path: root/epan/dissectors/packet-m2pa.c

/* packet-m2pa.c
 * Routines for MTP2 Peer Adaptation Layer dissection
 * It is hopefully (needs testing) compliant to
 * https://tools.ietf.org/html/draft-ietf-sigtran-m2pa-02
 * https://tools.ietf.org/html/draft-ietf-sigtran-m2pa-08
 * https://tools.ietf.org/html/rfc4165
 *
 * Copyright 2001, 2002, Jeff Morriss <jeff.morriss.ws [AT] gmail.com>,
 * updated by Michael Tuexen <tuexen [AT] fh-muenster.de>
 *
 * Wireshark - Network traffic analyzer
 * By Gerald Combs <gerald@wireshark.org>
 * Copyright 1998 Gerald Combs
 *
 * Copied from packet-m3ua.c
 *
 * SPDX-License-Identifier: GPL-2.0-or-later
 */


#include "config.h"

#include <epan/packet.h>
#include <epan/exceptions.h>
#include <epan/prefs.h>
#include <epan/sctpppids.h>
#include <epan/expert.h>

void proto_register_m2pa(void);
void proto_reg_handoff_m2pa(void);

#define SCTP_PORT_M2PA              3565

static int proto_m2pa;
static module_t *m2pa_module;

static int hf_version;
static int hf_spare;
static int hf_v2_type;
static int hf_v8_type;
static int hf_type;
static int hf_class;
static int hf_length;
static int hf_unused;
static int hf_bsn;
static int hf_fsn;
static int hf_v2_status;
static int hf_v8_status;
static int hf_status;
static int hf_v2_li_spare;
static int hf_v8_li_spare;
static int hf_v2_li_prio;
static int hf_v8_li_prio;
static int hf_filler;
static int hf_unknown_data;
static int hf_pri_prio;
static int hf_pri_spare;
static int hf_undecode_data;

static int ett_m2pa;
static int ett_m2pa_li;

static expert_field ei_undecode_data;
static expert_field ei_length;

static dissector_handle_t m2pa_handle;
static dissector_handle_t mtp3_handle;

typedef enum {
  M2PA_V02 = 1,
  M2PA_V08 = 2,
  M2PA_RFC4165 = 3
} Version_Type;

static int m2pa_version = M2PA_RFC4165;

#define VERSION_LENGTH         1
#define SPARE_LENGTH           1
#define CLASS_LENGTH           1
#define V2_TYPE_LENGTH         2
#define V8_TYPE_LENGTH         1
#define TYPE_LENGTH            V8_TYPE_LENGTH
#define LENGTH_LENGTH          4
#define UNUSED_LENGTH          1
#define BSN_LENGTH             3
#define FSN_LENGTH             3

#define V2_HEADER_LENGTH        (VERSION_LENGTH + SPARE_LENGTH + \
                                V2_TYPE_LENGTH + LENGTH_LENGTH)

#define V8_HEADER_LENGTH        (VERSION_LENGTH + SPARE_LENGTH + \
                                CLASS_LENGTH + V8_TYPE_LENGTH + LENGTH_LENGTH + \
                                UNUSED_LENGTH + BSN_LENGTH + UNUSED_LENGTH + \
                                FSN_LENGTH)
#define HEADER_LENGTH           V8_HEADER_LENGTH

#define HEADER_OFFSET          0
#define VERSION_OFFSET         HEADER_OFFSET
#define SPARE_OFFSET           (VERSION_OFFSET + VERSION_LENGTH)
#define CLASS_OFFSET           (SPARE_OFFSET + SPARE_LENGTH)
#define V2_TYPE_OFFSET         (SPARE_OFFSET + SPARE_LENGTH)
#define V8_TYPE_OFFSET         (CLASS_OFFSET + CLASS_LENGTH)
#define TYPE_OFFSET            V8_TYPE_OFFSET
#define V8_LENGTH_OFFSET       (V8_TYPE_OFFSET + V8_TYPE_LENGTH)
#define LENGTH_OFFSET          V8_LENGTH_OFFSET
#define V2_LENGTH_OFFSET       (V2_TYPE_OFFSET + V2_TYPE_LENGTH)
#define FIRST_UNUSED_OFFSET    (V8_LENGTH_OFFSET + LENGTH_LENGTH)
#define BSN_OFFSET             (FIRST_UNUSED_OFFSET + UNUSED_LENGTH)
#define SECOND_UNUSED_OFFSET   (BSN_OFFSET + BSN_LENGTH)
#define FSN_OFFSET             (SECOND_UNUSED_OFFSET + UNUSED_LENGTH)

