/* 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);

struct conntrack_gc_work {
        struct delayed_work     dwork;
        u32                     last_bucket;
        bool                    exiting;
        long                    next_gc_run;
};

static __read_mostly struct kmem_cache *nf_conntrack_cachep;
static __read_mostly spinlock_t nf_conntrack_locks_all_lock;
static __read_mostly DEFINE_SPINLOCK(nf_conntrack_locks_all_lock);
static __read_mostly bool nf_conntrack_locks_all;

/* every gc cycle scans at most 1/GC_MAX_BUCKETS_DIV part of table */
#define GC_MAX_BUCKETS_DIV      64u
/* upper bound of scan intervals */
#define GC_INTERVAL_MAX         (2 * HZ)
/* maximum conntracks to evict per gc run */
#define GC_MAX_EVICTS           256u

static struct conntrack_gc_work conntrack_gc_work;

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

                /*
                 * Order the 'nf_conntrack_locks_all' load vs. the
                 * spin_unlock_wait() loads below, to ensure
                 * that 'nf_conntrack_locks_all_lock' is indeed held:
                 */
                smp_rmb(); /* spin_lock(&nf_conntrack_locks_all_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;

        /*
         * Order the above store of 'nf_conntrack_locks_all' against
         * the spin_unlock_wait() loads below, such that if
         * nf_conntrack_lock() observes 'nf_conntrack_locks_all'
         * we must observe nf_conntrack_locks[] held:
         */
        smp_mb(); /* spin_lock(&nf_conntrack_locks_all_lock) */

        for (i = 0; i < CONNTRACK_LOCKS; i++) {
                spin_unlock_wait(&nf_conntrack_locks[i]);
        }
}

static void nf_conntrack_all_unlock(void)
{
        /*
         * All prior stores must be complete before we clear
         * 'nf_conntrack_locks_all'. Otherwise nf_conntrack_lock()
         * might observe the false value but not the entire
         * critical section:
         */
        smp_store_release(&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;
seqcount_t nf_conntrack_generation __read_mostly;

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)\n", 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 nf_conntrack_l4proto *l4proto;

        pr_debug("destroy_conntrack(%p)\n", ct);
        NF_CT_ASSERT(atomic_read(&nfct->use) == 0);

        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);

        local_bh_enable();

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

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

        local_bh_enable();
}

bool nf_ct_delete(struct nf_conn *ct, u32 portid, int report)
{
        struct nf_conn_tstamp *tstamp;

        if (test_and_set_bit(IPS_DYING_BIT, &ct->status))
                return false;

        tstamp = nf_conn_tstamp_find(ct);
        if (tstamp && tstamp->stop == 0)
                tstamp->stop = ktime_get_real_ns();

        if (nf_conntrack_event_report(IPCT_DESTROY, ct,
                                    portid, report) < 0) {
                /* destroy event was not delivered. nf_ct_put will
                 * be done by event cache worker on redelivery.
                 */
                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));
        nf_ct_delete_from_lists(ct);
        nf_ct_put(ct);
        return true;
}
EXPORT_SYMBOL_GPL(nf_ct_delete);

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));
}

/* caller must hold rcu readlock and none of the nf_conntrack_locks */
static void nf_ct_gc_expired(struct nf_conn *ct)
{
        if (!atomic_inc_not_zero(&ct->ct_general.use))
                return;

        if (nf_ct_should_gc(ct))
                nf_ct_kill(ct);

        nf_ct_put(ct);
}

/*
 * 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, hsize;

begin:
        nf_conntrack_get_ht(&ct_hash, &hsize);
        bucket = reciprocal_scale(hash, hsize);

        hlist_nulls_for_each_entry_rcu(h, n, &ct_hash[bucket], hnnode) {
                struct nf_conn *ct;

                ct = nf_ct_tuplehash_to_ctrack(h);
                if (nf_ct_is_expired(ct)) {
                        nf_ct_gc_expired(ct);
                        continue;
                }

                if (nf_ct_is_dying(ct))
                        continue;

                if (nf_ct_key_equal(h, tuple, zone, net))
                        return h;
        }
        /*
         * 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;

