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
36 #include <sys/types.h>
37 #include <sys/socket.h>
38 #include <net/if.h>
39 #include <netinet/in.h>
40 #include <netinet/if_ether.h>
41
42 #include <netinet/in_systm.h>
43
44 #include <string.h>
45
46 #include "stand.h"
47 #include "net.h"
48
49 /* Cache stuff */
50 #define ARP_NUM 8 /* need at most 3 arp entries */
51
52 struct arp_list {
53 struct in_addr addr;
54 u_char ea[6];
55 } arp_list[ARP_NUM] = {
56 /* XXX - net order `INADDR_BROADCAST' must be a constant */
57 { {0xffffffff}, BA }
58 };
59 int arp_num = 1;
60
61 /* Local forwards */
62 static ssize_t arpsend(struct iodesc *, void *, size_t);
63 static ssize_t arprecv(struct iodesc *, void **, void **, time_t, void *);
64
65 /* Broadcast an ARP packet, asking who has addr on interface d */
66 u_char *
arpwhohas(struct iodesc * d,struct in_addr addr)67 arpwhohas(struct iodesc *d, struct in_addr addr)
68 {
69 int i;
70 struct ether_arp *ah;
71 struct arp_list *al;
72 void *pkt;
73 struct {
74 struct ether_header eh;
75 struct {
76 struct ether_arp arp;
77 u_char pad[18]; /* 60 - sizeof(...) */
78 } data;
79 } wbuf;
80
81 /* Try for cached answer first */
82 for (i = 0, al = arp_list; i < arp_num; ++i, ++al)
83 if (addr.s_addr == al->addr.s_addr)
84 return (al->ea);
85
86 /* Don't overflow cache */
87 if (arp_num > ARP_NUM - 1) {
88 arp_num = 1; /* recycle */
89 printf("arpwhohas: overflowed arp_list!\n");
90 }
91
92 #ifdef ARP_DEBUG
93 if (debug)
94 printf("arpwhohas: send request for %s\n", inet_ntoa(addr));
95 #endif
96
97 bzero((char*)&wbuf.data, sizeof(wbuf.data));
98 ah = &wbuf.data.arp;
99 ah->arp_hrd = htons(ARPHRD_ETHER);
100 ah->arp_pro = htons(ETHERTYPE_IP);
101 ah->arp_hln = sizeof(ah->arp_sha); /* hardware address length */
102 ah->arp_pln = sizeof(ah->arp_spa); /* protocol address length */
103 ah->arp_op = htons(ARPOP_REQUEST);
104 MACPY(d->myea, ah->arp_sha);
105 bcopy(&d->myip, ah->arp_spa, sizeof(ah->arp_spa));
106 /* Leave zeros in arp_tha */
107 bcopy(&addr, ah->arp_tpa, sizeof(ah->arp_tpa));
108
109 /* Store ip address in cache (incomplete entry). */
110 al->addr = addr;
111
112 pkt = NULL;
113 ah = NULL;
114 i = sendrecv(d,
115 arpsend, &wbuf.data, sizeof(wbuf.data),
116 arprecv, &pkt, (void **)&ah, NULL);
117 if (i == -1) {
118 panic("arp: no response for %s",
119 inet_ntoa(addr));
120 }
121
122 /* Store ethernet address in cache */
123 #ifdef ARP_DEBUG
124 if (debug) {
125 struct ether_header *eh;
126
127 eh = (struct ether_header *)((uintptr_t)pkt + ETHER_ALIGN);
128 printf("arp: response from %s\n",
129 ether_sprintf(eh->ether_shost));
130 printf("arp: cacheing %s --> %s\n",
131 inet_ntoa(addr), ether_sprintf(ah->arp_sha));
132 }
133 #endif
134 MACPY(ah->arp_sha, al->ea);
135 ++arp_num;
136
137 free(pkt);
138 return (al->ea);
139 }
140
141 static ssize_t
arpsend(struct iodesc * d,void * pkt,size_t len)142 arpsend(struct iodesc *d, void *pkt, size_t len)
143 {
144
145 #ifdef ARP_DEBUG
146 if (debug)
147 printf("arpsend: called\n");
148 #endif
149
150 return (sendether(d, pkt, len, bcea, ETHERTYPE_ARP));
151 }
152
153 /*
154 * Returns 0 if this is the packet we're waiting for
155 * else -1 (and errno == 0)
156 */
157 static ssize_t
