nf_conntrack_core.c

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

#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_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_nat.h>
#include <net/netfilter/nf_nat_core.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);

int (*nf_nat_seq_adjust_hook)(struct sk_buff *skb,
                  struct nf_conn *ct,
                  enum ip_conntrack_info ctinfo,
                  unsigned int protoff);
EXPORT_SYMBOL_GPL(nf_nat_seq_adjust_hook);

DEFINE_SPINLOCK(nf_conntrack_lock);
EXPORT_SYMBOL_GPL(nf_conntrack_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);

unsigned int nf_conntrack_hash_rnd __read_mostly;
EXPORT_SYMBOL_GPL(nf_conntrack_hash_rnd);

static u32 hash_conntrack_raw(const struct nf_conntrack_tuple *tuple, u16 zone)
{
    unsigned int n;

    /* 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.
     */
    n = (sizeof(tuple->src) + sizeof(tuple->dst.u3)) / sizeof(u32);
    return jhash2((u32 *)tuple, n, zone ^ nf_conntrack_hash_rnd ^
              (((__force __u16)tuple->dst.u.all << 16) |
              tuple->dst.protonum));
}

static u32 __hash_bucket(u32 hash, unsigned int size)
{
    return ((u64)hash * size) >> 32;
}

static u32 hash_bucket(u32 hash, const struct net *net)
{
    return __hash_bucket(hash, net->ct.htable_size);
}

static u_int32_t __hash_conntrack(const struct nf_conntrack_tuple *tuple,
                  u16 zone, unsigned int size)
{
    return __hash_bucket(hash_conntrack_raw(tuple, zone), size);
}

static inline u_int32_t hash_conntrack(const struct net *net, u16 zone,
                       const struct nf_conntrack_tuple *tuple)
{
    return __hash_conntrack(tuple, zone, net->ct.htable_size);
}

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 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, 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 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, 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);
}

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

    /* To make sure we don't get any weird locking issues here:
     * destroy_conntrack() MUST NOT be called with a write lock
     * to nf_conntrack_lock!!! -HW */
    rcu_read_lock();
    l4proto = __nf_ct_l4proto_find(nf_ct_l3num(ct), nf_ct_protonum(ct));
    if (l4proto && l4proto->destroy)
        l4proto->destroy(ct);

    rcu_read_unlock();

    spin_lock_bh(&nf_conntrack_lock);
    /* 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);

    /* We overload first tuple to link into unconfirmed list. */
    if (!nf_ct_is_confirmed(ct)) {
        BUG_ON(hlist_nulls_unhashed(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode));
        hlist_nulls_del_rcu(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode);
    }

    NF_CT_STAT_INC(net, delete);
    spin_unlock_bh(&nf_conntrack_lock);

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

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

void nf_ct_delete_from_lists(struct nf_conn *ct)
{
    struct net *net = nf_ct_net(ct);

    nf_ct_helper_destroy(ct);
    spin_lock_bh(&nf_conntrack_lock);
    /* Inside lock so preempt is disabled on module removal path.
     * Otherwise we can get spurious warnings. */
    NF_CT_STAT_INC(net, delete_list);
    clean_from_lists(ct);
    spin_unlock_bh(&nf_conntrack_lock);
}
EXPORT_SYMBOL_GPL(nf_ct_delete_from_lists);

static void death_by_event(unsigned long ul_conntrack)
{
    struct nf_conn *ct = (void *)ul_conntrack;
    struct net *net = nf_ct_net(ct);
    struct nf_conntrack_ecache *ecache = nf_ct_ecache_find(ct);

    BUG_ON(ecache == NULL);

    if (nf_conntrack_event(IPCT_DESTROY, ct) < 0) {
        /* bad luck, let's retry again */
        ecache->timeout.expires = jiffies +
            (random32() % net->ct.sysctl_events_retry_timeout);
        add_timer(&ecache->timeout);
        return;
    }
    /* we've got the event delivered, now it's dying */
    set_bit(IPS_DYING_BIT, &ct->status);
    spin_lock(&nf_conntrack_lock);
    hlist_nulls_del(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode);
    spin_unlock(&nf_conntrack_lock);
    nf_ct_put(ct);
}

void nf_ct_insert_dying_list(struct nf_conn *ct)
{
    struct net *net = nf_ct_net(ct);
    struct nf_conntrack_ecache *ecache = nf_ct_ecache_find(ct);

