#include <stdio.h>
#include <sys/socket.h>

int main(void)
{
   int sd[2];
   int r;
   struct iovec vec;
   struct msghdr msg = { 0 };
   union {
      char buf[CMSG_SPACE(0)];
      struct cmsghdr align;
   } u;
   struct cmsghdr* cmsg;

   msg.msg_iov = &vec;
   msg.msg_iovlen = 1;
   msg.msg_control = u.buf;
   msg.msg_controllen = sizeof(u.buf);
   cmsg = CMSG_FIRSTHDR(&msg);
   cmsg->cmsg_level = SOL_SOCKET;
   cmsg->cmsg_type = SCM_RIGHTS;
   cmsg->cmsg_len = CMSG_LEN(0);

   vec.iov_base = "hello";
   vec.iov_len = 5;

   r = socketpair(PF_LOCAL, SOCK_STREAM, 0, sd);
   if (r == -1) {
      perror("socketpair");
      return 1;
   }

   r = sendmsg(sd[0], &msg, 0);
   if (r == -1) {
      perror("sendmsg");
      return 1;
   }

   r = recvmsg(sd[1], &msg, 0);
   if (r == -1) {
      perror("recvmsg");
      return 1;
   }
   return 0;
}


/*
import socket

sd1, sd2 = socket.socketpair()

sd1.sendmsg([b"hello"], [(socket.SOL_SOCKET, socket.SCM_RIGHTS, b"")])
sd2.recvmsg(1)
*/