#include <stdlib.h>
#include <assert.h>

#include "timestamp.h"
#include "session_private.h"
#include "session_pool.h"
#include "session_table.h"
#include "session_timer.h"
#include "session_queue.h"
#include "session_manager.h"
#include "tcp_helpers.h"
#include "udp_helpers.h"
#include "packet_helpers.h"
#include "dupkt_filter.h"
#include "eviction_filter.h"
#include "id_generator.h"

struct session_manager
{
     struct session_pool *sess_pool;
     struct session_table *tcp_sess_table;
     struct session_table *udp_sess_table;
     struct session_timer *sess_timer;
     struct session_queue *sess_evicted_queue;
     struct session_queue *sess_toclosed_queue;

     struct dupkt_filter *tcp_dupkt_filter;
     struct eviction_filter *udp_eviction_filter;

     struct session_manager_config config;

     /***************************************************************
      * session manager status
      ***************************************************************/

     // session number
     uint64_t tcp_sess_num;
     uint64_t tcp_opening_sess_num;
     uint64_t tcp_active_sess_num;
     uint64_t tcp_closing_sess_num;

     uint64_t udp_sess_num;
     uint64_t udp_opening_sess_num;
     uint64_t udp_active_sess_num;
     uint64_t udp_closing_sess_num;

     uint64_t tcp_overload_evict_old_sess_num;
     uint64_t tcp_overload_evict_new_sess_num;
     uint64_t udp_overload_evict_old_sess_num;
     uint64_t udp_overload_evict_new_sess_num;

     // packet filter status
     uint64_t npkts_miss_l4_proto; // fast forward

     uint64_t npkts_hit_tcp_miss_sess; // fast forward
     uint64_t npkts_hit_tcp_dupkt;     // fast forward
     uint64_t npkts_hit_tcp_discard;   // drop

     uint64_t npkts_hit_udp_evicted; // fast forward
};

static inline void tcp_init_timeout_cb(struct session *sess, void *arg);
static inline void tcp_handshake_timeout_cb(struct session *sess, void *arg);
static inline void tcp_data_timeout_cb(struct session *sess, void *arg);
static inline void tcp_half_closed_timeout_cb(struct session *sess, void *arg);
static inline void tcp_time_wait_timeout_cb(struct session *sess, void *arg);
static inline void udp_data_timeout_cb(struct session *sess, void *arg);

static inline int session_manager_check_config(struct session_manager_config *config);
static inline uint64_t session_manager_alloc_session_id(void);
static inline int session_manager_update_tcp_filter(struct session_manager *mgr, struct session *sess, const struct packet *pkt, enum session_dir curr_dir);

static inline enum session_dir judge_direction_by_tuple6(const struct tuple6 *key);
static inline enum session_dir judge_direction_by_session(const struct session *sess, const struct tuple6 *key);

static inline void session_update_tcp_state(struct session *sess, const struct layer_record *tcp_layer, enum session_dir curr_dir);
static inline void session_update_udp_state(struct session *sess, const struct layer_record *udp_layer, enum session_dir curr_dir);

static inline void session_manager_update_session_state(struct session_manager *mgr, struct session *sess, enum session_state state);
static inline void session_manager_update_session_timer(struct session_manager *mgr, struct session *sess, session_expire_cb expire_cb, uint64_t timeout_sec);
static inline void session_manager_update_session_base(struct session_manager *mgr, struct session *sess, const struct tuple6 *key, enum session_dir curr_dir);
static inline void session_manager_update_session_packet(struct session_manager *mgr, struct session *sess, const struct packet *pkt, enum session_dir curr_dir);

static inline void session_manager_update_udp_to_opening(struct session_manager *mgr, struct session *sess);
static inline void session_manager_update_udp_to_active(struct session_manager *mgr, struct session *sess);
static inline void session_manager_update_udp_to_closing(struct session_manager *mgr, struct session *sess);
static inline void session_manager_update_tcp_to_opening(struct session_manager *mgr, struct session *sess, int opening_by_syn);
static inline void session_manager_update_tcp_to_active(struct session_manager *mgr, struct session *sess);
static inline void session_manager_update_tcp_to_closing(struct session_manager *mgr, struct session *sess, int enable_time_wait);
static inline void session_manager_update_session_to_closed(struct session_manager *mgr, struct session *sess);

static inline void session_manager_handle_tcp_on_opening(struct session_manager *mgr, struct session *sess, enum tcp_state tcp_old_state, enum tcp_state tcp_curr_state);
static inline void session_manager_handle_tcp_on_active(struct session_manager *mgr, struct session *sess, enum tcp_state tcp_old_state, enum tcp_state tcp_curr_state);
static inline void session_manager_handle_tcp_on_closing(struct session_manager *mgr, struct session *sess, enum tcp_state tcp_old_state, enum tcp_state tcp_curr_state);

static inline struct session *session_manager_new_tcp_session(struct session_manager *mgr, const struct packet *pkt, const struct tuple6 *key);
static inline struct session *session_manager_new_udp_session(struct session_manager *mgr, const struct packet *pkt, const struct tuple6 *key);
static inline struct session *session_manager_update_tcp_session(struct session_manager *mgr, struct session *sess, const struct packet *pkt, const struct tuple6 *key);
static inline struct session *session_manager_update_udp_session(struct session_manager *mgr, struct session *sess, const struct packet *pkt, const struct tuple6 *key);

static inline void session_manager_free_session(struct session_manager *mgr, struct session *sess);
static inline void session_manager_recycle_session(struct session_manager *mgr);
static inline void session_manager_evicte_session(struct session_manager *mgr, struct session *sess);