    BUG_ON(ecache == NULL);

    /* add this conntrack to the dying list */
    spin_lock_bh(&nf_conntrack_lock);
    hlist_nulls_add_head(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode,
                 &net->ct.dying);
    spin_unlock_bh(&nf_conntrack_lock);
    /* set a new timer to retry event delivery */
    setup_timer(&ecache->timeout, death_by_event, (unsigned long)ct);
    ecache->timeout.expires = jiffies +
        (random32() % net->ct.sysctl_events_retry_timeout);
    add_timer(&ecache->timeout);
}
EXPORT_SYMBOL_GPL(nf_ct_insert_dying_list);

static void death_by_timeout(unsigned long ul_conntrack)
{
    struct nf_conn *ct = (void *)ul_conntrack;
    struct nf_conn_tstamp *tstamp;

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

    if (!test_bit(IPS_DYING_BIT, &ct->status) &&
        unlikely(nf_conntrack_event(IPCT_DESTROY, ct) < 0)) {
        /* destroy event was not delivered */
        nf_ct_delete_from_lists(ct);
        nf_ct_insert_dying_list(ct);
        return;
    }
    set_bit(IPS_DYING_BIT, &ct->status);
    nf_ct_delete_from_lists(ct);
    nf_ct_put(ct);
}

/*
 * Warning :
 * - Caller must take a reference on returned object
 *   and recheck nf_ct_tuple_equal(tuple, &h->tuple)
 * OR
 * - Caller must lock nf_conntrack_lock before calling this function
 */
static struct nf_conntrack_tuple_hash *
____nf_conntrack_find(struct net *net, u16 zone,
              const struct nf_conntrack_tuple *tuple, u32 hash)
{
    struct nf_conntrack_tuple_hash *h;
    struct hlist_nulls_node *n;
    unsigned int bucket = hash_bucket(hash, net);

    /* Disable BHs the entire time since we normally need to disable them
     * at least once for the stats anyway.
     */
    local_bh_disable();
begin:
    hlist_nulls_for_each_entry_rcu(h, n, &net->ct.hash[bucket], hnnode) {
        if (nf_ct_tuple_equal(tuple, &h->tuple) &&
            nf_ct_zone(nf_ct_tuplehash_to_ctrack(h)) == zone) {
            NF_CT_STAT_INC(net, found);
            local_bh_enable();
            return h;
        }
        NF_CT_STAT_INC(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(net, search_restart);
        goto begin;
    }
    local_bh_enable();

    return NULL;
}

struct nf_conntrack_tuple_hash *
__nf_conntrack_find(struct net *net, u16 zone,
            const struct nf_conntrack_tuple *tuple)
{
    return ____nf_conntrack_find(net, zone, tuple,
                     hash_conntrack_raw(tuple, zone));
}
EXPORT_SYMBOL_GPL(__nf_conntrack_find);

/* Find a connection corresponding to a tuple. */
static struct nf_conntrack_tuple_hash *
__nf_conntrack_find_get(struct net *net, u16 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_tuple_equal(tuple, &h->tuple) ||
                     nf_ct_zone(ct) != zone)) {
                nf_ct_put(ct);
                goto begin;
            }
        }
    }
    rcu_read_unlock();

    return h;
}

struct nf_conntrack_tuple_hash *
nf_conntrack_find_get(struct net *net, u16 zone,
              const struct nf_conntrack_tuple *tuple)
{
    return __nf_conntrack_find_get(net, zone, tuple,
                       hash_conntrack_raw(tuple, zone));
}
EXPORT_SYMBOL_GPL(nf_conntrack_find_get);

static void __nf_conntrack_hash_insert(struct nf_conn *ct,
                       unsigned int hash,
                       unsigned int repl_hash)
{
    struct net *net = nf_ct_net(ct);

    hlist_nulls_add_head_rcu(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode,
               &net->ct.hash[hash]);
    hlist_nulls_add_head_rcu(&ct->tuplehash[IP_CT_DIR_REPLY].hnnode,
               &net->ct.hash[repl_hash]);
}

