Fix misaligned references when using recvmsg with control messages

On some platforms the alignment of cmsg_data could be less than the
alignment of the messages that it contains.  That led to unaligned
reads
on those platforms.  This change fixes the issue by always copying the
message contents into aligned objects.  The change is not 100%
backwards
compatible when using recvmsg.  Users may have to replace code like
this:

```rust
if let ControlMessage::ScmRights(&fds) = cmsg {
```

with this:
```rust
if let ControlMessageOwned::ScmRights(fds) = cmsg {
```

Fixes #999

1 files changed, 17 insertions, 17 deletions

diff --git a/test/sys/test_socket.rs b/test/sys/test_socket.rs
index 5a40574d..5d55c87d 100644
--- a/test/sys/test_socket.rs
+++ b/test/sys/test_socket.rs
@@ -141,7 +141,7 @@ pub fn test_scm_rights() {
     use nix::unistd::{pipe, read, write, close};
     use nix::sys::socket::{socketpair, sendmsg, recvmsg,
                            AddressFamily, SockType, SockFlag,
-                           ControlMessage, MsgFlags};
+                           ControlMessage, ControlMessageOwned, MsgFlags};
 
     let (fd1, fd2) = socketpair(AddressFamily::Unix, SockType::Stream, None, SockFlag::empty())
                      .unwrap();
@@ -164,7 +164,7 @@ pub fn test_scm_rights() {
         let msg = recvmsg(fd2, &iov, Some(&mut cmsgspace), MsgFlags::empty()).unwrap();
 
         for cmsg in msg.cmsgs() {
-            if let ControlMessage::ScmRights(fd) = cmsg {
+            if let ControlMessageOwned::ScmRights(fd) = cmsg {
                 assert_eq!(received_r, None);
                 assert_eq!(fd.len(), 1);
                 received_r = Some(fd[0]);
@@ -195,7 +195,7 @@ fn test_scm_rights_single_cmsg_multiple_fds() {
     use std::os::unix::net::UnixDatagram;
     use std::os::unix::io::{RawFd, AsRawFd};
     use std::thread;
-    use nix::sys::socket::{ControlMessage, MsgFlags,
+    use nix::sys::socket::{ControlMessage, ControlMessageOwned, MsgFlags,
         sendmsg, recvmsg};
     use nix::sys::uio::IoVec;
     use libc;
@@ -215,7 +215,7 @@ fn test_scm_rights_single_cmsg_multiple_fds() {
 
         let mut cmsgs = msg.cmsgs();
         match cmsgs.next() {
-            Some(ControlMessage::ScmRights(fds)) => {
+            Some(ControlMessageOwned::ScmRights(fds)) => {
                 assert_eq!(fds.len(), 2,
                            "unexpected fd count (expected 2 fds, got {})",
                            fds.len());
@@ -277,7 +277,7 @@ fn test_scm_credentials() {
     use nix::unistd::{close, getpid, getuid, getgid};
     use nix::sys::socket::{socketpair, sendmsg, recvmsg, setsockopt,
                            AddressFamily, SockType, SockFlag,
-                           ControlMessage, MsgFlags};
+                           ControlMessage, ControlMessageOwned, MsgFlags};
     use nix::sys::socket::sockopt::PassCred;
 
     let (send, recv) = socketpair(AddressFamily::Unix, SockType::Stream, None, SockFlag::empty())
@@ -304,7 +304,7 @@ fn test_scm_credentials() {
         let mut received_cred = None;
 
         for cmsg in msg.cmsgs() {
-            if let ControlMessage::ScmCredentials(cred) = cmsg {
+            if let ControlMessageOwned::ScmCredentials(cred) = cmsg {
                 assert!(received_cred.is_none());
                 assert_eq!(cred.pid, getpid().as_raw());
                 assert_eq!(cred.uid, getuid().as_raw());
@@ -353,7 +353,7 @@ fn test_impl_scm_credentials_and_rights(mut space: Vec<u8>) {
     use nix::unistd::{pipe, read, write, close, getpid, getuid, getgid};
     use nix::sys::socket::{socketpair, sendmsg, recvmsg, setsockopt,
                            AddressFamily, SockType, SockFlag,
-                           ControlMessage, MsgFlags};
+                           ControlMessage, ControlMessageOwned, MsgFlags};
     use nix::sys::socket::sockopt::PassCred;
 
     let (send, recv) = socketpair(AddressFamily::Unix, SockType::Stream, None, SockFlag::empty())
@@ -390,17 +390,17 @@ fn test_impl_scm_credentials_and_rights(mut space: Vec<u8>) {
 
