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  * 4. 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 __FBSDID("$FreeBSD$");
  40
  41 #include <sys/types.h>
  42 #include <sys/socket.h>
  43 #include <net/if.h>
  44 #include <netinet/in.h>
  45 #include <netinet/if_ether.h>
  46
  47 #include <netinet/in_systm.h>
  48
  49 #include <string.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(d, addr)
  73         struct iodesc *d;
  74         struct in_addr addr;
  75 {
  76         int i;
  77         struct ether_arp *ah;
  78         struct arp_list *al;
  79         struct {
  80                 struct ether_header eh;
  81                 struct {
  82                         struct ether_arp arp;
  83                         u_char pad[18];         /* 60 - sizeof(...) */
  84                 } data;
  85         } wbuf;
  86         struct {
  87                 struct ether_header eh;
  88                 struct {
  89                         struct ether_arp arp;
  90                         u_char pad[24];         /* extra space */
  91                 } data;
  92         } rbuf;
  93
  94         /* Try for cached answer first */
  95         for (i = 0, al = arp_list; i < arp_num; ++i, ++al)
  96                 if (addr.s_addr == al->addr.s_addr)
  97                         return (al->ea);
  98
  99         /* Don't overflow cache */
 100         if (arp_num > ARP_NUM - 1) {
 101                 arp_num = 1;    /* recycle */
 102                 printf("arpwhohas: overflowed arp_list!\n");
 103         }
 104
 105 #ifdef ARP_DEBUG
 106         if (debug)
 107             printf("arpwhohas: send request for %s\n", inet_ntoa(addr));
 108 #endif
 109
 110         bzero((char*)&wbuf.data, sizeof(wbuf.data));
 111         ah = &wbuf.data.arp;
 112         ah->arp_hrd = htons(ARPHRD_ETHER);
 113         ah->arp_pro = htons(ETHERTYPE_IP);
 114         ah->arp_hln = sizeof(ah->arp_sha); /* hardware address length */
 115         ah->arp_pln = sizeof(ah->arp_spa); /* protocol address length */
 116         ah->arp_op = htons(ARPOP_REQUEST);
 117         MACPY(d->myea, ah->arp_sha);
 118         bcopy(&d->myip, ah->arp_spa, sizeof(ah->arp_spa));
 119         /* Leave zeros in arp_tha */
 120         bcopy(&addr, ah->arp_tpa, sizeof(ah->arp_tpa));
 121
 122         /* Store ip address in cache (incomplete entry). */
 123         al->addr = addr;
 124
 125         i = sendrecv(d,
 126             arpsend, &wbuf.data, sizeof(wbuf.data),
 127             arprecv, &rbuf.data, sizeof(rbuf.data));
 128         if (i == -1) {
 129                 panic("arp: no response for %s\n",
 130                           inet_ntoa(addr));
 131         }
 132
 133         /* Store ethernet address in cache */
 134         ah = &rbuf.data.arp;
 135 #ifdef ARP_DEBUG
 136         if (debug) {
 137                 printf("arp: response from %s\n",
 138                     ether_sprintf(rbuf.eh.ether_shost));
 139                 printf("arp: cacheing %s --> %s\n",
 140                     inet_ntoa(addr), ether_sprintf(ah->arp_sha));
 141         }
 142 #endif
 143         MACPY(ah->arp_sha, al->ea);
 144         ++arp_num;
 145
 146         return (al->ea);
 147 }
 148
 149 static ssize_t
 150 arpsend(d, pkt, len)
 151         struct iodesc *d;
 152         void *pkt;
 153         size_t len;
 154 {
 155
 156 #ifdef ARP_DEBUG
 157         if (debug)
 158                 printf("arpsend: called\n");
 159 #endif
 160
 161         return (sendether(d, pkt, len, bcea, ETHERTYPE_ARP));
 162 }
 163
 164 /*
 165  * Returns 0 if this is the packet we're waiting for
 166  * else -1 (and errno == 0)
 167  */
 168 static ssize_t
 169 arprecv(d, pkt, len, tleft)
 170         struct iodesc *d;
 171         void *pkt;
 172         size_t len;
 173         time_t tleft;
 174 {
 175         ssize_t n;
 176         struct ether_arp *ah;
 177         u_int16_t etype;        /* host order */
 178
 179 #ifdef ARP_DEBUG
 180         if (debug)
 181                 printf("arprecv: ");
 182 #endif
 183
 184         n = readether(d, pkt, len, tleft, &etype);
