sock.h

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/*
 * INET     An implementation of the TCP/IP protocol suite for the LINUX
 *      operating system.  INET is implemented using the  BSD Socket
 *      interface as the means of communication with the user level.
 *
 *      Definitions for the AF_INET socket handler.
 *
 * Version: @(#)sock.h  1.0.4   05/13/93
 *
 * Authors: Ross Biro
 *      Fred N. van Kempen, <[email protected]>
 *      Corey Minyard <[email protected]>
 *      Florian La Roche <[email protected]>
 *
 * Fixes:
 *      Alan Cox    :   Volatiles in skbuff pointers. See
 *                  skbuff comments. May be overdone,
 *                  better to prove they can be removed
 *                  than the reverse.
 *      Alan Cox    :   Added a zapped field for tcp to note
 *                  a socket is reset and must stay shut up
 *      Alan Cox    :   New fields for options
 *  Pauline Middelink   :   identd support
 *      Alan Cox    :   Eliminate low level recv/recvfrom
 *      David S. Miller :   New socket lookup architecture.
 *              Steve Whitehouse:       Default routines for sock_ops
 *              Arnaldo C. Melo :   removed net_pinfo, tp_pinfo and made
 *                          protinfo be just a void pointer, as the
 *                          protocol specific parts were moved to
 *                          respective headers and ipv4/v6, etc now
 *                          use private slabcaches for its socks
 *              Pedro Hortas    :   New flags field for socket options
 *
 *
 *      This program is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU General Public License
 *      as published by the Free Software Foundation; either version
 *      2 of the License, or (at your option) any later version.
 */
#ifndef _SOCK_H
#define _SOCK_H

#include <linux/hardirq.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/list_nulls.h>
#include <linux/timer.h>
#include <linux/cache.h>
#include <linux/bitops.h>
#include <linux/lockdep.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>   /* struct sk_buff */
#include <linux/mm.h>
#include <linux/security.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/memcontrol.h>
#include <linux/res_counter.h>
#include <linux/static_key.h>
#include <linux/aio.h>
#include <linux/sched.h>

#include <linux/filter.h>
#include <linux/rculist_nulls.h>
#include <linux/poll.h>

#include <linux/atomic.h>
#include <net/dst.h>
#include <net/checksum.h>

struct cgroup;
struct cgroup_subsys;
#ifdef CONFIG_NET
int mem_cgroup_sockets_init(struct mem_cgroup *memcg, struct cgroup_subsys *ss);
void mem_cgroup_sockets_destroy(struct mem_cgroup *memcg);
#else
static inline
int mem_cgroup_sockets_init(struct mem_cgroup *memcg, struct cgroup_subsys *ss)
{
    return 0;
}
static inline
void mem_cgroup_sockets_destroy(struct mem_cgroup *memcg)
{
}
#endif
/*
 * This structure really needs to be cleaned up.
 * Most of it is for TCP, and not used by any of
 * the other protocols.
 */

/* Define this to get the SOCK_DBG debugging facility. */
#define SOCK_DEBUGGING
#ifdef SOCK_DEBUGGING
#define SOCK_DEBUG(sk, msg...) do { if ((sk) && sock_flag((sk), SOCK_DBG)) \
                    printk(KERN_DEBUG msg); } while (0)
#else
/* Validate arguments and do nothing */
static inline __printf(2, 3)
void SOCK_DEBUG(const struct sock *sk, const char *msg, ...)
{
}
#endif

/* This is the per-socket lock.  The spinlock provides a synchronization
 * between user contexts and software interrupt processing, whereas the
 * mini-semaphore synchronizes multiple users amongst themselves.
 */
typedef struct {
    spinlock_t      slock;
    int         owned;
    wait_queue_head_t   wq;
    /*
     * We express the mutex-alike socket_lock semantics
     * to the lock validator by explicitly managing
     * the slock as a lock variant (in addition to
     * the slock itself):
     */
#ifdef CONFIG_DEBUG_LOCK_ALLOC
    struct lockdep_map dep_map;
#endif
} socket_lock_t;

struct sock;
struct proto;
struct net;

struct sock_common {
    /* skc_daddr and skc_rcv_saddr must be grouped :
     * cf INET_MATCH() and INET_TW_MATCH()
     */
    __be32          skc_daddr;
    __be32          skc_rcv_saddr;

    union  {
        unsigned int    skc_hash;
        __u16       skc_u16hashes[2];
    };
    unsigned short      skc_family;
    volatile unsigned char  skc_state;
    unsigned char       skc_reuse;
    int         skc_bound_dev_if;
    union {
        struct hlist_node   skc_bind_node;
        struct hlist_nulls_node skc_portaddr_node;
    };
    struct proto        *skc_prot;
#ifdef CONFIG_NET_NS
    struct net      *skc_net;
#endif
    /*
     * fields between dontcopy_begin/dontcopy_end
     * are not copied in sock_copy()
     */
    /* private: */
    int         skc_dontcopy_begin[0];
    /* public: */
    union {
        struct hlist_node   skc_node;
        struct hlist_nulls_node skc_nulls_node;
    };
    int         skc_tx_queue_mapping;
    atomic_t        skc_refcnt;
    /* private: */
    int                     skc_dontcopy_end[0];
    /* public: */
};

struct cg_proto;
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_family       __sk_common.skc_family
#define sk_state        __sk_common.skc_state
#define sk_reuse        __sk_common.skc_reuse
#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
    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;
#ifdef CONFIG_RPS
    __u32           sk_rxhash;
#endif
    atomic_t        sk_drops;
    int         sk_rcvbuf;

    struct sk_filter __rcu  *sk_filter;
    struct socket_wq __rcu  *sk_wq;

#ifdef CONFIG_NET_DMA
    struct sk_buff_head sk_async_wait_queue;
#endif

#ifdef CONFIG_XFRM
    struct xfrm_policy  *sk_policy[2];
#endif
    unsigned long       sk_flags;
    struct dst_entry    *sk_rx_dst;
    struct dst_entry    *sk_dst_cache;
    spinlock_t      sk_dst_lock;
    atomic_t        sk_wmem_alloc;
    atomic_t        sk_omem_alloc;
    int         sk_sndbuf;
    struct sk_buff_head sk_write_queue;
    kmemcheck_bitfield_begin(flags);
    unsigned int        sk_shutdown  : 2,
                sk_no_check  : 2,
                sk_userlocks : 4,
                sk_protocol  : 8,
                sk_type      : 16;
    kmemcheck_bitfield_end(flags);
    int         sk_wmem_queued;
    gfp_t           sk_allocation;
    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;
    unsigned short      sk_ack_backlog;
    unsigned short      sk_max_ack_backlog;
    __u32           sk_priority;
#ifdef CONFIG_CGROUPS
    __u32           sk_cgrp_prioidx;
#endif
    struct pid      *sk_peer_pid;
    const struct cred   *sk_peer_cred;
    long            sk_rcvtimeo;
    long            sk_sndtimeo;
    void            *sk_protinfo;
    struct timer_list   sk_timer;
    ktime_t         sk_stamp;
    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
    __u32           sk_mark;
    u32         sk_classid;
    struct cg_proto     *sk_cgrp;
    void            (*sk_state_change)(struct sock *sk);
    void            (*sk_data_ready)(struct sock *sk, int bytes);
    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);
};

/*
 * SK_CAN_REUSE and SK_NO_REUSE on a socket mean that the socket is OK
 * or not whether his port will be reused by someone else. SK_FORCE_REUSE
 * on a socket means that the socket will reuse everybody else's port
 * without looking at the other's sk_reuse value.
 */

#define SK_NO_REUSE 0
#define SK_CAN_REUSE    1
#define SK_FORCE_REUSE  2

static inline int sk_peek_offset(struct sock *sk, int flags)
{
    if ((flags & MSG_PEEK) && (sk->sk_peek_off >= 0))
        return sk->sk_peek_off;
    else
        return 0;
}

static inline void sk_peek_offset_bwd(struct sock *sk, int val)
{
    if (sk->sk_peek_off >= 0) {
        if (sk->sk_peek_off >= val)
            sk->sk_peek_off -= val;
        else
            sk->sk_peek_off = 0;
    }
}

static inline void sk_peek_offset_fwd(struct sock *sk, int val)
{
    if (sk->sk_peek_off >= 0)
        sk->sk_peek_off += val;
}

