/* Connection state tracking for netfilter.  This is separated from,
     but required by, the NAT layer; it can also be used by an iptables
     extension. */
  
  /* (C) 1999-2001 Paul `Rusty' Russell

   * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>

   * (C) 2003,2004 USAGI/WIDE Project <http://www.linux-ipv6.org>

   * (C) 2005-2012 Patrick McHardy <kaber@trash.net>

   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as
   * published by the Free Software Foundation.

   */

  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

  #include <linux/types.h>
  #include <linux/netfilter.h>
  #include <linux/module.h>

  #include <linux/sched.h>

  #include <linux/skbuff.h>
  #include <linux/proc_fs.h>
  #include <linux/vmalloc.h>
  #include <linux/stddef.h>
  #include <linux/slab.h>
  #include <linux/random.h>
  #include <linux/jhash.h>
  #include <linux/err.h>
  #include <linux/percpu.h>
  #include <linux/moduleparam.h>
  #include <linux/notifier.h>
  #include <linux/kernel.h>
  #include <linux/netdevice.h>
  #include <linux/socket.h>

  #include <linux/mm.h>

  #include <linux/nsproxy.h>

  #include <linux/rculist_nulls.h>

  #include <net/netfilter/nf_conntrack.h>
  #include <net/netfilter/nf_conntrack_l3proto.h>

  #include <net/netfilter/nf_conntrack_l4proto.h>

  #include <net/netfilter/nf_conntrack_expect.h>

  #include <net/netfilter/nf_conntrack_helper.h>

  #include <net/netfilter/nf_conntrack_seqadj.h>

  #include <net/netfilter/nf_conntrack_core.h>

  #include <net/netfilter/nf_conntrack_extend.h>

  #include <net/netfilter/nf_conntrack_acct.h>

  #include <net/netfilter/nf_conntrack_ecache.h>

  #include <net/netfilter/nf_conntrack_zones.h>

  #include <net/netfilter/nf_conntrack_timestamp.h>

  #include <net/netfilter/nf_conntrack_timeout.h>

  #include <net/netfilter/nf_conntrack_labels.h>

  #include <net/netfilter/nf_conntrack_synproxy.h>

  #include <net/netfilter/nf_nat.h>

  #include <net/netfilter/nf_nat_core.h>

  #include <net/netfilter/nf_nat_helper.h>

  #include <net/netns/hash.h>

  #define NF_CONNTRACK_VERSION	"0.5.0"

  int (*nfnetlink_parse_nat_setup_hook)(struct nf_conn *ct,
  				      enum nf_nat_manip_type manip,

  				      const struct nlattr *attr) __read_mostly;

  EXPORT_SYMBOL_GPL(nfnetlink_parse_nat_setup_hook);

  __cacheline_aligned_in_smp spinlock_t nf_conntrack_locks[CONNTRACK_LOCKS];
  EXPORT_SYMBOL_GPL(nf_conntrack_locks);

  __cacheline_aligned_in_smp DEFINE_SPINLOCK(nf_conntrack_expect_lock);
  EXPORT_SYMBOL_GPL(nf_conntrack_expect_lock);

  struct hlist_nulls_head *nf_conntrack_hash __read_mostly;
  EXPORT_SYMBOL_GPL(nf_conntrack_hash);

  static __read_mostly struct kmem_cache *nf_conntrack_cachep;

  static __read_mostly spinlock_t nf_conntrack_locks_all_lock;

  static __read_mostly seqcount_t nf_conntrack_generation;

  static __read_mostly DEFINE_SPINLOCK(nf_conntrack_locks_all_lock);

  static __read_mostly bool nf_conntrack_locks_all;
  
  void nf_conntrack_lock(spinlock_t *lock) __acquires(lock)
  {
  	spin_lock(lock);
  	while (unlikely(nf_conntrack_locks_all)) {
  		spin_unlock(lock);

  		spin_unlock_wait(&nf_conntrack_locks_all_lock);

  		spin_lock(lock);
  	}
  }
  EXPORT_SYMBOL_GPL(nf_conntrack_lock);

  static void nf_conntrack_double_unlock(unsigned int h1, unsigned int h2)
  {
  	h1 %= CONNTRACK_LOCKS;
  	h2 %= CONNTRACK_LOCKS;
  	spin_unlock(&nf_conntrack_locks[h1]);
  	if (h1 != h2)
  		spin_unlock(&nf_conntrack_locks[h2]);
  }
  
  /* return true if we need to recompute hashes (in case hash table was resized) */
  static bool nf_conntrack_double_lock(struct net *net, unsigned int h1,
  				     unsigned int h2, unsigned int sequence)
  {
  	h1 %= CONNTRACK_LOCKS;
  	h2 %= CONNTRACK_LOCKS;
  	if (h1 <= h2) {

  		nf_conntrack_lock(&nf_conntrack_locks[h1]);

  		if (h1 != h2)
  			spin_lock_nested(&nf_conntrack_locks[h2],
  					 SINGLE_DEPTH_NESTING);
  	} else {

  		nf_conntrack_lock(&nf_conntrack_locks[h2]);

  		spin_lock_nested(&nf_conntrack_locks[h1],
  				 SINGLE_DEPTH_NESTING);
  	}

  	if (read_seqcount_retry(&nf_conntrack_generation, sequence)) {

  		nf_conntrack_double_unlock(h1, h2);
  		return true;
  	}
  	return false;
  }
  
  static void nf_conntrack_all_lock(void)
  {
  	int i;

  	spin_lock(&nf_conntrack_locks_all_lock);
  	nf_conntrack_locks_all = true;
  
  	for (i = 0; i < CONNTRACK_LOCKS; i++) {

  		spin_unlock_wait(&nf_conntrack_locks[i]);

  	}

  }
  
  static void nf_conntrack_all_unlock(void)
  {

  	nf_conntrack_locks_all = false;
  	spin_unlock(&nf_conntrack_locks_all_lock);

  }

  unsigned int nf_conntrack_htable_size __read_mostly;

  EXPORT_SYMBOL_GPL(nf_conntrack_htable_size);

  unsigned int nf_conntrack_max __read_mostly;

