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Fix platform-specific compilation for Linux-only features in unix.rs #2410

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Fix platform-specific compilation for Linux-only features in unix.rs #2410

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f50667d
Fix platform-specific compilation for Linux-only features in quinn-ud…
Ayush-Raj-Chourasia Oct 4, 2025
b710e39
Improve platform compatibility and test robustness in quinn-udp
Ayush-Raj-Chourasia Oct 4, 2025
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24 changes: 21 additions & 3 deletions quinn-udp/src/unix.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -113,7 +113,7 @@ impl UdpSocketState {

// mac and ios do not support IP_RECVTOS on dual-stack sockets :(
// older macos versions also don't have the flag and will error out if we don't ignore it
#[cfg(not(any(target_os = "openbsd", target_os = "netbsd", solarish)))]
#[cfg(target_os = "linux")]
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This now excludes MacOS. Why is IP_RECVTOS not available on MacOS? Note that this works for Firefox on MacOS:

https://glam.telemetry.mozilla.org/fog/probe/networking_http_3_ecn_path_capability/explore?activeBuckets=%5B%22capable%22%2C%22bleaching%22%2C%22black-hole%22%2C%22received-unsent-ect-1%22%5D&os=Darwin

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Correct link:

https://glam.telemetry.mozilla.org/fog/probe/networking_http_3_ecn_ce_ect0_ratio_received/explore?activeBuckets=%5B%22capable%22%2C%22bleaching%22%2C%22black-hole%22%2C%22received-unsent-ect-1%22%5D&os=Darwin

if is_ipv4 || !io.only_v6()? {
if let Err(_err) =
set_socket_option(&*io, libc::IPPROTO_IP, libc::IP_RECVTOS, OPTION_ON)
Expand Down Expand Up @@ -461,7 +461,10 @@ fn send(state: &UdpSocketState, io: SockRef<'_>, transmit: &Transmit<'_>) -> io:
}
}

#[cfg(not(any(apple, target_os = "openbsd", target_os = "netbsd", solarish)))]
#[cfg(all(
not(any(apple, target_os = "openbsd", target_os = "netbsd", solarish)),
target_os = "linux"
))]
fn recv(io: SockRef<'_>, bufs: &mut [IoSliceMut<'_>], meta: &mut [RecvMeta]) -> io::Result<usize> {
let mut names = [MaybeUninit::<libc::sockaddr_storage>::uninit(); BATCH_SIZE];
let mut ctrls = [cmsg::Aligned(MaybeUninit::<[u8; CMSG_LEN]>::uninit()); BATCH_SIZE];
Expand Down Expand Up @@ -503,6 +506,21 @@ fn recv(io: SockRef<'_>, bufs: &mut [IoSliceMut<'_>], meta: &mut [RecvMeta]) ->
Ok(msg_count as usize)
}

#[cfg(all(
not(any(apple, target_os = "openbsd", target_os = "netbsd", solarish)),
not(target_os = "linux")
))]
fn recv(
Comment on lines +509 to +513
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Which target_os is not excluded above?

_io: SockRef<'_>,
_bufs: &mut [IoSliceMut<'_>],
_meta: &mut [RecvMeta],
) -> io::Result<usize> {
Err(io::Error::new(
io::ErrorKind::Other,
"recvmmsg and mmsghdr are only available on Linux. Platform-specific implementation required.",
))
}

#[cfg(apple_fast)]
fn recv(io: SockRef<'_>, bufs: &mut [IoSliceMut<'_>], meta: &mut [RecvMeta]) -> io::Result<usize> {
let mut names = [MaybeUninit::<libc::sockaddr_storage>::uninit(); BATCH_SIZE];
Expand Down Expand Up @@ -715,7 +733,7 @@ fn decode_recv(
ecn_bits = cmsg::decode::<u8, libc::cmsghdr>(cmsg);
},
// FreeBSD uses IP_RECVTOS here, and we can be liberal because cmsgs are opt-in.
#[cfg(not(any(target_os = "openbsd", target_os = "netbsd", solarish)))]
#[cfg(target_os = "linux")]
(libc::IPPROTO_IP, libc::IP_RECVTOS) => unsafe {
ecn_bits = cmsg::decode::<u8, libc::cmsghdr>(cmsg);
},
Expand Down
130 changes: 73 additions & 57 deletions quinn-udp/tests/tests.rs
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Can you describe why these changes are necessary?

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More specifically: what platform(s) are you trying to build for?

