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 * 4. 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
57struct 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};
64int arp_num = 1;
65
66/* Local forwards */
67static	ssize_t arpsend(struct iodesc *, void *, size_t);
68static	ssize_t arprecv(struct iodesc *, void *, size_t, time_t);
69
70/* Broadcast an ARP packet, asking who has addr on interface d */
71u_char *
72arpwhohas(d, addr)
73	struct iodesc *d;
74	struct in_addr addr;
75{
76	int i;
77	struct ether_arp *ah;
78	struct arp_list *al;
79	struct {
80		struct ether_header eh;
81		struct {
82			struct ether_arp arp;
83			u_char pad[18]; 	/* 60 - sizeof(...) */
84		} data;
85	} wbuf;
86	struct {
87		struct ether_header eh;
88		struct {
89			struct ether_arp arp;
90			u_char pad[24]; 	/* extra space */
91		} data;
92	} rbuf;
93
94	/* Try for cached answer first */
95	for (i = 0, al = arp_list; i < arp_num; ++i, ++al)
96		if (addr.s_addr == al->addr.s_addr)
97			return (al->ea);
98
99	/* Don't overflow cache */
100	if (arp_num > ARP_NUM - 1) {
101		arp_num = 1;	/* recycle */
102		printf("arpwhohas: overflowed arp_list!\n");
103	}
104
105#ifdef ARP_DEBUG
106 	if (debug)
107 	    printf("arpwhohas: send request for %s\n", inet_ntoa(addr));
108#endif
109
110	bzero((char*)&wbuf.data, sizeof(wbuf.data));
111	ah = &wbuf.data.arp;
112	ah->arp_hrd = htons(ARPHRD_ETHER);
113	ah->arp_pro = htons(ETHERTYPE_IP);
114	ah->arp_hln = sizeof(ah->arp_sha); /* hardware address length */
115	ah->arp_pln = sizeof(ah->arp_spa); /* protocol address length */
116	ah->arp_op = htons(ARPOP_REQUEST);
117	MACPY(d->myea, ah->arp_sha);
118	bcopy(&d->myip, ah->arp_spa, sizeof(ah->arp_spa));
119	/* Leave zeros in arp_tha */
120	bcopy(&addr, ah->arp_tpa, sizeof(ah->arp_tpa));
121
122	/* Store ip address in cache (incomplete entry). */
123	al->addr = addr;
124
125	i = sendrecv(d,
126	    arpsend, &wbuf.data, sizeof(wbuf.data),
127	    arprecv, &rbuf.data, sizeof(rbuf.data));
128	if (i == -1) {
129		panic("arp: no response for %s\n",
130			  inet_ntoa(addr));
131	}
132
133	/* Store ethernet address in cache */
134	ah = &rbuf.data.arp;
135#ifdef ARP_DEBUG
136 	if (debug) {
137		printf("arp: response from %s\n",
138		    ether_sprintf(rbuf.eh.ether_shost));
139		printf("arp: cacheing %s --> %s\n",
140		    inet_ntoa(addr), ether_sprintf(ah->arp_sha));
141	}
142#endif
143	MACPY(ah->arp_sha, al->ea);
144	++arp_num;
145
146	return (al->ea);
147}
148
149static ssize_t
150arpsend(d, pkt, len)
151	struct iodesc *d;
152	void *pkt;
153	size_t len;
154{
155
156#ifdef ARP_DEBUG
157 	if (debug)
158		printf("arpsend: called\n");
159#endif
160
161	return (sendether(d, pkt, len, bcea, ETHERTYPE_ARP));
162}
163
164/*
165 * Returns 0 if this is the packet we're waiting for
166 * else -1 (and errno == 0)
167 */
168static ssize_t
169arprecv(d, pkt, len, tleft)
170	struct iodesc *d;
171	void *pkt;
172	size_t len;
173	time_t tleft;
174{
175	ssize_t n;
176	struct ether_arp *ah;
177	u_int16_t etype;	/* host order */
178
179#ifdef ARP_DEBUG
180 	if (debug)
