moq_native/
bind.rs

1//! Dual-stack socket binding.
2//!
3//! Quinn uses a single socket and relies on the OS to route both address
4//! families. On Linux an `[::]` socket accepts IPv4 too, but Windows defaults
5//! `IPV6_V6ONLY` to on, so an IPv6 socket silently drops every IPv4 packet. The
6//! helpers here clear that before binding, so a relay on `[::]` is reachable
7//! over IPv4 and a dual-stack client can dial IPv4 servers (via IPv4-mapped
8//! addresses; the client's address-family matching lives in `util::pick_addr`).
9//! See <https://github.com/moq-dev/moq/issues/1375>.
10
11use socket2::{Domain, Protocol, Socket, Type};
12use std::net::{SocketAddr, TcpListener, UdpSocket};
13
14/// Bind a UDP socket, making an IPv6 socket dual-stack so it also serves IPv4.
15pub fn udp(addr: SocketAddr) -> std::io::Result<UdpSocket> {
16	let domain = if addr.is_ipv4() { Domain::IPV4 } else { Domain::IPV6 };
17	let socket = Socket::new(domain, Type::DGRAM, Some(Protocol::UDP))?;
18	make_dual_stack(&socket, addr);
19	socket.bind(&addr.into())?;
20	Ok(socket.into())
21}
22
23/// Bind a TCP listener, making an IPv6 socket dual-stack so it also serves IPv4.
24///
25/// The returned listener is non-blocking, ready for
26/// [`axum_server::from_tcp`](https://docs.rs/axum-server).
27pub fn tcp(addr: SocketAddr) -> std::io::Result<TcpListener> {
28	let domain = if addr.is_ipv4() { Domain::IPV4 } else { Domain::IPV6 };
29	let socket = Socket::new(domain, Type::STREAM, Some(Protocol::TCP))?;
30	make_dual_stack(&socket, addr);
31	// Match std's TcpListener, which sets SO_REUSEADDR on Unix (not Windows) so a
32	// restarted relay can rebind a port still in TIME_WAIT.
33	#[cfg(not(windows))]
34	socket.set_reuse_address(true)?;
35	socket.bind(&addr.into())?;
36	socket.listen(1024)?;
37	let listener: TcpListener = socket.into();
38	listener.set_nonblocking(true)?;
39	Ok(listener)
40}
41
42/// Clear `IPV6_V6ONLY` so an IPv6 socket also accepts IPv4. Best-effort: a
43/// platform that rejects the option keeps its default rather than failing the
44/// bind. No-op for IPv4 sockets.
45fn make_dual_stack(socket: &Socket, addr: SocketAddr) {
46	if addr.is_ipv6()
47		&& let Err(err) = socket.set_only_v6(false)
48	{
49		tracing::warn!(%err, "failed to enable dual-stack IPv6 socket; IPv4 clients may be unreachable");
50	}
51}
52
53#[cfg(test)]
54mod tests {
55	use super::*;
56
57	#[test]
58	fn udp_ipv6_is_dual_stack() {
59		// An IPv6 wildcard bind should come back dual-stack so IPv4 traffic
60		// reaches it. socket2 lets us read the option back to confirm.
61		let socket = udp("[::]:0".parse().unwrap()).unwrap();
62		let socket = Socket::from(socket);
63		assert!(!socket.only_v6().unwrap(), "IPv6 socket should be dual-stack");
64	}
65
66	#[test]
67	fn udp_ipv4_still_binds() {
68		let socket = udp("127.0.0.1:0".parse().unwrap()).unwrap();
69		assert!(socket.local_addr().unwrap().is_ipv4());
70	}
71
72	#[test]
73	fn tcp_ipv6_is_dual_stack() {
74		let listener = tcp("[::]:0".parse().unwrap()).unwrap();
75		let socket = Socket::from(listener);
76		assert!(!socket.only_v6().unwrap(), "IPv6 listener should be dual-stack");
77	}
78}
moq_native/bind.rs

moq_native/
bind.rs