/******************************************************************************
 * Private API
 ******************************************************************************/

static inline void tcp_init_timeout_cb(struct session *sess, void *arg)
{
     SESSION_LOG_DEBUG("run tcp_init_timeout_cb on session %lu", session_get_id(sess));
     struct session_manager *mgr = (struct session_manager *)arg;
     assert(mgr != NULL);

     if (session_get_closing_reasion(sess) == 0)
     {
          session_set_closing_reasion(sess, CLOSING_BY_TIMEOUT);
     }
     session_manager_update_tcp_to_closing(mgr, sess, 1);
}

static inline void tcp_handshake_timeout_cb(struct session *sess, void *arg)
{
     SESSION_LOG_DEBUG("run tcp_handshake_timeout_cb on session %lu", session_get_id(sess));
     struct session_manager *mgr = (struct session_manager *)arg;
     assert(mgr != NULL);

     if (session_get_closing_reasion(sess) == 0)
     {
          session_set_closing_reasion(sess, CLOSING_BY_TIMEOUT);
     }
     session_manager_update_tcp_to_closing(mgr, sess, 1);
}

static inline void tcp_data_timeout_cb(struct session *sess, void *arg)
{
     SESSION_LOG_DEBUG("run tcp_data_timeout_cb on session %lu", session_get_id(sess));
     struct session_manager *mgr = (struct session_manager *)arg;
     assert(mgr != NULL);

     if (session_get_closing_reasion(sess) == 0)
     {
          session_set_closing_reasion(sess, CLOSING_BY_TIMEOUT);
     }
     session_manager_update_tcp_to_closing(mgr, sess, 1);
}

static inline void tcp_half_closed_timeout_cb(struct session *sess, void *arg)
{
     SESSION_LOG_DEBUG("run tcp_half_closed_timeout_cb on session %lu", session_get_id(sess));
     struct session_manager *mgr = (struct session_manager *)arg;
     assert(mgr != NULL);

     if (session_get_closing_reasion(sess) == 0)
     {
          session_set_closing_reasion(sess, CLOSING_BY_TIMEOUT);
     }
     session_manager_update_tcp_to_closing(mgr, sess, 1);
}

static inline void tcp_time_wait_timeout_cb(struct session *sess, void *arg)
{
     SESSION_LOG_DEBUG("run tcp_time_wait_timeout_cb on session %lu", session_get_id(sess));
     struct session_manager *mgr = (struct session_manager *)arg;
     assert(mgr != NULL);

     session_manager_free_session(mgr, sess);
}

static inline void udp_data_timeout_cb(struct session *sess, void *arg)
{
     SESSION_LOG_DEBUG("run udp_data_timeout_cb on session %lu", session_get_id(sess));
     struct session_manager *mgr = (struct session_manager *)arg;
     assert(mgr != NULL);

     if (session_get_closing_reasion(sess) == 0)
     {
          session_set_closing_reasion(sess, CLOSING_BY_TIMEOUT);
     }
     session_manager_update_udp_to_closing(mgr, sess);
}

// return  0: success
// return -1: invalid config
static inline int session_manager_check_config(struct session_manager_config *config)
{
     if (config == NULL)
     {
          SESSION_LOG_ERROR("invalid config");
          return -1;
     }

     // max session number
     if (config->max_tcp_session_num < 2)
     {
          SESSION_LOG_ERROR("invalid max tcp session number");
          return -1;
     }
     if (config->max_udp_session_num < 2)
     {
          SESSION_LOG_ERROR("invalid max udp session number");
          return -1;
     }

     // session overload
     if (config->tcp_overload_evict_old_sess != 0 && config->tcp_overload_evict_old_sess != 1)
     {
          SESSION_LOG_ERROR("invalid tcp overload evict old session, support range: 0-1");
          return -1;
     }

     if (config->udp_overload_evict_old_sess != 0 && config->udp_overload_evict_old_sess != 1)
     {
          SESSION_LOG_ERROR("invalid udp overload evict old session, support range: 0-1");
          return -1;
     }

     // TCP timeout config
     if (config->tcp_timeout_init < 1 || config->tcp_timeout_init > 60)
     {
          SESSION_LOG_ERROR("invalid tcp timeout init, support range: 1-60");
          return -1;
     }
     if (config->tcp_timeout_handshake < 1 || config->tcp_timeout_handshake > 60)
     {
          SESSION_LOG_ERROR("invalid tcp timeout handshake, support range: 1-60");
          return -1;
     }
     if (config->tcp_timeout_data < 1 || config->tcp_timeout_data > 15999999)
     {
          SESSION_LOG_ERROR("invalid tcp timeout data, support range: 1-15,999,999");
          return -1;
     }
     if (config->tcp_timeout_half_closed < 1 || config->tcp_timeout_half_closed > 604800)
     {
          SESSION_LOG_ERROR("invalid tcp timeout half closed, support range: 1-604,800");
          return -1;
     }
     if (config->tcp_timeout_time_wait < 1 || config->tcp_timeout_time_wait > 600)
     {
          SESSION_LOG_ERROR("invalid tcp timeout time wait, support range: 1-600");
          return -1;
     }
     if (config->tcp_timeout_discard < 1 || config->tcp_timeout_discard > 15999999)
     {
          SESSION_LOG_ERROR("invalid tcp timeout discard, support range: 1-15,999,999");
          return -1;
     }

     // UDP timeout config
     if (config->udp_timeout_data < 1 || config->udp_timeout_data > 15999999)
     {
          SESSION_LOG_ERROR("invalid udp timeout data, support range: 1-15,999,999");
          return -1;
     }

     // TCP duplicate packet filter config
     if (config->tcp_dupkt_filter_enable != 0 && config->tcp_dupkt_filter_enable != 1)
     {
          SESSION_LOG_ERROR("invalid tcp dupkt filter enable, support range: 0-1");
          return -1;
     }
     if (config->tcp_dupkt_filter_enable)
     {
          if (config->tcp_dupkt_filter_capacity == 0)
          {
               SESSION_LOG_ERROR("invalid tcp dupkt filter capacity");
               return -1;
          }
          if (config->tcp_dupkt_filter_timeout < 1 || config->tcp_dupkt_filter_timeout > 60)
          {
               SESSION_LOG_ERROR("invalid tcp dupkt filter timeout, support range: 1-60");
               return -1;
          }
          if (config->tcp_dupkt_filter_error_rate < 0 || config->tcp_dupkt_filter_error_rate > 1)
          {
               SESSION_LOG_ERROR("invalid tcp dupkt filter error rate, support range: 0-1");
               return -1;
          }
     }

