Don't assume memory layout of std::net::SocketAddr

src/sys/unix/net.rs

@@ -1,4 +1,4 @@
-use std::net::SocketAddr;
+use std::net::{Ipv4Addr, Ipv6Addr, SocketAddr, SocketAddrV4, SocketAddrV6};
 
 pub(crate) fn new_ip_socket(
     addr: SocketAddr,
@@ -64,32 +64,76 @@ pub(crate) fn new_socket(
     socket
 }
 
-pub(crate) fn socket_addr(addr: &SocketAddr) -> (*const libc::sockaddr, libc::socklen_t) {
-    use std::mem::size_of_val;
+/// A type with the same memory layout as `libc::sockaddr`. Used in converting Rust level
+/// SocketAddr* types into their system representation. The benefit of this specific
+/// type over using `libc::sockaddr_storage` is that this type is exactly as large as it
+/// needs to be and not a lot larger. And it can be initialized cleaner from Rust.
+#[repr(C)]
+pub(crate) union SocketAddrCRepr {
+    v4: libc::sockaddr_in,
+    v6: libc::sockaddr_in6,
+}
+
+impl SocketAddrCRepr {
+    pub fn as_ptr(&self) -> *const libc::sockaddr {
+        self as *const _ as *const libc::sockaddr
+    }
+}
+
+/// Converts a Rust `SocketAddr` into the system representation.
+pub(crate) fn socket_addr(addr: &SocketAddr) -> (SocketAddrCRepr, libc::socklen_t) {
+    use std::mem;
 
     match addr {
-        SocketAddr::V4(ref addr) => (
-            addr as *const _ as *const libc::sockaddr,
-            size_of_val(addr) as libc::socklen_t,
-        ),
-        SocketAddr::V6(ref addr) => (
-            addr as *const _ as *const libc::sockaddr,
-            size_of_val(addr) as libc::socklen_t,
-        ),
+        SocketAddr::V4(ref a) => {
+            // `s_addr` is stored as BE on all machine and the array is in BE order.
+            // So the native endian conversion method is used so that it's never swapped.
+            let sin_addr = libc::in_addr { s_addr: u32::from_ne_bytes(a.ip().octets()) };
+
+            let sockaddr_in = libc::sockaddr_in {
+                sin_family: libc::AF_INET as libc::sa_family_t,
+                sin_port: a.port().to_be(),
+                sin_addr,
+                ..unsafe { mem::zeroed() }
+            };
+
+            let sockaddr = SocketAddrCRepr { v4: sockaddr_in };
+            (sockaddr, mem::size_of::<libc::sockaddr_in>() as libc::socklen_t)
+        }
+        SocketAddr::V6(ref a) => {
+            let sockaddr_in6 = libc::sockaddr_in6 {
+                sin6_family: libc::AF_INET6 as libc::sa_family_t,
+                sin6_port: a.port().to_be(),
+                sin6_addr: libc::in6_addr { s6_addr: a.ip().octets() },
+                sin6_flowinfo: a.flowinfo(),
+                sin6_scope_id: a.scope_id(),
+                ..unsafe { mem::zeroed() }
+            };
+
+            let sockaddr = SocketAddrCRepr { v6: sockaddr_in6 };
+            (sockaddr, mem::size_of::<libc::sockaddr_in6>() as libc::socklen_t)
+        }
     }
 }
 
-/// `storage` must be initialised to `sockaddr_in` or `sockaddr_in6`.
+/// Converts a `libc::sockaddr` compatible struct into a native Rust `SocketAddr`.
+/// SAFETY: `storage` must be initialised to `sockaddr_in` or `sockaddr_in6`.
 pub(crate) unsafe fn to_socket_addr(
     storage: *const libc::sockaddr_storage,
 ) -> std::io::Result<SocketAddr> {
     match (*storage).ss_family as libc::c_int {
-        libc::AF_INET => Ok(SocketAddr::V4(
-            *(storage as *const libc::sockaddr_in as *const _),
-        )),
-        libc::AF_INET6 => Ok(SocketAddr::V6(
-            *(storage as *const libc::sockaddr_in6 as *const _),
-        )),
+        libc::AF_INET => {
+            let addr: &libc::sockaddr_in = &*(storage as *const libc::sockaddr_in);
+            let ip = Ipv4Addr::from(addr.sin_addr.s_addr.to_ne_bytes());
+            let port = u16::from_be(addr.sin_port);
+            Ok(SocketAddr::V4(SocketAddrV4::new(ip, port)))
+        },
+        libc::AF_INET6 => {
+            let addr: &libc::sockaddr_in6 = &*(storage as *const libc::sockaddr_in6);
+            let ip = Ipv6Addr::from(addr.sin6_addr.s6_addr);
+            let port = u16::from_be(addr.sin6_port);
+            Ok(SocketAddr::V6(SocketAddrV6::new(ip, port, addr.sin6_flowinfo, addr.sin6_scope_id)))
+        },
         _ => Err(std::io::ErrorKind::InvalidInput.into()),
     }
 }

src/sys/unix/tcp.rs

@@ -20,14 +20,14 @@ pub(crate) fn new_v6_socket() -> io::Result<TcpSocket> {
 
 pub(crate) fn bind(socket: TcpSocket, addr: SocketAddr) -> io::Result<()> {
     let (raw_addr, raw_addr_length) = socket_addr(&addr);
-    syscall!(bind(socket, raw_addr, raw_addr_length))?;
+    syscall!(bind(socket, raw_addr.as_ptr(), raw_addr_length))?;
     Ok(())
 }
 
 pub(crate) fn connect(socket: TcpSocket, addr: SocketAddr) -> io::Result<net::TcpStream> {
     let (raw_addr, raw_addr_length) = socket_addr(&addr);
 
-    match syscall!(connect(socket, raw_addr, raw_addr_length)) {
+    match syscall!(connect(socket, raw_addr.as_ptr(), raw_addr_length)) {
         Err(err) if err.raw_os_error() != Some(libc::EINPROGRESS) => {
             Err(err)
         }

src/sys/unix/udp.rs

@@ -11,7 +11,7 @@ pub fn bind(addr: SocketAddr) -> io::Result<net::UdpSocket> {
 
     socket.and_then(|socket| {
         let (raw_addr, raw_addr_length) = socket_addr(&addr);
-        syscall!(bind(socket, raw_addr, raw_addr_length))
+        syscall!(bind(socket, raw_addr.as_ptr(), raw_addr_length))
             .map_err(|err| {
                 // Close the socket if we hit an error, ignoring the error
                 // from closing since we can't pass back two errors.