/*
 * Hashed lists helper routines
 */
static inline struct sock *sk_entry(const struct hlist_node *node)
{
    return hlist_entry(node, struct sock, sk_node);
}

static inline struct sock *__sk_head(const struct hlist_head *head)
{
    return hlist_entry(head->first, struct sock, sk_node);
}

static inline struct sock *sk_head(const struct hlist_head *head)
{
    return hlist_empty(head) ? NULL : __sk_head(head);
}

static inline struct sock *__sk_nulls_head(const struct hlist_nulls_head *head)
{
    return hlist_nulls_entry(head->first, struct sock, sk_nulls_node);
}

static inline struct sock *sk_nulls_head(const struct hlist_nulls_head *head)
{
    return hlist_nulls_empty(head) ? NULL : __sk_nulls_head(head);
}

static inline struct sock *sk_next(const struct sock *sk)
{
    return sk->sk_node.next ?
        hlist_entry(sk->sk_node.next, struct sock, sk_node) : NULL;
}

static inline struct sock *sk_nulls_next(const struct sock *sk)
{
    return (!is_a_nulls(sk->sk_nulls_node.next)) ?
        hlist_nulls_entry(sk->sk_nulls_node.next,
                  struct sock, sk_nulls_node) :
        NULL;
}

static inline bool sk_unhashed(const struct sock *sk)
{
    return hlist_unhashed(&sk->sk_node);
}

static inline bool sk_hashed(const struct sock *sk)
{
    return !sk_unhashed(sk);
}

static inline void sk_node_init(struct hlist_node *node)
{
    node->pprev = NULL;
}

static inline void sk_nulls_node_init(struct hlist_nulls_node *node)
{
    node->pprev = NULL;
}

static inline void __sk_del_node(struct sock *sk)
{
    __hlist_del(&sk->sk_node);
}

/* NB: equivalent to hlist_del_init_rcu */
static inline bool __sk_del_node_init(struct sock *sk)
{
    if (sk_hashed(sk)) {
        __sk_del_node(sk);
        sk_node_init(&sk->sk_node);
        return true;
    }
    return false;
}

/* Grab socket reference count. This operation is valid only
   when sk is ALREADY grabbed f.e. it is found in hash table
   or a list and the lookup is made under lock preventing hash table
   modifications.
 */

static inline void sock_hold(struct sock *sk)
{
    atomic_inc(&sk->sk_refcnt);
}

/* Ungrab socket in the context, which assumes that socket refcnt
   cannot hit zero, f.e. it is true in context of any socketcall.
 */
static inline void __sock_put(struct sock *sk)
{
    atomic_dec(&sk->sk_refcnt);
}

static inline bool sk_del_node_init(struct sock *sk)
{
    bool rc = __sk_del_node_init(sk);

    if (rc) {
        /* paranoid for a while -acme */
        WARN_ON(atomic_read(&sk->sk_refcnt) == 1);
        __sock_put(sk);
    }
    return rc;
}
#define sk_del_node_init_rcu(sk)    sk_del_node_init(sk)

static inline bool __sk_nulls_del_node_init_rcu(struct sock *sk)
{
    if (sk_hashed(sk)) {
        hlist_nulls_del_init_rcu(&sk->sk_nulls_node);
        return true;
    }
    return false;
}

static inline bool sk_nulls_del_node_init_rcu(struct sock *sk)
{
    bool rc = __sk_nulls_del_node_init_rcu(sk);

    if (rc) {
        /* paranoid for a while -acme */
        WARN_ON(atomic_read(&sk->sk_refcnt) == 1);
        __sock_put(sk);
    }
    return rc;
}

static inline void __sk_add_node(struct sock *sk, struct hlist_head *list)
{
    hlist_add_head(&sk->sk_node, list);
}

static inline void sk_add_node(struct sock *sk, struct hlist_head *list)
{
    sock_hold(sk);
    __sk_add_node(sk, list);
}

static inline void sk_add_node_rcu(struct sock *sk, struct hlist_head *list)
{
    sock_hold(sk);
    hlist_add_head_rcu(&sk->sk_node, list);
}

static inline void __sk_nulls_add_node_rcu(struct sock *sk, struct hlist_nulls_head *list)
{
    hlist_nulls_add_head_rcu(&sk->sk_nulls_node, list);
}

static inline void sk_nulls_add_node_rcu(struct sock *sk, struct hlist_nulls_head *list)
{
    sock_hold(sk);
    __sk_nulls_add_node_rcu(sk, list);
}

static inline void __sk_del_bind_node(struct sock *sk)
{
    __hlist_del(&sk->sk_bind_node);
}

static inline void sk_add_bind_node(struct sock *sk,
                    struct hlist_head *list)
{
    hlist_add_head(&sk->sk_bind_node, list);
}

#define sk_for_each(__sk, node, list) \
    hlist_for_each_entry(__sk, node, list, sk_node)
#define sk_for_each_rcu(__sk, node, list) \
    hlist_for_each_entry_rcu(__sk, node, list, sk_node)
#define sk_nulls_for_each(__sk, node, list) \
    hlist_nulls_for_each_entry(__sk, node, list, sk_nulls_node)
#define sk_nulls_for_each_rcu(__sk, node, list) \
    hlist_nulls_for_each_entry_rcu(__sk, node, list, sk_nulls_node)
#define sk_for_each_from(__sk, node) \
    if (__sk && ({ node = &(__sk)->sk_node; 1; })) \
        hlist_for_each_entry_from(__sk, node, sk_node)
#define sk_nulls_for_each_from(__sk, node) \
    if (__sk && ({ node = &(__sk)->sk_nulls_node; 1; })) \
        hlist_nulls_for_each_entry_from(__sk, node, sk_nulls_node)
#define sk_for_each_safe(__sk, node, tmp, list) \
    hlist_for_each_entry_safe(__sk, node, tmp, list, sk_node)
#define sk_for_each_bound(__sk, node, list) \
    hlist_for_each_entry(__sk, node, list, sk_bind_node)

static inline struct user_namespace *sk_user_ns(struct sock *sk)
{
    /* Careful only use this in a context where these parameters
     * can not change and must all be valid, such as recvmsg from
     * userspace.
     */
    return sk->sk_socket->file->f_cred->user_ns;
}

/* Sock flags */
enum sock_flags {
    SOCK_DEAD,
    SOCK_DONE,
    SOCK_URGINLINE,
    SOCK_KEEPOPEN,
    SOCK_LINGER,
    SOCK_DESTROY,
    SOCK_BROADCAST,
    SOCK_TIMESTAMP,
    SOCK_ZAPPED,
    SOCK_USE_WRITE_QUEUE, /* whether to call sk->sk_write_space in sock_wfree */
    SOCK_DBG, /* %SO_DEBUG setting */
    SOCK_RCVTSTAMP, /* %SO_TIMESTAMP setting */
    SOCK_RCVTSTAMPNS, /* %SO_TIMESTAMPNS setting */
    SOCK_LOCALROUTE, /* route locally only, %SO_DONTROUTE setting */
    SOCK_QUEUE_SHRUNK, /* write queue has been shrunk recently */
    SOCK_MEMALLOC, /* VM depends on this socket for swapping */
    SOCK_TIMESTAMPING_TX_HARDWARE,  /* %SOF_TIMESTAMPING_TX_HARDWARE */
    SOCK_TIMESTAMPING_TX_SOFTWARE,  /* %SOF_TIMESTAMPING_TX_SOFTWARE */
    SOCK_TIMESTAMPING_RX_HARDWARE,  /* %SOF_TIMESTAMPING_RX_HARDWARE */
    SOCK_TIMESTAMPING_RX_SOFTWARE,  /* %SOF_TIMESTAMPING_RX_SOFTWARE */
    SOCK_TIMESTAMPING_SOFTWARE,     /* %SOF_TIMESTAMPING_SOFTWARE */
    SOCK_TIMESTAMPING_RAW_HARDWARE, /* %SOF_TIMESTAMPING_RAW_HARDWARE */
    SOCK_TIMESTAMPING_SYS_HARDWARE, /* %SOF_TIMESTAMPING_SYS_HARDWARE */
    SOCK_FASYNC, /* fasync() active */
    SOCK_RXQ_OVFL,
    SOCK_ZEROCOPY, /* buffers from userspace */
    SOCK_WIFI_STATUS, /* push wifi status to userspace */
    SOCK_NOFCS, /* Tell NIC not to do the Ethernet FCS.
             * Will use last 4 bytes of packet sent from
             * user-space instead.
             */
};

static inline void sock_copy_flags(struct sock *nsk, struct sock *osk)
{
    nsk->sk_flags = osk->sk_flags;
}

static inline void sock_set_flag(struct sock *sk, enum sock_flags flag)
{
    __set_bit(flag, &sk->sk_flags);
}

static inline void sock_reset_flag(struct sock *sk, enum sock_flags flag)
{
    __clear_bit(flag, &sk->sk_flags);
}

static inline bool sock_flag(const struct sock *sk, enum sock_flags flag)
{
    return test_bit(flag, &sk->sk_flags);
}

