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[0.5.x] Don't assume representation of SocketAddr #1046

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Mar 3, 2021
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1 change: 1 addition & 0 deletions quinn/Cargo.toml
Original file line number Diff line number Diff line change
Expand Up @@ -34,6 +34,7 @@ mio = "0.6"
proto = { package = "quinn-proto", path = "../quinn-proto", version = "0.5.2" }
rustls = { version = "0.16", features = ["quic"] }
rustls-native-certs = { version = "0.1.0", optional = true }
socket2 = "0.3"
tracing = "0.1.10"
tokio = { version = "0.2.1", features = ["io-driver", "time"] }
webpki = "0.21"
Expand Down
43 changes: 28 additions & 15 deletions quinn/src/platform/unix.rs
Original file line number Diff line number Diff line change
Expand Up @@ -19,14 +19,6 @@ type IpTosTy = libc::c_int;
impl super::UdpExt for UdpSocket {
fn init_ext(&self) -> io::Result<()> {
// Safety
assert_eq!(
mem::size_of::<SocketAddrV4>(),
mem::size_of::<libc::sockaddr_in>()
);
assert_eq!(
mem::size_of::<SocketAddrV6>(),
mem::size_of::<libc::sockaddr_in6>()
);
assert!(
CMSG_LEN >= unsafe { libc::CMSG_SPACE(mem::size_of::<libc::c_int>() as _) as usize }
);
Expand Down Expand Up @@ -77,9 +69,25 @@ impl super::UdpExt for UdpSocket {
let mut msgs: [libc::mmsghdr; BATCH_SIZE] = unsafe { mem::zeroed() };
let mut iovecs: [libc::iovec; BATCH_SIZE] = unsafe { mem::zeroed() };
let mut cmsgs = [cmsg::Aligned(MaybeUninit::uninit()); BATCH_SIZE];
// This assume_init looks a bit weird because one might think it
// assumes the SockAddr data to be initialized, but that call
// refers to the whole array, which itself is made up of MaybeUninit
// containers. Their presence protects the SockAddr inside from
// being assumed as initialized by the assume_init call.
// TODO: Replace this with uninit_array once it becomes MSRV-stable
let mut addrs: [MaybeUninit<socket2::SockAddr>; BATCH_SIZE] =
unsafe { MaybeUninit::uninit().assume_init() };
for (i, transmit) in transmits.iter().enumerate().take(BATCH_SIZE) {
let dst_addr = unsafe {
std::ptr::write(
addrs[i].as_mut_ptr(),
socket2::SockAddr::from(transmit.destination),
);
&*addrs[i].as_ptr()
};
prepare_msg(
transmit,
dst_addr,
&mut msgs[i].msg_hdr,
&mut iovecs[i],
&mut cmsgs[i],
Expand Down Expand Up @@ -112,7 +120,8 @@ impl super::UdpExt for UdpSocket {
let mut ctrl = cmsg::Aligned(MaybeUninit::uninit());
let mut sent = 0;
while sent < transmits.len() {
prepare_msg(&transmits[sent], &mut hdr, &mut iov, &mut ctrl);
let addr = socket2::SockAddr::from(transmits[sent].destination);
prepare_msg(&transmits[sent], &addr, &mut hdr, &mut iov, &mut ctrl);
let n = unsafe { libc::sendmsg(self.as_raw_fd(), &hdr, 0) };
if n == -1 {
let e = io::Error::last_os_error();
Expand Down Expand Up @@ -198,19 +207,23 @@ const CMSG_LEN: usize = 24;

fn prepare_msg(
transmit: &Transmit,
dst_addr: &socket2::SockAddr,
hdr: &mut libc::msghdr,
iov: &mut libc::iovec,
ctrl: &mut cmsg::Aligned<MaybeUninit<[u8; CMSG_LEN]>>,
) {
iov.iov_base = transmit.contents.as_ptr() as *const _ as *mut _;
iov.iov_len = transmit.contents.len();

let (name, namelen) = match transmit.destination {
SocketAddr::V4(ref addr) => (addr as *const _ as _, mem::size_of::<libc::sockaddr_in>()),
SocketAddr::V6(ref addr) => (addr as *const _ as _, mem::size_of::<libc::sockaddr_in6>()),
};
hdr.msg_name = name;
hdr.msg_namelen = namelen as _;
// SAFETY: Casting the pointer to a mutable one is legal,
// as sendmsg is guaranteed to not alter the mutable pointer
// as per the POSIX spec. See the section on the sys/socket.h
// header for details. The type is only mutable in the first
// place because it is reused by recvmsg as well.
let name = dst_addr.as_ptr() as *mut libc::c_void;
let namelen = dst_addr.len();
hdr.msg_name = name as *mut _;
hdr.msg_namelen = namelen;
hdr.msg_iov = iov;
hdr.msg_iovlen = 1;

Expand Down