        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 &&
            !nfct_nat(ct) &&
            !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\n", 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 += nfct_time_stamp;
        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);
        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, hsize;
        struct hlist_nulls_node *n;
        struct nf_conn *ct;

        zone = nf_ct_zone(ignored_conntrack);

        rcu_read_lock();
 begin:
        nf_conntrack_get_ht(&ct_hash, &hsize);
        hash = __hash_conntrack(net, tuple, hsize);

        hlist_nulls_for_each_entry_rcu(h, n, &ct_hash[hash], hnnode) {
                ct = nf_ct_tuplehash_to_ctrack(h);

                if (ct == ignored_conntrack)
                        continue;

                if (nf_ct_is_expired(ct)) {
                        nf_ct_gc_expired(ct);
                        continue;
                }

                if (nf_ct_key_equal(h, tuple, zone, net)) {
                        NF_CT_STAT_INC_ATOMIC(net, found);
                        rcu_read_unlock();
                        return 1;
                }
        }

        if (get_nulls_value(n) != hash) {
                NF_CT_STAT_INC_ATOMIC(net, search_restart);
                goto begin;
        }

        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 unsigned int early_drop_list(struct net *net,
                                    struct hlist_nulls_head *head)
{
        struct nf_conntrack_tuple_hash *h;
        struct hlist_nulls_node *n;
        unsigned int drops = 0;
        struct nf_conn *tmp;

        hlist_nulls_for_each_entry_rcu(h, n, head, hnnode) {
                tmp = nf_ct_tuplehash_to_ctrack(h);

                if (nf_ct_is_expired(tmp)) {
                        nf_ct_gc_expired(tmp);
                        continue;
                }

                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))
                        continue;

                /* kill only if still in same netns -- might have moved due to
                 * SLAB_DESTROY_BY_RCU rules.
                 *
                 * We steal the timer reference.  If that fails timer has
                 * already fired or someone else deleted it. Just drop ref
                 * and move to next entry.
                 */
                if (net_eq(nf_ct_net(tmp), net) &&
                    nf_ct_is_confirmed(tmp) &&
                    nf_ct_delete(tmp, 0, 0))
                        drops++;

                nf_ct_put(tmp);
        }

        return drops;
}

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

        for (i = 0; i < NF_CT_EVICTION_RANGE; i++) {
                struct hlist_nulls_head *ct_hash;
                unsigned int hash, hsize, drops;

                rcu_read_lock();
                nf_conntrack_get_ht(&ct_hash, &hsize);
                hash = reciprocal_scale(_hash++, hsize);

                drops = early_drop_list(net, &ct_hash[hash]);
                rcu_read_unlock();

                if (drops) {
                        NF_CT_STAT_ADD_ATOMIC(net, early_drop, drops);
                        return true;
                }
        }

        return false;
}

static void gc_worker(struct work_struct *work)
{
        unsigned int i, goal, buckets = 0, expired_count = 0;
        struct conntrack_gc_work *gc_work;
        unsigned int ratio, scanned = 0;
        unsigned long next_run;

        gc_work = container_of(work, struct conntrack_gc_work, dwork.work);

        goal = nf_conntrack_htable_size / GC_MAX_BUCKETS_DIV;
        i = gc_work->last_bucket;

        do {
                struct nf_conntrack_tuple_hash *h;
                struct hlist_nulls_head *ct_hash;
                struct hlist_nulls_node *n;
                unsigned int hashsz;
                struct nf_conn *tmp;

                i++;
                rcu_read_lock();

                nf_conntrack_get_ht(&ct_hash, &hashsz);
                if (i >= hashsz)
                        i = 0;

                hlist_nulls_for_each_entry_rcu(h, n, &ct_hash[i], hnnode) {
                        tmp = nf_ct_tuplehash_to_ctrack(h);

                        scanned++;
                        if (nf_ct_is_expired(tmp)) {
                                nf_ct_gc_expired(tmp);
                                expired_count++;
                                continue;
                        }
                }

                /* could check get_nulls_value() here and restart if ct
                 * was moved to another chain.  But given gc is best-effort
                 * we will just continue with next hash slot.
                 */
                rcu_read_unlock();
                cond_resched_rcu_qs();
        } while (++buckets < goal &&
                 expired_count < GC_MAX_EVICTS);

        if (gc_work->exiting)
                return;