int
nf_conntrack_hash_check_insert(struct nf_conn *ct)
{
    struct net *net = nf_ct_net(ct);
    unsigned int hash, repl_hash;
    struct nf_conntrack_tuple_hash *h;
    struct hlist_nulls_node *n;
    u16 zone;

    zone = nf_ct_zone(ct);
    hash = hash_conntrack(net, zone,
                  &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
    repl_hash = hash_conntrack(net, zone,
                   &ct->tuplehash[IP_CT_DIR_REPLY].tuple);

    spin_lock_bh(&nf_conntrack_lock);

    /* See if there's one in the list already, including reverse */
    hlist_nulls_for_each_entry(h, n, &net->ct.hash[hash], hnnode)
        if (nf_ct_tuple_equal(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple,
                      &h->tuple) &&
            zone == nf_ct_zone(nf_ct_tuplehash_to_ctrack(h)))
            goto out;
    hlist_nulls_for_each_entry(h, n, &net->ct.hash[repl_hash], hnnode)
        if (nf_ct_tuple_equal(&ct->tuplehash[IP_CT_DIR_REPLY].tuple,
                      &h->tuple) &&
            zone == nf_ct_zone(nf_ct_tuplehash_to_ctrack(h)))
            goto out;

    add_timer(&ct->timeout);
    nf_conntrack_get(&ct->ct_general);
    __nf_conntrack_hash_insert(ct, hash, repl_hash);
    NF_CT_STAT_INC(net, insert);
    spin_unlock_bh(&nf_conntrack_lock);

    return 0;

out:
    NF_CT_STAT_INC(net, insert_failed);
    spin_unlock_bh(&nf_conntrack_lock);
    return -EEXIST;
}
EXPORT_SYMBOL_GPL(nf_conntrack_hash_check_insert);

/* Confirm a connection given skb; places it in hash table */
int
__nf_conntrack_confirm(struct sk_buff *skb)
{
    unsigned int hash, repl_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;
    u16 zone;

    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);
    /* reuse the hash saved before */
    hash = *(unsigned long *)&ct->tuplehash[IP_CT_DIR_REPLY].hnnode.pprev;
    hash = hash_bucket(hash, net);
    repl_hash = hash_conntrack(net, zone,
                   &ct->tuplehash[IP_CT_DIR_REPLY].tuple);

    /* 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);

    spin_lock_bh(&nf_conntrack_lock);

    /* We have to check the DYING flag inside the lock 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 */

    if (unlikely(nf_ct_is_dying(ct))) {
        spin_unlock_bh(&nf_conntrack_lock);
        return NF_ACCEPT;
    }

    /* 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, &net->ct.hash[hash], hnnode)
        if (nf_ct_tuple_equal(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple,
                      &h->tuple) &&
            zone == nf_ct_zone(nf_ct_tuplehash_to_ctrack(h)))
            goto out;
    hlist_nulls_for_each_entry(h, n, &net->ct.hash[repl_hash], hnnode)
        if (nf_ct_tuple_equal(&ct->tuplehash[IP_CT_DIR_REPLY].tuple,
                      &h->tuple) &&
            zone == nf_ct_zone(nf_ct_tuplehash_to_ctrack(h)))
            goto out;

    /* Remove from unconfirmed list */
    hlist_nulls_del_rcu(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode);

    /* 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, repl_hash);
    NF_CT_STAT_INC(net, insert);
    spin_unlock_bh(&nf_conntrack_lock);

    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_STAT_INC(net, insert_failed);
    spin_unlock_bh(&nf_conntrack_lock);
    return NF_DROP;
}
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);
    struct nf_conntrack_tuple_hash *h;
    struct hlist_nulls_node *n;
    struct nf_conn *ct;
    u16 zone = nf_ct_zone(ignored_conntrack);
    unsigned int hash = hash_conntrack(net, zone, tuple);

