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1/* $NetBSD: arp.c,v 1.18 1997/07/07 15:52:49 drochner Exp $ */
2
3/*
4 * Copyright (c) 1992 Regents of the University of California.
5 * All rights reserved.
6 *
7 * This software was developed by the Computer Systems Engineering group
8 * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
9 * contributed to Berkeley.
10 *
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions
13 * are met:
14 * 1. Redistributions of source code must retain the above copyright
15 * notice, this list of conditions and the following disclaimer.
16 * 2. Redistributions in binary form must reproduce the above copyright
17 * notice, this list of conditions and the following disclaimer in the
18 * documentation and/or other materials provided with the distribution.
19 * 3. All advertising materials mentioning features or use of this software
20 * must display the following acknowledgement:
21 * This product includes software developed by the University of
22 * California, Lawrence Berkeley Laboratory and its contributors.
19 * 4. Neither the name of the University nor the names of its contributors
20 * may be used to endorse or promote products derived from this software
21 * without specific prior written permission.
22 *
23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33 * SUCH DAMAGE.
34 *
35 * @(#) Header: arp.c,v 1.5 93/07/15 05:52:26 leres Exp (LBL)
36 */
37
38#include <sys/cdefs.h>
43__FBSDID("$FreeBSD: head/lib/libstand/arp.c 92913 2002-03-21 23:39:28Z obrien $");
39__FBSDID("$FreeBSD: head/lib/libstand/arp.c 165906 2007-01-09 01:02:06Z imp $");
40
41#include <sys/types.h>
42#include <sys/socket.h>
43#include <net/if.h>
44#include <netinet/in.h>
45#include <netinet/if_ether.h>
46
47#include <netinet/in_systm.h>
48
49#include <string.h>
50
51#include "stand.h"
52#include "net.h"
53
54/* Cache stuff */
55#define ARP_NUM 8 /* need at most 3 arp entries */
56
57struct arp_list {
58 struct in_addr addr;
59 u_char ea[6];
60} arp_list[ARP_NUM] = {
61 /* XXX - net order `INADDR_BROADCAST' must be a constant */
62 { {0xffffffff}, BA }
63};
64int arp_num = 1;
65
66/* Local forwards */
67static ssize_t arpsend(struct iodesc *, void *, size_t);
68static ssize_t arprecv(struct iodesc *, void *, size_t, time_t);
69
70/* Broadcast an ARP packet, asking who has addr on interface d */
71u_char *
72arpwhohas(d, addr)
73 struct iodesc *d;
74 struct in_addr addr;
75{
76 int i;
77 struct ether_arp *ah;
78 struct arp_list *al;
79 struct {
80 struct ether_header eh;
81 struct {
82 struct ether_arp arp;
83 u_char pad[18]; /* 60 - sizeof(...) */
84 } data;
85 } wbuf;
86 struct {
87 struct ether_header eh;
88 struct {
89 struct ether_arp arp;
90 u_char pad[24]; /* extra space */
91 } data;
92 } rbuf;
93
94 /* Try for cached answer first */
95 for (i = 0, al = arp_list; i < arp_num; ++i, ++al)
96 if (addr.s_addr == al->addr.s_addr)
97 return (al->ea);
98
99 /* Don't overflow cache */
100 if (arp_num > ARP_NUM - 1) {
101 arp_num = 1; /* recycle */
102 printf("arpwhohas: overflowed arp_list!\n");
103 }
104
105#ifdef ARP_DEBUG
106 if (debug)
107 printf("arpwhohas: send request for %s\n", inet_ntoa(addr));
108#endif
109
110 bzero((char*)&wbuf.data, sizeof(wbuf.data));
111 ah = &wbuf.data.arp;
112 ah->arp_hrd = htons(ARPHRD_ETHER);
113 ah->arp_pro = htons(ETHERTYPE_IP);
114 ah->arp_hln = sizeof(ah->arp_sha); /* hardware address length */
115 ah->arp_pln = sizeof(ah->arp_spa); /* protocol address length */
116 ah->arp_op = htons(ARPOP_REQUEST);
117 MACPY(d->myea, ah->arp_sha);
118 bcopy(&d->myip, ah->arp_spa, sizeof(ah->arp_spa));
119 /* Leave zeros in arp_tha */
120 bcopy(&addr, ah->arp_tpa, sizeof(ah->arp_tpa));
121
122 /* Store ip address in cache (incomplete entry). */
123 al->addr = addr;
124
125 i = sendrecv(d,
126 arpsend, &wbuf.data, sizeof(wbuf.data),
127 arprecv, &rbuf.data, sizeof(rbuf.data));
128 if (i == -1) {
129 panic("arp: no response for %s\n",
130 inet_ntoa(addr));