        /*
         * Eviction will normally happen from the packet path, and not
         * from this gc worker.
         *
         * This worker is only here to reap expired entries when system went
         * idle after a busy period.
         *
         * The heuristics below are supposed to balance conflicting goals:
         *
         * 1. Minimize time until we notice a stale entry
         * 2. Maximize scan intervals to not waste cycles
         *
         * Normally, expired_count will be 0, this increases the next_run time

         * to priorize 2) above.
         *
         * As soon as a timed-out entry is found, move towards 1) and increase
         * the scan frequency.
         * In case we have lots of evictions next scan is done immediately.
         */
        ratio = scanned ? expired_count * 100 / scanned : 0;
        if (ratio >= 90 || expired_count == GC_MAX_EVICTS) {
                gc_work->next_gc_run = 0;
                next_run = 0;
        } else if (expired_count) {
                gc_work->next_gc_run /= 2U;
                next_run = msecs_to_jiffies(1);
        } else {
                if (gc_work->next_gc_run < GC_INTERVAL_MAX)
                        gc_work->next_gc_run += msecs_to_jiffies(1);

                next_run = gc_work->next_gc_run;
        }

        gc_work->last_bucket = i;
        queue_delayed_work(system_long_wq, &gc_work->dwork, next_run);
}

static void conntrack_gc_work_init(struct conntrack_gc_work *gc_work)
{
        INIT_DELAYED_WORK(&gc_work->dwork, gc_worker);
        gc_work->next_gc_run = GC_INTERVAL_MAX;
        gc_work->exiting = false;
}

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\n");
                        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;
        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.\n");
                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 (!nf_ct_add_synproxy(ct, tmpl)) {
                nf_conntrack_free(ct);
                return ERR_PTR(-ENOMEM);
        }

        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\n");
                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\n",
                                 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);

        /* 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\n");
                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\n", ct);
                        *ctinfo = IP_CT_ESTABLISHED;
                } else if (test_bit(IPS_EXPECTED_BIT, &ct->status)) {
                        pr_debug("related packet for %p\n", ct);
                        *ctinfo = IP_CT_RELATED;
                } else {
                        pr_debug("new packet for %p\n", 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_thresh */
        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\n");
                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);

        ret = l4proto->packet(ct, skb, dataoff, ctinfo, pf, hooknum, timeouts);
        if (ret <= 0) {
                /* Invalid: inverse of the return code tells
                 * the netfilter core what to do */
                pr_debug("nf_conntrack_in: Can't track with proto module\n");
                nf_conntrack_put(skb->nfct);
                skb->nfct = NULL;
                NF_CT_STAT_INC_ATOMIC(net, invalid);
                if (ret == -NF_DROP)
                        NF_CT_STAT_INC_ATOMIC(net, drop);
                ret = -ret;
                goto out;
        }

        if (set_reply && !test_and_set_bit(IPS_SEEN_REPLY_BIT, &ct->status))
                nf_conntrack_event_cache(IPCT_REPLY, ct);
out:
        if (tmpl) {
                /* Special case: we have to repeat this hook, assign the
                 * template again to this packet. We assume that this packet
                 * has no conntrack assigned. This is used by nf_ct_tcp. */
                if (ret == NF_REPEAT)
                        skb->nfct = (struct nf_conntrack *)tmpl;
                else
                        nf_ct_put(tmpl);
        }

        return ret;
}
EXPORT_SYMBOL_GPL(nf_conntrack_in);

bool nf_ct_invert_tuplepr(struct nf_conntrack_tuple *inverse,
                          const struct nf_conntrack_tuple *orig)
{
        bool ret;

        rcu_read_lock();
        ret = nf_ct_invert_tuple(inverse, orig,
                                 __nf_ct_l3proto_find(orig->src.l3num),
                                 __nf_ct_l4proto_find(orig->src.l3num,
                                                      orig->dst.protonum));
        rcu_read_unlock();
        return ret;
}
EXPORT_SYMBOL_GPL(nf_ct_invert_tuplepr);

/* Alter reply tuple (maybe alter helper).  This is for NAT, and is
   implicitly racy: see __nf_conntrack_confirm */
void nf_conntrack_alter_reply(struct nf_conn *ct,
                              const struct nf_conntrack_tuple *newreply)
{
        struct nf_conn_help *help = nfct_help(ct);

