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