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/* packet-loop.c
* Routines for Ethernet loopback/Configuration Test Protocol dissection,
* as documented in section 8 "Ethernet Configuration Testing Protocol" of
* the v2.0 DIX Ethernet specification.
*
* See
*
* http://decnet.ipv7.net/docs/dundas/aa-k759b-tk.pdf
*
* for a copy of the DIX spec and
*
* http://stuff.mit.edu/people/jhawk/ctp.html
*
* for section 8.
*
* Wireshark - Network traffic analyzer
* By Gerald Combs <gerald@wireshark.org>
* Copyright 1998 Gerald Combs
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
#include "config.h"
#include <epan/packet.h>
#include <epan/etypes.h>
void proto_register_loop(void);
void proto_reg_handoff_loop(void);
static dissector_handle_t loop_handle;
static int proto_loop;
static int hf_loop_skipcount;
static int hf_loop_function;
static int hf_loop_relevant_function;
static int hf_loop_receipt_number;
static int hf_loop_forwarding_address;
static int ett_loop;
#define FUNC_REPLY 1
#define FUNC_FORWARD_DATA 2
static const value_string function_vals[] = {
{ FUNC_REPLY, "Reply" },
{ FUNC_FORWARD_DATA, "Forward Data" },
{ 0, NULL }
};
static int
dissect_loop(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_)
{
proto_tree *loop_tree = NULL;
proto_item *ti;
uint16_t function;
int offset = 0;
int skip_offset;
bool set_info = true;
bool more_function;
tvbuff_t *next_tvb;
col_set_str(pinfo->cinfo, COL_PROTOCOL, "LOOP");
col_clear(pinfo->cinfo, COL_INFO);
if (tree) {
ti = proto_tree_add_item(tree, proto_loop, tvb, offset, -1, ENC_NA);
loop_tree = proto_item_add_subtree(ti, ett_loop);
proto_tree_add_item(loop_tree, hf_loop_skipcount, tvb, offset, 2, ENC_LITTLE_ENDIAN);
}
skip_offset = 2 + tvb_get_letohs(tvb, offset);
offset += 2;
do {
function = tvb_get_letohs(tvb, offset);
if (offset == skip_offset) {
col_add_str(pinfo->cinfo, COL_INFO,
val_to_str(function, function_vals, "Unknown function (%u)"));
proto_tree_add_uint(loop_tree, hf_loop_relevant_function, tvb, offset, 2, function);
set_info = false;
}
proto_tree_add_uint(loop_tree, hf_loop_function, tvb, offset, 2, function);
offset += 2;
switch (function) {
case FUNC_REPLY:
proto_tree_add_item(loop_tree, hf_loop_receipt_number, tvb, offset, 2,
ENC_LITTLE_ENDIAN);
offset += 2;
more_function = false;
break;
case FUNC_FORWARD_DATA:
proto_tree_add_item(loop_tree, hf_loop_forwarding_address, tvb, offset,
6, ENC_NA);
offset += 6;
more_function = true;
break;
default:
more_function = false;
break;
}
} while (more_function);
if (set_info) {
col_set_str(pinfo->cinfo, COL_INFO, "No valid function found");
}
if (tvb_reported_length_remaining(tvb, offset) > 0)
{
next_tvb = tvb_new_subset_remaining(tvb, offset);
call_data_dissector(next_tvb, pinfo, tree);
}
return tvb_captured_length(tvb);
}
void
proto_register_loop(void)
{
static hf_register_info hf[] = {
{ &hf_loop_skipcount,
{ "skipCount", "loop.skipcount",
FT_UINT16, BASE_DEC, NULL, 0x0,
NULL, HFILL }},
{ &hf_loop_function,
{ "Function", "loop.function",
FT_UINT16, BASE_DEC, VALS(function_vals), 0x0,
NULL, HFILL }},
{ &hf_loop_relevant_function,
{ "Relevant function", "loop.relevant_function",
FT_UINT16, BASE_DEC, VALS(function_vals), 0x0,
NULL, HFILL }},
{ &hf_loop_receipt_number,
{ "Receipt number", "loop.receipt_number",
FT_UINT16, BASE_DEC, NULL, 0x0,
NULL, HFILL }},
{ &hf_loop_forwarding_address,
{ "Forwarding address", "loop.forwarding_address",
FT_ETHER, BASE_NONE, NULL, 0x0,
NULL, HFILL }},
};
static int *ett[] = {
&ett_loop,
};
proto_loop = proto_register_protocol("Configuration Test Protocol (loopback)",
"LOOP", "loop");
proto_register_field_array(proto_loop, hf, array_length(hf));
proto_register_subtree_array(ett, array_length(ett));
loop_handle = register_dissector("loop", dissect_loop, proto_loop);
}
void
proto_reg_handoff_loop(void)
{
dissector_add_uint("ethertype", ETHERTYPE_LOOP, loop_handle);
}
/*
* Editor modelines - https://www.wireshark.org/tools/modelines.html
*
* Local Variables:
* c-basic-offset: 2
* tab-width: 8
* indent-tabs-mode: nil
* End:
*
* ex: set shiftwidth=2 tabstop=8 expandtab:
* :indentSize=2:tabSize=8:noTabs=true:
*/
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