        /* Should be unconfirmed, so not in hash table yet */
        NF_CT_ASSERT(!nf_ct_is_confirmed(ct));

        pr_debug("Altering reply tuple of %p to ", ct);
        nf_ct_dump_tuple(newreply);

        ct->tuplehash[IP_CT_DIR_REPLY].tuple = *newreply;
        if (ct->master || (help && !hlist_empty(&help->expectations)))
                return;

        rcu_read_lock();
        __nf_ct_try_assign_helper(ct, NULL, GFP_ATOMIC);
        rcu_read_unlock();
}
EXPORT_SYMBOL_GPL(nf_conntrack_alter_reply);

/* Refresh conntrack for this many jiffies and do accounting if do_acct is 1 */
void __nf_ct_refresh_acct(struct nf_conn *ct,
                          enum ip_conntrack_info ctinfo,
                          const struct sk_buff *skb,
                          unsigned long extra_jiffies,
                          int do_acct)
{
        NF_CT_ASSERT(skb);

        /* Only update if this is not a fixed timeout */
        if (test_bit(IPS_FIXED_TIMEOUT_BIT, &ct->status))
                goto acct;

        /* If not in hash table, timer will not be active yet */
        if (nf_ct_is_confirmed(ct))
                extra_jiffies += nfct_time_stamp;

        ct->timeout = extra_jiffies;
acct:
        if (do_acct)
                nf_ct_acct_update(ct, ctinfo, skb->len);
}
EXPORT_SYMBOL_GPL(__nf_ct_refresh_acct);

bool nf_ct_kill_acct(struct nf_conn *ct,
                     enum ip_conntrack_info ctinfo,
                     const struct sk_buff *skb)
{
        nf_ct_acct_update(ct, ctinfo, skb->len);

        return nf_ct_delete(ct, 0, 0);
}
EXPORT_SYMBOL_GPL(nf_ct_kill_acct);

#if IS_ENABLED(CONFIG_NF_CT_NETLINK)

#include <linux/netfilter/nfnetlink.h>
#include <linux/netfilter/nfnetlink_conntrack.h>
#include <linux/mutex.h>

/* Generic function for tcp/udp/sctp/dccp and alike. This needs to be
 * in ip_conntrack_core, since we don't want the protocols to autoload
 * or depend on ctnetlink */
int nf_ct_port_tuple_to_nlattr(struct sk_buff *skb,
                               const struct nf_conntrack_tuple *tuple)
{
        if (nla_put_be16(skb, CTA_PROTO_SRC_PORT, tuple->src.u.tcp.port) ||
            nla_put_be16(skb, CTA_PROTO_DST_PORT, tuple->dst.u.tcp.port))
                goto nla_put_failure;
        return 0;

nla_put_failure:
        return -1;
}
EXPORT_SYMBOL_GPL(nf_ct_port_tuple_to_nlattr);

const struct nla_policy nf_ct_port_nla_policy[CTA_PROTO_MAX+1] = {
        [CTA_PROTO_SRC_PORT]  = { .type = NLA_U16 },
        [CTA_PROTO_DST_PORT]  = { .type = NLA_U16 },
};
EXPORT_SYMBOL_GPL(nf_ct_port_nla_policy);

int nf_ct_port_nlattr_to_tuple(struct nlattr *tb[],
                               struct nf_conntrack_tuple *t)
{
        if (!tb[CTA_PROTO_SRC_PORT] || !tb[CTA_PROTO_DST_PORT])
                return -EINVAL;

        t->src.u.tcp.port = nla_get_be16(tb[CTA_PROTO_SRC_PORT]);
        t->dst.u.tcp.port = nla_get_be16(tb[CTA_PROTO_DST_PORT]);

        return 0;
}
EXPORT_SYMBOL_GPL(nf_ct_port_nlattr_to_tuple);

int nf_ct_port_nlattr_tuple_size(void)
{
        return nla_policy_len(nf_ct_port_nla_policy, CTA_PROTO_MAX + 1);
}
EXPORT_SYMBOL_GPL(nf_ct_port_nlattr_tuple_size);
#endif

/* Used by ipt_REJECT and ip6t_REJECT. */
static void nf_conntrack_attach(struct sk_buff *nskb, const struct sk_buff *skb)
{
        struct nf_conn *ct;
        enum ip_conntrack_info ctinfo;

