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