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#include <sys/param.h>
37#include <sys/file.h>
38#include <sys/ioctl.h>
39#include <sys/socket.h>
40#include <sys/sockio.h>
41#include <sys/time.h>				/* concession to AIX */
42
43#if __STDC__
44struct mbuf;
45struct rtentry;
46#endif
47
48#include <net/if.h>
49#include <net/if_dl.h>
50#include <net/route.h>
51#include <netinet/in.h>
52
53#include <errno.h>
54#include <stdio.h>
55#include <stdlib.h>
56#include <string.h>
57#include <unistd.h>
58
59#include "gnuc.h"
60#include "os-proto.h"
61
62#include "findsaddr.h"
63
64#define SALEN(sa) ((sa)->sa_len)
65
66#ifndef roundup
67#define roundup(x, y)   ((((x)+((y)-1))/(y))*(y))  /* to any y */
68#endif
69
70struct rtmsg {
71        struct rt_msghdr rtmsg;
72        u_char data[512];
73};
74
75static struct rtmsg rtmsg = {
76	{ 0, RTM_VERSION, RTM_GET, 0,
77	RTF_UP | RTF_GATEWAY | RTF_HOST | RTF_STATIC,
78	RTA_DST | RTA_IFA, 0, 0, 0, 0, 0, { 0 } },
79	{ 0 }
80};
81
82/*
83 * Return the source address for the given destination address
84 */
85const char *
86findsaddr(register const struct sockaddr_in *to,
87    register struct sockaddr_in *from)
88{
89	register struct rt_msghdr *rp;
90	register u_char *cp;
91
92	register struct sockaddr_in *sp, *ifa;
93	register struct sockaddr *sa;
94	register int s, size, cc, seq, i;
95	register pid_t pid;
96	static char errbuf[512];
97
98	s = socket(PF_ROUTE, SOCK_RAW, AF_UNSPEC);
99	if (s < 0) {
100		sprintf(errbuf, "socket: %.128s", strerror(errno));
101		return (errbuf);
102	}
103
104	seq = 0;
105	pid = getpid();
106
107	rp = &rtmsg.rtmsg;
108	rp->rtm_seq = ++seq;
109	cp = (u_char *)(rp + 1);
110
111	sp = (struct sockaddr_in *)cp;
112	*sp = *to;
113	cp += roundup(SALEN((struct sockaddr *)sp), sizeof(u_int32_t));
114
115	size = cp - (u_char *)rp;
116	rp->rtm_msglen = size;
117
118	cc = write(s, (char *)rp, size);
119	if (cc < 0) {
120		sprintf(errbuf, "write: %.128s", strerror(errno));
121		close(s);
122		return (errbuf);
123	}
124	if (cc != size) {
125		sprintf(errbuf, "short write (%d != %d)", cc, size);
126		close(s);
127		return (errbuf);
128	}
129
130	size = sizeof(rtmsg);
131	do {
132		memset(rp, 0, size);
133		cc = read(s, (char *)rp, size);
134		if (cc < 0) {
135			sprintf(errbuf, "read: %.128s", strerror(errno));
136			close(s);
137			return (errbuf);
138		}
139
140	} while (rp->rtm_type != RTM_GET || rp->rtm_seq != seq ||
141	    rp->rtm_pid != pid);
142	close(s);
143
144
145	if (rp->rtm_version != RTM_VERSION) {
146		sprintf(errbuf, "bad version %d", rp->rtm_version);
147		return (errbuf);
148	}
149	if (rp->rtm_msglen > cc) {
150		sprintf(errbuf, "bad msglen %d > %d", rp->rtm_msglen, cc);
151		return (errbuf);
152	}
153	if (rp->rtm_errno != 0) {
154		sprintf(errbuf, "rtm_errno: %.128s", strerror(rp->rtm_errno));
155		return (errbuf);
156	}
157
158	/* Find the interface sockaddr */
159	cp = (u_char *)(rp + 1);
160	for (i = 1; i != 0; i <<= 1)
161		if ((i & rp->rtm_addrs) != 0) {
162			sa = (struct sockaddr *)cp;
163			switch (i) {
164
165			case RTA_IFA:
166				if (sa->sa_family == AF_INET) {
167					ifa = (struct sockaddr_in *)cp;
168					if (ifa->sin_addr.s_addr != 0) {
169						*from = *ifa;
170						return (NULL);
171					}
172				}
173				break;
174
175			}
176
177			if (SALEN(sa) == 0)
178				cp += sizeof(long);
179			else
180				cp += roundup(SALEN(sa), sizeof(long));
181		}
182
183	return ("failed!");
184}
185