        /* This ICMP is in reverse direction to the packet which caused it */
        ct = nf_ct_get(skb, &ctinfo);
        if (CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL)
                ctinfo = IP_CT_RELATED_REPLY;
        else
                ctinfo = IP_CT_RELATED;

        /* Attach to new skbuff, and increment count */
        nskb->nfct = &ct->ct_general;
        nskb->nfctinfo = ctinfo;
        nf_conntrack_get(nskb->nfct);
}

/* Bring out ya dead! */
static struct nf_conn *
get_next_corpse(struct net *net, int (*iter)(struct nf_conn *i, void *data),
                void *data, unsigned int *bucket)
{
        struct nf_conntrack_tuple_hash *h;
        struct nf_conn *ct;
        struct hlist_nulls_node *n;
        int cpu;
        spinlock_t *lockp;

        for (; *bucket < nf_conntrack_htable_size; (*bucket)++) {
                lockp = &nf_conntrack_locks[*bucket % CONNTRACK_LOCKS];
                local_bh_disable();
                nf_conntrack_lock(lockp);
                if (*bucket < nf_conntrack_htable_size) {
                        hlist_nulls_for_each_entry(h, n, &nf_conntrack_hash[*bucket], hnnode) {
                                if (NF_CT_DIRECTION(h) != IP_CT_DIR_ORIGINAL)
                                        continue;
                                ct = nf_ct_tuplehash_to_ctrack(h);
                                if (net_eq(nf_ct_net(ct), net) &&
                                    iter(ct, data))
                                        goto found;
                        }
                }
                spin_unlock(lockp);
                local_bh_enable();
                cond_resched();
        }

        for_each_possible_cpu(cpu) {
                struct ct_pcpu *pcpu = per_cpu_ptr(net->ct.pcpu_lists, cpu);

                spin_lock_bh(&pcpu->lock);
                hlist_nulls_for_each_entry(h, n, &pcpu->unconfirmed, hnnode) {
                        ct = nf_ct_tuplehash_to_ctrack(h);
                        if (iter(ct, data))
                                set_bit(IPS_DYING_BIT, &ct->status);
                }
                spin_unlock_bh(&pcpu->lock);
                cond_resched();
        }
        return NULL;
found:
        atomic_inc(&ct->ct_general.use);
        spin_unlock(lockp);
        local_bh_enable();
        return ct;
}

void nf_ct_iterate_cleanup(struct net *net,
                           int (*iter)(struct nf_conn *i, void *data),
                           void *data, u32 portid, int report)
{
        struct nf_conn *ct;
        unsigned int bucket = 0;

        might_sleep();

        if (atomic_read(&net->ct.count) == 0)
                return;

        while ((ct = get_next_corpse(net, iter, data, &bucket)) != NULL) {
                /* Time to push up daises... */

                nf_ct_delete(ct, portid, report);
                nf_ct_put(ct);
                cond_resched();
        }
}
EXPORT_SYMBOL_GPL(nf_ct_iterate_cleanup);

static int kill_all(struct nf_conn *i, void *data)
{
        return 1;
}

void nf_ct_free_hashtable(void *hash, unsigned int size)
{
        if (is_vmalloc_addr(hash))
                vfree(hash);
        else
                free_pages((unsigned long)hash,
                           get_order(sizeof(struct hlist_head) * size));
}
EXPORT_SYMBOL_GPL(nf_ct_free_hashtable);

static int untrack_refs(void)
{
        int cnt = 0, cpu;

        for_each_possible_cpu(cpu) {
                struct nf_conn *ct = &per_cpu(nf_conntrack_untracked, cpu);

                cnt += atomic_read(&ct->ct_general.use) - 1;
        }
        return cnt;
}

void nf_conntrack_cleanup_start(void)
{
        conntrack_gc_work.exiting = true;
        RCU_INIT_POINTER(ip_ct_attach, NULL);
}

void nf_conntrack_cleanup_end(void)
{
        RCU_INIT_POINTER(nf_ct_destroy, NULL);
        while (untrack_refs() > 0)
                schedule();

        cancel_delayed_work_sync(&conntrack_gc_work.dwork);
        nf_ct_free_hashtable(nf_conntrack_hash, nf_conntrack_htable_size);

