/*

 * tinc.c

 *

 * Copyright (C) 2017 - William Guglielmo <william@deselmo.com>

 * Copyright (C) 2017-22 - 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_TINC

#include "ndpi_api.h"

#include "libcache.h"

PACK_ON struct tinc_cache_entry {

  u_int32_t src_address;

  u_int32_t dst_address;

  u_int16_t dst_port;

} PACK_OFF;

static void ndpi_check_tinc(struct ndpi_detection_module_struct *ndpi_struct, struct ndpi_flow_struct *flow)

{

  struct ndpi_packet_struct *packet = &ndpi_struct->packet;

  const u_int8_t *packet_payload = packet->payload;

  u_int32_t payload_len = packet->payload_packet_len;

  if(packet->udp != NULL) {

    if(ndpi_struct->tinc_cache != NULL) {

      struct tinc_cache_entry tinc_cache_entry1 = {

        .src_address = packet->iph->saddr,

        .dst_address = packet->iph->daddr,

        .dst_port = packet->udp->dest

      };

      struct tinc_cache_entry tinc_cache_entry2 = {

        .src_address = packet->iph->daddr,

        .dst_address = packet->iph->saddr,

        .dst_port = packet->udp->source

      };

      if(cache_remove(ndpi_struct->tinc_cache, &tinc_cache_entry1, sizeof(tinc_cache_entry1)) == CACHE_NO_ERROR ||

   cache_remove(ndpi_struct->tinc_cache, &tinc_cache_entry2, sizeof(tinc_cache_entry2)) == CACHE_NO_ERROR) {

        cache_remove(ndpi_struct->tinc_cache, &tinc_cache_entry1, sizeof(tinc_cache_entry1));

        cache_remove(ndpi_struct->tinc_cache, &tinc_cache_entry2, sizeof(tinc_cache_entry2));

  /* cache_free(ndpi_struct->tinc_cache); */

        NDPI_LOG_INFO(ndpi_struct, "found tinc udp connection\n");

        ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_TINC, NDPI_PROTOCOL_UNKNOWN, NDPI_CONFIDENCE_DPI_CACHE);

      }

    }

    NDPI_EXCLUDE_PROTO(ndpi_struct, flow);

    return;

  } else if(packet->tcp != NULL) {

    switch(flow->tinc_state) {

    case 0:

    case 1:

      if(payload_len > 6 && memcmp(packet_payload, "0 ", 2) == 0 && packet_payload[2] != ' ') {

  u_int32_t i = 3;

  while(i < payload_len && packet_payload[i++] != ' ');

  if(i+3 == payload_len && memcmp((packet_payload+i), "17\n", 3) == 0) {

    flow->tinc_state++;

    return;

  }

      }

      break;

    case 2:

    case 3:

      if(payload_len > 11 && memcmp(packet_payload, "1 ", 2) == 0 && packet_payload[2] != ' ') {

  u_int16_t i = 3;

  u_int8_t numbers_left = 4;

  while(numbers_left) {

    while(i < payload_len && packet_payload[i] >= '0' && packet_payload[i] <= '9') {

      i++;

    }

    if(i < payload_len && packet_payload[i++] == ' ') {

      numbers_left--;

    }

    else break;

  }

  if(numbers_left) break;

  while(i < payload_len &&

        ((packet_payload[i] >= '0' && packet_payload[i] <= '9') ||

         (packet_payload[i] >= 'A' && packet_payload[i] <= 'Z'))) {

    i++;

  }

  if(i < payload_len && packet_payload[i] == '\n') {

    if(++flow->tinc_state > 3) {

      struct tinc_cache_entry tinc_cache_entry = {

        .src_address = flow->c_address.v4,

        .dst_address = flow->s_address.v4,

        .dst_port = flow->s_port,

      };

      if(ndpi_struct->tinc_cache == NULL)

        ndpi_struct->tinc_cache = cache_new(TINC_CACHE_MAX_SIZE);              

      cache_add(ndpi_struct->tinc_cache, &tinc_cache_entry, sizeof(tinc_cache_entry));

      NDPI_LOG_INFO(ndpi_struct, "found tinc tcp connection\n");

      ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_TINC, NDPI_PROTOCOL_UNKNOWN, NDPI_CONFIDENCE_DPI);

    }

    return;

  }

      }

      break;

    default: break;

    }

  }

  NDPI_EXCLUDE_PROTO(ndpi_struct, flow);

}

static void ndpi_search_tinc(struct ndpi_detection_module_struct* ndpi_struct, struct ndpi_flow_struct* flow) {

  NDPI_LOG_DBG(ndpi_struct, "tinc detection\n");

  if(flow->detected_protocol_stack[0] != NDPI_PROTOCOL_TINC) {

    ndpi_check_tinc(ndpi_struct, flow);

  }

}

void init_tinc_dissector(struct ndpi_detection_module_struct *ndpi_struct, u_int32_t *id)

{

  ndpi_set_bitmask_protocol_detection("TINC", ndpi_struct, *id,

              NDPI_PROTOCOL_TINC,

              ndpi_search_tinc,

              NDPI_SELECTION_BITMASK_PROTOCOL_TCP_OR_UDP_WITH_PAYLOAD_WITHOUT_RETRANSMISSION, /* TODO: IPv6? */

              SAVE_DETECTION_BITMASK_AS_UNKNOWN,

              ADD_TO_DETECTION_BITMASK);

  *id += 1;

}