/// Receive a msg from a socket.
pub unsafe fn recvmsg(sockfd: i32, msg: &mut msghdr_t, flags: i32) -> Result<ssize_t, Errno> {
    let sockfd = sockfd as usize;
    let msg_ptr = msg as *mut msghdr_t as usize;
    let flags = flags as usize;
    syscall3(SYS_RECVMSG, sockfd, msg_ptr, flags).map(|ret| ret as ssize_t)
}
