Annotation of sys/lib/libsa/arp.c, Revision 1.1.1.1
1.1 nbrk 1: /* $OpenBSD: arp.c,v 1.11 2003/08/11 06:23:09 deraadt Exp $ */
2: /* $NetBSD: arp.c,v 1.15 1996/10/13 02:28:58 christos Exp $ */
3:
4: /*
5: * Copyright (c) 1992 Regents of the University of California.
6: * All rights reserved.
7: *
8: * This software was developed by the Computer Systems Engineering group
9: * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
10: * contributed to Berkeley.
11: *
12: * Redistribution and use in source and binary forms, with or without
13: * modification, are permitted provided that the following conditions
14: * are met:
15: * 1. Redistributions of source code must retain the above copyright
16: * notice, this list of conditions and the following disclaimer.
17: * 2. Redistributions in binary form must reproduce the above copyright
18: * notice, this list of conditions and the following disclaimer in the
19: * documentation and/or other materials provided with the distribution.
20: * 3. All advertising materials mentioning features or use of this software
21: * must display the following acknowledgement:
22: * This product includes software developed by the University of
23: * California, Lawrence Berkeley Laboratory and its contributors.
24: * 4. Neither the name of the University nor the names of its contributors
25: * may be used to endorse or promote products derived from this software
26: * without specific prior written permission.
27: *
28: * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
29: * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
30: * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
31: * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
32: * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
33: * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
34: * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
35: * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
36: * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
37: * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
38: * SUCH DAMAGE.
39: *
40: * @(#) Header: arp.c,v 1.5 93/07/15 05:52:26 leres Exp (LBL)
41: */
42:
43: #include <sys/types.h>
44: #include <sys/socket.h>
45: #include <net/if.h>
46: #include <netinet/in.h>
47:
48: #include <netinet/if_ether.h>
49: #include <netinet/in_systm.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 *, size_t, time_t);
69:
70: /* Broadcast an ARP packet, asking who has addr on interface d */
71: u_char *
72: arpwhohas(struct iodesc *d, struct in_addr addr)
73: {
74: int i;
75: struct ether_arp *ah;
76: struct arp_list *al;
77: struct {
78: struct ether_header eh;
79: struct {
80: struct ether_arp arp;
81: u_char pad[18]; /* 60 - sizeof(...) */
82: } data;
83: } wbuf;
84: struct {
85: struct ether_header eh;
86: struct {
87: struct ether_arp arp;
88: u_char pad[24]; /* extra space */
89: } data;
90: } rbuf;
91:
92: /* Try for cached answer first */
93: for (i = 0, al = arp_list; i < arp_num; ++i, ++al)
94: if (addr.s_addr == al->addr.s_addr)
95: return (al->ea);
96:
97: /* Don't overflow cache */
98: if (arp_num > ARP_NUM - 1) {
99: arp_num = 1; /* recycle */
100: printf("arpwhohas: overflowed arp_list!\n");
101: }
102:
103: #ifdef ARP_DEBUG
104: if (debug)
105: printf("arpwhohas: send request for %s\n", inet_ntoa(addr));
106: #endif
107:
108: bzero((char *)&wbuf.data, sizeof(wbuf.data));
109: ah = &wbuf.data.arp;
110: ah->arp_hrd = htons(ARPHRD_ETHER);
111: ah->arp_pro = htons(ETHERTYPE_IP);
112: ah->arp_hln = sizeof(ah->arp_sha); /* hardware address length */
113: ah->arp_pln = sizeof(ah->arp_spa); /* protocol address length */
114: ah->arp_op = htons(ARPOP_REQUEST);
115: MACPY(d->myea, ah->arp_sha);
116: bcopy(&d->myip, ah->arp_spa, sizeof(ah->arp_spa));
117: /* Leave zeros in arp_tha */
