include/linux/netfilter_ipv4/ip_nat.h

#ifndef _IP_NAT_H
#define _IP_NAT_H
#include <linux/netfilter_ipv4.h>
#include <linux/netfilter_ipv4/ip_conntrack_tuple.h>

#define IP_NAT_MAPPING_TYPE_MAX_NAMELEN 16

enum ip_nat_manip_type
{
	IP_NAT_MANIP_SRC,
	IP_NAT_MANIP_DST
};

/* SRC manip occurs POST_ROUTING or LOCAL_IN */
#define HOOK2MANIP(hooknum) ((hooknum) != NF_IP_POST_ROUTING && (hooknum) != NF_IP_LOCAL_IN)

/* 2.3.19 (I hope) will define this in linux/netfilter_ipv4.h. */
#ifndef SO_ORIGINAL_DST
#define SO_ORIGINAL_DST 80
#endif

#define IP_NAT_RANGE_MAP_IPS 1
#define IP_NAT_RANGE_PROTO_SPECIFIED 2
/* Used internally by get_unique_tuple(). */
#define IP_NAT_RANGE_FULL 4

/* NAT sequence number modifications */
struct ip_nat_seq {
	/* position of the last TCP sequence number 
	 * modification (if any) */
	u_int32_t correction_pos;
	/* sequence number offset before and after last modification */
	int32_t offset_before, offset_after;
};

/* Single range specification. */
struct ip_nat_range
{
	/* Set to OR of flags above. */
	unsigned int flags;

	/* Inclusive: network order. */
	u_int32_t min_ip, max_ip;

	/* Inclusive: network order */
	union ip_conntrack_manip_proto min, max;
};

/* A range consists of an array of 1 or more ip_nat_range */
struct ip_nat_multi_range
{
	unsigned int rangesize;

	/* hangs off end. */
	struct ip_nat_range range[1];
};

/* Worst case: local-out manip + 1 post-routing, and reverse dirn. */
#define IP_NAT_MAX_MANIPS (2*3)

struct ip_nat_info_manip
{
	/* The direction. */
	u_int8_t direction;

	/* Which hook the manipulation happens on. */
	u_int8_t hooknum;

	/* The manipulation type. */
	u_int8_t maniptype;

	/* Manipulations to occur at each conntrack in this dirn. */
	struct ip_conntrack_manip manip;
};

#ifdef __KERNEL__
#include <linux/list.h>
#include <linux/netfilter_ipv4/lockhelp.h>

/* Protects NAT hash tables, and NAT-private part of conntracks. */
DECLARE_RWLOCK_EXTERN(ip_nat_lock);

/* Hashes for by-source and IP/protocol. */
struct ip_nat_hash
{
	struct list_head list;

	/* conntrack we're embedded in: NULL if not in hash. */
	struct ip_conntrack *conntrack;
};

/* The structure embedded in the conntrack structure. */
struct ip_nat_info
{
	/* Set to zero when conntrack created: bitmask of maniptypes */
	int initialized;

	unsigned int num_manips;

	/* Manipulations to be done on this conntrack. */
	struct ip_nat_info_manip manips[IP_NAT_MAX_MANIPS];

	struct ip_nat_hash bysource, byipsproto;

	/* Helper (NULL if none). */
	struct ip_nat_helper *helper;

	struct ip_nat_seq seq[IP_CT_DIR_MAX];
};

/* Set up the info structure to map into this range. */
extern unsigned int ip_nat_setup_info(struct ip_conntrack *conntrack,
				      const struct ip_nat_multi_range *mr,
				      unsigned int hooknum);

/* Is this tuple already taken? (not by us)*/
extern int ip_nat_used_tuple(const struct ip_conntrack_tuple *tuple,
			     const struct ip_conntrack *ignored_conntrack);

/* Calculate relative checksum. */
extern u_int16_t ip_nat_cheat_check(u_int32_t oldvalinv,
				    u_int32_t newval,
				    u_int16_t oldcheck);
#endif /*__KERNEL__*/
#endif