    /* Disable BHs the entire time since we need to disable them at
     * least once for the stats anyway.
     */
    rcu_read_lock_bh();
    hlist_nulls_for_each_entry_rcu(h, n, &net->ct.hash[hash], hnnode) {
        ct = nf_ct_tuplehash_to_ctrack(h);
        if (ct != ignored_conntrack &&
            nf_ct_tuple_equal(tuple, &h->tuple) &&
            nf_ct_zone(ct) == zone) {
            NF_CT_STAT_INC(net, found);
            rcu_read_unlock_bh();
            return 1;
        }
        NF_CT_STAT_INC(net, searched);
    }
    rcu_read_unlock_bh();

    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 *ct = NULL, *tmp;
    struct hlist_nulls_node *n;
    unsigned int i, cnt = 0;
    int dropped = 0;

    rcu_read_lock();
    for (i = 0; i < net->ct.htable_size; i++) {
        hlist_nulls_for_each_entry_rcu(h, n, &net->ct.hash[hash],
                     hnnode) {
            tmp = nf_ct_tuplehash_to_ctrack(h);
            if (!test_bit(IPS_ASSURED_BIT, &tmp->status))
                ct = tmp;
            cnt++;
        }

        if (ct != NULL) {
            if (likely(!nf_ct_is_dying(ct) &&
                   atomic_inc_not_zero(&ct->ct_general.use)))
                break;
            else
                ct = NULL;
        }

        if (cnt >= NF_CT_EVICTION_RANGE)
            break;

        hash = (hash + 1) % net->ct.htable_size;
    }
    rcu_read_unlock();

    if (!ct)
        return dropped;

    if (del_timer(&ct->timeout)) {
        death_by_timeout((unsigned long)ct);
        /* Check if we indeed killed this entry. Reliable event
           delivery may have inserted it into the dying list. */
        if (test_bit(IPS_DYING_BIT, &ct->status)) {
            dropped = 1;
            NF_CT_STAT_INC_ATOMIC(net, early_drop);
        }
    }
    nf_ct_put(ct);
    return dropped;
}

void init_nf_conntrack_hash_rnd(void)
{
    unsigned int rand;

    /*
     * Why not initialize nf_conntrack_rnd in a "init()" function ?
     * Because there isn't enough entropy when system initializing,
     * and we initialize it as late as possible.
     */
    do {
        get_random_bytes(&rand, sizeof(rand));
    } while (!rand);
    cmpxchg(&nf_conntrack_hash_rnd, 0, rand);
}

static struct nf_conn *
__nf_conntrack_alloc(struct net *net, u16 zone,
             const struct nf_conntrack_tuple *orig,
             const struct nf_conntrack_tuple *repl,
             gfp_t gfp, u32 hash)
{
    struct nf_conn *ct;

    if (unlikely(!nf_conntrack_hash_rnd)) {
        init_nf_conntrack_hash_rnd();
        /* recompute the hash as nf_conntrack_hash_rnd is initialized */
        hash = hash_conntrack_raw(orig, zone);
    }

    /* 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_bucket(hash, net))) {
            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(net->ct.nf_conntrack_cachep, gfp);
    if (ct == NULL) {
        atomic_dec(&net->ct.count);
        return ERR_PTR(-ENOMEM);
    }
    /*
     * Let ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode.next
     * and ct->tuplehash[IP_CT_DIR_REPLY].hnnode.next unchanged.
     */
    memset(&ct->tuplehash[IP_CT_DIR_MAX], 0,
           offsetof(struct nf_conn, proto) -
           offsetof(struct nf_conn, tuplehash[IP_CT_DIR_MAX]));
    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;
    /* Don't set timer yet: wait for confirmation */
    setup_timer(&ct->timeout, death_by_timeout, (unsigned long)ct);
    write_pnet(&ct->ct_net, net);
#ifdef CONFIG_NF_CONNTRACK_ZONES
    if (zone) {
        struct nf_conntrack_zone *nf_ct_zone;

        nf_ct_zone = nf_ct_ext_add(ct, NF_CT_EXT_ZONE, GFP_ATOMIC);
        if (!nf_ct_zone)
            goto out_free;
        nf_ct_zone->id = zone;
    }
#endif
    /*
     * changes to lookup keys must be done before setting refcnt to 1
     */
    smp_wmb();
    atomic_set(&ct->ct_general.use, 1);
    return ct;

