1 /* $OpenBSD: mcontrol-stream.c,v 1.1 2018/12/19 21:21:59 bluhm Exp $ */
2 /*
3 * Copyright (c) 2018 Alexander Bluhm <bluhm@openbsd.org>
4 *
5 * Permission to use, copy, modify, and distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
8 *
9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16 */
17
18 #include <sys/socket.h>
19 #include <sys/wait.h>
20
21 #include <err.h>
22 #include <fcntl.h>
23 #include <string.h>
24 #include <unistd.h>
25
26 int
main(int argc,char * argv[])27 main(int argc, char *argv[])
28 {
29 pid_t pid;
30 int fd, s[2], status;
31 char str[] = "foo";
32 struct msghdr msg;
33 struct cmsghdr *cmsg;
34 union {
35 struct cmsghdr hdr;
36 unsigned char buf[CMSG_SPACE(sizeof(int))];
37 } cmsgbuf;
38 struct iovec io_vector[1];
39
40 if ((fd = open("/dev/null", O_RDONLY)) == -1)
41 err(1, "open");
42 if (socketpair(AF_UNIX, SOCK_STREAM, 0, s) == -1)
43 err(1, "socketpair");
44
45 if ((pid = fork()) == -1)
46 err(1, "fork");
47 if (pid == 0) {
48 char buf[16];
49 ssize_t n;
50
51 /*
52 * The first recv(2) will block until the second control
53 * message causes a short read.
54 */
55 if ((n = recv(s[1], buf, sizeof(buf), MSG_WAITALL)) == -1)
56 err(1, "recv 1");
57 if ((size_t)n != strlen(str))
58 errx(1, "recv 1: len %zd", n);
59 if ((n = recv(s[1], buf, sizeof(buf), 0)) == -1)
60 err(1, "recv 2");
61 if ((size_t)n != strlen(str))
62 errx(1, "recv 2: len %zd", n);
63 _exit(0);
64 }
65
66 io_vector[0].iov_base = str;
67 io_vector[0].iov_len = strlen(str);
68
69 memset(&msg, 0, sizeof(msg));
70 msg.msg_control = &cmsgbuf.buf;
71 msg.msg_controllen = sizeof(cmsgbuf.buf);
72 msg.msg_iov = io_vector;
73 msg.msg_iovlen = 1;
74
75 cmsg = CMSG_FIRSTHDR(&msg);
76 cmsg->cmsg_len = CMSG_LEN(sizeof(int));
77 cmsg->cmsg_level = SOL_SOCKET;
78 cmsg->cmsg_type = SCM_RIGHTS;
79 *(int *)CMSG_DATA(cmsg) = fd;
80
81 if (sendmsg(s[0], &msg, 0) == -1)
82 err(1, "sendmsg 1");
83
84 /* Wait until child is blocking in recv(2) MSG_WAITALL syscall. */
85 sleep(2);
86
87 /* This will insert a control mbuf while soreceive() is sleeping. */
88 if (sendmsg(s[0], &msg, 0) == -1)
89 err(1, "sendmsg 2");
90
91 if (close(s[0]) == -1)
92 err(1, "close");
93
94 if (waitpid(pid, &status, 0) == -1)
95 err(1, "waitpid");
96 if (status != 0)
97 errx(1, "child: %d", status);
98
99 return 0;
100 }
101