     // UDP eviction filter config
     if (config->udp_eviction_filter_enable != 0 && config->udp_eviction_filter_enable != 1)
     {
          SESSION_LOG_ERROR("invalid udp eviction filter enable, support range: 0-1");
          return -1;
     }
     if (config->udp_eviction_filter_enable)
     {
          if (config->udp_eviction_filter_capacity == 0)
          {
               SESSION_LOG_ERROR("invalid udp eviction filter capacity");
               return -1;
          }
          if (config->udp_eviction_filter_timeout < 1 || config->udp_eviction_filter_timeout > 60)
          {
               SESSION_LOG_ERROR("invalid udp eviction filter timeout, support range: 1-60");
               return -1;
          }
          if (config->udp_eviction_filter_error_rate < 0 || config->udp_eviction_filter_error_rate > 1)
          {
               SESSION_LOG_ERROR("invalid udp eviction filter error rate, support range: 0-1");
               return -1;
          }
     }

     return 0;
}

static inline uint64_t session_manager_alloc_session_id(void)
{
     return id_generator_get();
}

// return 1: duplicate packet
// return 0: not duplicate packet
static inline int session_manager_update_tcp_filter(struct session_manager *mgr, struct session *sess, const struct packet *pkt, enum session_dir curr_dir)
{
     if (curr_dir == SESSION_DIR_C2S)
     {
          if (session_get_c2s_packets(sess) < 3)
          {
               goto dupkt_fitler;
          }
     }
     else if (curr_dir == SESSION_DIR_S2C)
     {
          if (session_get_s2c_packets(sess) < 3)
          {
               goto dupkt_fitler;
          }
     }

     if (session_get_dup_traffic_flag(sess) == DUP_TRAFFIC_YES)
     {
          goto dupkt_fitler;
     }
     else
     {
          return 0;
     }

dupkt_fitler:
     if (dupkt_filter_lookup(mgr->tcp_dupkt_filter, pkt))
     {
          return 1;
     }
     else
     {
          dupkt_filter_add(mgr->tcp_dupkt_filter, pkt);
          return 0;
     }
}

static inline enum session_dir judge_direction_by_tuple6(const struct tuple6 *key)
{
     uint16_t src_port = ntohs(key->src_port);
     uint16_t dst_port = ntohs(key->dst_port);

     // big port is client
     if (src_port > dst_port)
     {
          return SESSION_DIR_C2S;
     }

     else if (src_port < dst_port)
     {
          return SESSION_DIR_S2C;
     }
     else
     {
          // if port is equal, first packet is C2S
          return SESSION_DIR_C2S;
     }
}

static inline enum session_dir judge_direction_by_session(const struct session *sess, const struct tuple6 *key)
{
     if (tuple6_cmp(session_get0_key(sess), key) == 0)
     {
          return session_get_key_dir(sess);
     }
     else
     {
          return (session_get_key_dir(sess) == SESSION_DIR_C2S ? SESSION_DIR_S2C : SESSION_DIR_C2S);
     }
}

static inline void session_update_tcp_state(struct session *sess, const struct layer_record *tcp_layer, enum session_dir curr_dir)
{
     const struct tcphdr *hdr = (const struct tcphdr *)tcp_layer->hdr_ptr;
     uint64_t state = session_get_tcp_state(sess);
     if (tcp_hdr_has_flag_syn(hdr))
     {
          state |= (tcp_hdr_has_flag_ack(hdr) ? TCP_SYNACK_RECVED : TCP_SYN_RECVED);
     }
     else
     {
          if (tcp_hdr_has_flag_ack(hdr))
          {
               if (curr_dir == SESSION_DIR_C2S)
               {
                    state |= TCP_C2S_ACK_RECVED;
               }
               else if (curr_dir == SESSION_DIR_S2C)
               {
                    state |= TCP_S2C_ACK_RECVED;
               }
          }
     }
     if (tcp_hdr_has_flag_fin(hdr))
     {
          if (curr_dir == SESSION_DIR_C2S)
          {
               state |= TCP_C2S_FIN_RECVED;
          }
          else if (curr_dir == SESSION_DIR_S2C)
          {
               state |= TCP_S2C_FIN_RECVED;
          }
     }
     if (tcp_hdr_has_flag_rst(hdr))
     {
          if (curr_dir == SESSION_DIR_C2S)
          {
               state |= TCP_C2S_RST_RECVED;
          }
          else if (curr_dir == SESSION_DIR_S2C)
          {
               state |= TCP_S2C_RST_RECVED;
          }
     }
     if (tcp_layer->pld_len > 0)
     {
          if (curr_dir == SESSION_DIR_C2S)
          {
               state |= TCP_C2S_DATA_RECVED;
          }
          else if (curr_dir == SESSION_DIR_S2C)
          {
               state |= TCP_S2C_DATA_RECVED;
          }
     }

     session_set_tcp_state(sess, (enum tcp_state)state);
}

static inline void session_update_udp_state(struct session *sess, const struct layer_record *udp_layer, enum session_dir curr_dir)
{
     uint64_t state = session_get_udp_state(sess);
     if (curr_dir == SESSION_DIR_C2S)
     {
          state |= UDP_C2S_RECVED;
     }
     else if (curr_dir == SESSION_DIR_S2C)
     {
          state |= UDP_S2C_RECVED;
     }
     session_set_udp_state(sess, (enum udp_state)state);
}

/*
on opening update session
[*] session_init
[*] session_set_id
[*] session_set_key
[*] session_set_key_dir
[*] session_set_type
[*] session_set_create_time
[*] session_set_state

on packet update session
[*] session_inc_c2s_metrics
[*] session_inc_s2c_metrics
[*] session_set_c2s_1st_pkt
[*] session_set_s2c_1st_pkt
[*] session_set_c2s_1st_pkt_md
[*] session_set_s2c_1st_pkt_md
[*] session_set0_cur_pkt
[*] session_set_cur_dir
[*] session_set_last_time
    session_set_state
    session_set_dup_traffic_flag

on closing update session
[*] session_set_state
[*] session_set_closing_reasion
*/

static inline void session_manager_update_session_state(struct session_manager *mgr, struct session *sess, enum session_state state)
{
     // session state not change
     if (session_get_state(sess) == state)
     {
          return;
     }

     enum session_type type = session_get_type(sess);
     if (type == SESSION_TYPE_TCP)
     {
          // handle old state
          switch (session_get_state(sess))
          {
          case SESSION_STATE_OPENING:
               mgr->tcp_opening_sess_num--;
               break;
          case SESSION_STATE_ACTIVE:
               mgr->tcp_active_sess_num--;
               break;
          case SESSION_STATE_CLOSING:
               mgr->tcp_closing_sess_num--;
               break;
          case SESSION_STATE_CLOSED:
               /* void */
               break;
          default:
               break;
          }

