mkarp.c revision 1.5 
1/*	$NetBSD: mkarp.c,v 1.5 2003/04/08 04:04:01 petrov Exp $ */
2
3/*
4 * Copyright (c) 1984, 1993
5 *	The Regents of the University of California.  All rights reserved.
6 *
7 * This code is derived from software contributed to Berkeley by
8 * Sun Microsystems, Inc.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 *    notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 * 3. All advertising materials mentioning features or use of this software
19 *    must display the following acknowledgement:
20 *	This product includes software developed by the University of
21 *	California, Berkeley and its contributors.
22 * 4. Neither the name of the University nor the names of its contributors
23 *    may be used to endorse or promote products derived from this software
24 *    without specific prior written permission.
25 *
26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
29 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36 * SUCH DAMAGE.
37 */
38
39#include <sys/cdefs.h>
40#ifndef lint
41__COPYRIGHT("@(#) Copyright (c) 1984, 1993\n\
42	The Regents of the University of California.  All rights reserved.\n");
43#endif /* not lint */
44
45#ifndef lint
46#if 0
47static char sccsid[] = "@(#)arp.c	8.3 (Berkeley) 4/28/95";
48#else
49__RCSID("$NetBSD: mkarp.c,v 1.5 2003/04/08 04:04:01 petrov Exp $");
50#endif
51#endif /* not lint */
52
53/*
54 * mkarp - set an arp table entry
55 */
56
57#include <sys/param.h>
58#include <sys/file.h>
59#include <sys/socket.h>
60#include <sys/sysctl.h>
61
62#include <net/if.h>
63#include <net/if_dl.h>
64#include <net/if_ether.h>
65#include <net/if_types.h>
66#include <net/route.h>
67#include <netinet/in.h>
68#include <netinet/if_inarp.h>
69#include <arpa/inet.h>
70
71#include <err.h>
72#include <errno.h>
73#include <netdb.h>
74#include <nlist.h>
75#include <paths.h>
76#include <stdio.h>
77#include <stdlib.h>
78#include <string.h>
79#include <unistd.h>
80
81#include "mkarp.h"
82
83/* Roundup the same way rt_xaddrs does */
84#define ROUNDUP(a) \
85       ((a) > 0 ? (1 + (((a) - 1) | (sizeof(long) - 1))) : sizeof(long))
86
87int	rtmsg(int, int, struct rt_msghdr *, struct sockaddr_inarp *,
88	      struct sockaddr_dl *);
89struct	{
90	struct	rt_msghdr m_rtm;
91	char	m_space[512];
92}	m_rtmsg;
93
94/*
95 * Set an individual arp entry
96 */
97int
98mkarp(u_char *haddr, u_int32_t ipaddr)
99{
100	static struct sockaddr_inarp blank_sin = {sizeof(blank_sin), AF_INET };
101	static struct sockaddr_dl blank_sdl = {sizeof(blank_sdl), AF_LINK };
102
103	struct sockaddr_inarp *sin;
104	struct sockaddr_dl *sdl;
105	struct rt_msghdr *rtm;
106	u_int8_t *p, *endp;
107	int result;
108	int s;
109
110	struct sockaddr_inarp sin_m;
111	struct sockaddr_dl sdl_m;
112
113	sin = &sin_m;
114	rtm = &(m_rtmsg.m_rtm);
115
116	sdl_m = blank_sdl;		/* struct copy */
117	sin_m = blank_sin;		/* struct copy */
118
119	sin->sin_addr.s_addr = ipaddr;
120
121	p = LLADDR(&sdl_m);
122	endp = ((caddr_t)&sdl_m) + sdl_m.sdl_len;
123	if (endp > (p + ETHER_ADDR_LEN))
124		endp = p + ETHER_ADDR_LEN;
