The Tcpdump Group git mirrors - tcpdump/blob - print-null.c

   1 /*
   2  * Copyright (c) 1991, 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
  22 /* \summary: BSD loopback device printer */
  23
  24 #ifdef HAVE_CONFIG_H
  25 #include <config.h>
  26 #endif
  27
  28 #include "netdissect-stdinc.h"
  29
  30 #include <string.h>
  31
  32 #include "netdissect.h"
  33 #include "extract.h"
  34 #include "af.h"
  35
  36
  37 /*
  38  * The DLT_NULL packet header is 4 bytes long. It contains a host-byte-order
  39  * 32-bit integer that specifies the family, e.g. AF_INET.
  40  *
  41  * Note here that "host" refers to the host on which the packets were
  42  * captured; that isn't necessarily *this* host.
  43  *
  44  * The OpenBSD DLT_LOOP packet header is the same, except that the integer
  45  * is in network byte order.
  46  */
  47 #define NULL_HDRLEN 4
  48
  49 /*
  50  * Byte-swap a 32-bit number.
  51  * ("htonl()" or "ntohl()" won't work - we want to byte-swap even on
  52  * big-endian platforms.)
  53  */
  54 #define SWAPLONG(y) \
  55 ((((y)&0xff)<<24) | (((y)&0xff00)<<8) | (((y)&0xff0000)>>8) | (((y)>>24)&0xff))
  56
  57 static void
  58 null_hdr_print(netdissect_options *ndo, uint32_t family, u_int length)
  59 {
  60         if (!ndo->ndo_qflag) {
  61                 ND_PRINT("AF %s (%u)",
  62                         tok2str(bsd_af_values,"Unknown",family),family);
  63         } else {
  64                 ND_PRINT("%s",
  65                         tok2str(bsd_af_values,"Unknown AF %u",family));
  66         }
  67
  68         ND_PRINT(", length %u: ", length);
  69 }
  70
  71 /*
  72  * This is the top level routine of the printer.  'p' points
  73  * to the ether header of the packet, 'h->ts' is the timestamp,
  74  * 'h->len' is the length of the packet off the wire, and 'h->caplen'
  75  * is the number of bytes actually captured.
  76  */
  77 void
  78 null_if_print(netdissect_options *ndo, const struct pcap_pkthdr *h, const u_char *p)
  79 {
  80         u_int length = h->len;
  81         u_int caplen = h->caplen;
  82         uint32_t family;
  83
  84         ndo->ndo_protocol = "null";
  85         if (caplen < NULL_HDRLEN) {
  86                 ndo->ndo_ll_hdr_len += caplen;
  87                 nd_print_trunc(ndo);
  88                 return;
  89         }
  90         ndo->ndo_ll_hdr_len += NULL_HDRLEN;
  91
  92         family = GET_HE_U_4(p);
  93
  94         /*
  95          * This isn't necessarily in our host byte order; if this is
  96          * a DLT_LOOP capture, it's in network byte order, and if
  97          * this is a DLT_NULL capture from a machine with the opposite
  98          * byte-order, it's in the opposite byte order from ours.
  99          *
 100          * If the upper 16 bits aren't all zero, assume it's byte-swapped.
 101          */
 102         if ((family & 0xFFFF0000) != 0)
 103                 family = SWAPLONG(family);
 104
 105         if (ndo->ndo_eflag)
 106                 null_hdr_print(ndo, family, length);
 107
 108         length -= NULL_HDRLEN;
 109         caplen -= NULL_HDRLEN;
 110         p += NULL_HDRLEN;
 111
 112         switch (family) {
 113
 114         case BSD_AFNUM_INET:
 115                 ip_print(ndo, p, length);
 116                 break;
 117
 118         case BSD_AFNUM_INET6_BSD:
 119         case BSD_AFNUM_INET6_FREEBSD:
 120         case BSD_AFNUM_INET6_DARWIN:
 121                 ip6_print(ndo, p, length);
 122                 break;
 123
 124         case BSD_AFNUM_ISO:
 125                 isoclns_print(ndo, p, length);
 126                 break;
 127
 128         case BSD_AFNUM_APPLETALK:
 129                 atalk_print(ndo, p, length);
 130                 break;
 131
 132         case BSD_AFNUM_IPX:
 133                 ipx_print(ndo, p, length);
 134                 break;
 135
 136         default:
 137                 /* unknown AF_ value */
 138                 if (!ndo->ndo_eflag)
 139                         null_hdr_print(ndo, family, length + NULL_HDRLEN);
 140                 if (!ndo->ndo_suppress_default_print)
 141                         ND_DEFAULTPRINT(p, caplen);
 142         }
 143 }