn := &udpConn{
	UDPConn: gonet.NewUDPConn(&wq, ep),
	id: id,
	}
	handle(conn)
	return true
	})
	s.SetTransportProtocolHandler(udp.ProtocolNumber, udpForwarder.HandlePacket)
	return nil
	}
	}

IMO if we only disable UDP at the tunnel level, the gvisor stack would still have to handle the UDP "connection", which would lead to unnecessary overhead.

This looks reasonable, the main point is I want also log the udp request while blocking it, but if that causes overhead, we may simply remove the udp in TransportProtocols. I will re-check this in detail when I'm free.

[mimedo]

Is there a way to disable UDP? Somehow I can't connect to a proxy and support from the provider says I should try without UDP.

[xjasonlyu]

UDP should have nothing to do with connecting to a proxy (at least the TCP should work)

[mimedo]

Thanks for the quick response @xjasonlyu!
When I connect to the SOCKS5 proxy I don't have any internet traffic and I see in the logs:

tun2socks -device tun0 -proxy socks5://[proxy-host]:[proxy-port] -interface eth0
[TCP] dial 1.0.0.1:853: CONNECT: connection not allowed by ruleset"
[UDP] dial 1.1.1.1:53: client handshake: EOF

I tried http-protocoll as well. The proxy provider doesn't need any authentication because my public IP is whitelisted, but I get this message from the logs:

tun2socks -device tun0 -proxy http://[proxy-host]:[proxy-port] -interface eth0
[TCP] dial 1.0.0.1:853: HTTP auth required by proxy"
[UDP] dial 1.0.0.1:53: unsupported operation

So I tried to add credentials but it still didn't work:

tun2socks -device tun0 -proxy http://[username]:[password]@[proxy-host]:[proxy-port] -interface eth0
[TCP] dial 1.0.0.1:853: HTTP connect status: 403 Forbidden
[UDP] dial 1.0.0.1:53: unsupported operation

I want to add that I tried another proxy provider which supported UDP and it worked without any problem. Additionally, I installed Super Proxy on my S21 and connected successfully with SOCKS5 to the proxy. I don't know why it doesn't work with tun2socks.

[mimedo]

@xjasonlyu I can demonstrate it for you with the Proxy provider I use. Unfortunatelly, I couldn't manage to get it working.

[mimedo]

@SuzukiHonoka I see this feature was merged. How is the command to start a connection without UDP?

[SuzukiHonoka]

@SuzukiHonoka I see this feature was merged. How is the command to start a connection without UDP?

It was not merged yet, if you want to try this, check my fork version of tun2socks, you'll need to compile the binary yourself.