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 * $FreeBSD$ 22 */ 23 24 #ifndef lint 25 static 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 */ 57 struct 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)) 102 103 static u_char ezero[6]; 104 105 void 106 arp_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; 165 trunc: 166 (void)printf("[|arp]"); 167 } 168