/*
 * drda.c
 *
 * Copyright (C) 2012-18 - ntop.org
 *
 * This module 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.
 *
 * This module 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.
 * If not, see <http://www.gnu.org/licenses/>.
 *
 */
#include "ndpi_protocol_ids.h"

#define NDPI_CURRENT_PROTO NDPI_PROTOCOL_DRDA

#include "ndpi_api.h"


struct ndpi_drda_hdr {
    u_int16_t length;
    u_int8_t magic;
    u_int8_t format;
    u_int16_t correlID;
    u_int16_t length2;
    u_int16_t code_pnt;
};

void ndpi_search_drda(struct ndpi_detection_module_struct *ndpi_struct,
        struct ndpi_flow_struct *flow)
{
    struct ndpi_packet_struct * packet = &flow->packet;
    u_int16_t payload_len = packet->payload_packet_len;
    u_int count = 0; // prevent integer overflow

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

    if(packet->tcp != NULL) {

        /* check port */
        if(payload_len >= sizeof(struct ndpi_drda_hdr)) {

            struct ndpi_drda_hdr * drda = (struct ndpi_drda_hdr *) packet->payload;

            u_int16_t len = ntohs(drda->length);

            /* check first header */
            if(len != ntohs(drda->length2) + 6 ||
                    drda->magic != 0xd0)
                goto no_drda;

            /* check if there are more drda headers */
            if(payload_len > len) {

                count = len;

                while(count + sizeof(struct ndpi_drda_hdr) < payload_len)
                {
                    /* update info */
                    drda = (struct ndpi_drda_hdr *)(packet->payload + count);
                    len = ntohs(drda->length);

                    if(len != ntohs(drda->length2) + 6 ||
                            drda->magic != 0xd0)
                        goto no_drda;

                    count += len;
                }
                if(count != payload_len) goto no_drda;
            }
            NDPI_LOG_INFO(ndpi_struct, "found DRDA\n");
            ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_DRDA);
            return;
        }
    }

no_drda:
    NDPI_EXCLUDE_PROTO(ndpi_struct, flow);
}


/* ***************************************************************** */


void init_drda_dissector(struct ndpi_detection_module_struct *ndpi_struct, u_int32_t *id,
        NDPI_PROTOCOL_BITMASK *detection_bitmask)
{
    ndpi_set_bitmask_protocol_detection("DRDA", ndpi_struct, detection_bitmask, *id,
            NDPI_PROTOCOL_DRDA,
            ndpi_search_drda,
            NDPI_SELECTION_BITMASK_PROTOCOL_TCP_WITH_PAYLOAD,
            SAVE_DETECTION_BITMASK_AS_UNKNOWN,
            ADD_TO_DETECTION_BITMASK);

    *id += 1;
}