 185         errno = 0;      /* XXX */
 186         if (n == -1 || n < sizeof(struct ether_arp)) {
 187 #ifdef ARP_DEBUG
 188                 if (debug)
 189                         printf("bad len=%d\n", n);
 190 #endif
 191                 return (-1);
 192         }
 193
 194         if (etype != ETHERTYPE_ARP) {
 195 #ifdef ARP_DEBUG
 196                 if (debug)
 197                         printf("not arp type=%d\n", etype);
 198 #endif
 199                 return (-1);
 200         }
 201
 202         /* Ethernet address now checked in readether() */
 203
 204         ah = (struct ether_arp *)pkt;
 205         if (ah->arp_hrd != htons(ARPHRD_ETHER) ||
 206             ah->arp_pro != htons(ETHERTYPE_IP) ||
 207             ah->arp_hln != sizeof(ah->arp_sha) ||
 208             ah->arp_pln != sizeof(ah->arp_spa) )
 209         {
 210 #ifdef ARP_DEBUG
 211                 if (debug)
 212                         printf("bad hrd/pro/hln/pln\n");
 213 #endif
 214                 return (-1);
 215         }
 216
 217         if (ah->arp_op == htons(ARPOP_REQUEST)) {
 218 #ifdef ARP_DEBUG
 219                 if (debug)
 220                         printf("is request\n");
 221 #endif
 222                 arp_reply(d, ah);
 223                 return (-1);
 224         }
 225
 226         if (ah->arp_op != htons(ARPOP_REPLY)) {
 227 #ifdef ARP_DEBUG
 228                 if (debug)
 229                         printf("not ARP reply\n");
 230 #endif
 231                 return (-1);
 232         }
 233
 234         /* Is the reply from the source we want? */
 235         if (bcmp(&arp_list[arp_num].addr,
 236                          ah->arp_spa, sizeof(ah->arp_spa)))
 237         {
 238 #ifdef ARP_DEBUG
 239                 if (debug)
 240                         printf("unwanted address\n");
 241 #endif
 242                 return (-1);
 243         }
 244         /* We don't care who the reply was sent to. */
 245
 246         /* We have our answer. */
 247 #ifdef ARP_DEBUG
 248         if (debug)
 249                 printf("got it\n");
 250 #endif
 251         return (n);
 252 }
 253
 254 /*
 255  * Convert an ARP request into a reply and send it.
 256  * Notes:  Re-uses buffer.  Pad to length = 46.
 257  */
 258 void
 259 arp_reply(d, pkt)
 260         struct iodesc *d;
 261         void *pkt;              /* the request */
 262 {
 263         struct ether_arp *arp = pkt;
 264
 265         if (arp->arp_hrd != htons(ARPHRD_ETHER) ||
 266             arp->arp_pro != htons(ETHERTYPE_IP) ||
 267             arp->arp_hln != sizeof(arp->arp_sha) ||
 268             arp->arp_pln != sizeof(arp->arp_spa) )
 269         {
 270 #ifdef ARP_DEBUG
 271                 if (debug)
 272                         printf("arp_reply: bad hrd/pro/hln/pln\n");
 273 #endif
 274                 return;
 275         }
 276
 277         if (arp->arp_op != htons(ARPOP_REQUEST)) {
 278 #ifdef ARP_DEBUG
 279                 if (debug)
 280                         printf("arp_reply: not request!\n");
 281 #endif
 282                 return;
 283         }
 284
 285         /* If we are not the target, ignore the request. */
 286         if (bcmp(arp->arp_tpa, &d->myip, sizeof(arp->arp_tpa)))
 287                 return;
 288
 289 #ifdef ARP_DEBUG
 290         if (debug) {
 291                 printf("arp_reply: to %s\n", ether_sprintf(arp->arp_sha));
 292         }
 293 #endif
 294
 295         arp->arp_op = htons(ARPOP_REPLY);
 296         /* source becomes target */
 297         bcopy(arp->arp_sha, arp->arp_tha, sizeof(arp->arp_tha));
 298         bcopy(arp->arp_spa, arp->arp_tpa, sizeof(arp->arp_tpa));
 299         /* here becomes source */
 300         bcopy(d->myea,  arp->arp_sha, sizeof(arp->arp_sha));
 301         bcopy(&d->myip, arp->arp_spa, sizeof(arp->arp_spa));
 302
 303         /*
 304          * No need to get fancy here.  If the send fails, the
 305          * requestor will just ask again.
 306          */
 307         (void) sendether(d, pkt, sizeof(*arp) + 18,
 308                          arp->arp_tha, ETHERTYPE_ARP);
 309 }