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 1.49 2000-10-10 05:05:07 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
  34 #include <netinet/in.h>
  35
  36 #include <stdio.h>
  37 #include <string.h>
  38
  39 #include "interface.h"
  40 #include "addrtoname.h"
  41 #include "ether.h"
  42 #include "ethertype.h"
  43 #include "extract.h"                    /* must come after interface.h */
  44
  45 /*
  46  * Address Resolution Protocol.
  47  *
  48  * See RFC 826 for protocol description.  ARP packets are variable
  49  * in size; the arphdr structure defines the fixed-length portion.
  50  * Protocol type values are the same as those for 10 Mb/s Ethernet.
  51  * It is followed by the variable-sized fields ar_sha, arp_spa,
  52  * arp_tha and arp_tpa in that order, according to the lengths
  53  * specified.  Field names used correspond to RFC 826.
  54  */
  55 struct  arphdr {
  56         u_short ar_hrd;         /* format of hardware address */
  57 #define ARPHRD_ETHER    1       /* ethernet hardware format */
  58 #define ARPHRD_IEEE802  6       /* token-ring hardware format */
  59 #define ARPHRD_FRELAY   15      /* frame relay hardware format */
  60         u_short ar_pro;         /* format of protocol address */
  61         u_char  ar_hln;         /* length of hardware address */
  62         u_char  ar_pln;         /* length of protocol address */
  63         u_short ar_op;          /* one of: */
  64 #define ARPOP_REQUEST   1       /* request to resolve address */
  65 #define ARPOP_REPLY     2       /* response to previous request */
  66 #define ARPOP_REVREQUEST 3      /* request protocol address given hardware */
  67 #define ARPOP_REVREPLY  4       /* response giving protocol address */
  68 #define ARPOP_INVREQUEST 8      /* request to identify peer */
  69 #define ARPOP_INVREPLY  9       /* response identifying peer */
  70 /*
  71  * The remaining fields are variable in size,
  72  * according to the sizes above.
  73  */
  74 #ifdef COMMENT_ONLY
  75         u_char  ar_sha[];       /* sender hardware address */
  76         u_char  ar_spa[];       /* sender protocol address */
  77         u_char  ar_tha[];       /* target hardware address */
  78         u_char  ar_tpa[];       /* target protocol address */
  79 #endif
  80 };
  81
  82 #define ARP_HDRLEN      8
  83
  84 /*
  85  * Ethernet Address Resolution Protocol.
  86  *
  87  * See RFC 826 for protocol description.  Structure below is adapted
  88  * to resolving internet addresses.  Field names used correspond to
  89  * RFC 826.
  90  */
  91 struct  ether_arp {
  92         struct  arphdr ea_hdr;  /* fixed-size header */
  93         u_char  arp_sha[6];     /* sender hardware address */
  94         u_char  arp_spa[4];     /* sender protocol address */
  95         u_char  arp_tha[6];     /* target hardware address */
  96         u_char  arp_tpa[4];     /* target protocol address */
  97 };
  98 #define arp_hrd ea_hdr.ar_hrd
  99 #define arp_pro ea_hdr.ar_pro
 100 #define arp_hln ea_hdr.ar_hln
 101 #define arp_pln ea_hdr.ar_pln
 102 #define arp_op  ea_hdr.ar_op
 103
 104 #define ETHER_ARP_HDRLEN        (ARP_HDRLEN + 6 + 4 + 6 + 4)
 105
 106 #define SHA(ap) ((ap)->arp_sha)
 107 #define THA(ap) ((ap)->arp_tha)
 108 #define SPA(ap) ((ap)->arp_spa)
 109 #define TPA(ap) ((ap)->arp_tpa)
 110
 111 /* Compatibility */
 112 #ifndef REVARP_REQUEST
 113 #define REVARP_REQUEST          3
 114 #endif
 115 #ifndef REVARP_REPLY
 116 #define REVARP_REPLY            4
 117 #endif
 118
 119 static u_char ezero[6];
 120
 121 void
 122 arp_print(register const u_char *bp, u_int length, u_int caplen)
 123 {
 124         register const struct ether_arp *ap;
 125         register const struct ether_header *eh;
 126         register u_short pro, hrd, op;
 127
 128         ap = (struct ether_arp *)bp;
 129         if ((u_char *)(ap + 1) > snapend) {
 130                 printf("[|arp]");
 131                 return;
 132         }
 133         if (length < ETHER_ARP_HDRLEN) {
 134                 (void)printf("truncated-arp");
 135                 default_print((u_char *)ap, length);
 136                 return;
 137         }
 138
 139         pro = EXTRACT_16BITS(&ap->arp_pro);
 140         hrd = EXTRACT_16BITS(&ap->arp_hrd);
 141         op = EXTRACT_16BITS(&ap->arp_op);
 142
 143         if ((pro != ETHERTYPE_IP && pro != ETHERTYPE_TRAIL)
 144             || ap->arp_hln != sizeof(SHA(ap))
 145             || ap->arp_pln != sizeof(SPA(ap))) {
 146                 (void)printf("arp-#%d for proto #%d (%d) hardware #%d (%d)",
 147                                 op, pro, ap->arp_pln,
 148                                 hrd, ap->arp_hln);
 149                 return;
 150         }
 151         if (pro == ETHERTYPE_TRAIL)
 152                 (void)printf("trailer-");
 153         eh = (struct ether_header *)packetp;
 154         switch (op) {
 155
 156         case ARPOP_REQUEST:
 157                 (void)printf("arp who-has %s", ipaddr_string(TPA(ap)));
 158                 if (memcmp((char *)ezero, (char *)THA(ap), 6) != 0)
 159                         (void)printf(" (%s)", etheraddr_string(THA(ap)));
 160                 (void)printf(" tell %s", ipaddr_string(SPA(ap)));
 161                 if (memcmp((char *)ESRC(eh), (char *)SHA(ap), 6) != 0)
 162                         (void)printf(" (%s)", etheraddr_string(SHA(ap)));
 163                 break;
 164
 165         case ARPOP_REPLY:
 166                 (void)printf("arp reply %s", ipaddr_string(SPA(ap)));
 167                 if (memcmp((char *)ESRC(eh), (char *)SHA(ap), 6) != 0)
 168                         (void)printf(" (%s)", etheraddr_string(SHA(ap)));
 169                 (void)printf(" is-at %s", etheraddr_string(SHA(ap)));
 170                 if (memcmp((char *)EDST(eh), (char *)THA(ap), 6) != 0)
 171                         (void)printf(" (%s)", etheraddr_string(THA(ap)));
 172                 break;
 173
 174         case REVARP_REQUEST:
 175                 (void)printf("rarp who-is %s tell %s",
 176                         etheraddr_string(THA(ap)),
 177                         etheraddr_string(SHA(ap)));
 178                 break;
 179
 180         case REVARP_REPLY:
 181                 (void)printf("rarp reply %s at %s",
 182                         etheraddr_string(THA(ap)),
 183                         ipaddr_string(TPA(ap)));
 184                 break;
 185
 186         default:
 187                 (void)printf("arp-#%d", op);
 188                 default_print((u_char *)ap, caplen);
 189                 return;
 190         }
 191         if (hrd != ARPHRD_ETHER)
 192                 printf(" hardware #%d", hrd);
 193 }