#include <sys/socket.h>
#include <sys/un.h>
#include <string.h>
#include <stddef.h>

static int
send_fd(int unix_fd, int fd)
{
	struct msghdr msgh;
	struct cmsghdr *cmsg;
	char buf[CMSG_SPACE (sizeof (fd))];

	memset(&msgh, 0, sizeof(msgh));
	memset(buf, 0, sizeof(buf));

	msgh.msg_control = buf;
	msgh.msg_controllen = sizeof (buf);

	cmsg = CMSG_FIRSTHDR(&msgh);
	cmsg->cmsg_len = CMSG_LEN(sizeof (fd));
	cmsg->cmsg_level = SOL_SOCKET;
	cmsg->cmsg_type = SCM_RIGHTS;

	msgh.msg_controllen = cmsg->cmsg_len;

	memcpy(CMSG_DATA(cmsg), &fd, sizeof (fd));
	return (sendmsg(unix_fd, &msgh, 0));
}


int
main(void)
{
	int fd[2], ff[2];
	int target;

	if (socketpair(PF_UNIX, SOCK_SEQPACKET, 0, fd) == -1)
		return (1);

	for (;;) {
		if (socketpair(PF_UNIX, SOCK_SEQPACKET, 0, ff) == -1)
			return (2);
		send_fd(ff[0], fd[0]);
		send_fd(ff[0], fd[1]);
		close(fd[1]);
		close(fd[0]);
		fd[0] = ff[0];
		fd[1] = ff[1];
	}
	return (0);
}