1 /* $NetBSD: arp.c,v 1.15 1996/10/13 02:28:58 christos 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 <netinet/in.h> 46 47 #include <netinet/if_ether.h> 48 #include <netinet/in_systm.h> 49 50 #include <string.h> 51 52 #include "stand.h" 53 #include "net.h" 54 55 /* Cache stuff */ 56 #define ARP_NUM 8 /* need at most 3 arp entries */ 57 58 struct arp_list { 59 struct in_addr addr; 60 u_char ea[6]; 61 } arp_list[ARP_NUM] = { 62 /* XXX - net order `INADDR_BROADCAST' must be a constant */ 63 { {0xffffffff}, BA } 64 }; 65 int arp_num = 1; 66 67 /* Local forwards */ 68 static ssize_t arpsend __P((struct iodesc *, void *, size_t)); 69 static ssize_t arprecv __P((struct iodesc *, void *, size_t, time_t)); 70 71 /* Broadcast an ARP packet, asking who has addr on interface d */ 72 u_char * 73 arpwhohas(d, addr) 74 register struct iodesc *d; 75 struct in_addr addr; 76 { 77 register int i; 78 register struct ether_arp *ah; 79 register struct arp_list *al; 80 struct { 81 struct ether_header eh; 82 struct { 83 struct ether_arp arp; 84 u_char pad[18]; /* 60 - sizeof(...) */ 85 } data; 86 } wbuf; 87 struct { 88 struct ether_header eh; 89 struct { 90 struct ether_arp arp; 91 u_char pad[24]; /* extra space */ 92 } data; 93 } rbuf; 94 95 /* Try for cached answer first */ 96 for (i = 0, al = arp_list; i < arp_num; ++i, ++al) 97 if (addr.s_addr == al->addr.s_addr) 98 return (al->ea); 99 100 /* Don't overflow cache */ 101 if (arp_num > ARP_NUM - 1) { 102 arp_num = 1; /* recycle */ 103 printf("arpwhohas: overflowed arp_list!\n"); 104 } 105 106 #ifdef ARP_DEBUG 107 if (debug) 108 printf("arpwhohas: send request for %s\n", inet_ntoa(addr)); 109 #endif 110 111 bzero((char*)&wbuf.data, sizeof(wbuf.data)); 112 ah = &wbuf.data.arp; 113 ah->arp_hrd = htons(ARPHRD_ETHER); 114 ah->arp_pro = htons(ETHERTYPE_IP); 115 ah->arp_hln = sizeof(ah->arp_sha); /* hardware address length */ 116 ah->arp_pln = sizeof(ah->arp_spa); /* protocol address length */ 117 ah->arp_op = htons(ARPOP_REQUEST); 118 MACPY(d->myea, ah->arp_sha); 119 bcopy(&d->myip, ah->arp_spa, sizeof(ah->arp_spa)); 120 /* Leave zeros in arp_tha */ 121 bcopy(&addr, ah->arp_tpa, sizeof(ah->arp_tpa)); 122 123 /* Store ip address in cache (incomplete entry). */ 124 al->addr = addr; 125 126 i = sendrecv(d, 127 arpsend, &wbuf.data, sizeof(wbuf.data), 128 arprecv, &rbuf.data, sizeof(rbuf.data)); 129 if (i == -1) { 130 panic("arp: no response for %s\n", 131 inet_ntoa(addr)); 132 } 133 134 /* Store ethernet address in cache */ 135 ah = &rbuf.data.arp; 136 #ifdef ARP_DEBUG 137 if (debug) { 138 printf("arp: response from %s\n", 139 ether_sprintf(rbuf.eh.ether_shost)); 140 printf("arp: cacheing %s --> %s\n", 141 inet_ntoa(addr), ether_sprintf(ah->arp_sha)); 142 } 143 #endif 144 MACPY(ah->arp_sha, al->ea); 145 ++arp_num; 146 147 return (al->ea); 148 } 149 150 static ssize_t 151 arpsend(d, pkt, len) 152 register struct iodesc *d; 153 register void *pkt; 154 register size_t len; 155 { 156 157 #ifdef ARP_DEBUG 158 if (debug) 159 printf("arpsend: called\n"); 160 #endif 161 162 return (sendether(d, pkt, len, bcea, ETHERTYPE_ARP)); 163 } 164 165 /* 166 * Returns 0 if this is the packet we're waiting for 167 * else -1 (and errno == 0) 168 */ 169 static ssize_t 170 arprecv(d, pkt, len, tleft) 171 register