The Tcpdump Group git mirrors - tcpdump/blob - print-arp.c

   1 /*
   2  * Copyright (c) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that: (1) source code distributions
   7  * retain the above copyright notice and this paragraph in its entirety, (2)
   8  * distributions including binary code include the above copyright notice and
   9  * this paragraph in its entirety in the documentation or other materials
  10  * provided with the distribution, and (3) all advertising materials mentioning
  11  * features or use of this software display the following acknowledgement:
  12  * ``This product includes software developed by the University of California,
  13  * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
  14  * the University nor the names of its contributors may be used to endorse
  15  * or promote products derived from this software without specific prior
  16  * written permission.
  17  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
  18  * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
  19  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  20  */
  21
  22 #ifndef lint
  23 static const char rcsid[] =
  24     "@(#) $Header: /tcpdump/master/tcpdump/print-arp.c,v 1.46 2000-09-23 08:03:31 guy Exp $ (LBL)";
  25 #endif
  26
  27 #ifdef HAVE_CONFIG_H
  28 #include "config.h"
  29 #endif
  30
  31 #include <sys/param.h>
  32 #include <sys/time.h>
  33 #include <sys/socket.h>
  34
  35 struct mbuf;
  36 struct rtentry;
  37 #include <net/if.h>
  38
  39 #include <netinet/in.h>
  40
  41 #include <stdio.h>
  42 #include <string.h>
  43
  44 #include "interface.h"
  45 #include "addrtoname.h"
  46 #include "ether.h"
  47 #include "ethertype.h"
  48 #include "extract.h"                    /* must come after interface.h */
  49
  50 /*
  51  * Address Resolution Protocol.
  52  *
  53  * See RFC 826 for protocol description.  ARP packets are variable
  54  * in size; the arphdr structure defines the fixed-length portion.
  55  * Protocol type values are the same as those for 10 Mb/s Ethernet.
  56  * It is followed by the variable-sized fields ar_sha, arp_spa,
  57  * arp_tha and arp_tpa in that order, according to the lengths
  58  * specified.  Field names used correspond to RFC 826.
  59  */
  60 struct  arphdr {
  61         u_short ar_hrd;         /* format of hardware address */
  62 #define ARPHRD_ETHER    1       /* ethernet hardware format */
  63 #define ARPHRD_IEEE802  6       /* token-ring hardware format */
  64 #define ARPHRD_FRELAY   15      /* frame relay hardware format */
  65         u_short ar_pro;         /* format of protocol address */
  66         u_char  ar_hln;         /* length of hardware address */
  67         u_char  ar_pln;         /* length of protocol address */
  68         u_short ar_op;          /* one of: */
  69 #define ARPOP_REQUEST   1       /* request to resolve address */
  70 #define ARPOP_REPLY     2       /* response to previous request */
  71 #define ARPOP_REVREQUEST 3      /* request protocol address given hardware */
  72 #define ARPOP_REVREPLY  4       /* response giving protocol address */
  73 #define ARPOP_INVREQUEST 8      /* request to identify peer */
  74 #define ARPOP_INVREPLY  9       /* response identifying peer */
  75 /*
  76  * The remaining fields are variable in size,
  77  * according to the sizes above.
  78  */
  79 #ifdef COMMENT_ONLY
  80         u_char  ar_sha[];       /* sender hardware address */
  81         u_char  ar_spa[];       /* sender protocol address */
  82         u_char  ar_tha[];       /* target hardware address */
  83         u_char  ar_tpa[];       /* target protocol address */
  84 #endif
  85 };
  86
  87 /*
  88  * Ethernet Address Resolution Protocol.
  89  *
  90  * See RFC 826 for protocol description.  Structure below is adapted
  91  * to resolving internet addresses.  Field names used correspond to
  92  * RFC 826.
