net/ipv4/inet_hashtables.c - kernel/msm-4.9 - Gitiles

 /*
  * 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.
  *
  *		Generic INET transport hashtables
  *
  * Authors:	Lotsa people, from code originally in tcp
  *
  *	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.
  */

 #include <linux/module.h>
 #include <linux/random.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
 #include <linux/wait.h>

 #include <net/inet_connection_sock.h>
 #include <net/inet_hashtables.h>
 #include <net/ip.h>

 /*
  * Allocate and initialize a new local port bind bucket.
  * The bindhash mutex for snum's hash chain must be held here.
  */
 struct inet_bind_bucket *inet_bind_bucket_create(struct kmem_cache *cachep,
 						 struct net *net,
 						 struct inet_bind_hashbucket *head,
 						 const unsigned short snum)
 {
 	struct inet_bind_bucket *tb = kmem_cache_alloc(cachep, GFP_ATOMIC);

 	if (tb != NULL) {
 		tb->ib_net       = hold_net(net);
 		tb->port      = snum;
 		tb->fastreuse = 0;
 		INIT_HLIST_HEAD(&tb->owners);
 		hlist_add_head(&tb->node, &head->chain);
 	}
 	return tb;
 }

 /*
  * Caller must hold hashbucket lock for this tb with local BH disabled
  */
 void inet_bind_bucket_destroy(struct kmem_cache *cachep, struct inet_bind_bucket *tb)
 {
 	if (hlist_empty(&tb->owners)) {
 		__hlist_del(&tb->node);
 		release_net(tb->ib_net);
 		kmem_cache_free(cachep, tb);
 	}
 }

 void inet_bind_hash(struct sock *sk, struct inet_bind_bucket *tb,
 		    const unsigned short snum)
 {
 	inet_sk(sk)->num = snum;
 	sk_add_bind_node(sk, &tb->owners);
 	inet_csk(sk)->icsk_bind_hash = tb;
 }

 /*
  * Get rid of any references to a local port held by the given sock.
  */
 static void __inet_put_port(struct sock *sk)
 {
 	struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;
 	const int bhash = inet_bhashfn(sock_net(sk), inet_sk(sk)->num,
 			hashinfo->bhash_size);
 	struct inet_bind_hashbucket *head = &hashinfo->bhash[bhash];
 	struct inet_bind_bucket *tb;

 	spin_lock(&head->lock);
 	tb = inet_csk(sk)->icsk_bind_hash;
 	__sk_del_bind_node(sk);
 	inet_csk(sk)->icsk_bind_hash = NULL;
 	inet_sk(sk)->num = 0;
 	inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb);
 	spin_unlock(&head->lock);
 }

 void inet_put_port(struct sock *sk)
 {
 	local_bh_disable();
 	__inet_put_port(sk);
 	local_bh_enable();
 }

 EXPORT_SYMBOL(inet_put_port);

 void __inet_inherit_port(struct sock *sk, struct sock *child)
 {
 	struct inet_hashinfo *table = sk->sk_prot->h.hashinfo;
 	const int bhash = inet_bhashfn(sock_net(sk), inet_sk(child)->num,
 			table->bhash_size);
 	struct inet_bind_hashbucket *head = &table->bhash[bhash];
 	struct inet_bind_bucket *tb;

 	spin_lock(&head->lock);
 	tb = inet_csk(sk)->icsk_bind_hash;
 	sk_add_bind_node(child, &tb->owners);
 	inet_csk(child)->icsk_bind_hash = tb;
 	spin_unlock(&head->lock);
 }

 EXPORT_SYMBOL_GPL(__inet_inherit_port);

 /*
  * This lock without WQ_FLAG_EXCLUSIVE is good on UP and it can be very bad on SMP.
  * Look, when several writers sleep and reader wakes them up, all but one
  * immediately hit write lock and grab all the cpus. Exclusive sleep solves
  * this, _but_ remember, it adds useless work on UP machines (wake up each
  * exclusive lock release). It should be ifdefed really.
  */
 void inet_listen_wlock(struct inet_hashinfo *hashinfo)
 	__acquires(hashinfo->lhash_lock)
 {
 	write_lock(&hashinfo->lhash_lock);

 	if (atomic_read(&hashinfo->lhash_users)) {
 		DEFINE_WAIT(wait);

