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 * @(#) Header: arp.c,v 1.5 93/07/15 05:52:26 leres Exp (LBL) 36 */ 37 38 #include <sys/cdefs.h> 39 __FBSDID("$FreeBSD$"); 40 41 #include <sys/types.h> 42 #include <sys/socket.h> 43 #include <net/if.h> 44 #include <netinet/in.h> 45 #include <netinet/if_ether.h> 46 47 #include <netinet/in_systm.h> 48 49 #include <string.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(struct iodesc *, void *, size_t); 68 static ssize_t arprecv(struct iodesc *, void **, void **, time_t, void *); 69 70 /* Broadcast an ARP packet, asking who has addr on interface d */ 71 u_char * 72 arpwhohas(struct iodesc *d, struct in_addr addr) 73 { 74 int i; 75 struct ether_arp *ah; 76 struct arp_list *al; 77 void *pkt; 78 struct { 79 struct ether_header eh; 80 struct { 81 struct ether_arp arp; 82 u_char pad[18]; /* 60 - sizeof(...) */ 83 } data; 84 } wbuf; 85 86 /* Try for cached answer first */ 87 for (i = 0, al = arp_list; i < arp_num; ++i, ++al) 88 if (addr.s_addr == al->addr.s_addr) 89 return (al->ea); 90 91 /* Don't overflow cache */ 92 if (arp_num > ARP_NUM - 1) { 93 arp_num = 1; /* recycle */ 94 printf("arpwhohas: overflowed arp_list!\n"); 95 } 96 97 #ifdef ARP_DEBUG 98 if (debug) 99 printf("arpwhohas: send request for %s\n", inet_ntoa(addr)); 100 #endif 101 102 bzero((char*)&wbuf.data, sizeof(wbuf.data)); 103 ah = &wbuf.data.arp; 104 ah->arp_hrd = htons(ARPHRD_ETHER); 105 ah->arp_pro = htons(ETHERTYPE_IP); 106 ah->arp_hln = sizeof(ah->arp_sha); /* hardware address length */ 107 ah->arp_pln = sizeof(ah->arp_spa); /* protocol address length */ 108 ah->arp_op = htons(ARPOP_REQUEST); 109 MACPY(d->myea, ah->arp_sha); 110 bcopy(&d->myip, ah->arp_spa, sizeof(ah->arp_spa)); 111 /* Leave zeros in arp_tha */ 112 bcopy(&addr, ah->arp_tpa, sizeof(ah->arp_tpa)); 113 114 /* Store ip address in cache (incomplete entry). */ 115 al->addr = addr; 116 117 pkt = NULL; 118 ah = NULL; 119 i = sendrecv(d, 120 arpsend, &wbuf.data, sizeof(wbuf.data), 121 arprecv, &pkt, (void **)&ah, NULL); 122 if (i == -1) { 123 panic("arp: no response for %s", 124 inet_ntoa(addr)); 125 } 126 127 /* Store ethernet address in cache */ 128 #ifdef ARP_DEBUG 129 if (debug) { 130 struct ether_header *eh; 131 132 eh = (struct ether_header *)((uintptr_t)pkt + ETHER_ALIGN); 133 printf("arp: response from %s\n", 134 ether_sprintf(eh->ether_shost)); 135 printf("arp: cacheing %s --> %s\n", 136 inet_ntoa(addr), ether_sprintf(ah->arp_sha)); 137 } 138 #endif 139 MACPY(ah->arp_sha, al->ea); 140 ++arp_num; 141 142 free(pkt); 143 return (al->ea); 144 } 145 146 static ssize_t 147 arpsend(struct iodesc *d, void *pkt, size_t len) 148 { 149 150 #ifdef ARP_DEBUG 151 if (debug) 152 printf("arpsend: called\n"); 153 #endif 154 155 return (sendether(d, pkt, len, bcea, ETHERTYPE_ARP)); 156 } 157 158 /* 159 * Returns 0 if this is the packet we're waiting for 160 * else -1 (and errno == 0) 161 */ 162 static ssize_t 163 arprecv(struct iodesc *d, void **pkt, void **payload, time_t tleft, void *extra) 164 { 165 ssize_t n; 166 struct ether_arp *ah; 167 uint16_t etype; /* host order */ 168 void *ptr; 169 170 #ifdef