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

   1 /*
   2  * Copyright (c) 2014 The TCPDUMP project
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  *
  14  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  15  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  16  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  17  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
  18  * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  19  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
  20  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  21  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  22  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  23  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  24  * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  25  * POSSIBILITY OF SUCH DAMAGE.
  26  */
  27
  28 /* \summary: Loopback Protocol printer */
  29
  30 /*
  31  * originally defined as the Ethernet Configuration Testing Protocol.
  32  * specification:
  33  * https://web.archive.org/web/20060919181108/http://www.mit.edu/people/jhawk/ctp.pdf
  34  */
  35
  36 #ifdef HAVE_CONFIG_H
  37 #include <config.h>
  38 #endif
  39
  40 #include "netdissect-stdinc.h"
  41
  42 #define ND_LONGJMP_FROM_TCHECK
  43 #include "netdissect.h"
  44 #include "extract.h"
  45 #include "addrtoname.h"
  46
  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,
  59                        const u_char *cp, u_int len)
  60 {
  61         uint16_t function;
  62
  63         if (len < 2)
  64                 goto invalid;
  65         /* function */
  66         function = GET_LE_U_2(cp);
  67         cp += 2;
  68         len -= 2;
  69         ND_PRINT(", %s", tok2str(fcode_str, " invalid (%u)", function));
  70
  71         switch (function) {
  72                 case LOOPBACK_REPLY:
  73                         if (len < 2)
  74                                 goto invalid;
  75                         /* receipt number */
  76                         ND_PRINT(", receipt number %u", GET_LE_U_2(cp));
  77                         cp += 2;
  78                         len -= 2;
  79                         /* data */
  80                         ND_PRINT(", data (%u octets)", len);
  81                         ND_TCHECK_LEN(cp, len);
  82                         break;
  83                 case LOOPBACK_FWDDATA:
  84                         if (len < MAC48_LEN)
  85                                 goto invalid;
  86                         /* forwarding address */
  87                         ND_PRINT(", forwarding address %s", GET_MAC48_STRING(cp));
  88                         cp += MAC48_LEN;
  89                         len -= MAC48_LEN;
  90                         /* data */
  91                         ND_PRINT(", data (%u octets)", len);
  92                         ND_TCHECK_LEN(cp, len);
  93                         break;
  94                 default:
  95                         ND_TCHECK_LEN(cp, len);
  96                         break;
  97         }
  98         return;
  99
 100 invalid:
 101         nd_print_invalid(ndo);
 102         ND_TCHECK_LEN(cp, len);
 103 }
 104
 105 void
 106 loopback_print(netdissect_options *ndo,
 107                const u_char *cp, u_int len)
 108 {
 109         uint16_t skipCount;
 110
 111         ndo->ndo_protocol = "loopback";
 112         ND_PRINT("Loopback");
 113         if (len < 2)
 114                 goto invalid;
 115         /* skipCount */
 116         skipCount = GET_LE_U_2(cp);
 117         cp += 2;
 118         len -= 2;
 119         ND_PRINT(", skipCount %u", skipCount);
 120         if (skipCount % 8)
 121                 ND_PRINT(" (bogus)");
 122         if (skipCount > len)
 123                 goto invalid;
 124         /* the octets to skip */
 125         ND_TCHECK_LEN(cp, skipCount);
 126         cp += skipCount;
 127         len -= skipCount;
 128         /* the first message to decode */
 129         loopback_message_print(ndo, cp, len);
 130         return;
 131
 132 invalid:
 133         nd_print_invalid(ndo);
 134         ND_TCHECK_LEN(cp, len);
 135 }
 136