/*
 * h323.c
 *
 * Copyright (C) 2015-18 ntop.org
 * Copyright (C) 2013 Remy Mudingay <mudingay@ill.fr>
 *
 */

#include "ndpi_protocol_ids.h"

#define NDPI_CURRENT_PROTO NDPI_PROTOCOL_H323

#include "ndpi_api.h"


struct tpkt {
    u_int8_t version, reserved;
    u_int16_t len;
};

void ndpi_search_h323(struct ndpi_detection_module_struct *ndpi_struct, struct ndpi_flow_struct *flow)
{
    struct ndpi_packet_struct *packet = &flow->packet;
    u_int16_t dport = 0, sport = 0;

    NDPI_LOG_DBG(ndpi_struct, "search H323\n");

    if(packet->tcp != NULL) {
        NDPI_LOG_DBG2(ndpi_struct, "calculated dport over tcp\n");

        /* H323  */
        if(packet->payload_packet_len >= 3
                && (packet->payload[0] == 0x03)
                && (packet->payload[1] == 0x00)) {
            struct tpkt *t = (struct tpkt*)packet->payload;
            u_int16_t len = ntohs(t->len);

            if(packet->payload_packet_len == len) {
                /*
                   We need to check if this packet is in reality
                   a RDP (Remote Desktop) packet encapsulated on TPTK
                   */

                if(packet->payload[4] == (packet->payload_packet_len - sizeof(struct tpkt) - 1)) {
                    /* ISO 8073/X.224 */
                    if((packet->payload[5] == 0xE0 /* CC Connect Request */)
                            || (packet->payload[5] == 0xD0 /* CC Connect Confirm */)) {
                        NDPI_LOG_INFO(ndpi_struct, "found RDP\n");
                        ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_RDP);
                        return;
                    }
                }

                flow->l4.tcp.h323_valid_packets++;

                if(flow->l4.tcp.h323_valid_packets >= 2) {
                    NDPI_LOG_INFO(ndpi_struct, "found H323 broadcast\n");
                    ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_H323);
                }
            } else {
                /* This is not H.323 */
                NDPI_EXCLUDE_PROTO(ndpi_struct, flow);
                return;
            }
        }
    } else if(packet->udp != NULL) {
        sport = ntohs(packet->udp->source), dport = ntohs(packet->udp->dest);
        NDPI_LOG_DBG2(ndpi_struct, "calculated dport over udp\n");

        if(packet->payload_packet_len >= 6 && packet->payload[0] == 0x80 && packet->payload[1] == 0x08 &&
                (packet->payload[2] == 0xe7 || packet->payload[2] == 0x26) &&
                packet->payload[4] == 0x00 && packet->payload[5] == 0x00)
        {
            NDPI_LOG_INFO(ndpi_struct, "found H323 broadcast\n");
            ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_H323);
            return;
        }
        /* H323  */
        if(sport == 1719 || dport == 1719)
        {
            if(packet->payload[0] == 0x16 && packet->payload[1] == 0x80 && packet->payload[4] == 0x06 && packet->payload[5] == 0x00)
            {
                NDPI_LOG_INFO(ndpi_struct, "found H323 broadcast\n");
                ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_H323);
                return;
            }
            else if(packet->payload_packet_len >= 20 && packet->payload_packet_len <= 117)
            {
                NDPI_LOG_INFO(ndpi_struct, "found H323 broadcast\n");
                ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_H323);
                return;
            }
            else
            {
                NDPI_EXCLUDE_PROTO(ndpi_struct, flow);
                return;
            }
        }
    }

}

void init_h323_dissector(struct ndpi_detection_module_struct *ndpi_struct, u_int32_t *id, NDPI_PROTOCOL_BITMASK *detection_bitmask)
{
    ndpi_set_bitmask_protocol_detection("H323", ndpi_struct, detection_bitmask, *id,
            NDPI_PROTOCOL_H323,
            ndpi_search_h323,
            NDPI_SELECTION_BITMASK_PROTOCOL_TCP_OR_UDP_WITH_PAYLOAD,
            SAVE_DETECTION_BITMASK_AS_UNKNOWN,
            ADD_TO_DETECTION_BITMASK);

    *id += 1;
}
