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. 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>
39 __FBSDID("$FreeBSD$");
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
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 **, void **, time_t, void *);
69
70 /* Broadcast an ARP packet, asking who has addr on interface d */
71 u_char *
arpwhohas(struct iodesc * d,struct in_addr addr)72 arpwhohas(struct iodesc *d, struct in_addr addr)
73 {
74 int i;
75 struct ether_arp *ah;
76 struct arp_list *al;
77 void *pkt;
78 struct {
79 struct ether_header eh;
80 struct {
81 struct ether_arp arp;
82 u_char pad[18]; /* 60 - sizeof(...) */
83 } data;
84 } wbuf;
85
86 /* Try for cached answer first */
87 for (i = 0, al = arp_list; i < arp_num; ++i, ++al)
88 if (addr.s_addr == al->addr.s_addr)
89 return (al->ea);
90
91 /* Don't overflow cache */
92 if (arp_num > ARP_NUM - 1) {
93 arp_num = 1; /* recycle */
94 printf("arpwhohas: overflowed arp_list!\n");
95 }
96
97 #ifdef ARP_DEBUG
98 if (debug)
99 printf("arpwhohas: send request for %s\n", inet_ntoa(addr));
100 #endif
101
102 bzero((char*)&wbuf.data, sizeof(wbuf.data));
103 ah = &wbuf.data.arp;
104 ah->arp_hrd = htons(ARPHRD_ETHER);
105 ah->arp_pro = htons(ETHERTYPE_IP);
106 ah->arp_hln = sizeof(ah->arp_sha); /* hardware address length */
107 ah->arp_pln = sizeof(ah->arp_spa); /* protocol address length */
108 ah->arp_op = htons(ARPOP_REQUEST);
109 MACPY(d->myea, ah->arp_sha);
110 bcopy(&d->myip, ah->arp_spa, sizeof(ah->arp_spa));
111 /* Leave zeros in arp_tha */
112 bcopy(&addr, ah->arp_tpa, sizeof(ah->arp_tpa));
113
114 /* Store ip address in cache (incomplete entry). */
115 al->addr = addr;
116
117 pkt = NULL;
118 ah = NULL;
119 i = sendrecv(d,
120 arpsend, &wbuf.data, sizeof(wbuf.data),
121 arprecv, &pkt, (void **)&ah, NULL);
122 if (i == -1) {
123 panic("arp: no response for %s",
124 inet_ntoa(addr));
125 }
126
127 /* Store ethernet address in cache */
128 #ifdef ARP_DEBUG
129 if (debug) {
130 struct ether_header *eh;
131
132 eh = (struct ether_header *)((uintptr_t)pkt + ETHER_ALIGN);
133 printf("arp: response from %s\n",
134 ether_sprintf(eh->ether_shost));
135 printf("arp: cacheing %s --> %s\n",
136 inet_ntoa(addr), ether_sprintf(ah->arp_sha));
137 }
138 #endif
139 MACPY(ah->arp_sha, al->ea);
140 ++arp_num;
141
142 free(pkt);
143 return (al->ea);
144 }
145
146 static ssize_t
arpsend(struct iodesc * d,void * pkt,size_t len)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
arprecv(struct iodesc * d,void ** pkt,void ** payload,time_t tleft,void * extra)163 arprecv(struct iodesc *d, void **pkt, void **payload, time_t tleft, void *extra)
164 {
165 ssize_t n;
166 struct ether_arp *ah;
167 uint16_t etype; /* host order */
168 void *ptr;
169
170 #ifdef ARP_DEBUG
171 if (debug)
172 printf("arprecv: ");
173 #endif
174
175 ptr = NULL;
176 n = readether(d, &ptr, (void **)&ah, tleft, &etype);
177 errno = 0; /* XXX */
178 if (n == -1 || n < sizeof(struct ether_arp)) {
