/*
   * 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/secure_seq.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) {

  		write_pnet(&tb->ib_net, hold_net(net));

  		tb->port      = snum;
  		tb->fastreuse = 0;

  		tb->num_owners = 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(ib_net(tb));

  		kmem_cache_free(cachep, tb);
  	}
  }

  
  void inet_bind_hash(struct sock *sk, struct inet_bind_bucket *tb,
  		    const unsigned short snum)
  {

  	struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;

  	atomic_inc(&hashinfo->bsockets);

  	inet_sk(sk)->inet_num = snum;

  	sk_add_bind_node(sk, &tb->owners);

  	tb->num_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)->inet_num,

  			hashinfo->bhash_size);

  	struct inet_bind_hashbucket *head = &hashinfo->bhash[bhash];
  	struct inet_bind_bucket *tb;

  	atomic_dec(&hashinfo->bsockets);

  	spin_lock(&head->lock);

  	tb = inet_csk(sk)->icsk_bind_hash;

  	__sk_del_bind_node(sk);

  	tb->num_owners--;

  	inet_csk(sk)->icsk_bind_hash = NULL;

  	inet_sk(sk)->inet_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);

  int __inet_inherit_port(struct sock *sk, struct sock *child)

  {
  	struct inet_hashinfo *table = sk->sk_prot->h.hashinfo;

  	unsigned short port = inet_sk(child)->inet_num;
  	const int bhash = inet_bhashfn(sock_net(sk), port,

  			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;

  	if (tb->port != port) {
  		/* NOTE: using tproxy and redirecting skbs to a proxy
  		 * on a different listener port breaks the assumption
  		 * that the listener socket's icsk_bind_hash is the same
  		 * as that of the child socket. We have to look up or
  		 * create a new bind bucket for the child here. */
  		struct hlist_node *node;
  		inet_bind_bucket_for_each(tb, node, &head->chain) {
  			if (net_eq(ib_net(tb), sock_net(sk)) &&
  			    tb->port == port)
  				break;
  		}
  		if (!node) {
  			tb = inet_bind_bucket_create(table->bind_bucket_cachep,
  						     sock_net(sk), head, port);
  			if (!tb) {
  				spin_unlock(&head->lock);
  				return -ENOMEM;
  			}
  		}
  	}

  	inet_bind_hash(child, tb, port);

  	spin_unlock(&head->lock);

  
  	return 0;

  }

  EXPORT_SYMBOL_GPL(__inet_inherit_port);

  static inline int compute_score(struct sock *sk, struct net *net,
  				const unsigned short hnum, const __be32 daddr,
  				const int dif)
  {
  	int score = -1;
  	struct inet_sock *inet = inet_sk(sk);

  	if (net_eq(sock_net(sk), net) && inet->inet_num == hnum &&

  			!ipv6_only_sock(sk)) {

  		__be32 rcv_saddr = inet->inet_rcv_saddr;

  		score = sk->sk_family == PF_INET ? 1 : 0;
  		if (rcv_saddr) {
  			if (rcv_saddr != daddr)
  				return -1;
  			score += 2;
  		}
  		if (sk->sk_bound_dev_if) {
  			if (sk->sk_bound_dev_if != dif)
  				return -1;
  			score += 2;
  		}
  	}
  	return score;
  }

  /*

   * 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.
   */

  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, *result;
  	struct hlist_nulls_node *node;
  	unsigned int hash = inet_lhashfn(net, hnum);
  	struct inet_listen_hashbucket *ilb = &hashinfo->listening_hash[hash];
  	int score, hiscore;

  	rcu_read_lock();
  begin:
  	result = NULL;
  	hiscore = -1;
  	sk_nulls_for_each_rcu(sk, node, &ilb->head) {
  		score = compute_score(sk, net, hnum, daddr, dif);
  		if (score > hiscore) {
  			result = sk;
  			hiscore = score;
  		}

