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 } 295