1 /* $NetBSD: arp.c,v 1.33 2009/01/17 14:00:36 tsutsui 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(struct iodesc *, void *, size_t); 93 static ssize_t arprecv(struct iodesc *, void *, size_t, saseconds_t); 94 95 /* Broadcast an ARP packet, asking who has addr on interface d */ 96 u_char * 97 arpwhohas(struct iodesc *d, struct in_addr addr) 98 { 99 int i; 100 struct ether_arp *ah; 101 struct arp_list *al; 102 struct { 103 struct ether_header eh; 104 struct { 105 struct ether_arp arp; 106 u_char pad[18]; /* 60 - sizeof(...) */ 107 } data; 108 } wbuf; 109 struct { 110 struct ether_header eh; 111 struct { 112 struct ether_arp arp; 113 u_char pad[24]; /* extra space */ 114 } data; 115 } rbuf; 116 117 /* Try for cached answer first */ 118 for (i = 0, al = arp_list; i < arp_num; ++i, ++al) 119 if (addr.s_addr == al->addr.s_addr) 120 return al->ea; 121 122 /* Don't overflow cache */ 123 if (arp_num > ARP_NUM - 1) { 124 arp_num = 1; /* recycle */ 125 printf("arpwhohas: overflowed arp_list!\n"); 126 } 127 128 #ifdef ARP_DEBUG 129 if (debug) 130 printf("arpwhohas: send request for %s\n", inet_ntoa(addr)); 131 #endif 132 133 (void)memset(&wbuf.data, 0, sizeof(wbuf.data)); 134 ah = &wbuf.data.arp; 135 ah->arp_hrd = htons(ARPHRD_ETHER); 136 ah->arp_pro = htons(ETHERTYPE_IP); 137 ah->arp_hln = sizeof(ah->arp_sha); /* hardware address length */ 138 ah->arp_pln = sizeof(ah->arp_spa); /* protocol address length */ 139 ah->arp_op = htons(ARPOP_REQUEST); 140 MACPY(d->myea, ah->arp_sha); 141 (void)memcpy(ah->arp_spa, &d->myip, sizeof(ah->arp_spa)); 142 /* Leave zeros in arp_tha */ 143 (void)memcpy(ah->arp_tpa, &addr, sizeof(ah->arp_tpa)); 144 145 /* Store ip address in cache (incomplete entry). */ 146 al->addr = addr; 147 148 i = sendrecv(d, 149 arpsend, &wbuf.data, sizeof(wbuf.data), 150 arprecv, &rbuf.data, sizeof(rbuf.data)); 151 if (i == -1) { 152 panic("arp: no response for %s", 153 inet_ntoa(addr)); 154 } 155 156 /* Store ethernet address in cache */ 157 ah = &rbuf.data.arp; 158 #ifdef ARP_DEBUG 159 if (debug) { 160 printf("arp: response from %s\n", 161 ether_sprintf(rbuf.eh.ether_shost)); 162 printf("arp: cacheing %s --> %s\n", 163 inet_ntoa(addr), ether_sprintf(ah->arp_sha)); 164 } 165 #endif 166 MACPY(ah->arp_sha, al->ea); 167 ++arp_num; 168 169 return al->ea; 170 } 171 172 static ssize_t 173 arpsend(struct iodesc *d, void *pkt, size_t len) 174 { 175 176 #ifdef ARP_DEBUG 177 if (debug) 178 printf("arpsend: called\n"); 179 #endif 180 181 return sendether(d, pkt, len, bcea, ETHERTYPE_ARP); 182 } 183 184 /* 185 * Returns 0 if this is the packet we're waiting for 186 * else -1 (and errno == 0) 187 */ 188 static ssize_t 189 arprecv(struct iodesc *d, void *pkt, size_t len, saseconds_t tleft) 190 { 191 ssize_t n; 192 struct ether_arp *ah; 193 u_int16_t etype; /* host order */ 194 195 #ifdef ARP_DEBUG 196 if (debug) 197 printf("arprecv: "); 198 #endif 199 200 n = readether(d, pkt, len, tleft, &etype); 