netfilter: nf_conntrack: fix conntrack lookup race

[linux-2.6/mini2440.git] / net / netfilter / nf_conntrack_core.c

/* 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>
 *
 * 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/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/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_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,
                                      struct nlattr *attr) __read_mostly;
EXPORT_SYMBOL_GPL(nfnetlink_parse_nat_setup_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);

struct nf_conn nf_conntrack_untracked __read_mostly;
EXPORT_SYMBOL_GPL(nf_conntrack_untracked);

static struct kmem_cache *nf_conntrack_cachep __read_mostly;

static int nf_conntrack_hash_rnd_initted;
static unsigned int nf_conntrack_hash_rnd;

static u_int32_t __hash_conntrack(const struct nf_conntrack_tuple *tuple,
                                  unsigned int size, unsigned int rnd)
{
        unsigned int n;
        u_int32_t h;

        /* 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);
        h = jhash2((u32 *)tuple, n,
                   rnd ^ (((__force __u16)tuple->dst.u.all << 16) |
                          tuple->dst.protonum));

        return ((u64)h * size) >> 32;
}

static inline u_int32_t hash_conntrack(const struct nf_conntrack_tuple *tuple)
{
        return __hash_conntrack(tuple, nf_conntrack_htable_size,
                                nf_conntrack_hash_rnd);
}

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));

        if (!test_bit(IPS_DYING_BIT, &ct->status))
                nf_conntrack_event(IPCT_DESTROY, ct);
        set_bit(IPS_DYING_BIT, &ct->status);

        /* 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);
}

static void death_by_timeout(unsigned long ul_conntrack)
{
        struct nf_conn *ct = (void *)ul_conntrack;
        struct net *net = nf_ct_net(ct);
        struct nf_conn_help *help = nfct_help(ct);
        struct nf_conntrack_helper *helper;

        if (help) {
                rcu_read_lock();
                helper = rcu_dereference(help->helper);
                if (helper && helper->destroy)
                        helper->destroy(ct);
                rcu_read_unlock();
        }

        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);
        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
 */
struct nf_conntrack_tuple_hash *
__nf_conntrack_find(struct net *net, const struct nf_conntrack_tuple *tuple)
{
        struct nf_conntrack_tuple_hash *h;
        struct hlist_nulls_node *n;
        unsigned int hash = hash_conntrack(tuple);

        /* 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[hash], hnnode) {
                if (nf_ct_tuple_equal(tuple, &h->tuple)) {
                        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) != hash)
                goto begin;
        local_bh_enable();

        return NULL;
}
EXPORT_SYMBOL_GPL(__nf_conntrack_find);

/* Find a connection corresponding to a tuple. */
struct nf_conntrack_tuple_hash *
nf_conntrack_find_get(struct net *net, const struct nf_conntrack_tuple *tuple)
{
        struct nf_conntrack_tuple_hash *h;
        struct nf_conn *ct;

        rcu_read_lock();
begin:
        h = __nf_conntrack_find(net, tuple);
        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_put(ct);
                                goto begin;
                        }
                }
        }
        rcu_read_unlock();

        return h;
}
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]);
}

void nf_conntrack_hash_insert(struct nf_conn *ct)
{
        unsigned int hash, repl_hash;

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

        __nf_conntrack_hash_insert(ct, hash, repl_hash);
}
EXPORT_SYMBOL_GPL(nf_conntrack_hash_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 hlist_nulls_node *n;
        enum ip_conntrack_info ctinfo;
        struct net *net;

        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;

        hash = hash_conntrack(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
        repl_hash = hash_conntrack(&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 noone 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);

        /* 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))
                        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))
                        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);
        set_bit(IPS_CONFIRMED_BIT, &ct->status);