struct iodesc *d; 172 register void *pkt; 173 register size_t len; 174 time_t tleft; 175 { 176 register ssize_t n; 177 register struct ether_arp *ah; 178 u_int16_t etype; /* host order */ 179 180 #ifdef ARP_DEBUG 181 if (debug) 182 printf("arprecv: "); 183 #endif 184 185 n = readether(d, pkt, len, tleft, &etype); 186 errno = 0; /* XXX */ 187 if (n == -1 || n < sizeof(struct ether_arp)) { 188 #ifdef ARP_DEBUG 189 if (debug) 190 printf("bad len=%d\n", n); 191 #endif 192 return (-1); 193 } 194 195 if (etype != ETHERTYPE_ARP) { 196 #ifdef ARP_DEBUG 197 if (debug) 198 printf("not arp type=%d\n", etype); 199 #endif 200 return (-1); 201 } 202 203 /* Ethernet address now checked in readether() */ 204 205 ah = (struct ether_arp *)pkt; 206 if (ah->arp_hrd != htons(ARPHRD_ETHER) || 207 ah->arp_pro != htons(ETHERTYPE_IP) || 208 ah->arp_hln != sizeof(ah->arp_sha) || 209 ah->arp_pln != sizeof(ah->arp_spa) ) 210 { 211 #ifdef ARP_DEBUG 212 if (debug) 213 printf("bad hrd/pro/hln/pln\n"); 214 #endif 215 return (-1); 216 } 217 218 if (ah->arp_op == htons(ARPOP_REQUEST)) { 219 #ifdef ARP_DEBUG 220 if (debug) 221 printf("is request\n"); 222 #endif 223 arp_reply(d, ah); 224 return (-1); 225 } 226 227 if (ah->arp_op != htons(ARPOP_REPLY)) { 228 #ifdef ARP_DEBUG 229 if (debug) 230 printf("not ARP reply\n"); 231 #endif 232 return (-1); 233 } 234 235 /* Is the reply from the source we want? */ 236 if (bcmp(&arp_list[arp_num].addr, 237 ah->arp_spa, sizeof(ah->arp_spa))) 238 { 239 #ifdef ARP_DEBUG 240 if (debug) 241 printf("unwanted address\n"); 242 #endif 243 return (-1); 244 } 245 /* We don't care who the reply was sent to. */ 246 247 /* We have our answer. */ 248 #ifdef ARP_DEBUG 249 if (debug) 250 printf("got it\n"); 251 #endif 252 return (n); 253 } 254 255 /* 256 * Convert an ARP request into a reply and send it. 257 * Notes: Re-uses buffer. Pad to length = 46. 258 */ 259 void 260 arp_reply(d, pkt) 261 register struct iodesc *d; 262 register void *pkt; /* the request */ 263 { 264 struct ether_arp *arp = pkt; 265 266 if (arp->arp_hrd != htons(ARPHRD_ETHER) || 267 arp->arp_pro != htons(ETHERTYPE_IP) || 268 arp->arp_hln != sizeof(arp->arp_sha) || 269 arp->arp_pln != sizeof(arp->arp_spa) ) 270 { 271 #ifdef ARP_DEBUG 272 if (debug) 273 printf("arp_reply: bad hrd/pro/hln/pln\n"); 274 #endif 275 return; 276 } 277 278 if (arp->arp_op != htons(ARPOP_REQUEST)) { 279 #ifdef ARP_DEBUG 280 if (debug) 281 printf("arp_reply: not request!\n"); 282 #endif 283 return; 284 } 285 286 /* If we are not the target, ignore the request. */ 287 if (bcmp(arp->arp_tpa, &d->myip, sizeof(arp->arp_tpa))) 288 return; 289 290 #ifdef ARP_DEBUG 291 if (debug) { 292 printf("arp_reply: to %s\n", ether_sprintf(arp->arp_sha)); 293 } 294 #endif 295 296 arp->arp_op = htons(ARPOP_REPLY); 297 /* source becomes target */ 298 bcopy(arp->arp_sha, arp->arp_tha, sizeof(arp->arp_tha)); 299 bcopy(arp->arp_spa, arp->arp_tpa, sizeof(arp->arp_tpa)); 300 /* here becomes source */ 301 bcopy(d->myea, arp->arp_sha, sizeof(arp->arp_sha)); 302 bcopy(&d->myip, arp->arp_spa, sizeof(arp->arp_spa)); 303 304 /* 305 * No need to get fancy here. If the send fails, the 306 * requestor will just ask again. 307 */ 308 (void) sendether(d, pkt, sizeof(*arp) + 18, 309 arp->arp_tha, ETHERTYPE_ARP); 310 } 311