static const value_string protocol_version_values[] = {
  { 1,      "Release 1" },
  { 0,      NULL } };

static const value_string message_class_values[] = {
  { 0xb,    "M2PA" },
  { 0,      NULL } };

#define V2_USER_DATA_TYPE   0x0601
#define V2_LINK_STATUS_TYPE 0x0602

static const value_string v2_message_type_values[] = {
  { V2_USER_DATA_TYPE,   "User Data" },
  { V2_LINK_STATUS_TYPE, "Link Status" },
  { 0,                   NULL } };

#define V8_USER_DATA_TYPE   0x0001
#define V8_LINK_STATUS_TYPE 0x0002

static const value_string v8_message_type_values[] = {
  { V8_USER_DATA_TYPE,   "User Data" },
  { V8_LINK_STATUS_TYPE, "Link Status" },
  { 0,                   NULL } };

#define USER_DATA_TYPE   V8_USER_DATA_TYPE
#define LINK_STATUS_TYPE V8_LINK_STATUS_TYPE

static const value_string message_type_values[] = {
  { USER_DATA_TYPE,   "User Data" },
  { LINK_STATUS_TYPE, "Link Status" },
  { 0,                NULL } };

static void
dissect_v2_header(tvbuff_t *header_tvb, packet_info *pinfo, proto_tree *m2pa_tree)
{
  uint16_t message_type;

  message_type  = tvb_get_ntohs(header_tvb, V2_TYPE_OFFSET);

  col_add_fstr(pinfo->cinfo, COL_INFO, "%s ", val_to_str_const(message_type, v2_message_type_values, "reserved"));

  proto_tree_add_item(m2pa_tree, hf_version, header_tvb, VERSION_OFFSET,       VERSION_LENGTH, ENC_BIG_ENDIAN);
  proto_tree_add_item(m2pa_tree, hf_spare,   header_tvb, SPARE_OFFSET,         SPARE_LENGTH,   ENC_BIG_ENDIAN);
  proto_tree_add_item(m2pa_tree, hf_v2_type, header_tvb, V2_TYPE_OFFSET,       V2_TYPE_LENGTH, ENC_BIG_ENDIAN);
  proto_tree_add_item(m2pa_tree, hf_length,  header_tvb, V2_LENGTH_OFFSET,     LENGTH_LENGTH,  ENC_BIG_ENDIAN);
}

static void
dissect_v8_header(tvbuff_t *header_tvb, packet_info *pinfo, proto_tree *m2pa_tree)
{
  uint8_t message_type;

  message_type  = tvb_get_uint8(header_tvb, V8_TYPE_OFFSET);

  col_add_fstr(pinfo->cinfo, COL_INFO, "%s ", val_to_str_const(message_type, v8_message_type_values, "Unknown"));

