1 /* $OpenBSD: arp.c,v 1.11 2003/08/11 06:23:09 deraadt Exp $ */
2 /* $NetBSD: arp.c,v 1.15 1996/10/13 02:28:58 christos Exp $ */
3
4 /*
5 * Copyright (c) 1992 Regents of the University of California.
6 * All rights reserved.
7 *
8 * This software was developed by the Computer Systems Engineering group
9 * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
10 * contributed to Berkeley.
11 *
12 * Redistribution and use in source and binary forms, with or without
13 * modification, are permitted provided that the following conditions
14 * are met:
15 * 1. Redistributions of source code must retain the above copyright
16 * notice, this list of conditions and the following disclaimer.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 * notice, this list of conditions and the following disclaimer in the
19 * documentation and/or other materials provided with the distribution.
20 * 3. All advertising materials mentioning features or use of this software
21 * must display the following acknowledgement:
22 * This product includes software developed by the University of
23 * California, Lawrence Berkeley Laboratory and its contributors.
24 * 4. Neither the name of the University nor the names of its contributors
25 * may be used to endorse or promote products derived from this software
26 * without specific prior written permission.
27 *
28 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
29 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
30 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
31 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
32 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
33 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
34 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
35 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
37 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
38 * SUCH DAMAGE.
39 *
40 * @(#) Header: arp.c,v 1.5 93/07/15 05:52:26 leres Exp (LBL)
41 */
42
43 #include <sys/types.h>
44 #include <sys/socket.h>
45 #include <net/if.h>
46 #include <netinet/in.h>
47
48 #include <netinet/if_ether.h>
49 #include <netinet/in_systm.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
57 struct 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 };
64 int arp_num = 1;
65
66 /* Local forwards */
67 static ssize_t arpsend(struct iodesc *, void *, size_t);
68 static ssize_t arprecv(struct iodesc *, void *, size_t, time_t);
69
70 /* Broadcast an ARP packet, asking who has addr on interface d */
71 u_char *
72 arpwhohas(struct iodesc *d, struct in_addr addr)
73 {
74 int i;
75 struct ether_arp *ah;
76 struct arp_list *al;
77 struct {
78 struct ether_header eh;
79 struct {
80 struct ether_arp arp;
81 u_char pad[18]; /* 60 - sizeof(...) */
82 } data;
83 } wbuf;
84 struct {
85 struct ether_header eh;
86 struct {
87 struct ether_arp arp;
88 u_char pad[24]; /* extra space */
89 } data;
90 } rbuf;
91
92 /* Try for cached answer first */
93 for (i = 0, al = arp_list; i < arp_num; ++i, ++al)
94 if (addr.s_addr == al->addr.s_addr)
95 return (al->ea);
96
97 /* Don't overflow cache */
98 if (arp_num > ARP_NUM - 1) {
99 arp_num = 1; /* recycle */
100 printf("arpwhohas: overflowed arp_list!\n");
101 }
102
103 #ifdef ARP_DEBUG
104 if (debug)
105 printf("arpwhohas: send request for %s\n", inet_ntoa(addr));
106 #endif
107
108 bzero((char *)&wbuf.data, sizeof(wbuf.data));
109 ah = &wbuf.data.arp;
110 ah->arp_hrd = htons(ARPHRD_ETHER);
111 ah->arp_pro = htons(ETHERTYPE_IP);
112 ah->arp_hln = sizeof(ah->arp_sha); /* hardware address length */
113 ah->arp_pln = sizeof(ah->arp_spa); /* protocol address length */
114 ah->arp_op = htons(ARPOP_REQUEST);
115 MACPY(d->myea, ah->arp_sha);
116 bcopy(&d->myip, ah->arp_spa, sizeof(ah->arp_spa));
117 /* Leave zeros in arp_tha */
118 bcopy(&addr, ah->arp_tpa, sizeof(ah->arp_tpa));
119
120 /* Store ip address in cache (incomplete entry). */
121 al->addr = addr;
122
123 i = sendrecv(d,
124 arpsend, &wbuf.data, sizeof(wbuf.data),
125 arprecv, &rbuf.data, sizeof(rbuf.data));
