FreeBSD/Linux Kernel Cross Reference
sys/lib/libsa/arp.c
1 /* $NetBSD: arp.c,v 1.24 2003/08/31 22:40:47 fvdl 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.
23 * 4. Neither the name of the University nor the names of its contributors
24 * may be used to endorse or promote products derived from this software
25 * without specific prior written permission.
26 *
27 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
28 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
29 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
30 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
31 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
32 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
33 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
34 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
35 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
36 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
37 * SUCH DAMAGE.
38 *
39 * @(#) Header: arp.c,v 1.5 93/07/15 05:52:26 leres Exp (LBL)
40 */
41
42 #include <sys/types.h>
43 #include <sys/socket.h>
44 #include <net/if.h>
45 #include <net/if_ether.h>
46 #include <netinet/in.h>
47
48 #include <netinet/in_systm.h>
49
50 #ifdef _STANDALONE
51 #include <lib/libkern/libkern.h>
52 #else
53 #include <string.h>
54 #endif
55
56 #include "stand.h"
57 #include "net.h"
58
59 /*
60 * Ethernet Address Resolution Protocol.
61 *
62 * See RFC 826 for protocol description. Structure below is adapted
63 * to resolving internet addresses. Field names used correspond to
64 * RFC 826.
65 */
66 struct ether_arp {
67 struct arphdr ea_hdr; /* fixed-size header */
68 u_int8_t arp_sha[ETHER_ADDR_LEN]; /* sender hardware address */
69 u_int8_t arp_spa[4]; /* sender protocol address */
70 u_int8_t arp_tha[ETHER_ADDR_LEN]; /* target hardware address */
71 u_int8_t arp_tpa[4]; /* target protocol address */
72 };
73 #define arp_hrd ea_hdr.ar_hrd
74 #define arp_pro ea_hdr.ar_pro
75 #define arp_hln ea_hdr.ar_hln
76 #define arp_pln ea_hdr.ar_pln
77 #define arp_op ea_hdr.ar_op
78
79 /* Cache stuff */
80 #define ARP_NUM 8 /* need at most 3 arp entries */
81
82 struct arp_list {
83 struct in_addr addr;
84 u_char ea[6];
85 } arp_list[ARP_NUM] = {
86 /* XXX - net order `INADDR_BROADCAST' must be a constant */
87 { {0xffffffff}, BA }
88 };
89 int arp_num = 1;
90
91 /* Local forwards */
92 static ssize_t arpsend __P((struct iodesc *, void *, size_t));
93 static ssize_t arprecv __P((struct iodesc *, void *, size_t, time_t));
94
95 /* Broadcast an ARP packet, asking who has addr on interface d */
96 u_char *
97 arpwhohas(d, addr)
98 struct iodesc *d;
99 struct in_addr addr;
100 {
101 int i;
102 struct ether_arp *ah;
103 struct arp_list *al;
104 struct {
105 struct ether_header eh;
106 struct {
107 struct ether_arp arp;
108 u_char pad[18]; /* 60 - sizeof(...) */
109 } data;
110 } wbuf;
111 struct {
112 struct ether_header eh;
113 struct {
114 struct ether_arp arp;
115 u_char pad[24]; /* extra space */
116 } data;
117 } rbuf;
118
119 /* Try for cached answer first */
120 for (i = 0, al = arp_list; i < arp_num; ++i, ++al)
121 if (addr.s_addr == al->addr.s_addr)
122 return (al->ea);
123
124 /* Don't overflow cache */
125 if (arp_num > ARP_NUM - 1) {
126 arp_num = 1; /* recycle */
127 printf("arpwhohas: overflowed arp_list!\n");
128 }
129
130 #ifdef ARP_DEBUG
131 if (debug)
132 printf("arpwhohas: send request for %s\n", inet_ntoa(addr));
133 #endif
134
135 bzero((char*)&wbuf.data, sizeof(wbuf.data));
136 ah = &wbuf.data.arp;
137 ah->arp_hrd = htons(ARPHRD_ETHER);
138 ah->arp_pro = htons(ETHERTYPE_IP);
139 ah->arp_hln = sizeof(ah->arp_sha); /* hardware address length */
140 ah->arp_pln = sizeof(ah->arp_spa); /* protocol address length */
141 ah->arp_op = htons(ARPOP_REQUEST);
142 MACPY(d->myea, ah->arp_sha);
143 bcopy(&d->myip, ah->arp_spa, sizeof(ah->arp_spa));
144 /* Leave zeros in arp_tha */
145 bcopy(&addr, ah->arp_tpa, sizeof(ah->arp_tpa));
146
147 /* Store ip address in cache (incomplete entry). */
148 al->addr = addr;
149
150 i = sendrecv(d,
151 arpsend, &wbuf.data, sizeof(wbuf.data),
152 arprecv, &rbuf.data, sizeof(rbuf.data));
153 if (i == -1) {
