1 //! socket helpers.
2
3 use std::io::{Error, Result};
4 use std::mem::{size_of, zeroed};
5 use std::os::unix::ffi::OsStrExt;
6 use std::os::unix::net::UnixDatagram;
7 use std::os::unix::prelude::{AsRawFd, RawFd};
8 use std::path::Path;
9 use std::ptr;
10
11 use libc::*;
12
13 const CMSG_BUFSIZE: usize = 64;
14
15 #[repr(C)]
16 union AlignedBuffer<T: Copy + Clone> {
17 buffer: T,
18 align: cmsghdr,
19 }
20
assert_cmsg_bufsize()21 fn assert_cmsg_bufsize() {
22 let space_one_fd = unsafe { CMSG_SPACE(size_of::<RawFd>() as u32) };
23 assert!(
24 space_one_fd <= CMSG_BUFSIZE as u32,
25 "cmsghdr buffer too small (< {}) to hold a single fd",
26 space_one_fd
27 );
28 }
29
30 #[cfg(test)]
31 #[test]
cmsg_buffer_size_for_one_fd()32 fn cmsg_buffer_size_for_one_fd() {
33 assert_cmsg_bufsize()
34 }
35
send_one_fd_to<P: AsRef<Path>>(socket: &UnixDatagram, fd: RawFd, path: P) -> Result<usize>36 pub fn send_one_fd_to<P: AsRef<Path>>(socket: &UnixDatagram, fd: RawFd, path: P) -> Result<usize> {
37 assert_cmsg_bufsize();
38
39 let mut addr: sockaddr_un = unsafe { zeroed() };
40 let path_bytes = path.as_ref().as_os_str().as_bytes();
41 // path_bytes may have at most sun_path + 1 bytes, to account for the trailing NUL byte.
42 if addr.sun_path.len() <= path_bytes.len() {
43 return Err(Error::from_raw_os_error(ENAMETOOLONG));
44 }
45
46 addr.sun_family = AF_UNIX as _;
47 unsafe {
48 std::ptr::copy_nonoverlapping(
49 path_bytes.as_ptr(),
50 addr.sun_path.as_mut_ptr() as *mut u8,
51 path_bytes.len(),
52 )
53 };
54
55 let mut msg: msghdr = unsafe { zeroed() };
56 // Set the target address.
57 msg.msg_name = &mut addr as *mut _ as *mut c_void;
58 msg.msg_namelen = size_of::<sockaddr_un>() as socklen_t;
59
60 // We send no data body with this message.
61 msg.msg_iov = ptr::null_mut();
62 msg.msg_iovlen = 0;
63
64 // Create and fill the control message buffer with our file descriptor
65 let mut cmsg_buffer = AlignedBuffer {
66 buffer: ([0u8; CMSG_BUFSIZE]),
67 };
68 msg.msg_control = unsafe { cmsg_buffer.buffer.as_mut_ptr() as _ };
69 msg.msg_controllen = unsafe { CMSG_SPACE(size_of::<RawFd>() as _) as _ };
70
71 let mut cmsg: &mut cmsghdr =
72 unsafe { CMSG_FIRSTHDR(&msg).as_mut() }.expect("Control message buffer exhausted");
73
74 cmsg.cmsg_level = SOL_SOCKET;
75 cmsg.cmsg_type = SCM_RIGHTS;
76 cmsg.cmsg_len = unsafe { CMSG_LEN(size_of::<RawFd>() as _) as _ };
77
78 unsafe { ptr::write(CMSG_DATA(cmsg) as *mut RawFd, fd) };
79
80 let result = unsafe { sendmsg(socket.as_raw_fd(), &msg, libc::MSG_NOSIGNAL) };
81
82 if result < 0 {
83 Err(Error::last_os_error())
84 } else {
85 // sendmsg returns the number of bytes written
86 Ok(result as usize)
87 }
88 }
89