201 errno = 0; /* XXX */ 202 if (n == -1 || (size_t)n < sizeof(struct ether_arp)) { 203 #ifdef ARP_DEBUG 204 if (debug) 205 printf("bad len=%ld\n", (signed long) n); 206 #endif 207 return -1; 208 } 209 210 if (etype != ETHERTYPE_ARP) { 211 #ifdef ARP_DEBUG 212 if (debug) 213 printf("not arp type=%d\n", etype); 214 #endif 215 return -1; 216 } 217 218 /* Ethernet address now checked in readether() */ 219 220 ah = (struct ether_arp *)pkt; 221 if (ah->arp_hrd != htons(ARPHRD_ETHER) || 222 ah->arp_pro != htons(ETHERTYPE_IP) || 223 ah->arp_hln != sizeof(ah->arp_sha) || 224 ah->arp_pln != sizeof(ah->arp_spa) ) 225 { 226 #ifdef ARP_DEBUG 227 if (debug) 228 printf("bad hrd/pro/hln/pln\n"); 229 #endif 230 return -1; 231 } 232 233 if (ah->arp_op == htons(ARPOP_REQUEST)) { 234 #ifdef ARP_DEBUG 235 if (debug) 236 printf("is request\n"); 237 #endif 238 arp_reply(d, ah); 239 return -1; 240 } 241 242 if (ah->arp_op != htons(ARPOP_REPLY)) { 243 #ifdef ARP_DEBUG 244 if (debug) 245 printf("not ARP reply\n"); 246 #endif 247 return -1; 248 } 249 250 /* Is the reply from the source we want? */ 251 if (memcmp(&arp_list[arp_num].addr, 252 ah->arp_spa, sizeof(ah->arp_spa))) 253 { 254 #ifdef ARP_DEBUG 255 if (debug) 256 printf("unwanted address\n"); 257 #endif 258 return -1; 259 } 260 /* We don't care who the reply was sent to. */ 261 262 /* We have our answer. */ 263 #ifdef ARP_DEBUG 264 if (debug) 265 printf("got it\n"); 266 #endif 267 return n; 268 } 269 270 /* 271 * Convert an ARP request into a reply and send it. 272 * Notes: Re-uses buffer. Pad to length = 46. 273 */ 274 void 275 arp_reply(struct iodesc *d, void *pkt) 276 { 277 struct ether_arp *arp = pkt; 278 279 if (arp->arp_hrd != htons(ARPHRD_ETHER) || 280 arp->arp_pro != htons(ETHERTYPE_IP) || 281 arp->arp_hln != sizeof(arp->arp_sha) || 282 arp->arp_pln != sizeof(arp->arp_spa) ) 283 { 284 #ifdef ARP_DEBUG 285 if (debug) 286 printf("arp_reply: bad hrd/pro/hln/pln\n"); 287 #endif 288 return; 289 } 290 291 if (arp->arp_op != htons(ARPOP_REQUEST)) { 292 #ifdef ARP_DEBUG 293 if (debug) 294 printf("arp_reply: not request!\n"); 295 #endif 296 return; 297 } 298 299 /* If we are not the target, ignore the request. */ 300 if (memcmp(arp->arp_tpa, &d->myip, sizeof(arp->arp_tpa))) 301 return; 302 303 #ifdef ARP_DEBUG 304 if (debug) { 305 printf("arp_reply: to %s\n", ether_sprintf(arp->arp_sha)); 306 } 307 #endif 308 309 arp->arp_op = htons(ARPOP_REPLY); 310 /* source becomes target */ 311 (void)memcpy(arp->arp_tha, arp->arp_sha, sizeof(arp->arp_tha)); 312 (void)memcpy(arp->arp_tpa, arp->arp_spa, sizeof(arp->arp_tpa)); 313 /* here becomes source */ 314 (void)memcpy(arp->arp_sha, d->myea, sizeof(arp->arp_sha)); 315 (void)memcpy(arp->arp_spa, &d->myip, sizeof(arp->arp_spa)); 316 317 /* 318 * No need to get fancy here. If the send fails, the 319 * requestor will just ask again. 320 */ 321 (void) sendether(d, pkt, sizeof(*arp) + 18, 322 arp->arp_tha, ETHERTYPE_ARP); 323 } 324