131 }
132
133 /* Store ethernet address in cache */
134 ah = &rbuf.data.arp;
135#ifdef ARP_DEBUG
136 if (debug) {
137 printf("arp: response from %s\n",
138 ether_sprintf(rbuf.eh.ether_shost));
139 printf("arp: cacheing %s --> %s\n",
140 inet_ntoa(addr), ether_sprintf(ah->arp_sha));
141 }
142#endif
143 MACPY(ah->arp_sha, al->ea);
144 ++arp_num;
145
146 return (al->ea);
147}
148
149static ssize_t
150arpsend(d, pkt, len)
151 struct iodesc *d;
152 void *pkt;
153 size_t len;
154{
155
156#ifdef ARP_DEBUG
157 if (debug)
158 printf("arpsend: called\n");
159#endif
160
161 return (sendether(d, pkt, len, bcea, ETHERTYPE_ARP));
162}
163
164/*
165 * Returns 0 if this is the packet we're waiting for
166 * else -1 (and errno == 0)
167 */
168static ssize_t
169arprecv(d, pkt, len, tleft)
170 struct iodesc *d;
171 void *pkt;
172 size_t len;
173 time_t tleft;
174{
175 ssize_t n;
176 struct ether_arp *ah;
177 u_int16_t etype; /* host order */
178
179#ifdef ARP_DEBUG
180 if (debug)
181 printf("arprecv: ");
182#endif
183
184 n = readether(d, pkt, len, tleft, &etype);
185 errno = 0; /* XXX */
186 if (n == -1 || n < sizeof(struct ether_arp)) {
187#ifdef ARP_DEBUG
188 if (debug)
189 printf("bad len=%d\n", n);
190#endif
191 return (-1);
192 }
193
194 if (etype != ETHERTYPE_ARP) {
195#ifdef ARP_DEBUG
196 if (debug)
197 printf("not arp type=%d\n", etype);
198#endif
199 return (-1);
200 }
201
202 /* Ethernet address now checked in readether() */
203
204 ah = (struct ether_arp *)pkt;
205 if (ah->arp_hrd != htons(ARPHRD_ETHER) ||
206 ah->arp_pro != htons(ETHERTYPE_IP) ||
207 ah->arp_hln != sizeof(ah->arp_sha) ||
208 ah->arp_pln != sizeof(ah->arp_spa) )
209 {
210#ifdef ARP_DEBUG
211 if (debug)
212 printf("bad hrd/pro/hln/pln\n");
213#endif
214 return (-1);
215 }
216
217 if (ah->arp_op == htons(ARPOP_REQUEST)) {
218#ifdef ARP_DEBUG
219 if (debug)
220 printf("is request\n");
221#endif
222 arp_reply(d, ah);
223 return (-1);
224 }
225
226 if (ah->arp_op != htons(ARPOP_REPLY)) {
227#ifdef ARP_DEBUG
228 if (debug)
229 printf("not ARP reply\n");
230#endif
231 return (-1);
232 }
233
234 /* Is the reply from the source we want? */
235 if (bcmp(&arp_list[arp_num].addr,
236 ah->arp_spa, sizeof(ah->arp_spa)))
237 {
238#ifdef ARP_DEBUG
239 if (debug)
240 printf("unwanted address\n");
241#endif
242 return (-1);
243 }
244 /* We don't care who the reply was sent to. */
245
246 /* We have our answer. */
247#ifdef ARP_DEBUG
248 if (debug)
249 printf("got it\n");
250#endif
251 return (n);
252}
253
254/*
255 * Convert an ARP request into a reply and send it.
256 * Notes: Re-uses buffer. Pad to length = 46.
257 */
258void
259arp_reply(d, pkt)
260 struct iodesc *d;
261 void *pkt; /* the request */
262{
263 struct ether_arp *arp = pkt;
264
265 if (arp->arp_hrd != htons(ARPHRD_ETHER) ||
266 arp->arp_pro != htons(ETHERTYPE_IP) ||
267 arp->arp_hln != sizeof(arp->arp_sha) ||
268 arp->arp_pln != sizeof(arp->arp_spa) )
269 {
270#ifdef ARP_DEBUG
271 if (debug)
272 printf("arp_reply: bad hrd/pro/hln/pln\n");
273#endif
274 return;
275 }
276
277 if (arp->arp_op != htons(ARPOP_REQUEST)) {
278#ifdef ARP_DEBUG
279 if (debug)
280 printf("arp_reply: not request!\n");
281#endif
282 return;
283 }
284
285 /* If we are not the target, ignore the request. */
286 if (bcmp(arp->arp_tpa, &d->myip, sizeof(arp->arp_tpa)))
287 return;
288
289#ifdef ARP_DEBUG
290 if (debug) {
291 printf("arp_reply: to %s\n", ether_sprintf(arp->arp_sha));
292 }
293#endif
294
295 arp->arp_op = htons(ARPOP_REPLY);
296 /* source becomes target */
297 bcopy(arp->arp_sha, arp->arp_tha, sizeof(arp->arp_tha));
298 bcopy(arp->arp_spa, arp->arp_tpa, sizeof(arp->arp_tpa));
299 /* here becomes source */
300 bcopy(d->myea, arp->arp_sha, sizeof(arp->arp_sha));
301 bcopy(&d->myip, arp->arp_spa, sizeof(arp->arp_spa));
302
303 /*
304 * No need to get fancy here. If the send fails, the
305 * requestor will just ask again.
306 */
307 (void) sendether(d, pkt, sizeof(*arp) + 18,
308 arp->arp_tha, ETHERTYPE_ARP);
309}