#ifdef CONFIG_NF_CONNTRACK_ZONES
out_free:
    atomic_dec(&net->ct.count);
    kmem_cache_free(net->ct.nf_conntrack_cachep, ct);
    return ERR_PTR(-ENOMEM);
#endif
}

struct nf_conn *nf_conntrack_alloc(struct net *net, u16 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);

    nf_ct_ext_destroy(ct);
    atomic_dec(&net->ct.count);
    nf_ct_ext_free(ct);
    kmem_cache_free(net->ct.nf_conntrack_cachep, ct);
}
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;
    u16 zone = tmpl ? nf_ct_zone(tmpl) : NF_CT_DEFAULT_ZONE;
    struct nf_conn_timeout *timeout_ext;
    unsigned int *timeouts;

    if (!nf_ct_invert_tuple(&repl_tuple, tuple, l3proto, l4proto)) {
        pr_debug("Can't invert tuple.\n");
        return NULL;
    }

    ct = __nf_conntrack_alloc(net, zone, tuple, &repl_tuple, GFP_ATOMIC,
                  hash);
    if (IS_ERR(ct))
        return (struct nf_conntrack_tuple_hash *)ct;

    timeout_ext = tmpl ? nf_ct_timeout_find(tmpl) : NULL;
    if (timeout_ext)
        timeouts = NF_CT_TIMEOUT_EXT_DATA(timeout_ext);
    else
        timeouts = l4proto->get_timeouts(net);

    if (!l4proto->new(ct, skb, dataoff, timeouts)) {
        nf_conntrack_free(ct);
        pr_debug("init conntrack: can't track with proto module\n");
        return NULL;
    }

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

    nf_ct_acct_ext_add(ct, GFP_ATOMIC);
    nf_ct_tstamp_ext_add(ct, GFP_ATOMIC);

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

    spin_lock_bh(&nf_conntrack_lock);
    exp = nf_ct_find_expectation(net, zone, tuple);
    if (exp) {
        pr_debug("conntrack: expectation arrives ct=%p exp=%p\n",
             ct, exp);
        /* Welcome, Mr. Bond.  We've been expecting you... */
        __set_bit(IPS_EXPECTED_BIT, &ct->status);
        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_conntrack_get(&ct->master->ct_general);
        NF_CT_STAT_INC(net, expect_new);
    } else {
        __nf_ct_try_assign_helper(ct, tmpl, GFP_ATOMIC);
        NF_CT_STAT_INC(net, new);
    }

    /* Overload tuple linked list to put us in unconfirmed list. */
    hlist_nulls_add_head_rcu(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode,
               &net->ct.unconfirmed);

    spin_unlock_bh(&nf_conntrack_lock);

    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)
{
    struct nf_conntrack_tuple tuple;
    struct nf_conntrack_tuple_hash *h;
    struct nf_conn *ct;
    u16 zone = tmpl ? nf_ct_zone(tmpl) : NF_CT_DEFAULT_ZONE;
    u32 hash;

    if (!nf_ct_get_tuple(skb, skb_network_offset(skb),
                 dataoff, l3num, protonum, &tuple, l3proto,
                 l4proto)) {
        pr_debug("resolve_normal_ct: Can't get tuple\n");
        return NULL;
    }

    /* look for tuple match */
    hash = hash_conntrack_raw(&tuple, zone);
    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("nf_conntrack_in: normal packet for %p\n", ct);
            *ctinfo = IP_CT_ESTABLISHED;
        } else if (test_bit(IPS_EXPECTED_BIT, &ct->status)) {
            pr_debug("nf_conntrack_in: related packet for %p\n",
                 ct);
            *ctinfo = IP_CT_RELATED;
        } else {
            pr_debug("nf_conntrack_in: 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_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\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(ct->timeout.data == (unsigned long)ct);
    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)) {
        ct->timeout.expires = extra_jiffies;
    } else {
        unsigned long newtime = jiffies + extra_jiffies;