        /* 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);
#ifdef CONFIG_NF_NAT_NEEDED
        if (test_bit(IPS_SRC_NAT_DONE_BIT, &ct->status) ||
            test_bit(IPS_DST_NAT_DONE_BIT, &ct->status))
                nf_conntrack_event_cache(IPCT_NATINFO, ct);
#endif
        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;
        unsigned int hash = hash_conntrack(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) {
                if (nf_ct_tuplehash_to_ctrack(h) != ignored_conntrack &&
                    nf_ct_tuple_equal(tuple, &h->tuple)) {
                        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 < nf_conntrack_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 && unlikely(nf_ct_is_dying(ct) ||
                                   !atomic_inc_not_zero(&ct->ct_general.use)))
                        ct = NULL;
                if (ct || cnt >= NF_CT_EVICTION_RANGE)
                        break;
                hash = (hash + 1) % nf_conntrack_htable_size;
        }
        rcu_read_unlock();

        if (!ct)
                return dropped;

        if (del_timer(&ct->timeout)) {
                death_by_timeout((unsigned long)ct);
                dropped = 1;
                NF_CT_STAT_INC_ATOMIC(net, early_drop);
        }
        nf_ct_put(ct);
        return dropped;
}

struct nf_conn *nf_conntrack_alloc(struct net *net,
                                   const struct nf_conntrack_tuple *orig,
                                   const struct nf_conntrack_tuple *repl,
                                   gfp_t gfp)
{
        struct nf_conn *ct;

        if (unlikely(!nf_conntrack_hash_rnd_initted)) {
                get_random_bytes(&nf_conntrack_hash_rnd,
                                sizeof(nf_conntrack_hash_rnd));
                nf_conntrack_hash_rnd_initted = 1;
        }

        /* 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)) {
                unsigned int hash = hash_conntrack(orig);
                if (!early_drop(net, hash)) {
                        atomic_dec(&net->ct.count);
                        if (net_ratelimit())
                                printk(KERN_WARNING
                                       "nf_conntrack: table full, dropping"
                                       " packet.\n");
                        return ERR_PTR(-ENOMEM);
                }
        }

        ct = kmem_cache_zalloc(nf_conntrack_cachep, gfp);
        if (ct == NULL) {
                pr_debug("nf_conntrack_alloc: Can't alloc conntrack.\n");
                atomic_dec(&net->ct.count);
                return ERR_PTR(-ENOMEM);
        }

        atomic_set(&ct->ct_general.use, 1);
        ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple = *orig;
        ct->tuplehash[IP_CT_DIR_REPLY].tuple = *repl;
        /* Don't set timer yet: wait for confirmation */
        setup_timer(&ct->timeout, death_by_timeout, (unsigned long)ct);
#ifdef CONFIG_NET_NS
        ct->ct_net = net;
#endif

        return ct;
}
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(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,
               const struct nf_conntrack_tuple *tuple,
               struct nf_conntrack_l3proto *l3proto,
               struct nf_conntrack_l4proto *l4proto,
               struct sk_buff *skb,
               unsigned int dataoff)
{
        struct nf_conn *ct;
        struct nf_conn_help *help;
        struct nf_conntrack_tuple repl_tuple;
        struct nf_conntrack_expect *exp;

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

        ct = nf_conntrack_alloc(net, tuple, &repl_tuple, GFP_ATOMIC);
        if (IS_ERR(ct)) {
                pr_debug("Can't allocate conntrack.\n");
                return (struct nf_conntrack_tuple_hash *)ct;
        }

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

        nf_ct_acct_ext_add(ct, GFP_ATOMIC);

        spin_lock_bh(&nf_conntrack_lock);
        exp = nf_ct_find_expectation(net, 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, 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, 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 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;

        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 */
        h = nf_conntrack_find_get(net, &tuple);
        if (!h) {
                h = init_conntrack(net, &tuple, l3proto, l4proto, skb, dataoff);
                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 + IP_CT_IS_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;
        enum ip_conntrack_info ctinfo;
        struct nf_conntrack_l3proto *l3proto;
        struct nf_conntrack_l4proto *l4proto;
        unsigned int dataoff;
        u_int8_t protonum;
        int set_reply = 0;
        int ret;

        /* Previously seen (loopback or untracked)?  Ignore. */
        if (skb->nfct) {
                NF_CT_STAT_INC_ATOMIC(net, ignore);
                return NF_ACCEPT;
        }