#ifdef CONFIG_NET
extern struct static_key memalloc_socks;
static inline int sk_memalloc_socks(void)
{
    return static_key_false(&memalloc_socks);
}
#else

static inline int sk_memalloc_socks(void)
{
    return 0;
}

#endif

static inline gfp_t sk_gfp_atomic(struct sock *sk, gfp_t gfp_mask)
{
    return GFP_ATOMIC | (sk->sk_allocation & __GFP_MEMALLOC);
}

static inline void sk_acceptq_removed(struct sock *sk)
{
    sk->sk_ack_backlog--;
}

static inline void sk_acceptq_added(struct sock *sk)
{
    sk->sk_ack_backlog++;
}

static inline bool sk_acceptq_is_full(const struct sock *sk)
{
    return sk->sk_ack_backlog > sk->sk_max_ack_backlog;
}

/*
 * Compute minimal free write space needed to queue new packets.
 */
static inline int sk_stream_min_wspace(const struct sock *sk)
{
    return sk->sk_wmem_queued >> 1;
}

static inline int sk_stream_wspace(const struct sock *sk)
{
    return sk->sk_sndbuf - sk->sk_wmem_queued;
}

extern void sk_stream_write_space(struct sock *sk);

static inline bool sk_stream_memory_free(const struct sock *sk)
{
    return sk->sk_wmem_queued < sk->sk_sndbuf;
}

/* OOB backlog add */
static inline void __sk_add_backlog(struct sock *sk, struct sk_buff *skb)
{
    /* dont let skb dst not refcounted, we are going to leave rcu lock */
    skb_dst_force(skb);

    if (!sk->sk_backlog.tail)
        sk->sk_backlog.head = skb;
    else
        sk->sk_backlog.tail->next = skb;

    sk->sk_backlog.tail = skb;
    skb->next = NULL;
}

/*
 * Take into account size of receive queue and backlog queue
 * Do not take into account this skb truesize,
 * to allow even a single big packet to come.
 */
static inline bool sk_rcvqueues_full(const struct sock *sk, const struct sk_buff *skb,
                     unsigned int limit)
{
    unsigned int qsize = sk->sk_backlog.len + atomic_read(&sk->sk_rmem_alloc);

    return qsize > limit;
}

/* The per-socket spinlock must be held here. */
static inline __must_check int sk_add_backlog(struct sock *sk, struct sk_buff *skb,
                          unsigned int limit)
{
    if (sk_rcvqueues_full(sk, skb, limit))
        return -ENOBUFS;

    __sk_add_backlog(sk, skb);
    sk->sk_backlog.len += skb->truesize;
    return 0;
}

extern int __sk_backlog_rcv(struct sock *sk, struct sk_buff *skb);

static inline int sk_backlog_rcv(struct sock *sk, struct sk_buff *skb)
{
    if (sk_memalloc_socks() && skb_pfmemalloc(skb))
        return __sk_backlog_rcv(sk, skb);

    return sk->sk_backlog_rcv(sk, skb);
}

static inline void sock_rps_record_flow(const struct sock *sk)
{
#ifdef CONFIG_RPS
    struct rps_sock_flow_table *sock_flow_table;

    rcu_read_lock();
    sock_flow_table = rcu_dereference(rps_sock_flow_table);
    rps_record_sock_flow(sock_flow_table, sk->sk_rxhash);
    rcu_read_unlock();
#endif
}

static inline void sock_rps_reset_flow(const struct sock *sk)
{
#ifdef CONFIG_RPS
    struct rps_sock_flow_table *sock_flow_table;

    rcu_read_lock();
    sock_flow_table = rcu_dereference(rps_sock_flow_table);
    rps_reset_sock_flow(sock_flow_table, sk->sk_rxhash);
    rcu_read_unlock();
#endif
}

static inline void sock_rps_save_rxhash(struct sock *sk,
                    const struct sk_buff *skb)
{
#ifdef CONFIG_RPS
    if (unlikely(sk->sk_rxhash != skb->rxhash)) {
        sock_rps_reset_flow(sk);
        sk->sk_rxhash = skb->rxhash;
    }
#endif
}

static inline void sock_rps_reset_rxhash(struct sock *sk)
{
#ifdef CONFIG_RPS
    sock_rps_reset_flow(sk);
    sk->sk_rxhash = 0;
#endif
}

#define sk_wait_event(__sk, __timeo, __condition)           \
    ({  int __rc;                       \
        release_sock(__sk);                 \
        __rc = __condition;                 \
        if (!__rc) {                        \
            *(__timeo) = schedule_timeout(*(__timeo));  \
        }                           \
        lock_sock(__sk);                    \
        __rc = __condition;                 \
        __rc;                           \
    })

extern int sk_stream_wait_connect(struct sock *sk, long *timeo_p);
extern int sk_stream_wait_memory(struct sock *sk, long *timeo_p);
extern void sk_stream_wait_close(struct sock *sk, long timeo_p);
extern int sk_stream_error(struct sock *sk, int flags, int err);
extern void sk_stream_kill_queues(struct sock *sk);
extern void sk_set_memalloc(struct sock *sk);
extern void sk_clear_memalloc(struct sock *sk);

extern int sk_wait_data(struct sock *sk, long *timeo);

struct request_sock_ops;
struct timewait_sock_ops;
struct inet_hashinfo;
struct raw_hashinfo;
struct module;

/* Networking protocol blocks we attach to sockets.
 * socket layer -> transport layer interface
 * transport -> network interface is defined by struct inet_proto
 */
struct proto {
    void            (*close)(struct sock *sk,
                    long timeout);
    int         (*connect)(struct sock *sk,
                    struct sockaddr *uaddr,
                    int addr_len);
    int         (*disconnect)(struct sock *sk, int flags);

    struct sock *       (*accept)(struct sock *sk, int flags, int *err);

    int         (*ioctl)(struct sock *sk, int cmd,
                     unsigned long arg);
    int         (*init)(struct sock *sk);
    void            (*destroy)(struct sock *sk);
    void            (*shutdown)(struct sock *sk, int how);
    int         (*setsockopt)(struct sock *sk, int level,
                    int optname, char __user *optval,
                    unsigned int optlen);
    int         (*getsockopt)(struct sock *sk, int level,
                    int optname, char __user *optval,
                    int __user *option);
#ifdef CONFIG_COMPAT
    int         (*compat_setsockopt)(struct sock *sk,
                    int level,
                    int optname, char __user *optval,
                    unsigned int optlen);
    int         (*compat_getsockopt)(struct sock *sk,
                    int level,
                    int optname, char __user *optval,
                    int __user *option);
    int         (*compat_ioctl)(struct sock *sk,
                    unsigned int cmd, unsigned long arg);
#endif
    int         (*sendmsg)(struct kiocb *iocb, struct sock *sk,
                       struct msghdr *msg, size_t len);
    int         (*recvmsg)(struct kiocb *iocb, struct sock *sk,
                       struct msghdr *msg,
                       size_t len, int noblock, int flags,
                       int *addr_len);
    int         (*sendpage)(struct sock *sk, struct page *page,
                    int offset, size_t size, int flags);
    int         (*bind)(struct sock *sk,
                    struct sockaddr *uaddr, int addr_len);

    int         (*backlog_rcv) (struct sock *sk,
                        struct sk_buff *skb);

    void        (*release_cb)(struct sock *sk);
    void        (*mtu_reduced)(struct sock *sk);

