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 1.52 2002-02-25 09:40:32 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  arp_pkthdr {
  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_ARCNET   7       /* arcnet hardware format */
  60 #define ARPHRD_FRELAY   15      /* frame relay hardware format */
  61 #define ARPHRD_STRIP    23      /* Ricochet Starmode Radio hardware format */
  62 #define ARPHRD_IEEE1394 24      /* IEEE 1394 (FireWire) hardware format */
  63         u_short ar_pro;         /* format of protocol address */
  64         u_char  ar_hln;         /* length of hardware address */
  65         u_char  ar_pln;         /* length of protocol address */
  66         u_short ar_op;          /* one of: */
  67 #define ARPOP_REQUEST   1       /* request to resolve address */
  68 #define ARPOP_REPLY     2       /* response to previous request */
  69 #define ARPOP_REVREQUEST 3      /* request protocol address given hardware */
  70 #define ARPOP_REVREPLY  4       /* response giving protocol address */
  71 #define ARPOP_INVREQUEST 8      /* request to identify peer */
  72 #define ARPOP_INVREPLY  9       /* response identifying peer */
  73 /*
  74  * The remaining fields are variable in size,
  75  * according to the sizes above.
  76  */
  77 #ifdef COMMENT_ONLY
  78         u_char  ar_sha[];       /* sender hardware address */
  79         u_char  ar_spa[];       /* sender protocol address */
  80         u_char  ar_tha[];       /* target hardware address */
  81         u_char  ar_tpa[];       /* target protocol address */
  82 #endif
  83 #define ar_sha(ap)      (((const caddr_t)((ap)+1))+0)
  84 #define ar_spa(ap)      (((const caddr_t)((ap)+1))+  (ap)->ar_hln)
  85 #define ar_tha(ap)      (((const caddr_t)((ap)+1))+  (ap)->ar_hln+(ap)->ar_pln)
  86 #define ar_tpa(ap)      (((const caddr_t)((ap)+1))+2*(ap)->ar_hln+(ap)->ar_pln)
  87 };
  88
  89 #define ARP_HDRLEN      8
  90
  91 #define HRD(ap) ((ap)->ar_hrd)
  92 #define HLN(ap) ((ap)->ar_hln)
  93 #define PLN(ap) ((ap)->ar_pln)
  94 #define OP(ap)  ((ap)->ar_op)
  95 #define PRO(ap) ((ap)->ar_pro)
  96 #define SHA(ap) (ar_sha(ap))
  97 #define SPA(ap) (ar_spa(ap))
  98 #define THA(ap) (ar_tha(ap))
  99 #define TPA(ap) (ar_tpa(ap))
 100
 101 static u_char ezero[6];
 102
 103 void
 104 arp_print(const u_char *bp, u_int length, u_int caplen)
 105 {
 106         const struct arp_pkthdr *ap;
 107         u_short pro, hrd, op;
 108
 109         ap = (const struct arp_pkthdr *)bp;
 110         TCHECK(*ap);
 111         if ((const u_char *)(ar_tpa(ap) + PLN(ap)) > snapend) {
 112                 (void)printf("truncated-arp");
 113                 default_print((const u_char *)ap, length);
 114                 return;
 115         }
 116
 117         pro = EXTRACT_16BITS(&PRO(ap));
 118         hrd = EXTRACT_16BITS(&HRD(ap));
 119         op = EXTRACT_16BITS(&OP(ap));
 120
 121         if (pro != ETHERTYPE_IP && pro != ETHERTYPE_TRAIL) {
 122                 (void)printf("arp-#%d for proto #%d (%d) hardware #%d (%d)",
 123                                 op, pro, PLN(ap), hrd, HLN(ap));
 124                 return;
 125         }
 126         if (pro == ETHERTYPE_TRAIL)
 127                 (void)printf("trailer-");
 128         switch (op) {
 129
 130         case ARPOP_REQUEST:
 131                 (void)printf("arp who-has %s", ipaddr_string(TPA(ap)));
 132                 if (memcmp((const char *)ezero, (const char *)THA(ap), HLN(ap)) != 0)
 133                         (void)printf(" (%s)",
 134                             linkaddr_string(THA(ap), HLN(ap)));
 135                 (void)printf(" tell %s", ipaddr_string(SPA(ap)));
 136                 break;
 137
 138         case ARPOP_REPLY:
 139                 (void)printf("arp reply %s", ipaddr_string(SPA(ap)));
 140                 (void)printf(" is-at %s", linkaddr_string(SHA(ap), HLN(ap)));
 141                 break;
 142
 143         case ARPOP_REVREQUEST:
 144                 (void)printf("rarp who-is %s tell %s",
 145                         linkaddr_string(THA(ap), HLN(ap)),
 146                         linkaddr_string(SHA(ap), HLN(ap)));
 147                 break;
 148
 149         case ARPOP_REVREPLY:
 150                 (void)printf("rarp reply %s at %s",
 151                         linkaddr_string(THA(ap), HLN(ap)),
 152                         ipaddr_string(TPA(ap)));
 153                 break;
 154
 155         default:
 156                 (void)printf("arp-#%d", op);
 157                 default_print((const u_char *)ap, caplen);
 158                 return;
 159         }
 160         if (hrd != ARPHRD_ETHER)
 161                 printf(" hardware #%d", hrd);
 162         return;
 163 trunc:
 164         (void)printf("[|arp]");
 165 }