  EXPORT_SYMBOL_GPL(nf_conntrack_max);

  DEFINE_PER_CPU(struct nf_conn, nf_conntrack_untracked);
  EXPORT_PER_CPU_SYMBOL(nf_conntrack_untracked);

  static unsigned int nf_conntrack_hash_rnd __read_mostly;

  static u32 hash_conntrack_raw(const struct nf_conntrack_tuple *tuple,
  			      const struct net *net)

  {

  	unsigned int n;

  	u32 seed;

  	get_random_once(&nf_conntrack_hash_rnd, sizeof(nf_conntrack_hash_rnd));

  	/* The direction must be ignored, so we hash everything up to the
  	 * destination ports (which is a multiple of 4) and treat the last
  	 * three bytes manually.
  	 */

  	seed = nf_conntrack_hash_rnd ^ net_hash_mix(net);

  	n = (sizeof(tuple->src) + sizeof(tuple->dst.u3)) / sizeof(u32);

  	return jhash2((u32 *)tuple, n, seed ^

  		      (((__force __u16)tuple->dst.u.all << 16) |
  		      tuple->dst.protonum));
  }

  static u32 scale_hash(u32 hash)

  {

  	return reciprocal_scale(hash, nf_conntrack_htable_size);

  }

  static u32 __hash_conntrack(const struct net *net,
  			    const struct nf_conntrack_tuple *tuple,
  			    unsigned int size)

  {

  	return reciprocal_scale(hash_conntrack_raw(tuple, net), size);

  }

  static u32 hash_conntrack(const struct net *net,
  			  const struct nf_conntrack_tuple *tuple)

  {

  	return scale_hash(hash_conntrack_raw(tuple, net));

  }

  bool

  nf_ct_get_tuple(const struct sk_buff *skb,
  		unsigned int nhoff,
  		unsigned int dataoff,
  		u_int16_t l3num,
  		u_int8_t protonum,

  		struct net *net,

  		struct nf_conntrack_tuple *tuple,
  		const struct nf_conntrack_l3proto *l3proto,

  		const struct nf_conntrack_l4proto *l4proto)

  {

  	memset(tuple, 0, sizeof(*tuple));

  
  	tuple->src.l3num = l3num;
  	if (l3proto->pkt_to_tuple(skb, nhoff, tuple) == 0)

  		return false;

  
  	tuple->dst.protonum = protonum;
  	tuple->dst.dir = IP_CT_DIR_ORIGINAL;

  	return l4proto->pkt_to_tuple(skb, dataoff, net, tuple);

  }

  EXPORT_SYMBOL_GPL(nf_ct_get_tuple);

  bool nf_ct_get_tuplepr(const struct sk_buff *skb, unsigned int nhoff,

  		       u_int16_t l3num,
  		       struct net *net, struct nf_conntrack_tuple *tuple)

  {
  	struct nf_conntrack_l3proto *l3proto;
  	struct nf_conntrack_l4proto *l4proto;
  	unsigned int protoff;
  	u_int8_t protonum;
  	int ret;
  
  	rcu_read_lock();
  
  	l3proto = __nf_ct_l3proto_find(l3num);
  	ret = l3proto->get_l4proto(skb, nhoff, &protoff, &protonum);
  	if (ret != NF_ACCEPT) {
  		rcu_read_unlock();

  		return false;

  	}
  
  	l4proto = __nf_ct_l4proto_find(l3num, protonum);

  	ret = nf_ct_get_tuple(skb, nhoff, protoff, l3num, protonum, net, tuple,

  			      l3proto, l4proto);
  
  	rcu_read_unlock();
  	return ret;
  }
  EXPORT_SYMBOL_GPL(nf_ct_get_tuplepr);

  bool

  nf_ct_invert_tuple(struct nf_conntrack_tuple *inverse,
  		   const struct nf_conntrack_tuple *orig,
  		   const struct nf_conntrack_l3proto *l3proto,

  		   const struct nf_conntrack_l4proto *l4proto)

  {

  	memset(inverse, 0, sizeof(*inverse));

  
  	inverse->src.l3num = orig->src.l3num;
  	if (l3proto->invert_tuple(inverse, orig) == 0)

  		return false;

  
  	inverse->dst.dir = !orig->dst.dir;
  
  	inverse->dst.protonum = orig->dst.protonum;

  	return l4proto->invert_tuple(inverse, orig);

  }

  EXPORT_SYMBOL_GPL(nf_ct_invert_tuple);

  static void
  clean_from_lists(struct nf_conn *ct)
  {

  	pr_debug("clean_from_lists(%p)
  ", ct);

  	hlist_nulls_del_rcu(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode);
  	hlist_nulls_del_rcu(&ct->tuplehash[IP_CT_DIR_REPLY].hnnode);

  
  	/* Destroy all pending expectations */

  	nf_ct_remove_expectations(ct);

  }

  /* must be called with local_bh_disable */
  static void nf_ct_add_to_dying_list(struct nf_conn *ct)
  {
  	struct ct_pcpu *pcpu;
  
  	/* add this conntrack to the (per cpu) dying list */
  	ct->cpu = smp_processor_id();
  	pcpu = per_cpu_ptr(nf_ct_net(ct)->ct.pcpu_lists, ct->cpu);
  
  	spin_lock(&pcpu->lock);
  	hlist_nulls_add_head(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode,
  			     &pcpu->dying);
  	spin_unlock(&pcpu->lock);
  }
  
  /* must be called with local_bh_disable */
  static void nf_ct_add_to_unconfirmed_list(struct nf_conn *ct)
  {
  	struct ct_pcpu *pcpu;
  
  	/* add this conntrack to the (per cpu) unconfirmed list */
  	ct->cpu = smp_processor_id();
  	pcpu = per_cpu_ptr(nf_ct_net(ct)->ct.pcpu_lists, ct->cpu);
  
  	spin_lock(&pcpu->lock);
  	hlist_nulls_add_head(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode,
  			     &pcpu->unconfirmed);
  	spin_unlock(&pcpu->lock);
  }
  
