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

Fixes #1388.

src/sys/unix/net.rs

@@ -1,4 +1,5 @@
-use std::net::SocketAddr;
+use std::mem;
+use std::net::{Ipv4Addr, Ipv6Addr, SocketAddr, SocketAddrV4, SocketAddrV6};
 
 pub(crate) fn new_ip_socket(
     addr: SocketAddr,
@@ -64,32 +65,99 @@ 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(crate) 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) {
     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 addr) => {
+            // `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(addr.ip().octets()) };
+
+            let sockaddr_in = libc::sockaddr_in {
+                sin_family: libc::AF_INET as libc::sa_family_t,
+                sin_port: addr.port().to_be(),
+                sin_addr,
+                sin_zero: [0; 8],
+                #[cfg(any(
+                    target_os = "dragonfly",
+                    target_os = "freebsd",
+                    target_os = "ios",
+                    target_os = "macos",
+                    target_os = "netbsd",
+                    target_os = "openbsd"
+                ))]
+                sin_len: 0,
+            };
+
+            let sockaddr = SocketAddrCRepr { v4: sockaddr_in };
+            (sockaddr, mem::size_of::<libc::sockaddr_in>() as libc::socklen_t)
+        }
+        SocketAddr::V6(ref addr) => {
+            let sockaddr_in6 = libc::sockaddr_in6 {
+                sin6_family: libc::AF_INET6 as libc::sa_family_t,
+                sin6_port: addr.port().to_be(),
+                sin6_addr: libc::in6_addr { s6_addr: addr.ip().octets() },
+                sin6_flowinfo: addr.flowinfo(),
+                sin6_scope_id: addr.scope_id(),
+                #[cfg(any(
+                    target_os = "dragonfly",
+                    target_os = "freebsd",
+                    target_os = "ios",
+                    target_os = "macos",
+                    target_os = "netbsd",
+                    target_os = "openbsd"
+                ))]
+                sin6_len: 0,
+                #[cfg(any(target_os = "solaris", target_os = "illumos"))]
+                __sin6_src_id: 0,
+            };
+
+            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 have the `ss_family` field correctly initialized.
+/// `storage` must be initialised to a `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 => {
+            // Safety: if the ss_family field is AF_INET then storage must be a sockaddr_in.
+            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 => {
+            // Safety: if the ss_family field is AF_INET6 then storage must be a sockaddr_in6.
+            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.

src/sys/windows/net.rs

@@ -1,10 +1,13 @@
 use std::io;
-use std::mem::size_of_val;
+use std::mem;
 use std::net::SocketAddr;
 use std::sync::Once;
 
 use winapi::ctypes::c_int;
-use winapi::shared::ws2def::SOCKADDR;
+use winapi::shared::inaddr::{in_addr_S_un, IN_ADDR};
+use winapi::shared::in6addr::{in6_addr_u, IN6_ADDR};
+use winapi::shared::ws2def::{AF_INET, AF_INET6, ADDRESS_FAMILY, SOCKADDR, SOCKADDR_IN};
+use winapi::shared::ws2ipdef::{SOCKADDR_IN6_LH, SOCKADDR_IN6_LH_u};
 use winapi::um::winsock2::{ioctlsocket, socket, FIONBIO, INVALID_SOCKET, SOCKET};
 
 /// Initialise the network stack for Windows.
@@ -41,15 +44,65 @@ pub(crate) fn new_socket(domain: c_int, socket_type: c_int) -> io::Result<SOCKET
     })
 }
 
-pub(crate) fn socket_addr(addr: &SocketAddr) -> (*const SOCKADDR, c_int) {
+/// A type with the same memory layout as `SOCKADDR`. Used in converting Rust level
+/// SocketAddr* types into their system representation. The benefit of this specific
+/// type over using `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: SOCKADDR_IN,
+    v6: SOCKADDR_IN6_LH,
+}
+
+impl SocketAddrCRepr {
+    pub(crate) fn as_ptr(&self) -> *const SOCKADDR {
+        self as *const _ as *const SOCKADDR
+    }
+}
+
+pub(crate) fn socket_addr(addr: &SocketAddr) -> (SocketAddrCRepr, c_int) {
     match addr {
-        SocketAddr::V4(ref addr) => (
-            addr as *const _ as *const SOCKADDR,
-            size_of_val(addr) as c_int,
-        ),
-        SocketAddr::V6(ref addr) => (
-            addr as *const _ as *const SOCKADDR,
-            size_of_val(addr) as c_int,
-        ),
+        SocketAddr::V4(ref addr) => {
+            // `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 = unsafe {
+                let mut s_un = mem::zeroed::<in_addr_S_un>();
+                *s_un.S_addr_mut() = u32::from_ne_bytes(addr.ip().octets());
+                IN_ADDR { S_un: s_un }
+            };
+
+            let sockaddr_in = SOCKADDR_IN {
+                sin_family: AF_INET as ADDRESS_FAMILY,
+                sin_port: addr.port().to_be(),
+                sin_addr,
+                sin_zero: [0; 8],
+            };
+
+            let sockaddr = SocketAddrCRepr { v4: sockaddr_in };
+            (sockaddr, mem::size_of::<SOCKADDR_IN>() as c_int)
+        },
+        SocketAddr::V6(ref addr) => {
+            let sin6_addr = unsafe {
+                let mut u = mem::zeroed::<in6_addr_u>();
+                *u.Byte_mut() = addr.ip().octets();
+                IN6_ADDR { u }
+            };
+            let u = unsafe {
+                let mut u = mem::zeroed::<SOCKADDR_IN6_LH_u>();
+                *u.sin6_scope_id_mut() = addr.scope_id();
+                u
+            };
+
+            let sockaddr_in6 = SOCKADDR_IN6_LH {
+                sin6_family: AF_INET6 as ADDRESS_FAMILY,
+                sin6_port: addr.port().to_be(),
+                sin6_addr,
+                sin6_flowinfo: addr.flowinfo(),
+                u,
+            };
+
+            let sockaddr = SocketAddrCRepr { v6: sockaddr_in6 };
+            (sockaddr, mem::size_of::<SOCKADDR_IN6_LH>() as c_int)
+        }
     }
 }

