/* 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);

static dissector_handle_t tdmoe_handle;

/* protocols and header fields */

static int proto_tdmoe;

static int hf_tdmoe_subaddress;

static int hf_tdmoe_samples;

static int hf_tdmoe_flags;

static int hf_tdmoe_yellow_alarm;

static int hf_tdmoe_sig_bits_present;

static int hf_tdmoe_packet_counter;

static int hf_tdmoe_channels;

static int hf_tdmoe_sig_bits;

static int ett_tdmoe;

static int ett_tdmoe_flags;

static dissector_handle_t lapd_handle;

static unsigned 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;

  uint16_t    channels;

  uint16_t    subaddress;

  int32_t offset = 0;

  static int * const flags[] = { &hf_tdmoe_yellow_alarm, &hf_tdmoe_sig_bits_present, NULL };

  /* 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_uint8(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_uint8(tvb, 3) & TDMOE_SIGBITS_BITMASK) {

    /* 4 sigbits per channel. Might be different on other sub-protocols? */

    uint16_t 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 (unsigned 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_UINT16, 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 int *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_handle = register_dissector("tdmoe", dissect_tdmoe, proto_tdmoe);

  tdmoe_module = prefs_register_protocol(proto_tdmoe, NULL);

  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_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:

 */