  /* must be called with local_bh_disable */
  static void nf_ct_del_from_dying_or_unconfirmed_list(struct nf_conn *ct)
  {
  	struct ct_pcpu *pcpu;
  
  	/* We overload first tuple to link into unconfirmed or dying list.*/
  	pcpu = per_cpu_ptr(nf_ct_net(ct)->ct.pcpu_lists, ct->cpu);
  
  	spin_lock(&pcpu->lock);
  	BUG_ON(hlist_nulls_unhashed(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode));
  	hlist_nulls_del_rcu(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode);
  	spin_unlock(&pcpu->lock);
  }

  /* Released via destroy_conntrack() */

  struct nf_conn *nf_ct_tmpl_alloc(struct net *net,
  				 const struct nf_conntrack_zone *zone,
  				 gfp_t flags)

  {
  	struct nf_conn *tmpl;

  	tmpl = kzalloc(sizeof(*tmpl), flags);

  	if (tmpl == NULL)
  		return NULL;
  
  	tmpl->status = IPS_TEMPLATE;
  	write_pnet(&tmpl->ct_net, net);

  	nf_ct_zone_add(tmpl, zone);

  	atomic_set(&tmpl->ct_general.use, 0);
  
  	return tmpl;

  }
  EXPORT_SYMBOL_GPL(nf_ct_tmpl_alloc);

  void nf_ct_tmpl_free(struct nf_conn *tmpl)

  {
  	nf_ct_ext_destroy(tmpl);
  	nf_ct_ext_free(tmpl);
  	kfree(tmpl);
  }

  EXPORT_SYMBOL_GPL(nf_ct_tmpl_free);

  static void
  destroy_conntrack(struct nf_conntrack *nfct)
  {
  	struct nf_conn *ct = (struct nf_conn *)nfct;

  	struct net *net = nf_ct_net(ct);

  	struct nf_conntrack_l4proto *l4proto;

  	pr_debug("destroy_conntrack(%p)
  ", ct);

  	NF_CT_ASSERT(atomic_read(&nfct->use) == 0);
  	NF_CT_ASSERT(!timer_pending(&ct->timeout));

  	if (unlikely(nf_ct_is_template(ct))) {
  		nf_ct_tmpl_free(ct);
  		return;
  	}

  	rcu_read_lock();

  	l4proto = __nf_ct_l4proto_find(nf_ct_l3num(ct), nf_ct_protonum(ct));

  	if (l4proto->destroy)

  		l4proto->destroy(ct);

  	rcu_read_unlock();

  	local_bh_disable();

  	/* Expectations will have been removed in clean_from_lists,
  	 * except TFTP can create an expectation on the first packet,
  	 * before connection is in the list, so we need to clean here,

  	 * too.
  	 */

  	nf_ct_remove_expectations(ct);

  	nf_ct_del_from_dying_or_unconfirmed_list(ct);

  	NF_CT_STAT_INC(net, delete);

  	local_bh_enable();

  
  	if (ct->master)
  		nf_ct_put(ct->master);

  	pr_debug("destroy_conntrack: returning ct=%p to slab
  ", ct);

  	nf_conntrack_free(ct);
  }

  static void nf_ct_delete_from_lists(struct nf_conn *ct)

  {

  	struct net *net = nf_ct_net(ct);

  	unsigned int hash, reply_hash;

  	unsigned int sequence;

  	nf_ct_helper_destroy(ct);

  
  	local_bh_disable();
  	do {

  		sequence = read_seqcount_begin(&nf_conntrack_generation);

  		hash = hash_conntrack(net,

  				      &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);

  		reply_hash = hash_conntrack(net,

  					   &ct->tuplehash[IP_CT_DIR_REPLY].tuple);
  	} while (nf_conntrack_double_lock(net, hash, reply_hash, sequence));

  	clean_from_lists(ct);

  	nf_conntrack_double_unlock(hash, reply_hash);

  	nf_ct_add_to_dying_list(ct);

  
  	NF_CT_STAT_INC(net, delete_list);
  	local_bh_enable();

  }

  bool nf_ct_delete(struct nf_conn *ct, u32 portid, int report)

  {

  	struct nf_conn_tstamp *tstamp;
  
  	tstamp = nf_conn_tstamp_find(ct);
  	if (tstamp && tstamp->stop == 0)

  		tstamp->stop = ktime_get_real_ns();

  	if (nf_ct_is_dying(ct))
  		goto delete;
  
  	if (nf_conntrack_event_report(IPCT_DESTROY, ct,
  				    portid, report) < 0) {

  		/* destroy event was not delivered */
  		nf_ct_delete_from_lists(ct);

  		nf_conntrack_ecache_delayed_work(nf_ct_net(ct));

  		return false;

  	}

  
  	nf_conntrack_ecache_work(nf_ct_net(ct));

  	set_bit(IPS_DYING_BIT, &ct->status);

   delete:

  	nf_ct_delete_from_lists(ct);

  	nf_ct_put(ct);

  	return true;
  }
  EXPORT_SYMBOL_GPL(nf_ct_delete);
  
  static void death_by_timeout(unsigned long ul_conntrack)
  {
  	nf_ct_delete((struct nf_conn *)ul_conntrack, 0, 0);

  }

  static inline bool
  nf_ct_key_equal(struct nf_conntrack_tuple_hash *h,

  		const struct nf_conntrack_tuple *tuple,

  		const struct nf_conntrack_zone *zone,
  		const struct net *net)

  {
  	struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(h);
  
  	/* A conntrack can be recreated with the equal tuple,
  	 * so we need to check that the conntrack is confirmed
  	 */
  	return nf_ct_tuple_equal(tuple, &h->tuple) &&

  	       nf_ct_zone_equal(ct, zone, NF_CT_DIRECTION(h)) &&

  	       nf_ct_is_confirmed(ct) &&
  	       net_eq(net, nf_ct_net(ct));

