1 /* $OpenBSD: srcaddr.c,v 1.1 2020/04/13 03:09:29 pamela Exp $ */ 2 3 /* 4 * Copyright (c) 2020 Pamela Mosiejczuk <pamela@openbsd.org> 5 * Copyright (c) 2020 Florian Obser <florian@openbsd.org> 6 * 7 * Permission to use, copy, modify, and distribute this software for any 8 * purpose with or without fee is hereby granted, provided that the above 9 * copyright notice and this permission notice appear in all copies. 10 * 11 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 12 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 13 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 14 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 15 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 16 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 17 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 18 */ 19 20 #include <sys/types.h> 21 #include <sys/socket.h> 22 23 #include <err.h> 24 #include <netdb.h> 25 #include <stdio.h> 26 #include <stdlib.h> 27 #include <string.h> 28 #include <unistd.h> 29 30 __dead void usage(void); 31 32 /* given an IPv6 destination address, return the source address selected */ 33 int 34 main(int argc, char *argv[]) 35 { 36 struct addrinfo hints, *res; 37 struct sockaddr_storage ss; 38 socklen_t len; 39 int ch, error, s; 40 char *target, src[NI_MAXHOST]; 41 42 while ((ch = getopt(argc, argv, "")) != -1) { 43 switch (ch) { 44 default: 45 usage(); 46 } 47 } 48 argc -= optind; 49 argv += optind; 50 51 if (argc != 1) 52 usage(); 53 54 target = *argv; 55 56 memset(&hints, 0, sizeof(hints)); 57 hints.ai_flags = AI_NUMERICHOST | AI_NUMERICSERV; 58 hints.ai_family = AF_INET6; 59 hints.ai_socktype = SOCK_DGRAM; 60 61 if ((error = getaddrinfo(target, "8888", &hints, &res))) 62 errx(1, "%s", gai_strerror(error)); 63 64 s = socket(res->ai_family, res->ai_socktype, res->ai_protocol); 65 if (s == -1) 66 err(1, "socket"); 67 68 if (connect(s, res->ai_addr, res->ai_addrlen) == -1) 69 err(1, "connect"); 70 freeaddrinfo(res); 71 72 len = sizeof(ss); 73 if (getsockname(s, (struct sockaddr *)&ss, &len) == -1) 74 err(1, "getsockname"); 75 76 if ((error = getnameinfo((struct sockaddr *)&ss, ss.ss_len, src, 77 sizeof(src), NULL, 0, NI_NUMERICHOST | NI_NUMERICSERV))) 78 errx(1, "%s", gai_strerror(error)); 79 80 printf("%s\n", src); 81 82 return (0); 83 } 84 85 __dead void 86 usage(void) 87 { 88 fprintf(stderr, "usage: srcaddr destination\n"); 89 exit (1); 90 } 91