    /* Keeping track of sk's, looking them up, and port selection methods. */
    void            (*hash)(struct sock *sk);
    void            (*unhash)(struct sock *sk);
    void            (*rehash)(struct sock *sk);
    int         (*get_port)(struct sock *sk, unsigned short snum);
    void            (*clear_sk)(struct sock *sk, int size);

    /* Keeping track of sockets in use */
#ifdef CONFIG_PROC_FS
    unsigned int        inuse_idx;
#endif

    /* Memory pressure */
    void            (*enter_memory_pressure)(struct sock *sk);
    atomic_long_t       *memory_allocated;  /* Current allocated memory. */
    struct percpu_counter   *sockets_allocated; /* Current number of sockets. */
    /*
     * Pressure flag: try to collapse.
     * Technical note: it is used by multiple contexts non atomically.
     * All the __sk_mem_schedule() is of this nature: accounting
     * is strict, actions are advisory and have some latency.
     */
    int         *memory_pressure;
    long            *sysctl_mem;
    int         *sysctl_wmem;
    int         *sysctl_rmem;
    int         max_header;
    bool            no_autobind;

    struct kmem_cache   *slab;
    unsigned int        obj_size;
    int         slab_flags;

    struct percpu_counter   *orphan_count;

    struct request_sock_ops *rsk_prot;
    struct timewait_sock_ops *twsk_prot;

    union {
        struct inet_hashinfo    *hashinfo;
        struct udp_table    *udp_table;
        struct raw_hashinfo *raw_hash;
    } h;

    struct module       *owner;

    char            name[32];

    struct list_head    node;
#ifdef SOCK_REFCNT_DEBUG
    atomic_t        socks;
#endif
#ifdef CONFIG_MEMCG_KMEM
    /*
     * cgroup specific init/deinit functions. Called once for all
     * protocols that implement it, from cgroups populate function.
     * This function has to setup any files the protocol want to
     * appear in the kmem cgroup filesystem.
     */
    int         (*init_cgroup)(struct mem_cgroup *memcg,
                           struct cgroup_subsys *ss);
    void            (*destroy_cgroup)(struct mem_cgroup *memcg);
    struct cg_proto     *(*proto_cgroup)(struct mem_cgroup *memcg);
#endif
};

/*
 * Bits in struct cg_proto.flags
 */
enum cg_proto_flags {
    /* Currently active and new sockets should be assigned to cgroups */
    MEMCG_SOCK_ACTIVE,
    /* It was ever activated; we must disarm static keys on destruction */
    MEMCG_SOCK_ACTIVATED,
};

struct cg_proto {
    void            (*enter_memory_pressure)(struct sock *sk);
    struct res_counter  *memory_allocated;  /* Current allocated memory. */
    struct percpu_counter   *sockets_allocated; /* Current number of sockets. */
    int         *memory_pressure;
    long            *sysctl_mem;
    unsigned long       flags;
    /*
     * memcg field is used to find which memcg we belong directly
     * Each memcg struct can hold more than one cg_proto, so container_of
     * won't really cut.
     *
     * The elegant solution would be having an inverse function to
     * proto_cgroup in struct proto, but that means polluting the structure
     * for everybody, instead of just for memcg users.
     */
    struct mem_cgroup   *memcg;
};

extern int proto_register(struct proto *prot, int alloc_slab);
extern void proto_unregister(struct proto *prot);

static inline bool memcg_proto_active(struct cg_proto *cg_proto)
{
    return test_bit(MEMCG_SOCK_ACTIVE, &cg_proto->flags);
}

static inline bool memcg_proto_activated(struct cg_proto *cg_proto)
{
    return test_bit(MEMCG_SOCK_ACTIVATED, &cg_proto->flags);
}

#ifdef SOCK_REFCNT_DEBUG
static inline void sk_refcnt_debug_inc(struct sock *sk)
{
    atomic_inc(&sk->sk_prot->socks);
}

static inline void sk_refcnt_debug_dec(struct sock *sk)
{
    atomic_dec(&sk->sk_prot->socks);
    printk(KERN_DEBUG "%s socket %p released, %d are still alive\n",
           sk->sk_prot->name, sk, atomic_read(&sk->sk_prot->socks));
}

inline void sk_refcnt_debug_release(const struct sock *sk)
{
    if (atomic_read(&sk->sk_refcnt) != 1)
        printk(KERN_DEBUG "Destruction of the %s socket %p delayed, refcnt=%d\n",
               sk->sk_prot->name, sk, atomic_read(&sk->sk_refcnt));
}
#else /* SOCK_REFCNT_DEBUG */
#define sk_refcnt_debug_inc(sk) do { } while (0)
#define sk_refcnt_debug_dec(sk) do { } while (0)
#define sk_refcnt_debug_release(sk) do { } while (0)
#endif /* SOCK_REFCNT_DEBUG */

#if defined(CONFIG_MEMCG_KMEM) && defined(CONFIG_NET)
extern struct static_key memcg_socket_limit_enabled;
static inline struct cg_proto *parent_cg_proto(struct proto *proto,
                           struct cg_proto *cg_proto)
{
    return proto->proto_cgroup(parent_mem_cgroup(cg_proto->memcg));
}
#define mem_cgroup_sockets_enabled static_key_false(&memcg_socket_limit_enabled)
#else
#define mem_cgroup_sockets_enabled 0
static inline struct cg_proto *parent_cg_proto(struct proto *proto,
                           struct cg_proto *cg_proto)
{
    return NULL;
}
#endif


static inline bool sk_has_memory_pressure(const struct sock *sk)
{
    return sk->sk_prot->memory_pressure != NULL;
}

static inline bool sk_under_memory_pressure(const struct sock *sk)
{
    if (!sk->sk_prot->memory_pressure)
        return false;

    if (mem_cgroup_sockets_enabled && sk->sk_cgrp)
        return !!*sk->sk_cgrp->memory_pressure;

    return !!*sk->sk_prot->memory_pressure;
}

static inline void sk_leave_memory_pressure(struct sock *sk)
{
    int *memory_pressure = sk->sk_prot->memory_pressure;

    if (!memory_pressure)
        return;

    if (*memory_pressure)
        *memory_pressure = 0;

    if (mem_cgroup_sockets_enabled && sk->sk_cgrp) {
        struct cg_proto *cg_proto = sk->sk_cgrp;
        struct proto *prot = sk->sk_prot;

        for (; cg_proto; cg_proto = parent_cg_proto(prot, cg_proto))
            if (*cg_proto->memory_pressure)
                *cg_proto->memory_pressure = 0;
    }

}

static inline void sk_enter_memory_pressure(struct sock *sk)
{
    if (!sk->sk_prot->enter_memory_pressure)
        return;

    if (mem_cgroup_sockets_enabled && sk->sk_cgrp) {
        struct cg_proto *cg_proto = sk->sk_cgrp;
        struct proto *prot = sk->sk_prot;

        for (; cg_proto; cg_proto = parent_cg_proto(prot, cg_proto))
            cg_proto->enter_memory_pressure(sk);
    }

    sk->sk_prot->enter_memory_pressure(sk);
}

static inline long sk_prot_mem_limits(const struct sock *sk, int index)
{
    long *prot = sk->sk_prot->sysctl_mem;
    if (mem_cgroup_sockets_enabled && sk->sk_cgrp)
        prot = sk->sk_cgrp->sysctl_mem;
    return prot[index];
}

static inline void memcg_memory_allocated_add(struct cg_proto *prot,
                          unsigned long amt,
                          int *parent_status)
{
    struct res_counter *fail;
    int ret;

    ret = res_counter_charge_nofail(prot->memory_allocated,
                    amt << PAGE_SHIFT, &fail);
    if (ret < 0)
        *parent_status = OVER_LIMIT;
}

static inline void memcg_memory_allocated_sub(struct cg_proto *prot,
                          unsigned long amt)
{
    res_counter_uncharge(prot->memory_allocated, amt << PAGE_SHIFT);
}

static inline u64 memcg_memory_allocated_read(struct cg_proto *prot)
{
    u64 ret;
    ret = res_counter_read_u64(prot->memory_allocated, RES_USAGE);
    return ret >> PAGE_SHIFT;
}

static inline long
sk_memory_allocated(const struct sock *sk)
{
    struct proto *prot = sk->sk_prot;
    if (mem_cgroup_sockets_enabled && sk->sk_cgrp)
        return memcg_memory_allocated_read(sk->sk_cgrp);

