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

   1 /*
   2  * This module implements decoding of the the Loopback Protocol, originally
   3  * defined as the Configuration Testing Protocol. It is based on the following
   4  * specification:
   5  * http://www.mit.edu/people/jhawk/ctp.pdf
   6  *
   7  * Copyright (c) 2014 The TCPDUMP project
   8  * All rights reserved.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  20  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  21  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  22  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
  23  * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  24  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
  25  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  26  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  27  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  29  * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  30  * POSSIBILITY OF SUCH DAMAGE.
  31  */
  32
  33 #define NETDISSECT_REWORKED
  34 #ifdef HAVE_CONFIG_H
  35 #include "config.h"
  36 #endif
  37
  38 #include <tcpdump-stdinc.h>
  39
  40 #include "interface.h"
  41 #include "extract.h"
  42 #include "ether.h"
  43 #include "addrtoname.h"
  44
  45 static const char tstr[] = " [|loopback]";
  46 static const char cstr[] = " (corrupt)";
  47
  48 #define LOOPBACK_REPLY   1
  49 #define LOOPBACK_FWDDATA 2
  50
  51 static const struct tok fcode_str[] = {
  52         { LOOPBACK_REPLY,   "Reply"        },
  53         { LOOPBACK_FWDDATA, "Forward Data" },
  54         { 0, NULL }
  55 };
  56
  57 static void
  58 loopback_message_print(netdissect_options *ndo, const u_char *cp, const u_int len)
  59 {
  60         const u_char *ep = cp + len;
  61         uint16_t function;
  62
  63         if (len < 2)
  64                 goto corrupt;
  65         /* function */
  66         ND_TCHECK2(*cp, 2);
  67         function = EXTRACT_LE_16BITS(cp);
  68         cp += 2;
  69         ND_PRINT((ndo, ", %s", tok2str(fcode_str, " invalid (%u)", function)));
  70
  71         switch (function) {
  72                 case LOOPBACK_REPLY:
  73                         if (len < 4)
  74                                 goto corrupt;
  75                         /* receipt number */
  76                         ND_TCHECK2(*cp, 2);
  77                         ND_PRINT((ndo, ", receipt number %u", EXTRACT_LE_16BITS(cp)));
  78                         cp += 2;
  79                         /* data */
  80                         ND_PRINT((ndo, ", data (%u octets)", len - 4));
  81                         ND_TCHECK2(*cp, len - 4);
  82                         break;
  83                 case LOOPBACK_FWDDATA:
  84                         if (len < 8)
  85                                 goto corrupt;
  86                         /* forwarding address */
  87                         ND_TCHECK2(*cp, ETHER_ADDR_LEN);
  88                         ND_PRINT((ndo, ", forwarding address %s", etheraddr_string(cp)));
  89                         cp += ETHER_ADDR_LEN;
  90                         /* data */
  91                         ND_PRINT((ndo, ", data (%u octets)", len - 8));
  92                         ND_TCHECK2(*cp, len - 8);
  93                         break;
  94                 default:
  95                         ND_TCHECK2(*cp, len - 2);
  96                         break;
  97         }
  98         return;
  99
 100 corrupt:
 101         ND_PRINT((ndo, "%s", cstr));
 102         ND_TCHECK2(*cp, ep - cp);
 103         return;
 104 trunc:
 105         ND_PRINT((ndo, "%s", tstr));
 106 }
 107
 108 void
 109 loopback_print(netdissect_options *ndo, const u_char *cp, const u_int len)
 110 {
 111         const u_char *ep = cp + len;
 112         uint16_t skipCount;
 113
 114         ND_PRINT((ndo, "Loopback"));
 115         if (len < 2)
 116                 goto corrupt;
 117         /* skipCount */
 118         ND_TCHECK2(*cp, 2);
 119         skipCount = EXTRACT_LE_16BITS(cp);
 120         cp += 2;
 121         ND_PRINT((ndo, ", skipCount %u", skipCount));
 122         if (skipCount % 8)
 123                 ND_PRINT((ndo, " (bogus)"));
 124         if (skipCount > len - 2)
 125                 goto corrupt;
 126         loopback_message_print(ndo, cp + skipCount, len - 2 - skipCount);
 127         return;
 128
 129 corrupt:
 130         ND_PRINT((ndo, "%s", cstr));
 131         ND_TCHECK2(*cp, ep - cp);
 132         return;
 133 trunc:
 134         ND_PRINT((ndo, "%s", tstr));
 135 }
 136