#ifndef __LINUX_NETFILTER_H
  #define __LINUX_NETFILTER_H
  
  #ifdef __KERNEL__
  #include <linux/init.h>

  #include <linux/skbuff.h>
  #include <linux/net.h>
  #include <linux/if.h>

  #include <linux/in.h>
  #include <linux/in6.h>

  #include <linux/wait.h>
  #include <linux/list.h>
  #endif

  #include <linux/types.h>

  #include <linux/compiler.h>

  #include <linux/sysctl.h>

  
  /* Responses from hook functions. */
  #define NF_DROP 0
  #define NF_ACCEPT 1
  #define NF_STOLEN 2
  #define NF_QUEUE 3
  #define NF_REPEAT 4
  #define NF_STOP 5
  #define NF_MAX_VERDICT NF_STOP

  /* we overload the higher bits for encoding auxiliary data such as the queue

   * number or errno values. Not nice, but better than additional function
   * arguments. */
  #define NF_VERDICT_MASK 0x000000ff
  
  /* extra verdict flags have mask 0x0000ff00 */

  #define NF_VERDICT_FLAG_QUEUE_BYPASS	0x00008000

  /* queue number (NF_QUEUE) or errno (NF_DROP) */

  #define NF_VERDICT_QMASK 0xffff0000
  #define NF_VERDICT_QBITS 16

  #define NF_QUEUE_NR(x) ((((x) << 16) & NF_VERDICT_QMASK) | NF_QUEUE)

  #define NF_DROP_ERR(x) (((-x) << 16) | NF_DROP)

  /* only for userspace compatibility */
  #ifndef __KERNEL__

  /* Generic cache responses from hook functions.
     <= 0x2000 is used for protocol-flags. */
  #define NFC_UNKNOWN 0x4000
  #define NFC_ALTERED 0x8000

  
  /* NF_VERDICT_BITS should be 8 now, but userspace might break if this changes */
  #define NF_VERDICT_BITS 16

  #endif

  enum nf_inet_hooks {
  	NF_INET_PRE_ROUTING,
  	NF_INET_LOCAL_IN,
  	NF_INET_FORWARD,
  	NF_INET_LOCAL_OUT,
  	NF_INET_POST_ROUTING,
  	NF_INET_NUMHOOKS
  };

  enum {
  	NFPROTO_UNSPEC =  0,
  	NFPROTO_IPV4   =  2,
  	NFPROTO_ARP    =  3,
  	NFPROTO_BRIDGE =  7,
  	NFPROTO_IPV6   = 10,
  	NFPROTO_DECNET = 12,
  	NFPROTO_NUMPROTO,
  };

  union nf_inet_addr {

  	__u32		all[4];

  	__be32		ip;
  	__be32		ip6[4];

  	struct in_addr	in;
  	struct in6_addr	in6;

  };

  #ifdef __KERNEL__

  #ifdef CONFIG_NETFILTER

  static inline int NF_DROP_GETERR(int verdict)
  {
  	return -(verdict >> NF_VERDICT_QBITS);
  }

  static inline int nf_inet_addr_cmp(const union nf_inet_addr *a1,
  				   const union nf_inet_addr *a2)
  {
  	return a1->all[0] == a2->all[0] &&
  	       a1->all[1] == a2->all[1] &&
  	       a1->all[2] == a2->all[2] &&
  	       a1->all[3] == a2->all[3];
  }

  extern void netfilter_init(void);
  
  /* Largest hook number + 1 */
  #define NF_MAX_HOOKS 8
  
  struct sk_buff;

  
  typedef unsigned int nf_hookfn(unsigned int hooknum,

  			       struct sk_buff *skb,

  			       const struct net_device *in,
  			       const struct net_device *out,
  			       int (*okfn)(struct sk_buff *));

  struct nf_hook_ops {

  	struct list_head list;
  
  	/* User fills in from here down. */
  	nf_hookfn *hook;
  	struct module *owner;

  	u_int8_t pf;
  	unsigned int hooknum;

  	/* Hooks are ordered in ascending priority. */
  	int priority;
  };

  struct nf_sockopt_ops {

  	struct list_head list;

  	u_int8_t pf;

  
  	/* Non-inclusive ranges: use 0/0/NULL to never get called. */
  	int set_optmin;
  	int set_optmax;
  	int (*set)(struct sock *sk, int optval, void __user *user, unsigned int len);

  #ifdef CONFIG_COMPAT

  	int (*compat_set)(struct sock *sk, int optval,
  			void __user *user, unsigned int len);

  #endif

  	int get_optmin;
  	int get_optmax;
  	int (*get)(struct sock *sk, int optval, void __user *user, int *len);

  #ifdef CONFIG_COMPAT

  	int (*compat_get)(struct sock *sk, int optval,
  			void __user *user, int *len);

  #endif

  	/* Use the module struct to lock set/get code in place */
  	struct module *owner;

  };

