arp.c revision 1.7
1 /* $NetBSD: arp.c,v 1.7 1995/09/11 21:11:36 thorpej 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 static struct arp_list { 59 n_long addr; 60 u_char ea[6]; 61 } arp_list[ARP_NUM] = { 62 { INADDR_BROADCAST, BA } 63 }; 64 static int arp_num = 1; 65 66 /* Local forwards */ 67 static size_t arpsend __P((struct iodesc *, void *, size_t)); 68 static size_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 n_long addr; 75 { 76 register int i; 77 register struct ether_arp *ah; 78 register struct arp_list *al; 79 struct { 80 u_char header[ETHER_SIZE]; 81 struct { 82 struct ether_arp arp; 83 u_char pad[18]; /* 60 - sizeof(arp) */ 84 } data; 85 } wbuf; 86 struct { 87 u_char header[ETHER_SIZE]; 88 struct { 89 struct ether_arp arp; 90 u_char pad[24]; /* extra space */ 91 } data; 92 } rbuf; 93 94 #ifdef ARP_DEBUG 95 if (debug) 96 printf("arpwhohas: called for %s\n", intoa(addr)); 97 #endif 98 /* Try for cached answer first */ 99 for (i = 0, al = arp_list; i < arp_num; ++i, ++al) 100 if (addr == al->addr) 101 return (al->ea); 102 103 /* Don't overflow cache */ 104 if (arp_num > ARP_NUM - 1) 105 panic("arpwhohas: overflowed arp_list!"); 106 107 #ifdef ARP_DEBUG 108 if (debug) 109 printf("arpwhohas: not cached\n"); 110 #endif 111 112 bzero((char*)&wbuf.data, sizeof(wbuf.data)); 113 ah = &wbuf.data.arp; 114 ah->arp_hrd = htons(ARPHRD_ETHER); 115 ah->arp_pro = htons(ETHERTYPE_IP); 116 ah->arp_hln = sizeof(ah->arp_sha); /* hardware address length */ 117 ah->arp_pln = sizeof(ah->arp_spa); /* protocol address length */ 118 ah->arp_op = htons(ARPOP_REQUEST); 119 MACPY(d->myea, ah->arp_sha); 120 bcopy(&d->myip, ah->arp_spa, sizeof(ah->arp_spa)); 121 bcopy(&addr, ah->arp_tpa, sizeof(ah->arp_tpa)); 122 123 /* Store ip address in cache */ 124 al->addr = addr; 125 126 (void)sendrecv(d, 127 arpsend, &wbuf.data, sizeof(wbuf.data), 128 arprecv, &rbuf.data, sizeof(rbuf.data)); 129 130 /* Store ethernet address in cache */ 131 MACPY(rbuf.data.arp.arp_sha, al->ea); 132 ++arp_num; 133 134 return (al->ea); 135 } 136 137 static size_t 138 arpsend(d, pkt, len) 139 register struct iodesc *d; 140 register void *pkt; 141 register size_t len; 142 { 143 144 #ifdef ARP_DEBUG 145 if (debug) 146 printf("arpsend: called\n"); 147 #endif 148 149 return (sendether(d, pkt, len, bcea, ETHERTYPE_ARP)); 150 } 151 152 /* Returns 0 if this is the packet we're waiting for else -1 (and errno == 0) */ 153 static size_t 154 arprecv(d, pkt, len, tleft) 155 register struct iodesc *d; 156 register void *pkt; 157 register size_t len; 158 time_t tleft; 159 { 160 register struct ether_arp *ah; 161 u_int16_t etype; /* host order */ 162 163 #ifdef ARP_DEBUG 164 if (debug) 165 printf("arprecv: "); 166 #endif 167 168 len = readether(d, pkt, len, tleft, &etype); 169 if (len == -1 || len < sizeof(struct ether_arp)) { 170 #ifdef ARP_DEBUG 