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 <tcpdump-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 static const char istr[] = " (invalid)";
  46
  47 #define LOOPBACK_REPLY   1
  48 #define LOOPBACK_FWDDATA 2
  49
  50 static const struct tok fcode_str[] = {
  51         { LOOPBACK_REPLY,   "Reply"        },
  52         { LOOPBACK_FWDDATA, "Forward Data" },
  53         { 0, NULL }
  54 };
  55
  56 static void
  57 loopback_message_print(netdissect_options *ndo, const u_char *cp, const u_int len)
  58 {
  59         const u_char *ep = cp + len;
  60         uint16_t function;
  61
  62         if (len < 2)
  63                 goto invalid;
  64         /* function */
  65         ND_TCHECK2(*cp, 2);
  66         function = EXTRACT_LE_16BITS(cp);
  67         cp += 2;
  68         ND_PRINT((ndo, ", %s", tok2str(fcode_str, " invalid (%u)", function)));
  69
  70         switch (function) {
  71                 case LOOPBACK_REPLY:
  72                         if (len < 4)
  73                                 goto invalid;
  74                         /* receipt number */
  75                         ND_TCHECK2(*cp, 2);
  76                         ND_PRINT((ndo, ", receipt number %u", EXTRACT_LE_16BITS(cp)));
  77                         cp += 2;
  78                         /* data */
  79                         ND_PRINT((ndo, ", data (%u octets)", len - 4));
  80                         ND_TCHECK2(*cp, len - 4);
  81                         break;
  82                 case LOOPBACK_FWDDATA:
  83                         if (len < 8)
  84                                 goto invalid;
  85                         /* forwarding address */
  86                         ND_TCHECK2(*cp, ETHER_ADDR_LEN);
  87                         ND_PRINT((ndo, ", forwarding address %s", etheraddr_string(ndo, cp)));
  88                         cp += ETHER_ADDR_LEN;
  89                         /* data */
  90                         ND_PRINT((ndo, ", data (%u octets)", len - 8));
  91                         ND_TCHECK2(*cp, len - 8);
  92                         break;
  93                 default:
  94                         ND_TCHECK2(*cp, len - 2);
  95                         break;
  96         }
  97         return;
  98
  99 invalid:
 100         ND_PRINT((ndo, "%s", istr));
 101         ND_TCHECK2(*cp, ep - cp);
 102         return;
 103 trunc:
 104         ND_PRINT((ndo, "%s", tstr));
 105 }
 106
 107 void
 108 loopback_print(netdissect_options *ndo, const u_char *cp, const u_int len)
 109 {
 110         const u_char *ep = cp + len;
 111         uint16_t skipCount;
 112
 113         ND_PRINT((ndo, "Loopback"));
 114         if (len < 2)
 115                 goto invalid;
 116         /* skipCount */
 117         ND_TCHECK2(*cp, 2);
 118         skipCount = EXTRACT_LE_16BITS(cp);
 119         cp += 2;
 120         ND_PRINT((ndo, ", skipCount %u", skipCount));
 121         if (skipCount % 8)
 122                 ND_PRINT((ndo, " (bogus)"));
 123         if (skipCount > len - 2)
 124                 goto invalid;
 125         loopback_message_print(ndo, cp + skipCount, len - 2 - skipCount);
 126         return;
 127
 128 invalid:
 129         ND_PRINT((ndo, "%s", istr));
 130         ND_TCHECK2(*cp, ep - cp);
 131         return;
 132 trunc:
 133         ND_PRINT((ndo, "%s", tstr));
 134 }
 135