  /* Function to register/unregister hook points. */
  int nf_register_hook(struct nf_hook_ops *reg);
  void nf_unregister_hook(struct nf_hook_ops *reg);

  int nf_register_hooks(struct nf_hook_ops *reg, unsigned int n);
  void nf_unregister_hooks(struct nf_hook_ops *reg, unsigned int n);

  
  /* Functions to register get/setsockopt ranges (non-inclusive).  You
     need to check permissions yourself! */
  int nf_register_sockopt(struct nf_sockopt_ops *reg);
  void nf_unregister_sockopt(struct nf_sockopt_ops *reg);

  #ifdef CONFIG_SYSCTL
  /* Sysctl registration */

  extern struct ctl_path nf_net_netfilter_sysctl_path[];
  extern struct ctl_path nf_net_ipv4_netfilter_sysctl_path[];

  #endif /* CONFIG_SYSCTL */

  extern struct list_head nf_hooks[NFPROTO_NUMPROTO][NF_MAX_HOOKS];

  #if defined(CONFIG_JUMP_LABEL)
  #include <linux/jump_label.h>
  extern struct jump_label_key nf_hooks_needed[NFPROTO_NUMPROTO][NF_MAX_HOOKS];
  static inline bool nf_hooks_active(u_int8_t pf, unsigned int hook)
  {
  	if (__builtin_constant_p(pf) &&
  	    __builtin_constant_p(hook))
  		return static_branch(&nf_hooks_needed[pf][hook]);
  
  	return !list_empty(&nf_hooks[pf][hook]);
  }
  #else
  static inline bool nf_hooks_active(u_int8_t pf, unsigned int hook)
  {
  	return !list_empty(&nf_hooks[pf][hook]);
  }
  #endif

  int nf_hook_slow(u_int8_t pf, unsigned int hook, struct sk_buff *skb,

  		 struct net_device *indev, struct net_device *outdev,
  		 int (*okfn)(struct sk_buff *), int thresh);
  
  /**
   *	nf_hook_thresh - call a netfilter hook
   *	
   *	Returns 1 if the hook has allowed the packet to pass.  The function
   *	okfn must be invoked by the caller in this case.  Any other return
   *	value indicates the packet has been consumed by the hook.
   */

  static inline int nf_hook_thresh(u_int8_t pf, unsigned int hook,

  				 struct sk_buff *skb,

  				 struct net_device *indev,
  				 struct net_device *outdev,

  				 int (*okfn)(struct sk_buff *), int thresh)

  {

  	if (nf_hooks_active(pf, hook))
  		return nf_hook_slow(pf, hook, skb, indev, outdev, okfn, thresh);
  	return 1;

  }

  static inline int nf_hook(u_int8_t pf, unsigned int hook, struct sk_buff *skb,

  			  struct net_device *indev, struct net_device *outdev,
  			  int (*okfn)(struct sk_buff *))
  {

  	return nf_hook_thresh(pf, hook, skb, indev, outdev, okfn, INT_MIN);

  }

                     
  /* Activate hook; either okfn or kfree_skb called, unless a hook
     returns NF_STOLEN (in which case, it's up to the hook to deal with
     the consequences).
  
     Returns -ERRNO if packet dropped.  Zero means queued, stolen or
     accepted.
  */
  
  /* RR:
     > I don't want nf_hook to return anything because people might forget
     > about async and trust the return value to mean "packet was ok".
  
     AK:
     Just document it clearly, then you can expect some sense from kernel
     coders :)
  */

  static inline int
  NF_HOOK_THRESH(uint8_t pf, unsigned int hook, struct sk_buff *skb,
  	       struct net_device *in, struct net_device *out,
  	       int (*okfn)(struct sk_buff *), int thresh)
  {
  	int ret = nf_hook_thresh(pf, hook, skb, in, out, okfn, thresh);
  	if (ret == 1)
  		ret = okfn(skb);
  	return ret;
  }

  static inline int
  NF_HOOK_COND(uint8_t pf, unsigned int hook, struct sk_buff *skb,
  	     struct net_device *in, struct net_device *out,
  	     int (*okfn)(struct sk_buff *), bool cond)
  {

  	int ret;
  
  	if (!cond ||

  	    ((ret = nf_hook_thresh(pf, hook, skb, in, out, okfn, INT_MIN)) == 1))

  		ret = okfn(skb);
  	return ret;
  }

  static inline int
  NF_HOOK(uint8_t pf, unsigned int hook, struct sk_buff *skb,
  	struct net_device *in, struct net_device *out,
  	int (*okfn)(struct sk_buff *))
  {
  	return NF_HOOK_THRESH(pf, hook, skb, in, out, okfn, INT_MIN);
  }

  
  /* Call setsockopt() */

  int nf_setsockopt(struct sock *sk, u_int8_t pf, int optval, char __user *opt,

  		  unsigned int len);

  int nf_getsockopt(struct sock *sk, u_int8_t pf, int optval, char __user *opt,

  		  int *len);

