1 /* $NetBSD: arp.c,v 1.35 2019/03/31 20:08:45 christos 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 <net/if_ether.h> 46 #include <netinet/in.h> 47 48 #include <netinet/in_systm.h> 49 50 #ifdef _STANDALONE 51 #include <lib/libkern/libkern.h> 52 #else 53 #include <arpa/inet.h> 54 #include <string.h> 55 #endif 56 57 #include "stand.h" 58 #include "net.h" 59 60 /* 61 * Ethernet Address Resolution Protocol. 62 * 63 * See RFC 826 for protocol description. Structure below is adapted 64 * to resolving internet addresses. Field names used correspond to 65 * RFC 826. 66 */ 67 struct ether_arp { 68 struct arphdr ea_hdr; /* fixed-size header */ 69 u_int8_t arp_sha[ETHER_ADDR_LEN]; /* sender hardware address */ 70 u_int8_t arp_spa[4]; /* sender protocol address */ 71 u_int8_t arp_tha[ETHER_ADDR_LEN]; /* target hardware address */ 72 u_int8_t arp_tpa[4]; /* target protocol address */ 73 }; 74 #define arp_hrd ea_hdr.ar_hrd 75 #define arp_pro ea_hdr.ar_pro 76 #define arp_hln ea_hdr.ar_hln 77 #define arp_pln ea_hdr.ar_pln 78 #define arp_op ea_hdr.ar_op 79 80 /* Cache stuff */ 81 #define ARP_NUM 8 /* need at most 3 arp entries */ 82 83 struct arp_list { 84 struct in_addr addr; 85 u_char ea[ETHER_ADDR_LEN]; 86 } arp_list[ARP_NUM] = { 87 /* XXX - net order `INADDR_BROADCAST' must be a constant */ 88 { {0xffffffff}, BA } 89 }; 90 int arp_num = 1; 91 92 /* Local forwards */ 93 static ssize_t arpsend(struct iodesc *, void *, size_t); 94 static ssize_t arprecv(struct iodesc *, void *, size_t, saseconds_t); 95 96 /* Broadcast an ARP packet, asking who has addr on interface d */ 97 u_char * 98 arpwhohas(struct iodesc *d, struct in_addr addr) 99 { 100 int i; 101 ssize_t ns; 102 struct ether_arp *ah; 103 struct arp_list *al; 104 struct { 105 struct ether_header eh; 106 struct { 107 struct ether_arp arp; 108 u_char pad[18]; /* 60 - sizeof(...) */ 109 } data; 110 } wbuf; 111 struct { 112 struct ether_header eh; 113 struct { 114 struct ether_arp arp; 115 u_char pad[24]; /* extra space */ 116 } data; 117 } rbuf; 118 119 /* Try for cached answer first */ 120 for (i = 0, al = arp_list; i < arp_num; ++i, ++al) 121 if (addr.s_addr == al->addr.s_addr) 122 return al->ea; 123 124 /* Don't overflow cache */ 125 if (arp_num > ARP_NUM - 1) { 126 arp_num = 1; /* recycle */ 127 printf("%s: overflowed arp_list!\n", __func__); 128 } 129 130 #ifdef ARP_DEBUG 131 if (debug) 132 printf("%s: send request for %s\n", __func__, inet_ntoa(addr)); 133 #endif 134 135 (void)memset(&wbuf.data, 0, sizeof(wbuf.data)); 136 ah = &wbuf.data.arp; 137 ah->arp_hrd = htons(ARPHRD_ETHER); 138 ah->arp_pro = htons(ETHERTYPE_IP); 139 ah->arp_hln = sizeof(ah->arp_sha); /* hardware address length */ 140 ah->arp_pln = sizeof(ah->arp_spa); /* protocol address length */ 141 ah->arp_op = htons(ARPOP_REQUEST); 142 MACPY(d->myea, ah->arp_sha); 143 (void)memcpy(ah->arp_spa, &d->myip, sizeof(ah->arp_spa)); 144 /* Leave zeros in arp_tha */ 145 (void)memcpy(ah->arp_tpa, &addr, sizeof(ah->arp_tpa)); 146 147 /* Store ip address in cache (incomplete entry). */ 148 al->addr = addr; 149 150 ns = sendrecv(d, 151 arpsend, &wbuf.data, sizeof(wbuf.data), 152 arprecv, &rbuf.data, sizeof(rbuf.data)); 153 if (ns == -1) { 154 panic("%s: no response for %s", __func__, inet_ntoa(addr)); 155 } 156 157 /* Store ethernet address in cache */ 158 ah = &rbuf.data.arp; 159 #ifdef ARP_DEBUG 160 if (debug) { 161 printf("%s: response from %s\n", __func__, 162 ether_sprintf(rbuf.eh.ether_shost)); 163 printf("%s: cacheing %s --> %s\n", __func__, 164 inet_ntoa(addr), ether_sprintf(ah->arp_sha)); 165 } 166 #endif 167 MACPY(ah->arp_sha, al->ea); 168 ++arp_num; 169 170 return