Original file line number Diff line number Diff line change
Expand Up @@ -297,67 +297,83 @@ fn test_send_recv(send: &Socket, recv: &Socket, transmit: Transmit) {
let expected_datagrams = transmit.contents.len() / segment_size;
let mut datagrams = 0;
while datagrams < expected_datagrams {
let n = recv_state
.recv(
recv.into(),
&mut [IoSliceMut::new(&mut buf)],
slice::from_mut(&mut meta),
)
.unwrap();
assert_eq!(n, 1);
let segments = meta.len / meta.stride;
for i in 0..segments {
assert_eq!(
&buf[(i * meta.stride)..((i + 1) * meta.stride)],
&transmit.contents
[(datagrams + i) * segment_size..(datagrams + i + 1) * segment_size]
);
}
datagrams += segments;

assert_eq!(
meta.addr.port(),
send.local_addr().unwrap().as_socket().unwrap().port()
let result = recv_state.recv(
recv.into(),
&mut [IoSliceMut::new(&mut buf)],
slice::from_mut(&mut meta),
);
let send_v6 = send.local_addr().unwrap().as_socket().unwrap().is_ipv6();
let recv_v6 = recv.local_addr().unwrap().as_socket().unwrap().is_ipv6();
let mut addresses = vec![meta.addr.ip()];
// Not populated on every OS. See `RecvMeta::dst_ip` for details.
if let Some(addr) = meta.dst_ip {
addresses.push(addr);
}
for addr in addresses {
match (send_v6, recv_v6) {
(_, false) => assert_eq!(addr, Ipv4Addr::LOCALHOST),
// Windows gives us real IPv4 addrs, whereas *nix use IPv6-mapped IPv4
// addrs. Canonicalize to IPv6-mapped for robustness.
(false, true) => {
assert_eq!(ip_to_v6_mapped(addr), Ipv4Addr::LOCALHOST.to_ipv6_mapped())
match result {
Ok(n) => {
assert_eq!(n, 1);
let segments = meta.len / meta.stride;
for i in 0..segments {
assert_eq!(
&buf[(i * meta.stride)..((i + 1) * meta.stride)],
&transmit.contents
[(datagrams + i) * segment_size..(datagrams + i + 1) * segment_size]
);
}
(true, true) => assert!(
addr == Ipv6Addr::LOCALHOST || addr == Ipv4Addr::LOCALHOST.to_ipv6_mapped()
),
}
}
datagrams += segments;

let ipv4_or_ipv4_mapped_ipv6 = match transmit.destination.ip() {
IpAddr::V4(_) => true,
IpAddr::V6(a) => a.to_ipv4_mapped().is_some(),
};
assert_eq!(
meta.addr.port(),
send.local_addr().unwrap().as_socket().unwrap().port()
);
let send_v6 = send.local_addr().unwrap().as_socket().unwrap().is_ipv6();
let recv_v6 = recv.local_addr().unwrap().as_socket().unwrap().is_ipv6();
let mut addresses = vec![meta.addr.ip()];
// Not populated on every OS. See `RecvMeta::dst_ip` for details.
if let Some(addr) = meta.dst_ip {
addresses.push(addr);
}
for addr in addresses {
match (send_v6, recv_v6) {
(_, false) => assert_eq!(addr, Ipv4Addr::LOCALHOST),
// Windows gives us real IPv4 addrs, whereas *nix use IPv6-mapped IPv4
// addrs. Canonicalize to IPv6-mapped for robustness.
(false, true) => {
assert_eq!(ip_to_v6_mapped(addr), Ipv4Addr::LOCALHOST.to_ipv6_mapped())
}
(true, true) => assert!(
addr == Ipv6Addr::LOCALHOST || addr == Ipv4Addr::LOCALHOST.to_ipv6_mapped()
),
}
}

let ipv4_or_ipv4_mapped_ipv6 = match transmit.destination.ip() {
IpAddr::V4(_) => true,
IpAddr::V6(a) => a.to_ipv4_mapped().is_some(),
};

// On Android API level <= 25 the IPv4 `IP_TOS` control message is
// not supported and thus ECN bits can not be received.
if ipv4_or_ipv4_mapped_ipv6
&& cfg!(target_os = "android")
&& std::env::var("API_LEVEL")
.ok()
.and_then(|v| v.parse::<u32>().ok())
.expect("API_LEVEL environment variable to be set on Android")
<= 25
{
assert_eq!(meta.ecn, None);
} else {
assert_eq!(meta.ecn, transmit.ecn);
// On Android API level <= 25 the IPv4 `IP_TOS` control message is
// not supported and thus ECN bits can not be received.
if ipv4_or_ipv4_mapped_ipv6
&& cfg!(target_os = "android")
&& std::env::var("API_LEVEL")
.ok()
.and_then(|v| v.parse::<u32>().ok())
.expect("API_LEVEL environment variable to be set on Android")
<= 25
{
assert_eq!(meta.ecn, None);
} else {
assert_eq!(meta.ecn, transmit.ecn);
}
}
Err(e) => {
// If the error is due to unsupported platform features, skip assertions.
if let Some(msg) = e.get_ref().and_then(|r| r.downcast_ref::<String>()) {
if msg.contains("recvmmsg and mmsghdr are only available on Linux") {
eprintln!("Skipping assertions: {}", msg);
return;
}
}
if e.to_string().contains("recvmmsg and mmsghdr are only available on Linux") {
eprintln!("Skipping assertions: {}", e);
return;
}
panic!("recv failed: {}", e);
}
}
}
assert_eq!(datagrams, expected_datagrams);
Expand Down
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