 		for (;;) {
 			prepare_to_wait_exclusive(&hashinfo->lhash_wait,
 						  &wait, TASK_UNINTERRUPTIBLE);
 			if (!atomic_read(&hashinfo->lhash_users))
 				break;
 			write_unlock_bh(&hashinfo->lhash_lock);
 			schedule();
 			write_lock_bh(&hashinfo->lhash_lock);
 		}

 		finish_wait(&hashinfo->lhash_wait, &wait);
 	}
 }

 /*
  * Don't inline this cruft. Here are some nice properties to exploit here. The
  * BSD API does not allow a listening sock to specify the remote port nor the
  * remote address for the connection. So always assume those are both
  * wildcarded during the search since they can never be otherwise.
  */
 static struct sock *inet_lookup_listener_slow(struct net *net,
 					      const struct hlist_head *head,
 					      const __be32 daddr,
 					      const unsigned short hnum,
 					      const int dif)
 {
 	struct sock *result = NULL, *sk;
 	const struct hlist_node *node;
 	int hiscore = -1;

 	sk_for_each(sk, node, head) {
 		const struct inet_sock *inet = inet_sk(sk);

 		if (net_eq(sock_net(sk), net) && inet->num == hnum &&
 				!ipv6_only_sock(sk)) {
 			const __be32 rcv_saddr = inet->rcv_saddr;
 			int score = sk->sk_family == PF_INET ? 1 : 0;

 			if (rcv_saddr) {
 				if (rcv_saddr != daddr)
 					continue;
 				score += 2;
 			}
 			if (sk->sk_bound_dev_if) {
 				if (sk->sk_bound_dev_if != dif)
 					continue;
 				score += 2;
 			}
 			if (score == 5)
 				return sk;
 			if (score > hiscore) {
 				hiscore	= score;
 				result	= sk;
 			}
 		}
 	}
 	return result;
 }

 /* Optimize the common listener case. */
 struct sock *__inet_lookup_listener(struct net *net,
 				    struct inet_hashinfo *hashinfo,
 				    const __be32 daddr, const unsigned short hnum,
 				    const int dif)
 {
 	struct sock *sk = NULL;
 	const struct hlist_head *head;

 	read_lock(&hashinfo->lhash_lock);
 	head = &hashinfo->listening_hash[inet_lhashfn(net, hnum)];
 	if (!hlist_empty(head)) {
 		const struct inet_sock *inet = inet_sk((sk = __sk_head(head)));

 		if (inet->num == hnum && !sk->sk_node.next &&
 		    (!inet->rcv_saddr || inet->rcv_saddr == daddr) &&
 		    (sk->sk_family == PF_INET || !ipv6_only_sock(sk)) &&
 		    !sk->sk_bound_dev_if && net_eq(sock_net(sk), net))
 			goto sherry_cache;
 		sk = inet_lookup_listener_slow(net, head, daddr, hnum, dif);
 	}
 	if (sk) {
 sherry_cache:
 		sock_hold(sk);
 	}
 	read_unlock(&hashinfo->lhash_lock);
 	return sk;
 }
 EXPORT_SYMBOL_GPL(__inet_lookup_listener);

 struct sock * __inet_lookup_established(struct net *net,
 				  struct inet_hashinfo *hashinfo,
 				  const __be32 saddr, const __be16 sport,
 				  const __be32 daddr, const u16 hnum,
 				  const int dif)
 {
 	INET_ADDR_COOKIE(acookie, saddr, daddr)
 	const __portpair ports = INET_COMBINED_PORTS(sport, hnum);
 	struct sock *sk;
 	const struct hlist_node *node;
 	/* Optimize here for direct hit, only listening connections can
 	 * have wildcards anyways.
 	 */
 	unsigned int hash = inet_ehashfn(net, daddr, hnum, saddr, sport);
 	struct inet_ehash_bucket *head = inet_ehash_bucket(hashinfo, hash);
 	rwlock_t *lock = inet_ehash_lockp(hashinfo, hash);

 	prefetch(head->chain.first);
 	read_lock(lock);
 	sk_for_each(sk, node, &head->chain) {
 		if (INET_MATCH(sk, net, hash, acookie,
 					saddr, daddr, ports, dif))
 			goto hit; /* You sunk my battleship! */
 	}