  proto_tree_add_item(m2pa_tree, hf_version, header_tvb, VERSION_OFFSET,       VERSION_LENGTH, ENC_BIG_ENDIAN);
  proto_tree_add_item(m2pa_tree, hf_spare,   header_tvb, SPARE_OFFSET,         SPARE_LENGTH,   ENC_BIG_ENDIAN);
  proto_tree_add_item(m2pa_tree, hf_class,   header_tvb, CLASS_OFFSET,         CLASS_LENGTH,   ENC_BIG_ENDIAN);
  proto_tree_add_item(m2pa_tree, hf_v8_type, header_tvb, V8_TYPE_OFFSET,       V8_TYPE_LENGTH, ENC_BIG_ENDIAN);
  proto_tree_add_item(m2pa_tree, hf_length,  header_tvb, V8_LENGTH_OFFSET,     LENGTH_LENGTH,  ENC_BIG_ENDIAN);
  proto_tree_add_item(m2pa_tree, hf_unused,  header_tvb, FIRST_UNUSED_OFFSET,  UNUSED_LENGTH,  ENC_BIG_ENDIAN);
  proto_tree_add_item(m2pa_tree, hf_bsn,     header_tvb, BSN_OFFSET,           BSN_LENGTH,     ENC_BIG_ENDIAN);
  proto_tree_add_item(m2pa_tree, hf_unused,  header_tvb, SECOND_UNUSED_OFFSET, UNUSED_LENGTH,  ENC_BIG_ENDIAN);
  proto_tree_add_item(m2pa_tree, hf_fsn,     header_tvb, FSN_OFFSET,           FSN_LENGTH,     ENC_BIG_ENDIAN);
}

static void
dissect_header(tvbuff_t *header_tvb, packet_info *pinfo, proto_tree *m2pa_tree)
{
  uint8_t message_type;

  message_type  = tvb_get_uint8(header_tvb, V8_TYPE_OFFSET);

  col_add_fstr(pinfo->cinfo, COL_INFO, "%s ", val_to_str_const(message_type, v8_message_type_values, "Unknown"));

  proto_tree_add_item(m2pa_tree, hf_version,  header_tvb, VERSION_OFFSET,       VERSION_LENGTH,  ENC_BIG_ENDIAN);
  proto_tree_add_item(m2pa_tree, hf_spare,    header_tvb, SPARE_OFFSET,         SPARE_LENGTH,    ENC_BIG_ENDIAN);
  proto_tree_add_item(m2pa_tree, hf_class,    header_tvb, CLASS_OFFSET,         CLASS_LENGTH,    ENC_BIG_ENDIAN);
  proto_tree_add_item(m2pa_tree, hf_type,     header_tvb, TYPE_OFFSET,          TYPE_LENGTH,     ENC_BIG_ENDIAN);
  proto_tree_add_item(m2pa_tree, hf_length,   header_tvb, LENGTH_OFFSET,        LENGTH_LENGTH,   ENC_BIG_ENDIAN);
  proto_tree_add_item(m2pa_tree, hf_unused,   header_tvb, FIRST_UNUSED_OFFSET,  UNUSED_LENGTH,   ENC_BIG_ENDIAN);
  proto_tree_add_item(m2pa_tree, hf_bsn,      header_tvb, BSN_OFFSET,           BSN_LENGTH,      ENC_BIG_ENDIAN);
  proto_tree_add_item(m2pa_tree, hf_unused,   header_tvb, SECOND_UNUSED_OFFSET, UNUSED_LENGTH,   ENC_BIG_ENDIAN);
  proto_tree_add_item(m2pa_tree, hf_fsn,      header_tvb, FSN_OFFSET,           FSN_LENGTH,      ENC_BIG_ENDIAN);
}

#define LI_OFFSET           0
#define LI_LENGTH           1
#define MTP3_OFFSET         (LI_OFFSET + LI_LENGTH)

#define V2_LI_SPARE_MASK    0xfc
#define V2_LI_PRIORITY_MASK 0x3

static void
dissect_v2_user_data_message(tvbuff_t *message_data_tvb, packet_info *pinfo, proto_item *m2pa_item, proto_tree *m2pa_tree, proto_tree *tree)
{
  proto_tree *m2pa_li_tree;
  tvbuff_t *payload_tvb;

  if (tvb_reported_length(message_data_tvb) > 0) {
    m2pa_li_tree = proto_tree_add_subtree(m2pa_tree, message_data_tvb, LI_OFFSET, LI_LENGTH, ett_m2pa_li, NULL, "Length Indicator");

    proto_tree_add_item(m2pa_li_tree, hf_v2_li_spare, message_data_tvb, LI_OFFSET, LI_LENGTH, ENC_BIG_ENDIAN);
    proto_tree_add_item(m2pa_li_tree, hf_v2_li_prio,  message_data_tvb, LI_OFFSET, LI_LENGTH, ENC_BIG_ENDIAN);

