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 static const char tstr[] = " [|null]";
  37
  38 /*
  39  * The DLT_NULL packet header is 4 bytes long. It contains a host-byte-order
  40  * 32-bit integer that specifies the family, e.g. AF_INET.
  41  *
  42  * Note here that "host" refers to the host on which the packets were
  43  * captured; that isn't necessarily *this* host.
  44  *
  45  * The OpenBSD DLT_LOOP packet header is the same, except that the integer
  46  * is in network byte order.
  47  */
  48 #define NULL_HDRLEN 4
  49
  50 /*
  51  * Byte-swap a 32-bit number.
  52  * ("htonl()" or "ntohl()" won't work - we want to byte-swap even on
  53  * big-endian platforms.)
  54  */
  55 #define SWAPLONG(y) \
  56 ((((y)&0xff)<<24) | (((y)&0xff00)<<8) | (((y)&0xff0000)>>8) | (((y)>>24)&0xff))
  57
  58 static void
  59 null_hdr_print(netdissect_options *ndo, u_int family, u_int length)
  60 {
  61         if (!ndo->ndo_qflag) {
  62                 ND_PRINT("AF %s (%u)",
  63                         tok2str(bsd_af_values,"Unknown",family),family);
  64         } else {
  65                 ND_PRINT("%s",
  66                         tok2str(bsd_af_values,"Unknown AF %u",family));
  67         }
  68
  69         ND_PRINT(", length %u: ", length);
  70 }
  71
  72 /*
  73  * This is the top level routine of the printer.  'p' points
  74  * to the ether header of the packet, 'h->ts' is the timestamp,
  75  * 'h->len' is the length of the packet off the wire, and 'h->caplen'
  76  * is the number of bytes actually captured.
  77  */
  78 u_int
  79 null_if_print(netdissect_options *ndo, const struct pcap_pkthdr *h, const u_char *p)
  80 {
  81         u_int length = h->len;
  82         u_int caplen = h->caplen;
  83         uint32_t family;
  84
  85         ndo->ndo_protocol = "null_if";
  86         if (caplen < NULL_HDRLEN)
  87                 goto trunc;
  88
  89         ND_TCHECK_4(p);
  90         memcpy((char *)&family, (const char *)p, sizeof(family));
  91
  92         /*
  93          * This isn't necessarily in our host byte order; if this is
  94          * a DLT_LOOP capture, it's in network byte order, and if
  95          * this is a DLT_NULL capture from a machine with the opposite
  96          * byte-order, it's in the opposite byte order from ours.
  97          *
  98          * If the upper 16 bits aren't all zero, assume it's byte-swapped.
  99          */
 100         if ((family & 0xFFFF0000) != 0)
 101                 family = SWAPLONG(family);
 102
 103         if (ndo->ndo_eflag)
 104                 null_hdr_print(ndo, family, length);
 105
 106         length -= NULL_HDRLEN;
 107         caplen -= NULL_HDRLEN;
 108         p += NULL_HDRLEN;
 109
 110         switch (family) {
 111
 112         case BSD_AFNUM_INET:
 113                 ip_print(ndo, p, length);
 114                 break;
 115
 116         case BSD_AFNUM_INET6_BSD:
 117         case BSD_AFNUM_INET6_FREEBSD:
 118         case BSD_AFNUM_INET6_DARWIN:
 119                 ip6_print(ndo, p, length);
 120                 break;
 121
 122         case BSD_AFNUM_ISO:
 123                 isoclns_print(ndo, p, length);
 124                 break;
 125
 126         case BSD_AFNUM_APPLETALK:
 127                 atalk_print(ndo, p, length);
 128                 break;
 129
 130         case BSD_AFNUM_IPX:
 131                 ipx_print(ndo, p, length);
 132                 break;
 133
 134         default:
 135                 /* unknown AF_ value */
 136                 if (!ndo->ndo_eflag)
 137                         null_hdr_print(ndo, family, length + NULL_HDRLEN);
 138                 if (!ndo->ndo_suppress_default_print)
 139                         ND_DEFAULTPRINT(p, caplen);
 140         }
 141
 142         return (NULL_HDRLEN);
 143 trunc:
 144         ND_PRINT("%s", tstr);
 145         return (NULL_HDRLEN);
 146 }