 	/* Must check for a TIME_WAIT'er before going to listener hash. */
 	sk_for_each(sk, node, &head->twchain) {
 		if (INET_TW_MATCH(sk, net, hash, acookie,
 					saddr, daddr, ports, dif))
 			goto hit;
 	}
 	sk = NULL;
 out:
 	read_unlock(lock);
 	return sk;
 hit:
 	sock_hold(sk);
 	goto out;
 }
 EXPORT_SYMBOL_GPL(__inet_lookup_established);

 /* called with local bh disabled */
 static int __inet_check_established(struct inet_timewait_death_row *death_row,
 				    struct sock *sk, __u16 lport,
 				    struct inet_timewait_sock **twp)
 {
 	struct inet_hashinfo *hinfo = death_row->hashinfo;
 	struct inet_sock *inet = inet_sk(sk);
 	__be32 daddr = inet->rcv_saddr;
 	__be32 saddr = inet->daddr;
 	int dif = sk->sk_bound_dev_if;
 	INET_ADDR_COOKIE(acookie, saddr, daddr)
 	const __portpair ports = INET_COMBINED_PORTS(inet->dport, lport);
 	struct net *net = sock_net(sk);
 	unsigned int hash = inet_ehashfn(net, daddr, lport, saddr, inet->dport);
 	struct inet_ehash_bucket *head = inet_ehash_bucket(hinfo, hash);
 	rwlock_t *lock = inet_ehash_lockp(hinfo, hash);
 	struct sock *sk2;
 	const struct hlist_node *node;
 	struct inet_timewait_sock *tw;

 	prefetch(head->chain.first);
 	write_lock(lock);

 	/* Check TIME-WAIT sockets first. */
 	sk_for_each(sk2, node, &head->twchain) {
 		tw = inet_twsk(sk2);

 		if (INET_TW_MATCH(sk2, net, hash, acookie,
 					saddr, daddr, ports, dif)) {
 			if (twsk_unique(sk, sk2, twp))
 				goto unique;
 			else
 				goto not_unique;
 		}
 	}
 	tw = NULL;

 	/* And established part... */
 	sk_for_each(sk2, node, &head->chain) {
 		if (INET_MATCH(sk2, net, hash, acookie,
 					saddr, daddr, ports, dif))
 			goto not_unique;
 	}

 unique:
 	/* Must record num and sport now. Otherwise we will see
 	 * in hash table socket with a funny identity. */
 	inet->num = lport;
 	inet->sport = htons(lport);
 	sk->sk_hash = hash;
 	BUG_TRAP(sk_unhashed(sk));
 	__sk_add_node(sk, &head->chain);
 	sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
 	write_unlock(lock);

 	if (twp) {
 		*twp = tw;
 		NET_INC_STATS_BH(LINUX_MIB_TIMEWAITRECYCLED);
 	} else if (tw) {
 		/* Silly. Should hash-dance instead... */
 		inet_twsk_deschedule(tw, death_row);
 		NET_INC_STATS_BH(LINUX_MIB_TIMEWAITRECYCLED);

 		inet_twsk_put(tw);
 	}

 	return 0;

 not_unique:
 	write_unlock(lock);
 	return -EADDRNOTAVAIL;
 }

 static inline u32 inet_sk_port_offset(const struct sock *sk)
 {
 	const struct inet_sock *inet = inet_sk(sk);
 	return secure_ipv4_port_ephemeral(inet->rcv_saddr, inet->daddr,
 					  inet->dport);
 }

 void __inet_hash_nolisten(struct sock *sk)
 {
 	struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;
 	struct hlist_head *list;
 	rwlock_t *lock;
 	struct inet_ehash_bucket *head;

 	BUG_TRAP(sk_unhashed(sk));

 	sk->sk_hash = inet_sk_ehashfn(sk);
 	head = inet_ehash_bucket(hashinfo, sk->sk_hash);
 	list = &head->chain;
 	lock = inet_ehash_lockp(hashinfo, sk->sk_hash);

 	write_lock(lock);
 	__sk_add_node(sk, list);
 	sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
 	write_unlock(lock);
 }
 EXPORT_SYMBOL_GPL(__inet_hash_nolisten);

 static void __inet_hash(struct sock *sk)
 {
 	struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;
 	struct hlist_head *list;
 	rwlock_t *lock;

 	if (sk->sk_state != TCP_LISTEN) {
 		__inet_hash_nolisten(sk);
 		return;
 	}

 	BUG_TRAP(sk_unhashed(sk));
 	list = &hashinfo->listening_hash[inet_sk_listen_hashfn(sk)];
 	lock = &hashinfo->lhash_lock;