    /* Re-adjust length of M2PA item since it will be dissected as MTP3 */
    proto_item_set_len(m2pa_item, V2_HEADER_LENGTH + LI_LENGTH);
  }

  payload_tvb = tvb_new_subset_remaining(message_data_tvb, MTP3_OFFSET);
  call_dissector(mtp3_handle, payload_tvb, pinfo, tree);
}

#define V8_LI_SPARE_MASK        0x3f
#define V8_LI_PRIORITY_MASK     0xc0

static void
dissect_v8_user_data_message(tvbuff_t *message_data_tvb, packet_info *pinfo, proto_item *m2pa_item, proto_tree *m2pa_tree, proto_tree *tree)
{
  proto_tree *m2pa_li_tree;
  tvbuff_t *payload_tvb;

  if (tvb_reported_length(message_data_tvb) > 0) {
    m2pa_li_tree = proto_tree_add_subtree(m2pa_tree, message_data_tvb, LI_OFFSET, LI_LENGTH, ett_m2pa_li, NULL, "Length Indicator");
    proto_tree_add_item(m2pa_li_tree, hf_v8_li_prio,  message_data_tvb, LI_OFFSET, LI_LENGTH, ENC_BIG_ENDIAN);
    proto_tree_add_item(m2pa_li_tree, hf_v8_li_spare, message_data_tvb, LI_OFFSET, LI_LENGTH, ENC_BIG_ENDIAN);

    /* Re-adjust length of M2PA item since it will be dissected as MTP3 */
    proto_item_set_len(m2pa_item, V8_HEADER_LENGTH + LI_LENGTH);

    payload_tvb = tvb_new_subset_remaining(message_data_tvb, MTP3_OFFSET);
    call_dissector(mtp3_handle, payload_tvb, pinfo, tree);
  }
}

#define PRIORITY_MASK     0xc0
#define SPARE_MASK        0x3f

#define PRI_OFFSET           0
#define PRI_LENGTH           1

static void
dissect_user_data_message(tvbuff_t *message_data_tvb, packet_info *pinfo, proto_item *m2pa_item, proto_tree *m2pa_tree, proto_tree *tree)
{
  proto_tree *m2pa_li_tree;
  tvbuff_t *payload_tvb;

  if (tvb_reported_length(message_data_tvb) > 0) {
    m2pa_li_tree = proto_tree_add_subtree(m2pa_tree, message_data_tvb, PRI_OFFSET, PRI_LENGTH, ett_m2pa_li, NULL, "Priority");
    proto_tree_add_item(m2pa_li_tree, hf_pri_prio,  message_data_tvb, PRI_OFFSET, PRI_LENGTH, ENC_BIG_ENDIAN);
    proto_tree_add_item(m2pa_li_tree, hf_pri_spare, message_data_tvb, PRI_OFFSET, PRI_LENGTH, ENC_BIG_ENDIAN);

    /* Re-adjust length of M2PA item since it will be dissected as MTP3 */
    proto_item_set_len(m2pa_item, HEADER_LENGTH + PRI_LENGTH);

    payload_tvb = tvb_new_subset_remaining(message_data_tvb, MTP3_OFFSET);
    call_dissector(mtp3_handle, payload_tvb, pinfo, tree);
  }
}

static const value_string v2_link_status_values[] = {
  { 1, "In Service" },
  { 2, "Processor Outage" },
  { 3, "Processor Outage Ended" },
  { 4, "Busy" },
  { 5, "Busy Ended" },
  { 0, NULL } };

