/*

 * bacnet.c

 *

 * Building Automation and Control Network

 *

 * Copyright (C) 2023 - ntop.org

 *

 * nDPI is free software: you can redistribute it and/or modify

 * it under the terms of the GNU Lesser General Public License as published by

 * the Free Software Foundation, either version 3 of the License, or

 * (at your option) any later version.

 *

 * nDPI is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public License

 * along with nDPI.  If not, see <http://www.gnu.org/licenses/>.

 *

 */

#include "ndpi_protocol_ids.h"

#define NDPI_CURRENT_PROTO NDPI_PROTOCOL_BACNET

#include "ndpi_api.h"

#include "ndpi_private.h"

// BVLC (BACnet Virtual Link Control) Annex is part of BVLL (BACnet Virtual Link Layer).

// See: https://www.ashrae.org/file%20library/technical%20resources/standards%20and%20guidelines/standards%20addenda/135-1995_addendum-a.pdf

PACK_ON

struct bvlc_header {

  uint8_t type;

  uint8_t function;

  uint16_t length;

} PACK_OFF;

static void ndpi_int_bacnet_add_connection(struct ndpi_detection_module_struct * const ndpi_struct,

                                           struct ndpi_flow_struct * const flow)

{

  NDPI_LOG_INFO(ndpi_struct, "found BACnet\n");

  ndpi_set_detected_protocol(ndpi_struct, flow,

                             NDPI_PROTOCOL_BACNET,

                             NDPI_PROTOCOL_UNKNOWN,

                             NDPI_CONFIDENCE_DPI);

}

/* ***************************************************** */

static void ndpi_search_bacnet(struct ndpi_detection_module_struct *ndpi_struct,

                               struct ndpi_flow_struct *flow)

{

  struct ndpi_packet_struct const * const packet = &ndpi_struct->packet;

  struct bvlc_header const * const bvlc = (struct bvlc_header *)&packet->payload[0];

  NDPI_LOG_DBG(ndpi_struct, "search BACnet\n");

  if (packet->payload_packet_len < sizeof(*bvlc))

  {

    NDPI_EXCLUDE_DISSECTOR(ndpi_struct, flow);

    return;

  }

  if (bvlc->type != 0x81)

  {

    NDPI_EXCLUDE_DISSECTOR(ndpi_struct, flow);

    return;

  }

  if (bvlc->function > 0x0b)

  {

    NDPI_EXCLUDE_DISSECTOR(ndpi_struct, flow);

    return;

  }

  if (ntohs(bvlc->length) != packet->payload_packet_len)

  {

    NDPI_EXCLUDE_DISSECTOR(ndpi_struct, flow);

    return;

  }

  ndpi_int_bacnet_add_connection(ndpi_struct, flow);

}

/* ***************************************************** */

void init_bacnet_dissector(struct ndpi_detection_module_struct *ndpi_struct)

{

  register_dissector("BACnet", ndpi_struct,

                     ndpi_search_bacnet,

                     NDPI_SELECTION_BITMASK_PROTOCOL_V4_V6_UDP_WITH_PAYLOAD,

                     1, NDPI_PROTOCOL_BACNET);

}