mkarp.c revision 1.8 
1/*	$NetBSD: mkarp.c,v 1.8 2009/04/18 08:50:23 lukem 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. Neither the name of the University nor the names of its contributors
19 *    may be used to endorse or promote products derived from this software
20 *    without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 */
34
35#include <sys/cdefs.h>
36#ifndef lint
37__COPYRIGHT("@(#) Copyright (c) 1984, 1993\
38 The Regents of the University of California.  All rights reserved.");
39#endif /* not lint */
40
41#ifndef lint
42#if 0
43static char sccsid[] = "@(#)arp.c	8.3 (Berkeley) 4/28/95";
44#else
45__RCSID("$NetBSD: mkarp.c,v 1.8 2009/04/18 08:50:23 lukem Exp $");
46#endif
47#endif /* not lint */
48
49/*
50 * mkarp - set an arp table entry
51 */
52
53#include <sys/param.h>
54#include <sys/file.h>
55#include <sys/socket.h>
56#include <sys/sysctl.h>
57
58#include <net/if.h>
59#include <net/if_dl.h>
60#include <net/if_ether.h>
61#include <net/if_types.h>
62#include <net/route.h>
63#include <netinet/in.h>
64#include <netinet/if_inarp.h>
65#include <arpa/inet.h>
66
67#include <err.h>
68#include <errno.h>
69#include <netdb.h>
70#include <nlist.h>
71#include <paths.h>
72#include <stdio.h>
73#include <stdlib.h>
74#include <string.h>
75#include <unistd.h>
76
77#include "mkarp.h"
78
79/* Roundup the same way rt_xaddrs does */
80#define ROUNDUP(a) \
81       ((a) > 0 ? (1 + (((a) - 1) | (sizeof(long) - 1))) : sizeof(long))
82
83int	rtmsg(int, int, struct rt_msghdr *, struct sockaddr_inarp *,
84	      struct sockaddr_dl *);
85struct	{
86	struct	rt_msghdr m_rtm;
87	char	m_space[512];
88}	m_rtmsg;
89
90/*
91 * Set an individual arp entry
92 */
93int
94mkarp(u_char *haddr, u_int32_t ipaddr)
95{
96	static struct sockaddr_inarp blank_sin = {
97		sizeof(blank_sin), AF_INET, 0, { 0 }, { 0 }, 0, 0  };
98	static struct sockaddr_dl blank_sdl = {
99		sizeof(blank_sdl), AF_LINK, 0, 0, 0, 0, 0, { 0 } };
100
101	struct sockaddr_inarp *sin;
102	struct sockaddr_dl *sdl;
103	struct rt_msghdr *rtm;
104	u_int8_t *p, *endp;
105	int result;
106	int s;
107
108	struct sockaddr_inarp sin_m;
109	struct sockaddr_dl sdl_m;
110
111	sin = &sin_m;
112	rtm = &(m_rtmsg.m_rtm);
113
114	sdl_m = blank_sdl;		/* struct copy */
115	sin_m = blank_sin;		/* struct copy */
116
117	sin->sin_addr.s_addr = ipaddr;
118
119	p = LLADDR(&sdl_m);
120	endp = ((caddr_t)&sdl_m) + sdl_m.sdl_len;
121	if (endp > (p + ETHER_ADDR_LEN))
122		endp = p + ETHER_ADDR_LEN;
123
124	while (p < endp) {
125		*p++ = *haddr++;
126	}
127	sdl_m.sdl_alen = ETHER_ADDR_LEN;
128
129	/*
130	 * We need to close and open the socket to prevent routing updates
131	 * building up such that when we send our message we never see our
132	 * reply (and hang)
133	 */