    return atomic_long_read(prot->memory_allocated);
}

static inline long
sk_memory_allocated_add(struct sock *sk, int amt, int *parent_status)
{
    struct proto *prot = sk->sk_prot;

    if (mem_cgroup_sockets_enabled && sk->sk_cgrp) {
        memcg_memory_allocated_add(sk->sk_cgrp, amt, parent_status);
        /* update the root cgroup regardless */
        atomic_long_add_return(amt, prot->memory_allocated);
        return memcg_memory_allocated_read(sk->sk_cgrp);
    }

    return atomic_long_add_return(amt, prot->memory_allocated);
}

static inline void
sk_memory_allocated_sub(struct sock *sk, int amt)
{
    struct proto *prot = sk->sk_prot;

    if (mem_cgroup_sockets_enabled && sk->sk_cgrp)
        memcg_memory_allocated_sub(sk->sk_cgrp, amt);

    atomic_long_sub(amt, prot->memory_allocated);
}

static inline void sk_sockets_allocated_dec(struct sock *sk)
{
    struct proto *prot = sk->sk_prot;

    if (mem_cgroup_sockets_enabled && sk->sk_cgrp) {
        struct cg_proto *cg_proto = sk->sk_cgrp;

        for (; cg_proto; cg_proto = parent_cg_proto(prot, cg_proto))
            percpu_counter_dec(cg_proto->sockets_allocated);
    }

    percpu_counter_dec(prot->sockets_allocated);
}

static inline void sk_sockets_allocated_inc(struct sock *sk)
{
    struct proto *prot = sk->sk_prot;

    if (mem_cgroup_sockets_enabled && sk->sk_cgrp) {
        struct cg_proto *cg_proto = sk->sk_cgrp;

        for (; cg_proto; cg_proto = parent_cg_proto(prot, cg_proto))
            percpu_counter_inc(cg_proto->sockets_allocated);
    }

    percpu_counter_inc(prot->sockets_allocated);
}

static inline int
sk_sockets_allocated_read_positive(struct sock *sk)
{
    struct proto *prot = sk->sk_prot;

    if (mem_cgroup_sockets_enabled && sk->sk_cgrp)
        return percpu_counter_read_positive(sk->sk_cgrp->sockets_allocated);

    return percpu_counter_read_positive(prot->sockets_allocated);
}

static inline int
proto_sockets_allocated_sum_positive(struct proto *prot)
{
    return percpu_counter_sum_positive(prot->sockets_allocated);
}

static inline long
proto_memory_allocated(struct proto *prot)
{
    return atomic_long_read(prot->memory_allocated);
}

static inline bool
proto_memory_pressure(struct proto *prot)
{
    if (!prot->memory_pressure)
        return false;
    return !!*prot->memory_pressure;
}


#ifdef CONFIG_PROC_FS
/* Called with local bh disabled */
extern void sock_prot_inuse_add(struct net *net, struct proto *prot, int inc);
extern int sock_prot_inuse_get(struct net *net, struct proto *proto);
#else
static inline void sock_prot_inuse_add(struct net *net, struct proto *prot,
        int inc)
{
}
#endif


/* With per-bucket locks this operation is not-atomic, so that
 * this version is not worse.
 */
static inline void __sk_prot_rehash(struct sock *sk)
{
    sk->sk_prot->unhash(sk);
    sk->sk_prot->hash(sk);
}

void sk_prot_clear_portaddr_nulls(struct sock *sk, int size);

/* About 10 seconds */
#define SOCK_DESTROY_TIME (10*HZ)

/* Sockets 0-1023 can't be bound to unless you are superuser */
#define PROT_SOCK   1024

#define SHUTDOWN_MASK   3
#define RCV_SHUTDOWN    1
#define SEND_SHUTDOWN   2

#define SOCK_SNDBUF_LOCK    1
#define SOCK_RCVBUF_LOCK    2
#define SOCK_BINDADDR_LOCK  4
#define SOCK_BINDPORT_LOCK  8

/* sock_iocb: used to kick off async processing of socket ios */
struct sock_iocb {
    struct list_head    list;

    int         flags;
    int         size;
    struct socket       *sock;
    struct sock     *sk;
    struct scm_cookie   *scm;
    struct msghdr       *msg, async_msg;
    struct kiocb        *kiocb;
};

static inline struct sock_iocb *kiocb_to_siocb(struct kiocb *iocb)
{
    return (struct sock_iocb *)iocb->private;
}

static inline struct kiocb *siocb_to_kiocb(struct sock_iocb *si)
{
    return si->kiocb;
}

struct socket_alloc {
    struct socket socket;
    struct inode vfs_inode;
};

static inline struct socket *SOCKET_I(struct inode *inode)
{
    return &container_of(inode, struct socket_alloc, vfs_inode)->socket;
}

static inline struct inode *SOCK_INODE(struct socket *socket)
{
    return &container_of(socket, struct socket_alloc, socket)->vfs_inode;
}

/*
 * Functions for memory accounting
 */
extern int __sk_mem_schedule(struct sock *sk, int size, int kind);
extern void __sk_mem_reclaim(struct sock *sk);

#define SK_MEM_QUANTUM ((int)PAGE_SIZE)
#define SK_MEM_QUANTUM_SHIFT ilog2(SK_MEM_QUANTUM)
#define SK_MEM_SEND 0
#define SK_MEM_RECV 1

static inline int sk_mem_pages(int amt)
{
    return (amt + SK_MEM_QUANTUM - 1) >> SK_MEM_QUANTUM_SHIFT;
}

static inline bool sk_has_account(struct sock *sk)
{
    /* return true if protocol supports memory accounting */
    return !!sk->sk_prot->memory_allocated;
}

static inline bool sk_wmem_schedule(struct sock *sk, int size)
{
    if (!sk_has_account(sk))
        return true;
    return size <= sk->sk_forward_alloc ||
        __sk_mem_schedule(sk, size, SK_MEM_SEND);
}

static inline bool
sk_rmem_schedule(struct sock *sk, struct sk_buff *skb, int size)
{
    if (!sk_has_account(sk))
        return true;
    return size<= sk->sk_forward_alloc ||
        __sk_mem_schedule(sk, size, SK_MEM_RECV) ||
        skb_pfmemalloc(skb);
}

static inline void sk_mem_reclaim(struct sock *sk)
{
    if (!sk_has_account(sk))
        return;
    if (sk->sk_forward_alloc >= SK_MEM_QUANTUM)
        __sk_mem_reclaim(sk);
}

static inline void sk_mem_reclaim_partial(struct sock *sk)
{
    if (!sk_has_account(sk))
        return;
    if (sk->sk_forward_alloc > SK_MEM_QUANTUM)
        __sk_mem_reclaim(sk);
}

static inline void sk_mem_charge(struct sock *sk, int size)
{
    if (!sk_has_account(sk))
        return;
    sk->sk_forward_alloc -= size;
}

static inline void sk_mem_uncharge(struct sock *sk, int size)
{
    if (!sk_has_account(sk))
        return;
    sk->sk_forward_alloc += size;
}

static inline void sk_wmem_free_skb(struct sock *sk, struct sk_buff *skb)
{
    sock_set_flag(sk, SOCK_QUEUE_SHRUNK);
    sk->sk_wmem_queued -= skb->truesize;
    sk_mem_uncharge(sk, skb->truesize);
    __kfree_skb(skb);
}

/* Used by processes to "lock" a socket state, so that
 * interrupts and bottom half handlers won't change it
 * from under us. It essentially blocks any incoming
 * packets, so that we won't get any new data or any
 * packets that change the state of the socket.
 *
 * While locked, BH processing will add new packets to
 * the backlog queue.  This queue is processed by the
 * owner of the socket lock right before it is released.
 *
 * Since ~2.3.5 it is also exclusive sleep lock serializing
 * accesses from user process context.
 */
#define sock_owned_by_user(sk)  ((sk)->sk_lock.owned)