  93  */
  94 struct  ether_arp {
  95         struct  arphdr ea_hdr;  /* fixed-size header */
  96         u_char  arp_sha[6];     /* sender hardware address */
  97         u_char  arp_spa[4];     /* sender protocol address */
  98         u_char  arp_tha[6];     /* target hardware address */
  99         u_char  arp_tpa[4];     /* target protocol address */
 100 };
 101 #define arp_hrd ea_hdr.ar_hrd
 102 #define arp_pro ea_hdr.ar_pro
 103 #define arp_hln ea_hdr.ar_hln
 104 #define arp_pln ea_hdr.ar_pln
 105 #define arp_op  ea_hdr.ar_op
 106
 107 #define SHA(ap) ((ap)->arp_sha)
 108 #define THA(ap) ((ap)->arp_tha)
 109 #define SPA(ap) ((ap)->arp_spa)
 110 #define TPA(ap) ((ap)->arp_tpa)
 111
 112 /* Compatibility */
 113 #ifndef REVARP_REQUEST
 114 #define REVARP_REQUEST          3
 115 #endif
 116 #ifndef REVARP_REPLY
 117 #define REVARP_REPLY            4
 118 #endif
 119
 120 static u_char ezero[6];
 121
 122 void
 123 arp_print(register const u_char *bp, u_int length, u_int caplen)
 124 {
 125         register const struct ether_arp *ap;
 126         register const struct ether_header *eh;
 127         register u_short pro, hrd, op;
 128
 129         ap = (struct ether_arp *)bp;
 130         if ((u_char *)(ap + 1) > snapend) {
 131                 printf("[|arp]");
 132                 return;
 133         }
 134         if (length < sizeof(struct ether_arp)) {
 135                 (void)printf("truncated-arp");
 136                 default_print((u_char *)ap, length);
 137                 return;
 138         }
 139
 140         pro = EXTRACT_16BITS(&ap->arp_pro);
 141         hrd = EXTRACT_16BITS(&ap->arp_hrd);
 142         op = EXTRACT_16BITS(&ap->arp_op);
 143
 144         if ((pro != ETHERTYPE_IP && pro != ETHERTYPE_TRAIL)
 145             || ap->arp_hln != sizeof(SHA(ap))
 146             || ap->arp_pln != sizeof(SPA(ap))) {
 147                 (void)printf("arp-#%d for proto #%d (%d) hardware #%d (%d)",
 148                                 op, pro, ap->arp_pln,
 149                                 hrd, ap->arp_hln);
 150                 return;
 151         }
 152         if (pro == ETHERTYPE_TRAIL)
 153                 (void)printf("trailer-");
 154         eh = (struct ether_header *)packetp;
 155         switch (op) {
 156
 157         case ARPOP_REQUEST:
 158                 (void)printf("arp who-has %s", ipaddr_string(TPA(ap)));
 159                 if (memcmp((char *)ezero, (char *)THA(ap), 6) != 0)
 160                         (void)printf(" (%s)", etheraddr_string(THA(ap)));
 161                 (void)printf(" tell %s", ipaddr_string(SPA(ap)));
 162                 if (memcmp((char *)ESRC(eh), (char *)SHA(ap), 6) != 0)
 163                         (void)printf(" (%s)", etheraddr_string(SHA(ap)));
 164                 break;
 165
 166         case ARPOP_REPLY:
 167                 (void)printf("arp reply %s", ipaddr_string(SPA(ap)));
 168                 if (memcmp((char *)ESRC(eh), (char *)SHA(ap), 6) != 0)
 169                         (void)printf(" (%s)", etheraddr_string(SHA(ap)));
 170                 (void)printf(" is-at %s", etheraddr_string(SHA(ap)));
 171                 if (memcmp((char *)EDST(eh), (char *)THA(ap), 6) != 0)
 172                         (void)printf(" (%s)", etheraddr_string(THA(ap)));
 173                 break;
 174
 175         case REVARP_REQUEST:
 176                 (void)printf("rarp who-is %s tell %s",
 177                         etheraddr_string(THA(ap)),
 178                         etheraddr_string(SHA(ap)));
 179                 break;
 180
 181         case REVARP_REPLY:
 182                 (void)printf("rarp reply %s at %s",
 183                         etheraddr_string(THA(ap)),
 184                         ipaddr_string(TPA(ap)));
 185                 break;
 186
 187         default:
 188                 (void)printf("arp-#%d", op);
 189                 default_print((u_char *)ap, caplen);
 190                 return;
 191         }
 192         if (hrd != ARPHRD_ETHER)
 193                 printf(" hardware #%d", hrd);
 194 }