arprecv(struct iodesc * d,void ** pkt,void ** payload,time_t tleft,void * extra)158 arprecv(struct iodesc *d, void **pkt, void **payload, time_t tleft, void *extra)
159 {
160 ssize_t n;
161 struct ether_arp *ah;
162 uint16_t etype; /* host order */
163 void *ptr;
164
165 #ifdef ARP_DEBUG
166 if (debug)
167 printf("arprecv: ");
168 #endif
169
170 ptr = NULL;
171 n = readether(d, &ptr, (void **)&ah, tleft, &etype);
172 errno = 0; /* XXX */
173 if (n == -1 || n < sizeof(struct ether_arp)) {
174 #ifdef ARP_DEBUG
175 if (debug)
176 printf("bad len=%zd\n", n);
177 #endif
178 free(ptr);
179 return (-1);
180 }
181
182 if (etype != ETHERTYPE_ARP) {
183 #ifdef ARP_DEBUG
184 if (debug)
185 printf("not arp type=%d\n", etype);
186 #endif
187 free(ptr);
188 return (-1);
189 }
190
191 /* Ethernet address now checked in readether() */
192 if (ah->arp_hrd != htons(ARPHRD_ETHER) ||
193 ah->arp_pro != htons(ETHERTYPE_IP) ||
194 ah->arp_hln != sizeof(ah->arp_sha) ||
195 ah->arp_pln != sizeof(ah->arp_spa) )
196 {
197 #ifdef ARP_DEBUG
198 if (debug)
199 printf("bad hrd/pro/hln/pln\n");
200 #endif
201 free(ptr);
202 return (-1);
203 }
204
205 if (ah->arp_op == htons(ARPOP_REQUEST)) {
206 #ifdef ARP_DEBUG
207 if (debug)
208 printf("is request\n");
209 #endif
210 arp_reply(d, ah);
211 free(ptr);
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 free(ptr);
221 return (-1);
222 }
223
224 /* Is the reply from the source we want? */
225 if (bcmp(&arp_list[arp_num].addr,
226 ah->arp_spa, sizeof(ah->arp_spa)))
227 {
228 #ifdef ARP_DEBUG
229 if (debug)
230 printf("unwanted address\n");
231 #endif
232 free(ptr);
233 return (-1);
234 }
235 /* We don't care who the reply was sent to. */
236
237 /* We have our answer. */
238 #ifdef ARP_DEBUG
239 if (debug)
240 printf("got it\n");
241 #endif
242 *pkt = ptr;
243 *payload = ah;
244 return (n);
245 }
246
247 /*
248 * Convert an ARP request into a reply and send it.
249 * Notes: Re-uses buffer. Pad to length = 46.
250 */
251 void
arp_reply(struct iodesc * d,void * pkt)252 arp_reply(struct iodesc *d, void *pkt)
253 {
254 struct ether_arp *arp = pkt;
255
256 if (arp->arp_hrd != htons(ARPHRD_ETHER) ||
257 arp->arp_pro != htons(ETHERTYPE_IP) ||
258 arp->arp_hln != sizeof(arp->arp_sha) ||
259 arp->arp_pln != sizeof(arp->arp_spa) )
260 {
261 #ifdef ARP_DEBUG
262 if (debug)
263 printf("arp_reply: bad hrd/pro/hln/pln\n");
264 #endif
265 return;
266 }
267
268 if (arp->arp_op != htons(ARPOP_REQUEST)) {
269 #ifdef ARP_DEBUG
270 if (debug)
271 printf("arp_reply: not request!\n");
272 #endif
273 return;
274 }
275
276 /* If we are not the target, ignore the request. */
277 if (bcmp(arp->arp_tpa, &d->myip, sizeof(arp->arp_tpa)))
278 return;
279
280 #ifdef ARP_DEBUG
281 if (debug) {
282 printf("arp_reply: to %s\n", ether_sprintf(arp->arp_sha));
283 }
284 #endif
285
286 arp->arp_op = htons(ARPOP_REPLY);
287 /* source becomes target */
288 bcopy(arp->arp_sha, arp->arp_tha, sizeof(arp->arp_tha));
289 bcopy(arp->arp_spa, arp->arp_tpa, sizeof(arp->arp_tpa));
290 /* here becomes source */
291 bcopy(d->myea, arp->arp_sha, sizeof(arp->arp_sha));
292 bcopy(&d->myip, arp->arp_spa, sizeof(arp->arp_spa));
293
294 /*
295 * No need to get fancy here. If the send fails, the
296 * requestor will just ask again.
297 */
298 (void) sendether(d, pkt, sizeof(*arp) + 18,
299 arp->arp_tha, ETHERTYPE_ARP);
300 }
301