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 * $FreeBSD: head/contrib/tcpdump/print-arp.c 98527 2002-06-21 00:49:02Z fenner $
22 */
23
24#ifndef lint
25static const char rcsid[] =
26 "@(#) $Header: /tcpdump/master/tcpdump/print-arp.c,v 1.51 2001/09/17 21:57:54 fenner Exp $ (LBL)";
27#endif
28
29#ifdef HAVE_CONFIG_H
30#include "config.h"
31#endif
32
33#include <sys/param.h>
34#include <sys/time.h>
35
36#include <netinet/in.h>
37
38#include <stdio.h>
39#include <string.h>
40
41#include "interface.h"
42#include "addrtoname.h"
43#include "ether.h"
44#include "ethertype.h"
45#include "extract.h" /* must come after interface.h */
46
47/*
48 * Address Resolution Protocol.
49 *
50 * See RFC 826 for protocol description. ARP packets are variable
51 * in size; the arphdr structure defines the fixed-length portion.
52 * Protocol type values are the same as those for 10 Mb/s Ethernet.
53 * It is followed by the variable-sized fields ar_sha, arp_spa,
54 * arp_tha and arp_tpa in that order, according to the lengths
55 * specified. Field names used correspond to RFC 826.
56 */
57struct arphdr {
58 u_short ar_hrd; /* format of hardware address */
59#define ARPHRD_ETHER 1 /* ethernet hardware format */
60#define ARPHRD_IEEE802 6 /* token-ring hardware format */
61#define ARPHRD_ARCNET 7 /* arcnet hardware format */
62#define ARPHRD_FRELAY 15 /* frame relay hardware format */
63#define ARPHRD_STRIP 23 /* Ricochet Starmode Radio hardware format */
64#define ARPHRD_IEEE1394 24 /* IEEE 1394 (FireWire) 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#define ar_sha(ap) (((const caddr_t)((ap)+1))+0)
86#define ar_spa(ap) (((const caddr_t)((ap)+1))+ (ap)->ar_hln)
87#define ar_tha(ap) (((const caddr_t)((ap)+1))+ (ap)->ar_hln+(ap)->ar_pln)
88#define ar_tpa(ap) (((const caddr_t)((ap)+1))+2*(ap)->ar_hln+(ap)->ar_pln)
89};
90
91#define ARP_HDRLEN 8
92
93#define HRD(ap) ((ap)->ar_hrd)
94#define HLN(ap) ((ap)->ar_hln)
95#define PLN(ap) ((ap)->ar_pln)
96#define OP(ap) ((ap)->ar_op)
97#define PRO(ap) ((ap)->ar_pro)
98#define SHA(ap) (ar_sha(ap))
99#define SPA(ap) (ar_spa(ap))
100#define THA(ap) (ar_tha(ap))
101#define TPA(ap) (ar_tpa(ap))
102
103static u_char ezero[6];
104
105void
106arp_print(const u_char *bp, u_int length, u_int caplen)
107{
108 const struct arphdr *ap;
109 u_short pro, hrd, op;
110
111 ap = (const struct arphdr *)bp;
112 TCHECK(*ap);
113 if ((const u_char *)(ar_tpa(ap) + PLN(ap)) > snapend) {
114 (void)printf("truncated-arp");
115 default_print((const u_char *)ap, length);
116 return;
117 }
118
119 pro = EXTRACT_16BITS(&PRO(ap));
120 hrd = EXTRACT_16BITS(&HRD(ap));
121 op = EXTRACT_16BITS(&OP(ap));
122
123 if (pro != ETHERTYPE_IP && pro != ETHERTYPE_TRAIL) {
124 (void)printf("arp-#%d for proto #%d (%d) hardware #%d (%d)",
125 op, pro, PLN(ap), hrd, HLN(ap));
126 return;
127 }
128 if (pro == ETHERTYPE_TRAIL)
129 (void)printf("trailer-");
130 switch (op) {
131
132 case ARPOP_REQUEST:
133 (void)printf("arp who-has %s", ipaddr_string(TPA(ap)));
134 if (memcmp((const char *)ezero, (const char *)THA(ap), HLN(ap)) != 0)
135 (void)printf(" (%s)",
136 linkaddr_string(THA(ap), HLN(ap)));
137 (void)printf(" tell %s", ipaddr_string(SPA(ap)));
138 break;
139
140 case ARPOP_REPLY:
141 (void)printf("arp reply %s", ipaddr_string(SPA(ap)));
142 (void)printf(" is-at %s", linkaddr_string(SHA(ap), HLN(ap)));
143 break;
144
145 case ARPOP_REVREQUEST:
146 (void)printf("rarp who-is %s tell %s",
147 linkaddr_string(THA(ap), HLN(ap)),
148 linkaddr_string(SHA(ap), HLN(ap)));
149 break;
150
151 case ARPOP_REVREPLY:
152 (void)printf("rarp reply %s at %s",
153 linkaddr_string(THA(ap), HLN(ap)),
154 ipaddr_string(TPA(ap)));
155 break;
156
157 default:
158 (void)printf("arp-#%d", op);
159 default_print((const u_char *)ap, caplen);
160 return;
161 }
162 if (hrd != ARPHRD_ETHER)
163 printf(" hardware #%d", hrd);
164 return;
165trunc:
166 (void)printf("[|arp]");
167}