  	}

  	/*
  	 * if the nulls value we got at the end of this lookup is
  	 * not the expected one, we must restart lookup.
  	 * We probably met an item that was moved to another chain.
  	 */
  	if (get_nulls_value(node) != hash + LISTENING_NULLS_BASE)
  		goto begin;
  	if (result) {
  		if (unlikely(!atomic_inc_not_zero(&result->sk_refcnt)))
  			result = NULL;
  		else if (unlikely(compute_score(result, net, hnum, daddr,
  				  dif) < hiscore)) {
  			sock_put(result);
  			goto begin;
  		}

  	}

  	rcu_read_unlock();
  	return result;

  }

  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_nulls_node *node;

  	/* Optimize here for direct hit, only listening connections can
  	 * have wildcards anyways.
  	 */

  	unsigned int hash = inet_ehashfn(net, daddr, hnum, saddr, sport);

  	unsigned int slot = hash & hashinfo->ehash_mask;

  	struct inet_ehash_bucket *head = &hashinfo->ehash[slot];

  	rcu_read_lock();
  begin:
  	sk_nulls_for_each_rcu(sk, node, &head->chain) {

  		if (INET_MATCH(sk, net, hash, acookie,

  					saddr, daddr, ports, dif)) {
  			if (unlikely(!atomic_inc_not_zero(&sk->sk_refcnt)))
  				goto begintw;
  			if (unlikely(!INET_MATCH(sk, net, hash, acookie,
  				saddr, daddr, ports, dif))) {
  				sock_put(sk);
  				goto begin;
  			}
  			goto out;
  		}

  	}

  	/*
  	 * if the nulls value we got at the end of this lookup is
  	 * not the expected one, we must restart lookup.
  	 * We probably met an item that was moved to another chain.
  	 */
  	if (get_nulls_value(node) != slot)
  		goto begin;

  begintw:

  	/* Must check for a TIME_WAIT'er before going to listener hash. */

  	sk_nulls_for_each_rcu(sk, node, &head->twchain) {

  		if (INET_TW_MATCH(sk, net, hash, acookie,

  					saddr, daddr, ports, dif)) {
  			if (unlikely(!atomic_inc_not_zero(&sk->sk_refcnt))) {
  				sk = NULL;
  				goto out;
  			}
  			if (unlikely(!INET_TW_MATCH(sk, net, hash, acookie,
  				 saddr, daddr, ports, dif))) {
  				sock_put(sk);
  				goto begintw;
  			}
  			goto out;
  		}

  	}

  	/*
  	 * if the nulls value we got at the end of this lookup is
  	 * not the expected one, we must restart lookup.
  	 * We probably met an item that was moved to another chain.
  	 */
  	if (get_nulls_value(node) != slot)
  		goto begintw;

  	sk = NULL;
  out:

  	rcu_read_unlock();

  	return sk;

  }
  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->inet_rcv_saddr;
  	__be32 saddr = inet->inet_daddr;

  	int dif = sk->sk_bound_dev_if;
  	INET_ADDR_COOKIE(acookie, saddr, daddr)

  	const __portpair ports = INET_COMBINED_PORTS(inet->inet_dport, lport);

  	struct net *net = sock_net(sk);

  	unsigned int hash = inet_ehashfn(net, daddr, lport,
  					 saddr, inet->inet_dport);

  	struct inet_ehash_bucket *head = inet_ehash_bucket(hinfo, hash);

  	spinlock_t *lock = inet_ehash_lockp(hinfo, hash);

  	struct sock *sk2;

  	const struct hlist_nulls_node *node;

  	struct inet_timewait_sock *tw;

  	int twrefcnt = 0;

  	spin_lock(lock);

  
  	/* Check TIME-WAIT sockets first. */

  	sk_nulls_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_nulls_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->inet_num = lport;
  	inet->inet_sport = htons(lport);

  	sk->sk_hash = hash;

  	WARN_ON(!sk_unhashed(sk));

