There is a bug in udp support

[enp6]

cargo run -- --listen-addr 0.0.0.0:5000 password -u 111 -p 333

In the code, I have written config.set_udp_support(true);

However, it still cannot support UDP and prompts "invalid reply ip"

[ddscentral]

Sorry for necro. Yes, the example does not appear to work with UDP even with UDP support enabled in the library. I got it working with a small hack to src/server.rs,but it's probably not PR-worthy (still learning Rust). Can post if anyone needs it.

[dizda]

Thanks for posting this, have you found a workaround? /cc. @yuguorui @erebe @XOR-op

[erebe]

I don't know, I use this crate as a lib and don't use the implemented server/client. (I disable the exec of cmd). For UDP, I have a special case where I return the bind addr of the udp server I spawn. https://github.com/erebe/wstunnel/blob/main/src/socks5.rs#L116

Only difference from https://github.com/dizda/fast-socks5/blob/master/src/server.rs#L699 is that I return the ip of the binded socket, not the one from the reply_ip (which I always discard)

[ddscentral]

Here's a (very) rough patch which makes UDP work for me in the server example. It does some need cleanup and an extra "rand" dependency. fast-socks-udpfix.patch

I am a developer but not very familiar with intricacies of Rust. Maybe this patch will at least give you an idea on why the current implementation doesn't work.

[erebe]

Does this works if you try to contact your udp socks5 from another machine @ddscentral ?

IpAddr::V4(Ipv4Addr::new(0, 0, 0, 0))

[ddscentral]

You mean outside of localhost ? Yes, it does work fine. Server and client are separate machines. I run tun2socks on the client machine with tunnel interface as it's default route (so all traffic goes through a fast-socks5 server). This program has connection logging and I do see DNS requests over UDP going through without errors.

[yuguorui]

Thanks for posting this, have you found a workaround? /cc. @yuguorui @erebe @XOR-op

Yeah, it is hard to set a reply_ip without the knowledge of underlay socket.

There is an API set_reply_ip() at https://github.com/dizda/fast-socks5/blob/master/src/server.rs#L292. Could you @enp6 please set an IP with this API?

[yuguorui]

And here is the comments about the API.

    /// Set the bind IP address in Socks5Reply.
    ///
    /// Only the inner socket owner knows the correct reply bind addr, so leave this field to be
    /// populated. For those strict clients, users can use this function to set the correct IP
    /// address.
    ///
    /// Most popular SOCKS5 clients [1] [2] ignore BND.ADDR and BND.PORT the reply of command
    /// CONNECT, but this field could be useful in some other command, such as UDP ASSOCIATE.
    ///
    /// [1]. https://github.com/chromium/chromium/blob/bd2c7a8b65ec42d806277dd30f138a673dec233a/net/socket/socks5_client_socket.cc#L481
    /// [2]. https://github.com/curl/curl/blob/d15692ebbad5e9cfb871b0f7f51a73e43762cee2/lib/socks.c#L978

[ddscentral]

Well setting the reply IP to all zeros (instead of IPv6 localhost) and a random port instead of a zero port seems to work. But I'm not entirely sure whether this is the correct way to do it, my guess is it isn't or definitely not the best.

[yuguorui]

Agreed, but unfortunately RFC 1928 does not have a detailed description for this part.

[mokeyish]

Is udp client supported now? See README it's still on the TODO list.

[ddscentral]

By "udp client" you mean UDP support in the "client" example ?

[mokeyish]

Yeah, It only has TCP client exmaple.

[osousa]

Does UDP work? Would be nice as most rust based socks5 servers don't support UDP

[ddscentral]

With a small modification I've posted before, UDP does work for me, at least with tun2socks as client.