         for cmsg in msg.cmsgs() {
             match cmsg {
-                ControlMessage::ScmRights(fds) => {
+                ControlMessageOwned::ScmRights(fds) => {
                     assert_eq!(received_r, None, "already received fd");
                     assert_eq!(fds.len(), 1);
                     received_r = Some(fds[0]);
                 }
-                ControlMessage::ScmCredentials(cred) => {
+                ControlMessageOwned::ScmCredentials(cred) => {
                     assert!(received_cred.is_none());
                     assert_eq!(cred.pid, getpid().as_raw());
                     assert_eq!(cred.uid, getuid().as_raw());
                     assert_eq!(cred.gid, getgid().as_raw());
-                    received_cred = Some(*cred);
+                    received_cred = Some(cred);
                 }
                 _ => panic!("unexpected cmsg"),
             }
@@ -542,7 +542,7 @@ pub fn test_recv_ipv4pktinfo() {
     use nix::sys::socket::sockopt::Ipv4PacketInfo;
     use nix::sys::socket::{bind, SockFlag, SockType};
     use nix::sys::socket::{getsockname, setsockopt, socket};
-    use nix::sys::socket::{recvmsg, sendmsg, ControlMessage, MsgFlags};
+    use nix::sys::socket::{recvmsg, sendmsg, ControlMessageOwned, MsgFlags};
     use nix::sys::uio::IoVec;
     use nix::net::if_::*;
 
@@ -592,7 +592,7 @@ pub fn test_recv_ipv4pktinfo() {
 
         let mut cmsgs = msg.cmsgs();
         match cmsgs.next() {
-            Some(ControlMessage::Ipv4PacketInfo(pktinfo)) => {
+            Some(ControlMessageOwned::Ipv4PacketInfo(pktinfo)) => {
                 let i = if_nametoindex(lo_name.as_bytes()).expect("if_nametoindex");
                 assert_eq!(
                     pktinfo.ipi_ifindex as libc::c_uint,
@@ -632,7 +632,7 @@ pub fn test_recvif() {
     use nix::sys::socket::sockopt::{Ipv4RecvIf, Ipv4RecvDstAddr};
     use nix::sys::socket::{bind, SockFlag, SockType};
     use nix::sys::socket::{getsockname, setsockopt, socket, SockAddr};
-    use nix::sys::socket::{recvmsg, sendmsg, ControlMessage, MsgFlags};
+    use nix::sys::socket::{recvmsg, sendmsg, ControlMessageOwned, MsgFlags};
     use nix::sys::uio::IoVec;
 
     let lo_ifaddr = loopback_address(AddressFamily::Inet);
@@ -685,7 +685,7 @@ pub fn test_recvif() {
         let mut rx_recvdstaddr = false;
         for cmsg in msg.cmsgs() {
             match cmsg {
-                ControlMessage::Ipv4RecvIf(dl) => {
+                ControlMessageOwned::Ipv4RecvIf(dl) => {
                     rx_recvif = true;
                     let i = if_nametoindex(lo_name.as_bytes()).expect("if_nametoindex");
                     assert_eq!(
@@ -696,7 +696,7 @@ pub fn test_recvif() {
                         dl.sdl_index
                     );
                 },
-                ControlMessage::Ipv4RecvDstAddr(addr) => {
+                ControlMessageOwned::Ipv4RecvDstAddr(addr) => {
                     rx_recvdstaddr = true;
                     if let SockAddr::Inet(InetAddr::V4(a)) = lo {
                         assert_eq!(a.sin_addr.s_addr,
@@ -742,7 +742,7 @@ pub fn test_recv_ipv6pktinfo() {
     use nix::sys::socket::sockopt::Ipv6RecvPacketInfo;
     use nix::sys::socket::{bind, AddressFamily, SockFlag, SockType};
     use nix::sys::socket::{getsockname, setsockopt, socket};
-    use nix::sys::socket::{recvmsg, sendmsg, ControlMessage, MsgFlags};
+    use nix::sys::socket::{recvmsg, sendmsg, ControlMessageOwned, MsgFlags};
     use nix::sys::uio::IoVec;
 
     let lo_ifaddr = loopback_address(AddressFamily::Inet6);
@@ -791,7 +791,7 @@ pub fn test_recv_ipv6pktinfo() {
 
         let mut cmsgs = msg.cmsgs();
         match cmsgs.next() {
-            Some(ControlMessage::Ipv6PacketInfo(pktinfo)) => {
+            Some(ControlMessageOwned::Ipv6PacketInfo(pktinfo)) => {
                 let i = if_nametoindex(lo_name.as_bytes()).expect("if_nametoindex");
                 assert_eq!(
                     pktinfo.ipi6_ifindex,