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

   1 /*
   2  * This module implements decoding of 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 #ifdef HAVE_CONFIG_H
  34 #include "config.h"
  35 #endif
  36
  37 #include <netdissect-stdinc.h>
  38
  39 #include "netdissect.h"
  40 #include "extract.h"
  41 #include "ether.h"
  42 #include "addrtoname.h"
  43
  44 static const char tstr[] = " [|loopback]";
  45
  46 #define LOOPBACK_REPLY   1
  47 #define LOOPBACK_FWDDATA 2
  48
  49 static const struct tok fcode_str[] = {
  50         { LOOPBACK_REPLY,   "Reply"        },
  51         { LOOPBACK_FWDDATA, "Forward Data" },
  52         { 0, NULL }
  53 };
  54
  55 static void
  56 loopback_message_print(netdissect_options *ndo, const u_char *cp, const u_int len)
  57 {
  58         const u_char *ep = cp + len;
  59         uint16_t function;
  60
  61         if (len < 2)
  62                 goto invalid;
  63         /* function */
  64         ND_TCHECK2(*cp, 2);
  65         function = EXTRACT_LE_16BITS(cp);
  66         cp += 2;
  67         ND_PRINT((ndo, ", %s", tok2str(fcode_str, " invalid (%u)", function)));
  68
  69         switch (function) {
  70                 case LOOPBACK_REPLY:
  71                         if (len < 4)
  72                                 goto invalid;
  73                         /* receipt number */
  74                         ND_TCHECK2(*cp, 2);
  75                         ND_PRINT((ndo, ", receipt number %u", EXTRACT_LE_16BITS(cp)));
  76                         cp += 2;
  77                         /* data */
  78                         ND_PRINT((ndo, ", data (%u octets)", len - 4));
  79                         ND_TCHECK2(*cp, len - 4);
  80                         break;
  81                 case LOOPBACK_FWDDATA:
  82                         if (len < 8)
  83                                 goto invalid;
  84                         /* forwarding address */
  85                         ND_TCHECK2(*cp, ETHER_ADDR_LEN);
  86                         ND_PRINT((ndo, ", forwarding address %s", etheraddr_string(ndo, cp)));
  87                         cp += ETHER_ADDR_LEN;
  88                         /* data */
  89                         ND_PRINT((ndo, ", data (%u octets)", len - 8));
  90                         ND_TCHECK2(*cp, len - 8);
  91                         break;
  92                 default:
  93                         ND_TCHECK2(*cp, len - 2);
  94                         break;
  95         }
  96         return;
  97
  98 invalid:
  99         ND_PRINT((ndo, "%s", istr));
 100         ND_TCHECK2(*cp, ep - cp);
 101         return;
 102 trunc:
 103         ND_PRINT((ndo, "%s", tstr));
 104 }
 105
 106 void
 107 loopback_print(netdissect_options *ndo, const u_char *cp, const u_int len)
 108 {
 109         const u_char *ep = cp + len;
 110         uint16_t skipCount;
 111
 112         ND_PRINT((ndo, "Loopback"));
 113         if (len < 2)
 114                 goto invalid;
 115         /* skipCount */
 116         ND_TCHECK2(*cp, 2);
 117         skipCount = EXTRACT_LE_16BITS(cp);
 118         cp += 2;
 119         ND_PRINT((ndo, ", skipCount %u", skipCount));
 120         if (skipCount % 8)
 121                 ND_PRINT((ndo, " (bogus)"));
 122         if (skipCount > len - 2)
 123                 goto invalid;
 124         loopback_message_print(ndo, cp + skipCount, len - 2 - skipCount);
 125         return;
 126
 127 invalid:
 128         ND_PRINT((ndo, "%s", istr));
 129         ND_TCHECK2(*cp, ep - cp);
 130         return;
 131 trunc:
 132         ND_PRINT((ndo, "%s", tstr));
 133 }
 134