  }

  /* must be called with rcu read lock held */
  void nf_conntrack_get_ht(struct hlist_nulls_head **hash, unsigned int *hsize)
  {
  	struct hlist_nulls_head *hptr;
  	unsigned int sequence, hsz;
  
  	do {
  		sequence = read_seqcount_begin(&nf_conntrack_generation);
  		hsz = nf_conntrack_htable_size;
  		hptr = nf_conntrack_hash;
  	} while (read_seqcount_retry(&nf_conntrack_generation, sequence));
  
  	*hash = hptr;
  	*hsize = hsz;
  }
  EXPORT_SYMBOL_GPL(nf_conntrack_get_ht);

  /*
   * Warning :
   * - Caller must take a reference on returned object
   *   and recheck nf_ct_tuple_equal(tuple, &h->tuple)

   */

  static struct nf_conntrack_tuple_hash *

  ____nf_conntrack_find(struct net *net, const struct nf_conntrack_zone *zone,

  		      const struct nf_conntrack_tuple *tuple, u32 hash)

  {
  	struct nf_conntrack_tuple_hash *h;

  	struct hlist_nulls_head *ct_hash;

  	struct hlist_nulls_node *n;

  	unsigned int bucket, sequence;

  begin:

  	do {
  		sequence = read_seqcount_begin(&nf_conntrack_generation);

  		bucket = scale_hash(hash);
  		ct_hash = nf_conntrack_hash;

  	} while (read_seqcount_retry(&nf_conntrack_generation, sequence));
  
  	hlist_nulls_for_each_entry_rcu(h, n, &ct_hash[bucket], hnnode) {

  		if (nf_ct_key_equal(h, tuple, zone, net)) {

  			NF_CT_STAT_INC_ATOMIC(net, found);

  			return h;
  		}

  		NF_CT_STAT_INC_ATOMIC(net, searched);

  	}

  	/*
  	 * 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(n) != bucket) {

  		NF_CT_STAT_INC_ATOMIC(net, search_restart);

  		goto begin;

  	}

  
  	return NULL;
  }

  /* Find a connection corresponding to a tuple. */

  static struct nf_conntrack_tuple_hash *

  __nf_conntrack_find_get(struct net *net, const struct nf_conntrack_zone *zone,

  			const struct nf_conntrack_tuple *tuple, u32 hash)

  {
  	struct nf_conntrack_tuple_hash *h;

  	struct nf_conn *ct;

  	rcu_read_lock();

  begin:

  	h = ____nf_conntrack_find(net, zone, tuple, hash);

  	if (h) {
  		ct = nf_ct_tuplehash_to_ctrack(h);

  		if (unlikely(nf_ct_is_dying(ct) ||
  			     !atomic_inc_not_zero(&ct->ct_general.use)))

  			h = NULL;

  		else {

  			if (unlikely(!nf_ct_key_equal(h, tuple, zone, net))) {

  				nf_ct_put(ct);
  				goto begin;
  			}
  		}

  	}
  	rcu_read_unlock();

  
  	return h;
  }

  
  struct nf_conntrack_tuple_hash *

  nf_conntrack_find_get(struct net *net, const struct nf_conntrack_zone *zone,

  		      const struct nf_conntrack_tuple *tuple)
  {
  	return __nf_conntrack_find_get(net, zone, tuple,

  				       hash_conntrack_raw(tuple, net));

  }

  EXPORT_SYMBOL_GPL(nf_conntrack_find_get);

  static void __nf_conntrack_hash_insert(struct nf_conn *ct,
  				       unsigned int hash,

  				       unsigned int reply_hash)

  {

  	hlist_nulls_add_head_rcu(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode,

  			   &nf_conntrack_hash[hash]);

  	hlist_nulls_add_head_rcu(&ct->tuplehash[IP_CT_DIR_REPLY].hnnode,

  			   &nf_conntrack_hash[reply_hash]);

  }

  int
  nf_conntrack_hash_check_insert(struct nf_conn *ct)

  {

  	const struct nf_conntrack_zone *zone;

  	struct net *net = nf_ct_net(ct);

  	unsigned int hash, reply_hash;

  	struct nf_conntrack_tuple_hash *h;
  	struct hlist_nulls_node *n;

  	unsigned int sequence;

  	zone = nf_ct_zone(ct);

  	local_bh_disable();
  	do {

  		sequence = read_seqcount_begin(&nf_conntrack_generation);

  		hash = hash_conntrack(net,

  				      &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);

  		reply_hash = hash_conntrack(net,

  					   &ct->tuplehash[IP_CT_DIR_REPLY].tuple);
  	} while (nf_conntrack_double_lock(net, hash, reply_hash, sequence));

  
  	/* See if there's one in the list already, including reverse */

  	hlist_nulls_for_each_entry(h, n, &nf_conntrack_hash[hash], hnnode)

  		if (nf_ct_key_equal(h, &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple,

  				    zone, net))

  			goto out;

  	hlist_nulls_for_each_entry(h, n, &nf_conntrack_hash[reply_hash], hnnode)

  		if (nf_ct_key_equal(h, &ct->tuplehash[IP_CT_DIR_REPLY].tuple,

  				    zone, net))

  			goto out;

  	add_timer(&ct->timeout);

  	smp_wmb();
  	/* The caller holds a reference to this object */
  	atomic_set(&ct->ct_general.use, 2);

  	__nf_conntrack_hash_insert(ct, hash, reply_hash);

  	nf_conntrack_double_unlock(hash, reply_hash);

  	NF_CT_STAT_INC(net, insert);

  	local_bh_enable();

  	return 0;
  
  out:

  	nf_conntrack_double_unlock(hash, reply_hash);

  	NF_CT_STAT_INC(net, insert_failed);

  	local_bh_enable();

  	return -EEXIST;

  }

  EXPORT_SYMBOL_GPL(nf_conntrack_hash_check_insert);

  static inline void nf_ct_acct_update(struct nf_conn *ct,
  				     enum ip_conntrack_info ctinfo,
  				     unsigned int len)
  {
  	struct nf_conn_acct *acct;
  
  	acct = nf_conn_acct_find(ct);
  	if (acct) {
  		struct nf_conn_counter *counter = acct->counter;
  
  		atomic64_inc(&counter[CTINFO2DIR(ctinfo)].packets);
  		atomic64_add(len, &counter[CTINFO2DIR(ctinfo)].bytes);
  	}
  }

  static void nf_ct_acct_merge(struct nf_conn *ct, enum ip_conntrack_info ctinfo,
  			     const struct nf_conn *loser_ct)
  {
  	struct nf_conn_acct *acct;
  
  	acct = nf_conn_acct_find(loser_ct);
  	if (acct) {
  		struct nf_conn_counter *counter = acct->counter;

  		unsigned int bytes;
  
