/*

 * line.c

 *

 * Copyright (C) 2022-23 - 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_LINE_CALL

#include "ndpi_api.h"

extern int is_valid_rtp_payload_type(uint8_t type);

static void ndpi_int_line_add_connection(struct ndpi_detection_module_struct * const ndpi_struct,

                                         struct ndpi_flow_struct * const flow)

{

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

  ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_UNKNOWN,

                             NDPI_PROTOCOL_LINE_CALL, NDPI_CONFIDENCE_DPI);

}

static void ndpi_search_line(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, "searching LineCall\n");

  if(packet->iph && (flow->guessed_protocol_id_by_ip == NDPI_PROTOCOL_LINE)) {

    /*

      The heuristic below (coming from reverse engineering packet traces)

      will apply only to IPv4 and Line IP addresses. This is to avoid puttin

      false positives in other nDPI-decoded protocols.

    */

    if ((packet->payload_packet_len == 110 &&

   ndpi_struct->packet.payload[0] == 0xB6 &&  ndpi_struct->packet.payload[1] == 0x18 && ndpi_struct->packet.payload[2] == 0x00 && ndpi_struct->packet.payload[3] == 0x6A) ||

  (packet->payload_packet_len >= 738 && (ndpi_struct->packet.payload[0] == 0xDA || ndpi_struct->packet.payload[0] == 0xDB) &&

   ndpi_struct->packet.payload[4] == 0x06 && ndpi_struct->packet.payload[5] == 0x02) ||

  (packet->payload_packet_len >= 150 && (ndpi_struct->packet.payload[0] == 0xD9 || ndpi_struct->packet.payload[0] == 0xD8) &&

   ((ndpi_struct->packet.payload[1] & 0xF0) == 0x90 || (ndpi_struct->packet.payload[1] & 0xF0) == 0xD0 || (ndpi_struct->packet.payload[1] & 0xF0) == 0xE0) && ndpi_struct->packet.payload[4] == 0x06 &&

   ndpi_struct->packet.payload[5] == 0x02)) {

      ndpi_int_line_add_connection(ndpi_struct, flow);

      return;

    }

    if ((packet->payload_packet_len == 46 && ntohl(get_u_int32_t(packet->payload, 0)) == 0xb6130006) ||

  (packet->payload_packet_len == 8 && ntohl(get_u_int32_t(packet->payload, 0)) == 0xb6070004) ||

  (packet->payload_packet_len == 16 && ntohl(get_u_int32_t(packet->payload, 0)) == 0xb609000c) ||

  (packet->payload_packet_len >= 2 /* TODO */ && ndpi_struct->packet.payload[0] == 0xD0 &&

   (ndpi_struct->packet.payload[1] == 0xB3 || ndpi_struct->packet.payload[1] == 0xB4

    || ndpi_struct->packet.payload[1] == 0xDA || ndpi_struct->packet.payload[1] == 0xDB))) {

      ndpi_int_line_add_connection(ndpi_struct, flow);

      return;

    }

  }

  /* Some "random" UDP packets before the standard RTP stream:

     it seems that the 4th bytes of these packets is some kind of packet

     number. Look for 4 packets per direction with consecutive numbers. */

  if(packet->payload_packet_len > 10) {

    if(flow->l4.udp.line_pkts[packet->packet_direction] == 0) {

      flow->l4.udp.line_base_cnt[packet->packet_direction] = packet->payload[3];

      flow->l4.udp.line_pkts[packet->packet_direction] += 1;

      return;

    } else {

      /* It might be a RTP/RTCP packet. Ignore it and keep looking for the

         LINE packet numbers */

      /* Basic RTP detection */

      if((packet->payload[0] >> 6) == 2 && /* Version 2 */

         (packet->payload[1] == 201 || /* RTCP, Receiver Report */

          packet->payload[1] == 200 || /* RTCP, Sender Report */

          is_valid_rtp_payload_type(packet->payload[1] & 0x7F)) /* RTP */) {

        NDPI_LOG_DBG(ndpi_struct, "Probably RTP; keep looking for LINE");

        return;

      } else {

        if((u_int8_t)(flow->l4.udp.line_base_cnt[packet->packet_direction] +

                      flow->l4.udp.line_pkts[packet->packet_direction]) == packet->payload[3]) {

          flow->l4.udp.line_pkts[packet->packet_direction] += 1;

          if(flow->l4.udp.line_pkts[0] >= 4 && flow->l4.udp.line_pkts[1] >= 4) {

            /* To avoid false positives: usually "base pkt numbers" per-direction are different */

            if(flow->l4.udp.line_base_cnt[0] != flow->l4.udp.line_base_cnt[1])

              ndpi_int_line_add_connection(ndpi_struct, flow);

            else

              NDPI_EXCLUDE_PROTO(ndpi_struct, flow);

    }

          return;

        }

      }

    }

  }

  NDPI_EXCLUDE_PROTO(ndpi_struct, flow);

  return;

}

void init_line_dissector(struct ndpi_detection_module_struct *ndpi_struct,

                         u_int32_t *id)

{

  ndpi_set_bitmask_protocol_detection("LineCall", ndpi_struct, *id,

              NDPI_PROTOCOL_LINE_CALL,

              ndpi_search_line,

              NDPI_SELECTION_BITMASK_PROTOCOL_V4_V6_UDP_WITH_PAYLOAD,

              SAVE_DETECTION_BITMASK_AS_UNKNOWN,

              ADD_TO_DETECTION_BITMASK);

  *id += 1;

}