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The C and C++ Include Header Files

/usr/include/linux/netfilter/nf_conntrack_tuple_common.h

$ cat -n /usr/include/linux/netfilter/nf_conntrack_tuple_common.h

     1	/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
     2	#ifndef _NF_CONNTRACK_TUPLE_COMMON_H
     3	#define _NF_CONNTRACK_TUPLE_COMMON_H
     4	
     5	#include <linux/types.h>
     6	#include <linux/netfilter.h>
     7	#include <linux/netfilter/nf_conntrack_common.h> /* IP_CT_IS_REPLY */
     8	
     9	enum ip_conntrack_dir {
    10		IP_CT_DIR_ORIGINAL,
    11		IP_CT_DIR_REPLY,
    12		IP_CT_DIR_MAX
    13	};
    14	
    15	/* The protocol-specific manipulable parts of the tuple: always in
    16	 * network order
    17	 */
    18	union nf_conntrack_man_proto {
    19		/* Add other protocols here. */
    20		__be16 all;
    21	
    22		struct {
    23			__be16 port;
    24		} tcp;
    25		struct {
    26			__be16 port;
    27		} udp;
    28		struct {
    29			__be16 id;
    30		} icmp;
    31		struct {
    32			__be16 port;
    33		} dccp;
    34		struct {
    35			__be16 port;
    36		} sctp;
    37		struct {
    38			__be16 key;	/* GRE key is 32bit, PPtP only uses 16bit */
    39		} gre;
    40	};
    41	
    42	#define CTINFO2DIR(ctinfo) ((ctinfo) >= IP_CT_IS_REPLY ? IP_CT_DIR_REPLY : IP_CT_DIR_ORIGINAL)
    43	
    44	#endif /* _NF_CONNTRACK_TUPLE_COMMON_H */

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