/*
 * tinc.c
 *
 * Copyright (C) 2017 - William Guglielmo <william@deselmo.com>
 * Copyright (C) 2017-18 - 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"


static void ndpi_check_tinc(struct ndpi_detection_module_struct *ndpi_struct, struct ndpi_flow_struct *flow)
{
    struct ndpi_packet_struct *packet = &flow->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);
            }
        }

        return;

    } else if(packet->tcp != NULL) {
        if(payload_len == 0) {
            if(packet->tcp->syn == 1 && packet->tcp->ack == 0) {
                flow->tinc_cache_entry.src_address = packet->iph->saddr;
                flow->tinc_cache_entry.dst_address = packet->iph->daddr;
                flow->tinc_cache_entry.dst_port = packet->tcp->dest;
            }
            return;
        }

        switch(flow->tinc_state) {
            case 0:
            case 1:
                if(payload_len > 6 && memcmp(packet_payload, "0 ", 2) == 0 && packet_payload[2] != ' ') {
                    u_int16_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(packet_payload[i] >= '0' && packet_payload[i] <= '9') {
                            i++;
                        }

                        if(packet_payload[i++] == ' ') {
                            numbers_left--;
                        }
                        else break;
                    }

                    if(numbers_left) break;

                    while((packet_payload[i] >= '0' && packet_payload[i] <= '9') ||
                            (packet_payload[i] >= 'A' && packet_payload[i] <= 'Z')) {
                        i++;
                    }

                    if(packet_payload[i] == '\n') {
                        if(++flow->tinc_state > 3) {
                            if(ndpi_struct->tinc_cache == NULL)
                                ndpi_struct->tinc_cache = cache_new(TINC_CACHE_MAX_SIZE);

                            cache_add(ndpi_struct->tinc_cache, &(flow->tinc_cache_entry), sizeof(flow->tinc_cache_entry));
                            NDPI_LOG_INFO(ndpi_struct, "found tinc tcp connection\n");
                            ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_TINC);
                        }
                        return;
                    }
                }
                break;

            default: break;
        }
    }

    NDPI_EXCLUDE_PROTO(ndpi_struct, flow);
}

void ndpi_search_tinc(struct ndpi_detection_module_struct* ndpi_struct, struct ndpi_flow_struct* flow) {
    struct ndpi_packet_struct* packet = &flow->packet;

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

    if(packet->detected_protocol != NDPI_PROTOCOL_TINC) {
        if(packet->tcp_retransmission == 0) {
            ndpi_check_tinc(ndpi_struct, flow);
        }
    }
}

void init_tinc_dissector(struct ndpi_detection_module_struct *ndpi_struct, u_int32_t *id, NDPI_PROTOCOL_BITMASK *detection_bitmask)
{
    ndpi_set_bitmask_protocol_detection("TINC", ndpi_struct, detection_bitmask, *id,
            NDPI_PROTOCOL_TINC,
            ndpi_search_tinc,
            NDPI_SELECTION_BITMASK_PROTOCOL_TCP_OR_UDP,
            SAVE_DETECTION_BITMASK_AS_UNKNOWN,
            ADD_TO_DETECTION_BITMASK);

    *id += 1;
}

