1 /* $NetBSD: arp.c,v 1.22 2001/10/18 19:00:38 jdolecek 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\n", 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 || 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 } 335