        /* 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 occured\n");
                NF_CT_STAT_INC_ATOMIC(net, error);
                NF_CT_STAT_INC_ATOMIC(net, invalid);
                return -ret;
        }

        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, skb, dataoff, &ctinfo, pf, hooknum);
                if (ret <= 0) {
                        NF_CT_STAT_INC_ATOMIC(net, error);
                        NF_CT_STAT_INC_ATOMIC(net, invalid);
                        return -ret;
                }
        }

        ct = resolve_normal_ct(net, skb, dataoff, pf, protonum,
                               l3proto, l4proto, &set_reply, &ctinfo);
        if (!ct) {
                /* Not valid part of a connection */
                NF_CT_STAT_INC_ATOMIC(net, invalid);
                return NF_ACCEPT;
        }

        if (IS_ERR(ct)) {
                /* Too stressed to deal. */
                NF_CT_STAT_INC_ATOMIC(net, drop);
                return NF_DROP;
        }

        NF_CT_ASSERT(skb->nfct);

        ret = l4proto->packet(ct, skb, dataoff, ctinfo, pf, hooknum);
        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);
                return -ret;
        }

        if (set_reply && !test_and_set_bit(IPS_SEEN_REPLY_BIT, &ct->status))
                nf_conntrack_event_cache(IPCT_STATUS, ct);

        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, 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)
{
        int event = 0;

        NF_CT_ASSERT(ct->timeout.data == (unsigned long)ct);
        NF_CT_ASSERT(skb);

        spin_lock_bh(&nf_conntrack_lock);

        /* 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;
                event = IPCT_REFRESH;
        } 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
                    && del_timer(&ct->timeout)) {
                        ct->timeout.expires = newtime;
                        add_timer(&ct->timeout);
                        event = IPCT_REFRESH;
                }
        }

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

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

        spin_unlock_bh(&nf_conntrack_lock);

        /* must be unlocked when calling event cache */
        if (event)
                nf_conntrack_event_cache(event, ct);
}
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;

                spin_lock_bh(&nf_conntrack_lock);
                acct = nf_conn_acct_find(ct);
                if (acct) {
                        acct[CTINFO2DIR(ctinfo)].packets++;
                        acct[CTINFO2DIR(ctinfo)].bytes +=
                                skb->len - skb_network_offset(skb);
                }
                spin_unlock_bh(&nf_conntrack_lock);
        }

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

#if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)

#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)
{
        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);
        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 + IP_CT_IS_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 < nf_conntrack_htable_size; (*bucket)++) {
                hlist_nulls_for_each_entry(h, n, &net->ct.hash[*bucket], hnnode) {
                        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_all(struct nf_conn *i, void *data)
{
        struct __nf_ct_flush_report *fr = (struct __nf_ct_flush_report *)data;

        /* get_next_corpse sets the dying bit for us */
        nf_conntrack_event_report(IPCT_DESTROY,
                                  i,
                                  fr->pid,
                                  fr->report);
        return 1;
}

void nf_ct_free_hashtable(void *hash, int vmalloced, unsigned int size)
{
        if (vmalloced)
                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(struct net *net, u32 pid, int report)
{
        struct __nf_ct_flush_report fr = {
                .pid    = pid,
                .report = report,
        };
        nf_ct_iterate_cleanup(net, kill_all, &fr);
}
EXPORT_SYMBOL_GPL(nf_conntrack_flush);

static void nf_conntrack_cleanup_init_net(void)
{
        nf_conntrack_helper_fini();
        nf_conntrack_proto_fini();
        kmem_cache_destroy(nf_conntrack_cachep);
}

static void nf_conntrack_cleanup_net(struct net *net)
{
        nf_ct_event_cache_flush(net);
        nf_conntrack_ecache_fini(net);
 i_see_dead_people:
        nf_conntrack_flush(net, 0, 0);
        if (atomic_read(&net->ct.count) != 0) {
                schedule();
                goto i_see_dead_people;
        }
        /* wait until all references to nf_conntrack_untracked are dropped */
        while (atomic_read(&nf_conntrack_untracked.ct_general.use) > 1)
                schedule();

        nf_ct_free_hashtable(net->ct.hash, net->ct.hash_vmalloc,
                             nf_conntrack_htable_size);
        nf_conntrack_acct_fini(net);
        nf_conntrack_expect_fini(net);
        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_assign_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_cleanup_net(net);