125
126	while (p < endp) {
127		*p++ = *haddr++;
128	}
129	sdl_m.sdl_alen = ETHER_ADDR_LEN;
130
131	/*
132	 * We need to close and open the socket to prevent routing updates
133	 * building up such that when we send our message we never see our
134	 * reply (and hang)
135	 */
136	s = socket(PF_ROUTE, SOCK_RAW, 0);
137	if (s < 0)
138		err(1, "socket");
139
140	rtm->rtm_flags = 0;
141
142	if (rtmsg(RTM_GET, s, rtm, &sin_m, &sdl_m) < 0) {
143#if 0
144		warn("%s", host);
145#endif
146		close(s);
147		return (1);
148	}
149	sin = (struct sockaddr_inarp *)(rtm + 1);
150	sdl = (struct sockaddr_dl *)(sin->sin_len + (char *)sin);
151	if (sin->sin_addr.s_addr == sin_m.sin_addr.s_addr) {
152		if (sdl->sdl_family == AF_LINK &&
153		    (rtm->rtm_flags & RTF_LLINFO) &&
154		    !(rtm->rtm_flags & RTF_GATEWAY)) switch (sdl->sdl_type) {
155		case IFT_ETHER: case IFT_FDDI: case IFT_ISO88023:
156		case IFT_ISO88024: case IFT_ISO88025: case IFT_ARCNET:
157			goto overwrite;
158		}
159#if 0
160		(void)printf("set: can only proxy for %s\n", host);
161#endif
162		close(s);
163		return (1);
164	}
165overwrite:
166	if (sdl->sdl_family != AF_LINK) {
167#if 0
168		(void)printf("cannot intuit interface index and type for %s\n",
169		    host);
170#endif
171		close(s);
172		return (1);
173	}
174	sdl_m.sdl_type = sdl->sdl_type;
175	sdl_m.sdl_index = sdl->sdl_index;
176	result = rtmsg(RTM_ADD, s, rtm, &sin_m, &sdl_m);
177	close(s);
178	return (result);
179}
180
181int
182rtmsg(int cmd, int s, struct rt_msghdr *rtm, struct sockaddr_inarp *sin_m,
183      struct sockaddr_dl *sdl_m)
184{
185	static int seq;
186	int rlen;
187	char *cp;
188	int l;
189	pid_t pid;
190	struct timeval time;
191
192	rtm = &m_rtmsg.m_rtm;
193	cp = m_rtmsg.m_space;
194	errno = 0;
195
196	pid = getpid();
197
198	(void)memset(&m_rtmsg, 0, sizeof(m_rtmsg));
199	rtm->rtm_version = RTM_VERSION;
200
201	switch (cmd) {
202	default:
203		errx(1, "internal wrong cmd");
204		/*NOTREACHED*/
205	case RTM_ADD:
206		rtm->rtm_addrs |= RTA_GATEWAY;
207		(void)gettimeofday(&time, 0);
208		rtm->rtm_rmx.rmx_expire = time.tv_sec + 20 * 60;
209		rtm->rtm_inits = RTV_EXPIRE;
210		rtm->rtm_flags |= (RTF_HOST | RTF_STATIC);
211		sin_m->sin_other = 0;
212
213		/* FALLTHROUGH */
214	case RTM_GET:
215		rtm->rtm_addrs |= RTA_DST;
216	}
217#define NEXTADDR(w, s) \
218	if (rtm->rtm_addrs & (w)) { \
219		(void)memcpy(cp, s, ((struct sockaddr *)s)->sa_len); \
220                cp += ROUNDUP(((struct sockaddr *)s)->sa_len);}
221
222	NEXTADDR(RTA_DST, sin_m);
223	NEXTADDR(RTA_GATEWAY, sdl_m);
224
225	rtm->rtm_msglen = cp - (char *)&m_rtmsg;
226
227	l = rtm->rtm_msglen;
228	rtm->rtm_seq = ++seq;
229	rtm->rtm_type = cmd;
230	if ((rlen = write(s, (char *)&m_rtmsg, l)) < 0) {
231		if (errno != ESRCH && errno != EEXIST) {
232			warn("writing to routing socket");
233			return (-1);
234		}
235	}
236	do {
237		l = read(s, (char *)&m_rtmsg, sizeof(m_rtmsg));
238	} while (l > 0 && (rtm->rtm_seq != seq || rtm->rtm_pid != pid));
239	if (l < 0)
240		warn("read from routing socket");
241	return (0);
242}
243