/*

 * kcp.c

 *

 * Copyright (C) 2024 - 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_KCP

#include "ndpi_api.h"

#include "ndpi_private.h"

PACK_ON

struct kcp_header {

  uint32_t conversation_id;

  uint8_t command;

  uint8_t fragment_count;

  uint16_t window_size;

  uint32_t timestamp;

  uint32_t serial_number;

  uint32_t unacknowledged_serial_number;

  uint32_t length;

  uint8_t data[];

} PACK_OFF;

enum kcp_commands {

  IKCP_CMD_PUSH = 81,

  IKCP_CMD_ACK  = 82,

  IKCP_CMD_WASK = 83,

  IKCP_CMD_WINS = 84

};

static void ndpi_int_kcp_add_connection(struct ndpi_detection_module_struct * const ndpi_struct,

                                        struct ndpi_flow_struct * const flow)

{

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

  ndpi_set_detected_protocol(ndpi_struct, flow,

                             NDPI_PROTOCOL_KCP,

                             NDPI_PROTOCOL_UNKNOWN,

                             NDPI_CONFIDENCE_DPI);

}

static void ndpi_search_kcp(struct ndpi_detection_module_struct *ndpi_struct,

                            struct ndpi_flow_struct *flow)

{

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

  struct kcp_header const * const kcp_header = (struct kcp_header *)packet->payload;

  NDPI_LOG_INFO(ndpi_struct, "search kcp\n");

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

  {

    NDPI_EXCLUDE_DISSECTOR(ndpi_struct, flow);

    return;

  }

  switch (kcp_header->command)

  {

    case IKCP_CMD_PUSH:

    case IKCP_CMD_ACK:

    case IKCP_CMD_WASK:

    case IKCP_CMD_WINS:

      break;

    default:

      NDPI_EXCLUDE_DISSECTOR(ndpi_struct, flow);

      return;

  }

  uint32_t const kcp_pdu_length = le32toh(kcp_header->length);

  if (kcp_pdu_length + sizeof(*kcp_header) != packet->payload_packet_len)

  {

    NDPI_EXCLUDE_DISSECTOR(ndpi_struct, flow);

    return;

  }

  ndpi_int_kcp_add_connection(ndpi_struct, flow);

}

void init_kcp_dissector(struct ndpi_detection_module_struct *ndpi_struct)

{

  ndpi_register_dissector("KCP", ndpi_struct,

                     ndpi_search_kcp,

                     NDPI_SELECTION_BITMASK_PROTOCOL_V4_V6_TCP_OR_UDP_WITH_PAYLOAD_WITHOUT_RETRANSMISSION,

                      1, NDPI_PROTOCOL_KCP);

}