  		/* u32 should be fine since we must have seen one packet. */
  		bytes = atomic64_read(&counter[CTINFO2DIR(ctinfo)].bytes);
  		nf_ct_acct_update(ct, ctinfo, bytes);
  	}
  }
  
  /* Resolve race on insertion if this protocol allows this. */
  static int nf_ct_resolve_clash(struct net *net, struct sk_buff *skb,
  			       enum ip_conntrack_info ctinfo,
  			       struct nf_conntrack_tuple_hash *h)
  {
  	/* This is the conntrack entry already in hashes that won race. */
  	struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(h);
  	struct nf_conntrack_l4proto *l4proto;
  
  	l4proto = __nf_ct_l4proto_find(nf_ct_l3num(ct), nf_ct_protonum(ct));
  	if (l4proto->allow_clash &&
  	    !nf_ct_is_dying(ct) &&
  	    atomic_inc_not_zero(&ct->ct_general.use)) {
  		nf_ct_acct_merge(ct, ctinfo, (struct nf_conn *)skb->nfct);
  		nf_conntrack_put(skb->nfct);
  		/* Assign conntrack already in hashes to this skbuff. Don't
  		 * modify skb->nfctinfo to ensure consistent stateful filtering.
  		 */
  		skb->nfct = &ct->ct_general;
  		return NF_ACCEPT;
  	}
  	NF_CT_STAT_INC(net, drop);
  	return NF_DROP;
  }

  /* Confirm a connection given skb; places it in hash table */
  int

  __nf_conntrack_confirm(struct sk_buff *skb)

  {

  	const struct nf_conntrack_zone *zone;

  	unsigned int hash, reply_hash;

  	struct nf_conntrack_tuple_hash *h;

  	struct nf_conn *ct;

  	struct nf_conn_help *help;

  	struct nf_conn_tstamp *tstamp;

  	struct hlist_nulls_node *n;

  	enum ip_conntrack_info ctinfo;

  	struct net *net;

  	unsigned int sequence;

  	int ret = NF_DROP;

  	ct = nf_ct_get(skb, &ctinfo);

  	net = nf_ct_net(ct);

  
  	/* ipt_REJECT uses nf_conntrack_attach to attach related
  	   ICMP/TCP RST packets in other direction.  Actual packet
  	   which created connection will be IP_CT_NEW or for an
  	   expected connection, IP_CT_RELATED. */
  	if (CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL)
  		return NF_ACCEPT;

  	zone = nf_ct_zone(ct);

  	local_bh_disable();
  
  	do {

  		sequence = read_seqcount_begin(&nf_conntrack_generation);

  		/* reuse the hash saved before */
  		hash = *(unsigned long *)&ct->tuplehash[IP_CT_DIR_REPLY].hnnode.pprev;

  		hash = scale_hash(hash);

  		reply_hash = hash_conntrack(net,

  					   &ct->tuplehash[IP_CT_DIR_REPLY].tuple);
  
  	} while (nf_conntrack_double_lock(net, hash, reply_hash, sequence));

  
  	/* We're not in hash table, and we refuse to set up related

  	 * connections for unconfirmed conns.  But packet copies and
  	 * REJECT will give spurious warnings here.
  	 */

  	/* NF_CT_ASSERT(atomic_read(&ct->ct_general.use) == 1); */

  	/* No external references means no one else could have

  	 * confirmed us.
  	 */

  	NF_CT_ASSERT(!nf_ct_is_confirmed(ct));

  	pr_debug("Confirming conntrack %p
  ", ct);

  	/* We have to check the DYING flag after unlink to prevent
  	 * a race against nf_ct_get_next_corpse() possibly called from
  	 * user context, else we insert an already 'dead' hash, blocking
  	 * further use of that particular connection -JM.
  	 */
  	nf_ct_del_from_dying_or_unconfirmed_list(ct);

  	if (unlikely(nf_ct_is_dying(ct))) {
  		nf_ct_add_to_dying_list(ct);
  		goto dying;
  	}

  	/* See if there's one in the list already, including reverse:
  	   NAT could have grabbed it without realizing, since we're
  	   not in the hash.  If there is, we lost race. */

  	hlist_nulls_for_each_entry(h, n, &nf_conntrack_hash[hash], hnnode)

  		if (nf_ct_key_equal(h, &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple,

  				    zone, net))

  			goto out;

  	hlist_nulls_for_each_entry(h, n, &nf_conntrack_hash[reply_hash], hnnode)

  		if (nf_ct_key_equal(h, &ct->tuplehash[IP_CT_DIR_REPLY].tuple,

  				    zone, net))

  			goto out;

  	/* Timer relative to confirmation time, not original
  	   setting time, otherwise we'd get timer wrap in
  	   weird delay cases. */
  	ct->timeout.expires += jiffies;
  	add_timer(&ct->timeout);
  	atomic_inc(&ct->ct_general.use);

  	ct->status |= IPS_CONFIRMED;

  	/* set conntrack timestamp, if enabled. */
  	tstamp = nf_conn_tstamp_find(ct);
  	if (tstamp) {
  		if (skb->tstamp.tv64 == 0)

  			__net_timestamp(skb);

  
  		tstamp->start = ktime_to_ns(skb->tstamp);
  	}

  	/* Since the lookup is lockless, hash insertion must be done after
  	 * starting the timer and setting the CONFIRMED bit. The RCU barriers
  	 * guarantee that no other CPU can find the conntrack before the above
  	 * stores are visible.
  	 */

  	__nf_conntrack_hash_insert(ct, hash, reply_hash);

  	nf_conntrack_double_unlock(hash, reply_hash);

  	NF_CT_STAT_INC(net, insert);

  	local_bh_enable();

  	help = nfct_help(ct);
  	if (help && help->helper)

  		nf_conntrack_event_cache(IPCT_HELPER, ct);

  	nf_conntrack_event_cache(master_ct(ct) ?