src/sys/windows/tcp.rs

@@ -1,13 +1,13 @@
 use std::io;
 use std::mem::size_of;
-use std::net::{self, SocketAddr, SocketAddrV4, SocketAddrV6};
+use std::net::{self, Ipv4Addr, Ipv6Addr, SocketAddr, SocketAddrV4, SocketAddrV6};
 use std::time::Duration;
 use std::convert::TryInto;
 use std::os::windows::io::FromRawSocket;
 use std::os::windows::raw::SOCKET as StdSocket; // winapi uses usize, stdlib uses u32/u64.
 
 use winapi::ctypes::{c_char, c_int, c_ushort};
-use winapi::shared::ws2def::{SOCKADDR_STORAGE, AF_INET, SOCKADDR_IN};
+use winapi::shared::ws2def::{SOCKADDR_STORAGE, AF_INET, AF_INET6, SOCKADDR_IN};
 use winapi::shared::ws2ipdef::SOCKADDR_IN6_LH;
 
 use winapi::shared::minwindef::{BOOL, TRUE, FALSE};
@@ -35,7 +35,7 @@ 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),
+        bind(socket, raw_addr.as_ptr(), raw_addr_length),
         PartialEq::eq,
         SOCKET_ERROR
     )?;
@@ -48,7 +48,7 @@ pub(crate) fn connect(socket: TcpSocket, addr: SocketAddr) -> io::Result<net::Tc
     let (raw_addr, raw_addr_length) = socket_addr(&addr);
 
     let res = syscall!(
-        connect(socket, raw_addr, raw_addr_length),
+        connect(socket, raw_addr.as_ptr(), raw_addr_length),
         PartialEq::eq,
         SOCKET_ERROR
     );
@@ -108,23 +108,32 @@ pub(crate) fn get_reuseaddr(socket: TcpSocket) -> io::Result<bool> {
 }
 
 pub(crate) fn get_localaddr(socket: TcpSocket) -> io::Result<SocketAddr> {
-    let mut addr: SOCKADDR_STORAGE = unsafe { std::mem::zeroed() };
-    let mut length = std::mem::size_of_val(&addr) as c_int;
+    let mut storage: SOCKADDR_STORAGE = unsafe { std::mem::zeroed() };
+    let mut length = std::mem::size_of_val(&storage) as c_int;
 
     match unsafe { getsockname(
         socket,
-        &mut addr as *mut _ as *mut _,
+        &mut storage as *mut _ as *mut _,
         &mut length
     ) } {
         SOCKET_ERROR => Err(io::Error::last_os_error()),
         _ => {
-            let storage: *const SOCKADDR_STORAGE = (&addr) as *const _;
-            if addr.ss_family as c_int == AF_INET {
-                let sock_addr : SocketAddrV4 = unsafe { *(storage as *const SOCKADDR_IN as *const _) };
-                Ok(sock_addr.into())
+            if storage.ss_family as c_int == AF_INET {
+                // Safety: if the ss_family field is AF_INET then storage must be a sockaddr_in.
+                let addr: &SOCKADDR_IN = unsafe { &*(&storage as *const _ as *const SOCKADDR_IN) };
+                let ip_bytes = unsafe { addr.sin_addr.S_un.S_un_b() };
+                let ip = Ipv4Addr::from([ip_bytes.s_b1, ip_bytes.s_b2, ip_bytes.s_b3, ip_bytes.s_b4]);
+                let port = u16::from_be(addr.sin_port);
+                Ok(SocketAddr::V4(SocketAddrV4::new(ip, port)))
+            } else if storage.ss_family as c_int == AF_INET6 {
+                // Safety: if the ss_family field is AF_INET6 then storage must be a sockaddr_in6.
+                let addr: &SOCKADDR_IN6_LH = unsafe { &*(&storage as *const _ as *const SOCKADDR_IN6_LH) };
+                let ip = Ipv6Addr::from(*unsafe { addr.sin6_addr.u.Byte() });
+                let port = u16::from_be(addr.sin6_port);
+                let scope_id = unsafe { *addr.u.sin6_scope_id() };
+                Ok(SocketAddr::V6(SocketAddrV6::new(ip, port, addr.sin6_flowinfo, scope_id)))
             } else {
-                let sock_addr : SocketAddrV6 = unsafe { *(storage as *const SOCKADDR_IN6_LH as *const _) };
-                Ok(sock_addr.into())
+                Err(std::io::ErrorKind::InvalidInput.into())
             }
         },
     }

src/sys/windows/udp.rs

@@ -12,7 +12,7 @@ pub fn bind(addr: SocketAddr) -> io::Result<net::UdpSocket> {
     new_ip_socket(addr, SOCK_DGRAM).and_then(|socket| {
         let (raw_addr, raw_addr_length) = socket_addr(&addr);
         syscall!(
-            win_bind(socket, raw_addr, raw_addr_length,),
+            win_bind(socket, raw_addr.as_ptr(), raw_addr_length,),
             PartialEq::eq,
             SOCKET_ERROR
         )