Rust 1.46.0 compatibility

Rust doesn't allow mem::transmute in a const fn until 1.56.0.  And it
doesn't allow Ipv4Addr::octets in a const fn until 1.50.0

Author: asomers

Cargo.toml

@@ -30,7 +30,6 @@ targets = [
 libc = { version = "0.2.121", features = [ "extra_traits" ] }
 bitflags = "1.1"
 cfg-if = "1.0"
-static_assertions = "1.1.0"
 
 [target.'cfg(not(target_os = "redox"))'.dependencies]
 memoffset = { version = "0.6.3", optional = true }

src/sys/socket/addr.rs

@@ -31,30 +31,24 @@ use crate::sys::socket::addr::sys_control::SysControlAddr;
 pub use self::datalink::LinkAddr;
 #[cfg(any(target_os = "android", target_os = "linux"))]
 pub use self::vsock::VsockAddr;
-#[cfg(feature = "net")]
-use static_assertions::const_assert_eq;
 
 /// Convert a std::net::Ipv4Addr into the libc form.
-// In the standard library, this is a simple newtype, but it doesn't expose
-// the inner libc type, so we must use a pointer cast.
 #[cfg(feature = "net")]
-pub(crate) const fn ipv4addr_to_libc(addr: net::Ipv4Addr) -> libc::in_addr {
-    const_assert_eq!(mem::size_of::<libc::in_addr>(),
-                     mem::size_of::<net::Ipv4Addr>());
-    unsafe {
-        *(&addr as *const net::Ipv4Addr as *const libc::in_addr)
+pub(crate) fn ipv4addr_to_libc(addr: net::Ipv4Addr) -> libc::in_addr {
+    let octets = addr.octets();
+    libc::in_addr {
+        s_addr: u32::to_be(((octets[0] as u32) << 24) |
+            ((octets[1] as u32) << 16) |
+            ((octets[2] as u32) << 8) |
+            (octets[3] as u32))
     }
 }
 
 /// Convert a std::net::Ipv6Addr into the libc form.
-// In the standard library, this is a simple newtype, but it doesn't expose
-// the inner libc type, so we must use a pointer cast.
 #[cfg(feature = "net")]
-pub(crate) const fn ipv6addr_to_libc(addr: &net::Ipv6Addr) -> &libc::in6_addr {
-    const_assert_eq!(mem::size_of::<libc::in6_addr>(),
-                     mem::size_of::<net::Ipv6Addr>());
-    unsafe {
-        &*(addr as *const net::Ipv6Addr as *const libc::in6_addr)
+pub(crate) const fn ipv6addr_to_libc(addr: &net::Ipv6Addr) -> libc::in6_addr {
+    libc::in6_addr {
+        s6_addr: addr.octets()
     }
 }
 
@@ -1311,7 +1305,7 @@ impl From<net::SocketAddrV6> for SockaddrIn6 {
             sin6_len: mem::size_of::<libc::sockaddr_in6>() as u8,
             sin6_family: AddressFamily::Inet6 as sa_family_t,
             sin6_port: addr.port().to_be(),  // network byte order
-            sin6_addr: *ipv6addr_to_libc(addr.ip()),
+            sin6_addr: ipv6addr_to_libc(addr.ip()),
             sin6_flowinfo: addr.flowinfo(),  // host byte order
             sin6_scope_id: addr.scope_id(),  // host byte order
             .. unsafe { mem::zeroed() }

src/sys/socket/mod.rs

@@ -504,11 +504,13 @@ impl IpMembershipRequest {
     pub fn new(group: net::Ipv4Addr, interface: Option<net::Ipv4Addr>)
         -> Self
     {
+        let imr_addr = match interface {
+            None => net::Ipv4Addr::UNSPECIFIED,
+            Some(addr) => addr
+        };
         IpMembershipRequest(libc::ip_mreq {
             imr_multiaddr: ipv4addr_to_libc(group),
-            imr_interface: ipv4addr_to_libc(
-                interface.unwrap_or(net::Ipv4Addr::UNSPECIFIED)
-            ),
+            imr_interface: ipv4addr_to_libc(imr_addr)
         })
     }
 }
@@ -524,7 +526,7 @@ impl Ipv6MembershipRequest {
     /// Instantiate a new `Ipv6MembershipRequest`
     pub const fn new(group: net::Ipv6Addr) -> Self {
         Ipv6MembershipRequest(libc::ipv6_mreq {
-            ipv6mr_multiaddr: *ipv6addr_to_libc(&group),
+            ipv6mr_multiaddr: ipv6addr_to_libc(&group),
             ipv6mr_interface: 0,
         })
     }