text: #ifndef _IP_CONNTRACK_H
  #define _IP_CONNTRACK_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. */
  
  #include <linux/config.h>
  #include <linux/netfilter_ipv4/ip_conntrack_tuple.h>
  #include <linux/bitops.h>
  #include <linux/compiler.h>
  #include <asm/atomic.h>
  
  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),
  };
  
  #include <linux/netfilter_ipv4/ip_conntrack_tcp.h>
  #include <linux/netfilter_ipv4/ip_conntrack_icmp.h>
  
  /* per conntrack: protocol private data */
  union ip_conntrack_proto {
  	/* insert conntrack proto private data here */
  	struct ip_ct_tcp tcp;
  	struct ip_ct_icmp icmp;
  };
  
  union ip_conntrack_expect_proto {
  	/* insert expect proto private data here */
  };
  
  /* Add protocol helper include file here */
  #include <linux/netfilter_ipv4/ip_conntrack_amanda.h>
  #include <linux/netfilter_ipv4/ip_conntrack_ftp.h>
  #include <linux/netfilter_ipv4/ip_conntrack_irc.h>
  
  /* per expectation: application helper private data */
  union ip_conntrack_expect_help {
  	/* insert conntrack helper private data (expect) here */
  	struct ip_ct_amanda_expect exp_amanda_info;
  	struct ip_ct_ftp_expect exp_ftp_info;
  	struct ip_ct_irc_expect exp_irc_info;
  
  #ifdef CONFIG_IP_NF_NAT_NEEDED
  	union {
  		/* insert nat helper private data (expect) here */
  	} nat;
  #endif
  };
  
  /* per conntrack: application helper private data */
  union ip_conntrack_help {
  	/* insert conntrack helper private data (master) here */
  	struct ip_ct_ftp_master ct_ftp_info;
  	struct ip_ct_irc_master ct_irc_info;
  };
  
  #ifdef CONFIG_IP_NF_NAT_NEEDED
  #include <linux/netfilter_ipv4/ip_nat.h>
  
  /* per conntrack: nat application helper private data */
  union ip_conntrack_nat_help {
  	/* insert nat helper private data here */
  };
  #endif
  
  #ifdef __KERNEL__
  
  #include <linux/types.h>
  #include <linux/skbuff.h>
  
  #ifdef CONFIG_NF_DEBUG
  #define IP_NF_ASSERT(x)							\
  do {									\
  	if (!(x))							\
  		/* Wooah!  I'm tripping my conntrack in a frenzy of	\
  		   netplay... */					\
  		printk("NF_IP_ASSERT: %s:%i(%s)\n",			\
  		       __FILE__, __LINE__, __FUNCTION__);		\
  } while(0)
  #else
  #define IP_NF_ASSERT(x)
  #endif
  
  struct ip_conntrack_expect
  {
  	/* Internal linked list (global expectation list) */
  	struct list_head list;
  
  	/* reference count */
  	atomic_t use;
  
  	/* expectation list for this master */
  	struct list_head expected_list;
  
  	/* The conntrack of the master connection */
  	struct ip_conntrack *expectant;
  
  	/* The conntrack of the sibling connection, set after
  	 * expectation arrived */
  	struct ip_conntrack *sibling;
  
  	/* Tuple saved for conntrack */
  	struct ip_conntrack_tuple ct_tuple;
  
  	/* Timer function; deletes the expectation. */
  	struct timer_list timeout;
  
  	/* Data filled out by the conntrack helpers follow: */
  
  	/* We expect this tuple, with the following mask */
  	struct ip_conntrack_tuple tuple, mask;
  
  	/* Function to call after setup and insertion */
  	int (*expectfn)(struct ip_conntrack *new);
  
  	/* At which sequence number did this expectation occur */
  	u_int32_t seq;
    
  	union ip_conntrack_expect_proto proto;
  
  	union ip_conntrack_expect_help help;
  };
  
  #include <linux/netfilter_ipv4/ip_conntrack_helper.h>
  struct ip_conntrack
  {
  	/* Usage count in here is 1 for hash table/destruct timer, 1 per skb,
             plus 1 for any connection(s) we are `master' for */
  	struct nf_conntrack ct_general;
  
  	/* These are my tuples; original and reply */
  	struct ip_conntrack_tuple_hash tuplehash[IP_CT_DIR_MAX];
  
  	/* Have we seen traffic both ways yet? (bitset) */
  	unsigned long status;
  