 	inet_listen_wlock(hashinfo);
 	__sk_add_node(sk, list);
 	sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
 	write_unlock(lock);
 	wake_up(&hashinfo->lhash_wait);
 }

 void inet_hash(struct sock *sk)
 {
 	if (sk->sk_state != TCP_CLOSE) {
 		local_bh_disable();
 		__inet_hash(sk);
 		local_bh_enable();
 	}
 }
 EXPORT_SYMBOL_GPL(inet_hash);

 void inet_unhash(struct sock *sk)
 {
 	rwlock_t *lock;
 	struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;

 	if (sk_unhashed(sk))
 		goto out;

 	if (sk->sk_state == TCP_LISTEN) {
 		local_bh_disable();
 		inet_listen_wlock(hashinfo);
 		lock = &hashinfo->lhash_lock;
 	} else {
 		lock = inet_ehash_lockp(hashinfo, sk->sk_hash);
 		write_lock_bh(lock);
 	}

 	if (__sk_del_node_init(sk))
 		sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
 	write_unlock_bh(lock);
 out:
 	if (sk->sk_state == TCP_LISTEN)
 		wake_up(&hashinfo->lhash_wait);
 }
 EXPORT_SYMBOL_GPL(inet_unhash);

 int __inet_hash_connect(struct inet_timewait_death_row *death_row,
 		struct sock *sk, u32 port_offset,
 		int (*check_established)(struct inet_timewait_death_row *,
 			struct sock *, __u16, struct inet_timewait_sock **),
 		void (*hash)(struct sock *sk))
 {
 	struct inet_hashinfo *hinfo = death_row->hashinfo;
 	const unsigned short snum = inet_sk(sk)->num;
 	struct inet_bind_hashbucket *head;
 	struct inet_bind_bucket *tb;
 	int ret;
 	struct net *net = sock_net(sk);

 	if (!snum) {
 		int i, remaining, low, high, port;
 		static u32 hint;
 		u32 offset = hint + port_offset;
 		struct hlist_node *node;
 		struct inet_timewait_sock *tw = NULL;

 		inet_get_local_port_range(&low, &high);
 		remaining = (high - low) + 1;

 		local_bh_disable();
 		for (i = 1; i <= remaining; i++) {
 			port = low + (i + offset) % remaining;
 			head = &hinfo->bhash[inet_bhashfn(net, port,
 					hinfo->bhash_size)];
 			spin_lock(&head->lock);

 			/* Does not bother with rcv_saddr checks,
 			 * because the established check is already
 			 * unique enough.
 			 */
 			inet_bind_bucket_for_each(tb, node, &head->chain) {
 				if (tb->ib_net == net && tb->port == port) {
 					BUG_TRAP(!hlist_empty(&tb->owners));
 					if (tb->fastreuse >= 0)
 						goto next_port;
 					if (!check_established(death_row, sk,
 								port, &tw))
 						goto ok;
 					goto next_port;
 				}
 			}

 			tb = inet_bind_bucket_create(hinfo->bind_bucket_cachep,
 					net, head, port);
 			if (!tb) {
 				spin_unlock(&head->lock);
 				break;
 			}
 			tb->fastreuse = -1;
 			goto ok;

 		next_port:
 			spin_unlock(&head->lock);
 		}
 		local_bh_enable();

 		return -EADDRNOTAVAIL;

 ok:
 		hint += i;

 		/* Head lock still held and bh's disabled */
 		inet_bind_hash(sk, tb, port);
 		if (sk_unhashed(sk)) {
 			inet_sk(sk)->sport = htons(port);
 			hash(sk);
 		}
 		spin_unlock(&head->lock);

 		if (tw) {
 			inet_twsk_deschedule(tw, death_row);
 			inet_twsk_put(tw);
 		}

 		ret = 0;
 		goto out;
 	}

 	head = &hinfo->bhash[inet_bhashfn(net, snum, hinfo->bhash_size)];
 	tb  = inet_csk(sk)->icsk_bind_hash;
 	spin_lock_bh(&head->lock);
 	if (sk_head(&tb->owners) == sk && !sk->sk_bind_node.next) {
 		hash(sk);
 		spin_unlock_bh(&head->lock);
 		return 0;
 	} else {
 		spin_unlock(&head->lock);
 		/* No definite answer... Walk to established hash table */
 		ret = check_established(death_row, sk, snum, NULL);
 out:
 		local_bh_enable();
 		return ret;
 	}
 }