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

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

        *vmalloced = 0;

        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) {
                *vmalloced = 1;
                printk(KERN_WARNING "nf_conntrack: falling back to vmalloc.\n");
                hash = __vmalloc(sz, GFP_KERNEL | __GFP_ZERO, PAGE_KERNEL);
        }

        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, vmalloced, old_vmalloced;
        unsigned int hashsize, old_size;
        int rnd;
        struct hlist_nulls_head *hash, *old_hash;
        struct nf_conntrack_tuple_hash *h;

        /* 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, &vmalloced, 1);
        if (!hash)
                return -ENOMEM;

        /* We have to rehahs for the new table anyway, so we also can
         * use a newrandom seed */
        get_random_bytes(&rnd, sizeof(rnd));

        /* 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 < nf_conntrack_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);
                        hlist_nulls_del_rcu(&h->hnnode);
                        bucket = __hash_conntrack(&h->tuple, hashsize, rnd);
                        hlist_nulls_add_head_rcu(&h->hnnode, &hash[bucket]);
                }
        }
        old_size = nf_conntrack_htable_size;
        old_vmalloced = init_net.ct.hash_vmalloc;
        old_hash = init_net.ct.hash;

        nf_conntrack_htable_size = hashsize;
        init_net.ct.hash_vmalloc = vmalloced;
        init_net.ct.hash = hash;
        nf_conntrack_hash_rnd = rnd;
        spin_unlock_bh(&nf_conntrack_lock);

        nf_ct_free_hashtable(old_hash, old_vmalloced, 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);

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

        /* 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
                        = (((num_physpages << PAGE_SHIFT) / 16384)
                           / sizeof(struct hlist_head));
                if (num_physpages > (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("nf_conntrack version %s (%u buckets, %d max)\n",
               NF_CONNTRACK_VERSION, nf_conntrack_htable_size,
               nf_conntrack_max);

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

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

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

        return 0;

err_helper:
        nf_conntrack_proto_fini();
err_proto:
        kmem_cache_destroy(nf_conntrack_cachep);
err_cache:
        return ret;
}

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

        atomic_set(&net->ct.count, 0);
        INIT_HLIST_NULLS_HEAD(&net->ct.unconfirmed, 0);
        net->ct.stat = alloc_percpu(struct ip_conntrack_stat);
        if (!net->ct.stat) {
                ret = -ENOMEM;
                goto err_stat;
        }
        ret = nf_conntrack_ecache_init(net);
        if (ret < 0)
                goto err_ecache;
        net->ct.hash = nf_ct_alloc_hashtable(&nf_conntrack_htable_size,
                                             &net->ct.hash_vmalloc, 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;

        /* Set up fake conntrack:
            - to never be deleted, not in any hashes */
#ifdef CONFIG_NET_NS
        nf_conntrack_untracked.ct_net = &init_net;
#endif
        atomic_set(&nf_conntrack_untracked.ct_general.use, 1);
        /*  - and look it like as a confirmed connection */
        set_bit(IPS_CONFIRMED_BIT, &nf_conntrack_untracked.status);

        return 0;

err_acct:
        nf_conntrack_expect_fini(net);
err_expect:
        nf_ct_free_hashtable(net->ct.hash, net->ct.hash_vmalloc,
                             nf_conntrack_htable_size);
err_hash:
        nf_conntrack_ecache_fini(net);
err_ecache:
        free_percpu(net->ct.stat);
err_stat:
        return ret;
}

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_init_net(net);
        if (ret < 0)
                goto out_net;

        if (net_eq(net, &init_net)) {
                /* For use by REJECT target */
                rcu_assign_pointer(ip_ct_attach, nf_conntrack_attach);
                rcu_assign_pointer(nf_ct_destroy, destroy_conntrack);
        }
        return 0;

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