1 /* $NetBSD: arp.c,v 1.13 1995/12/08 04:12:53 gwr 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), 142 ether_sprintf(ah->arp_sha)); 143 } 144 #endif 145 MACPY(ah->arp_sha, al->ea); 146 ++arp_num; 147 148 return (al->ea); 149 } 150 151 static ssize_t 152 arpsend(d, pkt, len) 153 register struct iodesc *d; 154 register void *pkt; 155 register size_t len; 156 { 157 158 #ifdef ARP_DEBUG 159 if (debug) 160 printf("arpsend: called\n"); 161 #endif 162 163 return (sendether(d, pkt, len, bcea, ETHERTYPE_ARP)); 164 } 165 166 /* 167 * Returns 0 if this is the packet we're waiting for 168 * else -1 (and errno == 0) 169 */ 170 static ssize_t 171 arprecv(d, pkt, len, tleft) 172 register struct iodesc *d; 173 register void *pkt; 174 register size_t len; 175 time_t tleft; 176 { 177 register ssize_t n; 178 register struct ether_arp *ah; 179 u_int16_t etype; /* host order */ 180 181 #ifdef ARP_DEBUG 182 if (debug) 183 printf("arprecv: "); 184 #endif 185 186 n = readether(d, pkt, len, tleft, &etype); 187 errno = 0; /* XXX */ 188 if (n == -1 || n < sizeof(struct ether_arp)) { 189 #ifdef ARP_DEBUG 190 if (debug) 191 printf("bad len=%d\n", n); 192 #endif 193 return (-1); 194 } 195 196 if (etype != ETHERTYPE_ARP) { 197 #ifdef ARP_DEBUG 198 if (debug) 199 printf("not arp type=%d\n", etype); 200 #endif 201 return (-1); 202 } 203 204 /* Ethernet address now checked in readether() */ 205 206 ah = (struct ether_arp *)pkt; 207 if (ah->arp_hrd != htons(ARPHRD_ETHER) || 208 ah->arp_pro != htons(ETHERTYPE_IP) || 209 ah->arp_hln != sizeof(ah->arp_sha) || 210 ah->arp_pln != sizeof(ah->arp_spa) ) 211 { 212 #ifdef ARP_DEBUG 213 if (debug) 214 printf("bad hrd/pro/hln/pln\n"); 215 #endif 216 return (-1); 217 } 218 219 if (ah->arp_op == htons(ARPOP_REQUEST)) { 220 #ifdef ARP_DEBUG 221 if (debug) 222 printf("is request\n"); 223 #endif 224 arp_reply(d, ah); 225 return (-1); 226 } 227 228 if (ah->arp_op != htons(ARPOP_REPLY)) { 229 #ifdef ARP_DEBUG 230 if (debug) 231 printf("not ARP reply\n"); 232 #endif 233 return (-1); 234 } 235 236 /* Is the reply from the source we want? */ 237 if (bcmp(&arp_list[arp_num].addr, 238 ah->arp_spa, sizeof(ah->arp_spa))) 239 { 240 #ifdef ARP_DEBUG 241 if (debug) 242 printf("unwanted address\n"); 243 #endif 244 return (-1); 245 } 246 /* We don't care who the reply was sent to. */ 247 248 /* We have our answer. */ 249 #ifdef ARP_DEBUG 250 if (debug) 251 printf("got it\n"); 252 #endif 253 return (n); 254 } 255 256 /* 257 * Convert an ARP request into a reply and send it. 258 * Notes: Re-uses buffer. Pad to length = 46. 259 */ 260 void 261 arp_reply(d, pkt) 262 register struct iodesc *d; 263 register void *pkt; /* the request */ 264 { 265 struct ether_arp *arp = pkt; 266 267 if (arp->arp_hrd != htons(ARPHRD_ETHER) || 268 arp->arp_pro != htons(ETHERTYPE_IP) || 269 arp->arp_hln != sizeof(arp->arp_sha) || 270 arp->arp_pln != sizeof(arp->arp_spa) ) 271 { 272 #ifdef ARP_DEBUG 273 if (debug) 274 printf("arp_reply: bad hrd/pro/hln/pln\n"); 275 #endif 276 return; 277 } 278 279 if (arp->arp_op != htons(ARPOP_REQUEST)) { 280 #ifdef ARP_DEBUG 281 if (debug) 282 printf("arp_reply: not request!\n"); 283 #endif 284 return; 285 } 286 287 /* If we are not the target, ignore the request. */ 288 if (bcmp(arp->arp_tpa, &d->myip, sizeof(arp->arp_tpa))) 289 return; 290 291 #ifdef ARP_DEBUG 292 if (debug) { 293 printf("arp_reply: to %s\n", 294 ether_sprintf(arp->arp_sha)); 295 } 296 #endif 297 298 arp->arp_op = htons(ARPOP_REPLY); 299 /* source becomes target */ 300 bcopy(arp->arp_sha, arp->arp_tha, sizeof(arp->arp_tha)); 301 bcopy(arp->arp_spa, arp->arp_tpa, sizeof(arp->arp_tpa)); 302 /* here becomes source */ 303 bcopy(d->myea, arp->arp_sha, sizeof(arp->arp_sha)); 304 bcopy(&d->myip, arp->arp_spa, sizeof(arp->arp_spa)); 305 306 /* 307 * No need to get fancy here. If the send fails, the 308 * requestor will just ask again. 309 */ 310 (void) sendether(d, pkt, sizeof(*arp) + 18, 311 arp->arp_tha, ETHERTYPE_ARP); 312 } 313