/*

 * capwap.c

 *

 * Copyright (C) 2019 - 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_CAPWAP

#include "ndpi_api.h"

#include "ndpi_private.h"

#define NDPI_CAPWAP_CONTROL_PORT 5246

#define NDPI_CAPWAP_DATA_PORT    5247

static void ndpi_int_capwap_add_connection(struct ndpi_detection_module_struct *ndpi_struct,

             struct ndpi_flow_struct *flow) {

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

}

static int is_capwap_multicast(const struct ndpi_packet_struct *packet)

{

  /* RFC 5115 Sec 3.3

     "The WTP MUST send the Discovery Request

      message to either the limited broadcast IP address (255.255.255.255),

      the well-known CAPWAP multicast address (224.0.1.140), or to the

      unicast IP address of the AC.  For IPv6 networks, since broadcast

      does not exist, the use of "All ACs multicast address" (FF0X:0:0:0:0:

      0:0:18C) is used instead.

  */

  if(packet->iph) {

    if((packet->iph->daddr == 0xFFFFFFFF) ||

       (ntohl(packet->iph->daddr) == 0XE000018C))

      return 1;

  } else if(packet->iphv6) {

    if(((ntohl(packet->iphv6->ip6_dst.u6_addr.u6_addr32[0] & 0xFFF0FFFF) == 0xFF000000)) &&

       (packet->iphv6->ip6_dst.u6_addr.u6_addr32[1] == 0) &&

       (packet->iphv6->ip6_dst.u6_addr.u6_addr32[2] == 0) &&

       (ntohl(packet->iphv6->ip6_dst.u6_addr.u6_addr32[3] == 0x0000018C)))

      return 1;

  }

  return 0;

}

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

static void ndpi_search_setup_capwap(struct ndpi_detection_module_struct *ndpi_struct,

             struct ndpi_flow_struct *flow) {

  struct ndpi_packet_struct *packet = &ndpi_struct->packet;

  u_int16_t sport, dport;

  sport = ntohs(packet->udp->source), dport = ntohs(packet->udp->dest);

  if((dport == NDPI_CAPWAP_CONTROL_PORT)

     && (is_capwap_multicast(packet))

     && (packet->payload_packet_len >= 16)

     && (packet->payload[0] == 0x0)

     && (packet->payload[8] == 6 /* Mac len */)

     )

    goto capwap_found;

  if(((sport == NDPI_CAPWAP_CONTROL_PORT) || (dport == NDPI_CAPWAP_CONTROL_PORT))

     && ((packet->payload[0] == 0x0) || (packet->payload[0] == 0x1))

     ) {

    u_int16_t msg_len, offset, to_add;

    if(packet->payload[0] == 0x0)

      offset = 13, to_add = 13;

    else

      offset = 15, to_add = 17;

    if (packet->payload_packet_len >= offset + sizeof(u_int16_t)) {

      msg_len = ntohs(*(u_int16_t*)&packet->payload[offset]);

      if((msg_len+to_add) == packet->payload_packet_len)

        goto capwap_found;

    }

  }

  if(

     (((dport == NDPI_CAPWAP_DATA_PORT) && (!is_capwap_multicast(packet))) || (sport == NDPI_CAPWAP_DATA_PORT))

     && (packet->payload_packet_len >= 16)

     && (packet->payload[0] == 0x0)

     ) {

    u_int8_t is_80211_data = (packet->payload[9] & 0x0C) >> 2;

    if((sport == NDPI_CAPWAP_DATA_PORT) && (is_80211_data == 2 /* IEEE 802.11 Data */))

      goto capwap_found;

    else if(dport == NDPI_CAPWAP_DATA_PORT) {

      u_int16_t msg_len = ntohs(*(u_int16_t*)&packet->payload[13]);

      if((packet->payload[8] == 1 /* Mac len */)

   || (packet->payload[8] == 6 /* Mac len */)

   || (packet->payload[8] == 4 /* Wireless len */)

   || ((msg_len+15) == packet->payload_packet_len))

  goto capwap_found;  

    }

  }

  NDPI_EXCLUDE_DISSECTOR(ndpi_struct, flow);

  return;

 capwap_found:

  ndpi_int_capwap_add_connection(ndpi_struct, flow);

}

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

{

  struct ndpi_packet_struct *packet = &ndpi_struct->packet;

  if(packet->udp && (flow->detected_protocol_stack[0] == NDPI_PROTOCOL_UNKNOWN))

    ndpi_search_setup_capwap(ndpi_struct, flow);

}

void init_capwap_dissector(struct ndpi_detection_module_struct *ndpi_struct)

{

  ndpi_register_dissector("CAPWAP", ndpi_struct,

                     ndpi_search_capwap,

                     NDPI_SELECTION_BITMASK_PROTOCOL_V4_V6_UDP_WITH_PAYLOAD,

                     1, NDPI_PROTOCOL_CAPWAP);

}