findsaddr-socket.c revision 100784 
1/*
2 * Copyright (c) 2000
3 *	The Regents of the University of California.  All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 * 3. All advertising materials mentioning features or use of this software
14 *    must display the following acknowledgement:
15 *	This product includes software developed by the Computer Systems
16 *	Engineering Group at Lawrence Berkeley Laboratory.
17 * 4. Neither the name of the University nor of the Laboratory may be used
18 *    to endorse or promote products derived from this software without
19 *    specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 */
33
34/* XXX Yes this is WAY too complicated */
35
36#ifndef lint
37static const char rcsid[] =
38    "@(#) $Id: findsaddr-socket.c,v 1.1 2000/11/23 20:17:12 leres Exp $ (LBL)";
39#endif
40
41#include <sys/param.h>
42#include <sys/file.h>
43#include <sys/ioctl.h>
44#include <sys/socket.h>
45#ifdef HAVE_SYS_SOCKIO_H
46#include <sys/sockio.h>
47#endif
48#include <sys/time.h>				/* concession to AIX */
49
50#if __STDC__
51struct mbuf;
52struct rtentry;
53#endif
54
55#include <net/if.h>
56#include <net/if_dl.h>
57#include <net/route.h>
58#include <netinet/in.h>
59
60#include <errno.h>
61#include <stdio.h>
62#include <stdlib.h>
63#include <string.h>
64#include <unistd.h>
65
66#include "gnuc.h"
67#ifdef HAVE_OS_PROTO_H
68#include "os-proto.h"
69#endif
70
71#include "findsaddr.h"
72
73#ifdef HAVE_SOCKADDR_SA_LEN
74#define SALEN(sa) ((sa)->sa_len)
75#else
76#define SALEN(sa) salen(sa)
77#endif
78
79#ifndef roundup
80#define roundup(x, y)   ((((x)+((y)-1))/(y))*(y))  /* to any y */
81#endif
82
83struct rtmsg {
84        struct rt_msghdr rtmsg;
85        u_char data[512];
86};
87
88static struct rtmsg rtmsg = {
89	{ 0, RTM_VERSION, RTM_GET, 0,
90	RTF_UP | RTF_GATEWAY | RTF_HOST | RTF_STATIC,
91	RTA_DST | RTA_IFA, 0, 0, 0, 0, 0, { 0 } },
92	{ 0 }
93};
94
95#ifndef HAVE_SOCKADDR_SA_LEN
96static int salen(struct sockaddr *);
97#endif
98
99/*
100 * Return the source address for the given destination address
101 */
102const char *
103findsaddr(register const struct sockaddr_in *to,
104    register struct sockaddr_in *from)
105{
106	register struct rt_msghdr *rp;
107	register u_char *cp;
108
109	register struct sockaddr_in *sp, *ifa;
110	register struct sockaddr *sa;
111	register int s, size, cc, seq, i;
112	register pid_t pid;
113	static char errbuf[512];
114
115	s = socket(PF_ROUTE, SOCK_RAW, AF_UNSPEC);
116	if (s < 0) {
117		sprintf(errbuf, "socket: %.128s", strerror(errno));
118		return (errbuf);
119	}
120
121	seq = 0;
122	pid = getpid();
123
124	rp = &rtmsg.rtmsg;
125	rp->rtm_seq = ++seq;
126	cp = (u_char *)(rp + 1);
127
128	sp = (struct sockaddr_in *)cp;
129	*sp = *to;
130	cp += roundup(SALEN((struct sockaddr *)sp), sizeof(u_int32_t));
131
132	size = cp - (u_char *)rp;
133	rp->rtm_msglen = size;
134
135	cc = write(s, (char *)rp, size);
136	if (cc < 0) {
137		sprintf(errbuf, "write: %.128s", strerror(errno));
138		close(s);
139		return (errbuf);
140	}
141	if (cc != size) {
142		sprintf(errbuf, "short write (%d != %d)", cc, size);
143		close(s);
144		return (errbuf);
145	}
146
147	size = sizeof(rtmsg);
148	do {
149		memset(rp, 0, size);
150		cc = read(s, (char *)rp, size);
151		if (cc < 0) {
152			sprintf(errbuf, "read: %.128s", strerror(errno));
153			close(s);
154			return (errbuf);
155		}
156
157	} while (rp->rtm_seq != seq || rp->rtm_pid != pid);
158	close(s);
159
160
161	if (rp->rtm_version != RTM_VERSION) {
162		sprintf(errbuf, "bad version %d", rp->rtm_version);
163		return (errbuf);
164	}
165	if (rp->rtm_msglen > cc) {
166		sprintf(errbuf, "bad msglen %d > %d", rp->rtm_msglen, cc);
167		return (errbuf);
168	}
169	if (rp->rtm_errno != 0) {
170		sprintf(errbuf, "rtm_errno: %.128s", strerror(rp->rtm_errno));
171		return (errbuf);
172	}
173
174	/* Find the interface sockaddr */
175	cp = (u_char *)(rp + 1);
176	for (i = 1; i != 0; i <<= 1)
177		if ((i & rp->rtm_addrs) != 0) {
178			sa = (struct sockaddr *)cp;
179			switch (i) {
180
181			case RTA_IFA:
182				if (sa->sa_family == AF_INET) {
183					ifa = (struct sockaddr_in *)cp;
184					if (ifa->sin_addr.s_addr != 0) {
185						*from = *ifa;
186						return (NULL);
187					}
188				}
189				break;
190
191			default:
192				/* empty */
193			}
194
195			if (SALEN(sa) == 0)
196				cp += sizeof(u_int32_t);
197			else
198				cp += roundup(SALEN(sa), sizeof(u_int32_t));
199		}
200
201	return ("failed!");
202}
203
204#ifndef HAVE_SOCKADDR_SA_LEN
205static int
206salen(struct sockaddr *sa)
207{
208	switch (sa->sa_family) {
209
210	case AF_INET:
211		return (sizeof(struct sockaddr_in));
212
213	case AF_LINK:
214		return (sizeof(struct sockaddr_dl));
215
216	default:
217		return (sizeof(struct sockaddr));
218	}
219}
220#endif
221