Fix struct msghdr types on non-Linux platforms.

http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/sys_socket.h.html

Author: kinetiknz

CHANGELOG.md

@@ -66,6 +66,8 @@ This project adheres to [Semantic Versioning](http://semver.org/).
   ([#623](https://github.com/nix-rust/nix/pull/623))
 - Multiple constants related to the termios API have now been properly defined for
   all supported platforms. ([#527](https://github.com/nix-rust/nix/pull/527))
+- Fixed field types of `sys::socket::ffi::{msghdr, cmsghdr}` on
+  non-Linux platforms.  ([#](https://...))
 
 ## [0.8.1] 2017-04-16
 

nix-test/src/lib.rs

@@ -36,8 +36,8 @@ pub fn assert_size_of<T>(name: &str) {
         assert!(expect > 0, "undefined type {}", name);
 
         if mem::size_of::<T>() != expect {
-            panic!("incorrectly sized type; expect={}; actual={}",
-                   expect, mem::size_of::<T>());
+            panic!("incorrectly sized type; type={} expect={}; actual={}",
+                   name, expect, mem::size_of::<T>());
         }
     }
 }

nix-test/src/sizes.c

@@ -24,6 +24,8 @@ size_of(const char* type) {
 
     // sys/socket
     SIZE_OF_S(sockaddr_storage);
+    SIZE_OF_S(msghdr);
+    SIZE_OF_S(cmsghdr);
 
     // sys/uio
     SIZE_OF_S(iovec);

src/sys/socket/ffi.rs

@@ -3,7 +3,10 @@
 
 pub use libc::{socket, listen, bind, accept, connect, setsockopt, sendto, recvfrom, getsockname, getpeername, recv, send};
 
-use libc::{c_int, c_void, socklen_t, size_t, ssize_t};
+use libc::{c_int, c_void, socklen_t, ssize_t};
+
+#[cfg(not(target_os = "macos"))]
+use libc::size_t;
 
 #[cfg(target_os = "macos")]
 use libc::c_uint;
@@ -18,10 +21,22 @@ pub type type_of_cmsg_len = socklen_t;
 
 // OSX always aligns struct cmsghdr as if it were a 32-bit OS
 #[cfg(target_os = "macos")]
-pub type type_of_cmsg_data = c_uint;
+pub type align_of_cmsg_data = c_uint;
 
 #[cfg(not(target_os = "macos"))]
-pub type type_of_cmsg_data = size_t;
+pub type align_of_cmsg_data = size_t;
+
+#[cfg(target_os = "linux")]
+pub type type_of_msgiov_len = size_t;
+
+#[cfg(not(target_os = "linux"))]
+pub type type_of_msgiov_len = c_int;
+
+#[cfg(target_os = "linux")]
+pub type type_of_msg_controllen = size_t;
+
+#[cfg(not(target_os = "linux"))]
+pub type type_of_msg_controllen = socklen_t;
 
 // Private because we don't expose any external functions that operate
 // directly on this type; we just use it internally at FFI boundaries.
@@ -33,9 +48,9 @@ pub struct msghdr<'a> {
     pub msg_name: *const c_void,
     pub msg_namelen: socklen_t,
     pub msg_iov: *const IoVec<&'a [u8]>,
-    pub msg_iovlen: size_t,
+    pub msg_iovlen: type_of_msgiov_len,
     pub msg_control: *const c_void,
-    pub msg_controllen: size_t,
+    pub msg_controllen: type_of_msg_controllen,
     pub msg_flags: c_int,
 }
 
@@ -47,7 +62,6 @@ pub struct cmsghdr {
     pub cmsg_len: type_of_cmsg_len,
     pub cmsg_level: c_int,
     pub cmsg_type: c_int,
-    pub cmsg_data: [type_of_cmsg_data; 0]
 }
 
 extern {

src/sys/socket/mod.rs

@@ -85,7 +85,8 @@ unsafe fn copy_bytes<'a, 'b, T: ?Sized>(src: &T, dst: &'a mut &'b mut [u8]) {
 }
 
 
-use self::ffi::{cmsghdr, msghdr, type_of_cmsg_len, type_of_cmsg_data};
+use self::ffi::{cmsghdr, msghdr, type_of_cmsg_len, align_of_cmsg_data,
+                type_of_msgiov_len, type_of_msg_controllen};
 
 /// A structure used to make room in a cmsghdr passed to recvmsg. The
 /// size and alignment match that of a cmsghdr followed by a T, but the
@@ -95,8 +96,11 @@ use self::ffi::{cmsghdr, msghdr, type_of_cmsg_len, type_of_cmsg_data};
 /// To make room for multiple messages, nest the type parameter with
 /// tuples, e.g.
 /// `let cmsg: CmsgSpace<([RawFd; 3], CmsgSpace<[RawFd; 2]>)> = CmsgSpace::new();`
+#[repr(C)]
 pub struct CmsgSpace<T> {
     _hdr: cmsghdr,
+    #[cfg(not(target_os = "macos"))]
+    _pad: [align_of_cmsg_data; 0],
     _data: T,
 }
 
