1 /*	$OpenBSD: nonxt-reflect.c,v 1.2 2018/05/21 01:19:21 bluhm Exp $	*/
2 /*
3  * Copyright (c) Alexander Bluhm <bluhm@genua.de>
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/types.h>
19 #include <sys/socket.h>
20 
21 #include <netdb.h>
22 
23 #include <err.h>
24 #include <errno.h>
25 #include <stdio.h>
26 #include <stdlib.h>
27 #include <string.h>
28 #include <unistd.h>
29 
30 void __dead usage(void);
31 
32 void
33 usage(void)
34 {
35 	fprintf(stderr, "usage: nonxt-reflect localaddr\n"
36 	    "Daemonize, wait for protocol 59 packets, and answer them.\n");
37 	exit(1);
38 }
39 
40 int
41 main(int argc, char *argv[])
42 {
43 	struct addrinfo hints, *res, *res0;
44 	const char *cause = NULL, *local;
45 	int error;
46 	int save_errno;
47 	int s;
48 	char buf[1024];
49 
50 	switch (argc) {
51 	case 2:
52 		local = argv[1];
53 		break;
54 	default:
55 		usage();
56 	}
57 
58 	if (pledge("stdio inet dns proc", NULL) == -1)
59 		err(1, "pledge");
60 
61 	/* Create socket and bind it to local address. */
62 	memset(&hints, 0, sizeof(hints));
63 	hints.ai_family = AF_UNSPEC;
64 	hints.ai_socktype = SOCK_RAW;
65 	hints.ai_protocol = IPPROTO_NONE;
66 	hints.ai_flags = AI_PASSIVE;
67 	error = getaddrinfo(local, NULL, &hints, &res0);
68 	if (error)
69 		errx(1, "getaddrinfo local: %s", gai_strerror(error));
70 	for (res = res0; res; res = res->ai_next) {
71 		s = socket(res->ai_family, res->ai_socktype, res->ai_protocol);
72 		if (s == -1) {
73 			cause = "socket";
74 			continue;
75 		}
76 		if (bind(s, res->ai_addr, res->ai_addrlen) == -1) {
77 			cause = "bind";
78 			save_errno = errno;
79 			close(s);
80 			errno = save_errno;
81 			continue;
82 		}
83 		break;
84 	}
85 	if (res == NULL)
86 		err(1, "%s", cause);
87 	freeaddrinfo(res0);
88 
89 	/* Socket is ready to receive, parent process may proceed. */
90 	daemon(1, 1);
91 	if (pledge("stdio inet", NULL) == -1)
92 		err(1, "pledge");
93 
94 	for (;;) {
95 		struct sockaddr_storage ss;
96 		socklen_t slen;
97 
98 		/* Receive a protocol 59 packet. */
99 		slen = sizeof(ss);
100 		if (recvfrom(s, buf, sizeof(buf), 0, (struct sockaddr *)&ss,
101 		    &slen) == -1)
102 			err(1, "recv");
103 		/* Send back a reply packet. */
104 		if (sendto(s, buf, 0, 0, (struct sockaddr *)&ss, slen) == -1)
105 			err(1, "send");
106 	}
107 
108 	/* NOTREACHED */
109 	return 0;
110 }
111