ARP_DEBUG 171 if (debug) 172 printf("arprecv: "); 173 #endif 174 175 ptr = NULL; 176 n = readether(d, &ptr, (void **)&ah, tleft, &etype); 177 errno = 0; /* XXX */ 178 if (n == -1 || n < sizeof(struct ether_arp)) { 179 #ifdef ARP_DEBUG 180 if (debug) 181 printf("bad len=%zd\n", n); 182 #endif 183 free(ptr); 184 return (-1); 185 } 186 187 if (etype != ETHERTYPE_ARP) { 188 #ifdef ARP_DEBUG 189 if (debug) 190 printf("not arp type=%d\n", etype); 191 #endif 192 free(ptr); 193 return (-1); 194 } 195 196 /* Ethernet address now checked in readether() */ 197 if (ah->arp_hrd != htons(ARPHRD_ETHER) || 198 ah->arp_pro != htons(ETHERTYPE_IP) || 199 ah->arp_hln != sizeof(ah->arp_sha) || 200 ah->arp_pln != sizeof(ah->arp_spa) ) 201 { 202 #ifdef ARP_DEBUG 203 if (debug) 204 printf("bad hrd/pro/hln/pln\n"); 205 #endif 206 free(ptr); 207 return (-1); 208 } 209 210 if (ah->arp_op == htons(ARPOP_REQUEST)) { 211 #ifdef ARP_DEBUG 212 if (debug) 213 printf("is request\n"); 214 #endif 215 arp_reply(d, ah); 216 free(ptr); 217 return (-1); 218 } 219 220 if (ah->arp_op != htons(ARPOP_REPLY)) { 221 #ifdef ARP_DEBUG 222 if (debug) 223 printf("not ARP reply\n"); 224 #endif 225 free(ptr); 226 return (-1); 227 } 228 229 /* Is the reply from the source we want? */ 230 if (bcmp(&arp_list[arp_num].addr, 231 ah->arp_spa, sizeof(ah->arp_spa))) 232 { 233 #ifdef ARP_DEBUG 234 if (debug) 235 printf("unwanted address\n"); 236 #endif 237 free(ptr); 238 return (-1); 239 } 240 /* We don't care who the reply was sent to. */ 241 242 /* We have our answer. */ 243 #ifdef ARP_DEBUG 244 if (debug) 245 printf("got it\n"); 246 #endif 247 *pkt = ptr; 248 *payload = ah; 249 return (n); 250 } 251 252 /* 253 * Convert an ARP request into a reply and send it. 254 * Notes: Re-uses buffer. Pad to length = 46. 255 */ 256 void 257 arp_reply(struct iodesc *d, void *pkt) 258 { 259 struct ether_arp *arp = pkt; 260 261 if (arp->arp_hrd != htons(ARPHRD_ETHER) || 262 arp->arp_pro != htons(ETHERTYPE_IP) || 263 arp->arp_hln != sizeof(arp->arp_sha) || 264 arp->arp_pln != sizeof(arp->arp_spa) ) 265 { 266 #ifdef ARP_DEBUG 267 if (debug) 268 printf("arp_reply: bad hrd/pro/hln/pln\n"); 269 #endif 270 return; 271 } 272 273 if (arp->arp_op != htons(ARPOP_REQUEST)) { 274 #ifdef ARP_DEBUG 275 if (debug) 276 printf("arp_reply: not request!\n"); 277 #endif 278 return; 279 } 280 281 /* If we are not the target, ignore the request. */ 282 if (bcmp(arp->arp_tpa, &d->myip, sizeof(arp->arp_tpa))) 283 return; 284 285 #ifdef ARP_DEBUG 286 if (debug) { 287 printf("arp_reply: to %s\n", ether_sprintf(arp->arp_sha)); 288 } 289 #endif 290 291 arp->arp_op = htons(ARPOP_REPLY); 292 /* source becomes target */ 293 bcopy(arp->arp_sha, arp->arp_tha, sizeof(arp->arp_tha)); 294 bcopy(arp->arp_spa, arp->arp_tpa, sizeof(arp->arp_tpa)); 295 /* here becomes source */ 296 bcopy(d->myea, arp->arp_sha, sizeof(arp->arp_sha)); 297 bcopy(&d->myip, arp->arp_spa, sizeof(arp->arp_spa)); 298 299 /* 300 * No need to get fancy here. If the send fails, the 301 * requestor will just ask again. 302 */ 303 (void) sendether(d, pkt, sizeof(*arp) + 18, 304 arp->arp_tha, ETHERTYPE_ARP); 305 } 306