Windows: WARN:smartdns::server::udp:36: error receiving message on udp_socket (and fix)

[chmichael]

Only in windows it throws and UDP warning:
WARN:smartdns::server::udp:36: error receiving message on udp_socket: An existing connection was forcibly closed by the remote host. (os error 10054)

Here's the solution for windows only in rust:
shadowsocks/shadowsocks-rust#262 (comment)
You'll need to import the winapi package too: https://crates.io/crates/winapi

from notes:
Ignoring UdpSocket's WSAECONNRESET error
This is because UdpSocket::recv_from may return WSAECONNRESET
if you called UdpSocket::send_to a destination that is not existed (may be closed).
It is not an error. Could be ignored completely.
We have to ignore it here because it will crash the server.

I hope you add it soon
discussion: #368

[mokeyish]

Thanks, Looks good, I'll check it out this weekend.

There is already a ready-made code, you can just adjust it and give it a try.

The corresponding code is here:

smartdns-rs/src/server/mod.rs

Lines 330 to 350 in 669e379

	pub fn udp(
	sock_addr: SocketAddr,
	bind_device: Option<&str>,
	bind_type: &str,
	) -> io::Result<UdpSocket> {
	let device_note = bind_device
	.map(|device| format!("@{device}"))
	.unwrap_or_default();
	log::debug!("binding {} to {:?}{}", bind_type, sock_addr, device_note);
	let udp_socket = std::net::UdpSocket::bind(sock_addr)?;
	{
	let sock_ref = socket2::SockRef::from(&udp_socket);
	sock_ref.set_nonblocking(true)?;
	sock_ref.set_reuse_address(true)?;
	#[cfg(target_os = "macos")]
	sock_ref.set_reuse_port(true)?;
	#[cfg(any(target_os = "android", target_os = "fuchsia", target_os = "linux"))]

[mokeyish]

I solved this problem a long time ago. At that time, the program crashed. I just changed the error to a warning so that it would not affect the use.

hickory-dns/hickory-dns#1913 (comment)

[chmichael]

Done and compiled! No more UDP errors in Windows!

btw it needs the "unsafe declaration" cause of "WSAIoctl".
Maybe you can find somewhere else safe ?

CARGO.TOML add:
[target.'cfg(windows)'.dependencies]
...
// add code below
winapi = { version = "0.3.9", features = ["mswsock", "winsock2"] }
...

MOD.RS:

    pub fn udp(
        sock_addr: SocketAddr,
        bind_device: Option<&str>,
        bind_type: &str,
    ) -> io::Result<UdpSocket> {

        // add code below
        use std::{mem, os::windows::io::AsRawSocket, ptr};
        use winapi::{
            shared::minwindef::{BOOL, DWORD, FALSE, LPDWORD, LPVOID},
            um::{
                mswsock::SIO_UDP_CONNRESET,
                winsock2::{WSAGetLastError, WSAIoctl, SOCKET, SOCKET_ERROR},
                },
        };
       
        ...        
        let udp_socket = std::net::UdpSocket::bind(sock_addr)?;`

        // add code below
        let handle = udp_socket.as_raw_socket() as SOCKET;
        let mut bytes_returned: DWORD = 0;
        let mut enable: BOOL = FALSE;
	    unsafe { 
		    let ret = WSAIoctl(
              handle,
              SIO_UDP_CONNRESET,
              &mut enable as *mut _ as LPVOID,
              mem::size_of_val(&enable) as DWORD,
              ptr::null_mut(),
              0,
              &mut bytes_returned as *mut _ as LPDWORD,
              ptr::null_mut(),
              None,
            );

  	        if ret == SOCKET_ERROR {
               use std::io::Error;

              // Error occurs
              let err_code = WSAGetLastError();
              return Err(Error::from_raw_os_error(err_code));
            }
		};

ps: i did update all the cargo packages to the latest versions and only rustls has a breaking change.

[mokeyish]

Calling Windows API, unsafe seems to be inevitable.

But I prefer to use
https://crates.io/crates/windows
instead of winapi, which has not been updated for a long time.

[chmichael]

Windows GNU build produces UDP 38 error

[mokeyish]

Indeed, GNU has not solved this problem. I don't have time to find a solution, and if it is solved, it will only reduce the log warning, which does not affect the use.