 /*
  * Bind a port for a connect operation and hash it.
  */
 int inet_hash_connect(struct inet_timewait_death_row *death_row,
 		      struct sock *sk)
 {
 	return __inet_hash_connect(death_row, sk, inet_sk_port_offset(sk),
 			__inet_check_established, __inet_hash_nolisten);
 }

 EXPORT_SYMBOL_GPL(inet_hash_connect);
	/*
	* 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.
	*
	* Generic INET transport hashtables
	*
	* Authors: Lotsa people, from code originally in tcp
	*
	* 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.
	*/

	#include <linux/module.h>
	#include <linux/random.h>
	#include <linux/sched.h>
	#include <linux/slab.h>
	#include <linux/wait.h>

	#include <net/inet_connection_sock.h>
	#include <net/inet_hashtables.h>
	#include <net/ip.h>

	/*
	* Allocate and initialize a new local port bind bucket.
	* The bindhash mutex for snum's hash chain must be held here.
	*/
	struct inet_bind_bucket inet_bind_bucket_create(struct kmem_cache cachep,
	struct net *net,
	struct inet_bind_hashbucket *head,
	const unsigned short snum)
	{
	struct inet_bind_bucket *tb = kmem_cache_alloc(cachep, GFP_ATOMIC);

	if (tb != NULL) {
	tb->ib_net = hold_net(net);
	tb->port = snum;
	tb->fastreuse = 0;
	INIT_HLIST_HEAD(&tb->owners);
	hlist_add_head(&tb->node, &head->chain);
	}
	return tb;
	}

	/*
	* Caller must hold hashbucket lock for this tb with local BH disabled
	*/
	void inet_bind_bucket_destroy(struct kmem_cache cachep, struct inet_bind_bucket tb)
	{
	if (hlist_empty(&tb->owners)) {
	__hlist_del(&tb->node);
	release_net(tb->ib_net);
	kmem_cache_free(cachep, tb);
	}
	}

	void inet_bind_hash(struct sock sk, struct inet_bind_bucket tb,
	const unsigned short snum)
	{
	inet_sk(sk)->num = snum;
	sk_add_bind_node(sk, &tb->owners);
	inet_csk(sk)->icsk_bind_hash = tb;
	}

	/*
	* Get rid of any references to a local port held by the given sock.
	*/
	static void __inet_put_port(struct sock *sk)
	{
	struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;
	const int bhash = inet_bhashfn(sock_net(sk), inet_sk(sk)->num,
	hashinfo->bhash_size);
	struct inet_bind_hashbucket *head = &hashinfo->bhash[bhash];
	struct inet_bind_bucket *tb;

	spin_lock(&head->lock);
	tb = inet_csk(sk)->icsk_bind_hash;
	__sk_del_bind_node(sk);
	inet_csk(sk)->icsk_bind_hash = NULL;
	inet_sk(sk)->num = 0;
	inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb);
	spin_unlock(&head->lock);
	}

	void inet_put_port(struct sock *sk)
	{
	local_bh_disable();
	__inet_put_port(sk);
	local_bh_enable();
	}

	EXPORT_SYMBOL(inet_put_port);

	void __inet_inherit_port(struct sock sk, struct sock child)
	{
	struct inet_hashinfo *table = sk->sk_prot->h.hashinfo;
	const int bhash = inet_bhashfn(sock_net(sk), inet_sk(child)->num,
	table->bhash_size);
	struct inet_bind_hashbucket *head = &table->bhash[bhash];
	struct inet_bind_bucket *tb;

	spin_lock(&head->lock);
	tb = inet_csk(sk)->icsk_bind_hash;
	sk_add_bind_node(child, &tb->owners);
	inet_csk(child)->icsk_bind_hash = tb;
	spin_unlock(&head->lock);
	}

	EXPORT_SYMBOL_GPL(__inet_inherit_port);

