print-arp.c revision 111729 
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 111729 2003-03-02 08:25:48Z fenner $
22 */
23
24#ifndef lint
25static const char rcsid[] =
26    "@(#) $Header: /tcpdump/master/tcpdump/print-arp.c,v 1.51.4.2 2002/07/10 07:09:53 guy 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	arp_pkthdr {
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 u_char *)((ap)+1))+0)
86#define ar_spa(ap)	(((const u_char *)((ap)+1))+  (ap)->ar_hln)
87#define ar_tha(ap)	(((const u_char *)((ap)+1))+  (ap)->ar_hln+(ap)->ar_pln)
88#define ar_tpa(ap)	(((const u_char *)((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 arp_pkthdr *ap;
109	u_short pro, hrd, op;
110
111	ap = (const struct arp_pkthdr *)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}
168