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/**  *	struct sock - network layer representation of sockets  *	@__sk_common: shared layout with inet_timewait_sock  *	@sk_shutdown: mask of %SEND_SHUTDOWN and/or %RCV_SHUTDOWN  *	@sk_userlocks: %SO_SNDBUF and %SO_RCVBUF settings  *	@sk_lock:	synchronizer  *	@sk_rcvbuf: size of receive buffer in bytes  *	@sk_wq: sock wait queue and async head  *	@sk_rx_dst: receive input route used by early demux  *	@sk_dst_cache: destination cache  *	@sk_policy: flow policy  *	@sk_receive_queue: incoming packets  *	@sk_wmem_alloc: transmit queue bytes committed  *	@sk_write_queue: Packet sending queue  *	@sk_omem_alloc: "o" is "option" or "other"  *	@sk_wmem_queued: persistent queue size  *	@sk_forward_alloc: space allocated forward  *	@sk_napi_id: id of the last napi context to receive data for sk  *	@sk_ll_usec: usecs to busypoll when there is no data  *	@sk_allocation: allocation mode  *	@sk_pacing_rate: Pacing rate (if supported by transport/packet scheduler)  *	@sk_max_pacing_rate: Maximum pacing rate (%SO_MAX_PACING_RATE)  *	@sk_sndbuf: size of send buffer in bytes  *	@sk_padding: unused element for alignment  *	@sk_no_check_tx: %SO_NO_CHECK setting, set checksum in TX packets  *	@sk_no_check_rx: allow zero checksum in RX packets  *	@sk_route_caps: route capabilities (e.g. %NETIF_F_TSO)  *	@sk_route_nocaps: forbidden route capabilities (e.g NETIF_F_GSO_MASK)  *	@sk_gso_type: GSO type (e.g. %SKB_GSO_TCPV4)  *	@sk_gso_max_size: Maximum GSO segment size to build  *	@sk_gso_max_segs: Maximum number of GSO segments  *	@sk_lingertime: %SO_LINGER l_linger setting  *	@sk_backlog: always used with the per-socket spinlock held  *	@sk_callback_lock: used with the callbacks in the end of this struct  *	@sk_error_queue: rarely used  *	@sk_prot_creator: sk_prot of original sock creator (see ipv6_setsockopt,  *			  IPV6_ADDRFORM for instance)  *	@sk_err: last error  *	@sk_err_soft: errors that don't cause failure but are the cause of a  *		      persistent failure not just 'timed out'  *	@sk_drops: raw/udp drops counter  *	@sk_ack_backlog: current listen backlog  *	@sk_max_ack_backlog: listen backlog set in listen()  *	@sk_priority: %SO_PRIORITY setting  *	@sk_type: socket type (%SOCK_STREAM, etc)  *	@sk_protocol: which protocol this socket belongs in this network family  *	@sk_peer_pid: &struct pid for this socket's peer  *	@sk_peer_cred: %SO_PEERCRED setting  *	@sk_rcvlowat: %SO_RCVLOWAT setting  *	@sk_rcvtimeo: %SO_RCVTIMEO setting  *	@sk_sndtimeo: %SO_SNDTIMEO setting  *	@sk_txhash: computed flow hash for use on transmit  *	@sk_filter: socket filtering instructions  *	@sk_timer: sock cleanup timer  *	@sk_stamp: time stamp of last packet received  *	@sk_tsflags: SO_TIMESTAMPING socket options  *	@sk_tskey: counter to disambiguate concurrent tstamp requests  *	@sk_socket: Identd and reporting IO signals  *	@sk_user_data: RPC layer private data  *	@sk_frag: cached page frag  *	@sk_peek_off: current peek_offset value  *	@sk_send_head: front of stuff to transmit  *	@sk_security: used by security modules  *	@sk_mark: generic packet mark  *	@sk_cgrp_data: cgroup data for this cgroup  *	@sk_memcg: this socket's memory cgroup association  *	@sk_write_pending: a write to stream socket waits to start  *	@sk_state_change: callback to indicate change in the state of the sock  *	@sk_data_ready: callback to indicate there is data to be processed  *	@sk_write_space: callback to indicate there is bf sending space available  *	@sk_error_report: callback to indicate errors (e.g. %MSG_ERRQUEUE)  *	@sk_backlog_rcv: callback to process the backlog  *	@sk_destruct: called at sock freeing time, i.e. when all refcnt == 0  *	@sk_reuseport_cb: reuseport group container  *	@sk_rcu: used during RCU grace period  */struct sock {	/*	 * Now struct inet_timewait_sock also uses sock_common, so please just	 * don't add nothing before this first member (__sk_common) --acme	 */	struct sock_common	__sk_common;#define sk_node			__sk_common.skc_node#define sk_nulls_node		