	/*
	* This lock without WQ_FLAG_EXCLUSIVE is good on UP and it can be very bad on SMP.
	* Look, when several writers sleep and reader wakes them up, all but one
	* immediately hit write lock and grab all the cpus. Exclusive sleep solves
	* this, _but_ remember, it adds useless work on UP machines (wake up each
	* exclusive lock release). It should be ifdefed really.
	*/
	void inet_listen_wlock(struct inet_hashinfo *hashinfo)
	__acquires(hashinfo->lhash_lock)
	{
	write_lock(&hashinfo->lhash_lock);

	if (atomic_read(&hashinfo->lhash_users)) {
	DEFINE_WAIT(wait);

	for (;;) {
	prepare_to_wait_exclusive(&hashinfo->lhash_wait,
	&wait, TASK_UNINTERRUPTIBLE);
	if (!atomic_read(&hashinfo->lhash_users))
	break;
	write_unlock_bh(&hashinfo->lhash_lock);
	schedule();
	write_lock_bh(&hashinfo->lhash_lock);
	}

	finish_wait(&hashinfo->lhash_wait, &wait);
	}
	}

	/*
	* Don't inline this cruft. Here are some nice properties to exploit here. The
	* BSD API does not allow a listening sock to specify the remote port nor the
	* remote address for the connection. So always assume those are both
	* wildcarded during the search since they can never be otherwise.
	*/
	static struct sock inet_lookup_listener_slow(struct net net,
	const struct hlist_head *head,
	const __be32 daddr,
	const unsigned short hnum,
	const int dif)
	{
	struct sock result = NULL, sk;
	const struct hlist_node *node;
	int hiscore = -1;

	sk_for_each(sk, node, head) {
	const struct inet_sock *inet = inet_sk(sk);

	if (net_eq(sock_net(sk), net) && inet->num == hnum &&
	!ipv6_only_sock(sk)) {
	const __be32 rcv_saddr = inet->rcv_saddr;
	int score = sk->sk_family == PF_INET ? 1 : 0;

	if (rcv_saddr) {
	if (rcv_saddr != daddr)
	continue;
	score += 2;
	}
	if (sk->sk_bound_dev_if) {
	if (sk->sk_bound_dev_if != dif)
	continue;
	score += 2;
	}
	if (score == 5)
	return sk;
	if (score > hiscore) {
	hiscore = score;
	result = sk;
	}
	}
	}
	return result;
	}

	/* Optimize the common listener case. */
	struct sock __inet_lookup_listener(struct net net,
	struct inet_hashinfo *hashinfo,
	const __be32 daddr, const unsigned short hnum,
	const int dif)
	{
	struct sock *sk = NULL;
	const struct hlist_head *head;

	read_lock(&hashinfo->lhash_lock);
	head = &hashinfo->listening_hash[inet_lhashfn(net, hnum)];
	if (!hlist_empty(head)) {
	const struct inet_sock *inet = inet_sk((sk = __sk_head(head)));

	if (inet->num == hnum && !sk->sk_node.next &&
	(!inet->rcv_saddr \|\| inet->rcv_saddr == daddr) &&
	(sk->sk_family == PF_INET \|\| !ipv6_only_sock(sk)) &&
	!sk->sk_bound_dev_if && net_eq(sock_net(sk), net))
	goto sherry_cache;
	sk = inet_lookup_listener_slow(net, head, daddr, hnum, dif);
	}
	if (sk) {
	sherry_cache:
	sock_hold(sk);
	}
	read_unlock(&hashinfo->lhash_lock);
	return sk;
	}
	EXPORT_SYMBOL_GPL(__inet_lookup_listener);

	struct sock * __inet_lookup_established(struct net *net,
	struct inet_hashinfo *hashinfo,
	const __be32 saddr, const __be16 sport,
	const __be32 daddr, const u16 hnum,
	const int dif)
	{
	INET_ADDR_COOKIE(acookie, saddr, daddr)
	const __portpair ports = INET_COMBINED_PORTS(sport, hnum);
	struct sock *sk;
	const struct hlist_node *node;
	/* Optimize here for direct hit, only listening connections can
	* have wildcards anyways.
	*/
	unsigned int hash = inet_ehashfn(net, daddr, hnum, saddr, sport);
	struct inet_ehash_bucket *head = inet_ehash_bucket(hashinfo, hash);
	rwlock_t *lock = inet_ehash_lockp(hashinfo, hash);

	prefetch(head->chain.first);
	read_lock(lock);
	sk_for_each(sk, node, &head->chain) {
	if (INET_MATCH(sk, net, hash, acookie,
	saddr, daddr, ports, dif))
	goto hit; /* You sunk my battleship! */
	}

