epan/dissectors/packet-loop.c

   1 /* packet-loop.c
   2  * Routines for Ethernet loopback/Configuration Test Protocol dissection
   3  *
   4  * See
   5  *
   6  *      http://stuff.mit.edu/people/jhawk/ctp.html
   7  *
   8  * $Id$
   9  *
  10  * Wireshark - Network traffic analyzer
  11  * By Gerald Combs <gerald@wireshark.org>
  12  * Copyright 1998 Gerald Combs
  13  *
  14  * This program is free software; you can redistribute it and/or
  15  * modify it under the terms of the GNU General Public License
  16  * as published by the Free Software Foundation; either version 2
  17  * of the License, or (at your option) any later version.
  18  *
  19  * This program is distributed in the hope that it will be useful,
  20  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22  * GNU General Public License for more details.
  23  *
  24  * You should have received a copy of the GNU General Public License
  25  * along with this program; if not, write to the Free Software
  26  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  27  */
  28
  29 #include "config.h"
  30
  31 #include <glib.h>
  32 #include <epan/packet.h>
  33 #include <epan/etypes.h>
  34
  35 static int proto_loop = -1;
  36 static int hf_loop_skipcount = -1;
  37 static int hf_loop_function = -1;
  38 static int hf_loop_receipt_number = -1;
  39 static int hf_loop_forwarding_address = -1;
  40
  41 static gint ett_loop = -1;
  42
  43 static dissector_handle_t data_handle;
  44
  45 #define FUNC_REPLY              1
  46 #define FUNC_FORWARD_DATA       2
  47
  48 static const value_string function_vals[] = {
  49   { FUNC_REPLY, "Reply" },
  50   { FUNC_FORWARD_DATA, "Forward Data" },
  51   { 0, NULL }
  52 };
  53
  54 static void
  55 dissect_loop(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
  56 {
  57   proto_tree  *loop_tree = NULL;
  58   proto_item  *ti;
  59   guint16     function;
  60   int         offset = 0;
  61   int         skip_offset;
  62   gboolean    set_info = TRUE;
  63   gboolean    more_function;
  64   tvbuff_t    *next_tvb;
  65
  66   col_set_str(pinfo->cinfo, COL_PROTOCOL, "LOOP");
  67   col_clear(pinfo->cinfo, COL_INFO);
  68
  69   if (tree) {
  70     ti = proto_tree_add_item(tree, proto_loop, tvb, offset, -1, ENC_NA);
  71     loop_tree = proto_item_add_subtree(ti, ett_loop);
  72
  73     proto_tree_add_item(loop_tree, hf_loop_skipcount, tvb, offset, 2, ENC_LITTLE_ENDIAN);
  74   }
  75   skip_offset = 2 + tvb_get_letohs(tvb, offset);
  76   offset += 2;
  77
  78   do {
  79     function = tvb_get_letohs(tvb, offset);
  80     if (offset == skip_offset) {
  81       col_add_str(pinfo->cinfo, COL_INFO,
  82                     val_to_str(function, function_vals, "Unknown function (%u)"));
  83
  84       proto_tree_add_text(loop_tree, tvb, offset, 2, "Relevant function:");
  85       set_info = FALSE;
  86     }
  87     if (tree)
  88       proto_tree_add_uint(loop_tree, hf_loop_function, tvb, offset, 2, function);
  89     offset += 2;
  90     switch (function) {
  91
  92     case FUNC_REPLY:
  93       if (tree)
  94         proto_tree_add_item(loop_tree, hf_loop_receipt_number, tvb, offset, 2,
  95                             ENC_LITTLE_ENDIAN);
  96       offset += 2;
  97       more_function = FALSE;
  98       break;
  99
 100     case FUNC_FORWARD_DATA:
 101       if (tree)
 102         proto_tree_add_item(loop_tree, hf_loop_forwarding_address, tvb, offset,
 103                             6, ENC_NA);
 104       offset += 6;
 105       more_function = TRUE;
 106       break;
 107
 108     default:
 109       more_function = FALSE;
 110       break;
 111     }
 112   } while (more_function);
 113
 114   if (set_info) {
 115     col_set_str(pinfo->cinfo, COL_INFO, "No valid function found");
 116   }
 117
 118   if (tvb_length_remaining(tvb, offset) > 0)
 119   {
 120     next_tvb = tvb_new_subset_remaining(tvb, offset);
 121     call_dissector(data_handle, next_tvb, pinfo, tree);
 122   }
 123 }
 124
 125 void
 126 proto_register_loop(void)
 127 {
 128   static hf_register_info hf[] = {
 129     { &hf_loop_skipcount,
 130       { "skipCount",            "loop.skipcount",
 131         FT_UINT16,      BASE_DEC,       NULL,   0x0,
 132         NULL, HFILL }},
 133
 134     { &hf_loop_function,
 135       { "Function",             "loop.function",
 136         FT_UINT16,      BASE_DEC,       VALS(function_vals),    0x0,
 137         NULL, HFILL }},
 138
 139     { &hf_loop_receipt_number,
 140       { "Receipt number",       "loop.receipt_number",
 141         FT_UINT16,      BASE_DEC,       NULL,   0x0,
 142         NULL, HFILL }},
 143
 144     { &hf_loop_forwarding_address,
 145       { "Forwarding address",   "loop.forwarding_address",
 146         FT_ETHER,       BASE_NONE,      NULL,   0x0,
 147         NULL, HFILL }},
 148   };
 149   static gint *ett[] = {
 150     &ett_loop,
 151   };
 152
 153   proto_loop = proto_register_protocol("Configuration Test Protocol (loopback)",
 154                                       "LOOP", "loop");
 155   proto_register_field_array(proto_loop, hf, array_length(hf));
 156   proto_register_subtree_array(ett, array_length(ett));
 157 }
 158
 159 void
 160 proto_reg_handoff_loop(void)
 161 {
 162   dissector_handle_t loop_handle;
 163
 164   loop_handle = create_dissector_handle(dissect_loop, proto_loop);
 165
 166   dissector_add_uint("ethertype", ETHERTYPE_LOOP, loop_handle);
 167
 168   data_handle = find_dissector("data");
 169 }