1. 根目录:
2. include
3. linux
4. netfilter
5. nfnetlink_compat.h

#ifndef _NFNETLINK_COMPAT_H
#define _NFNETLINK_COMPAT_H

#include <linux/types.h>

#ifndef __KERNEL__
/* Old nfnetlink macros for userspace */

/* nfnetlink groups: Up to 32 maximum */
#define NF_NETLINK_CONNTRACK_NEW 		0x00000001
#define NF_NETLINK_CONNTRACK_UPDATE		0x00000002
#define NF_NETLINK_CONNTRACK_DESTROY		0x00000004
#define NF_NETLINK_CONNTRACK_EXP_NEW		0x00000008
#define NF_NETLINK_CONNTRACK_EXP_UPDATE		0x00000010
#define NF_NETLINK_CONNTRACK_EXP_DESTROY	0x00000020

/* Generic structure for encapsulation optional netfilter information.
 * It is reminiscent of sockaddr, but with sa_family replaced
 * with attribute type.
 * ! This should someday be put somewhere generic as now rtnetlink and
 * ! nfnetlink use the same attributes methods. - J. Schulist.
 */

struct nfattr {
	__u16 nfa_len;
	__u16 nfa_type;	/* we use 15 bits for the type, and the highest
				 * bit to indicate whether the payload is nested */
};

/* FIXME: Apart from NFNL_NFA_NESTED shamelessly copy and pasted from
 * rtnetlink.h, it's time to put this in a generic file */

#define NFNL_NFA_NEST	0x8000
#define NFA_TYPE(attr) 	((attr)->nfa_type & 0x7fff)

#define NFA_ALIGNTO     4
#define NFA_ALIGN(len)	(((len) + NFA_ALIGNTO - 1) & ~(NFA_ALIGNTO - 1))
#define NFA_OK(nfa,len)	((len) > 0 && (nfa)->nfa_len >= sizeof(struct nfattr) \
	&& (nfa)->nfa_len <= (len))
#define NFA_NEXT(nfa,attrlen)	((attrlen) -= NFA_ALIGN((nfa)->nfa_len), \
	(struct nfattr *)(((char *)(nfa)) + NFA_ALIGN((nfa)->nfa_len)))
#define NFA_LENGTH(len)	(NFA_ALIGN(sizeof(struct nfattr)) + (len))
#define NFA_SPACE(len)	NFA_ALIGN(NFA_LENGTH(len))
#define NFA_DATA(nfa)   ((void *)(((char *)(nfa)) + NFA_LENGTH(0)))
#define NFA_PAYLOAD(nfa) ((int)((nfa)->nfa_len) - NFA_LENGTH(0))
#define NFA_NEST(skb, type) \
({	struct nfattr *__start = (struct nfattr *)skb_tail_pointer(skb); \
	NFA_PUT(skb, (NFNL_NFA_NEST | type), 0, NULL); \
	__start;  })
#define NFA_NEST_END(skb, start) \
({      (start)->nfa_len = skb_tail_pointer(skb) - (unsigned char *)(start); \
        (skb)->len; })
#define NFA_NEST_CANCEL(skb, start) \
({      if (start) \
                skb_trim(skb, (unsigned char *) (start) - (skb)->data); \
        -1; })

#define NFM_NFA(n)      ((struct nfattr *)(((char *)(n)) \
        + NLMSG_ALIGN(sizeof(struct nfgenmsg))))
#define NFM_PAYLOAD(n)  NLMSG_PAYLOAD(n, sizeof(struct nfgenmsg))

#endif /* ! __KERNEL__ */
#endif /* _NFNETLINK_COMPAT_H */