/*
 * vxlan.c
 *
 * Copyright (C) 2011-22 - 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_VXLAN

#include "ndpi_api.h"

/* This code handles VXLAN as per RFC 7348 */

struct vxlan_header {
  u_int8_t flags[4]; /* the first byte is flags, other three are reserved */
  u_int8_t vni[4];   /* the first three bytes are VNI, the last byte is reserved */
};

static void ndpi_check_vxlan(struct ndpi_detection_module_struct *ndpi_struct, struct ndpi_flow_struct *flow)
{
  struct ndpi_packet_struct *packet = &ndpi_struct->packet;
  u_int32_t payload_len = packet->payload_packet_len;

  if((packet->udp != NULL) && (payload_len >= sizeof(struct vxlan_header))) {
    u_int32_t vxlan_dst_port  = ntohs(4789);
    u_int32_t expected_flags = 0x08; /* only one bit should be set in the first byte */

    struct vxlan_header *vxlan = (struct vxlan_header *)packet->payload;

    if((packet->udp->dest == vxlan_dst_port) &&
      (vxlan->flags[0] == expected_flags) && (vxlan->flags[1] == 0x0) &&
      (vxlan->flags[2] == 0x0) && (vxlan->flags[3] == 0x0) &&
      (vxlan->vni[3] == 0x0)) {

      NDPI_LOG_INFO(ndpi_struct, "found vxlan\n");
      ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_VXLAN, NDPI_PROTOCOL_VXLAN, NDPI_CONFIDENCE_DPI);
      return;
    }
  }

  NDPI_EXCLUDE_PROTO(ndpi_struct, flow);
  return;
}

void ndpi_search_vxlan(struct ndpi_detection_module_struct *ndpi_struct, struct ndpi_flow_struct *flow)
{
  NDPI_LOG_DBG(ndpi_struct, "search vxlan\n");

  /* skip marked packets */
  if(flow->detected_protocol_stack[0] != NDPI_PROTOCOL_VXLAN)
    ndpi_check_vxlan(ndpi_struct, flow);
}

void init_vxlan_dissector(struct ndpi_detection_module_struct *ndpi_struct, u_int32_t *id, NDPI_PROTOCOL_BITMASK *detection_bitmask)
{
  ndpi_set_bitmask_protocol_detection("VXLAN", ndpi_struct, detection_bitmask, *id,
              NDPI_PROTOCOL_VXLAN,
              ndpi_search_vxlan,
              NDPI_SELECTION_BITMASK_PROTOCOL_V4_V6_UDP_WITH_PAYLOAD,
              SAVE_DETECTION_BITMASK_AS_UNKNOWN,
              ADD_TO_DETECTION_BITMASK);

  *id += 1;
}