#define STATUS_LENGTH    4
#define STATUS_OFFSET    0
#define FILLER_OFFSET    (STATUS_OFFSET + STATUS_LENGTH)

static void
dissect_v2_link_status_message(tvbuff_t *message_data_tvb, packet_info *pinfo, proto_tree *m2pa_tree)
{
  col_append_fstr(pinfo->cinfo, COL_INFO, "(%s) ", val_to_str_const(tvb_get_ntohl(message_data_tvb, STATUS_OFFSET), v2_link_status_values, "Unknown"));
  proto_tree_add_item(m2pa_tree, hf_v2_status, message_data_tvb, STATUS_OFFSET, STATUS_LENGTH, ENC_BIG_ENDIAN);
}

static const value_string v8_link_status_values[] = {
  { 1, "Alignment" },
  { 2, "Proving Normal" },
  { 3, "Proving Emergency" },
  { 4, "Ready" },
  { 5, "Processor Outage" },
  { 6, "Processor Outage Ended" },
  { 7, "Busy" },
  { 8, "Busy Ended" },
  { 9, "Out of Service" },
  { 0, NULL } };

static void
dissect_v8_link_status_message(tvbuff_t *message_data_tvb, packet_info *pinfo, proto_tree *m2pa_tree)
{
  uint16_t filler_length;

  col_append_fstr(pinfo->cinfo, COL_INFO, "(%s) ", val_to_str_const(tvb_get_ntohl(message_data_tvb, STATUS_OFFSET), v8_link_status_values, "Unknown"));

  filler_length = tvb_reported_length(message_data_tvb) - STATUS_LENGTH;

  proto_tree_add_item(m2pa_tree, hf_v8_status, message_data_tvb, STATUS_OFFSET, STATUS_LENGTH, ENC_BIG_ENDIAN);
  if (filler_length > 0)
      proto_tree_add_item(m2pa_tree, hf_filler, message_data_tvb, FILLER_OFFSET, filler_length, ENC_NA);
}

static const value_string link_status_values[] = {
  { 1, "Alignment" },
  { 2, "Proving Normal" },
  { 3, "Proving Emergency" },
  { 4, "Ready" },
  { 5, "Processor Outage" },
  { 6, "Processor Outage Ended" },
  { 7, "Busy" },
  { 8, "Busy Ended" },
  { 9, "Out of Service" },
  { 0, NULL } };

static void
dissect_link_status_message(tvbuff_t *message_data_tvb, packet_info *pinfo, proto_tree *m2pa_tree)
{
  uint16_t filler_length;

  col_append_fstr(pinfo->cinfo, COL_INFO, "(%s) ", val_to_str_const(tvb_get_ntohl(message_data_tvb, STATUS_OFFSET), link_status_values, "Unknown"));

  filler_length = tvb_reported_length(message_data_tvb) - STATUS_LENGTH;

  proto_tree_add_item(m2pa_tree, hf_status, message_data_tvb, STATUS_OFFSET, STATUS_LENGTH, ENC_BIG_ENDIAN);
  if (filler_length > 0)
      proto_tree_add_item(m2pa_tree, hf_filler, message_data_tvb, FILLER_OFFSET, filler_length, ENC_NA);
}

static void
dissect_unknown_message(tvbuff_t *message_data_tvb, proto_tree *m2pa_tree)
{
  unsigned length;

  length = tvb_reported_length(message_data_tvb);
  if (length > 0)
    proto_tree_add_item(m2pa_tree, hf_unknown_data, message_data_tvb, 0, length, ENC_NA);
}

#define V2_MESSAGE_DATA_OFFSET (HEADER_OFFSET + V2_HEADER_LENGTH)

static void
dissect_v2_message_data(tvbuff_t *message_tvb, packet_info *pinfo, proto_item *m2pa_item, proto_tree *m2pa_tree, proto_tree *tree)
{
  uint32_t message_data_length;
  uint16_t type;
  tvbuff_t *message_data_tvb;

  message_data_length = tvb_get_ntohl(message_tvb, V2_LENGTH_OFFSET);
  if (message_data_length < 1 || message_data_length > INT_MAX) {
    proto_tree_add_expert_format(m2pa_tree, pinfo, &ei_length, message_tvb, V2_LENGTH_OFFSET, 4,
        "Invalid message data length: %u", message_data_length);
    return;
  }

  message_data_tvb    = tvb_new_subset_length(message_tvb, V2_MESSAGE_DATA_OFFSET, message_data_length);
  type                = tvb_get_ntohs(message_tvb, V2_TYPE_OFFSET);

  switch(type) {
  case V2_USER_DATA_TYPE:
    dissect_v2_user_data_message(message_data_tvb, pinfo, m2pa_item, m2pa_tree, tree);
    break;
  case V2_LINK_STATUS_TYPE:
    dissect_v2_link_status_message(message_data_tvb, pinfo, m2pa_tree);
    break;
  default:
    dissect_unknown_message(message_data_tvb, m2pa_tree);
  }
}