154 panic("arp: no response for %s",
155 inet_ntoa(addr));
156 }
157
158 /* Store ethernet address in cache */
159 ah = &rbuf.data.arp;
160 #ifdef ARP_DEBUG
161 if (debug) {
162 printf("arp: response from %s\n",
163 ether_sprintf(rbuf.eh.ether_shost));
164 printf("arp: cacheing %s --> %s\n",
165 inet_ntoa(addr), ether_sprintf(ah->arp_sha));
166 }
167 #endif
168 MACPY(ah->arp_sha, al->ea);
169 ++arp_num;
170
171 return (al->ea);
172 }
173
174 static ssize_t
175 arpsend(d, pkt, len)
176 struct iodesc *d;
177 void *pkt;
178 size_t len;
179 {
180
181 #ifdef ARP_DEBUG
182 if (debug)
183 printf("arpsend: called\n");
184 #endif
185
186 return (sendether(d, pkt, len, bcea, ETHERTYPE_ARP));
187 }
188
189 /*
190 * Returns 0 if this is the packet we're waiting for
191 * else -1 (and errno == 0)
192 */
193 static ssize_t
194 arprecv(d, pkt, len, tleft)
195 struct iodesc *d;
196 void *pkt;
197 size_t len;
198 time_t tleft;
199 {
200 ssize_t n;
201 struct ether_arp *ah;
202 u_int16_t etype; /* host order */
203
204 #ifdef ARP_DEBUG
205 if (debug)
206 printf("arprecv: ");
207 #endif
208
209 n = readether(d, pkt, len, tleft, &etype);
210 errno = 0; /* XXX */
211 if (n == -1 || (size_t)n < sizeof(struct ether_arp)) {
212 #ifdef ARP_DEBUG
213 if (debug)
214 printf("bad len=%ld\n", (signed long) n);
215 #endif
216 return (-1);
217 }
218
219 if (etype != ETHERTYPE_ARP) {
220 #ifdef ARP_DEBUG
221 if (debug)
222 printf("not arp type=%d\n", etype);
223 #endif
224 return (-1);
225 }
226
227 /* Ethernet address now checked in readether() */
228
229 ah = (struct ether_arp *)pkt;
230 if (ah->arp_hrd != htons(ARPHRD_ETHER) ||
231 ah->arp_pro != htons(ETHERTYPE_IP) ||
232 ah->arp_hln != sizeof(ah->arp_sha) ||
233 ah->arp_pln != sizeof(ah->arp_spa) )
234 {
235 #ifdef ARP_DEBUG
236 if (debug)
237 printf("bad hrd/pro/hln/pln\n");
238 #endif
239 return (-1);
240 }
241
242 if (ah->arp_op == htons(ARPOP_REQUEST)) {
243 #ifdef ARP_DEBUG
244 if (debug)
245 printf("is request\n");
246 #endif
247 arp_reply(d, ah);
248 return (-1);
249 }
250
251 if (ah->arp_op != htons(ARPOP_REPLY)) {
252 #ifdef ARP_DEBUG
253 if (debug)
254 printf("not ARP reply\n");
255 #endif
256 return (-1);
257 }
258
259 /* Is the reply from the source we want? */
260 if (bcmp(&arp_list[arp_num].addr,
261 ah->arp_spa, sizeof(ah->arp_spa)))
262 {
263 #ifdef ARP_DEBUG
264 if (debug)
265 printf("unwanted address\n");
266 #endif
267 return (-1);
268 }
269 /* We don't care who the reply was sent to. */
270
271 /* We have our answer. */
272 #ifdef ARP_DEBUG
273 if (debug)
274 printf("got it\n");
275 #endif
276 return (n);
277 }
278
279 /*
280 * Convert an ARP request into a reply and send it.
281 * Notes: Re-uses buffer. Pad to length = 46.
282 */
283 void
284 arp_reply(d, pkt)
285 struct iodesc *d;
286 void *pkt; /* the request */
287 {
288 struct ether_arp *arp = pkt;
289
290 if (arp->arp_hrd != htons(ARPHRD_ETHER) ||
291 arp->arp_pro != htons(ETHERTYPE_IP) ||
292 arp->arp_hln != sizeof(arp->arp_sha) ||
293 arp->arp_pln != sizeof(arp->arp_spa) )
294 {
295 #ifdef ARP_DEBUG
296 if (debug)
297 printf("arp_reply: bad hrd/pro/hln/pln\n");
298 #endif
299 return;
300 }
301
302 if (arp->arp_op != htons(ARPOP_REQUEST)) {
303 #ifdef ARP_DEBUG
304 if (debug)
305 printf("arp_reply: not request!\n");
306 #endif
307 return;
308 }
309
310 /* If we are not the target, ignore the request. */
311 if (bcmp(arp->arp_tpa, &d->myip, sizeof(arp->arp_tpa)))
312 return;
313
314 #ifdef ARP_DEBUG
315 if (debug) {
316 printf("arp_reply: to %s\n", ether_sprintf(arp->arp_sha));
317 }
318 #endif
319
320 arp->arp_op = htons(ARPOP_REPLY);
321 /* source becomes target */
322 bcopy(arp->arp_sha, arp->arp_tha, sizeof(arp->arp_tha));
323 bcopy(arp->arp_spa, arp->arp_tpa, sizeof(arp->arp_tpa));
324 /* here becomes source */
325 bcopy(d->myea, arp->arp_sha, sizeof(arp->arp_sha));
326 bcopy(&d->myip, arp->arp_spa, sizeof(arp->arp_spa));
327
328 /*
329 * No need to get fancy here. If the send fails, the
330 * requestor will just ask again.
331 */
332 (void) sendether(d, pkt, sizeof(*arp) + 18,
333 arp->arp_tha, ETHERTYPE_ARP);
334 }
Cache object: 03f06deb0789ed058f2d313123ccd659
|