text: #ifndef _NF_CONNTRACK_COMMON_H
  #define _NF_CONNTRACK_COMMON_H
  /* Connection state tracking for netfilter.  This is separated from,
     but required by, the NAT layer; it can also be used by an iptables
     extension. */
  enum ip_conntrack_info
  {
  	/* Part of an established connection (either direction). */
  	IP_CT_ESTABLISHED,
  
  	/* Like NEW, but related to an existing connection, or ICMP error
  	   (in either direction). */
  	IP_CT_RELATED,
  
  	/* Started a new connection to track (only
             IP_CT_DIR_ORIGINAL); may be a retransmission. */
  	IP_CT_NEW,
  
  	/* >= this indicates reply direction */
  	IP_CT_IS_REPLY,
  
  	/* Number of distinct IP_CT types (no NEW in reply dirn). */
  	IP_CT_NUMBER = IP_CT_IS_REPLY * 2 - 1
  };
  
  /* Bitset representing status of connection. */
  enum ip_conntrack_status {
  	/* It's an expected connection: bit 0 set.  This bit never changed */
  	IPS_EXPECTED_BIT = 0,
  	IPS_EXPECTED = (1 << IPS_EXPECTED_BIT),
  
  	/* We've seen packets both ways: bit 1 set.  Can be set, not unset. */
  	IPS_SEEN_REPLY_BIT = 1,
  	IPS_SEEN_REPLY = (1 << IPS_SEEN_REPLY_BIT),
  
  	/* Conntrack should never be early-expired. */
  	IPS_ASSURED_BIT = 2,
  	IPS_ASSURED = (1 << IPS_ASSURED_BIT),
  
  	/* Connection is confirmed: originating packet has left box */
  	IPS_CONFIRMED_BIT = 3,
  	IPS_CONFIRMED = (1 << IPS_CONFIRMED_BIT),
  
  	/* Connection needs src nat in orig dir.  This bit never changed. */
  	IPS_SRC_NAT_BIT = 4,
  	IPS_SRC_NAT = (1 << IPS_SRC_NAT_BIT),
  
  	/* Connection needs dst nat in orig dir.  This bit never changed. */
  	IPS_DST_NAT_BIT = 5,
  	IPS_DST_NAT = (1 << IPS_DST_NAT_BIT),
  
  	/* Both together. */
  	IPS_NAT_MASK = (IPS_DST_NAT | IPS_SRC_NAT),
  
  	/* Connection needs TCP sequence adjusted. */
  	IPS_SEQ_ADJUST_BIT = 6,
  	IPS_SEQ_ADJUST = (1 << IPS_SEQ_ADJUST_BIT),
  
  	/* NAT initialization bits. */
  	IPS_SRC_NAT_DONE_BIT = 7,
  	IPS_SRC_NAT_DONE = (1 << IPS_SRC_NAT_DONE_BIT),
  
  	IPS_DST_NAT_DONE_BIT = 8,
  	IPS_DST_NAT_DONE = (1 << IPS_DST_NAT_DONE_BIT),
  
  	/* Both together */
  	IPS_NAT_DONE_MASK = (IPS_DST_NAT_DONE | IPS_SRC_NAT_DONE),
  
  	/* Connection is dying (removed from lists), can not be unset. */
  	IPS_DYING_BIT = 9,
  	IPS_DYING = (1 << IPS_DYING_BIT),
  
  	/* Connection has fixed timeout. */
  	IPS_FIXED_TIMEOUT_BIT = 10,
  	IPS_FIXED_TIMEOUT = (1 << IPS_FIXED_TIMEOUT_BIT),
  };
  
  #ifdef __KERNEL__
  struct ip_conntrack_stat
  {
  	unsigned int searched;
  	unsigned int found;
  	unsigned int new;
  	unsigned int invalid;
  	unsigned int ignore;
  	unsigned int delete;
  	unsigned int delete_list;
  	unsigned int insert;
  	unsigned int insert_failed;
  	unsigned int drop;
  	unsigned int early_drop;
  	unsigned int error;
  	unsigned int expect_new;
  	unsigned int expect_create;
  	unsigned int expect_delete;
  };
  
  /* call to create an explicit dependency on nf_conntrack. */
  extern void need_conntrack(void);
  
  #endif /* __KERNEL__ */
  
  #endif /* _NF_CONNTRACK_COMMON_H */
  