171 if (debug) 172 printf("bad len=%d\n", len); 173 #endif 174 goto bad; 175 } 176 177 if (etype != ETHERTYPE_ARP) { 178 #ifdef ARP_DEBUG 179 if (debug) 180 printf("not arp type=%d\n", etype); 181 #endif 182 goto bad; 183 } 184 185 /* Ethernet address now checked in readether() */ 186 187 ah = (struct ether_arp *)pkt; 188 if (ah->arp_hrd != htons(ARPHRD_ETHER) || 189 ah->arp_pro != htons(ETHERTYPE_IP) || 190 ah->arp_hln != sizeof(ah->arp_sha) || 191 ah->arp_pln != sizeof(ah->arp_spa) ) 192 { 193 #ifdef ARP_DEBUG 194 if (debug) 195 printf("bad hrd/pro/hln/pln\n") 196 #endif 197 goto bad; 198 } 199 200 if (ah->arp_op == htons(ARPOP_REQUEST)) { 201 arp_reply(d, ah); 202 goto bad; 203 } 204 205 if (ah->arp_op != htons(ARPOP_REPLY)) { 206 #ifdef ARP_DEBUG 207 if (debug) 208 printf("not ARP reply\n"); 209 #endif 210 goto bad; 211 } 212 213 if (bcmp(&arp_list[arp_num].addr, ah->arp_spa, sizeof(long)) != 0 || 214 bcmp(&d->myip, ah->arp_tpa, sizeof(d->myip)) != 0) { 215 #ifdef ARP_DEBUG 216 if (debug) 217 printf("already cached??\n"); 218 #endif 219 goto bad; 220 } 221 222 #ifdef ARP_DEBUG 223 if (debug) 224 printf("cacheing %s --> %s\n", 225 intoa(ah->arp_spa), 226 ether_sprintf(ah->arp_sha)); 227 #endif 228 return (0); 229 230 bad: 231 errno = 0; 232 return (-1); 233 } 234 235 /* 236 * Convert an ARP request into a reply and send it. 237 * Notes: Re-uses buffer. Min send length = 60. 238 */ 239 void 240 arp_reply(d, pkt) 241 register struct iodesc *d; 242 register void *pkt; /* the request */ 243 { 244 struct ether_arp *arp = pkt; 245 246 if (arp->arp_hrd != htons(ARPHRD_ETHER) || 247 arp->arp_pro != htons(ETHERTYPE_IP) || 248 arp->arp_hln != sizeof(arp->arp_sha) || 249 arp->arp_pln != sizeof(arp->arp_spa) ) 250 { 251 #ifdef ARP_DEBUG 252 if (debug) 253 printf("arp_reply: bad hrd/pro/hln/pln\n") 254 #endif 255 return; 256 } 257 258 if (arp->arp_op != htons(ARPOP_REQUEST)) { 259 #ifdef ARP_DEBUG 260 if (debug) 261 printf("arp_reply: not request!\n"); 262 #endif 263 return; 264 } 265 266 /* If we are not the target, ignore the request. */ 267 if (bcmp(arp->arp_tpa, &d->myip, sizeof(arp->arp_tpa))) 268 return; 269 270 #ifdef ARP_DEBUG 271 if (debug) { 272 printf("arp_reply: to %s\n", 273 ether_sprintf(arp->arp_sha)); 274 } 275 #endif 276 277 arp->arp_op = htons(ARPOP_REPLY); 278 /* source becomes target */ 279 bcopy(arp->arp_sha, arp->arp_tha, sizeof(arp->arp_tha)); 280 bcopy(arp->arp_spa, arp->arp_tpa, sizeof(arp->arp_tpa)); 281 /* here becomes source */ 282 bcopy(d->myea, arp->arp_sha, sizeof(arp->arp_sha)); 283 bcopy(&d->myip, arp->arp_spa, sizeof(arp->arp_spa)); 284 285 /* 286 * No need to get fancy here. If the send fails, the 287 * requestor will just ask again. 288 */ 289 (void) sendether(d, pkt, 60, arp->arp_tha, ETHERTYPE_ARP); 290 } 291
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