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 1.48 2000-10-09 03:24:25 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 #include <stdio.h>
  36 #include <string.h>
  37
  38 #include "interface.h"
  39 #include "addrtoname.h"
  40 #include "ether.h"
  41 #include "ethertype.h"
  42 #include "extract.h"                    /* must come after interface.h */
  43
  44 /*
  45  * Address Resolution Protocol.
  46  *
  47  * See RFC 826 for protocol description.  ARP packets are variable
  48  * in size; the arphdr structure defines the fixed-length portion.
  49  * Protocol type values are the same as those for 10 Mb/s Ethernet.
  50  * It is followed by the variable-sized fields ar_sha, arp_spa,
  51  * arp_tha and arp_tpa in that order, according to the lengths
  52  * specified.  Field names used correspond to RFC 826.
  53  */
  54 struct  arphdr {
  55         u_short ar_hrd;         /* format of hardware address */
  56 #define ARPHRD_ETHER    1       /* ethernet hardware format */
  57 #define ARPHRD_IEEE802  6       /* token-ring hardware format */
  58 #define ARPHRD_FRELAY   15      /* frame relay hardware format */
  59         u_short ar_pro;         /* format of protocol address */
  60         u_char  ar_hln;         /* length of hardware address */
  61         u_char  ar_pln;         /* length of protocol address */
  62         u_short ar_op;          /* one of: */
  63 #define ARPOP_REQUEST   1       /* request to resolve address */
  64 #define ARPOP_REPLY     2       /* response to previous request */
  65 #define ARPOP_REVREQUEST 3      /* request protocol address given hardware */
  66 #define ARPOP_REVREPLY  4       /* response giving protocol address */
  67 #define ARPOP_INVREQUEST 8      /* request to identify peer */
  68 #define ARPOP_INVREPLY  9       /* response identifying peer */
  69 /*
  70  * The remaining fields are variable in size,
  71  * according to the sizes above.
  72  */
  73 #ifdef COMMENT_ONLY
  74         u_char  ar_sha[];       /* sender hardware address */
  75         u_char  ar_spa[];       /* sender protocol address */
  76         u_char  ar_tha[];       /* target hardware address */
  77         u_char  ar_tpa[];       /* target protocol address */
  78 #endif
  79 };
  80
  81 #define ARP_HDRLEN      8
  82
  83 /*
  84  * Ethernet Address Resolution Protocol.
  85  *
  86  * See RFC 826 for protocol description.  Structure below is adapted
  87  * to resolving internet addresses.  Field names used correspond to
  88  * RFC 826.
  89  */
  90 struct  ether_arp {
  91         struct  arphdr ea_hdr;  /* fixed-size header */
  92         u_char  arp_sha[6];     /* sender hardware address */
  93         u_char  arp_spa[4];     /* sender protocol address */
  94         u_char  arp_tha[6];     /* target hardware address */
  95         u_char  arp_tpa[4];     /* target protocol address */
  96 };
  97 #define arp_hrd ea_hdr.ar_hrd
  98 #define arp_pro ea_hdr.ar_pro
  99 #define arp_hln ea_hdr.ar_hln
 100 #define arp_pln ea_hdr.ar_pln
 101 #define arp_op  ea_hdr.ar_op
 102
 103 #define ETHER_ARP_HDRLEN        (ARP_HDRLEN + 6 + 4 + 6 + 4)
 104
 105 #define SHA(ap) ((ap)->arp_sha)
 106 #define THA(ap) ((ap)->arp_tha)
 107 #define SPA(ap) ((ap)->arp_spa)
 108 #define TPA(ap) ((ap)->arp_tpa)
 109
 110 /* Compatibility */
 111 #ifndef REVARP_REQUEST
 112 #define REVARP_REQUEST          3
 113 #endif
 114 #ifndef REVARP_REPLY
 115 #define REVARP_REPLY            4
 116 #endif
 117
 118 static u_char ezero[6];
 119
 120 void
 121 arp_print(register const u_char *bp, u_int length, u_int caplen)
 122 {
 123         register const struct ether_arp *ap;
 124         register const struct ether_header *eh;
 125         register u_short pro, hrd, op;
 126
 127         ap = (struct ether_arp *)bp;
 128         if ((u_char *)(ap + 1) > snapend) {
 129                 printf("[|arp]");
 130                 return;
 131         }
 132         if (length < ETHER_ARP_HDRLEN) {
 133                 (void)printf("truncated-arp");
 134                 default_print((u_char *)ap, length);
 135                 return;
 136         }
 137
 138         pro = EXTRACT_16BITS(&ap->arp_pro);
 139         hrd = EXTRACT_16BITS(&ap->arp_hrd);
 140         op = EXTRACT_16BITS(&ap->arp_op);
 141
 142         if ((pro != ETHERTYPE_IP && pro != ETHERTYPE_TRAIL)
 143             || ap->arp_hln != sizeof(SHA(ap))
 144             || ap->arp_pln != sizeof(SPA(ap))) {
 145                 (void)printf("arp-#%d for proto #%d (%d) hardware #%d (%d)",
 146                                 op, pro, ap->arp_pln,
 147                                 hrd, ap->arp_hln);
 148                 return;
 149         }
 150         if (pro == ETHERTYPE_TRAIL)
 151                 (void)printf("trailer-");
 152         eh = (struct ether_header *)packetp;
 153         switch (op) {
 154
 155         case ARPOP_REQUEST:
 156                 (void)printf("arp who-has %s", ipaddr_string(TPA(ap)));
 157                 if (memcmp((char *)ezero, (char *)THA(ap), 6) != 0)
 158                         (void)printf(" (%s)", etheraddr_string(THA(ap)));
 159                 (void)printf(" tell %s", ipaddr_string(SPA(ap)));
 160                 if (memcmp((char *)ESRC(eh), (char *)SHA(ap), 6) != 0)
 161                         (void)printf(" (%s)", etheraddr_string(SHA(ap)));
 162                 break;
 163
 164         case ARPOP_REPLY:
 165                 (void)printf("arp reply %s", ipaddr_string(SPA(ap)));
 166                 if (memcmp((char *)ESRC(eh), (char *)SHA(ap), 6) != 0)
 167                         (void)printf(" (%s)", etheraddr_string(SHA(ap)));
 168                 (void)printf(" is-at %s", etheraddr_string(SHA(ap)));
 169                 if (memcmp((char *)EDST(eh), (char *)THA(ap), 6) != 0)
 170                         (void)printf(" (%s)", etheraddr_string(THA(ap)));
 171                 break;
 172
 173         case REVARP_REQUEST:
 174                 (void)printf("rarp who-is %s tell %s",
 175                         etheraddr_string(THA(ap)),
 176                         etheraddr_string(SHA(ap)));
 177                 break;
 178
 179         case REVARP_REPLY:
 180                 (void)printf("rarp reply %s at %s",
 181                         etheraddr_string(THA(ap)),
 182                         ipaddr_string(TPA(ap)));
 183                 break;
 184
 185         default:
 186                 (void)printf("arp-#%d", op);
 187                 default_print((u_char *)ap, caplen);
 188                 return;
 189         }
 190         if (hrd != ARPHRD_ETHER)
 191                 printf(" hardware #%d", hrd);
 192 }