#define V8_MESSAGE_DATA_OFFSET (HEADER_OFFSET + V8_HEADER_LENGTH)

static void
dissect_v8_message_data(tvbuff_t *message_tvb, packet_info *pinfo, proto_item *m2pa_item, proto_tree *m2pa_tree, proto_tree *tree)
{
  uint32_t message_data_length;
  uint8_t type;
  tvbuff_t *message_data_tvb;

  message_data_length = tvb_get_ntohl(message_tvb, V8_LENGTH_OFFSET) - V8_HEADER_LENGTH;
  if (message_data_length < 1 || message_data_length > INT_MAX) {
    proto_tree_add_expert_format(m2pa_tree, pinfo, &ei_length, message_tvb, V8_LENGTH_OFFSET, 4,
        "Invalid message data length: %u", message_data_length);
    return;
  }
  message_data_tvb    = tvb_new_subset_length(message_tvb, V8_MESSAGE_DATA_OFFSET, message_data_length);
  type                = tvb_get_uint8(message_tvb, V8_TYPE_OFFSET);


  switch(type) {
  case V8_USER_DATA_TYPE:
    dissect_v8_user_data_message(message_data_tvb, pinfo, m2pa_item, m2pa_tree, tree);
    break;
  case V8_LINK_STATUS_TYPE:
    dissect_v8_link_status_message(message_data_tvb, pinfo, m2pa_tree);
    break;
  default:
    dissect_unknown_message(message_data_tvb, m2pa_tree);
  }
}

#define MESSAGE_DATA_OFFSET (HEADER_OFFSET + HEADER_LENGTH)

static void
dissect_message_data(tvbuff_t *message_tvb, packet_info *pinfo, proto_item *m2pa_item, proto_tree *m2pa_tree, proto_tree *tree)
{
  uint32_t length, message_data_length, actual_length;
  uint8_t type;
  tvbuff_t *message_data_tvb;

  length              = tvb_get_ntohl(message_tvb, LENGTH_OFFSET);
  message_data_length = length - HEADER_LENGTH;
  message_data_tvb    = tvb_new_subset_length(message_tvb, MESSAGE_DATA_OFFSET, message_data_length);
  type                = tvb_get_uint8(message_tvb, TYPE_OFFSET);


  switch(type) {
  case USER_DATA_TYPE:
    dissect_user_data_message(message_data_tvb, pinfo, m2pa_item, m2pa_tree, tree);
    break;
  case LINK_STATUS_TYPE:
    dissect_link_status_message(message_data_tvb, pinfo, m2pa_tree);
    break;
  default:
    dissect_unknown_message(message_data_tvb, m2pa_tree);
  }

  actual_length = tvb_reported_length(message_tvb);

  if (actual_length > length)
  {
    proto_item *pi;

    pi = proto_tree_add_item(m2pa_tree, hf_undecode_data, message_tvb, length, (actual_length - length), ENC_NA);
    expert_add_info_format(pinfo, pi, &ei_undecode_data,
                           "There are %d bytes of data which is greater than M2PA's length parameter (%d)",
                           actual_length, length);
  }
}

static void
dissect_v2_message(tvbuff_t *message_tvb, packet_info *pinfo, proto_item *m2pa_item, proto_tree *m2pa_tree, proto_tree *tree)
{
  dissect_v2_header(message_tvb, pinfo, m2pa_tree);
  dissect_v2_message_data(message_tvb, pinfo, m2pa_item, m2pa_tree, tree);
}