        /* Only update the timeout if the new timeout is at least
           HZ jiffies from the old timeout. Need del_timer for race
           avoidance (may already be dying). */
        if (newtime - ct->timeout.expires >= HZ)
            mod_timer_pending(&ct->timeout, newtime);
    }

acct:
    if (do_acct) {
        struct nf_conn_counter *acct;

        acct = nf_conn_acct_find(ct);
        if (acct) {
            atomic64_inc(&acct[CTINFO2DIR(ctinfo)].packets);
            atomic64_add(skb->len, &acct[CTINFO2DIR(ctinfo)].bytes);
        }
    }
}
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,
               int do_acct)
{
    if (do_acct) {
        struct nf_conn_counter *acct;

        acct = nf_conn_acct_find(ct);
        if (acct) {
            atomic64_inc(&acct[CTINFO2DIR(ctinfo)].packets);
            atomic64_add(skb->len - skb_network_offset(skb),
                     &acct[CTINFO2DIR(ctinfo)].bytes);
        }
    }

    if (del_timer(&ct->timeout)) {
        ct->timeout.function((unsigned long)ct);
        return true;
    }
    return false;
}
EXPORT_SYMBOL_GPL(__nf_ct_kill_acct);

#ifdef CONFIG_NF_CONNTRACK_ZONES
static struct nf_ct_ext_type nf_ct_zone_extend __read_mostly = {
    .len    = sizeof(struct nf_conntrack_zone),
    .align  = __alignof__(struct nf_conntrack_zone),
    .id = NF_CT_EXT_ZONE,
};
#endif

#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, 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;

    spin_lock_bh(&nf_conntrack_lock);
    for (; *bucket < net->ct.htable_size; (*bucket)++) {
        hlist_nulls_for_each_entry(h, n, &net->ct.hash[*bucket], hnnode) {
            if (NF_CT_DIRECTION(h) != IP_CT_DIR_ORIGINAL)
                continue;
            ct = nf_ct_tuplehash_to_ctrack(h);
            if (iter(ct, data))
                goto found;
        }
    }
    hlist_nulls_for_each_entry(h, n, &net->ct.unconfirmed, hnnode) {
        ct = nf_ct_tuplehash_to_ctrack(h);
        if (iter(ct, data))
            set_bit(IPS_DYING_BIT, &ct->status);
    }
    spin_unlock_bh(&nf_conntrack_lock);
    return NULL;
found:
    atomic_inc(&ct->ct_general.use);
    spin_unlock_bh(&nf_conntrack_lock);
    return ct;
}

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

    while ((ct = get_next_corpse(net, iter, data, &bucket)) != NULL) {
        /* Time to push up daises... */
        if (del_timer(&ct->timeout))
            death_by_timeout((unsigned long)ct);
        /* ... else the timer will get him soon. */

        nf_ct_put(ct);
    }
}
EXPORT_SYMBOL_GPL(nf_ct_iterate_cleanup);

struct __nf_ct_flush_report {
    u32 pid;
    int report;
};

static int kill_report(struct nf_conn *i, void *data)
{
    struct __nf_ct_flush_report *fr = (struct __nf_ct_flush_report *)data;
    struct nf_conn_tstamp *tstamp;

    tstamp = nf_conn_tstamp_find(i);
    if (tstamp && tstamp->stop == 0)
        tstamp->stop = ktime_to_ns(ktime_get_real());

    /* If we fail to deliver the event, death_by_timeout() will retry */
    if (nf_conntrack_event_report(IPCT_DESTROY, i,
                      fr->pid, fr->report) < 0)
        return 1;

    /* Avoid the delivery of the destroy event in death_by_timeout(). */
    set_bit(IPS_DYING_BIT, &i->status);
    return 1;
}

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);

void nf_conntrack_flush_report(struct net *net, u32 pid, int report)
{
    struct __nf_ct_flush_report fr = {
        .pid    = pid,
        .report = report,
    };
    nf_ct_iterate_cleanup(net, kill_report, &fr);
}
EXPORT_SYMBOL_GPL(nf_conntrack_flush_report);

static void nf_ct_release_dying_list(struct net *net)
{
    struct nf_conntrack_tuple_hash *h;
    struct nf_conn *ct;
    struct hlist_nulls_node *n;

    spin_lock_bh(&nf_conntrack_lock);
    hlist_nulls_for_each_entry(h, n, &net->ct.dying, hnnode) {
        ct = nf_ct_tuplehash_to_ctrack(h);
        /* never fails to remove them, no listeners at this point */
        nf_ct_kill(ct);
    }
    spin_unlock_bh(&nf_conntrack_lock);
}