        nf_conntrack_proto_fini();
        nf_conntrack_seqadj_fini();
        nf_conntrack_labels_fini();
        nf_conntrack_helper_fini();
        nf_conntrack_timeout_fini();
        nf_conntrack_ecache_fini();
        nf_conntrack_tstamp_fini();
        nf_conntrack_acct_fini();
        nf_conntrack_expect_fini();

        kmem_cache_destroy(nf_conntrack_cachep);
}

/*
 * Mishearing the voices in his head, our hero wonders how he's
 * supposed to kill the mall.
 */
void nf_conntrack_cleanup_net(struct net *net)
{
        LIST_HEAD(single);

        list_add(&net->exit_list, &single);
        nf_conntrack_cleanup_net_list(&single);
}

void nf_conntrack_cleanup_net_list(struct list_head *net_exit_list)
{
        int busy;
        struct net *net;

        /*
         * This makes sure all current packets have passed through
         *  netfilter framework.  Roll on, two-stage module
         *  delete...
         */
        synchronize_net();
i_see_dead_people:
        busy = 0;
        list_for_each_entry(net, net_exit_list, exit_list) {
                nf_ct_iterate_cleanup(net, kill_all, NULL, 0, 0);
                if (atomic_read(&net->ct.count) != 0)
                        busy = 1;
        }
        if (busy) {
                schedule();
                goto i_see_dead_people;
        }

        list_for_each_entry(net, net_exit_list, exit_list) {
                nf_conntrack_proto_pernet_fini(net);
                nf_conntrack_helper_pernet_fini(net);
                nf_conntrack_ecache_pernet_fini(net);
                nf_conntrack_tstamp_pernet_fini(net);
                nf_conntrack_acct_pernet_fini(net);
                nf_conntrack_expect_pernet_fini(net);
                free_percpu(net->ct.stat);
                free_percpu(net->ct.pcpu_lists);
        }
}

void *nf_ct_alloc_hashtable(unsigned int *sizep, int nulls)
{
        struct hlist_nulls_head *hash;
        unsigned int nr_slots, i;
        size_t sz;

        if (*sizep > (UINT_MAX / sizeof(struct hlist_nulls_head)))
                return NULL;

        BUILD_BUG_ON(sizeof(struct hlist_nulls_head) != sizeof(struct hlist_head));
        nr_slots = *sizep = roundup(*sizep, PAGE_SIZE / sizeof(struct hlist_nulls_head));

        if (nr_slots > (UINT_MAX / sizeof(struct hlist_nulls_head)))
                return NULL;

        sz = nr_slots * sizeof(struct hlist_nulls_head);
        hash = (void *)__get_free_pages(GFP_KERNEL | __GFP_NOWARN | __GFP_ZERO,
                                        get_order(sz));
        if (!hash)
                hash = vzalloc(sz);

        if (hash && nulls)
                for (i = 0; i < nr_slots; i++)
                        INIT_HLIST_NULLS_HEAD(&hash[i], i);

        return hash;
}
EXPORT_SYMBOL_GPL(nf_ct_alloc_hashtable);

int nf_conntrack_hash_resize(unsigned int hashsize)
{
        int i, bucket;
        unsigned int old_size;
        struct hlist_nulls_head *hash, *old_hash;
        struct nf_conntrack_tuple_hash *h;
        struct nf_conn *ct;

        if (!hashsize)
                return -EINVAL;

        hash = nf_ct_alloc_hashtable(&hashsize, 1);
        if (!hash)
                return -ENOMEM;

        old_size = nf_conntrack_htable_size;
        if (old_size == hashsize) {
                nf_ct_free_hashtable(hash, hashsize);
                return 0;
        }

        local_bh_disable();
        nf_conntrack_all_lock();
        write_seqcount_begin(&nf_conntrack_generation);

        /* Lookups in the old hash might happen in parallel, which means we
         * might get false negatives during connection lookup. New connections
         * created because of a false negative won't make it into the hash
         * though since that required taking the locks.
         */

        for (i = 0; i < nf_conntrack_htable_size; i++) {
                while (!hlist_nulls_empty(&nf_conntrack_hash[i])) {
                        h = hlist_nulls_entry(nf_conntrack_hash[i].first,
                                              struct nf_conntrack_tuple_hash, hnnode);
                        ct = nf_ct_tuplehash_to_ctrack(h);
                        hlist_nulls_del_rcu(&h->hnnode);
                        bucket = __hash_conntrack(nf_ct_net(ct),
                                                  &h->tuple, hashsize);
                        hlist_nulls_add_head_rcu(&h->hnnode, &hash[bucket]);
                }
        }
        old_size = nf_conntrack_htable_size;
        old_hash = nf_conntrack_hash;

