/*

 * fins.c

 *

 * Factory Interface Network Service

 *

 * Copyright (C) 2023 - ntop.org

 * Copyright (C) V.G <v.gavrilov@securitycode.ru>

 *

 * 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_FINS

#include "ndpi_api.h"

#include "ndpi_private.h"

struct fins_hdr {

  u_int8_t icf; /* Information Control Field */

  u_int8_t rsv; /* Reserved, must be set to 0 */

  u_int8_t gct; /* Permissible number of gateways */

  u_int8_t dna; /* Destination network address */

  u_int8_t da1; /* Destination node address */

  u_int8_t da2; /* Destination unit address */

  u_int8_t sna; /* Source network address */

  u_int8_t sa1; /* Source node address */

  u_int8_t sa2; /* Source unit address */

  u_int8_t sid; /* Service ID */

};

static void ndpi_int_fins_add_connection(struct ndpi_detection_module_struct * const ndpi_struct,

                                         struct ndpi_flow_struct * const flow)

{

  ndpi_set_detected_protocol(ndpi_struct, flow,

                             NDPI_PROTOCOL_FINS,

                             NDPI_PROTOCOL_UNKNOWN,

                             NDPI_CONFIDENCE_DPI);

}

static void ndpi_search_fins(struct ndpi_detection_module_struct *ndpi_struct,

                             struct ndpi_flow_struct *flow)

{

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

  NDPI_LOG_DBG(ndpi_struct, "search Omron FINS\n");

  /* FINS/TCP header is 20 bytes long, but it's usually followed

   * by 10 byte FINS header and command data

   */

  if (packet->tcp != NULL && packet->payload_packet_len >= 20) {

    /* The FINS/TCP header always contains the

     * 4 byte ASCII magic value 'FINS'

     */

    if (memcmp(packet->payload, "FINS", 4) == 0) {

      NDPI_LOG_INFO(ndpi_struct, "found FINS over TCP\n");

      ndpi_int_fins_add_connection(ndpi_struct, flow);

      return;

    }

  } else if ((packet->udp != NULL) &&

             (packet->payload_packet_len > sizeof(struct fins_hdr)))

  {

    struct fins_hdr const * const fins = (struct fins_hdr *)packet->payload;

    /* 0x80 - command, response required

     * 0xC0 - response, response not required

     * 0xC1 - response, response required

     */

    if ((fins->icf != 0x80) && (fins->icf != 0xC0) && 

        (fins->icf != 0xC1))

    {

      goto not_fins;

    }

    if ((fins->dna > 0x7F)  || (fins->sna > 0x7F) ||

        (fins->gct != 0x02) || (fins->rsv != 0)) 

    {

      goto not_fins;

    }

    if ((fins->da2 == 0x00) || (fins->da2 == 0xFE) ||

        (fins->da2 == 0xE1) || ((fins->da2 >= 0x10) && 

        (fins->da2 <= 0x1F)))

    {

      if ((fins->sa2 == 0x00) || (fins->sa2 == 0xFE) ||

          (fins->sa2 == 0xE1) || ((fins->sa2 >= 0x10) && 

          (fins->sa2 <= 0x1F)))

      {

        NDPI_LOG_INFO(ndpi_struct, "found FINS over UDP\n");

        ndpi_int_fins_add_connection(ndpi_struct, flow);

        return;

      }

    }

  }

not_fins:

  NDPI_EXCLUDE_DISSECTOR(ndpi_struct, flow);

}

void init_fins_dissector(struct ndpi_detection_module_struct *ndpi_struct)

{

  register_dissector("FINS", ndpi_struct,

                     ndpi_search_fins,

                     NDPI_SELECTION_BITMASK_PROTOCOL_V4_V6_TCP_OR_UDP_WITH_PAYLOAD_WITHOUT_RETRANSMISSION,

                     1, NDPI_PROTOCOL_FINS);

}