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
40 #include <sys/types.h>
41 #include <sys/socket.h>
42 #include <net/if.h>
43 #include <netinet/in.h>
44 #include <netinet/if_ether.h>
45
46 #include <netinet/in_systm.h>
47
48 #include <string.h>
49
50 #include "stand.h"
51 #include "net.h"
52
53 /* Cache stuff */
54 #define ARP_NUM 8 /* need at most 3 arp entries */
55
56 struct arp_list {
57 struct in_addr addr;
58 uchar_t ea[6];
59 } arp_list[ARP_NUM] = {
60 /* XXX - net order `INADDR_BROADCAST' must be a constant */
61 { {0xffffffff}, BA }
62 };
63 int arp_num = 1;
64
65 /* Local forwards */
66 static ssize_t arpsend(struct iodesc *, void *, size_t);
67 static ssize_t arprecv(struct iodesc *, void **, void **, time_t, void *);
68
69 /* Broadcast an ARP packet, asking who has addr on interface d */
70 uchar_t *
arpwhohas(struct iodesc * d,struct in_addr addr)71 arpwhohas(struct iodesc *d, struct in_addr addr)
72 {
73 int i;
74 struct ether_arp *ah;
75 struct arp_list *al;
76 void *pkt;
77 struct {
78 struct ether_header eh;
79 struct {
80 struct ether_arp arp;
81 uchar_t pad[18]; /* 60 - sizeof (...) */
82 } data;
83 } wbuf;
84
85 /* Try for cached answer first */
86 for (i = 0, al = arp_list; i < arp_num; ++i, ++al)
87 if (addr.s_addr == al->addr.s_addr)
88 return (al->ea);
89
90 /* Don't overflow cache */
91 if (arp_num > ARP_NUM - 1) {
92 arp_num = 1; /* recycle */
93 printf("arpwhohas: overflowed arp_list!\n");
94 }
95
96 #ifdef ARP_DEBUG
97 if (debug)
98 printf("arpwhohas: send request for %s\n", inet_ntoa(addr));
99 #endif
100
101 bzero((char *)&wbuf.data, sizeof (wbuf.data));
102 ah = &wbuf.data.arp;
103 ah->arp_hrd = htons(ARPHRD_ETHER);
104 ah->arp_pro = htons(ETHERTYPE_IP);
105 ah->arp_hln = sizeof (ah->arp_sha); /* hardware address length */
106 ah->arp_pln = sizeof (ah->arp_spa); /* protocol address length */
107 ah->arp_op = htons(ARPOP_REQUEST);
108 MACPY(d->myea, ah->arp_sha);
109 bcopy(&d->myip, ah->arp_spa, sizeof (ah->arp_spa));
110 /* Leave zeros in arp_tha */
111 bcopy(&addr, ah->arp_tpa, sizeof (ah->arp_tpa));
112
113 /* Store ip address in cache (incomplete entry). */
114 al->addr = addr;
115
116 pkt = NULL;
117 ah = NULL;
118 i = sendrecv(d,
119 arpsend, &wbuf.data, sizeof (wbuf.data),
120 arprecv, &pkt, (void **)&ah, NULL);
121 if (i == -1)
122 panic("arp: no response for %s", inet_ntoa(addr));
123
124 /* Store ethernet address in cache */
125 #ifdef ARP_DEBUG
126 if (debug) {
127 struct ether_header *eh;
128
129 eh = (struct ether_header *)((uintptr_t)pkt + ETHER_ALIGN);
130 printf("arp: response from %s\n",
131 ether_sprintf(eh->ether_shost));
132 printf("arp: cacheing %s --> %s\n",
133 inet_ntoa(addr), ether_sprintf(ah->arp_sha));
134 }
135 #endif
136 MACPY(ah->arp_sha, al->ea);
137 ++arp_num;
138 free(pkt);
139 return (al->ea);
140 }
141
142 static ssize_t
arpsend(struct iodesc * d,void * pkt,size_t len)143 arpsend(struct iodesc *d, void *pkt, size_t len)
144 {
145
146 #ifdef ARP_DEBUG
147 if (debug)
148 printf("arpsend: called\n");
149 #endif
150
151 return (sendether(d, pkt, len, bcea, ETHERTYPE_ARP));
152 }
153
154 /*
155 * Returns 0 if this is the packet we're waiting for
156 * else -1 (and errno == 0)
157 */
158 static ssize_t
