1 /* $OpenBSD: arp.c,v 1.7 1999/01/11 05:12:25 millert 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 __P((struct iodesc *, void *, size_t)); 68 static ssize_t arprecv __P((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 register struct iodesc *d; 74 struct in_addr addr; 75 { 76 register int i; 77 register struct ether_arp *ah; 78 register 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", inet_ntoa(addr)); 130 } 131 132 /* Store ethernet address in cache */ 133 ah = &rbuf.data.arp; 134 #ifdef ARP_DEBUG 135 if (debug) { 136 printf("arp: response from %s\n", 137 ether_sprintf(rbuf.eh.ether_shost)); 138 printf("arp: cacheing %s --> %s\n", 139 inet_ntoa(addr), ether_sprintf(ah->arp_sha)); 140 } 141 #endif 142 MACPY(ah->arp_sha, al->ea); 143 ++arp_num; 144 145 return (al->ea); 146 } 147 148 static ssize_t 149 arpsend(d, pkt, len) 150 register struct iodesc *d; 151 register void *pkt; 152 register size_t len; 153 { 154 155 #ifdef ARP_DEBUG 156 if (debug) 157 printf("arpsend: called\n"); 158 #endif 159 160 return (sendether(d, pkt, len, bcea, ETHERTYPE_ARP)); 161 } 162 163 /* 164 * Returns 0 if this is the packet we're waiting for 165 * else -1 (and errno == 0) 166 */ 167 static ssize_t 168 arprecv(d, pkt, len, tleft) 169 register struct iodesc *d; 170 register void *pkt; 171 register size_t len; 172 time_t tleft; 173 { 174 register ssize_t n; 175 register struct ether_arp *ah; 176 u_int16_t etype; /* host order */ 177 178 #ifdef ARP_DEBUG 179 if (debug) 180 printf("arprecv: "); 181 #endif 182 183 n = readether(d, pkt, len, tleft, &etype); 184 errno = 0; /* XXX */ 185 if (n < 0 || (size_t)n < sizeof(struct ether_arp)) { 186 #ifdef ARP_DEBUG 187 if (debug) 188 printf("bad len=%d\n", n); 189 #endif 190 return (-1); 191 } 192 193 if (etype != ETHERTYPE_ARP) { 194 #ifdef ARP_DEBUG 195 if (debug) 196 printf("not arp type=%d\n", etype); 197 #endif 198 return (-1); 199 } 200 201 /* Ethernet address now checked in readether() */ 202 203 ah = (struct ether_arp *)pkt; 204 if (ah->arp_hrd != htons(ARPHRD_ETHER) || 205 ah->arp_pro != htons(ETHERTYPE_IP) || 206 ah->arp_hln != sizeof(ah->arp_sha) || 207 ah->arp_pln != sizeof(ah->arp_spa) ) 208 { 209 #ifdef ARP_DEBUG 210 if (debug) 211 printf("bad hrd/pro/hln/pln\n"); 212 #endif 213 return (-1); 214 } 215 216 if (ah->arp_op == htons(ARPOP_REQUEST)) { 217 #ifdef ARP_DEBUG 218 if (debug) 219 printf("is request\n"); 220 #endif 221 arp_reply(d, ah); 222 return (-1); 223 } 224 225 if (ah->arp_op != htons(ARPOP_REPLY)) { 226 #ifdef ARP_DEBUG 227 if (debug) 228 printf("not ARP reply\n"); 229 #endif 230 return (-1); 231 } 232 233 /* Is the reply from the source we want? */ 234 if (bcmp(&arp_list[arp_num].addr, 235 ah->arp_spa, sizeof(ah->arp_spa))) 236 { 237 #ifdef ARP_DEBUG 238 if (debug) 239 printf("unwanted address\n"); 240 #endif 241 return (-1); 242 } 243 /* We don't care who the reply was sent to. */ 244 245 /* We have our answer. */ 246 #ifdef ARP_DEBUG 247 if (debug) 248 printf("got it\n"); 249 #endif 250 return (n); 251 } 252 253 /* 254 * Convert an ARP request into a reply and send it. 255 * Notes: Re-uses buffer. Pad to length = 46. 256 */ 257 void 258 arp_reply(d, pkt) 259 register struct iodesc *d; 260 register void *pkt; /* the request */ 261 { 262 struct ether_arp *arp = pkt; 263 264 if (arp->arp_hrd != htons(ARPHRD_ETHER) || 265 arp->arp_pro != htons(ETHERTYPE_IP) || 266 arp->arp_hln != sizeof(arp->arp_sha) || 267 arp->arp_pln != sizeof(arp->arp_spa) ) 268 { 269 #ifdef ARP_DEBUG 270 if (debug) 271 printf("arp_reply: bad hrd/pro/hln/pln\n"); 272 #endif 273 return; 274 } 275 276 if (arp->arp_op != htons(ARPOP_REQUEST)) { 277 #ifdef ARP_DEBUG 278 if (debug) 279 printf("arp_reply: not request!\n"); 280 #endif 281 return; 282 } 283 284 /* If we are not the target, ignore the request. */ 285 if (bcmp(arp->arp_tpa, &d->myip, sizeof(arp->arp_tpa))) 286 return; 287 288 #ifdef ARP_DEBUG 289 if (debug) { 290 printf("arp_reply: to %s\n", ether_sprintf(arp->arp_sha)); 291 } 292 #endif 293 294 arp->arp_op = htons(ARPOP_REPLY); 295 /* source becomes target */ 296 bcopy(arp->arp_sha, arp->arp_tha, sizeof(arp->arp_tha)); 297 bcopy(arp->arp_spa, arp->arp_tpa, sizeof(arp->arp_tpa)); 298 /* here becomes source */ 299 bcopy(d->myea, arp->arp_sha, sizeof(arp->arp_sha)); 300 bcopy(&d->myip, arp->arp_spa, sizeof(arp->arp_spa)); 301 302 /* 303 * No need to get fancy here. If the send fails, the 304 * requestor will just ask again. 305 */ 306 (void) sendether(d, pkt, sizeof(*arp) + 18, 307 arp->arp_tha, ETHERTYPE_ARP); 308 } 309