Annotation of sys/lib/libsa/arp.c, Revision 1.1
1.1 ! nbrk 1: /* $OpenBSD: arp.c,v 1.11 2003/08/11 06:23:09 deraadt 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: #include <netinet/in_systm.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 *, size_t, time_t);
! 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: struct {
! 78: struct ether_header eh;
! 79: struct {
! 80: struct ether_arp arp;
! 81: u_char pad[18]; /* 60 - sizeof(...) */
! 82: } data;
! 83: } wbuf;
! 84: struct {
! 85: struct ether_header eh;
! 86: struct {
! 87: struct ether_arp arp;
! 88: u_char pad[24]; /* extra space */
! 89: } data;
! 90: } rbuf;
! 91:
! 92: /* Try for cached answer first */
! 93: for (i = 0, al = arp_list; i < arp_num; ++i, ++al)
! 94: if (addr.s_addr == al->addr.s_addr)
! 95: return (al->ea);
! 96:
! 97: /* Don't overflow cache */
! 98: if (arp_num > ARP_NUM - 1) {
! 99: arp_num = 1; /* recycle */
! 100: printf("arpwhohas: overflowed arp_list!\n");
! 101: }
! 102:
! 103: #ifdef ARP_DEBUG
! 104: if (debug)
! 105: printf("arpwhohas: send request for %s\n", inet_ntoa(addr));
! 106: #endif
! 107:
! 108: bzero((char *)&wbuf.data, sizeof(wbuf.data));
! 109: ah = &wbuf.data.arp;
! 110: ah->arp_hrd = htons(ARPHRD_ETHER);
! 111: ah->arp_pro = htons(ETHERTYPE_IP);
! 112: ah->arp_hln = sizeof(ah->arp_sha); /* hardware address length */
! 113: ah->arp_pln = sizeof(ah->arp_spa); /* protocol address length */
! 114: ah->arp_op = htons(ARPOP_REQUEST);
! 115: MACPY(d->myea, ah->arp_sha);
! 116: bcopy(&d->myip, ah->arp_spa, sizeof(ah->arp_spa));
! 117: /* Leave zeros in arp_tha */
! 118: bcopy(&addr, ah->arp_tpa, sizeof(ah->arp_tpa));
! 119:
! 120: /* Store ip address in cache (incomplete entry). */
! 121: al->addr = addr;
! 122:
! 123: i = sendrecv(d,
! 124: arpsend, &wbuf.data, sizeof(wbuf.data),
! 125: arprecv, &rbuf.data, sizeof(rbuf.data));
! 126: if (i == -1) {
! 127: panic("arp: no response for %s", inet_ntoa(addr));
! 128: }
! 129:
! 130: /* Store ethernet address in cache */
! 131: ah = &rbuf.data.arp;
! 132: #ifdef ARP_DEBUG
! 133: if (debug) {
! 134: printf("arp: response from %s\n",
! 135: ether_sprintf(rbuf.eh.ether_shost));
! 136: printf("arp: cacheing %s --> %s\n",
! 137: inet_ntoa(addr), ether_sprintf(ah->arp_sha));
! 138: }
! 139: #endif
! 140: MACPY(ah->arp_sha, al->ea);
! 141: ++arp_num;
! 142:
! 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, size_t len, time_t tleft)
! 164: {
! 165: ssize_t n;
! 166: struct ether_arp *ah;
! 167: u_int16_t etype; /* host order */
! 168:
! 169: #ifdef ARP_DEBUG
! 170: if (debug)
! 171: printf("arprecv: ");
! 172: #endif
! 173:
! 174: n = readether(d, pkt, len, tleft, &etype);
! 175: errno = 0; /* XXX */
! 176: if (n < 0 || (size_t)n < sizeof(struct ether_arp)) {
! 177: #ifdef ARP_DEBUG
! 178: if (debug)
! 179: printf("bad len=%d\n", n);
! 180: #endif
! 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: return (-1);
! 190: }
! 191:
! 192: /* Ethernet address now checked in readether() */
! 193:
! 194: ah = (struct ether_arp *)pkt;
! 195: if (ah->arp_hrd != htons(ARPHRD_ETHER) ||
! 196: ah->arp_pro != htons(ETHERTYPE_IP) ||
! 197: ah->arp_hln != sizeof(ah->arp_sha) ||
! 198: ah->arp_pln != sizeof(ah->arp_spa)) {
! 199: #ifdef ARP_DEBUG
! 200: if (debug)
! 201: printf("bad hrd/pro/hln/pln\n");
! 202: #endif
! 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: 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: return (-1);
! 221: }
! 222:
! 223: /* Is the reply from the source we want? */
! 224: if (bcmp(&arp_list[arp_num].addr, ah->arp_spa,
! 225: sizeof(ah->arp_spa))) {
! 226: #ifdef ARP_DEBUG
! 227: if (debug)
! 228: printf("unwanted address\n");
! 229: #endif
! 230: return (-1);
! 231: }
! 232: /* We don't care who the reply was sent to. */
! 233:
! 234: /* We have our answer. */
! 235: #ifdef ARP_DEBUG
! 236: if (debug)
! 237: printf("got it\n");
! 238: #endif
! 239: return (n);
! 240: }
! 241:
! 242: /*
! 243: * Convert an ARP request into a reply and send it.
! 244: * Notes: Re-uses buffer. Pad to length = 46.
! 245: */
! 246: void
! 247: arp_reply(struct iodesc *d, void *pkt)
! 248: {
! 249: struct ether_arp *arp = pkt;
! 250:
! 251: if (arp->arp_hrd != htons(ARPHRD_ETHER) ||
! 252: arp->arp_pro != htons(ETHERTYPE_IP) ||
! 253: arp->arp_hln != sizeof(arp->arp_sha) ||
! 254: arp->arp_pln != sizeof(arp->arp_spa)) {
! 255: #ifdef ARP_DEBUG
! 256: if (debug)
! 257: printf("arp_reply: bad hrd/pro/hln/pln\n");
! 258: #endif
! 259: return;
! 260: }
! 261:
! 262: if (arp->arp_op != htons(ARPOP_REQUEST)) {
! 263: #ifdef ARP_DEBUG
! 264: if (debug)
! 265: printf("arp_reply: not request!\n");
! 266: #endif
! 267: return;
! 268: }
! 269:
! 270: /* If we are not the target, ignore the request. */
! 271: if (bcmp(arp->arp_tpa, &d->myip, sizeof(arp->arp_tpa)))
! 272: return;
! 273:
! 274: #ifdef ARP_DEBUG
! 275: if (debug) {
! 276: printf("arp_reply: to %s\n", ether_sprintf(arp->arp_sha));
! 277: }
! 278: #endif
! 279:
! 280: arp->arp_op = htons(ARPOP_REPLY);
! 281: /* source becomes target */
! 282: bcopy(arp->arp_sha, arp->arp_tha, sizeof(arp->arp_tha));
! 283: bcopy(arp->arp_spa, arp->arp_tpa, sizeof(arp->arp_tpa));
! 284: /* here becomes source */
! 285: bcopy(d->myea, arp->arp_sha, sizeof(arp->arp_sha));
! 286: bcopy(&d->myip, arp->arp_spa, sizeof(arp->arp_spa));
! 287:
! 288: /*
! 289: * No need to get fancy here. If the send fails, the
! 290: * requestor will just ask again.
! 291: */
! 292: (void) sendether(d, pkt, sizeof(*arp) + 18,
! 293: arp->arp_tha, ETHERTYPE_ARP);
! 294: }
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