arprecv(struct iodesc * d,void ** pkt,void ** payload,time_t tleft,void * extra __unused)159 arprecv(struct iodesc *d, void **pkt, void **payload, time_t tleft,
160 void *extra __unused)
161 {
162 ssize_t n;
163 struct ether_arp *ah;
164 uint16_t etype; /* host order */
165 void *ptr;
166
167 #ifdef ARP_DEBUG
168 if (debug)
169 printf("arprecv: ");
170 #endif
171
172 ptr = NULL;
173 n = readether(d, &ptr, (void **)&ah, tleft, &etype);
174 errno = 0; /* XXX */
175 if (n == -1 || n < sizeof (struct ether_arp)) {
176 #ifdef ARP_DEBUG
177 if (debug)
178 printf("bad len=%d\n", n);
179 #endif
180 free(ptr);
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 free(ptr);
190 return (-1);
191 }
192
193 /* Ethernet address now checked in readether() */
194 if (ah->arp_hrd != htons(ARPHRD_ETHER) ||
195 ah->arp_pro != htons(ETHERTYPE_IP) ||
196 ah->arp_hln != sizeof (ah->arp_sha) ||
197 ah->arp_pln != sizeof (ah->arp_spa)) {
198 #ifdef ARP_DEBUG
199 if (debug)
200 printf("bad hrd/pro/hln/pln\n");
201 #endif
202 free(ptr);
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 free(ptr);
213 return (-1);
214 }
215
216 if (ah->arp_op != htons(ARPOP_REPLY)) {
217 #ifdef ARP_DEBUG
218 if (debug)
219 printf("not ARP reply\n");
220 #endif
221 free(ptr);
222 return (-1);
223 }
224
225 /* Is the reply from the source we want? */
226 if (bcmp(&arp_list[arp_num].addr, ah->arp_spa, sizeof (ah->arp_spa))) {
227 #ifdef ARP_DEBUG
228 if (debug)
229 printf("unwanted address\n");
230 #endif
231 free(ptr);
232 return (-1);
233 }
234 /* We don't care who the reply was sent to. */
235
236 /* We have our answer. */
237 #ifdef ARP_DEBUG
238 if (debug)
239 printf("got it\n");
240 #endif
241 *pkt = ptr;
242 *payload = ah;
243 return (n);
244 }
245
246 /*
247 * Convert an ARP request into a reply and send it.
248 * Notes: Re-uses buffer. Pad to length = 46.
249 */
250 void
arp_reply(struct iodesc * d,void * pkt)251 arp_reply(struct iodesc *d, void *pkt)
252 {
253 struct ether_arp *arp = pkt;
254
255 if (arp->arp_hrd != htons(ARPHRD_ETHER) ||
256 arp->arp_pro != htons(ETHERTYPE_IP) ||
257 arp->arp_hln != sizeof (arp->arp_sha) ||
258 arp->arp_pln != sizeof (arp->arp_spa)) {
259 #ifdef ARP_DEBUG
260 if (debug)
261 printf("arp_reply: bad hrd/pro/hln/pln\n");
262 #endif
263 return;
264 }
265
266 if (arp->arp_op != htons(ARPOP_REQUEST)) {
267 #ifdef ARP_DEBUG
268 if (debug)
269 printf("arp_reply: not request!\n");
270 #endif
271 return;
272 }
273
274 /* If we are not the target, ignore the request. */
275 if (bcmp(arp->arp_tpa, &d->myip, sizeof (arp->arp_tpa)))
276 return;
277
278 #ifdef ARP_DEBUG
279 if (debug) {
280 printf("arp_reply: to %s\n", ether_sprintf(arp->arp_sha));
281 }
282 #endif
283
284 arp->arp_op = htons(ARPOP_REPLY);
285 /* source becomes target */
286 bcopy(arp->arp_sha, arp->arp_tha, sizeof (arp->arp_tha));
287 bcopy(arp->arp_spa, arp->arp_tpa, sizeof (arp->arp_tpa));
288 /* here becomes source */
289 bcopy(d->myea, arp->arp_sha, sizeof (arp->arp_sha));
290 bcopy(&d->myip, arp->arp_spa, sizeof (arp->arp_spa));
291
292 /*
293 * No need to get fancy here. If the send fails, the
294 * requestor will just ask again.
295 */
296 (void) sendether(d, pkt, sizeof (*arp) + 18,
297 arp->arp_tha, ETHERTYPE_ARP);
298 }
299