179 #ifdef ARP_DEBUG
180 if (debug)
181 printf("bad len=%d\n", n);
182 #endif
183 free(ptr);
184 return (-1);
185 }
186
187 if (etype != ETHERTYPE_ARP) {
188 #ifdef ARP_DEBUG
189 if (debug)
190 printf("not arp type=%d\n", etype);
191 #endif
192 free(ptr);
193 return (-1);
194 }
195
196 /* Ethernet address now checked in readether() */
197 if (ah->arp_hrd != htons(ARPHRD_ETHER) ||
198 ah->arp_pro != htons(ETHERTYPE_IP) ||
199 ah->arp_hln != sizeof(ah->arp_sha) ||
200 ah->arp_pln != sizeof(ah->arp_spa) )
201 {
202 #ifdef ARP_DEBUG
203 if (debug)
204 printf("bad hrd/pro/hln/pln\n");
205 #endif
206 free(ptr);
207 return (-1);
208 }
209
210 if (ah->arp_op == htons(ARPOP_REQUEST)) {
211 #ifdef ARP_DEBUG
212 if (debug)
213 printf("is request\n");
214 #endif
215 arp_reply(d, ah);
216 free(ptr);
217 return (-1);
218 }
219
220 if (ah->arp_op != htons(ARPOP_REPLY)) {
221 #ifdef ARP_DEBUG
222 if (debug)
223 printf("not ARP reply\n");
224 #endif
225 free(ptr);
226 return (-1);
227 }
228
229 /* Is the reply from the source we want? */
230 if (bcmp(&arp_list[arp_num].addr,
231 ah->arp_spa, sizeof(ah->arp_spa)))
232 {
233 #ifdef ARP_DEBUG
234 if (debug)
235 printf("unwanted address\n");
236 #endif
237 free(ptr);
238 return (-1);
239 }
240 /* We don't care who the reply was sent to. */
241
242 /* We have our answer. */
243 #ifdef ARP_DEBUG
244 if (debug)
245 printf("got it\n");
246 #endif
247 *pkt = ptr;
248 *payload = ah;
249 return (n);
250 }
251
252 /*
253 * Convert an ARP request into a reply and send it.
254 * Notes: Re-uses buffer. Pad to length = 46.
255 */
256 void
arp_reply(struct iodesc * d,void * pkt)257 arp_reply(struct iodesc *d, void *pkt)
258 {
259 struct ether_arp *arp = pkt;
260
261 if (arp->arp_hrd != htons(ARPHRD_ETHER) ||
262 arp->arp_pro != htons(ETHERTYPE_IP) ||
263 arp->arp_hln != sizeof(arp->arp_sha) ||
264 arp->arp_pln != sizeof(arp->arp_spa) )
265 {
266 #ifdef ARP_DEBUG
267 if (debug)
268 printf("arp_reply: bad hrd/pro/hln/pln\n");
269 #endif
270 return;
271 }
272
273 if (arp->arp_op != htons(ARPOP_REQUEST)) {
274 #ifdef ARP_DEBUG
275 if (debug)
276 printf("arp_reply: not request!\n");
277 #endif
278 return;
279 }
280
281 /* If we are not the target, ignore the request. */
282 if (bcmp(arp->arp_tpa, &d->myip, sizeof(arp->arp_tpa)))
283 return;
284
285 #ifdef ARP_DEBUG
286 if (debug) {
287 printf("arp_reply: to %s\n", ether_sprintf(arp->arp_sha));
288 }
289 #endif
290
291 arp->arp_op = htons(ARPOP_REPLY);
292 /* source becomes target */
293 bcopy(arp->arp_sha, arp->arp_tha, sizeof(arp->arp_tha));
294 bcopy(arp->arp_spa, arp->arp_tpa, sizeof(arp->arp_tpa));
295 /* here becomes source */
296 bcopy(d->myea, arp->arp_sha, sizeof(arp->arp_sha));
297 bcopy(&d->myip, arp->arp_spa, sizeof(arp->arp_spa));
298
299 /*
300 * No need to get fancy here. If the send fails, the
301 * requestor will just ask again.
302 */
303 (void) sendether(d, pkt, sizeof(*arp) + 18,
304 arp->arp_tha, ETHERTYPE_ARP);
305 }
306