al->ea; 171 } 172 173 static ssize_t 174 arpsend(struct iodesc *d, void *pkt, size_t len) 175 { 176 177 #ifdef ARP_DEBUG 178 if (debug) 179 printf("%s: called\n", __func__); 180 #endif 181 182 return sendether(d, pkt, len, bcea, ETHERTYPE_ARP); 183 } 184 185 /* 186 * Returns 0 if this is the packet we're waiting for 187 * else -1 (and errno == 0) 188 */ 189 static ssize_t 190 arprecv(struct iodesc *d, void *pkt, size_t len, saseconds_t tleft) 191 { 192 ssize_t n; 193 struct ether_arp *ah; 194 u_int16_t etype; /* host order */ 195 196 #ifdef ARP_DEBUG 197 if (debug) 198 printf("%s: ", __func__); 199 #endif 200 n = readether(d, pkt, len, tleft, &etype); 201 errno = 0; /* XXX */ 202 if (n == -1 || (size_t)n < sizeof(struct ether_arp)) { 203 #ifdef ARP_DEBUG 204 if (debug) 205 printf("bad len=%zd\n", n); 206 #endif 207 return -1; 208 } 209 210 if (etype != ETHERTYPE_ARP) { 211 #ifdef ARP_DEBUG 212 if (debug) 213 printf("not arp type=%d\n", etype); 214 #endif 215 return -1; 216 } 217 218 /* Ethernet address now checked in readether() */ 219 220 ah = (struct ether_arp *)pkt; 221 if (ah->arp_hrd != htons(ARPHRD_ETHER) || 222 ah->arp_pro != htons(ETHERTYPE_IP) || 223 ah->arp_hln != sizeof(ah->arp_sha) || 224 ah->arp_pln != sizeof(ah->arp_spa) ) 225 { 226 #ifdef ARP_DEBUG 227 if (debug) 228 printf("bad hrd/pro/hln/pln\n"); 229 #endif 230 return -1; 231 } 232 233 if (ah->arp_op == htons(ARPOP_REQUEST)) { 234 #ifdef ARP_DEBUG 235 if (debug) 236 printf("is request\n"); 237 #endif 238 arp_reply(d, ah); 239 return -1; 240 } 241 242 if (ah->arp_op != htons(ARPOP_REPLY)) { 243 #ifdef ARP_DEBUG 244 if (debug) 245 printf("not ARP reply\n"); 246 #endif 247 return -1; 248 } 249 250 /* Is the reply from the source we want? */ 251 if (memcmp(&arp_list[arp_num].addr, 252 ah->arp_spa, sizeof(ah->arp_spa))) 253 { 254 #ifdef ARP_DEBUG 255 if (debug) 256 printf("unwanted address\n"); 257 #endif 258 return -1; 259 } 260 /* We don't care who the reply was sent to. */ 261 262 /* We have our answer. */ 263 #ifdef ARP_DEBUG 264 if (debug) 265 printf("got it\n"); 266 #endif 267 return n; 268 } 269 270 /* 271 * Convert an ARP request into a reply and send it. 272 * Notes: Re-uses buffer. Pad to length = 46. 273 */ 274 void 275 arp_reply(struct iodesc *d, void *pkt) 276 { 277 struct ether_arp *arp = pkt; 278 279 if (arp->arp_hrd != htons(ARPHRD_ETHER) || 280 arp->arp_pro != htons(ETHERTYPE_IP) || 281 arp->arp_hln != sizeof(arp->arp_sha) || 282 arp->arp_pln != sizeof(arp->arp_spa) ) 283 { 284 #ifdef ARP_DEBUG 285 if (debug) 286 printf("%s: bad hrd/pro/hln/pln\n", __func__); 287 #endif 288 return; 289 } 290 291 if (arp->arp_op != htons(ARPOP_REQUEST)) { 292 #ifdef ARP_DEBUG 293 if (debug) 294 printf("%s: not request!\n", __func__); 295 #endif 296 return; 297 } 298 299 /* If we are not the target, ignore the request. */ 300 if (memcmp(arp->arp_tpa, &d->myip, sizeof(arp->arp_tpa))) 301 return; 302 303 #ifdef ARP_DEBUG 304 if (debug) { 305 printf("%s: to %s\n", __func__, ether_sprintf(arp->arp_sha)); 306 } 307 #endif 308 309 arp->arp_op = htons(ARPOP_REPLY); 310 /* source becomes target */ 311 (void)memcpy(arp->arp_tha, arp->arp_sha, sizeof(arp->arp_tha)); 312 (void)memcpy(arp->arp_tpa, arp->arp_spa, sizeof(arp->arp_tpa)); 313 /* here becomes source */ 314 (void)memcpy(arp->arp_sha, d->myea, sizeof(arp->arp_sha)); 315 (void)memcpy(arp->arp_spa, &d->myip, sizeof(arp->arp_spa)); 316 317 /* 318 * No need to get fancy here. If the send fails, the 319 * requestor will just ask again. 320 */ 321 (void) sendether(d, pkt, sizeof(*arp) + 18, 322 arp->arp_tha, ETHERTYPE_ARP); 323 } 324
Indexes created Tue Sep 30 17:09:57 GMT 2025