          // handle new state
          switch (state)
          {
          case SESSION_STATE_OPENING:
               mgr->tcp_opening_sess_num++;
               mgr->tcp_sess_num++;
               break;
          case SESSION_STATE_ACTIVE:
               mgr->tcp_active_sess_num++;
               break;
          case SESSION_STATE_CLOSING:
               mgr->tcp_closing_sess_num++;
               break;
          case SESSION_STATE_CLOSED:
               mgr->tcp_sess_num--;
               break;
          default:
               break;
          }
     }
     else if (type == SESSION_TYPE_UDP)
     {
          // handle old state
          switch (session_get_state(sess))
          {
          case SESSION_STATE_OPENING:
               mgr->udp_opening_sess_num--;
               break;
          case SESSION_STATE_ACTIVE:
               mgr->udp_active_sess_num--;
               break;
          case SESSION_STATE_CLOSING:
               mgr->udp_closing_sess_num--;
               break;
          case SESSION_STATE_CLOSED:
               /* void */
               break;
          default:
               break;
          }

          // handle new state
          switch (state)
          {
          case SESSION_STATE_OPENING:
               mgr->udp_opening_sess_num++;
               mgr->udp_sess_num++;
               break;
          case SESSION_STATE_ACTIVE:
               mgr->udp_active_sess_num++;
               break;
          case SESSION_STATE_CLOSING:
               mgr->udp_closing_sess_num++;
               break;
          case SESSION_STATE_CLOSED:
               mgr->udp_sess_num--;
               break;
          default:
               break;
          }
     }

     session_set_state(sess, state);
}

static inline void session_manager_update_session_timer(struct session_manager *mgr, struct session *sess, session_expire_cb expire_cb, uint64_t timeout_sec)
{
     session_timer_del_session(mgr->sess_timer, sess);
     session_set_expirecb(sess, expire_cb, mgr, timestamp_get_sec() + timeout_sec);
     session_timer_add_session(mgr->sess_timer, sess);
}

static inline void session_manager_update_session_base(struct session_manager *mgr, struct session *sess, const struct tuple6 *key, enum session_dir curr_dir)
{
     session_init(sess);
     session_set_id(sess, session_manager_alloc_session_id());
     session_set_key(sess, key);
     session_set_key_dir(sess, curr_dir);
     if (key->ip_proto == IPPROTO_UDP)
     {
          session_set_type(sess, SESSION_TYPE_UDP);
     }
     else if (key->ip_proto == IPPROTO_TCP)
     {
          session_set_type(sess, SESSION_TYPE_TCP);
     }
     session_set_create_time(sess, timestamp_get_sec());
}

static inline void session_manager_update_session_packet(struct session_manager *mgr, struct session *sess, const struct packet *pkt, enum session_dir curr_dir)
{
     uint64_t len = packet_get_raw_len(pkt);
     if (curr_dir == SESSION_DIR_C2S)
     {
          session_inc_c2s_metrics(sess, 1, len);
          if (session_get0_c2s_1st_pkt(sess) == NULL)
          {
               session_set_c2s_1st_pkt(sess, pkt);
          }
     }
     else if (curr_dir == SESSION_DIR_S2C)
     {
          session_inc_s2c_metrics(sess, 1, len);
          if (session_get0_s2c_1st_pkt(sess) == NULL)
          {
               session_set_s2c_1st_pkt(sess, pkt);
          }
     }
     session_set0_cur_pkt(sess, pkt);
     session_set_cur_dir(sess, curr_dir);
     session_set_last_time(sess, timestamp_get_sec());
}

static inline void session_manager_update_udp_to_opening(struct session_manager *mgr, struct session *sess)
{
     session_manager_update_session_state(mgr, sess, SESSION_STATE_OPENING);
     session_manager_update_session_timer(mgr, sess, udp_data_timeout_cb, mgr->config.udp_timeout_data);
}

static inline void session_manager_update_udp_to_active(struct session_manager *mgr, struct session *sess)
{
     session_manager_update_session_state(mgr, sess, SESSION_STATE_ACTIVE);
     session_manager_update_session_timer(mgr, sess, udp_data_timeout_cb, mgr->config.udp_timeout_data);
}

static inline void session_manager_update_udp_to_closing(struct session_manager *mgr, struct session *sess)
{
     session_manager_update_session_state(mgr, sess, SESSION_STATE_CLOSING);
     session_timer_del_session(mgr->sess_timer, sess);
     session_queue_push(mgr->sess_toclosed_queue, sess);
     eviction_filter_add(mgr->udp_eviction_filter, session_get0_1st_pkt(sess));
}

static inline void session_manager_update_tcp_to_opening(struct session_manager *mgr, struct session *sess, int opening_by_syn)
{
     session_manager_update_session_state(mgr, sess, SESSION_STATE_OPENING);
     if (opening_by_syn)
     {
          session_manager_update_session_timer(mgr, sess, tcp_init_timeout_cb, mgr->config.tcp_timeout_init);
     }
     else
     {
          session_manager_update_session_timer(mgr, sess, tcp_handshake_timeout_cb, mgr->config.tcp_timeout_handshake);
     }
}

static inline void session_manager_update_tcp_to_active(struct session_manager *mgr, struct session *sess)
{
     session_manager_update_session_state(mgr, sess, SESSION_STATE_ACTIVE);
     session_manager_update_session_timer(mgr, sess, tcp_data_timeout_cb, mgr->config.tcp_timeout_data);
}

static inline void session_manager_update_tcp_to_closing(struct session_manager *mgr, struct session *sess, int enable_time_wait)
{
     session_manager_update_session_state(mgr, sess, SESSION_STATE_CLOSING);
     if (enable_time_wait)
     {
          session_manager_update_session_timer(mgr, sess, tcp_time_wait_timeout_cb, mgr->config.tcp_timeout_time_wait);
     }
     else
     {
          session_timer_del_session(mgr->sess_timer, sess);
     }
}

static inline void session_manager_update_session_to_closed(struct session_manager *mgr, struct session *sess)
{
     session_manager_update_session_state(mgr, sess, SESSION_STATE_CLOSED);
     session_timer_del_session(mgr->sess_timer, sess);
}