  				 IPCT_RELATED : IPCT_NEW, ct);

  	return NF_ACCEPT;

  out:

  	nf_ct_add_to_dying_list(ct);

  	ret = nf_ct_resolve_clash(net, skb, ctinfo, h);
  dying:

  	nf_conntrack_double_unlock(hash, reply_hash);

  	NF_CT_STAT_INC(net, insert_failed);

  	local_bh_enable();

  	return ret;

  }

  EXPORT_SYMBOL_GPL(__nf_conntrack_confirm);

  
  /* Returns true if a connection correspondings to the tuple (required
     for NAT). */
  int
  nf_conntrack_tuple_taken(const struct nf_conntrack_tuple *tuple,
  			 const struct nf_conn *ignored_conntrack)
  {

  	struct net *net = nf_ct_net(ignored_conntrack);

  	const struct nf_conntrack_zone *zone;

  	struct nf_conntrack_tuple_hash *h;

  	struct hlist_nulls_head *ct_hash;
  	unsigned int hash, sequence;

  	struct hlist_nulls_node *n;

  	struct nf_conn *ct;

  
  	zone = nf_ct_zone(ignored_conntrack);

  	rcu_read_lock();

  	do {
  		sequence = read_seqcount_begin(&nf_conntrack_generation);
  		hash = hash_conntrack(net, tuple);

  		ct_hash = nf_conntrack_hash;

  	} while (read_seqcount_retry(&nf_conntrack_generation, sequence));
  
  	hlist_nulls_for_each_entry_rcu(h, n, &ct_hash[hash], hnnode) {

  		ct = nf_ct_tuplehash_to_ctrack(h);
  		if (ct != ignored_conntrack &&

  		    nf_ct_key_equal(h, tuple, zone, net)) {

  			NF_CT_STAT_INC_ATOMIC(net, found);
  			rcu_read_unlock();

  			return 1;
  		}

  		NF_CT_STAT_INC_ATOMIC(net, searched);

  	}

  	rcu_read_unlock();

  	return 0;

  }

  EXPORT_SYMBOL_GPL(nf_conntrack_tuple_taken);

  #define NF_CT_EVICTION_RANGE	8

  /* There's a small race here where we may free a just-assured
     connection.  Too bad: we're in trouble anyway. */

  static noinline int early_drop(struct net *net, unsigned int _hash)

  {

  	/* Use oldest entry, which is roughly LRU */

  	struct nf_conntrack_tuple_hash *h;

  	struct nf_conn *tmp;

  	struct hlist_nulls_node *n;

  	unsigned int i, hash, sequence;
  	struct nf_conn *ct = NULL;

  	spinlock_t *lockp;

  	bool ret = false;
  
  	i = 0;

  	local_bh_disable();
  restart:

  	sequence = read_seqcount_begin(&nf_conntrack_generation);

  	for (; i < NF_CT_EVICTION_RANGE; i++) {
  		hash = scale_hash(_hash++);

  		lockp = &nf_conntrack_locks[hash % CONNTRACK_LOCKS];

  		nf_conntrack_lock(lockp);

  		if (read_seqcount_retry(&nf_conntrack_generation, sequence)) {

  			spin_unlock(lockp);
  			goto restart;
  		}

  		hlist_nulls_for_each_entry_rcu(h, n, &nf_conntrack_hash[hash],
  					       hnnode) {

  			tmp = nf_ct_tuplehash_to_ctrack(h);

  
  			if (test_bit(IPS_ASSURED_BIT, &tmp->status) ||
  			    !net_eq(nf_ct_net(tmp), net) ||
  			    nf_ct_is_dying(tmp))
  				continue;
  
  			if (atomic_inc_not_zero(&tmp->ct_general.use)) {

  				ct = tmp;

  				break;
  			}

  		}

  		spin_unlock(lockp);

  		if (ct)

  			break;

  	}

  	local_bh_enable();

  
  	if (!ct)

  		return false;

  	/* kill only if in same netns -- might have moved due to
  	 * SLAB_DESTROY_BY_RCU rules
  	 */
  	if (net_eq(nf_ct_net(ct), net) && del_timer(&ct->timeout)) {

  		if (nf_ct_delete(ct, 0, 0)) {

  			NF_CT_STAT_INC_ATOMIC(net, early_drop);

  			ret = true;

  		}

  	}

  	nf_ct_put(ct);

  	return ret;

  }

  static struct nf_conn *

  __nf_conntrack_alloc(struct net *net,
  		     const struct nf_conntrack_zone *zone,

  		     const struct nf_conntrack_tuple *orig,
  		     const struct nf_conntrack_tuple *repl,
  		     gfp_t gfp, u32 hash)

  {

  	struct nf_conn *ct;

  	/* We don't want any race condition at early drop stage */

  	atomic_inc(&net->ct.count);

  	if (nf_conntrack_max &&

  	    unlikely(atomic_read(&net->ct.count) > nf_conntrack_max)) {

  		if (!early_drop(net, hash)) {

  			atomic_dec(&net->ct.count);

  			net_warn_ratelimited("nf_conntrack: table full, dropping packet
  ");

  			return ERR_PTR(-ENOMEM);
  		}
  	}

  	/*
  	 * Do not use kmem_cache_zalloc(), as this cache uses
  	 * SLAB_DESTROY_BY_RCU.
  	 */

  	ct = kmem_cache_alloc(nf_conntrack_cachep, gfp);

  	if (ct == NULL)
  		goto out;

  	spin_lock_init(&ct->lock);

  	ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple = *orig;

  	ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode.pprev = NULL;

  	ct->tuplehash[IP_CT_DIR_REPLY].tuple = *repl;

  	/* save hash for reusing when confirming */
  	*(unsigned long *)(&ct->tuplehash[IP_CT_DIR_REPLY].hnnode.pprev) = hash;

  	ct->status = 0;

  	/* Don't set timer yet: wait for confirmation */

  	setup_timer(&ct->timeout, death_by_timeout, (unsigned long)ct);

  	write_pnet(&ct->ct_net, net);

  	memset(&ct->__nfct_init_offset[0], 0,
  	       offsetof(struct nf_conn, proto) -
  	       offsetof(struct nf_conn, __nfct_init_offset[0]));

  	nf_ct_zone_add(ct, zone);

  	/* Because we use RCU lookups, we set ct_general.use to zero before
  	 * this is inserted in any list.

