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 * 3. 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 36 #include <sys/types.h> 37 #include <sys/socket.h> 38 #include <net/if.h> 39 #include <netinet/in.h> 40 #include <netinet/if_ether.h> 41 42 #include <netinet/in_systm.h> 43 44 #include <string.h> 45 46 #include "stand.h" 47 #include "net.h" 48 49 /* Cache stuff */ 50 #define ARP_NUM 8 /* need at most 3 arp entries */ 51 52 struct arp_list { 53 struct in_addr addr; 54 u_char ea[6]; 55 } arp_list[ARP_NUM] = { 56 /* XXX - net order `INADDR_BROADCAST' must be a constant */ 57 { {0xffffffff}, BA } 58 }; 59 int arp_num = 1; 60 61 /* Local forwards */ 62 static ssize_t arpsend(struct iodesc *, void *, size_t); 63 static ssize_t arprecv(struct iodesc *, void **, void **, time_t, void *); 64 65 /* Broadcast an ARP packet, asking who has addr on interface d */ 66 u_char * 67 arpwhohas(struct iodesc *d, struct in_addr addr) 68 { 69 int i; 70 struct ether_arp *ah; 71 struct arp_list *al; 72 void *pkt; 73 struct { 74 struct ether_header eh; 75 struct { 76 struct ether_arp arp; 77 u_char pad[18]; /* 60 - sizeof(...) */ 78 } data; 79 } wbuf; 80 81 /* Try for cached answer first */ 82 for (i = 0, al = arp_list; i < arp_num; ++i, ++al) 83 if (addr.s_addr == al->addr.s_addr) 84 return (al->ea); 85 86 /* Don't overflow cache */ 87 if (arp_num > ARP_NUM - 1) { 88 arp_num = 1; /* recycle */ 89 printf("arpwhohas: overflowed arp_list!\n"); 90 } 91 92 #ifdef ARP_DEBUG 93 if (debug) 94 printf("arpwhohas: send request for %s\n", inet_ntoa(addr)); 95 #endif 96 97 bzero((char*)&wbuf.data, sizeof(wbuf.data)); 98 ah = &wbuf.data.arp; 99 ah->arp_hrd = htons(ARPHRD_ETHER); 100 ah->arp_pro = htons(ETHERTYPE_IP); 101 ah->arp_hln = sizeof(ah->arp_sha); /* hardware address length */ 102 ah->arp_pln = sizeof(ah->arp_spa); /* protocol address length */ 103 ah->arp_op = htons(ARPOP_REQUEST); 104 MACPY(d->myea, ah->arp_sha); 105 bcopy(&d->myip, ah->arp_spa, sizeof(ah->arp_spa)); 106 /* Leave zeros in arp_tha */ 107 bcopy(&addr, ah->arp_tpa, sizeof(ah->arp_tpa)); 108 109 /* Store ip address in cache (incomplete entry). */ 110 al->addr = addr; 111 112 pkt = NULL; 113 ah = NULL; 114 i = sendrecv(d, 115 arpsend, &wbuf.data, sizeof(wbuf.data), 116 arprecv, &pkt, (void **)&ah, NULL); 117 if (i == -1) { 118 panic("arp: no response for %s", 119 inet_ntoa(addr)); 120 } 121 122 /* Store ethernet address in cache */ 123 #ifdef ARP_DEBUG 124 if (debug) { 125 struct ether_header *eh; 126 127 eh = (struct ether_header *)((uintptr_t)pkt + ETHER_ALIGN); 128 printf("arp: response from %s\n", 129 ether_sprintf(eh->ether_shost)); 130 printf("arp: cacheing %s --> %s\n", 131 inet_ntoa(addr), ether_sprintf(ah->arp_sha)); 132 } 133 #endif 134 MACPY(ah->arp_sha, al->ea); 135 ++arp_num; 136 137 free(pkt); 138 return (al->ea); 139 } 140 141 static ssize_t 142 arpsend(struct iodesc *d, void *pkt, size_t len) 143 { 144 145 #ifdef ARP_DEBUG 146 if (debug) 147 printf("arpsend: called\n"); 148 #endif 149 150 return (sendether(d, pkt, len, bcea, ETHERTYPE_ARP)); 151 } 152 153 /* 154 * Returns 0 if this is the packet we're waiting for 155 * else -1 (and errno == 0) 156 */ 157 static ssize_t 158 arprecv(struct iodesc *d, void **pkt, void **payload, time_t