mkarp.c revision 1.11 
1/*	$NetBSD: mkarp.c,v 1.11 2016/04/04 07:37:08 ozaki-r 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 1.11 2016/04/04 07:37:08 ozaki-r 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 *);
85static struct {
86	struct	rt_msghdr m_rtm;
87	char	m_space[512];
88}	m_rtmsg;
89
90static int
91is_llinfo(const struct sockaddr_dl *sdl, int rtflags)
92{
93	if (sdl->sdl_family != AF_LINK ||
94	    (rtflags & (RTF_LLDATA|RTF_GATEWAY)) != RTF_LLDATA)
95		return 0;
96
97	switch (sdl->sdl_type) {
98	case IFT_ETHER:
99	case IFT_FDDI:
100	case IFT_ISO88023:
101	case IFT_ISO88024:
102	case IFT_ISO88025:
103	case IFT_ARCNET:
104		return 1;
105	default:
106		return 0;
107	}
108}
109
110/*
111 * Set an individual arp entry
112 */
113int
114mkarp(u_char *haddr, u_int32_t ipaddr)
115{
116	static struct sockaddr_inarp blank_sin = {
117		.sin_len = sizeof(blank_sin),
118		.sin_family = AF_INET,
119	};
120	static struct sockaddr_dl blank_sdl = {
121		.sdl_len = sizeof(blank_sdl),
122		.sdl_family = AF_LINK,
123	};
124
125	struct sockaddr_inarp *sin;
126	struct sockaddr_dl *sdl;
127	struct rt_msghdr *rtm;
128	u_int8_t *p, *endp;
129	int result;
130	int s;
131
132	struct sockaddr_inarp sin_m;
133	struct sockaddr_dl sdl_m;
134
135	sin = &sin_m;
136	rtm = &(m_rtmsg.m_rtm);
137
138	sdl_m = blank_sdl;		/* struct copy */
139	sin_m = blank_sin;		/* struct copy */
140
141	sin->sin_addr.s_addr = ipaddr;
142
143	p = LLADDR(&sdl_m);
144	endp = ((caddr_t)&sdl_m) + sdl_m.sdl_len;
145	if (endp > (p + ETHER_ADDR_LEN))
146		endp = p + ETHER_ADDR_LEN;
147
148	while (p < endp) {
149		*p++ = *haddr++;
150	}
151	sdl_m.sdl_alen = ETHER_ADDR_LEN;
152
153	/*
154	 * We need to close and open the socket to prevent routing updates
155	 * building up such that when we send our message we never see our
156	 * reply (and hang)
157	 */
158	s = socket(PF_ROUTE, SOCK_RAW, 0);
159	if (s < 0)
160		err(1, "socket");
161
162	rtm->rtm_flags = 0;
163
164	if (rtmsg(RTM_GET, s, rtm, &sin_m, &sdl_m) < 0) {
165#if 0
166		warn("%s", host);
167#endif
168		close(s);
169		return (1);
170	}
171	sin = (struct sockaddr_inarp *)(rtm + 1);
172	sdl = (struct sockaddr_dl *)(sin->sin_len + (char *)sin);
173	if (sin->sin_addr.s_addr == sin_m.sin_addr.s_addr) {
174		if (is_llinfo(sdl, rtm->rtm_flags))
175			goto overwrite;
176#if 0
177		(void)printf("set: can only proxy for %s\n", host);
178#endif
179		close(s);
180		return (1);
181	}
182overwrite:
183	if (sdl->sdl_family != AF_LINK) {
184#if 0
185		(void)printf("cannot intuit interface index and type for %s\n",
186		    host);
187#endif
188		close(s);
189		return (1);
190	}
191	sdl_m.sdl_type = sdl->sdl_type;
192	sdl_m.sdl_index = sdl->sdl_index;
193	result = rtmsg(RTM_ADD, s, rtm, &sin_m, &sdl_m);
194	close(s);
195	return (result);
196}
197
198int
199rtmsg(int cmd, int s, struct rt_msghdr *rtm, struct sockaddr_inarp *sin_m,
200      struct sockaddr_dl *sdl_m)
201{
202	static int seq;
203	int rlen;
204	char *cp;
205	int l;
206	pid_t pid;
207	struct timeval tv;
208
209	rtm = &m_rtmsg.m_rtm;
210	cp = m_rtmsg.m_space;
211	errno = 0;
212
213	pid = getpid();
214
215	(void)memset(&m_rtmsg, 0, sizeof(m_rtmsg));
216	rtm->rtm_version = RTM_VERSION;
217
218	switch (cmd) {
219	default:
220		errx(1, "internal wrong cmd");
221		/*NOTREACHED*/
222	case RTM_ADD:
223		rtm->rtm_addrs |= RTA_GATEWAY;
224		(void)gettimeofday(&tv, 0);
225		rtm->rtm_rmx.rmx_expire = tv.tv_sec + 20 * 60;
226		rtm->rtm_inits = RTV_EXPIRE;
227		rtm->rtm_flags |= (RTF_HOST | RTF_STATIC | RTF_LLDATA);
228		sin_m->sin_other = 0;
229
230		/* FALLTHROUGH */
231	case RTM_GET:
232		rtm->rtm_addrs |= RTA_DST;
233	}
234#define NEXTADDR(w, s) \
235	if (rtm->rtm_addrs & (w)) { \
236		(void)memcpy(cp, s, ((struct sockaddr *)s)->sa_len); \
237                cp += ROUNDUP(((struct sockaddr *)s)->sa_len);}
238
239	NEXTADDR(RTA_DST, sin_m);
240	NEXTADDR(RTA_GATEWAY, sdl_m);
241
242	rtm->rtm_msglen = cp - (char *)&m_rtmsg;
243
244	l = rtm->rtm_msglen;
245	rtm->rtm_seq = ++seq;
246	rtm->rtm_type = cmd;
247	if ((rlen = write(s, (char *)&m_rtmsg, l)) < 0) {
248		if (errno != ESRCH && errno != EEXIST) {
249			warn("writing to routing socket");
250			return (-1);
251		}
252	}
253	do {
254		l = read(s, (char *)&m_rtmsg, sizeof(m_rtmsg));
255	} while (l > 0 && (rtm->rtm_seq != seq || rtm->rtm_pid != pid));
256	if (l < 0)
257		warn("read from routing socket");
258	return (0);
259}
260