  	 */

  	atomic_set(&ct->ct_general.use, 0);

  	return ct;

  out:
  	atomic_dec(&net->ct.count);

  	return ERR_PTR(-ENOMEM);

  }

  struct nf_conn *nf_conntrack_alloc(struct net *net,
  				   const struct nf_conntrack_zone *zone,

  				   const struct nf_conntrack_tuple *orig,
  				   const struct nf_conntrack_tuple *repl,
  				   gfp_t gfp)
  {
  	return __nf_conntrack_alloc(net, zone, orig, repl, gfp, 0);
  }

  EXPORT_SYMBOL_GPL(nf_conntrack_alloc);

  void nf_conntrack_free(struct nf_conn *ct)

  {

  	struct net *net = nf_ct_net(ct);

  	/* A freed object has refcnt == 0, that's
  	 * the golden rule for SLAB_DESTROY_BY_RCU
  	 */
  	NF_CT_ASSERT(atomic_read(&ct->ct_general.use) == 0);

  	nf_ct_ext_destroy(ct);

  	nf_ct_ext_free(ct);

  	kmem_cache_free(nf_conntrack_cachep, ct);

  	smp_mb__before_atomic();

  	atomic_dec(&net->ct.count);

  }

  EXPORT_SYMBOL_GPL(nf_conntrack_free);

  /* Allocate a new conntrack: we return -ENOMEM if classification
     failed due to stress.  Otherwise it really is unclassifiable. */
  static struct nf_conntrack_tuple_hash *

  init_conntrack(struct net *net, struct nf_conn *tmpl,

  	       const struct nf_conntrack_tuple *tuple,

  	       struct nf_conntrack_l3proto *l3proto,

  	       struct nf_conntrack_l4proto *l4proto,

  	       struct sk_buff *skb,

  	       unsigned int dataoff, u32 hash)

  {

  	struct nf_conn *ct;

  	struct nf_conn_help *help;

  	struct nf_conntrack_tuple repl_tuple;

  	struct nf_conntrack_ecache *ecache;

  	struct nf_conntrack_expect *exp = NULL;

  	const struct nf_conntrack_zone *zone;

  	struct nf_conn_timeout *timeout_ext;

  	struct nf_conntrack_zone tmp;

  	unsigned int *timeouts;

  	if (!nf_ct_invert_tuple(&repl_tuple, tuple, l3proto, l4proto)) {

  		pr_debug("Can't invert tuple.
  ");

  		return NULL;
  	}

  	zone = nf_ct_zone_tmpl(tmpl, skb, &tmp);

  	ct = __nf_conntrack_alloc(net, zone, tuple, &repl_tuple, GFP_ATOMIC,
  				  hash);

  	if (IS_ERR(ct))

  		return (struct nf_conntrack_tuple_hash *)ct;

  	if (tmpl && nfct_synproxy(tmpl)) {
  		nfct_seqadj_ext_add(ct);
  		nfct_synproxy_ext_add(ct);
  	}

  	timeout_ext = tmpl ? nf_ct_timeout_find(tmpl) : NULL;

  	if (timeout_ext) {
  		timeouts = nf_ct_timeout_data(timeout_ext);
  		if (unlikely(!timeouts))
  			timeouts = l4proto->get_timeouts(net);
  	} else {

  		timeouts = l4proto->get_timeouts(net);

  	}

  	if (!l4proto->new(ct, skb, dataoff, timeouts)) {

  		nf_conntrack_free(ct);

  		pr_debug("can't track with proto module
  ");

  		return NULL;
  	}

  	if (timeout_ext)

  		nf_ct_timeout_ext_add(ct, rcu_dereference(timeout_ext->timeout),
  				      GFP_ATOMIC);

  	nf_ct_acct_ext_add(ct, GFP_ATOMIC);

  	nf_ct_tstamp_ext_add(ct, GFP_ATOMIC);

  	nf_ct_labels_ext_add(ct);

  
  	ecache = tmpl ? nf_ct_ecache_find(tmpl) : NULL;
  	nf_ct_ecache_ext_add(ct, ecache ? ecache->ctmask : 0,
  				 ecache ? ecache->expmask : 0,
  			     GFP_ATOMIC);

  	local_bh_disable();
  	if (net->ct.expect_count) {
  		spin_lock(&nf_conntrack_expect_lock);
  		exp = nf_ct_find_expectation(net, zone, tuple);
  		if (exp) {

  			pr_debug("expectation arrives ct=%p exp=%p
  ",

  				 ct, exp);
  			/* Welcome, Mr. Bond.  We've been expecting you... */
  			__set_bit(IPS_EXPECTED_BIT, &ct->status);
  			/* exp->master safe, refcnt bumped in nf_ct_find_expectation */
  			ct->master = exp->master;
  			if (exp->helper) {
  				help = nf_ct_helper_ext_add(ct, exp->helper,
  							    GFP_ATOMIC);
  				if (help)
  					rcu_assign_pointer(help->helper, exp->helper);
  			}

  #ifdef CONFIG_NF_CONNTRACK_MARK

  			ct->mark = exp->master->mark;

  #endif

  #ifdef CONFIG_NF_CONNTRACK_SECMARK

  			ct->secmark = exp->master->secmark;

  #endif

  			NF_CT_STAT_INC(net, expect_new);
  		}
  		spin_unlock(&nf_conntrack_expect_lock);
  	}
  	if (!exp) {

  		__nf_ct_try_assign_helper(ct, tmpl, GFP_ATOMIC);

  		NF_CT_STAT_INC(net, new);