  	/* Timer function; drops refcnt when it goes off. */
  	struct timer_list timeout;
  
  	/* If we're expecting another related connection, this will be
             in expected linked list */
  	struct list_head sibling_list;
  	
  	/* Current number of expected connections */
  	unsigned int expecting;
  
  	/* If we were expected by an expectation, this will be it */
  	struct ip_conntrack_expect *master;
  
  	/* Helper, if any. */
  	struct ip_conntrack_helper *helper;
  
  	/* Our various nf_ct_info structs specify *what* relation this
             packet has to the conntrack */
  	struct nf_ct_info infos[IP_CT_NUMBER];
  
  	/* Storage reserved for other modules: */
  
  	union ip_conntrack_proto proto;
  
  	union ip_conntrack_help help;
  
  #ifdef CONFIG_IP_NF_NAT_NEEDED
  	struct {
  		struct ip_nat_info info;
  		union ip_conntrack_nat_help help;
  #if defined(CONFIG_IP_NF_TARGET_MASQUERADE) || \
  	defined(CONFIG_IP_NF_TARGET_MASQUERADE_MODULE)
  		int masq_index;
  #endif
  	} nat;
  #endif /* CONFIG_IP_NF_NAT_NEEDED */
  
  };
  
  /* get master conntrack via master expectation */
  #define master_ct(conntr) (conntr->master ? conntr->master->expectant : NULL)
  
  /* Alter reply tuple (maybe alter helper).  If it's already taken,
     return 0 and don't do alteration. */
  extern int
  ip_conntrack_alter_reply(struct ip_conntrack *conntrack,
  			 const struct ip_conntrack_tuple *newreply);
  
  /* Is this tuple taken? (ignoring any belonging to the given
     conntrack). */
  extern int
  ip_conntrack_tuple_taken(const struct ip_conntrack_tuple *tuple,
  			 const struct ip_conntrack *ignored_conntrack);
  
  /* Return conntrack_info and tuple hash for given skb. */
  extern struct ip_conntrack *
  ip_conntrack_get(struct sk_buff *skb, enum ip_conntrack_info *ctinfo);
  
  /* decrement reference count on a conntrack */
  extern inline void ip_conntrack_put(struct ip_conntrack *ct);
  
  /* find unconfirmed expectation based on tuple */
  struct ip_conntrack_expect *
  ip_conntrack_expect_find_get(const struct ip_conntrack_tuple *tuple);
  
  /* decrement reference count on an expectation */
  void ip_conntrack_expect_put(struct ip_conntrack_expect *exp);
  
  /* call to create an explicit dependency on ip_conntrack. */
  extern void need_ip_conntrack(void);
  
  extern int invert_tuplepr(struct ip_conntrack_tuple *inverse,
  			  const struct ip_conntrack_tuple *orig);
  
  /* Refresh conntrack for this many jiffies */
  extern void ip_ct_refresh(struct ip_conntrack *ct,
  			  unsigned long extra_jiffies);
  
  /* These are for NAT.  Icky. */
  /* Call me when a conntrack is destroyed. */
  extern void (*ip_conntrack_destroyed)(struct ip_conntrack *conntrack);
  
  /* Returns new sk_buff, or NULL */
  struct sk_buff *
  ip_ct_gather_frags(struct sk_buff *skb);
  
  /* Delete all conntracks which match. */
  extern void
  ip_ct_selective_cleanup(int (*kill)(const struct ip_conntrack *i, void *data),
  			void *data);
  
  /* It's confirmed if it is, or has been in the hash table. */
  static inline int is_confirmed(struct ip_conntrack *ct)
  {
  	return test_bit(IPS_CONFIRMED_BIT, &ct->status);
  }
  
  extern unsigned int ip_conntrack_htable_size;
  
  /* eg. PROVIDES_CONNTRACK(ftp); */
  #define PROVIDES_CONNTRACK(name)                        \
          int needs_ip_conntrack_##name;                  \
          EXPORT_SYMBOL(needs_ip_conntrack_##name)
  
  /*. eg. NEEDS_CONNTRACK(ftp); */
  #define NEEDS_CONNTRACK(name)                                           \
          extern int needs_ip_conntrack_##name;                           \
          static int *need_ip_conntrack_##name __attribute_used__ = &needs_ip_conntrack_##name
  
  #endif /* __KERNEL__ */
  #endif /* _IP_CONNTRACK_H */
  