/*
 * Macro so as to not evaluate some arguments when
 * lockdep is not enabled.
 *
 * Mark both the sk_lock and the sk_lock.slock as a
 * per-address-family lock class.
 */
#define sock_lock_init_class_and_name(sk, sname, skey, name, key)   \
do {                                    \
    sk->sk_lock.owned = 0;                      \
    init_waitqueue_head(&sk->sk_lock.wq);               \
    spin_lock_init(&(sk)->sk_lock.slock);               \
    debug_check_no_locks_freed((void *)&(sk)->sk_lock,      \
            sizeof((sk)->sk_lock));             \
    lockdep_set_class_and_name(&(sk)->sk_lock.slock,        \
                (skey), (sname));               \
    lockdep_init_map(&(sk)->sk_lock.dep_map, (name), (key), 0); \
} while (0)

extern void lock_sock_nested(struct sock *sk, int subclass);

static inline void lock_sock(struct sock *sk)
{
    lock_sock_nested(sk, 0);
}

extern void release_sock(struct sock *sk);

/* BH context may only use the following locking interface. */
#define bh_lock_sock(__sk)  spin_lock(&((__sk)->sk_lock.slock))
#define bh_lock_sock_nested(__sk) \
                spin_lock_nested(&((__sk)->sk_lock.slock), \
                SINGLE_DEPTH_NESTING)
#define bh_unlock_sock(__sk)    spin_unlock(&((__sk)->sk_lock.slock))

extern bool lock_sock_fast(struct sock *sk);
static inline void unlock_sock_fast(struct sock *sk, bool slow)
{
    if (slow)
        release_sock(sk);
    else
        spin_unlock_bh(&sk->sk_lock.slock);
}


extern struct sock      *sk_alloc(struct net *net, int family,
                      gfp_t priority,
                      struct proto *prot);
extern void         sk_free(struct sock *sk);
extern void         sk_release_kernel(struct sock *sk);
extern struct sock      *sk_clone_lock(const struct sock *sk,
                           const gfp_t priority);

extern struct sk_buff       *sock_wmalloc(struct sock *sk,
                          unsigned long size, int force,
                          gfp_t priority);
extern struct sk_buff       *sock_rmalloc(struct sock *sk,
                          unsigned long size, int force,
                          gfp_t priority);
extern void         sock_wfree(struct sk_buff *skb);
extern void         sock_rfree(struct sk_buff *skb);
extern void         sock_edemux(struct sk_buff *skb);

extern int          sock_setsockopt(struct socket *sock, int level,
                        int op, char __user *optval,
                        unsigned int optlen);

extern int          sock_getsockopt(struct socket *sock, int level,
                        int op, char __user *optval,
                        int __user *optlen);
extern struct sk_buff       *sock_alloc_send_skb(struct sock *sk,
                             unsigned long size,
                             int noblock,
                             int *errcode);
extern struct sk_buff       *sock_alloc_send_pskb(struct sock *sk,
                              unsigned long header_len,
                              unsigned long data_len,
                              int noblock,
                              int *errcode);
extern void *sock_kmalloc(struct sock *sk, int size,
              gfp_t priority);
extern void sock_kfree_s(struct sock *sk, void *mem, int size);
extern void sk_send_sigurg(struct sock *sk);

/*
 * Functions to fill in entries in struct proto_ops when a protocol
 * does not implement a particular function.
 */
extern int                      sock_no_bind(struct socket *,
                         struct sockaddr *, int);
extern int                      sock_no_connect(struct socket *,
                        struct sockaddr *, int, int);
extern int                      sock_no_socketpair(struct socket *,
                           struct socket *);
extern int                      sock_no_accept(struct socket *,
                           struct socket *, int);
extern int                      sock_no_getname(struct socket *,
                        struct sockaddr *, int *, int);
extern unsigned int             sock_no_poll(struct file *, struct socket *,
                         struct poll_table_struct *);
extern int                      sock_no_ioctl(struct socket *, unsigned int,
                          unsigned long);
extern int          sock_no_listen(struct socket *, int);
extern int                      sock_no_shutdown(struct socket *, int);
extern int          sock_no_getsockopt(struct socket *, int , int,
                           char __user *, int __user *);
extern int          sock_no_setsockopt(struct socket *, int, int,
                           char __user *, unsigned int);
extern int                      sock_no_sendmsg(struct kiocb *, struct socket *,
                        struct msghdr *, size_t);
extern int                      sock_no_recvmsg(struct kiocb *, struct socket *,
                        struct msghdr *, size_t, int);
extern int          sock_no_mmap(struct file *file,
                         struct socket *sock,
                         struct vm_area_struct *vma);
extern ssize_t          sock_no_sendpage(struct socket *sock,
                        struct page *page,
                        int offset, size_t size,
                        int flags);

/*
 * Functions to fill in entries in struct proto_ops when a protocol
 * uses the inet style.
 */
extern int sock_common_getsockopt(struct socket *sock, int level, int optname,
                  char __user *optval, int __user *optlen);
extern int sock_common_recvmsg(struct kiocb *iocb, struct socket *sock,
                   struct msghdr *msg, size_t size, int flags);
extern int sock_common_setsockopt(struct socket *sock, int level, int optname,
                  char __user *optval, unsigned int optlen);
extern int compat_sock_common_getsockopt(struct socket *sock, int level,
        int optname, char __user *optval, int __user *optlen);
extern int compat_sock_common_setsockopt(struct socket *sock, int level,
        int optname, char __user *optval, unsigned int optlen);

extern void sk_common_release(struct sock *sk);

/*
 *  Default socket callbacks and setup code
 */

/* Initialise core socket variables */
extern void sock_init_data(struct socket *sock, struct sock *sk);

extern void sk_filter_release_rcu(struct rcu_head *rcu);

static inline void sk_filter_release(struct sk_filter *fp)
{
    if (atomic_dec_and_test(&fp->refcnt))
        call_rcu(&fp->rcu, sk_filter_release_rcu);
}

static inline void sk_filter_uncharge(struct sock *sk, struct sk_filter *fp)
{
    unsigned int size = sk_filter_len(fp);

    atomic_sub(size, &sk->sk_omem_alloc);
    sk_filter_release(fp);
}

static inline void sk_filter_charge(struct sock *sk, struct sk_filter *fp)
{
    atomic_inc(&fp->refcnt);
    atomic_add(sk_filter_len(fp), &sk->sk_omem_alloc);
}

/*
 * Socket reference counting postulates.
 *
 * * Each user of socket SHOULD hold a reference count.
 * * Each access point to socket (an hash table bucket, reference from a list,
 *   running timer, skb in flight MUST hold a reference count.
 * * When reference count hits 0, it means it will never increase back.
 * * When reference count hits 0, it means that no references from
 *   outside exist to this socket and current process on current CPU
 *   is last user and may/should destroy this socket.
 * * sk_free is called from any context: process, BH, IRQ. When
 *   it is called, socket has no references from outside -> sk_free
 *   may release descendant resources allocated by the socket, but
 *   to the time when it is called, socket is NOT referenced by any
 *   hash tables, lists etc.
 * * Packets, delivered from outside (from network or from another process)
 *   and enqueued on receive/error queues SHOULD NOT grab reference count,
 *   when they sit in queue. Otherwise, packets will leak to hole, when
 *   socket is looked up by one cpu and unhasing is made by another CPU.
 *   It is true for udp/raw, netlink (leak to receive and error queues), tcp
 *   (leak to backlog). Packet socket does all the processing inside
 *   BR_NETPROTO_LOCK, so that it has not this race condition. UNIX sockets
 *   use separate SMP lock, so that they are prone too.
 */