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;
}

static void nf_conntrack_cleanup_init_net(void)
{
    while (untrack_refs() > 0)
        schedule();

#ifdef CONFIG_NF_CONNTRACK_ZONES
    nf_ct_extend_unregister(&nf_ct_zone_extend);
#endif
}

static void nf_conntrack_cleanup_net(struct net *net)
{
 i_see_dead_people:
    nf_ct_iterate_cleanup(net, kill_all, NULL);
    nf_ct_release_dying_list(net);
    if (atomic_read(&net->ct.count) != 0) {
        schedule();
        goto i_see_dead_people;
    }

    nf_ct_free_hashtable(net->ct.hash, net->ct.htable_size);
    nf_conntrack_helper_fini(net);
    nf_conntrack_timeout_fini(net);
    nf_conntrack_ecache_fini(net);
    nf_conntrack_tstamp_fini(net);
    nf_conntrack_acct_fini(net);
    nf_conntrack_expect_fini(net);
    kmem_cache_destroy(net->ct.nf_conntrack_cachep);
    kfree(net->ct.slabname);
    free_percpu(net->ct.stat);
}

/* Mishearing the voices in his head, our hero wonders how he's
   supposed to kill the mall. */
void nf_conntrack_cleanup(struct net *net)
{
    if (net_eq(net, &init_net))
        RCU_INIT_POINTER(ip_ct_attach, NULL);

    /* This makes sure all current packets have passed through
       netfilter framework.  Roll on, two-stage module
       delete... */
    synchronize_net();
    nf_conntrack_proto_fini(net);
    nf_conntrack_cleanup_net(net);

    if (net_eq(net, &init_net)) {
        RCU_INIT_POINTER(nf_ct_destroy, NULL);
        nf_conntrack_cleanup_init_net();
    }
}

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

    BUILD_BUG_ON(sizeof(struct hlist_nulls_head) != sizeof(struct hlist_head));
    nr_slots = *sizep = roundup(*sizep, PAGE_SIZE / sizeof(struct hlist_nulls_head));
    sz = nr_slots * sizeof(struct hlist_nulls_head);
    hash = (void *)__get_free_pages(GFP_KERNEL | __GFP_NOWARN | __GFP_ZERO,
                    get_order(sz));
    if (!hash) {
        printk(KERN_WARNING "nf_conntrack: falling back to vmalloc.\n");
        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_set_hashsize(const char *val, struct kernel_param *kp)
{
    int i, bucket;
    unsigned int hashsize, old_size;
    struct hlist_nulls_head *hash, *old_hash;
    struct nf_conntrack_tuple_hash *h;
    struct nf_conn *ct;

    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);

    hashsize = simple_strtoul(val, NULL, 0);
    if (!hashsize)
        return -EINVAL;

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

    /* 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 lock.
     */
    spin_lock_bh(&nf_conntrack_lock);
    for (i = 0; i < init_net.ct.htable_size; i++) {
        while (!hlist_nulls_empty(&init_net.ct.hash[i])) {
            h = hlist_nulls_entry(init_net.ct.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(&h->tuple, nf_ct_zone(ct),
                          hashsize);
            hlist_nulls_add_head_rcu(&h->hnnode, &hash[bucket]);
        }
    }
    old_size = init_net.ct.htable_size;
    old_hash = init_net.ct.hash;

    init_net.ct.htable_size = nf_conntrack_htable_size = hashsize;
    init_net.ct.hash = hash;
    spin_unlock_bh(&nf_conntrack_lock);

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

static int nf_conntrack_init_init_net(void)
{
    int max_factor = 8;
    int ret, cpu;

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

    printk(KERN_INFO "nf_conntrack version %s (%u buckets, %d max)\n",
           NF_CONNTRACK_VERSION, nf_conntrack_htable_size,
           nf_conntrack_max);
#ifdef CONFIG_NF_CONNTRACK_ZONES
    ret = nf_ct_extend_register(&nf_ct_zone_extend);
    if (ret < 0)
        goto err_extend;
#endif
    /* 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);
    return 0;

