2 * Copyright (c) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997
3 * The Regents of the University of California. All rights reserved.
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
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.
25 static const char rcsid[] =
26 "@(#) $Header: /tcpdump/master/tcpdump/print-arp.c,v 1.49 2000/10/10 05:05:07 guy Exp $ (LBL)";
33 #include <sys/param.h>
36 #include <netinet/in.h>
41 #include "interface.h"
42 #include "addrtoname.h"
44 #include "ethertype.h"
45 #include "extract.h" /* must come after interface.h */
48 * Address Resolution Protocol.
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.
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_FRELAY 15 /* frame relay hardware format */
62 u_short ar_pro; /* format of protocol address */
63 u_char ar_hln; /* length of hardware address */
64 u_char ar_pln; /* length of protocol address */
65 u_short ar_op; /* one of: */
66 #define ARPOP_REQUEST 1 /* request to resolve address */
67 #define ARPOP_REPLY 2 /* response to previous request */
68 #define ARPOP_REVREQUEST 3 /* request protocol address given hardware */
69 #define ARPOP_REVREPLY 4 /* response giving protocol address */
70 #define ARPOP_INVREQUEST 8 /* request to identify peer */
71 #define ARPOP_INVREPLY 9 /* response identifying peer */
73 * The remaining fields are variable in size,
74 * according to the sizes above.
77 u_char ar_sha[]; /* sender hardware address */
78 u_char ar_spa[]; /* sender protocol address */
79 u_char ar_tha[]; /* target hardware address */
80 u_char ar_tpa[]; /* target protocol address */
87 * Ethernet Address Resolution Protocol.
89 * See RFC 826 for protocol description. Structure below is adapted
90 * to resolving internet addresses. Field names used correspond to
94 struct arphdr ea_hdr; /* fixed-size header */
95 u_char arp_sha[6]; /* sender hardware address */
96 u_char arp_spa[4]; /* sender protocol address */
97 u_char arp_tha[6]; /* target hardware address */
98 u_char arp_tpa[4]; /* target protocol address */
100 #define arp_hrd ea_hdr.ar_hrd
101 #define arp_pro ea_hdr.ar_pro
102 #define arp_hln ea_hdr.ar_hln
103 #define arp_pln ea_hdr.ar_pln
104 #define arp_op ea_hdr.ar_op
106 #define ETHER_ARP_HDRLEN (ARP_HDRLEN + 6 + 4 + 6 + 4)
108 #define SHA(ap) ((ap)->arp_sha)
109 #define THA(ap) ((ap)->arp_tha)
110 #define SPA(ap) ((ap)->arp_spa)
111 #define TPA(ap) ((ap)->arp_tpa)
114 #ifndef REVARP_REQUEST
115 #define REVARP_REQUEST 3
118 #define REVARP_REPLY 4
121 static u_char ezero[6];
124 arp_print(register const u_char *bp, u_int length, u_int caplen)
126 register const struct ether_arp *ap;
127 register const struct ether_header *eh;
128 register u_short pro, hrd, op;
130 ap = (struct ether_arp *)bp;
131 if ((u_char *)(ap + 1) > snapend) {
135 if (length < ETHER_ARP_HDRLEN) {
136 (void)printf("truncated-arp");
137 default_print((u_char *)ap, length);
141 pro = EXTRACT_16BITS(&ap->arp_pro);
142 hrd = EXTRACT_16BITS(&ap->arp_hrd);
143 op = EXTRACT_16BITS(&ap->arp_op);
145 if ((pro != ETHERTYPE_IP && pro != ETHERTYPE_TRAIL)
146 || ap->arp_hln != sizeof(SHA(ap))
147 || ap->arp_pln != sizeof(SPA(ap))) {
148 (void)printf("arp-#%d for proto #%d (%d) hardware #%d (%d)",
149 op, pro, ap->arp_pln,
153 if (pro == ETHERTYPE_TRAIL)
154 (void)printf("trailer-");
155 eh = (struct ether_header *)packetp;
159 (void)printf("arp who-has %s", ipaddr_string(TPA(ap)));
160 if (memcmp((char *)ezero, (char *)THA(ap), 6) != 0)
161 (void)printf(" (%s)", etheraddr_string(THA(ap)));
162 (void)printf(" tell %s", ipaddr_string(SPA(ap)));
163 if (memcmp((char *)ESRC(eh), (char *)SHA(ap), 6) != 0)
164 (void)printf(" (%s)", etheraddr_string(SHA(ap)));
168 (void)printf("arp reply %s", ipaddr_string(SPA(ap)));
169 if (memcmp((char *)ESRC(eh), (char *)SHA(ap), 6) != 0)
170 (void)printf(" (%s)", etheraddr_string(SHA(ap)));
171 (void)printf(" is-at %s", etheraddr_string(SHA(ap)));
172 if (memcmp((char *)EDST(eh), (char *)THA(ap), 6) != 0)
173 (void)printf(" (%s)", etheraddr_string(THA(ap)));
177 (void)printf("rarp who-is %s tell %s",
178 etheraddr_string(THA(ap)),
179 etheraddr_string(SHA(ap)));
183 (void)printf("rarp reply %s at %s",
184 etheraddr_string(THA(ap)),
185 ipaddr_string(TPA(ap)));
189 (void)printf("arp-#%d", op);
190 default_print((u_char *)ap, caplen);
193 if (hrd != ARPHRD_ETHER)
194 printf(" hardware #%d", hrd);