/* Ungrab socket and destroy it, if it was the last reference. */
static inline void sock_put(struct sock *sk)
{
    if (atomic_dec_and_test(&sk->sk_refcnt))
        sk_free(sk);
}

extern int sk_receive_skb(struct sock *sk, struct sk_buff *skb,
              const int nested);

static inline void sk_tx_queue_set(struct sock *sk, int tx_queue)
{
    sk->sk_tx_queue_mapping = tx_queue;
}

static inline void sk_tx_queue_clear(struct sock *sk)
{
    sk->sk_tx_queue_mapping = -1;
}

static inline int sk_tx_queue_get(const struct sock *sk)
{
    return sk ? sk->sk_tx_queue_mapping : -1;
}

static inline void sk_set_socket(struct sock *sk, struct socket *sock)
{
    sk_tx_queue_clear(sk);
    sk->sk_socket = sock;
}

static inline wait_queue_head_t *sk_sleep(struct sock *sk)
{
    BUILD_BUG_ON(offsetof(struct socket_wq, wait) != 0);
    return &rcu_dereference_raw(sk->sk_wq)->wait;
}
/* Detach socket from process context.
 * Announce socket dead, detach it from wait queue and inode.
 * Note that parent inode held reference count on this struct sock,
 * we do not release it in this function, because protocol
 * probably wants some additional cleanups or even continuing
 * to work with this socket (TCP).
 */
static inline void sock_orphan(struct sock *sk)
{
    write_lock_bh(&sk->sk_callback_lock);
    sock_set_flag(sk, SOCK_DEAD);
    sk_set_socket(sk, NULL);
    sk->sk_wq  = NULL;
    write_unlock_bh(&sk->sk_callback_lock);
}

static inline void sock_graft(struct sock *sk, struct socket *parent)
{
    write_lock_bh(&sk->sk_callback_lock);
    sk->sk_wq = parent->wq;
    parent->sk = sk;
    sk_set_socket(sk, parent);
    security_sock_graft(sk, parent);
    write_unlock_bh(&sk->sk_callback_lock);
}

extern kuid_t sock_i_uid(struct sock *sk);
extern unsigned long sock_i_ino(struct sock *sk);

static inline struct dst_entry *
__sk_dst_get(struct sock *sk)
{
    return rcu_dereference_check(sk->sk_dst_cache, sock_owned_by_user(sk) ||
                               lockdep_is_held(&sk->sk_lock.slock));
}

static inline struct dst_entry *
sk_dst_get(struct sock *sk)
{
    struct dst_entry *dst;

    rcu_read_lock();
    dst = rcu_dereference(sk->sk_dst_cache);
    if (dst)
        dst_hold(dst);
    rcu_read_unlock();
    return dst;
}

extern void sk_reset_txq(struct sock *sk);

static inline void dst_negative_advice(struct sock *sk)
{
    struct dst_entry *ndst, *dst = __sk_dst_get(sk);

    if (dst && dst->ops->negative_advice) {
        ndst = dst->ops->negative_advice(dst);

        if (ndst != dst) {
            rcu_assign_pointer(sk->sk_dst_cache, ndst);
            sk_reset_txq(sk);
        }
    }
}

static inline void
__sk_dst_set(struct sock *sk, struct dst_entry *dst)
{
    struct dst_entry *old_dst;

    sk_tx_queue_clear(sk);
    /*
     * This can be called while sk is owned by the caller only,
     * with no state that can be checked in a rcu_dereference_check() cond
     */
    old_dst = rcu_dereference_raw(sk->sk_dst_cache);
    rcu_assign_pointer(sk->sk_dst_cache, dst);
    dst_release(old_dst);
}

static inline void
sk_dst_set(struct sock *sk, struct dst_entry *dst)
{
    spin_lock(&sk->sk_dst_lock);
    __sk_dst_set(sk, dst);
    spin_unlock(&sk->sk_dst_lock);
}

static inline void
__sk_dst_reset(struct sock *sk)
{
    __sk_dst_set(sk, NULL);
}

static inline void
sk_dst_reset(struct sock *sk)
{
    spin_lock(&sk->sk_dst_lock);
    __sk_dst_reset(sk);
    spin_unlock(&sk->sk_dst_lock);
}

extern struct dst_entry *__sk_dst_check(struct sock *sk, u32 cookie);

extern struct dst_entry *sk_dst_check(struct sock *sk, u32 cookie);

static inline bool sk_can_gso(const struct sock *sk)
{
    return net_gso_ok(sk->sk_route_caps, sk->sk_gso_type);
}

extern void sk_setup_caps(struct sock *sk, struct dst_entry *dst);

static inline void sk_nocaps_add(struct sock *sk, netdev_features_t flags)
{
    sk->sk_route_nocaps |= flags;
    sk->sk_route_caps &= ~flags;
}

static inline int skb_do_copy_data_nocache(struct sock *sk, struct sk_buff *skb,
                       char __user *from, char *to,
                       int copy, int offset)
{
    if (skb->ip_summed == CHECKSUM_NONE) {
        int err = 0;
        __wsum csum = csum_and_copy_from_user(from, to, copy, 0, &err);
        if (err)
            return err;
        skb->csum = csum_block_add(skb->csum, csum, offset);
    } else if (sk->sk_route_caps & NETIF_F_NOCACHE_COPY) {
        if (!access_ok(VERIFY_READ, from, copy) ||
            __copy_from_user_nocache(to, from, copy))
            return -EFAULT;
    } else if (copy_from_user(to, from, copy))
        return -EFAULT;

    return 0;
}

static inline int skb_add_data_nocache(struct sock *sk, struct sk_buff *skb,
                       char __user *from, int copy)
{
    int err, offset = skb->len;

    err = skb_do_copy_data_nocache(sk, skb, from, skb_put(skb, copy),
                       copy, offset);
    if (err)
        __skb_trim(skb, offset);

    return err;
}

static inline int skb_copy_to_page_nocache(struct sock *sk, char __user *from,
                       struct sk_buff *skb,
                       struct page *page,
                       int off, int copy)
{
    int err;

    err = skb_do_copy_data_nocache(sk, skb, from, page_address(page) + off,
                       copy, skb->len);
    if (err)
        return err;

    skb->len         += copy;
    skb->data_len        += copy;
    skb->truesize        += copy;
    sk->sk_wmem_queued   += copy;
    sk_mem_charge(sk, copy);
    return 0;
}

static inline int skb_copy_to_page(struct sock *sk, char __user *from,
                   struct sk_buff *skb, struct page *page,
                   int off, int copy)
{
    if (skb->ip_summed == CHECKSUM_NONE) {
        int err = 0;
        __wsum csum = csum_and_copy_from_user(from,
                             page_address(page) + off,
                                copy, 0, &err);
        if (err)
            return err;
        skb->csum = csum_block_add(skb->csum, csum, skb->len);
    } else if (copy_from_user(page_address(page) + off, from, copy))
        return -EFAULT;

    skb->len         += copy;
    skb->data_len        += copy;
    skb->truesize        += copy;
    sk->sk_wmem_queued   += copy;
    sk_mem_charge(sk, copy);
    return 0;
}

static inline int sk_wmem_alloc_get(const struct sock *sk)
{
    return atomic_read(&sk->sk_wmem_alloc) - 1;
}

static inline int sk_rmem_alloc_get(const struct sock *sk)
{
    return atomic_read(&sk->sk_rmem_alloc);
}

static inline bool sk_has_allocations(const struct sock *sk)
{
    return sk_wmem_alloc_get(sk) || sk_rmem_alloc_get(sk);
}

static inline bool wq_has_sleeper(struct socket_wq *wq)
{
    /* We need to be sure we are in sync with the
     * add_wait_queue modifications to the wait queue.
     *
     * This memory barrier is paired in the sock_poll_wait.
     */
    smp_mb();
    return wq && waitqueue_active(&wq->wait);
}

static inline void sock_poll_wait(struct file *filp,
        wait_queue_head_t *wait_address, poll_table *p)
{
    if (!poll_does_not_wait(p) && wait_address) {
        poll_wait(filp, wait_address, p);
        /* We need to be sure we are in sync with the
         * socket flags modification.
         *
         * This memory barrier is paired in the wq_has_sleeper.
         */
        smp_mb();
    }
}

/*
 *  Queue a received datagram if it will fit. Stream and sequenced
 *  protocols can't normally use this as they need to fit buffers in
 *  and play with them.
 *
 *  Inlined as it's very short and called for pretty much every
 *  packet ever received.
 */

static inline void skb_set_owner_w(struct sk_buff *skb, struct sock *sk)
{
    skb_orphan(skb);
    skb->sk = sk;
    skb->destructor = sock_wfree;
    /*
     * We used to take a refcount on sk, but following operation
     * is enough to guarantee sk_free() wont free this sock until
     * all in-flight packets are completed
     */
    atomic_add(skb->truesize, &sk->sk_wmem_alloc);
}

static inline void skb_set_owner_r(struct sk_buff *skb, struct sock *sk)
{
    skb_orphan(skb);
    skb->sk = sk;
    skb->destructor = sock_rfree;
    atomic_add(skb->truesize, &sk->sk_rmem_alloc);
    sk_mem_charge(sk, skb->truesize);
}

extern void sk_reset_timer(struct sock *sk, struct timer_list *timer,
               unsigned long expires);

extern void sk_stop_timer(struct sock *sk, struct timer_list *timer);

extern int sock_queue_rcv_skb(struct sock *sk, struct sk_buff *skb);

extern int sock_queue_err_skb(struct sock *sk, struct sk_buff *skb);