#ifdef CONFIG_NF_CONNTRACK_ZONES
err_extend:
#endif
    return ret;
}

/*
 * 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)

static int nf_conntrack_init_net(struct net *net)
{
    int ret;

    atomic_set(&net->ct.count, 0);
    INIT_HLIST_NULLS_HEAD(&net->ct.unconfirmed, UNCONFIRMED_NULLS_VAL);
    INIT_HLIST_NULLS_HEAD(&net->ct.dying, DYING_NULLS_VAL);
    net->ct.stat = alloc_percpu(struct ip_conntrack_stat);
    if (!net->ct.stat) {
        ret = -ENOMEM;
        goto err_stat;
    }

    net->ct.slabname = kasprintf(GFP_KERNEL, "nf_conntrack_%p", net);
    if (!net->ct.slabname) {
        ret = -ENOMEM;
        goto err_slabname;
    }

    net->ct.nf_conntrack_cachep = kmem_cache_create(net->ct.slabname,
                            sizeof(struct nf_conn), 0,
                            SLAB_DESTROY_BY_RCU, NULL);
    if (!net->ct.nf_conntrack_cachep) {
        printk(KERN_ERR "Unable to create nf_conn slab cache\n");
        ret = -ENOMEM;
        goto err_cache;
    }

    net->ct.htable_size = nf_conntrack_htable_size;
    net->ct.hash = nf_ct_alloc_hashtable(&net->ct.htable_size, 1);
    if (!net->ct.hash) {
        ret = -ENOMEM;
        printk(KERN_ERR "Unable to create nf_conntrack_hash\n");
        goto err_hash;
    }
    ret = nf_conntrack_expect_init(net);
    if (ret < 0)
        goto err_expect;
    ret = nf_conntrack_acct_init(net);
    if (ret < 0)
        goto err_acct;
    ret = nf_conntrack_tstamp_init(net);
    if (ret < 0)
        goto err_tstamp;
    ret = nf_conntrack_ecache_init(net);
    if (ret < 0)
        goto err_ecache;
    ret = nf_conntrack_timeout_init(net);
    if (ret < 0)
        goto err_timeout;
    ret = nf_conntrack_helper_init(net);
    if (ret < 0)
        goto err_helper;
    return 0;
err_helper:
    nf_conntrack_timeout_fini(net);
err_timeout:
    nf_conntrack_ecache_fini(net);
err_ecache:
    nf_conntrack_tstamp_fini(net);
err_tstamp:
    nf_conntrack_acct_fini(net);
err_acct:
    nf_conntrack_expect_fini(net);
err_expect:
    nf_ct_free_hashtable(net->ct.hash, net->ct.htable_size);
err_hash:
    kmem_cache_destroy(net->ct.nf_conntrack_cachep);
err_cache:
    kfree(net->ct.slabname);
err_slabname:
    free_percpu(net->ct.stat);
err_stat:
    return ret;
}

s16 (*nf_ct_nat_offset)(const struct nf_conn *ct,
            enum ip_conntrack_dir dir,
            u32 seq);
EXPORT_SYMBOL_GPL(nf_ct_nat_offset);

int nf_conntrack_init(struct net *net)
{
    int ret;

    if (net_eq(net, &init_net)) {
        ret = nf_conntrack_init_init_net();
        if (ret < 0)
            goto out_init_net;
    }
    ret = nf_conntrack_proto_init(net);
    if (ret < 0)
        goto out_proto;
    ret = nf_conntrack_init_net(net);
    if (ret < 0)
        goto out_net;

    if (net_eq(net, &init_net)) {
        /* For use by REJECT target */
        RCU_INIT_POINTER(ip_ct_attach, nf_conntrack_attach);
        RCU_INIT_POINTER(nf_ct_destroy, destroy_conntrack);

        /* Howto get NAT offsets */
        RCU_INIT_POINTER(nf_ct_nat_offset, NULL);
    }
    return 0;

out_net:
    nf_conntrack_proto_fini(net);
out_proto:
    if (net_eq(net, &init_net))
        nf_conntrack_cleanup_init_net();
out_init_net:
    return ret;
}