// opening -> opening
// opening -> active
// opening -> closing
static inline void session_manager_handle_tcp_on_opening(struct session_manager *mgr, struct session *sess, enum tcp_state tcp_old_state, enum tcp_state tcp_curr_state)
{
     uint64_t tcp_mod_state = tcp_curr_state & (~tcp_old_state);

     // opening -> closing
     if ((tcp_curr_state & TCP_C2S_FIN_RECVED) && (tcp_curr_state & TCP_S2C_FIN_RECVED))
     {
          SESSION_LOG_DEBUG("TCP FIN-FIN received, session %lu opening -> closing", session_get_id(sess));
          session_manager_update_tcp_to_closing(mgr, sess, 1);
          return;
     }
     if (tcp_mod_state & (TCP_C2S_RST_RECVED | TCP_S2C_RST_RECVED))
     {
          SESSION_LOG_DEBUG("TCP %s RST received, session %lu opening -> closing", (tcp_curr_state & TCP_C2S_RST_RECVED ? "C2S" : "S2C"), session_get_id(sess));
          session_set_closing_reasion(sess, (tcp_mod_state & TCP_C2S_RST_RECVED) ? CLOSING_BY_CLIENT_RST : CLOSING_BY_SERVER_RST);
          session_manager_update_tcp_to_closing(mgr, sess, 1);
          return;
     }

     // opening -> active
     if (tcp_mod_state & (TCP_C2S_DATA_RECVED | TCP_S2C_DATA_RECVED))
     {
          SESSION_LOG_DEBUG("TCP %s DATA received, session %lu opening -> active", (tcp_curr_state & TCP_C2S_DATA_RECVED ? "C2S" : "S2C"), session_get_id(sess));
          session_manager_update_tcp_to_active(mgr, sess);
          return;
     }

     // opening -> opening
     if (tcp_mod_state & (TCP_C2S_FIN_RECVED | TCP_S2C_FIN_RECVED))
     {
          SESSION_LOG_DEBUG("TCP %s FIN received, session %lu opening -> opening", (tcp_curr_state & TCP_C2S_FIN_RECVED ? "C2S" : "S2C"), session_get_id(sess));
          // still opening, only update timeout
          session_set_closing_reasion(sess, (tcp_mod_state & TCP_C2S_FIN_RECVED) ? CLOSING_BY_CLIENT_FIN : CLOSING_BY_SERVER_FIN);
          session_manager_update_session_timer(mgr, sess, tcp_half_closed_timeout_cb, mgr->config.tcp_timeout_half_closed);
          return;
     }

     if (tcp_mod_state & (TCP_C2S_ACK_RECVED | TCP_S2C_ACK_RECVED))
     {
          SESSION_LOG_DEBUG("TCP %s ACK received, session %lu opening -> opening", (tcp_curr_state & TCP_C2S_ACK_RECVED ? "C2S" : "S2C"), session_get_id(sess));
          // still opening, only update timeout
          session_manager_update_session_timer(mgr, sess, tcp_data_timeout_cb, mgr->config.tcp_timeout_data);
          return;
     }

     if (tcp_mod_state & TCP_SYNACK_RECVED)
     {
          SESSION_LOG_DEBUG("TCP SYNACK received, session %lu opening -> opening", session_get_id(sess));
          session_manager_update_tcp_to_opening(mgr, sess, 0);
     }

     if (tcp_mod_state == 0)
     {
          if (tcp_curr_state & TCP_SYN_RECVED)
          {
               SESSION_LOG_DEBUG("TCP SYN retransmission received, session %lu opening -> opening", session_get_id(sess));
               session_manager_update_tcp_to_opening(mgr, sess, 1);
          }

          if (tcp_curr_state & TCP_SYNACK_RECVED)
          {
               SESSION_LOG_DEBUG("TCP SYNACK retransmission received, session %lu opening -> opening", session_get_id(sess));
               session_manager_update_tcp_to_opening(mgr, sess, 0);
          }
     }
}

// active -> active
// active -> closing
static inline void session_manager_handle_tcp_on_active(struct session_manager *mgr, struct session *sess, enum tcp_state tcp_old_state, enum tcp_state tcp_curr_state)
{
     // active -> closing
     if ((tcp_curr_state & TCP_C2S_FIN_RECVED) && (tcp_curr_state & TCP_S2C_FIN_RECVED))
     {
          SESSION_LOG_DEBUG("TCP FIN-FIN received, session %lu active -> closing", session_get_id(sess));
          session_manager_update_tcp_to_closing(mgr, sess, 1);
          return;
     }
     if (tcp_curr_state & (TCP_C2S_RST_RECVED | TCP_S2C_RST_RECVED))
     {
          SESSION_LOG_DEBUG("TCP %s RST received, session %lu active -> closing", (tcp_curr_state & TCP_C2S_RST_RECVED) ? "C2S" : "S2C", session_get_id(sess));
          session_set_closing_reasion(sess, (tcp_curr_state & TCP_C2S_RST_RECVED) ? CLOSING_BY_CLIENT_RST : CLOSING_BY_SERVER_RST);
          session_manager_update_tcp_to_closing(mgr, sess, 1);
          return;
     }

     // active -> active
     if (tcp_curr_state & (TCP_C2S_FIN_RECVED | TCP_S2C_FIN_RECVED))
     {
          SESSION_LOG_DEBUG("TCP %s FIN received, session %lu active -> active", (tcp_curr_state & TCP_C2S_FIN_RECVED) ? "C2S" : "S2C", session_get_id(sess));
          // still active
          session_set_closing_reasion(sess, (tcp_curr_state & TCP_C2S_FIN_RECVED) ? CLOSING_BY_CLIENT_FIN : CLOSING_BY_SERVER_FIN);
          session_manager_update_session_timer(mgr, sess, tcp_half_closed_timeout_cb, mgr->config.tcp_timeout_half_closed);
          return;
     }