181		printf("arprecv: ");
182#endif
183
184	n = readether(d, pkt, len, tleft, &etype);
185	errno = 0;	/* XXX */
186	if (n == -1 || n < sizeof(struct ether_arp)) {
187#ifdef ARP_DEBUG
188		if (debug)
189			printf("bad len=%d\n", n);
190#endif
191		return (-1);
192	}
193
194	if (etype != ETHERTYPE_ARP) {
195#ifdef ARP_DEBUG
196		if (debug)
197			printf("not arp type=%d\n", etype);
198#endif
199		return (-1);
200	}
201
202	/* Ethernet address now checked in readether() */
203
204	ah = (struct ether_arp *)pkt;
205	if (ah->arp_hrd != htons(ARPHRD_ETHER) ||
206	    ah->arp_pro != htons(ETHERTYPE_IP) ||
207	    ah->arp_hln != sizeof(ah->arp_sha) ||
208	    ah->arp_pln != sizeof(ah->arp_spa) )
209	{
210#ifdef ARP_DEBUG
211		if (debug)
212			printf("bad hrd/pro/hln/pln\n");
213#endif
214		return (-1);
215	}
216
217	if (ah->arp_op == htons(ARPOP_REQUEST)) {
218#ifdef ARP_DEBUG
219		if (debug)
220			printf("is request\n");
221#endif
222		arp_reply(d, ah);
223		return (-1);
224	}
225
226	if (ah->arp_op != htons(ARPOP_REPLY)) {
227#ifdef ARP_DEBUG
228		if (debug)
229			printf("not ARP reply\n");
230#endif
231		return (-1);
232	}
233
234	/* Is the reply from the source we want? */
235	if (bcmp(&arp_list[arp_num].addr,
236			 ah->arp_spa, sizeof(ah->arp_spa)))
237	{
238#ifdef ARP_DEBUG
239		if (debug)
240			printf("unwanted address\n");
241#endif
242		return (-1);
243	}
244	/* We don't care who the reply was sent to. */
245
246	/* We have our answer. */
247#ifdef ARP_DEBUG
248 	if (debug)
249		printf("got it\n");
250#endif
251	return (n);
252}
253
254/*
255 * Convert an ARP request into a reply and send it.
256 * Notes:  Re-uses buffer.  Pad to length = 46.
257 */
258void
259arp_reply(d, pkt)
260	struct iodesc *d;
261	void *pkt;		/* the request */
262{
263	struct ether_arp *arp = pkt;
264
265	if (arp->arp_hrd != htons(ARPHRD_ETHER) ||
266	    arp->arp_pro != htons(ETHERTYPE_IP) ||
267	    arp->arp_hln != sizeof(arp->arp_sha) ||
268	    arp->arp_pln != sizeof(arp->arp_spa) )
269	{
270#ifdef ARP_DEBUG
271		if (debug)
272			printf("arp_reply: bad hrd/pro/hln/pln\n");
273#endif
274		return;
275	}
276
277	if (arp->arp_op != htons(ARPOP_REQUEST)) {
278#ifdef ARP_DEBUG
279		if (debug)
280			printf("arp_reply: not request!\n");
281#endif
282		return;
283	}
284
285	/* If we are not the target, ignore the request. */
286	if (bcmp(arp->arp_tpa, &d->myip, sizeof(arp->arp_tpa)))
287		return;
288
289#ifdef ARP_DEBUG
290	if (debug) {
291		printf("arp_reply: to %s\n", ether_sprintf(arp->arp_sha));
292	}
293#endif
294
295	arp->arp_op = htons(ARPOP_REPLY);
296	/* source becomes target */
297	bcopy(arp->arp_sha, arp->arp_tha, sizeof(arp->arp_tha));
298	bcopy(arp->arp_spa, arp->arp_tpa, sizeof(arp->arp_tpa));
299	/* here becomes source */
300	bcopy(d->myea,  arp->arp_sha, sizeof(arp->arp_sha));
301	bcopy(&d->myip, arp->arp_spa, sizeof(arp->arp_spa));
302
303	/*
304	 * No need to get fancy here.  If the send fails, the
305	 * requestor will just ask again.
306	 */
307	(void) sendether(d, pkt, sizeof(*arp) + 18,
308	                 arp->arp_tha, ETHERTYPE_ARP);
309}
310