lib/libstand/arp.c

   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  * $DragonFly: src/lib/libstand/arp.c,v 1.4 2005/12/11 02:27:26 swildner Exp $
  37  */
  38
  39 #include <sys/param.h>
  40 #include <sys/socket.h>
  41 #include <net/if.h>
  42 #include <netinet/in.h>
  43 #include <netinet/if_ether.h>
  44
  45 #include <netinet/in_systm.h>
  46
  47 #include <string.h>
  48
  49 #include "stand.h"
  50 #include "net.h"
  51
  52 /* Cache stuff */
  53 #define ARP_NUM 8                       /* need at most 3 arp entries */
  54
  55 struct arp_list {
  56         struct in_addr  addr;
  57         u_char          ea[6];
  58 } arp_list[ARP_NUM] = {
  59         /* XXX - net order `INADDR_BROADCAST' must be a constant */
  60         { {0xffffffff}, BA }
  61 };
  62 int arp_num = 1;
  63
  64 /* Local forwards */
  65 static  ssize_t arpsend(struct iodesc *, void *, size_t);
  66 static  ssize_t arprecv(struct iodesc *, void *, size_t, time_t);
  67
  68 /* Broadcast an ARP packet, asking who has addr on interface d */
  69 u_char *
  70 arpwhohas(struct iodesc *d, struct in_addr addr)
  71 {
  72         int i;
  73         struct ether_arp *ah;
  74         struct arp_list *al;
  75         struct {
  76                 struct ether_header eh;
  77                 struct {
  78                         struct ether_arp arp;
  79                         u_char pad[18];         /* 60 - sizeof(...) */
  80                 } data;
  81         } wbuf;
  82         struct {
  83                 struct ether_header eh;
  84                 struct {
  85                         struct ether_arp arp;
  86                         u_char pad[24];         /* extra space */
  87                 } data;
  88         } rbuf;
  89
  90         /* Try for cached answer first */
  91         for (i = 0, al = arp_list; i < arp_num; ++i, ++al)
  92                 if (addr.s_addr == al->addr.s_addr)
  93                         return (al->ea);
  94
  95         /* Don't overflow cache */
  96         if (arp_num > ARP_NUM - 1) {
  97                 arp_num = 1;    /* recycle */
  98                 printf("arpwhohas: overflowed arp_list!\n");
  99         }
 100
 101 #ifdef ARP_DEBUG
 102         if (debug)
 103             printf("arpwhohas: send request for %s\n", inet_ntoa(addr));
 104 #endif
 105
 106         bzero((char*)&wbuf.data, sizeof(wbuf.data));
 107         ah = &wbuf.data.arp;
 108         ah->arp_hrd = htons(ARPHRD_ETHER);
 109         ah->arp_pro = htons(ETHERTYPE_IP);
 110         ah->arp_hln = sizeof(ah->arp_sha); /* hardware address length */
 111         ah->arp_pln = sizeof(ah->arp_spa); /* protocol address length */
 112         ah->arp_op = htons(ARPOP_REQUEST);
 113         MACPY(d->myea, ah->arp_sha);
 114         bcopy(&d->myip, ah->arp_spa, sizeof(ah->arp_spa));
 115         /* Leave zeros in arp_tha */
 116         bcopy(&addr, ah->arp_tpa, sizeof(ah->arp_tpa));
 117
 118         /* Store ip address in cache (incomplete entry). */
 119         al->addr = addr;
 120
 121         i = sendrecv(d,
 122             arpsend, &wbuf.data, sizeof(wbuf.data),
 123             arprecv, &rbuf.data, sizeof(rbuf.data));
 124         if (i == -1) {
 125                 panic("arp: no response for %s\n",
 126                           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: 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         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 == -1 || 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         {
 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,
 225                          ah->arp_spa, sizeof(ah->arp_spa)))
 226         {
 227 #ifdef ARP_DEBUG
 228                 if (debug)
 229                         printf("unwanted address\n");
 230 #endif
 231                 return (-1);
 232         }
 233         /* We don't care who the reply was sent to. */
 234
 235         /* We have our answer. */
 236 #ifdef ARP_DEBUG
 237         if (debug)
 238                 printf("got it\n");
 239 #endif
 240         return (n);
 241 }
 242
 243 /*
 244  * Convert an ARP request into a reply and send it.
 245  * Notes:  Re-uses buffer.  Pad to length = 46.
 246  *
 247  * Parameters:
 248  *      pkt:    the request
 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         {
 260 #ifdef ARP_DEBUG
 261                 if (debug)
 262                         printf("arp_reply: bad hrd/pro/hln/pln\n");
 263 #endif
 264                 return;
 265         }
 266
 267         if (arp->arp_op != htons(ARPOP_REQUEST)) {
 268 #ifdef ARP_DEBUG
 269                 if (debug)
 270                         printf("arp_reply: not request!\n");
 271 #endif
 272                 return;
 273         }
 274
 275         /* If we are not the target, ignore the request. */
 276         if (bcmp(arp->arp_tpa, &d->myip, sizeof(arp->arp_tpa)))
 277                 return;
 278
 279 #ifdef ARP_DEBUG
 280         if (debug) {
 281                 printf("arp_reply: to %s\n", ether_sprintf(arp->arp_sha));
 282         }
 283 #endif
 284
 285         arp->arp_op = htons(ARPOP_REPLY);
 286         /* source becomes target */
 287         bcopy(arp->arp_sha, arp->arp_tha, sizeof(arp->arp_tha));
 288         bcopy(arp->arp_spa, arp->arp_tpa, sizeof(arp->arp_tpa));
 289         /* here becomes source */
 290         bcopy(d->myea,  arp->arp_sha, sizeof(arp->arp_sha));
 291         bcopy(&d->myip, arp->arp_spa, sizeof(arp->arp_spa));
 292
 293         /*
 294          * No need to get fancy here.  If the send fails, the
 295          * requestor will just ask again.
 296          */
 297         (void) sendether(d, pkt, sizeof(*arp) + 18,
 298                          arp->arp_tha, ETHERTYPE_ARP);
 299 }