static void
dissect_v8_message(tvbuff_t *message_tvb, packet_info *pinfo, proto_item *m2pa_item, proto_tree *m2pa_tree, proto_tree *tree)
{
  dissect_v8_header(message_tvb, pinfo, m2pa_tree);
  dissect_v8_message_data(message_tvb, pinfo, m2pa_item, m2pa_tree, tree);
}

static void
dissect_message(tvbuff_t *message_tvb, packet_info *pinfo, proto_item *m2pa_item, proto_tree *m2pa_tree, proto_tree *tree)
{
  dissect_header(message_tvb, pinfo, m2pa_tree);
  dissect_message_data(message_tvb, pinfo, m2pa_item, m2pa_tree, tree);
}

static int
dissect_m2pa(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_)
{
  proto_item *m2pa_item;
  proto_tree *m2pa_tree;

  switch(m2pa_version) {
  case M2PA_V02:
    col_set_str(pinfo->cinfo, COL_PROTOCOL, "M2PA (ID 02)");
    break;
  case M2PA_V08:
    col_set_str(pinfo->cinfo, COL_PROTOCOL, "M2PA (ID 08)");
    break;
  case M2PA_RFC4165:
    col_set_str(pinfo->cinfo, COL_PROTOCOL, "M2PA");
    break;
  };

  m2pa_item = proto_tree_add_item(tree, proto_m2pa, tvb, 0, -1, ENC_NA);
  m2pa_tree = proto_item_add_subtree(m2pa_item, ett_m2pa);

  switch(m2pa_version) {
    case M2PA_V02:
      dissect_v2_message(tvb, pinfo, m2pa_item, m2pa_tree, tree);
      break;
    case M2PA_V08:
      dissect_v8_message(tvb, pinfo, m2pa_item, m2pa_tree, tree);
      break;
    case M2PA_RFC4165:
      dissect_message(tvb, pinfo, m2pa_item, m2pa_tree, tree);
      break;
  };
  return tvb_captured_length(tvb);
}

void
proto_register_m2pa(void)
{
  static hf_register_info hf[] =
  { { &hf_version,      { "Version",        "m2pa.version",        FT_UINT8,  BASE_DEC,  VALS(protocol_version_values), 0x0,                 NULL, HFILL} },
    { &hf_spare,        { "Spare",          "m2pa.spare",          FT_UINT8,  BASE_HEX,  NULL,                          0x0,                 NULL, HFILL} },
    { &hf_v2_type,      { "Message Type",   "m2pa.type_v2",        FT_UINT16, BASE_HEX,  VALS(v2_message_type_values),  0x0,                 NULL, HFILL} },
    { &hf_v8_type,      { "Message Type",   "m2pa.type_v8",        FT_UINT8,  BASE_DEC,  VALS(v8_message_type_values),  0x0,                 NULL, HFILL} },
    { &hf_type,         { "Message Type",   "m2pa.type",           FT_UINT8,  BASE_DEC,  VALS(message_type_values),     0x0,                 NULL, HFILL} },
    { &hf_class,        { "Message Class",  "m2pa.class",          FT_UINT8,  BASE_DEC,  VALS(message_class_values),    0x0,                 NULL, HFILL} },
    { &hf_length,       { "Message length", "m2pa.length",         FT_UINT32, BASE_DEC,  NULL,                          0x0,                 NULL, HFILL} },
    { &hf_unused,       { "Unused",         "m2pa.unused",         FT_UINT8,  BASE_DEC,  NULL,                          0x0,                 NULL, HFILL} },
    { &hf_bsn,          { "BSN",            "m2pa.bsn",            FT_UINT24, BASE_DEC,  NULL,                          0x0,                 NULL, HFILL} },
    { &hf_fsn,          { "FSN",            "m2pa.fsn",            FT_UINT24, BASE_DEC,  NULL,                          0x0,                 NULL, HFILL} },
    { &hf_v2_li_spare,  { "Spare",          "m2pa.li_spare_v2",    FT_UINT8,  BASE_DEC,  NULL,                          V2_LI_SPARE_MASK,    NULL, HFILL} },
    { &hf_v8_li_spare,  { "Spare",          "m2pa.li_spare_v8",    FT_UINT8,  BASE_HEX,  NULL,                          V8_LI_SPARE_MASK,    NULL, HFILL} },
    { &hf_pri_spare,    { "Spare",          "m2pa.priority_spare", FT_UINT8,  BASE_HEX,  NULL,                          SPARE_MASK,          NULL, HFILL} },
    { &hf_v2_li_prio,   { "Priority",       "m2pa.li_priority_v2", FT_UINT8,  BASE_DEC,  NULL,                          V2_LI_PRIORITY_MASK, NULL, HFILL} },
    { &hf_v8_li_prio,   { "Priority",       "m2pa.li_priority_v8", FT_UINT8,  BASE_HEX,  NULL,                          V8_LI_PRIORITY_MASK, NULL, HFILL} },
    { &hf_pri_prio,     { "Priority",       "m2pa.priority",       FT_UINT8,  BASE_HEX,  NULL,                          PRIORITY_MASK,       NULL, HFILL} },
    { &hf_v2_status,    { "Link Status",    "m2pa.status_v2",      FT_UINT32, BASE_DEC,  VALS(v2_link_status_values),   0x0,                 NULL, HFILL} },
    { &hf_v8_status,    { "Link Status",    "m2pa.status_v8",      FT_UINT32, BASE_DEC,  VALS(v8_link_status_values),   0x0,                 NULL, HFILL} },
    { &hf_status,       { "Link Status",    "m2pa.status",         FT_UINT32, BASE_DEC,  VALS(link_status_values),      0x0,                 NULL, HFILL} },
    { &hf_filler,       { "Filler",         "m2pa.filler",         FT_BYTES,  BASE_NONE, NULL,                          0x0,                 NULL, HFILL} },
    { &hf_unknown_data, { "Unknown Data",   "m2pa.unknown_data",   FT_BYTES,  BASE_NONE, NULL,                          0x0,                 NULL, HFILL} },
    { &hf_undecode_data,{ "Undecoded data", "m2pa.undecoded_data", FT_BYTES,  BASE_NONE, NULL,                          0x0,                 NULL, HFILL} }
  };

