/*      $OpenBSD: mcontrol-stream.c,v 1.1 2018/12/19 21:21:59 bluhm Exp $       */
/*
 * Copyright (c) 2018 Alexander Bluhm <bluhm@openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

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

#include <err.h>
#include <fcntl.h>
#include <string.h>
#include <unistd.h>

int
main(int argc, char *argv[])
{
        pid_t pid;
        int fd, s[2], status;
        char str[] = "foo";
        struct msghdr msg;
        struct cmsghdr *cmsg;
        union {
                struct cmsghdr hdr;
                unsigned char buf[CMSG_SPACE(sizeof(int))];
        } cmsgbuf;
        struct iovec io_vector[1];

        if ((fd = open("/dev/null", O_RDONLY)) == -1)
                err(1, "open");
        if (socketpair(AF_UNIX, SOCK_STREAM, 0, s) == -1)
                err(1, "socketpair");

        if ((pid = fork()) == -1)
                err(1, "fork");
        if (pid == 0) {
                char buf[16];
                ssize_t n;

                /*
                 * The first recv(2) will block until the second control
                 * message causes a short read.
                 */
                if ((n = recv(s[1], buf, sizeof(buf), MSG_WAITALL)) == -1)
                        err(1, "recv 1");
                if ((size_t)n != strlen(str))
                        errx(1, "recv 1: len %zd", n);
                if ((n = recv(s[1], buf, sizeof(buf), 0)) == -1)
                        err(1, "recv 2");
                if ((size_t)n != strlen(str))
                        errx(1, "recv 2: len %zd", n);
                _exit(0);
        }

        io_vector[0].iov_base = str;
        io_vector[0].iov_len = strlen(str);

        memset(&msg, 0, sizeof(msg));
        msg.msg_control = &cmsgbuf.buf;
        msg.msg_controllen = sizeof(cmsgbuf.buf);
        msg.msg_iov = io_vector;
        msg.msg_iovlen = 1;

        cmsg = CMSG_FIRSTHDR(&msg);
        cmsg->cmsg_len = CMSG_LEN(sizeof(int));
        cmsg->cmsg_level = SOL_SOCKET;
        cmsg->cmsg_type = SCM_RIGHTS;
        *(int *)CMSG_DATA(cmsg) = fd;

        if (sendmsg(s[0], &msg, 0) == -1)
                err(1, "sendmsg 1");

        /* Wait until child is blocking in recv(2) MSG_WAITALL syscall. */
        sleep(2);

        /* This will insert a control mbuf while soreceive() is sleeping. */
        if (sendmsg(s[0], &msg, 0) == -1)
                err(1, "sendmsg 2");

        if (close(s[0]) == -1)
                err(1, "close");

        if (waitpid(pid, &status, 0) == -1)
                err(1, "waitpid");
        if (status != 0)
                errx(1, "child: %d", status);

        return 0;
}