__sk_common.skc_nulls_node#define sk_refcnt		__sk_common.skc_refcnt#define sk_tx_queue_mapping	__sk_common.skc_tx_queue_mapping#define sk_dontcopy_begin	__sk_common.skc_dontcopy_begin#define sk_dontcopy_end		__sk_common.skc_dontcopy_end#define sk_hash			__sk_common.skc_hash#define sk_portpair		__sk_common.skc_portpair#define sk_num			__sk_common.skc_num#define sk_dport		__sk_common.skc_dport#define sk_addrpair		__sk_common.skc_addrpair#define sk_daddr		__sk_common.skc_daddr#define sk_rcv_saddr		__sk_common.skc_rcv_saddr#define sk_family		__sk_common.skc_family#define sk_state		__sk_common.skc_state#define sk_reuse		__sk_common.skc_reuse#define sk_reuseport		__sk_common.skc_reuseport#define sk_ipv6only		__sk_common.skc_ipv6only#define sk_net_refcnt		__sk_common.skc_net_refcnt#define sk_bound_dev_if		__sk_common.skc_bound_dev_if#define sk_bind_node		__sk_common.skc_bind_node#define sk_prot			__sk_common.skc_prot#define sk_net			__sk_common.skc_net#define sk_v6_daddr		__sk_common.skc_v6_daddr#define sk_v6_rcv_saddr	__sk_common.skc_v6_rcv_saddr#define sk_cookie		__sk_common.skc_cookie#define sk_incoming_cpu		__sk_common.skc_incoming_cpu#define sk_flags		__sk_common.skc_flags#define sk_rxhash		__sk_common.skc_rxhash	socket_lock_t		sk_lock;	struct sk_buff_head	sk_receive_queue;	/*	 * The backlog queue is special, it is always used with	 * the per-socket spinlock held and requires low latency	 * access. Therefore we special case it's implementation.	 * Note : rmem_alloc is in this structure to fill a hole	 * on 64bit arches, not because its logically part of	 * backlog.	 */	struct {		atomic_t	rmem_alloc;		int		len;		struct sk_buff	*head;		struct sk_buff	*tail;	} sk_backlog;#define sk_rmem_alloc sk_backlog.rmem_alloc	int			sk_forward_alloc;	__u32			sk_txhash;#ifdef CONFIG_NET_RX_BUSY_POLL	unsigned int		sk_napi_id;	unsigned int		sk_ll_usec;#endif	atomic_t		sk_drops;	int			sk_rcvbuf;	struct sk_filter __rcu	*sk_filter;	union {		struct socket_wq __rcu	*sk_wq;		struct socket_wq	*sk_wq_raw;	};#ifdef CONFIG_XFRM	struct xfrm_policy __rcu *sk_policy[2];#endif	struct dst_entry	*sk_rx_dst;	struct dst_entry __rcu	*sk_dst_cache;	/* Note: 32bit hole on 64bit arches */	atomic_t		sk_wmem_alloc;	atomic_t		sk_omem_alloc;	int			sk_sndbuf;	struct sk_buff_head	sk_write_queue;	/*	 * Because of non atomicity rules, all	 * changes are protected by socket lock.	 */	kmemcheck_bitfield_begin(flags);	unsigned int		sk_padding : 2,				sk_no_check_tx : 1,				sk_no_check_rx : 1,				sk_userlocks : 4,				sk_protocol  : 8,				sk_type      : 16;#define SK_PROTOCOL_MAX U8_MAX	kmemcheck_bitfield_end(flags);	int			sk_wmem_queued;	gfp_t			sk_allocation;	u32			sk_pacing_rate; /* bytes per second */	u32			sk_max_pacing_rate;	netdev_features_t	sk_route_caps;	netdev_features_t	sk_route_nocaps;	int			sk_gso_type;	unsigned int		sk_gso_max_size;	u16			sk_gso_max_segs;	int			sk_rcvlowat;	unsigned long	        sk_lingertime;	struct sk_buff_head	sk_error_queue;	struct proto		*sk_prot_creator;	rwlock_t		sk_callback_lock;	int			sk_err,				sk_err_soft;	u32			sk_ack_backlog;	u32			sk_max_ack_backlog;	__u32			sk_priority;	__u32			sk_mark;	struct pid		*sk_peer_pid;	const struct cred	*sk_peer_cred;	long			sk_rcvtimeo;	long			sk_sndtimeo;	struct timer_list	sk_timer;	ktime_t			sk_stamp;	u16			sk_tsflags;	u8			sk_shutdown;	u32			sk_tskey;	struct socket		*sk_socket;	void			*sk_user_data;	struct page_frag	sk_frag;	struct sk_buff		*sk_send_head;	__s32			sk_peek_off;	int			sk_write_pending;#ifdef CONFIG_SECURITY	void			*sk_security;#endif	struct sock_cgroup_data	sk_cgrp_data;	struct mem_cgroup	*sk_memcg;	void			(*sk_state_change)(struct sock *sk);	void			(*sk_data_ready)(struct sock *sk);	void			(*sk_write_space)(struct sock *sk);	void			(*sk_error_report)(struct sock *sk);	int			(*sk_backlog_rcv)(struct sock *sk,						  struct sk_buff *skb);	void                    (*sk_destruct)(struct sock *sk);	struct sock_reuseport __rcu	*sk_reuseport_cb;	struct rcu_head		sk_rcu;};

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