tleft, void *extra) 159 { 160 ssize_t n; 161 struct ether_arp *ah; 162 uint16_t etype; /* host order */ 163 void *ptr; 164 165 #ifdef ARP_DEBUG 166 if (debug) 167 printf("arprecv: "); 168 #endif 169 170 ptr = NULL; 171 n = readether(d, &ptr, (void **)&ah, tleft, &etype); 172 errno = 0; /* XXX */ 173 if (n == -1 || n < sizeof(struct ether_arp)) { 174 #ifdef ARP_DEBUG 175 if (debug) 176 printf("bad len=%zd\n", n); 177 #endif 178 free(ptr); 179 return (-1); 180 } 181 182 if (etype != ETHERTYPE_ARP) { 183 #ifdef ARP_DEBUG 184 if (debug) 185 printf("not arp type=%d\n", etype); 186 #endif 187 free(ptr); 188 return (-1); 189 } 190 191 /* Ethernet address now checked in readether() */ 192 if (ah->arp_hrd != htons(ARPHRD_ETHER) || 193 ah->arp_pro != htons(ETHERTYPE_IP) || 194 ah->arp_hln != sizeof(ah->arp_sha) || 195 ah->arp_pln != sizeof(ah->arp_spa) ) 196 { 197 #ifdef ARP_DEBUG 198 if (debug) 199 printf("bad hrd/pro/hln/pln\n"); 200 #endif 201 free(ptr); 202 return (-1); 203 } 204 205 if (ah->arp_op == htons(ARPOP_REQUEST)) { 206 #ifdef ARP_DEBUG 207 if (debug) 208 printf("is request\n"); 209 #endif 210 arp_reply(d, ah); 211 free(ptr); 212 return (-1); 213 } 214 215 if (ah->arp_op != htons(ARPOP_REPLY)) { 216 #ifdef ARP_DEBUG 217 if (debug) 218 printf("not ARP reply\n"); 219 #endif 220 free(ptr); 221 return (-1); 222 } 223 224 /* Is the reply from the source we want? */ 225 if (bcmp(&arp_list[arp_num].addr, 226 ah->arp_spa, sizeof(ah->arp_spa))) 227 { 228 #ifdef ARP_DEBUG 229 if (debug) 230 printf("unwanted address\n"); 231 #endif 232 free(ptr); 233 return (-1); 234 } 235 /* We don't care who the reply was sent to. */ 236 237 /* We have our answer. */ 238 #ifdef ARP_DEBUG 239 if (debug) 240 printf("got it\n"); 241 #endif 242 *pkt = ptr; 243 *payload = ah; 244 return (n); 245 } 246 247 /* 248 * Convert an ARP request into a reply and send it. 249 * Notes: Re-uses buffer. Pad to length = 46. 250 */ 251 void 252 arp_reply(struct iodesc *d, void *pkt) 253 { 254 struct ether_arp *arp = pkt; 255 256 if (arp->arp_hrd != htons(ARPHRD_ETHER) || 257 arp->arp_pro != htons(ETHERTYPE_IP) || 258 arp->arp_hln != sizeof(arp->arp_sha) || 259 arp->arp_pln != sizeof(arp->arp_spa) ) 260 { 261 #ifdef ARP_DEBUG 262 if (debug) 263 printf("arp_reply: bad hrd/pro/hln/pln\n"); 264 #endif 265 return; 266 } 267 268 if (arp->arp_op != htons(ARPOP_REQUEST)) { 269 #ifdef ARP_DEBUG 270 if (debug) 271 printf("arp_reply: not request!\n"); 272 #endif 273 return; 274 } 275 276 /* If we are not the target, ignore the request. */ 277 if (bcmp(arp->arp_tpa, &d->myip, sizeof(arp->arp_tpa))) 278 return; 279 280 #ifdef ARP_DEBUG 281 if (debug) { 282 printf("arp_reply: to %s\n", ether_sprintf(arp->arp_sha)); 283 } 284 #endif 285 286 arp->arp_op = htons(ARPOP_REPLY); 287 /* source becomes target */ 288 bcopy(arp->arp_sha, arp->arp_tha, sizeof(arp->arp_tha)); 289 bcopy(arp->arp_spa, arp->arp_tpa, sizeof(arp->arp_tpa)); 290 /* here becomes source */ 291 bcopy(d->myea, arp->arp_sha, sizeof(arp->arp_sha)); 292 bcopy(&d->myip, arp->arp_spa, sizeof(arp->arp_spa)); 293 294 /* 295 * No need to get fancy here. If the send fails, the 296 * requestor will just ask again. 297 */ 298 (void) sendether(d, pkt, sizeof(*arp) + 18, 299 arp->arp_tha, ETHERTYPE_ARP); 300 } 301