     // still active
     session_manager_update_tcp_to_active(mgr, sess);
}

// closing -> closing
// closing -> closed
static inline void session_manager_handle_tcp_on_closing(struct session_manager *mgr, struct session *sess, enum tcp_state tcp_old_state, enum tcp_state tcp_curr_state)
{
     // still closing
     session_manager_update_tcp_to_closing(mgr, sess, 1);
}

static inline struct session *session_manager_new_tcp_session(struct session_manager *mgr, const struct packet *pkt, const struct tuple6 *key)
{
     const struct layer_record *tcp_layer = packet_get_innermost_layer(pkt, LAYER_TYPE_TCP);
     if (tcp_layer == NULL)
     {
          mgr->npkts_miss_l4_proto++;
          return NULL;
     }

     const struct tcphdr *hdr = (const struct tcphdr *)tcp_layer->hdr_ptr;
     if (!tcp_hdr_has_flag_syn(hdr))
     {
          mgr->npkts_hit_tcp_miss_sess++;
          return NULL;
     }

     if (mgr->tcp_sess_num >= mgr->config.max_tcp_session_num - 1)
     {
          if (mgr->config.tcp_overload_evict_old_sess)
          {
               struct session *evicted_sess = session_table_find_least_recently_unused_session(mgr->tcp_sess_table);
               assert(evicted_sess);
               session_manager_evicte_session(mgr, evicted_sess);
               mgr->tcp_overload_evict_old_sess_num++;
          }
          else
          {
               if (mgr->tcp_sess_num >= mgr->config.max_tcp_session_num)
               {
                    mgr->tcp_overload_evict_new_sess_num++;
                    return NULL;
               }
               else
               {
                    // continue;
               }
          }
     }

     struct session *sess = session_pool_alloc(mgr->sess_pool);
     assert(sess);

     enum session_dir curr_dir = tcp_hdr_has_flag_ack(hdr) ? SESSION_DIR_S2C : SESSION_DIR_C2S;
     session_manager_update_session_base(mgr, sess, key, curr_dir);
     session_manager_update_session_packet(mgr, sess, pkt, curr_dir);
     session_update_tcp_state(sess, tcp_layer, curr_dir);

     char buffer[128] = {0};
     tuple6_tostring(session_get0_key(sess), buffer, sizeof(buffer));
     SESSION_LOG_DEBUG("session new: %lu %s", session_get_id(sess), buffer);
     SESSION_LOG_DEBUG("TCP %s received, session %lu init -> opening", (curr_dir == SESSION_DIR_C2S ? "SYN" : "SYNACK"), session_get_id(sess));

     session_manager_update_tcp_to_opening(mgr, sess, curr_dir == SESSION_DIR_C2S);
     session_table_add_session(mgr->tcp_sess_table, key, sess);
     dupkt_filter_add(mgr->tcp_dupkt_filter, pkt);

     return sess;
}

static inline struct session *session_manager_new_udp_session(struct session_manager *mgr, const struct packet *pkt, const struct tuple6 *key)
{
     if (eviction_filter_lookup(mgr->udp_eviction_filter, pkt))
     {
          mgr->npkts_hit_udp_evicted++;
          return NULL;
     }

     if (mgr->udp_sess_num >= mgr->config.max_udp_session_num - 1)
     {
          if (mgr->config.udp_overload_evict_old_sess)
          {
               struct session *evicted_sess = session_table_find_least_recently_unused_session(mgr->udp_sess_table);
               assert(evicted_sess);
               session_manager_evicte_session(mgr, evicted_sess);
               mgr->udp_overload_evict_old_sess_num++;
          }
          else
          {
               if (mgr->udp_sess_num >= mgr->config.max_udp_session_num)
               {
                    mgr->udp_overload_evict_new_sess_num++;
                    return NULL;
               }
               else
               {
                    // continue;
               }
          }
     }

     struct session *sess = session_pool_alloc(mgr->sess_pool);
     assert(sess);

     enum session_dir curr_dir = judge_direction_by_tuple6(key);
     session_manager_update_session_base(mgr, sess, key, curr_dir);
     session_manager_update_session_packet(mgr, sess, pkt, curr_dir);
     session_update_udp_state(sess, NULL, curr_dir);
     session_manager_update_udp_to_opening(mgr, sess);
     session_table_add_session(mgr->udp_sess_table, key, sess);

     char buffer[128] = {0};
     tuple6_tostring(session_get0_key(sess), buffer, sizeof(buffer));
     SESSION_LOG_DEBUG("session new: %lu %s", session_get_id(sess), buffer);
     SESSION_LOG_DEBUG("UDP %s first packet received, session %lu init -> opening", (curr_dir == SESSION_DIR_C2S ? "C2S" : "S2C"), session_get_id(sess));

     return sess;
}

static inline struct session *session_manager_update_tcp_session(struct session_manager *mgr, struct session *sess, const struct packet *pkt, const struct tuple6 *key)
{
     const struct layer_record *tcp_layer = packet_get_innermost_layer(pkt, LAYER_TYPE_TCP);
     if (tcp_layer == NULL)
     {
          mgr->npkts_miss_l4_proto++;
          return NULL;
     }

     enum session_dir curr_dir = judge_direction_by_session(sess, key);
     if (session_manager_update_tcp_filter(mgr, sess, pkt, curr_dir))
     {
          mgr->npkts_hit_tcp_dupkt++;
          session_set_dup_traffic_flag(sess, DUP_TRAFFIC_YES);
          return NULL;
     }

     enum session_state sess_state = session_get_state(sess);
     enum tcp_state tcp_old_state = session_get_tcp_state(sess);
     session_manager_update_session_packet(mgr, sess, pkt, curr_dir);
     session_update_tcp_state(sess, tcp_layer, curr_dir);
     enum tcp_state tcp_curr_state = session_get_tcp_state(sess);

     switch (sess_state)
     {
     case SESSION_STATE_OPENING:
          session_manager_handle_tcp_on_opening(mgr, sess, tcp_old_state, tcp_curr_state);
          break;
     case SESSION_STATE_ACTIVE:
          session_manager_handle_tcp_on_active(mgr, sess, tcp_old_state, tcp_curr_state);
          break;
     case SESSION_STATE_CLOSING:
          session_manager_handle_tcp_on_closing(mgr, sess, tcp_old_state, tcp_curr_state);
          break;
     case SESSION_STATE_CLOSED:
          assert(0);
          break;
     default:
          break;
     }

