1 /* $OpenBSD: arp.c,v 1.13 2021/03/12 10:22:46 jsg Exp $ */ 2 /* $NetBSD: arp.c,v 1.15 1996/10/13 02:28:58 christos Exp $ */ 3 4 /* 5 * Copyright (c) 1992 Regents of the University of California. 6 * All rights reserved. 7 * 8 * This software was developed by the Computer Systems Engineering group 9 * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and 10 * contributed to Berkeley. 11 * 12 * Redistribution and use in source and binary forms, with or without 13 * modification, are permitted provided that the following conditions 14 * are met: 15 * 1. Redistributions of source code must retain the above copyright 16 * notice, this list of conditions and the following disclaimer. 17 * 2. Redistributions in binary form must reproduce the above copyright 18 * notice, this list of conditions and the following disclaimer in the 19 * documentation and/or other materials provided with the distribution. 20 * 3. All advertising materials mentioning features or use of this software 21 * must display the following acknowledgement: 22 * This product includes software developed by the University of 23 * California, Lawrence Berkeley Laboratory and its contributors. 24 * 4. Neither the name of the University nor the names of its contributors 25 * may be used to endorse or promote products derived from this software 26 * without specific prior written permission. 27 * 28 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 29 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 30 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 31 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 32 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 33 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 34 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 35 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 37 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 38 * SUCH DAMAGE. 39 * 40 * @(#) Header: arp.c,v 1.5 93/07/15 05:52:26 leres Exp (LBL) 41 */ 42 43 #include <sys/types.h> 44 #include <sys/socket.h> 45 #include <net/if.h> 46 #include <netinet/in.h> 47 48 #include <netinet/if_ether.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 u_char 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 *, size_t, time_t); 68 69 /* Broadcast an ARP packet, asking who has addr on interface d */ 70 u_char * 71 arpwhohas(struct iodesc *d, struct in_addr addr) 72 { 73 int i; 74 struct ether_arp *ah; 75 struct arp_list *al; 76 struct { 77 struct ether_header eh; 78 struct { 79 struct ether_arp arp; 80 u_char pad[18]; /* 60 - sizeof(...) */ 81 } data; 82 } wbuf; 83 struct { 84 struct ether_header eh; 85 struct { 86 struct ether_arp arp; 87 u_char pad[24]; /* extra space */ 88 } data; 89 } rbuf; 90 91 /* Try for cached answer first */ 92 for (i = 0, al = arp_list; i < arp_num; ++i, ++al) 93 if (addr.s_addr == al->addr.s_addr) 94 return (al->ea); 95 96 /* Don't overflow cache */ 97 if (arp_num > ARP_NUM - 1) { 98 arp_num = 1; /* recycle */ 99 printf("arpwhohas: overflowed arp_list!\n"); 100 } 101 102 #ifdef ARP_DEBUG 103 if (debug) 104 printf("arpwhohas: send request for %s\n", inet_ntoa(addr)); 105 #endif 106 107 bzero((char *)&wbuf.data, sizeof(wbuf.data)); 108 ah = &wbuf.data.arp; 109 ah->arp_hrd = htons(ARPHRD_ETHER); 110 ah->arp_pro = htons(ETHERTYPE_IP); 111 ah->arp_hln = sizeof(ah->arp_sha); /* hardware address length */ 112 ah->arp_pln = sizeof(ah->arp_spa); /* protocol address length */ 113 ah->arp_op = htons(ARPOP_REQUEST); 114 MACPY(d->myea, ah->arp_sha); 115 bcopy(&d->myip, ah->arp_spa, sizeof(ah->arp_spa)); 116 /* Leave zeros in arp_tha */ 117 bcopy(&addr, ah->arp_tpa, sizeof(ah->arp_tpa)); 118 119 /* Store ip address in cache (incomplete entry). */ 