  #ifdef CONFIG_COMPAT

  int compat_nf_setsockopt(struct sock *sk, u_int8_t pf, int optval,

  		char __user *opt, unsigned int len);

  int compat_nf_getsockopt(struct sock *sk, u_int8_t pf, int optval,

  		char __user *opt, int *len);

  #endif

  /* Call this before modifying an existing packet: ensures it is
     modifiable and linear to the point you care about (writable_len).
     Returns true or false. */

  extern int skb_make_writable(struct sk_buff *skb, unsigned int writable_len);

  struct flowi;

  struct nf_queue_entry;

  struct nf_afinfo {
  	unsigned short	family;

  	__sum16		(*checksum)(struct sk_buff *skb, unsigned int hook,

  				    unsigned int dataoff, u_int8_t protocol);

  	__sum16		(*checksum_partial)(struct sk_buff *skb,
  					    unsigned int hook,
  					    unsigned int dataoff,
  					    unsigned int len,
  					    u_int8_t protocol);

  	int		(*route)(struct net *net, struct dst_entry **dst,

  				 struct flowi *fl, bool strict);

  	void		(*saveroute)(const struct sk_buff *skb,

  				     struct nf_queue_entry *entry);

  	int		(*reroute)(struct sk_buff *skb,

  				   const struct nf_queue_entry *entry);

  	int		route_key_size;

  };

  extern const struct nf_afinfo __rcu *nf_afinfo[NFPROTO_NUMPROTO];

  static inline const struct nf_afinfo *nf_get_afinfo(unsigned short family)

  {
  	return rcu_dereference(nf_afinfo[family]);
  }

  static inline __sum16

  nf_checksum(struct sk_buff *skb, unsigned int hook, unsigned int dataoff,
  	    u_int8_t protocol, unsigned short family)
  {

  	const struct nf_afinfo *afinfo;

  	__sum16 csum = 0;

  
  	rcu_read_lock();
  	afinfo = nf_get_afinfo(family);
  	if (afinfo)
  		csum = afinfo->checksum(skb, hook, dataoff, protocol);
  	rcu_read_unlock();
  	return csum;
  }

  static inline __sum16
  nf_checksum_partial(struct sk_buff *skb, unsigned int hook,
  		    unsigned int dataoff, unsigned int len,
  		    u_int8_t protocol, unsigned short family)
  {
  	const struct nf_afinfo *afinfo;
  	__sum16 csum = 0;
  
  	rcu_read_lock();
  	afinfo = nf_get_afinfo(family);
  	if (afinfo)
  		csum = afinfo->checksum_partial(skb, hook, dataoff, len,
  						protocol);
  	rcu_read_unlock();
  	return csum;
  }

  extern int nf_register_afinfo(const struct nf_afinfo *afinfo);
  extern void nf_unregister_afinfo(const struct nf_afinfo *afinfo);

  #include <net/flow.h>
  extern void (*ip_nat_decode_session)(struct sk_buff *, struct flowi *);
  
  static inline void

  nf_nat_decode_session(struct sk_buff *skb, struct flowi *fl, u_int8_t family)

  {

  #ifdef CONFIG_NF_NAT_NEEDED

  	void (*decodefn)(struct sk_buff *, struct flowi *);

  	if (family == AF_INET) {
  		rcu_read_lock();
  		decodefn = rcu_dereference(ip_nat_decode_session);
  		if (decodefn)
  			decodefn(skb, fl);
  		rcu_read_unlock();
  	}

  #endif
  }

  #ifdef CONFIG_PROC_FS
  #include <linux/proc_fs.h>
  extern struct proc_dir_entry *proc_net_netfilter;
  #endif

  #else /* !CONFIG_NETFILTER */
  #define NF_HOOK(pf, hook, skb, indev, outdev, okfn) (okfn)(skb)

  #define NF_HOOK_COND(pf, hook, skb, indev, outdev, okfn, cond) (okfn)(skb)

  static inline int nf_hook_thresh(u_int8_t pf, unsigned int hook,

  				 struct sk_buff *skb,

  				 struct net_device *indev,
  				 struct net_device *outdev,

  				 int (*okfn)(struct sk_buff *), int thresh)

  {

  	return okfn(skb);

  }

  static inline int nf_hook(u_int8_t pf, unsigned int hook, struct sk_buff *skb,

  			  struct net_device *indev, struct net_device *outdev,
  			  int (*okfn)(struct sk_buff *))
  {

  	return 1;

  }

  struct flowi;

  static inline void

  nf_nat_decode_session(struct sk_buff *skb, struct flowi *fl, u_int8_t family)
  {
  }

  #endif /*CONFIG_NETFILTER*/

  #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)

  extern void (*ip_ct_attach)(struct sk_buff *, struct sk_buff *) __rcu;

  extern void nf_ct_attach(struct sk_buff *, struct sk_buff *);

  extern void (*nf_ct_destroy)(struct nf_conntrack *) __rcu;

  #else
  static inline void nf_ct_attach(struct sk_buff *new, struct sk_buff *skb) {}
  #endif

  #endif /*__KERNEL__*/
  #endif /*__LINUX_NETFILTER_H*/