/// Send a message on a socket. Allow sending ancillary data.
pub unsafe fn sendmsg(sockfd: i32, msg: &msghdr_t, flags: i32) -> Result<ssize_t, Errno> {
let sockfd = sockfd as usize;
let msg_ptr = msg as *const msghdr_t as usize;
let flags = flags as usize;
syscall3(SYS_SENDMSG, sockfd, msg_ptr, flags).map(|ret| ret as ssize_t)
}