only_v6 panic on windows

[BiagioFesta]

This sample code

use socket2::SockRef;
use std::net::{Ipv4Addr, SocketAddr, UdpSocket};

fn is_only_v6(socket: SockRef) -> Option<bool> {
    socket.only_v6().ok()
}

fn main() {
    let socket = UdpSocket::bind(SocketAddr::new(Ipv4Addr::LOCALHOST.into(), 0)).unwrap();
    println!("{:?}", is_only_v6(SockRef::from(&socket)));
}

panics (debug assertion) on Windows

thread 'main' panicked at ..\socket2-0.5.8\src\sys\windows.rs:772:9:
assertion `left == right` failed
  left: 1
 right: 4

Is this expected and I am missing something?

[Thomasdezeeuw]

I think Windows doesn't use a c_int for this option, but a boolean (the 1 byte one, not the 4 byte on they sometimes use). So we need to update the type:

socket2/src/socket.rs

Line 1880 in 5c1f3b0

getsockopt::<c_int>(self.as_raw(), sys::IPPROTO_IPV6, sys::IPV6_V6ONLY)

See

socket2/src/sys/windows.rs

Lines 87 to 94 in 5c1f3b0

	/// Type used in set/getsockopt to retrieve the `TCP_NODELAY` option.
	///
	/// NOTE: <https://docs.microsoft.com/en-us/windows/win32/api/winsock2/nf-winsock2-getsockopt>
	/// documents that options such as `TCP_NODELAY` and `SO_KEEPALIVE` expect a
	/// `BOOL` (alias for `c_int`, 4 bytes), however in practice this turns out to
	/// be false (or misleading) as a `BOOLEAN` (`c_uchar`, 1 byte) is returned by
	/// `getsockopt`.
	pub(crate) type Bool = windows_sys::Win32::Foundation::BOOLEAN;

Weird that our testing never caught this before.