	/* Must check for a TIME_WAIT'er before going to listener hash. */
	sk_for_each(sk, node, &head->twchain) {
	if (INET_TW_MATCH(sk, net, hash, acookie,
	saddr, daddr, ports, dif))
	goto hit;
	}
	sk = NULL;
	out:
	read_unlock(lock);
	return sk;
	hit:
	sock_hold(sk);
	goto out;
	}
	EXPORT_SYMBOL_GPL(__inet_lookup_established);

	/* called with local bh disabled */
	static int __inet_check_established(struct inet_timewait_death_row *death_row,
	struct sock *sk, __u16 lport,
	struct inet_timewait_sock **twp)
	{
	struct inet_hashinfo *hinfo = death_row->hashinfo;
	struct inet_sock *inet = inet_sk(sk);
	__be32 daddr = inet->rcv_saddr;
	__be32 saddr = inet->daddr;
	int dif = sk->sk_bound_dev_if;
	INET_ADDR_COOKIE(acookie, saddr, daddr)
	const __portpair ports = INET_COMBINED_PORTS(inet->dport, lport);
	struct net *net = sock_net(sk);
	unsigned int hash = inet_ehashfn(net, daddr, lport, saddr, inet->dport);
	struct inet_ehash_bucket *head = inet_ehash_bucket(hinfo, hash);
	rwlock_t *lock = inet_ehash_lockp(hinfo, hash);
	struct sock *sk2;
	const struct hlist_node *node;
	struct inet_timewait_sock *tw;

	prefetch(head->chain.first);
	write_lock(lock);

	/* Check TIME-WAIT sockets first. */
	sk_for_each(sk2, node, &head->twchain) {
	tw = inet_twsk(sk2);

	if (INET_TW_MATCH(sk2, net, hash, acookie,
	saddr, daddr, ports, dif)) {
	if (twsk_unique(sk, sk2, twp))
	goto unique;
	else
	goto not_unique;
	}
	}
	tw = NULL;

	/* And established part... */
	sk_for_each(sk2, node, &head->chain) {
	if (INET_MATCH(sk2, net, hash, acookie,
	saddr, daddr, ports, dif))
	goto not_unique;
	}

	unique:
	/* Must record num and sport now. Otherwise we will see
	* in hash table socket with a funny identity. */
	inet->num = lport;
	inet->sport = htons(lport);
	sk->sk_hash = hash;
	BUG_TRAP(sk_unhashed(sk));
	__sk_add_node(sk, &head->chain);
	sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
	write_unlock(lock);

	if (twp) {
	*twp = tw;
	NET_INC_STATS_BH(LINUX_MIB_TIMEWAITRECYCLED);
	} else if (tw) {
	/* Silly. Should hash-dance instead... */
	inet_twsk_deschedule(tw, death_row);
	NET_INC_STATS_BH(LINUX_MIB_TIMEWAITRECYCLED);

	inet_twsk_put(tw);
	}

	return 0;

	not_unique:
	write_unlock(lock);
	return -EADDRNOTAVAIL;
	}

	static inline u32 inet_sk_port_offset(const struct sock *sk)
	{
	const struct inet_sock *inet = inet_sk(sk);
	return secure_ipv4_port_ephemeral(inet->rcv_saddr, inet->daddr,
	inet->dport);
	}

	void __inet_hash_nolisten(struct sock *sk)
	{
	struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;
	struct hlist_head *list;
	rwlock_t *lock;
	struct inet_ehash_bucket *head;

	BUG_TRAP(sk_unhashed(sk));

	sk->sk_hash = inet_sk_ehashfn(sk);
	head = inet_ehash_bucket(hashinfo, sk->sk_hash);
	list = &head->chain;
	lock = inet_ehash_lockp(hashinfo, sk->sk_hash);

	write_lock(lock);
	__sk_add_node(sk, list);
	sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
	write_unlock(lock);
	}
	EXPORT_SYMBOL_GPL(__inet_hash_nolisten);

	static void __inet_hash(struct sock *sk)
	{
	struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;
	struct hlist_head *list;
	rwlock_t *lock;

	if (sk->sk_state != TCP_LISTEN) {
	__inet_hash_nolisten(sk);
	return;
	}

	BUG_TRAP(sk_unhashed(sk));
	list = &hashinfo->listening_hash[inet_sk_listen_hashfn(sk)];
	lock = &hashinfo->lhash_lock;

	inet_listen_wlock(hashinfo);
	__sk_add_node(sk, list);
	sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
	write_unlock(lock);
	wake_up(&hashinfo->lhash_wait);
	}