134	s = socket(PF_ROUTE, SOCK_RAW, 0);
135	if (s < 0)
136		err(1, "socket");
137
138	rtm->rtm_flags = 0;
139
140	if (rtmsg(RTM_GET, s, rtm, &sin_m, &sdl_m) < 0) {
141#if 0
142		warn("%s", host);
143#endif
144		close(s);
145		return (1);
146	}
147	sin = (struct sockaddr_inarp *)(rtm + 1);
148	sdl = (struct sockaddr_dl *)(sin->sin_len + (char *)sin);
149	if (sin->sin_addr.s_addr == sin_m.sin_addr.s_addr) {
150		if (sdl->sdl_family == AF_LINK &&
151		    (rtm->rtm_flags & RTF_LLINFO) &&
152		    !(rtm->rtm_flags & RTF_GATEWAY)) switch (sdl->sdl_type) {
153		case IFT_ETHER: case IFT_FDDI: case IFT_ISO88023:
154		case IFT_ISO88024: case IFT_ISO88025: case IFT_ARCNET:
155			goto overwrite;
156		}
157#if 0
158		(void)printf("set: can only proxy for %s\n", host);
159#endif
160		close(s);
161		return (1);
162	}
163overwrite:
164	if (sdl->sdl_family != AF_LINK) {
165#if 0
166		(void)printf("cannot intuit interface index and type for %s\n",
167		    host);
168#endif
169		close(s);
170		return (1);
171	}
172	sdl_m.sdl_type = sdl->sdl_type;
173	sdl_m.sdl_index = sdl->sdl_index;
174	result = rtmsg(RTM_ADD, s, rtm, &sin_m, &sdl_m);
175	close(s);
176	return (result);
177}
178
179int
180rtmsg(int cmd, int s, struct rt_msghdr *rtm, struct sockaddr_inarp *sin_m,
181      struct sockaddr_dl *sdl_m)
182{
183	static int seq;
184	int rlen;
185	char *cp;
186	int l;
187	pid_t pid;
188	struct timeval tv;
189
190	rtm = &m_rtmsg.m_rtm;
191	cp = m_rtmsg.m_space;
192	errno = 0;
193
194	pid = getpid();
195
196	(void)memset(&m_rtmsg, 0, sizeof(m_rtmsg));
197	rtm->rtm_version = RTM_VERSION;
198
199	switch (cmd) {
200	default:
201		errx(1, "internal wrong cmd");
202		/*NOTREACHED*/
203	case RTM_ADD:
204		rtm->rtm_addrs |= RTA_GATEWAY;
205		(void)gettimeofday(&tv, 0);
206		rtm->rtm_rmx.rmx_expire = tv.tv_sec + 20 * 60;
207		rtm->rtm_inits = RTV_EXPIRE;
208		rtm->rtm_flags |= (RTF_HOST | RTF_STATIC);
209		sin_m->sin_other = 0;
210
211		/* FALLTHROUGH */
212	case RTM_GET:
213		rtm->rtm_addrs |= RTA_DST;
214	}
215#define NEXTADDR(w, s) \
216	if (rtm->rtm_addrs & (w)) { \
217		(void)memcpy(cp, s, ((struct sockaddr *)s)->sa_len); \
218                cp += ROUNDUP(((struct sockaddr *)s)->sa_len);}
219
220	NEXTADDR(RTA_DST, sin_m);
221	NEXTADDR(RTA_GATEWAY, sdl_m);
222
223	rtm->rtm_msglen = cp - (char *)&m_rtmsg;
224
225	l = rtm->rtm_msglen;
226	rtm->rtm_seq = ++seq;
227	rtm->rtm_type = cmd;
228	if ((rlen = write(s, (char *)&m_rtmsg, l)) < 0) {
229		if (errno != ESRCH && errno != EEXIST) {
230			warn("writing to routing socket");
231			return (-1);
232		}
233	}
234	do {
235		l = read(s, (char *)&m_rtmsg, sizeof(m_rtmsg));
236	} while (l > 0 && (rtm->rtm_seq != seq || rtm->rtm_pid != pid));
237	if (l < 0)
238		warn("read from routing socket");
239	return (0);
240}
241