  static int *ett[] = {
    &ett_m2pa,
    &ett_m2pa_li
  };

  static const enum_val_t m2pa_version_options[] = {
    { "draft-2",  "Internet Draft version 2",  M2PA_V02     },
    { "draft-8",  "Internet Draft version 8",  M2PA_V08     },
    { "RFC4165",  "RFC 4165",                  M2PA_RFC4165 },
    { NULL, NULL, 0 }
  };

  static ei_register_info ei[] = {
     { &ei_undecode_data, { "m2pa.undecoded_data.expert", PI_MALFORMED, PI_WARN, "There are bytes of data which is greater than M2PA's length parameter", EXPFILL }},
     { &ei_length, { "m2pa.length.invalid", PI_MALFORMED, PI_ERROR, "Invalid message data length", EXPFILL }},
  };

  expert_module_t* expert_m2pa;

  proto_m2pa = proto_register_protocol("MTP2 Peer Adaptation Layer", "M2PA", "m2pa");

  proto_register_field_array(proto_m2pa, hf, array_length(hf));
  proto_register_subtree_array(ett, array_length(ett));
  expert_m2pa = expert_register_protocol(proto_m2pa);
  expert_register_field_array(expert_m2pa, ei, array_length(ei));

  /* Allow other dissectors to find this one by name. */
  m2pa_handle = register_dissector("m2pa", dissect_m2pa, proto_m2pa);

  m2pa_module = prefs_register_protocol(proto_m2pa, NULL);

  prefs_register_enum_preference(m2pa_module, "version", "M2PA version", "Version used by Wireshark", &m2pa_version, m2pa_version_options, false);
}

void
proto_reg_handoff_m2pa(void)
{
  mtp3_handle   = find_dissector_add_dependency("mtp3", proto_m2pa);

  dissector_add_uint("sctp.ppi", M2PA_PAYLOAD_PROTOCOL_ID, m2pa_handle);
  dissector_add_uint_with_preference("sctp.port", SCTP_PORT_M2PA, m2pa_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:
 */