  	__sk_nulls_add_node_rcu(sk, &head->chain);

  	if (tw) {
  		twrefcnt = inet_twsk_unhash(tw);
  		NET_INC_STATS_BH(net, LINUX_MIB_TIMEWAITRECYCLED);
  	}

  	spin_unlock(lock);

  	if (twrefcnt)
  		inet_twsk_put(tw);

  	sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);

  
  	if (twp) {
  		*twp = tw;

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

  
  		inet_twsk_put(tw);
  	}

  	return 0;
  
  not_unique:

  	spin_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->inet_rcv_saddr,
  					  inet->inet_daddr,
  					  inet->inet_dport);

  }

  int __inet_hash_nolisten(struct sock *sk, struct inet_timewait_sock *tw)

  {

  	struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;

  	struct hlist_nulls_head *list;

  	spinlock_t *lock;

  	struct inet_ehash_bucket *head;

  	int twrefcnt = 0;

  	WARN_ON(!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);

  	spin_lock(lock);

  	__sk_nulls_add_node_rcu(sk, list);

  	if (tw) {
  		WARN_ON(sk->sk_hash != tw->tw_hash);
  		twrefcnt = inet_twsk_unhash(tw);
  	}

  	spin_unlock(lock);

  	sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);

  	return twrefcnt;

  }
  EXPORT_SYMBOL_GPL(__inet_hash_nolisten);

  static void __inet_hash(struct sock *sk)

  {

  	struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;

  	struct inet_listen_hashbucket *ilb;

  
  	if (sk->sk_state != TCP_LISTEN) {

  		__inet_hash_nolisten(sk, NULL);

  		return;
  	}

  	WARN_ON(!sk_unhashed(sk));

  	ilb = &hashinfo->listening_hash[inet_sk_listen_hashfn(sk)];

  	spin_lock(&ilb->lock);

  	__sk_nulls_add_node_rcu(sk, &ilb->head);

  	sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);

  	spin_unlock(&ilb->lock);

  }

  
  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)
  {

  	struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;

  	spinlock_t *lock;
  	int done;

  
  	if (sk_unhashed(sk))

  		return;

  	if (sk->sk_state == TCP_LISTEN)
  		lock = &hashinfo->listening_hash[inet_sk_listen_hashfn(sk)].lock;
  	else
  		lock = inet_ehash_lockp(hashinfo, sk->sk_hash);

  	spin_lock_bh(lock);
  	done =__sk_nulls_del_node_init_rcu(sk);

  	if (done)
  		sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);

  	spin_unlock_bh(lock);

  }
  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 **),

  		int (*hash)(struct sock *sk, struct inet_timewait_sock *twp))

  {
  	struct inet_hashinfo *hinfo = death_row->hashinfo;

  	const unsigned short snum = inet_sk(sk)->inet_num;

  	struct inet_bind_hashbucket *head;
  	struct inet_bind_bucket *tb;

  	int ret;

  	struct net *net = sock_net(sk);

  	int twrefcnt = 1;

  	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;

  			if (inet_is_reserved_local_port(port))
  				continue;

  			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 (net_eq(ib_net(tb), net) &&
  				    tb->port == port) {

  					if (tb->fastreuse >= 0)
  						goto next_port;

  					WARN_ON(hlist_empty(&tb->owners));

  					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)->inet_sport = htons(port);

  			twrefcnt += hash(sk, tw);

  		}

  		if (tw)
  			twrefcnt += inet_twsk_bind_unhash(tw, hinfo);

  		spin_unlock(&head->lock);

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

  			while (twrefcnt) {
  				twrefcnt--;
  				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, NULL);

  		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);

  
  void inet_hashinfo_init(struct inet_hashinfo *h)
  {
  	int i;

  	atomic_set(&h->bsockets, 0);

  	for (i = 0; i < INET_LHTABLE_SIZE; i++) {

  		spin_lock_init(&h->listening_hash[i].lock);

  		INIT_HLIST_NULLS_HEAD(&h->listening_hash[i].head,
  				      i + LISTENING_NULLS_BASE);
  		}

  }

  EXPORT_SYMBOL_GPL(inet_hashinfo_init);