1. 根目录:
2. include
3. uapi
4. linux
5. netfilter
6. nfnetlink.h

#ifndef _UAPI_NFNETLINK_H
#define _UAPI_NFNETLINK_H
#include <linux/types.h>
#include <linux/netfilter/nfnetlink_compat.h>

enum nfnetlink_groups {
	NFNLGRP_NONE,
#define NFNLGRP_NONE			NFNLGRP_NONE
	NFNLGRP_CONNTRACK_NEW,
#define NFNLGRP_CONNTRACK_NEW		NFNLGRP_CONNTRACK_NEW
	NFNLGRP_CONNTRACK_UPDATE,
#define NFNLGRP_CONNTRACK_UPDATE	NFNLGRP_CONNTRACK_UPDATE
	NFNLGRP_CONNTRACK_DESTROY,
#define NFNLGRP_CONNTRACK_DESTROY	NFNLGRP_CONNTRACK_DESTROY
	NFNLGRP_CONNTRACK_EXP_NEW,
#define	NFNLGRP_CONNTRACK_EXP_NEW	NFNLGRP_CONNTRACK_EXP_NEW
	NFNLGRP_CONNTRACK_EXP_UPDATE,
#define NFNLGRP_CONNTRACK_EXP_UPDATE	NFNLGRP_CONNTRACK_EXP_UPDATE
	NFNLGRP_CONNTRACK_EXP_DESTROY,
#define NFNLGRP_CONNTRACK_EXP_DESTROY	NFNLGRP_CONNTRACK_EXP_DESTROY
	__NFNLGRP_MAX,
};
#define NFNLGRP_MAX	(__NFNLGRP_MAX - 1)

/* General form of address family dependent message.
 */
struct nfgenmsg {
	__u8  nfgen_family;		/* AF_xxx */
	__u8  version;		/* nfnetlink version */
	__be16    res_id;		/* resource id */
};

#define NFNETLINK_V0	0

/* netfilter netlink message types are split in two pieces:
 * 8 bit subsystem, 8bit operation.
 */

#define NFNL_SUBSYS_ID(x)	((x & 0xff00) >> 8)
#define NFNL_MSG_TYPE(x)	(x & 0x00ff)

/* No enum here, otherwise __stringify() trick of MODULE_ALIAS_NFNL_SUBSYS()
 * won't work anymore */
#define NFNL_SUBSYS_NONE 		0
#define NFNL_SUBSYS_CTNETLINK		1
#define NFNL_SUBSYS_CTNETLINK_EXP	2
#define NFNL_SUBSYS_QUEUE		3
#define NFNL_SUBSYS_ULOG		4
#define NFNL_SUBSYS_OSF			5
#define NFNL_SUBSYS_IPSET		6
#define NFNL_SUBSYS_ACCT		7
#define NFNL_SUBSYS_CTNETLINK_TIMEOUT	8
#define NFNL_SUBSYS_CTHELPER		9
#define NFNL_SUBSYS_COUNT		10

#endif /* _UAPI_NFNETLINK_H */