     return sess;
}

static inline struct session *session_manager_update_udp_session(struct session_manager *mgr, struct session *sess, const struct packet *pkt, const struct tuple6 *key)
{
     enum session_dir curr_dir = judge_direction_by_session(sess, key);
     session_manager_update_session_packet(mgr, sess, pkt, curr_dir);
     session_update_udp_state(sess, NULL, curr_dir);
     enum session_state sess_state = session_get_state(sess);

     switch (sess_state)
     {
     case SESSION_STATE_OPENING:
          session_manager_update_udp_to_active(mgr, sess);
          break;
     case SESSION_STATE_ACTIVE:
          session_manager_update_udp_to_active(mgr, sess);
          return sess;
     case SESSION_STATE_CLOSING:
          assert(0);
          break;
     case SESSION_STATE_CLOSED:
          assert(0);
          break;
     }

     return sess;
}

static inline void session_manager_free_session(struct session_manager *mgr, struct session *sess)
{
     if (sess)
     {
          SESSION_LOG_DEBUG("%s, session %lu closing -> closed", session_closing_reasion_tostring(session_get_closing_reasion(sess)), session_get_id(sess));
          session_manager_update_session_to_closed(mgr, sess);
          if (session_get_type(sess) == SESSION_TYPE_TCP)
          {
               session_table_del_session(mgr->tcp_sess_table, session_get0_key(sess));
          }
          if (session_get_type(sess) == SESSION_TYPE_UDP)
          {
               session_table_del_session(mgr->udp_sess_table, session_get0_key(sess));
          }
          session_set0_cur_pkt(sess, NULL);
          session_set_cur_dir(sess, SESSION_DIR_NONE);
          session_free(sess);
          session_pool_free(mgr->sess_pool, sess);
          sess = NULL;
     }
}

static inline void session_manager_recycle_session(struct session_manager *mgr)
{
     while (1)
     {
          struct session *sess = session_queue_pop(mgr->sess_toclosed_queue);
          if (sess == NULL)
          {
               break;
          }
          session_manager_free_session(mgr, sess);
     }
}

static inline void session_manager_evicte_session(struct session_manager *mgr, struct session *sess)
{
     session_set_closing_reasion(sess, CLOSING_BY_EVICTED);
     session_manager_update_session_state(mgr, sess, SESSION_STATE_CLOSING);
     session_queue_push(mgr->sess_evicted_queue, sess);
     session_timer_del_session(mgr->sess_timer, sess);

     if (session_get_type(sess) == SESSION_TYPE_UDP)
     {
          eviction_filter_add(mgr->udp_eviction_filter, session_get0_1st_pkt(sess));
     }
}

/******************************************************************************
 * Public API
 ******************************************************************************/

struct session_manager *session_manager_create(struct session_manager_config *config)
{
     if (session_manager_check_config(config))
     {
          return NULL;
     }

     struct session_manager *mgr = (struct session_manager *)calloc(1, sizeof(struct session_manager));
     if (mgr == NULL)
     {
          return NULL;
     }

     memcpy(&mgr->config, config, sizeof(struct session_manager_config));
     mgr->sess_pool = session_pool_create(mgr->config.max_tcp_session_num + mgr->config.max_udp_session_num);
     if (mgr->sess_pool == NULL)
     {
          goto error;
     }

     mgr->tcp_sess_table = session_table_create();
     if (mgr->tcp_sess_table == NULL)
     {
          goto error;
     }

     mgr->udp_sess_table = session_table_create();
     if (mgr->udp_sess_table == NULL)
     {
          goto error;
     }

     mgr->sess_timer = session_timer_create();
     if (mgr->sess_timer == NULL)
     {
          goto error;
     }

     mgr->sess_evicted_queue = session_queue_create();
     if (mgr->sess_evicted_queue == NULL)
     {
          goto error;
     }

     mgr->sess_toclosed_queue = session_queue_create();
     if (mgr->sess_toclosed_queue == NULL)
     {
          goto error;
     }

     mgr->tcp_dupkt_filter = dupkt_filter_create(mgr->config.tcp_dupkt_filter_enable, mgr->config.tcp_dupkt_filter_capacity, mgr->config.tcp_dupkt_filter_error_rate, mgr->config.tcp_dupkt_filter_timeout);
     if (mgr->tcp_dupkt_filter == NULL)
     {
          goto error;
     }

     mgr->udp_eviction_filter = eviction_filter_create(mgr->config.udp_eviction_filter_enable, mgr->config.udp_eviction_filter_capacity, mgr->config.udp_eviction_filter_error_rate, mgr->config.udp_eviction_filter_timeout);
     if (mgr->udp_eviction_filter == NULL)
     {
          goto error;
     }

     return mgr;

error:
     session_manager_destroy(mgr);
     return NULL;
}

void session_manager_destroy(struct session_manager *mgr)
{
     struct session *sess;
     if (mgr)
     {
          // move all evicted session to closed queue
          while (mgr->sess_evicted_queue && session_manager_get_evicted_session(mgr))
          {
          }

          // free all closed queue
          if (mgr->sess_toclosed_queue)
          {
               session_manager_recycle_session(mgr);
          }

          // free all udp session which is not in closed state
          while (mgr->udp_sess_table && (sess = session_table_find_least_recently_unused_session(mgr->udp_sess_table)))
          {
               session_manager_free_session(mgr, sess);
          }

          // free all tcp session which is not in closed state
          while (mgr->tcp_sess_table && (sess = session_table_find_least_recently_unused_session(mgr->tcp_sess_table)))
          {
               session_manager_free_session(mgr, sess);
          }

          eviction_filter_destroy(mgr->udp_eviction_filter);
          dupkt_filter_destroy(mgr->tcp_dupkt_filter);
          session_queue_destroy(mgr->sess_toclosed_queue);
          session_queue_destroy(mgr->sess_evicted_queue);
          session_timer_destroy(mgr->sess_timer);
          session_table_destroy(mgr->udp_sess_table);
          session_table_destroy(mgr->tcp_sess_table);
          session_pool_destroy(mgr->sess_pool);
          free(mgr);
          mgr = NULL;
     }
}