  	}

  	/* Now it is inserted into the unconfirmed list, bump refcount */
  	nf_conntrack_get(&ct->ct_general);

  	nf_ct_add_to_unconfirmed_list(ct);

  	local_bh_enable();

  
  	if (exp) {
  		if (exp->expectfn)

  			exp->expectfn(ct, exp);

  		nf_ct_expect_put(exp);

  	}

  	return &ct->tuplehash[IP_CT_DIR_ORIGINAL];

  }
  
  /* On success, returns conntrack ptr, sets skb->nfct and ctinfo */
  static inline struct nf_conn *

  resolve_normal_ct(struct net *net, struct nf_conn *tmpl,

  		  struct sk_buff *skb,

  		  unsigned int dataoff,
  		  u_int16_t l3num,
  		  u_int8_t protonum,
  		  struct nf_conntrack_l3proto *l3proto,

  		  struct nf_conntrack_l4proto *l4proto,

  		  int *set_reply,

  		  enum ip_conntrack_info *ctinfo)

  {

  	const struct nf_conntrack_zone *zone;

  	struct nf_conntrack_tuple tuple;
  	struct nf_conntrack_tuple_hash *h;

  	struct nf_conntrack_zone tmp;

  	struct nf_conn *ct;

  	u32 hash;

  	if (!nf_ct_get_tuple(skb, skb_network_offset(skb),

  			     dataoff, l3num, protonum, net, &tuple, l3proto,

  			     l4proto)) {

  		pr_debug("Can't get tuple
  ");

  		return NULL;
  	}
  
  	/* look for tuple match */

  	zone = nf_ct_zone_tmpl(tmpl, skb, &tmp);

  	hash = hash_conntrack_raw(&tuple, net);

  	h = __nf_conntrack_find_get(net, zone, &tuple, hash);

  	if (!h) {

  		h = init_conntrack(net, tmpl, &tuple, l3proto, l4proto,

  				   skb, dataoff, hash);

  		if (!h)
  			return NULL;
  		if (IS_ERR(h))
  			return (void *)h;
  	}
  	ct = nf_ct_tuplehash_to_ctrack(h);
  
  	/* It exists; we have (non-exclusive) reference. */
  	if (NF_CT_DIRECTION(h) == IP_CT_DIR_REPLY) {

  		*ctinfo = IP_CT_ESTABLISHED_REPLY;

  		/* Please set reply bit if this packet OK */
  		*set_reply = 1;
  	} else {
  		/* Once we've had two way comms, always ESTABLISHED. */
  		if (test_bit(IPS_SEEN_REPLY_BIT, &ct->status)) {

  			pr_debug("normal packet for %p
  ", ct);

  			*ctinfo = IP_CT_ESTABLISHED;
  		} else if (test_bit(IPS_EXPECTED_BIT, &ct->status)) {

  			pr_debug("related packet for %p
  ", ct);

  			*ctinfo = IP_CT_RELATED;
  		} else {

  			pr_debug("new packet for %p
  ", ct);

  			*ctinfo = IP_CT_NEW;
  		}
  		*set_reply = 0;
  	}
  	skb->nfct = &ct->ct_general;
  	skb->nfctinfo = *ctinfo;
  	return ct;
  }
  
  unsigned int

  nf_conntrack_in(struct net *net, u_int8_t pf, unsigned int hooknum,
  		struct sk_buff *skb)

  {

  	struct nf_conn *ct, *tmpl = NULL;

  	enum ip_conntrack_info ctinfo;
  	struct nf_conntrack_l3proto *l3proto;

  	struct nf_conntrack_l4proto *l4proto;

  	unsigned int *timeouts;

  	unsigned int dataoff;
  	u_int8_t protonum;
  	int set_reply = 0;
  	int ret;

  	if (skb->nfct) {

  		/* Previously seen (loopback or untracked)?  Ignore. */
  		tmpl = (struct nf_conn *)skb->nfct;
  		if (!nf_ct_is_template(tmpl)) {
  			NF_CT_STAT_INC_ATOMIC(net, ignore);
  			return NF_ACCEPT;
  		}
  		skb->nfct = NULL;

  	}

  	/* rcu_read_lock()ed by nf_hook_slow */

  	l3proto = __nf_ct_l3proto_find(pf);

  	ret = l3proto->get_l4proto(skb, skb_network_offset(skb),

  				   &dataoff, &protonum);
  	if (ret <= 0) {

  		pr_debug("not prepared to track yet or error occurred
  ");

  		NF_CT_STAT_INC_ATOMIC(net, error);
  		NF_CT_STAT_INC_ATOMIC(net, invalid);

  		ret = -ret;
  		goto out;

  	}

  	l4proto = __nf_ct_l4proto_find(pf, protonum);

  
  	/* It may be an special packet, error, unclean...
  	 * inverse of the return code tells to the netfilter
  	 * core what to do with the packet. */

  	if (l4proto->error != NULL) {

  		ret = l4proto->error(net, tmpl, skb, dataoff, &ctinfo,
  				     pf, hooknum);

  		if (ret <= 0) {

  			NF_CT_STAT_INC_ATOMIC(net, error);
  			NF_CT_STAT_INC_ATOMIC(net, invalid);

  			ret = -ret;
  			goto out;

  		}

  		/* ICMP[v6] protocol trackers may assign one conntrack. */
  		if (skb->nfct)
  			goto out;

  	}

  	ct = resolve_normal_ct(net, tmpl, skb, dataoff, pf, protonum,

  			       l3proto, l4proto, &set_reply, &ctinfo);

  	if (!ct) {
  		/* Not valid part of a connection */

  		NF_CT_STAT_INC_ATOMIC(net, invalid);

  		ret = NF_ACCEPT;
  		goto out;

  	}
  
  	if (IS_ERR(ct)) {
  		/* Too stressed to deal. */

  		NF_CT_STAT_INC_ATOMIC(net, drop);

  		ret = NF_DROP;
  		goto out;

  	}

  	NF_CT_ASSERT(skb->nfct);

  	/* Decide what timeout policy we want to apply to this flow. */

  	timeouts = nf_ct_timeout_lookup(net, ct, l4proto);