118: bcopy(&addr, ah->arp_tpa, sizeof(ah->arp_tpa));
119:
120: /* Store ip address in cache (incomplete entry). */
121: al->addr = addr;
122:
123: i = sendrecv(d,
124: arpsend, &wbuf.data, sizeof(wbuf.data),
125: arprecv, &rbuf.data, sizeof(rbuf.data));
126: if (i == -1) {
127: panic("arp: no response for %s", inet_ntoa(addr));
128: }
129:
130: /* Store ethernet address in cache */
131: ah = &rbuf.data.arp;
132: #ifdef ARP_DEBUG
133: if (debug) {
134: printf("arp: response from %s\n",
135: ether_sprintf(rbuf.eh.ether_shost));
136: printf("arp: cacheing %s --> %s\n",
137: inet_ntoa(addr), ether_sprintf(ah->arp_sha));
138: }
139: #endif
140: MACPY(ah->arp_sha, al->ea);
141: ++arp_num;
142:
143: return (al->ea);
144: }
145:
146: static ssize_t
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
163: arprecv(struct iodesc *d, void *pkt, size_t len, time_t tleft)
164: {
165: ssize_t n;
166: struct ether_arp *ah;
167: u_int16_t etype; /* host order */
168:
169: #ifdef ARP_DEBUG
170: if (debug)
171: printf("arprecv: ");
172: #endif
173:
174: n = readether(d, pkt, len, tleft, &etype);
175: errno = 0; /* XXX */
176: if (n < 0 || (size_t)n < sizeof(struct ether_arp)) {
177: #ifdef ARP_DEBUG
178: if (debug)
179: printf("bad len=%d\n", n);
180: #endif
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: return (-1);
190: }
191:
192: /* Ethernet address now checked in readether() */
193:
194: ah = (struct ether_arp *)pkt;
195: if (ah->arp_hrd != htons(ARPHRD_ETHER) ||
196: ah->arp_pro != htons(ETHERTYPE_IP) ||
197: ah->arp_hln != sizeof(ah->arp_sha) ||
198: ah->arp_pln != sizeof(ah->arp_spa)) {
199: #ifdef ARP_DEBUG
200: if (debug)
201: printf("bad hrd/pro/hln/pln\n");
202: #endif
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: 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: return (-1);
221: }
222:
223: /* Is the reply from the source we want? */
224: if (bcmp(&arp_list[arp_num].addr, ah->arp_spa,
225: sizeof(ah->arp_spa))) {
226: #ifdef ARP_DEBUG
227: if (debug)
228: printf("unwanted address\n");
229: #endif
230: return (-1);
231: }
232: /* We don't care who the reply was sent to. */
233:
234: /* We have our answer. */
235: #ifdef ARP_DEBUG
236: if (debug)
237: printf("got it\n");
238: #endif
239: return (n);
240: }
241:
242: /*
243: * Convert an ARP request into a reply and send it.
244: * Notes: Re-uses buffer. Pad to length = 46.
245: */
246: void
247: arp_reply(struct iodesc *d, void *pkt)
248: {
249: struct ether_arp *arp = pkt;
250:
251: if (arp->arp_hrd != htons(ARPHRD_ETHER) ||
252: arp->arp_pro != htons(ETHERTYPE_IP) ||
253: arp->arp_hln != sizeof(arp->arp_sha) ||
254: arp->arp_pln != sizeof(arp->arp_spa)) {
255: #ifdef ARP_DEBUG
256: if (debug)
257: printf("arp_reply: bad hrd/pro/hln/pln\n");
258: #endif
259: return;
260: }
261:
262: if (arp->arp_op != htons(ARPOP_REQUEST)) {
263: #ifdef ARP_DEBUG
264: if (debug)
265: printf("arp_reply: not request!\n");
266: #endif
267: return;
268: }
269:
270: /* If we are not the target, ignore the request. */
271: if (bcmp(arp->arp_tpa, &d->myip, sizeof(arp->arp_tpa)))
272: return;
273:
274: #ifdef ARP_DEBUG
275: if (debug) {
276: printf("arp_reply: to %s\n", ether_sprintf(arp->arp_sha));
277: }
278: #endif
279:
280: arp->arp_op = htons(ARPOP_REPLY);
281: /* source becomes target */
282: bcopy(arp->arp_sha, arp->arp_tha, sizeof(arp->arp_tha));
283: bcopy(arp->arp_spa, arp->arp_tpa, sizeof(arp->arp_tpa));
284: /* here becomes source */
285: bcopy(d->myea, arp->arp_sha, sizeof(arp->arp_sha));
286: bcopy(&d->myip, arp->arp_spa, sizeof(arp->arp_spa));
287:
288: /*
289: * No need to get fancy here. If the send fails, the
290: * requestor will just ask again.
291: */
292: (void) sendether(d, pkt, sizeof(*arp) + 18,
293: arp->arp_tha, ETHERTYPE_ARP);
294: }
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