// only use the packet six-tuple to find the session, not update it
struct session *session_manager_lookup_sesssion(struct session_manager *mgr, const struct packet *pkt)
{
     struct tuple6 key;
     memset(&key, 0, sizeof(struct tuple6));
     if (packet_get_innermost_tuple6(pkt, &key))
     {
          return NULL;
     }

     if (key.ip_proto == IPPROTO_UDP)
     {
          return session_table_find_session(mgr->udp_sess_table, &key);
     }
     else if (key.ip_proto == IPPROTO_TCP)
     {
          return session_table_find_session(mgr->tcp_sess_table, &key);
     }
     else
     {
          return NULL;
     }
}

/*
 * Return NULL in the following cases:
 *      1.not a TCP or UDP packet
 *      2.TCP packet miss session but no syn packet seen
 *      3.TCP duplicate packet
 *      4.TCP discards packets
 *      5.UDP evict packet
 * pakcet will not update the session and needs to be fast forwarded
 */
struct session *session_manager_update_session(struct session_manager *mgr, const struct packet *pkt)
{
     assert(session_manager_get_evicted_session(mgr) == NULL);

     session_manager_recycle_session(mgr);

     struct tuple6 key;
     memset(&key, 0, sizeof(struct tuple6));
     if (packet_get_innermost_tuple6(pkt, &key))
     {
          mgr->npkts_miss_l4_proto++;
          return NULL;
     }

     struct session *sess = NULL;
     if (key.ip_proto == IPPROTO_UDP)
     {
          sess = session_table_find_session(mgr->udp_sess_table, &key);
          if (sess)
          {
               return session_manager_update_udp_session(mgr, sess, pkt, &key);
          }
          else
          {
               return session_manager_new_udp_session(mgr, pkt, &key);
          }
     }
     else if (key.ip_proto == IPPROTO_TCP)
     {
          sess = session_table_find_session(mgr->tcp_sess_table, &key);
          if (sess)
          {
               return session_manager_update_tcp_session(mgr, sess, pkt, &key);
          }
          else
          {
               return session_manager_new_tcp_session(mgr, pkt, &key);
          }
     }
     else
     {
          return NULL;
     }
}

struct session *session_manager_get_expired_session(struct session_manager *mgr)
{
     session_manager_recycle_session(mgr);

     struct session *sess = session_timer_expire_session(mgr->sess_timer, timestamp_get_sec());
     if (sess)
     {
          session_run_expirecb(sess);

          if (session_get_state(sess) == SESSION_STATE_CLOSED)
          {
               return NULL;
          }

          if (session_get_type(sess) == SESSION_TYPE_UDP)
          {
               session_queue_push(mgr->sess_toclosed_queue, sess);
          }
     }

     return sess;
}

struct session *session_manager_get_evicted_session(struct session_manager *mgr)
{
     session_manager_recycle_session(mgr);

     struct session *sess = session_queue_pop(mgr->sess_evicted_queue);
     if (sess)
     {
          session_queue_push(mgr->sess_toclosed_queue, sess);
     }

     return sess;
}

uint64_t session_manager_get_expire_interval(struct session_manager *mgr)
{
     return session_timer_next_expire_interval(mgr->sess_timer);
}

void session_manager_get_session_counter(struct session_manager *mgr, struct session_counter *out)
{
     out->tcp_sess_num = mgr->tcp_sess_num;
     out->tcp_opening_sess_num = mgr->tcp_opening_sess_num;
     out->tcp_active_sess_num = mgr->tcp_active_sess_num;
     out->tcp_closing_sess_num = mgr->tcp_closing_sess_num;

     out->udp_sess_num = mgr->udp_sess_num;
     out->udp_opening_sess_num = mgr->udp_opening_sess_num;
     out->udp_active_sess_num = mgr->udp_active_sess_num;
     out->udp_closing_sess_num = mgr->udp_closing_sess_num;

     out->tcp_overload_evict_old_sess_num = mgr->tcp_overload_evict_old_sess_num;
     out->tcp_overload_evict_new_sess_num = mgr->tcp_overload_evict_new_sess_num;
     out->udp_overload_evict_old_sess_num = mgr->udp_overload_evict_old_sess_num;
     out->udp_overload_evict_new_sess_num = mgr->udp_overload_evict_new_sess_num;
}

void session_manager_print_status(struct session_manager *mgr)
{
     printf("session manager status:\n");

     printf("tcp session number    : %lu\n", mgr->tcp_sess_num);
     printf("    opening number    : %lu\n", mgr->tcp_opening_sess_num);
     printf("    active number     : %lu\n", mgr->tcp_active_sess_num);
     printf("    closing number    : %lu\n", mgr->tcp_closing_sess_num);
     printf("udp session number    : %lu\n", mgr->udp_sess_num);
     printf("    opening number    : %lu\n", mgr->udp_opening_sess_num);
     printf("    active number     : %lu\n", mgr->udp_active_sess_num);
     printf("    closing number    : %lu\n", mgr->udp_closing_sess_num);
     printf("tcp overload evict    : \n");
     printf("    old session number: %lu\n", mgr->tcp_overload_evict_old_sess_num);
     printf("    new session number: %lu\n", mgr->tcp_overload_evict_new_sess_num);
     printf("udp overload evict    : \n");
     printf("    old session number: %lu\n", mgr->udp_overload_evict_old_sess_num);
     printf("    new session number: %lu\n", mgr->udp_overload_evict_new_sess_num);

     printf("packet status:\n");
     printf("    miss l4 proto     : %lu  (bypass)\n", mgr->npkts_miss_l4_proto);

     printf("    hit tcp miss sess : %lu  (bypass)\n", mgr->npkts_hit_tcp_miss_sess);
     printf("    hit tcp dupkt     : %lu  (bypass)\n", mgr->npkts_hit_tcp_dupkt);
     printf("    hit tcp discard   : %lu  (drop)\n", mgr->npkts_hit_tcp_discard);

     printf("    hit udp evicted   : %lu  (bypass)\n", mgr->npkts_hit_udp_evicted);
}