wireshark/epan/dissectors/packet-tdmoe.c

/* packet-tdmoe.c
 * Routines for TDM over Ethernet packet disassembly
 * Copyright 2010, Haakon Nessjoen <haakon.nessjoen@gmail.com>
 *
 * 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>
#include <epan/prefs.h>

/* Bitmasks for the flags in the fourth byte of the packet */
#define TDMOE_YELLOW_ALARM_BITMASK 0x01
#define TDMOE_SIGBITS_BITMASK      0x02

void proto_reg_handoff_tdmoe(void);
void proto_register_tdmoe(void);

/* protocols and header fields */
static int proto_tdmoe = -1;

static int hf_tdmoe_subaddress = -1;
static int hf_tdmoe_samples = -1;
static int hf_tdmoe_flags = -1;
static int hf_tdmoe_yellow_alarm = -1;
static int hf_tdmoe_sig_bits_present = -1;
static int hf_tdmoe_packet_counter = -1;
static int hf_tdmoe_channels = -1;
static int hf_tdmoe_sig_bits = -1;

static gint ett_tdmoe = -1;
static gint ett_tdmoe_flags = -1;

static dissector_handle_t lapd_handle;

static gint pref_tdmoe_d_channel = 24;

static int
dissect_tdmoe(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)
{
	proto_item *ti;
	proto_tree *tdmoe_tree;
	tvbuff_t   *next_client;
	guint16     channels;
	guint16     subaddress;
	gint32 offset = 0;
	static int * const flags[] = { &hf_tdmoe_yellow_alarm, &hf_tdmoe_sig_bits_present, NULL };
	int         chan;

	/* Check that there's enough data */
	if (tvb_captured_length(tvb) < 8)
		return 0;

	subaddress = tvb_get_ntohs(tvb, 0);
	channels   = tvb_get_ntohs(tvb, 6);

	col_set_str(pinfo->cinfo, COL_PROTOCOL, "TDMoE");
	col_add_fstr(pinfo->cinfo, COL_INFO, "Subaddress: %d Channels: %d %s",
		subaddress,
		channels,
		(tvb_get_guint8(tvb, 3) & TDMOE_YELLOW_ALARM_BITMASK ? "[YELLOW ALARM]" : "")
	);


	/* create display subtree for the protocol */
	ti = proto_tree_add_item(tree, proto_tdmoe, tvb, 0, -1, ENC_NA);
	tdmoe_tree = proto_item_add_subtree(ti, ett_tdmoe);

	/* Subaddress */
	proto_tree_add_item(tdmoe_tree, hf_tdmoe_subaddress, tvb, offset, 2, ENC_BIG_ENDIAN);
	offset+=2;

	/* Samples (1 byte) */
	proto_tree_add_item(tdmoe_tree, hf_tdmoe_samples, tvb, offset, 1, ENC_BIG_ENDIAN);
	offset++;

	/* Yellow alarm & "Sig bits present" bits (1 byte) */
	proto_tree_add_bitmask(tdmoe_tree, tvb, offset, hf_tdmoe_flags, ett_tdmoe_flags, flags, ENC_BIG_ENDIAN);
	offset++;

	/* Packet counter (2 bytes) */
	proto_tree_add_item(tdmoe_tree, hf_tdmoe_packet_counter, tvb, offset, 2, ENC_BIG_ENDIAN);
	offset+=2;

	/* Number of channels in packet (2 bytes) */
	proto_tree_add_item(tdmoe_tree, hf_tdmoe_channels, tvb, offset, 2, ENC_BIG_ENDIAN);
	offset+=2;

	if (tvb_get_guint8(tvb, 3) & TDMOE_SIGBITS_BITMASK) {
		/* 4 sigbits per channel. Might be different on other sub-protocols? */
		guint16 length = (channels >> 1) + ((channels & 0x01) ? 1 : 0);

		proto_tree_add_item(tdmoe_tree, hf_tdmoe_sig_bits, tvb, offset, length, ENC_NA);
		offset += length;
	}