120 al->addr = addr; 121 122 i = sendrecv(d, 123 arpsend, &wbuf.data, sizeof(wbuf.data), 124 arprecv, &rbuf.data, sizeof(rbuf.data)); 125 if (i == -1) { 126 panic("arp: no response for %s", inet_ntoa(addr)); 127 } 128 129 /* Store ethernet address in cache */ 130 ah = &rbuf.data.arp; 131 #ifdef ARP_DEBUG 132 if (debug) { 133 printf("arp: response from %s\n", 134 ether_sprintf(rbuf.eh.ether_shost)); 135 printf("arp: caching %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 return (al->ea); 143 } 144 145 static ssize_t 146 arpsend(struct iodesc *d, void *pkt, size_t len) 147 { 148 149 #ifdef ARP_DEBUG 150 if (debug) 151 printf("arpsend: called\n"); 152 #endif 153 154 return (sendether(d, pkt, len, bcea, ETHERTYPE_ARP)); 155 } 156 157 /* 158 * Returns 0 if this is the packet we're waiting for 159 * else -1 (and errno == 0) 160 */ 161 static ssize_t 162 arprecv(struct iodesc *d, void *pkt, size_t len, time_t tleft) 163 { 164 ssize_t n; 165 struct ether_arp *ah; 166 u_int16_t etype; /* host order */ 167 168 #ifdef ARP_DEBUG 169 if (debug) 170 printf("arprecv: "); 171 #endif 172 173 n = readether(d, pkt, len, tleft, &etype); 174 errno = 0; /* XXX */ 175 if (n < 0 || (size_t)n < sizeof(struct ether_arp)) { 176 #ifdef ARP_DEBUG 177 if (debug) 178 printf("bad len=%d\n", n); 179 #endif 180 return (-1); 181 } 182 183 if (etype != ETHERTYPE_ARP) { 184 #ifdef ARP_DEBUG 185 if (debug) 186 printf("not arp type=%d\n", etype); 187 #endif 188 return (-1); 189 } 190 191 /* Ethernet address now checked in readether() */ 192 193 ah = (struct ether_arp *)pkt; 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 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 return (-1); 212 } 213 214 if (ah->arp_op != htons(ARPOP_REPLY)) { 215 #ifdef ARP_DEBUG 216 if (debug) 217 printf("not ARP reply\n"); 218 #endif 219 return (-1); 220 } 221 222 /* Is the reply from the source we want? */ 223 if (bcmp(&arp_list[arp_num].addr, ah->arp_spa, 224 sizeof(ah->arp_spa))) { 225 #ifdef ARP_DEBUG 226 if (debug) 227 printf("unwanted address\n"); 228 #endif 229 return (-1); 230 } 231 /* We don't care who the reply was sent to. */ 232 233 /* We have our answer. */ 234 #ifdef ARP_DEBUG 235 if (debug) 236 printf("got it\n"); 237 #endif 238 return (n); 239 } 240 241 /* 242 * Convert an ARP request into a reply and send it. 243 * Notes: Re-uses buffer. Pad to length = 46. 244 */ 245 void 246 arp_reply(struct iodesc *d, void *pkt) 247 { 248 struct ether_arp *arp = pkt; 249 250 if (arp->arp_hrd != htons(ARPHRD_ETHER) || 251 arp->arp_pro != htons(ETHERTYPE_IP) || 252 arp->arp_hln != sizeof(arp->arp_sha) || 253 arp->arp_pln != sizeof(arp->arp_spa)) { 254 #ifdef ARP_DEBUG 255 if (debug) 256 printf("arp_reply: bad hrd/pro/hln/pln\n"); 257 #endif 258 return; 259 } 260 261 if (arp->arp_op != htons(ARPOP_REQUEST)) { 262 #ifdef ARP_DEBUG 263 if (debug) 264 printf("arp_reply: not request!\n"); 265 #endif 266 return; 267 } 268 269 /* If we are not the target, ignore the request. */ 270 if (bcmp(arp->arp_tpa, &d->myip, sizeof(arp->arp_tpa))) 271 return; 272 273 #ifdef ARP_DEBUG 274 if (debug) { 275 printf("arp_reply: to %s\n", ether_sprintf(arp->arp_sha)); 276 } 277 #endif 278 279 arp->arp_op = htons(ARPOP_REPLY); 280 /* source becomes target */ 281 bcopy(arp->arp_sha, arp->arp_tha, sizeof(arp->arp_tha)); 282 bcopy(arp->arp_spa, arp->arp_tpa, sizeof(arp->arp_tpa)); 283 /* here becomes source */ 284 bcopy(d->myea, arp->arp_sha, sizeof(arp->arp_sha)); 285 bcopy(&d->myip, arp->arp_spa, sizeof(arp->arp_spa)); 286 287 /* 288 * No need to get fancy here. If the send fails, the 289 * requestor will just ask again. 290 */ 291 (void) sendether(d, pkt, sizeof(*arp) + 18, 292 arp->arp_tha, ETHERTYPE_ARP); 293 } 294