126 if (i == -1) {
127 panic("arp: no response for %s", inet_ntoa(addr));
128 }
129
130 /* Store ethernet address in cache */
131 ah = &rbuf.data.arp;
132 #ifdef ARP_DEBUG
133 if (debug) {
134 printf("arp: response from %s\n",
135 ether_sprintf(rbuf.eh.ether_shost));
136 printf("arp: cacheing %s --> %s\n",
137 inet_ntoa(addr), ether_sprintf(ah->arp_sha));
138 }
139 #endif
140 MACPY(ah->arp_sha, al->ea);
141 ++arp_num;
142
143 return (al->ea);
144 }
145
146 static ssize_t
147 arpsend(struct iodesc *d, void *pkt, size_t len)
148 {
149
150 #ifdef ARP_DEBUG
151 if (debug)
152 printf("arpsend: called\n");
153 #endif
154
155 return (sendether(d, pkt, len, bcea, ETHERTYPE_ARP));
156 }
157
158 /*
159 * Returns 0 if this is the packet we're waiting for
160 * else -1 (and errno == 0)
161 */
162 static ssize_t
163 arprecv(struct iodesc *d, void *pkt, size_t len, time_t tleft)
164 {
165 ssize_t n;
166 struct ether_arp *ah;
167 u_int16_t etype; /* host order */
168
169 #ifdef ARP_DEBUG
170 if (debug)
171 printf("arprecv: ");
172 #endif
173
174 n = readether(d, pkt, len, tleft, &etype);
175 errno = 0; /* XXX */
176 if (n < 0 || (size_t)n < sizeof(struct ether_arp)) {
177 #ifdef ARP_DEBUG
178 if (debug)
179 printf("bad len=%d\n", n);
180 #endif
181 return (-1);
182 }
183
184 if (etype != ETHERTYPE_ARP) {
185 #ifdef ARP_DEBUG
186 if (debug)
187 printf("not arp type=%d\n", etype);
188 #endif
189 return (-1);
190 }
191
192 /* Ethernet address now checked in readether() */
193
194 ah = (struct ether_arp *)pkt;
195 if (ah->arp_hrd != htons(ARPHRD_ETHER) ||
196 ah->arp_pro != htons(ETHERTYPE_IP) ||
197 ah->arp_hln != sizeof(ah->arp_sha) ||
198 ah->arp_pln != sizeof(ah->arp_spa)) {
199 #ifdef ARP_DEBUG
200 if (debug)
201 printf("bad hrd/pro/hln/pln\n");
202 #endif
203 return (-1);
204 }
205
206 if (ah->arp_op == htons(ARPOP_REQUEST)) {
207 #ifdef ARP_DEBUG
208 if (debug)
209 printf("is request\n");
210 #endif
211 arp_reply(d, ah);
212 return (-1);
213 }
214
215 if (ah->arp_op != htons(ARPOP_REPLY)) {
216 #ifdef ARP_DEBUG
217 if (debug)
218 printf("not ARP reply\n");
219 #endif
220 return (-1);
221 }
222
223 /* Is the reply from the source we want? */
224 if (bcmp(&arp_list[arp_num].addr, ah->arp_spa,
225 sizeof(ah->arp_spa))) {
226 #ifdef ARP_DEBUG
227 if (debug)
228 printf("unwanted address\n");
229 #endif
230 return (-1);
231 }
232 /* We don't care who the reply was sent to. */
233
234 /* We have our answer. */
235 #ifdef ARP_DEBUG
236 if (debug)
237 printf("got it\n");
238 #endif
239 return (n);
240 }
241
242 /*
243 * Convert an ARP request into a reply and send it.
244 * Notes: Re-uses buffer. Pad to length = 46.
245 */
246 void
247 arp_reply(struct iodesc *d, void *pkt)
248 {
249 struct ether_arp *arp = pkt;
250
251 if (arp->arp_hrd != htons(ARPHRD_ETHER) ||
252 arp->arp_pro != htons(ETHERTYPE_IP) ||
253 arp->arp_hln != sizeof(arp->arp_sha) ||
254 arp->arp_pln != sizeof(arp->arp_spa)) {
255 #ifdef ARP_DEBUG
256 if (debug)
257 printf("arp_reply: bad hrd/pro/hln/pln\n");
258 #endif
259 return;
260 }
261
262 if (arp->arp_op != htons(ARPOP_REQUEST)) {
263 #ifdef ARP_DEBUG
264 if (debug)
265 printf("arp_reply: not request!\n");
266 #endif
267 return;
268 }
269
270 /* If we are not the target, ignore the request. */
271 if (bcmp(arp->arp_tpa, &d->myip, sizeof(arp->arp_tpa)))
272 return;
273
274 #ifdef ARP_DEBUG
275 if (debug) {
276 printf("arp_reply: to %s\n", ether_sprintf(arp->arp_sha));
277 }
278 #endif
279
280 arp->arp_op = htons(ARPOP_REPLY);
281 /* source becomes target */
282 bcopy(arp->arp_sha, arp->arp_tha, sizeof(arp->arp_tha));
283 bcopy(arp->arp_spa, arp->arp_tpa, sizeof(arp->arp_tpa));
284 /* here becomes source */
285 bcopy(d->myea, arp->arp_sha, sizeof(arp->arp_sha));
286 bcopy(&d->myip, arp->arp_spa, sizeof(arp->arp_spa));
287
288 /*
289 * No need to get fancy here. If the send fails, the
290 * requestor will just ask again.
291 */
292 (void) sendether(d, pkt, sizeof(*arp) + 18,
293 arp->arp_tha, ETHERTYPE_ARP);
294 }