/*
 *  Recover an error report and clear atomically
 */

static inline int sock_error(struct sock *sk)
{
    int err;
    if (likely(!sk->sk_err))
        return 0;
    err = xchg(&sk->sk_err, 0);
    return -err;
}

static inline unsigned long sock_wspace(struct sock *sk)
{
    int amt = 0;

    if (!(sk->sk_shutdown & SEND_SHUTDOWN)) {
        amt = sk->sk_sndbuf - atomic_read(&sk->sk_wmem_alloc);
        if (amt < 0)
            amt = 0;
    }
    return amt;
}

static inline void sk_wake_async(struct sock *sk, int how, int band)
{
    if (sock_flag(sk, SOCK_FASYNC))
        sock_wake_async(sk->sk_socket, how, band);
}

#define SOCK_MIN_SNDBUF 2048
/*
 * Since sk_rmem_alloc sums skb->truesize, even a small frame might need
 * sizeof(sk_buff) + MTU + padding, unless net driver perform copybreak
 */
#define SOCK_MIN_RCVBUF (2048 + sizeof(struct sk_buff))

static inline void sk_stream_moderate_sndbuf(struct sock *sk)
{
    if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK)) {
        sk->sk_sndbuf = min(sk->sk_sndbuf, sk->sk_wmem_queued >> 1);
        sk->sk_sndbuf = max(sk->sk_sndbuf, SOCK_MIN_SNDBUF);
    }
}

struct sk_buff *sk_stream_alloc_skb(struct sock *sk, int size, gfp_t gfp);

static inline struct page_frag *sk_page_frag(struct sock *sk)
{
    if (sk->sk_allocation & __GFP_WAIT)
        return &current->task_frag;

    return &sk->sk_frag;
}

extern bool sk_page_frag_refill(struct sock *sk, struct page_frag *pfrag);

/*
 *  Default write policy as shown to user space via poll/select/SIGIO
 */
static inline bool sock_writeable(const struct sock *sk)
{
    return atomic_read(&sk->sk_wmem_alloc) < (sk->sk_sndbuf >> 1);
}

static inline gfp_t gfp_any(void)
{
    return in_softirq() ? GFP_ATOMIC : GFP_KERNEL;
}

static inline long sock_rcvtimeo(const struct sock *sk, bool noblock)
{
    return noblock ? 0 : sk->sk_rcvtimeo;
}

static inline long sock_sndtimeo(const struct sock *sk, bool noblock)
{
    return noblock ? 0 : sk->sk_sndtimeo;
}

static inline int sock_rcvlowat(const struct sock *sk, int waitall, int len)
{
    return (waitall ? len : min_t(int, sk->sk_rcvlowat, len)) ? : 1;
}

/* Alas, with timeout socket operations are not restartable.
 * Compare this to poll().
 */
static inline int sock_intr_errno(long timeo)
{
    return timeo == MAX_SCHEDULE_TIMEOUT ? -ERESTARTSYS : -EINTR;
}

extern void __sock_recv_timestamp(struct msghdr *msg, struct sock *sk,
    struct sk_buff *skb);
extern void __sock_recv_wifi_status(struct msghdr *msg, struct sock *sk,
    struct sk_buff *skb);

static inline void
sock_recv_timestamp(struct msghdr *msg, struct sock *sk, struct sk_buff *skb)
{
    ktime_t kt = skb->tstamp;
    struct skb_shared_hwtstamps *hwtstamps = skb_hwtstamps(skb);

    /*
     * generate control messages if
     * - receive time stamping in software requested (SOCK_RCVTSTAMP
     *   or SOCK_TIMESTAMPING_RX_SOFTWARE)
     * - software time stamp available and wanted
     *   (SOCK_TIMESTAMPING_SOFTWARE)
     * - hardware time stamps available and wanted
     *   (SOCK_TIMESTAMPING_SYS_HARDWARE or
     *   SOCK_TIMESTAMPING_RAW_HARDWARE)
     */
    if (sock_flag(sk, SOCK_RCVTSTAMP) ||
        sock_flag(sk, SOCK_TIMESTAMPING_RX_SOFTWARE) ||
        (kt.tv64 && sock_flag(sk, SOCK_TIMESTAMPING_SOFTWARE)) ||
        (hwtstamps->hwtstamp.tv64 &&
         sock_flag(sk, SOCK_TIMESTAMPING_RAW_HARDWARE)) ||
        (hwtstamps->syststamp.tv64 &&
         sock_flag(sk, SOCK_TIMESTAMPING_SYS_HARDWARE)))
        __sock_recv_timestamp(msg, sk, skb);
    else
        sk->sk_stamp = kt;

    if (sock_flag(sk, SOCK_WIFI_STATUS) && skb->wifi_acked_valid)
        __sock_recv_wifi_status(msg, sk, skb);
}

extern void __sock_recv_ts_and_drops(struct msghdr *msg, struct sock *sk,
                     struct sk_buff *skb);

static inline void sock_recv_ts_and_drops(struct msghdr *msg, struct sock *sk,
                      struct sk_buff *skb)
{
#define FLAGS_TS_OR_DROPS ((1UL << SOCK_RXQ_OVFL)           | \
               (1UL << SOCK_RCVTSTAMP)          | \
               (1UL << SOCK_TIMESTAMPING_RX_SOFTWARE)   | \
               (1UL << SOCK_TIMESTAMPING_SOFTWARE)      | \
               (1UL << SOCK_TIMESTAMPING_RAW_HARDWARE)  | \
               (1UL << SOCK_TIMESTAMPING_SYS_HARDWARE))

    if (sk->sk_flags & FLAGS_TS_OR_DROPS)
        __sock_recv_ts_and_drops(msg, sk, skb);
    else
        sk->sk_stamp = skb->tstamp;
}

extern int sock_tx_timestamp(struct sock *sk, __u8 *tx_flags);

#ifdef CONFIG_NET_DMA
static inline void sk_eat_skb(struct sock *sk, struct sk_buff *skb, bool copied_early)
{
    __skb_unlink(skb, &sk->sk_receive_queue);
    if (!copied_early)
        __kfree_skb(skb);
    else
        __skb_queue_tail(&sk->sk_async_wait_queue, skb);
}
#else
static inline void sk_eat_skb(struct sock *sk, struct sk_buff *skb, bool copied_early)
{
    __skb_unlink(skb, &sk->sk_receive_queue);
    __kfree_skb(skb);
}
#endif

static inline
struct net *sock_net(const struct sock *sk)
{
    return read_pnet(&sk->sk_net);
}

static inline
void sock_net_set(struct sock *sk, struct net *net)
{
    write_pnet(&sk->sk_net, net);
}

/*
 * Kernel sockets, f.e. rtnl or icmp_socket, are a part of a namespace.
 * They should not hold a reference to a namespace in order to allow
 * to stop it.
 * Sockets after sk_change_net should be released using sk_release_kernel
 */
static inline void sk_change_net(struct sock *sk, struct net *net)
{
    put_net(sock_net(sk));
    sock_net_set(sk, hold_net(net));
}

static inline struct sock *skb_steal_sock(struct sk_buff *skb)
{
    if (skb->sk) {
        struct sock *sk = skb->sk;

        skb->destructor = NULL;
        skb->sk = NULL;
        return sk;
    }
    return NULL;
}

extern void sock_enable_timestamp(struct sock *sk, int flag);
extern int sock_get_timestamp(struct sock *, struct timeval __user *);
extern int sock_get_timestampns(struct sock *, struct timespec __user *);

/*
 *  Enable debug/info messages
 */
extern int net_msg_warn;
#define NETDEBUG(fmt, args...) \
    do { if (net_msg_warn) printk(fmt,##args); } while (0)

#define LIMIT_NETDEBUG(fmt, args...) \
    do { if (net_msg_warn && net_ratelimit()) printk(fmt,##args); } while(0)

extern __u32 sysctl_wmem_max;
extern __u32 sysctl_rmem_max;

extern int sysctl_optmem_max;

extern __u32 sysctl_wmem_default;
extern __u32 sysctl_rmem_default;

#endif  /* _SOCK_H */