Expand ECN support

libc's CMSG macros got built out to many more platforms. There may
remain some obscure platforms where this will still fail to build, but
we can account for them as they show up in practice.

Author: Ralith

quinn/Cargo.toml

@@ -35,7 +35,7 @@ untrusted = "0.6.2"
 webpki = "0.19"
 webpki-roots = "0.16"
 ct-logs = "0.5"
-libc = "0.2.46"
+libc = "0.2.49"
 mio = "0.6"
 
 [dev-dependencies]

quinn/src/platform/cmsg.rs

@@ -36,7 +36,7 @@ impl<'a> Encoder<'a> {
         assert!(mem::align_of::<T>() <= mem::align_of::<libc::cmsghdr>());
         let space = unsafe { libc::CMSG_SPACE(mem::size_of_val(&value) as _) as usize };
         assert!(
-            self.hdr.msg_controllen >= self.len + space,
+            self.hdr.msg_controllen as usize >= self.len + space,
             "control message buffer too small"
         );
         let cmsg = self.cmsg.take().expect("no control buffer space remaining");
@@ -60,7 +60,7 @@ impl<'a> Encoder<'a> {
 // by `sendmsg`.
 impl<'a> Drop for Encoder<'a> {
     fn drop(&mut self) {
-        self.hdr.msg_controllen = self.len;
+        self.hdr.msg_controllen = self.len as _;
     }
 }
 

quinn/src/platform/mod.rs

@@ -2,15 +2,13 @@
 use quinn_proto::EcnCodepoint;
 use std::{io, net::SocketAddr};
 
-// The Linux code should work for most unixes, but as of this writing nobody's ported the
-// CMSG_... macros to the libc crate for any of the BSDs.
-#[cfg(target_os = "linux")]
+#[cfg(unix)]
 mod cmsg;
-#[cfg(target_os = "linux")]
-mod linux;
+#[cfg(unix)]
+mod unix;
 
 // No ECN support
-#[cfg(not(target_os = "linux"))]
+#[cfg(not(unix))]
 mod fallback;
 
 pub trait UdpExt {

quinn/src/platform/linux.rs renamed to quinn/src/platform/unix.rs

@@ -22,24 +22,25 @@ impl super::UdpExt for UdpSocket {
             mem::size_of::<SocketAddrV6>(),
             mem::size_of::<libc::sockaddr_in6>()
         );
-        assert_eq!(CMSG_LEN, unsafe {
-            libc::CMSG_SPACE(mem::size_of::<libc::c_int>() as _) as usize
-        });
+        assert!(
+            CMSG_LEN >= unsafe { libc::CMSG_SPACE(mem::size_of::<libc::c_int>() as _) as usize }
+        );
         assert!(
             mem::align_of::<libc::cmsghdr>() <= mem::align_of::<cmsg::Aligned<[u8; 0]>>(),
             "control message buffers will be misaligned"
         );
 
         let addr = self.local_addr()?;
 
-        if addr.is_ipv4() || !self.only_v6()? {
+        if addr.is_ipv4() || (!cfg!(target_os = "macos") && !self.only_v6()?) {
+            let on: libc::c_int = 1;
             let rc = unsafe {
                 libc::setsockopt(
                     self.as_raw_fd(),
                     libc::IPPROTO_IP,
                     libc::IP_RECVTOS,
-                    &true as *const _ as _,
-                    1,
+                    &on as *const _ as _,
+                    mem::size_of_val(&on) as _,
                 )
             };
             if rc == -1 {
@@ -54,7 +55,7 @@ impl super::UdpExt for UdpSocket {
                     libc::IPPROTO_IPV6,
                     libc::IPV6_RECVTCLASS,
                     &on as *const _ as _,
-                    mem::size_of::<libc::c_int>() as _,
+                    mem::size_of_val(&on) as _,
                 )
             };
             if rc == -1 {

quinn/src/tests.rs

@@ -25,7 +25,7 @@ fn echo_v4() {
 }
 
 #[test]
-#[cfg(target_os = "linux")] // Dual-stack sockets aren't the default anywhere else.
+//#[cfg(target_os = "linux")] // Dual-stack sockets aren't the default anywhere else.
 fn echo_dualstack() {
     run_echo(
         SocketAddr::new(IpAddr::V6(Ipv6Addr::UNSPECIFIED), 0),