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
main(int argc,char * argv[])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
usage(void)86 usage(void)
87 {
88 fprintf(stderr, "usage: srcaddr destination\n");
89 exit (1);
90 }
91