@@ -156,17 +160,18 @@ impl<'a> Iterator for CmsgIterator<'a> {
         }
         self.0 = &buf[cmsg_align(cmsg_len)..];
 
+        let cmsg_data = &buf[cmsg_align(sizeof_cmsghdr)..];
         match (cmsg.cmsg_level, cmsg.cmsg_type) {
             (SOL_SOCKET, SCM_RIGHTS) => unsafe {
                 Some(ControlMessage::ScmRights(
                     slice::from_raw_parts(
-                        &cmsg.cmsg_data as *const _ as *const _, 1)))
+                        cmsg_data.as_ptr() as *const _, 1)))
             },
             (_, _) => unsafe {
                 Some(ControlMessage::Unknown(UnknownCmsg(
                     &cmsg,
                     slice::from_raw_parts(
-                        &cmsg.cmsg_data as *const _ as *const _,
+                        cmsg_data.as_ptr() as *const _,
                         len))))
             }
         }
@@ -191,7 +196,7 @@ pub enum ControlMessage<'a> {
 pub struct UnknownCmsg<'a>(&'a cmsghdr, &'a [u8]);
 
 fn cmsg_align(len: usize) -> usize {
-    let align_bytes = mem::size_of::<type_of_cmsg_data>() - 1;
+    let align_bytes = mem::size_of::<align_of_cmsg_data>() - 1;
     (len + align_bytes) & !align_bytes
 }
 
@@ -213,8 +218,8 @@ impl<'a> ControlMessage<'a> {
         }
     }
 
-    // Unsafe: start and end of buffer must be size_t-aligned (that is,
-    // cmsg_align'd). Updates the provided slice; panics if the buffer
+    // Unsafe: start and end of buffer must be cmsg_align'd.
+    // Updates the provided slice; panics if the buffer
     // is too small.
     unsafe fn encode_into<'b>(&self, buf: &mut &'b mut [u8]) {
         match *self {
@@ -223,7 +228,6 @@ impl<'a> ControlMessage<'a> {
                     cmsg_len: self.len() as type_of_cmsg_len,
                     cmsg_level: SOL_SOCKET,
                     cmsg_type: SCM_RIGHTS,
-                    cmsg_data: [],
                 };
                 copy_bytes(&cmsg, buf);
 
@@ -287,9 +291,9 @@ pub fn sendmsg<'a>(fd: RawFd, iov: &[IoVec<&'a [u8]>], cmsgs: &[ControlMessage<'
         msg_name: name as *const c_void,
         msg_namelen: namelen,
         msg_iov: iov.as_ptr(),
-        msg_iovlen: iov.len() as size_t,
+        msg_iovlen: iov.len() as type_of_msgiov_len,
         msg_control: cmsg_ptr,
-        msg_controllen: capacity as size_t,
+        msg_controllen: capacity as type_of_msg_controllen,
         msg_flags: 0,
     };
     let ret = unsafe { ffi::sendmsg(fd, &mhdr, flags.bits()) };
@@ -310,9 +314,9 @@ pub fn recvmsg<'a, T>(fd: RawFd, iov: &[IoVec<&mut [u8]>], cmsg_buffer: Option<&
         msg_name: &mut address as *const _ as *const c_void,
         msg_namelen: mem::size_of::<sockaddr_storage>() as socklen_t,
         msg_iov: iov.as_ptr() as *const IoVec<&[u8]>, // safe cast to add const-ness
-        msg_iovlen: iov.len() as size_t,
+        msg_iovlen: iov.len() as type_of_msgiov_len,
         msg_control: msg_control as *const c_void,
-        msg_controllen: msg_controllen as size_t,
+        msg_controllen: msg_controllen as type_of_msg_controllen,
         msg_flags: 0,
     };
     let ret = unsafe { ffi::recvmsg(fd, &mut mhdr, flags.bits()) };
@@ -692,6 +696,8 @@ pub fn shutdown(df: RawFd, how: Shutdown) -> Result<()> {
 
 #[test]
 pub fn test_struct_sizes() {
-    use nixtest;
-    nixtest::assert_size_of::<sockaddr_storage>("sockaddr_storage");
+    use nixtest::assert_size_of;
+    assert_size_of::<sockaddr_storage>("sockaddr_storage");
+    assert_size_of::<msghdr>("msghdr");
+    assert_size_of::<cmsghdr>("cmsghdr");
 }