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

src/socket.rs

@@ -32,7 +32,7 @@ impl Socket {
     pub fn bind(&self, addr: &SocketAddr) -> io::Result<()> {
         let (addr, len) = addr2raw(addr);
         unsafe {
-            ::cvt(c::bind(self.inner.raw(), addr, len as c::socklen_t)).map(|_| ())
+            ::cvt(c::bind(self.inner.raw(), addr.as_ptr(), len as c::socklen_t)).map(|_| ())
         }
     }
 
@@ -45,7 +45,7 @@ impl Socket {
     pub fn connect(&self, addr: &SocketAddr) -> io::Result<()> {
         let (addr, len) = addr2raw(addr);
         unsafe {
-            ::cvt(c::connect(self.inner.raw(), addr, len)).map(|_| ())
+            ::cvt(c::connect(self.inner.raw(), addr.as_ptr(), len)).map(|_| ())
         }
     }
 
@@ -84,17 +84,130 @@ impl ::IntoInner for Socket {
     fn into_inner(self) -> sys::Socket { self.inner }
 }
 
-fn addr2raw(addr: &SocketAddr) -> (*const c::sockaddr, c::socklen_t) {
-    match *addr {
-        SocketAddr::V4(ref a) => {
-            (a as *const _ as *const _, mem::size_of_val(a) as c::socklen_t)
-        }
-        SocketAddr::V6(ref a) => {
-            (a as *const _ as *const _, mem::size_of_val(a) as c::socklen_t)
-        }
+/// A type with the same memory layout as `c::sockaddr`. Used in converting Rust level
+/// SocketAddr* types into their system representation. The benefit of this specific
+/// type over using `c::sockaddr_storage` is that this type is exactly as large as it
+/// needs to be and not a lot larger.
+#[repr(C)]
+pub(crate) union SocketAddrCRepr {
+    v4: c::sockaddr_in,
+    v6: c::sockaddr_in6,
+}
+
+impl SocketAddrCRepr {
+    pub(crate) fn as_ptr(&self) -> *const c::sockaddr {
+        self as *const _ as *const c::sockaddr
     }
 }
 
+fn addr2raw(addr: &SocketAddr) -> (SocketAddrCRepr, c::socklen_t) {
+    match addr {
+        &SocketAddr::V4(ref v4) => addr2raw_v4(v4),
+        &SocketAddr::V6(ref v6) => addr2raw_v6(v6),
+    }
+}
+
+#[cfg(unix)]
+fn addr2raw_v4(addr: &SocketAddrV4) -> (SocketAddrCRepr, c::socklen_t) {
+    let sin_addr = c::in_addr {
+        s_addr: u32::from(*addr.ip()).to_be(),
+    };
+
+    let sockaddr = SocketAddrCRepr {
+        v4: c::sockaddr_in {
+            sin_family: c::AF_INET as c::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,
+        },
+    };
+    (sockaddr, mem::size_of::<c::sockaddr_in>() as c::socklen_t)
+}
+
+#[cfg(windows)]
+fn addr2raw_v4(addr: &SocketAddrV4) -> (SocketAddrCRepr, c::socklen_t) {
+    let sin_addr = unsafe {
+        let mut s_un = mem::zeroed::<c::in_addr_S_un>();
+        *s_un.S_addr_mut() = u32::from(*addr.ip()).to_be();
+        c::IN_ADDR { S_un: s_un }
+    };
+
+    let sockaddr = SocketAddrCRepr {
+        v4: c::sockaddr_in {
+            sin_family: c::AF_INET as c::sa_family_t,
+            sin_port: addr.port().to_be(),
+            sin_addr,
+            sin_zero: [0; 8],
+        },
+    };
+    (sockaddr, mem::size_of::<c::sockaddr_in>() as c::socklen_t)
+}
+
+#[cfg(unix)]
+fn addr2raw_v6(addr: &SocketAddrV6) -> (SocketAddrCRepr, c::socklen_t) {
+    let sin6_addr = {
+        let mut sin6_addr = unsafe { mem::zeroed::<c::in6_addr>() };
+        sin6_addr.s6_addr = addr.ip().octets();
+        sin6_addr
+    };
+
+    let sockaddr = SocketAddrCRepr {
+        v6: c::sockaddr_in6 {
+            sin6_family: c::AF_INET6 as c::sa_family_t,
+            sin6_port: addr.port().to_be(),
+            sin6_addr,
+            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,
+        },
+    };
+    (sockaddr, mem::size_of::<c::sockaddr_in6>() as c::socklen_t)
+}
+
+#[cfg(windows)]
+fn addr2raw_v6(addr: &SocketAddrV6) -> (SocketAddrCRepr, c::socklen_t) {
+    let sin6_addr = unsafe {
+        let mut u = mem::zeroed::<c::in6_addr_u>();
+        *u.Byte_mut() = addr.ip().octets();
+        c::IN6_ADDR { u }
+    };
+    let scope_id = unsafe {
+        let mut u = mem::zeroed::<c::SOCKADDR_IN6_LH_u>();
+        *u.sin6_scope_id_mut() = addr.scope_id();
+        u
+    };
+
+    let sockaddr = SocketAddrCRepr {
+        v6: c::sockaddr_in6 {
+            sin6_family: c::AF_INET6 as c::sa_family_t,
+            sin6_port: addr.port().to_be(),
+            sin6_addr,
+            sin6_flowinfo: addr.flowinfo(),
+            u: scope_id,
+        },
+    };
+    (sockaddr, mem::size_of::<c::sockaddr_in6>() as c::socklen_t)
+}
+
 fn raw2addr(storage: &c::sockaddr_storage, len: c::socklen_t) -> io::Result<SocketAddr> {
     match storage.ss_family as c_int {
         c::AF_INET => {

src/sys/windows/mod.rs

@@ -34,6 +34,7 @@ pub mod c {
     pub use winapi::shared::ws2def::SOCKADDR as sockaddr;
     pub use winapi::shared::ws2def::SOCKADDR_STORAGE as sockaddr_storage;
     pub use winapi::shared::ws2def::SOCKADDR_IN as sockaddr_in;
+    pub use winapi::shared::ws2def::ADDRESS_FAMILY as sa_family_t;
     pub use winapi::shared::ws2ipdef::*;
     pub use winapi::shared::ws2ipdef::SOCKADDR_IN6_LH as sockaddr_in6;
     pub use winapi::shared::ws2ipdef::IP_MREQ as ip_mreq;