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 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(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 } 148 149 static ssize_t 150 arpsend(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 */ 168 static ssize_t 169 arprecv(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 */ 258 void 259 arp_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