	/* The rest is SAMPLES * CHANNELS bytes of channel data */
	for (chan = 1; chan <= channels; chan++) {
		next_client = tvb_new_subset_length(tvb, offset + ((chan - 1) * 8), 8);
		if (chan == pref_tdmoe_d_channel) {
			call_dissector(lapd_handle, next_client, pinfo, tree);
		} else {
			call_data_dissector(next_client, pinfo, tree);
		}
	}
	return 1;
}

void
proto_register_tdmoe(void)
{
	static hf_register_info hf[] = {

		{ &hf_tdmoe_subaddress,
		  { "Subaddress",	"tdmoe.subaddress", FT_UINT8, BASE_DEC, NULL, 0x0,
		    NULL, HFILL }},
		{ &hf_tdmoe_samples,
		  { "Samples",	"tdmoe.samples", FT_UINT8, BASE_DEC, NULL, 0x0,
		    "Samples per channel", HFILL }},
		{ &hf_tdmoe_flags,
		  { "Flags",	"tdmoe.flags", FT_UINT8, BASE_HEX, NULL, 0x0,
		    NULL, HFILL }},
		{ &hf_tdmoe_yellow_alarm,
		  { "Yellow Alarm", "tdmoe.yellowalarm", FT_BOOLEAN, 8, NULL, TDMOE_YELLOW_ALARM_BITMASK,
		    NULL, HFILL }},
		{ &hf_tdmoe_sig_bits_present,
		  { "Sig bits present", "tdmoe.sig_bits_present", FT_BOOLEAN, 8, NULL, TDMOE_SIGBITS_BITMASK,
		    NULL, HFILL }},
		{ &hf_tdmoe_packet_counter,
		  { "Counter", "tdmoe.counter", FT_UINT16, BASE_DEC, NULL, 0x0,
		    "Packet number", HFILL }},
		{ &hf_tdmoe_channels,
		  { "Channels", "tdmoe.channels", FT_UINT16, BASE_DEC, NULL, 0x0,
		    NULL, HFILL }},
		{ &hf_tdmoe_sig_bits,
		  { "Sig bits", "tdmoe.sig_bits", FT_BYTES, BASE_NONE, NULL, 0x0,
		    NULL, HFILL }},
	};
	static gint *ett[] = {
		&ett_tdmoe,
		&ett_tdmoe_flags
	};
	module_t *tdmoe_module;

	proto_tdmoe = proto_register_protocol("Digium TDMoE Protocol", "TDMoE", "tdmoe");
	proto_register_field_array(proto_tdmoe, hf, array_length(hf));
	proto_register_subtree_array(ett, array_length(ett));
	tdmoe_module = prefs_register_protocol(proto_tdmoe, proto_reg_handoff_tdmoe);
	prefs_register_uint_preference(tdmoe_module, "d_channel",
				       "TDMoE D-Channel",
				       "The TDMoE channel that contains the D-Channel.",
				       10, &pref_tdmoe_d_channel);
}

void
proto_reg_handoff_tdmoe(void)
{
	dissector_handle_t tdmoe_handle;

	tdmoe_handle = create_dissector_handle(dissect_tdmoe, proto_tdmoe);
	dissector_add_uint("ethertype", ETHERTYPE_TDMOE, tdmoe_handle);

	lapd_handle = find_dissector_add_dependency("lapd-bitstream", proto_tdmoe);
}

/*
 * Editor modelines  -  https://www.wireshark.org/tools/modelines.html
 *
 * Local variables:
 * c-basic-offset: 8
 * tab-width: 8
 * indent-tabs-mode: t
 * End:
 *
 * vi: set shiftwidth=8 tabstop=8 noexpandtab:
 * :indentSize=8:tabSize=8:noTabs=false:
 */