1*cb977d3aSmvs /* $OpenBSD: undgram_selfconn.c,v 1.1 2021/12/09 17:25:54 mvs Exp $ */
2*cb977d3aSmvs
3*cb977d3aSmvs /*
4*cb977d3aSmvs * Copyright (c) 2021 Vitaliy Makkoveev <mvs@openbsd.org>
5*cb977d3aSmvs *
6*cb977d3aSmvs * Permission to use, copy, modify, and distribute this software for any
7*cb977d3aSmvs * purpose with or without fee is hereby granted, provided that the above
8*cb977d3aSmvs * copyright notice and this permission notice appear in all copies.
9*cb977d3aSmvs *
10*cb977d3aSmvs * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
11*cb977d3aSmvs * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
12*cb977d3aSmvs * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
13*cb977d3aSmvs * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
14*cb977d3aSmvs * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
15*cb977d3aSmvs * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
16*cb977d3aSmvs * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
17*cb977d3aSmvs */
18*cb977d3aSmvs
19*cb977d3aSmvs /*
20*cb977d3aSmvs * unix(4) datagram socket could be connected to itself. There are two
21*cb977d3aSmvs * cases: temporary connection for sendto(2) syscall and normal connection
22*cb977d3aSmvs * provided by connect(2) syscall.
23*cb977d3aSmvs * Be sure socket doesn't deadlock itself and doesn't crash kernel while
24*cb977d3aSmvs * disconnecting and connecting again.
25*cb977d3aSmvs */
26*cb977d3aSmvs
27*cb977d3aSmvs #include <sys/types.h>
28*cb977d3aSmvs #include <sys/socket.h>
29*cb977d3aSmvs #include <sys/stat.h>
30*cb977d3aSmvs #include <sys/un.h>
31*cb977d3aSmvs #include <stdio.h>
32*cb977d3aSmvs #include <err.h>
33*cb977d3aSmvs #include <string.h>
34*cb977d3aSmvs #include <unistd.h>
35*cb977d3aSmvs
36*cb977d3aSmvs int
main(void)37*cb977d3aSmvs main(void)
38*cb977d3aSmvs {
39*cb977d3aSmvs static struct sockaddr_un sun;
40*cb977d3aSmvs int s, buf;
41*cb977d3aSmvs ssize_t ret;
42*cb977d3aSmvs
43*cb977d3aSmvs umask(0077);
44*cb977d3aSmvs
45*cb977d3aSmvs memset(&sun, 0, sizeof(sun));
46*cb977d3aSmvs sun.sun_len = sizeof(sun);
47*cb977d3aSmvs sun.sun_family = AF_UNIX;
48*cb977d3aSmvs snprintf(sun.sun_path, sizeof(sun.sun_path) - 1,
49*cb977d3aSmvs "undgram_selfconn%d.socket", getpid());
50*cb977d3aSmvs
51*cb977d3aSmvs unlink(sun.sun_path);
52*cb977d3aSmvs
53*cb977d3aSmvs if ((s = socket(AF_UNIX, SOCK_DGRAM|SOCK_NONBLOCK, 0)) < 0)
54*cb977d3aSmvs err(1, "socket");
55*cb977d3aSmvs if (bind(s, (struct sockaddr *)&sun, sizeof(sun)) < 0)
56*cb977d3aSmvs err(1, "bind");
57*cb977d3aSmvs
58*cb977d3aSmvs if (sendto(s, &s, sizeof(s), 0,
59*cb977d3aSmvs (struct sockaddr *)&sun, sizeof(sun)) < 0)
60*cb977d3aSmvs err(1, "sendto");
61*cb977d3aSmvs
62*cb977d3aSmvs /*
63*cb977d3aSmvs * Check received data to be sure the temporary connection
64*cb977d3aSmvs * was successful.
65*cb977d3aSmvs */
66*cb977d3aSmvs if ((ret = recvfrom(s, &buf, sizeof(buf), 0, NULL, NULL)) < 0)
67*cb977d3aSmvs err(1, "recvfrom");
68*cb977d3aSmvs if (ret != sizeof(s))
69*cb977d3aSmvs errx(1, "recvfrom: wrong size");
70*cb977d3aSmvs if (buf != s)
71*cb977d3aSmvs errx(1, "recvfrom: wrong data");
72*cb977d3aSmvs
73*cb977d3aSmvs if (connect(s, (struct sockaddr *)&sun, sizeof(sun)) < 0)
74*cb977d3aSmvs err(1, "connect");
75*cb977d3aSmvs /* Disconnect and connect it again */
76*cb977d3aSmvs if (connect(s, (struct sockaddr *)&sun, sizeof(sun)) < 0)
77*cb977d3aSmvs err(1, "connect");
78*cb977d3aSmvs close(s);
79*cb977d3aSmvs
80*cb977d3aSmvs return 0;
81*cb977d3aSmvs }
82