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.
23 static const char rcsid[] =
24 "@(#) $Header: /tcpdump/master/tcpdump/print-arp.c,v 1.51 2001/09/17 21:57:54 fenner Exp $ (LBL)";
31 #include <sys/param.h>
34 #include <netinet/in.h>
39 #include "interface.h"
40 #include "addrtoname.h"
42 #include "ethertype.h"
43 #include "extract.h" /* must come after interface.h */
46 * Address Resolution Protocol.
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.
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 */
74 * The remaining fields are variable in size,
75 * according to the sizes above.
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 */
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)
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))
101 static u_char ezero[6];
104 arp_print(const u_char *bp, u_int length, u_int caplen)
106 const struct arphdr *ap;
107 u_short pro, hrd, op;
109 ap = (const struct arphdr *)bp;
111 if ((const u_char *)(ar_tpa(ap) + PLN(ap)) > snapend) {
112 (void)printf("truncated-arp");
113 default_print((const u_char *)ap, length);
117 pro = EXTRACT_16BITS(&PRO(ap));
118 hrd = EXTRACT_16BITS(&HRD(ap));
119 op = EXTRACT_16BITS(&OP(ap));
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));
126 if (pro == ETHERTYPE_TRAIL)
127 (void)printf("trailer-");
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)));
139 (void)printf("arp reply %s", ipaddr_string(SPA(ap)));
140 (void)printf(" is-at %s", linkaddr_string(SHA(ap), HLN(ap)));
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)));
150 (void)printf("rarp reply %s at %s",
151 linkaddr_string(THA(ap), HLN(ap)),
152 ipaddr_string(TPA(ap)));
156 (void)printf("arp-#%d", op);
157 default_print((const u_char *)ap, caplen);
160 if (hrd != ARPHRD_ETHER)
161 printf(" hardware #%d", hrd);
164 (void)printf("[|arp]");