        nf_conntrack_hash = hash;
        nf_conntrack_htable_size = hashsize;

        write_seqcount_end(&nf_conntrack_generation);
        nf_conntrack_all_unlock();
        local_bh_enable();

        synchronize_net();
        nf_ct_free_hashtable(old_hash, old_size);
        return 0;
}

int nf_conntrack_set_hashsize(const char *val, struct kernel_param *kp)
{
        unsigned int hashsize;
        int rc;

        if (current->nsproxy->net_ns != &init_net)
                return -EOPNOTSUPP;

        /* On boot, we can set this without any fancy locking. */
        if (!nf_conntrack_htable_size)
                return param_set_uint(val, kp);

        rc = kstrtouint(val, 0, &hashsize);
        if (rc)
                return rc;

        return nf_conntrack_hash_resize(hashsize);
}
EXPORT_SYMBOL_GPL(nf_conntrack_set_hashsize);

module_param_call(hashsize, nf_conntrack_set_hashsize, param_get_uint,
                  &nf_conntrack_htable_size, 0600);

void nf_ct_untracked_status_or(unsigned long bits)
{
        int cpu;

        for_each_possible_cpu(cpu)
                per_cpu(nf_conntrack_untracked, cpu).status |= bits;
}
EXPORT_SYMBOL_GPL(nf_ct_untracked_status_or);

int nf_conntrack_init_start(void)
{
        int max_factor = 8;
        int ret = -ENOMEM;
        int i, cpu;

        seqcount_init(&nf_conntrack_generation);

        for (i = 0; i < CONNTRACK_LOCKS; i++)
                spin_lock_init(&nf_conntrack_locks[i]);

        if (!nf_conntrack_htable_size) {
                /* Idea from tcp.c: use 1/16384 of memory.
                 * On i386: 32MB machine has 512 buckets.
                 * >= 1GB machines have 16384 buckets.
                 * >= 4GB machines have 65536 buckets.
                 */
                nf_conntrack_htable_size
                        = (((totalram_pages << PAGE_SHIFT) / 16384)
                           / sizeof(struct hlist_head));
                if (totalram_pages > (4 * (1024 * 1024 * 1024 / PAGE_SIZE)))
                        nf_conntrack_htable_size = 65536;
                else if (totalram_pages > (1024 * 1024 * 1024 / PAGE_SIZE))
                        nf_conntrack_htable_size = 16384;
                if (nf_conntrack_htable_size < 32)
                        nf_conntrack_htable_size = 32;

                /* Use a max. factor of four by default to get the same max as
                 * with the old struct list_heads. When a table size is given
                 * we use the old value of 8 to avoid reducing the max.
                 * entries. */
                max_factor = 4;
        }

        nf_conntrack_hash = nf_ct_alloc_hashtable(&nf_conntrack_htable_size, 1);
        if (!nf_conntrack_hash)
                return -ENOMEM;

        nf_conntrack_max = max_factor * nf_conntrack_htable_size;

        nf_conntrack_cachep = kmem_cache_create("nf_conntrack",
                                                sizeof(struct nf_conn), 0,
                                                SLAB_DESTROY_BY_RCU | SLAB_HWCACHE_ALIGN, NULL);
        if (!nf_conntrack_cachep)
                goto err_cachep;

        printk(KERN_INFO "nf_conntrack version %s (%u buckets, %d max)\n",
               NF_CONNTRACK_VERSION, nf_conntrack_htable_size,
               nf_conntrack_max);

        ret = nf_conntrack_expect_init();
        if (ret < 0)
                goto err_expect;

        ret = nf_conntrack_acct_init();
        if (ret < 0)
                goto err_acct;

        ret = nf_conntrack_tstamp_init();
        if (ret < 0)
                goto err_tstamp;

        ret = nf_conntrack_ecache_init();
        if (ret < 0)
                goto err_ecache;

        ret = nf_conntrack_timeout_init();
        if (ret < 0)
                goto err_timeout;

        ret = nf_conntrack_helper_init();
        if (ret < 0)
                goto err_helper;

        ret = nf_conntrack_labels_init();
        if (ret < 0)
                goto err_labels;

        ret = nf_conntrack_seqadj_init();
        if (ret < 0)
                goto err_seqadj;

        ret = nf_conntrack_proto_init();
        if (ret < 0)
                goto err_proto;

