text: #ifndef _NF_NAT_HELPER_H
  #define _NF_NAT_HELPER_H
  /* NAT protocol helper routines. */
  
  #include <net/netfilter/nf_conntrack.h>
  
  struct sk_buff;
  
  /* These return true or false. */
  extern int __nf_nat_mangle_tcp_packet(struct sk_buff *skb,
  				      struct nf_conn *ct,
  				      enum ip_conntrack_info ctinfo,
  				      unsigned int match_offset,
  				      unsigned int match_len,
  				      const char *rep_buffer,
  				      unsigned int rep_len, bool adjust);
  
  static inline int nf_nat_mangle_tcp_packet(struct sk_buff *skb,
  					   struct nf_conn *ct,
  					   enum ip_conntrack_info ctinfo,
  					   unsigned int match_offset,
  					   unsigned int match_len,
  					   const char *rep_buffer,
  					   unsigned int rep_len)
  {
  	return __nf_nat_mangle_tcp_packet(skb, ct, ctinfo,
  					  match_offset, match_len,
  					  rep_buffer, rep_len, true);
  }
  
  extern int nf_nat_mangle_udp_packet(struct sk_buff *skb,
  				    struct nf_conn *ct,
  				    enum ip_conntrack_info ctinfo,
  				    unsigned int match_offset,
  				    unsigned int match_len,
  				    const char *rep_buffer,
  				    unsigned int rep_len);
  
  extern void nf_nat_set_seq_adjust(struct nf_conn *ct,
  				  enum ip_conntrack_info ctinfo,
  				  __be32 seq, s16 off);
  extern int nf_nat_seq_adjust(struct sk_buff *skb,
  			     struct nf_conn *ct,
  			     enum ip_conntrack_info ctinfo);
  
  /* Setup NAT on this expected conntrack so it follows master, but goes
   * to port ct->master->saved_proto. */
  extern void nf_nat_follow_master(struct nf_conn *ct,
  				 struct nf_conntrack_expect *this);
  
  extern s16 nf_nat_get_offset(const struct nf_conn *ct,
  			     enum ip_conntrack_dir dir,
  			     u32 seq);
  #endif
  