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 1.49 2000/10/10 05:05:07 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 */ 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_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 */ 72 /* 73 * The remaining fields are variable in size, 74 * according to the sizes above. 75 */ 76 #ifdef COMMENT_ONLY 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 */ 81 #endif 82 }; 83 84 #define ARP_HDRLEN 8 85 86 /* 87 * Ethernet Address Resolution Protocol. 88 * 89 * See RFC 826 for protocol description. Structure below is adapted 90 * to resolving internet addresses. Field names used correspond to 91 * RFC 826. 92 */ 93 struct ether_arp { 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 */ 99 }; 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 105 106 #define ETHER_ARP_HDRLEN (ARP_HDRLEN + 6 + 4 + 6 + 4) 107 108 #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) 112 113 /* Compatibility */ 114 #ifndef REVARP_REQUEST 115 #define REVARP_REQUEST 3 116 #endif 117 #ifndef REVARP_REPLY 118 #define REVARP_REPLY 4 119 #endif 120 121 static u_char ezero[6]; 122 123 void 124 arp_print(register const u_char *bp, u_int length, u_int caplen) 125 { 126 register const struct ether_arp *ap; 127 register const struct ether_header *eh; 128 register u_short pro, hrd, op; 129 130 ap = (struct ether_arp *)bp; 131 if ((u_char *)(ap + 1) > snapend) { 132 printf("[|arp]"); 133 return; 134 } 135 if (length < ETHER_ARP_HDRLEN) { 136 (void)printf("truncated-arp"); 137 default_print((u_char *)ap, length); 138 return; 139 } 140 141 pro = EXTRACT_16BITS(&ap->arp_pro); 142 hrd = EXTRACT_16BITS(&ap->arp_hrd); 143 op = EXTRACT_16BITS(&ap->arp_op); 144 145 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, 150 hrd, ap->arp_hln); 151 return; 152 } 153 if (pro == ETHERTYPE_TRAIL) 154 (void)printf("trailer-"); 155 eh = (struct ether_header *)packetp; 156 switch (op) { 157 158 case ARPOP_REQUEST: 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))); 165 break; 166 167 case ARPOP_REPLY: 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))); 174 break; 175 176 case REVARP_REQUEST: 177 (void)printf("rarp who-is %s tell %s", 178 etheraddr_string(THA(ap)), 179 etheraddr_string(SHA(ap))); 180 break; 181 182 case REVARP_REPLY: 183 (void)printf("rarp reply %s at %s", 184 etheraddr_string(THA(ap)), 185 ipaddr_string(TPA(ap))); 186 break; 187 188 default: 189 (void)printf("arp-#%d", op); 190 default_print((u_char *)ap, caplen); 191 return; 192 } 193 if (hrd != ARPHRD_ETHER) 194 printf(" hardware #%d", hrd); 195 } 196