        /* Set up fake conntrack: to never be deleted, not in any hashes */
        for_each_possible_cpu(cpu) {
                struct nf_conn *ct = &per_cpu(nf_conntrack_untracked, cpu);
                write_pnet(&ct->ct_net, &init_net);
                atomic_set(&ct->ct_general.use, 1);
        }
        /*  - and look it like as a confirmed connection */
        nf_ct_untracked_status_or(IPS_CONFIRMED | IPS_UNTRACKED);

        conntrack_gc_work_init(&conntrack_gc_work);
        queue_delayed_work(system_long_wq, &conntrack_gc_work.dwork, GC_INTERVAL_MAX);

        return 0;

err_proto:
        nf_conntrack_seqadj_fini();
err_seqadj:
        nf_conntrack_labels_fini();
err_labels:
        nf_conntrack_helper_fini();
err_helper:
        nf_conntrack_timeout_fini();
err_timeout:
        nf_conntrack_ecache_fini();
err_ecache:
        nf_conntrack_tstamp_fini();
err_tstamp:
        nf_conntrack_acct_fini();
err_acct:
        nf_conntrack_expect_fini();
err_expect:
        kmem_cache_destroy(nf_conntrack_cachep);
err_cachep:
        nf_ct_free_hashtable(nf_conntrack_hash, nf_conntrack_htable_size);
        return ret;
}

void nf_conntrack_init_end(void)
{
        /* For use by REJECT target */
        RCU_INIT_POINTER(ip_ct_attach, nf_conntrack_attach);
        RCU_INIT_POINTER(nf_ct_destroy, destroy_conntrack);
}

/*
 * We need to use special "null" values, not used in hash table
 */
#define UNCONFIRMED_NULLS_VAL   ((1<<30)+0)
#define DYING_NULLS_VAL         ((1<<30)+1)
#define TEMPLATE_NULLS_VAL      ((1<<30)+2)

int nf_conntrack_init_net(struct net *net)
{
        int ret = -ENOMEM;
        int cpu;

        atomic_set(&net->ct.count, 0);

        net->ct.pcpu_lists = alloc_percpu(struct ct_pcpu);
        if (!net->ct.pcpu_lists)
                goto err_stat;

        for_each_possible_cpu(cpu) {
                struct ct_pcpu *pcpu = per_cpu_ptr(net->ct.pcpu_lists, cpu);

                spin_lock_init(&pcpu->lock);
                INIT_HLIST_NULLS_HEAD(&pcpu->unconfirmed, UNCONFIRMED_NULLS_VAL);
                INIT_HLIST_NULLS_HEAD(&pcpu->dying, DYING_NULLS_VAL);
        }

        net->ct.stat = alloc_percpu(struct ip_conntrack_stat);
        if (!net->ct.stat)
                goto err_pcpu_lists;

        ret = nf_conntrack_expect_pernet_init(net);
        if (ret < 0)
                goto err_expect;
        ret = nf_conntrack_acct_pernet_init(net);
        if (ret < 0)
                goto err_acct;
        ret = nf_conntrack_tstamp_pernet_init(net);
        if (ret < 0)
                goto err_tstamp;
        ret = nf_conntrack_ecache_pernet_init(net);
        if (ret < 0)
                goto err_ecache;
        ret = nf_conntrack_helper_pernet_init(net);
        if (ret < 0)
                goto err_helper;
        ret = nf_conntrack_proto_pernet_init(net);

        if (ret < 0)
                goto err_proto;
        return 0;

err_proto:
        nf_conntrack_helper_pernet_fini(net);
err_helper:
        nf_conntrack_ecache_pernet_fini(net);
err_ecache:
        nf_conntrack_tstamp_pernet_fini(net);
err_tstamp:
        nf_conntrack_acct_pernet_fini(net);
err_acct:
        nf_conntrack_expect_pernet_fini(net);
err_expect:
        free_percpu(net->ct.stat);
err_pcpu_lists:
        free_percpu(net->ct.pcpu_lists);
err_stat:
        return ret;
}