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. 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  * $DragonFly: src/lib/libstand/arp.c,v 1.4 2005/12/11 02:27:26 swildner Exp $
  41  */
  42
  43 #include <sys/param.h>
  44 #include <sys/socket.h>
  45 #include <net/if.h>
  46 #include <netinet/in.h>
  47 #include <netinet/if_ether.h>
  48
  49 #include <netinet/in_systm.h>
  50
  51 #include <string.h>
  52
  53 #include "stand.h"
  54 #include "net.h"
  55
  56 /* Cache stuff */
  57 #define ARP_NUM 8                       /* need at most 3 arp entries */
  58
  59 struct arp_list {
  60         struct in_addr  addr;
  61         u_char          ea[6];
  62 } arp_list[ARP_NUM] = {
  63         /* XXX - net order `INADDR_BROADCAST' must be a constant */
  64         { {0xffffffff}, BA }
  65 };
  66 int arp_num = 1;
  67
  68 /* Local forwards */
  69 static  ssize_t arpsend(struct iodesc *, void *, size_t);
  70 static  ssize_t arprecv(struct iodesc *, void *, size_t, time_t);
  71
  72 /* Broadcast an ARP packet, asking who has addr on interface d */
  73 u_char *
  74 arpwhohas(struct iodesc *d, 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(struct iodesc *d, void *pkt, size_t len)
 151 {
 152
 153 #ifdef ARP_DEBUG
 154         if (debug)
 155                 printf("arpsend: called\n");
 156 #endif
 157
 158         return (sendether(d, pkt, len, bcea, ETHERTYPE_ARP));
 159 }
 160
 161 /*
 162  * Returns 0 if this is the packet we're waiting for
 163  * else -1 (and errno == 0)
 164  */
 165 static ssize_t
 166 arprecv(struct iodesc *d, void *pkt, size_t len, time_t tleft)
 167 {
 168         ssize_t n;
 169         struct ether_arp *ah;
 170         u_int16_t etype;        /* host order */
 171
 172 #ifdef ARP_DEBUG
 173         if (debug)
 174                 printf("arprecv: ");
 175 #endif
 176
 177         n = readether(d, pkt, len, tleft, &etype);
 178         errno = 0;      /* XXX */
 179         if (n == -1 || n < sizeof(struct ether_arp)) {
 180 #ifdef ARP_DEBUG
 181                 if (debug)
 182                         printf("bad len=%d\n", n);
 183 #endif
 184                 return (-1);
 185         }
 186
 187         if (etype != ETHERTYPE_ARP) {
 188 #ifdef ARP_DEBUG
 189                 if (debug)
 190                         printf("not arp type=%d\n", etype);
 191 #endif
 192                 return (-1);
 193         }
 194
 195         /* Ethernet address now checked in readether() */
 196
 197         ah = (struct ether_arp *)pkt;
 198         if (ah->arp_hrd != htons(ARPHRD_ETHER) ||
 199             ah->arp_pro != htons(ETHERTYPE_IP) ||
 200             ah->arp_hln != sizeof(ah->arp_sha) ||
 201             ah->arp_pln != sizeof(ah->arp_spa) )
 202         {
 203 #ifdef ARP_DEBUG
 204                 if (debug)
 205                         printf("bad hrd/pro/hln/pln\n");
 206 #endif
 207                 return (-1);
 208         }
 209
 210         if (ah->arp_op == htons(ARPOP_REQUEST)) {
 211 #ifdef ARP_DEBUG
 212                 if (debug)
 213                         printf("is request\n");
 214 #endif
 215                 arp_reply(d, ah);
 216                 return (-1);
 217         }
 218
 219         if (ah->arp_op != htons(ARPOP_REPLY)) {
 220 #ifdef ARP_DEBUG
 221                 if (debug)
 222                         printf("not ARP reply\n");
 223 #endif
 224                 return (-1);
 225         }
 226
 227         /* Is the reply from the source we want? */
 228         if (bcmp(&arp_list[arp_num].addr,
 229                          ah->arp_spa, sizeof(ah->arp_spa)))
 230         {
 231 #ifdef ARP_DEBUG
 232                 if (debug)
 233                         printf("unwanted address\n");
 234 #endif
 235                 return (-1);
 236         }
 237         /* We don't care who the reply was sent to. */
 238
 239         /* We have our answer. */
 240 #ifdef ARP_DEBUG
 241         if (debug)
 242                 printf("got it\n");
 243 #endif
 244         return (n);
 245 }
 246
 247 /*
 248  * Convert an ARP request into a reply and send it.
 249  * Notes:  Re-uses buffer.  Pad to length = 46.
 250  *
 251  * Parameters:
 252  *      pkt:    the request
 253  */
 254 void
 255 arp_reply(struct iodesc *d, void *pkt)
 256 {
 257         struct ether_arp *arp = pkt;
 258
 259         if (arp->arp_hrd != htons(ARPHRD_ETHER) ||
 260             arp->arp_pro != htons(ETHERTYPE_IP) ||
 261             arp->arp_hln != sizeof(arp->arp_sha) ||
 262             arp->arp_pln != sizeof(arp->arp_spa) )
 263         {
 264 #ifdef ARP_DEBUG
 265                 if (debug)
 266                         printf("arp_reply: bad hrd/pro/hln/pln\n");
 267 #endif
 268                 return;
 269         }
 270
 271         if (arp->arp_op != htons(ARPOP_REQUEST)) {
 272 #ifdef ARP_DEBUG
 273                 if (debug)
 274                         printf("arp_reply: not request!\n");
 275 #endif
 276                 return;
 277         }
 278
 279         /* If we are not the target, ignore the request. */
 280         if (bcmp(arp->arp_tpa, &d->myip, sizeof(arp->arp_tpa)))
 281                 return;
 282
 283 #ifdef ARP_DEBUG
 284         if (debug) {
 285                 printf("arp_reply: to %s\n", ether_sprintf(arp->arp_sha));
 286         }
 287 #endif
 288
 289         arp->arp_op = htons(ARPOP_REPLY);
 290         /* source becomes target */
 291         bcopy(arp->arp_sha, arp->arp_tha, sizeof(arp->arp_tha));
 292         bcopy(arp->arp_spa, arp->arp_tpa, sizeof(arp->arp_tpa));
 293         /* here becomes source */
 294         bcopy(d->myea,  arp->arp_sha, sizeof(arp->arp_sha));
 295         bcopy(&d->myip, arp->arp_spa, sizeof(arp->arp_spa));
 296
 297         /*
 298          * No need to get fancy here.  If the send fails, the
 299          * requestor will just ask again.
 300          */
 301         (void) sendether(d, pkt, sizeof(*arp) + 18,
 302                          arp->arp_tha, ETHERTYPE_ARP);
 303 }