	void inet_hash(struct sock *sk)
	{
	if (sk->sk_state != TCP_CLOSE) {
	local_bh_disable();
	__inet_hash(sk);
	local_bh_enable();
	}
	}
	EXPORT_SYMBOL_GPL(inet_hash);

	void inet_unhash(struct sock *sk)
	{
	rwlock_t *lock;
	struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;

	if (sk_unhashed(sk))
	goto out;

	if (sk->sk_state == TCP_LISTEN) {
	local_bh_disable();
	inet_listen_wlock(hashinfo);
	lock = &hashinfo->lhash_lock;
	} else {
	lock = inet_ehash_lockp(hashinfo, sk->sk_hash);
	write_lock_bh(lock);
	}

	if (__sk_del_node_init(sk))
	sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
	write_unlock_bh(lock);
	out:
	if (sk->sk_state == TCP_LISTEN)
	wake_up(&hashinfo->lhash_wait);
	}
	EXPORT_SYMBOL_GPL(inet_unhash);

	int __inet_hash_connect(struct inet_timewait_death_row *death_row,
	struct sock *sk, u32 port_offset,
	int (check_established)(struct inet_timewait_death_row ,
	struct sock , __u16, struct inet_timewait_sock *),
	void (hash)(struct sock sk))
	{
	struct inet_hashinfo *hinfo = death_row->hashinfo;
	const unsigned short snum = inet_sk(sk)->num;
	struct inet_bind_hashbucket *head;
	struct inet_bind_bucket *tb;
	int ret;
	struct net *net = sock_net(sk);

	if (!snum) {
	int i, remaining, low, high, port;
	static u32 hint;
	u32 offset = hint + port_offset;
	struct hlist_node *node;
	struct inet_timewait_sock *tw = NULL;

	inet_get_local_port_range(&low, &high);
	remaining = (high - low) + 1;

	local_bh_disable();
	for (i = 1; i <= remaining; i++) {
	port = low + (i + offset) % remaining;
	head = &hinfo->bhash[inet_bhashfn(net, port,
	hinfo->bhash_size)];
	spin_lock(&head->lock);

	/* Does not bother with rcv_saddr checks,
	* because the established check is already
	* unique enough.
	*/
	inet_bind_bucket_for_each(tb, node, &head->chain) {
	if (tb->ib_net == net && tb->port == port) {
	BUG_TRAP(!hlist_empty(&tb->owners));
	if (tb->fastreuse >= 0)
	goto next_port;
	if (!check_established(death_row, sk,
	port, &tw))
	goto ok;
	goto next_port;
	}
	}

	tb = inet_bind_bucket_create(hinfo->bind_bucket_cachep,
	net, head, port);
	if (!tb) {
	spin_unlock(&head->lock);
	break;
	}
	tb->fastreuse = -1;
	goto ok;

	next_port:
	spin_unlock(&head->lock);
	}
	local_bh_enable();

	return -EADDRNOTAVAIL;

	ok:
	hint += i;

	/* Head lock still held and bh's disabled */
	inet_bind_hash(sk, tb, port);
	if (sk_unhashed(sk)) {
	inet_sk(sk)->sport = htons(port);
	hash(sk);
	}
	spin_unlock(&head->lock);

	if (tw) {
	inet_twsk_deschedule(tw, death_row);
	inet_twsk_put(tw);
	}

	ret = 0;
	goto out;
	}

	head = &hinfo->bhash[inet_bhashfn(net, snum, hinfo->bhash_size)];
	tb = inet_csk(sk)->icsk_bind_hash;
	spin_lock_bh(&head->lock);
	if (sk_head(&tb->owners) == sk && !sk->sk_bind_node.next) {
	hash(sk);
	spin_unlock_bh(&head->lock);
	return 0;
	} else {
	spin_unlock(&head->lock);
	/* No definite answer... Walk to established hash table */
	ret = check_established(death_row, sk, snum, NULL);
	out:
	local_bh_enable();
	return ret;
	}
	}

	/*
	* Bind a port for a connect operation and hash it.
	*/
	int inet_hash_connect(struct inet_timewait_death_row *death_row,
	struct sock *sk)
	{
	return __inet_hash_connect(death_row, sk, inet_sk_port_offset(sk),
	__inet_check_established, __inet_hash_nolisten);
	}

	EXPORT_SYMBOL_GPL(inet_hash_connect);