/*
 * snat_det.c - deterministic NAT
 *
 * Copyright (c) 2017 Cisco and/or its affiliates.
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at:
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/**
 * @file
 * @brief deterministic NAT
 */

#include <snat/snat_det.h>


/**
 * @brief Add/delete deterministic NAT mapping.
 *
 * Create bijective mapping of inside address to outside address and port range
 * pairs, with the purpose of enabling deterministic NAT to reduce logging in
 * CGN deployments.
 *
 * @param sm       SNAT main.
 * @param in_addr  Inside network address.
 * @param in_plen  Inside network prefix length.
 * @param out_addr Outside network address.
 * @param out_plen Outside network prefix length.
 * @param is_add   If 0 delete, otherwise add.
 */
int
snat_det_add_map (snat_main_t * sm, ip4_address_t * in_addr, u8 in_plen,
		  ip4_address_t * out_addr, u8 out_plen, int is_add)
{
  snat_det_map_t *det_map;
  static snat_det_session_t empty_snat_det_session = { 0 };
  snat_interface_t *i;

  pool_get (sm->det_maps, det_map);
  memset (det_map, 0, sizeof (*det_map));
  det_map->in_addr.as_u32 = in_addr->as_u32 & ip4_main.fib_masks[in_plen];
  det_map->in_plen = in_plen;
  det_map->out_addr.as_u32 = out_addr->as_u32 & ip4_main.fib_masks[out_plen];
  det_map->out_plen = out_plen;
  det_map->sharing_ratio = (1 << (32 - in_plen)) / (1 << (32 - out_plen));
  det_map->ports_per_host = (65535 - 1023) / det_map->sharing_ratio;

  vec_validate_init_empty (det_map->sessions,
			   SNAT_DET_SES_PER_USER * (1 << (32 - in_plen)) - 1,
			   empty_snat_det_session);

  /* Add/del external address range to FIB */
  /* *INDENT-OFF* */
  pool_foreach (i, sm->interfaces,
  ({
    if (i->is_inside)
      continue;

    snat_add_del_addr_to_fib(out_addr, out_plen, i->sw_if_index, is_add);
    break;
  }));
  /* *INDENT-ON* */
  return 0;
}

/**
 * @brief The 'snat-det-expire-walk' process's main loop.
 *
 * Check expire time for active sessions.
 */
static uword
snat_det_expire_walk_fn (vlib_main_t * vm, vlib_node_runtime_t * rt,
			 vlib_frame_t * f)
{
  snat_main_t *sm = &snat_main;
  snat_det_map_t *dm;
  snat_det_session_t *ses;

  while (sm->deterministic)
    {
      vlib_process_wait_for_event_or_clock (vm, 10.0);
      vlib_process_get_events (vm, NULL);
      u32 now = (u32) vlib_time_now (vm);
      /* *INDENT-OFF* */
      pool_foreach (dm, sm->det_maps,
      ({
        vec_foreach(ses, dm->sessions)
          {
            /* Delete if session expired */
            if (ses->in_port && (ses->expire < now))
              snat_det_ses_close (dm, ses);
          }
      }));
      /* *INDENT-ON* */
    }

  return 0;
}

static vlib_node_registration_t snat_det_expire_walk_node;

/* *INDENT-OFF* */
VLIB_REGISTER_NODE (snat_det_expire_walk_node, static) = {
    .function = snat_det_expire_walk_fn,
    .type = VLIB_NODE_TYPE_PROCESS,
    .name =
    "snat-det-expire-walk",
};
/* *INDENT-ON* */

/*
 * fd.io coding-style-patch-verification: ON
 *
 * Local Variables:
 * eval: (c-set-style "gnu")
 * End:
 */