[GitHub/mt8127/android_kernel_alcatel_ttab.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.
 *
 * 23 Apr 2001: Harald Welte <laforge@gnumonks.org>
 *      - new API and handling of conntrack/nat helpers
 *      - now capable of multiple expectations for one master
 * 16 Jul 2002: Harald Welte <laforge@gnumonks.org>
 *      - add usage/reference counts to ip_conntrack_expect
 *      - export ip_conntrack[_expect]_{find_get,put} functions
 * 16 Dec 2003: Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp>
 *      - generalize L3 protocol denendent part.
 * 23 Mar 2004: Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp>
 *      - add support various size of conntrack structures.
 * 26 Jan 2006: Harald Welte <laforge@netfilter.org>
 *      - restructure nf_conn (introduce nf_conn_help)
 *      - redesign 'features' how they were originally intended
 * 26 Feb 2006: Pablo Neira Ayuso <pablo@eurodev.net>
 *      - add support for L3 protocol module load on demand.
 *
 * Derived from net/ipv4/netfilter/ip_conntrack_core.c
 */

#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 <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>

#define NF_CONNTRACK_VERSION    "0.5.0"

#if 0
#define DEBUGP printk
#else
#define DEBUGP(format, args...)
#endif

DEFINE_RWLOCK(nf_conntrack_lock);

/* nf_conntrack_standalone needs this */
atomic_t nf_conntrack_count = ATOMIC_INIT(0);
EXPORT_SYMBOL_GPL(nf_conntrack_count);

void (*nf_conntrack_destroyed)(struct nf_conn *conntrack) = NULL;
unsigned int nf_conntrack_htable_size __read_mostly;
int nf_conntrack_max __read_mostly;
EXPORT_SYMBOL_GPL(nf_conntrack_max);
struct list_head *nf_conntrack_hash __read_mostly;
struct nf_conn nf_conntrack_untracked __read_mostly;
unsigned int nf_ct_log_invalid __read_mostly;
LIST_HEAD(unconfirmed);
static int nf_conntrack_vmalloc __read_mostly;

static unsigned int nf_conntrack_next_id;

DEFINE_PER_CPU(struct ip_conntrack_stat, nf_conntrack_stat);
EXPORT_PER_CPU_SYMBOL(nf_conntrack_stat);

/*
 * This scheme offers various size of "struct nf_conn" dependent on
 * features(helper, nat, ...)
 */

#define NF_CT_FEATURES_NAMELEN  256
static struct {
        /* name of slab cache. printed in /proc/slabinfo */
        char *name;

        /* size of slab cache */
        size_t size;

        /* slab cache pointer */
        kmem_cache_t *cachep;

        /* allocated slab cache + modules which uses this slab cache */
        int use;

} nf_ct_cache[NF_CT_F_NUM];

/* protect members of nf_ct_cache except of "use" */
DEFINE_RWLOCK(nf_ct_cache_lock);

/* This avoids calling kmem_cache_create() with same name simultaneously */
static DEFINE_MUTEX(nf_ct_cache_mutex);

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 a, b;
        a = jhash((void *)tuple->src.u3.all, sizeof(tuple->src.u3.all),
                  ((tuple->src.l3num) << 16) | tuple->dst.protonum);
        b = jhash((void *)tuple->dst.u3.all, sizeof(tuple->dst.u3.all),
                        (tuple->src.u.all << 16) | tuple->dst.u.all);

        return jhash_2words(a, b, rnd) % size;
}

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);
}

int nf_conntrack_register_cache(u_int32_t features, const char *name,
                                size_t size)
{
        int ret = 0;
        char *cache_name;
        kmem_cache_t *cachep;

        DEBUGP("nf_conntrack_register_cache: features=0x%x, name=%s, size=%d\n",
               features, name, size);

        if (features < NF_CT_F_BASIC || features >= NF_CT_F_NUM) {
                DEBUGP("nf_conntrack_register_cache: invalid features.: 0x%x\n",
                        features);
                return -EINVAL;
        }

        mutex_lock(&nf_ct_cache_mutex);

        write_lock_bh(&nf_ct_cache_lock);
        /* e.g: multiple helpers are loaded */
        if (nf_ct_cache[features].use > 0) {
                DEBUGP("nf_conntrack_register_cache: already resisterd.\n");
                if ((!strncmp(nf_ct_cache[features].name, name,
                              NF_CT_FEATURES_NAMELEN))
                    && nf_ct_cache[features].size == size) {
                        DEBUGP("nf_conntrack_register_cache: reusing.\n");
                        nf_ct_cache[features].use++;
                        ret = 0;
                } else
                        ret = -EBUSY;

                write_unlock_bh(&nf_ct_cache_lock);
                mutex_unlock(&nf_ct_cache_mutex);
                return ret;
        }
        write_unlock_bh(&nf_ct_cache_lock);

        /*
         * The memory space for name of slab cache must be alive until
         * cache is destroyed.
         */
        cache_name = kmalloc(sizeof(char)*NF_CT_FEATURES_NAMELEN, GFP_ATOMIC);
        if (cache_name == NULL) {
                DEBUGP("nf_conntrack_register_cache: can't alloc cache_name\n");
                ret = -ENOMEM;
                goto out_up_mutex;
        }

        if (strlcpy(cache_name, name, NF_CT_FEATURES_NAMELEN)
                                                >= NF_CT_FEATURES_NAMELEN) {
                printk("nf_conntrack_register_cache: name too long\n");
                ret = -EINVAL;
                goto out_free_name;
        }

        cachep = kmem_cache_create(cache_name, size, 0, 0,
                                   NULL, NULL);
        if (!cachep) {
                printk("nf_conntrack_register_cache: Can't create slab cache "
                       "for the features = 0x%x\n", features);
                ret = -ENOMEM;
                goto out_free_name;
        }

        write_lock_bh(&nf_ct_cache_lock);
        nf_ct_cache[features].use = 1;
        nf_ct_cache[features].size = size;
        nf_ct_cache[features].cachep = cachep;
        nf_ct_cache[features].name = cache_name;
        write_unlock_bh(&nf_ct_cache_lock);

        goto out_up_mutex;

out_free_name:
        kfree(cache_name);
out_up_mutex:
        mutex_unlock(&nf_ct_cache_mutex);
        return ret;
}

/* FIXME: In the current, only nf_conntrack_cleanup() can call this function. */
void nf_conntrack_unregister_cache(u_int32_t features)
{
        kmem_cache_t *cachep;
        char *name;

        /*
         * This assures that kmem_cache_create() isn't called before destroying
         * slab cache.
         */
        DEBUGP("nf_conntrack_unregister_cache: 0x%04x\n", features);
        mutex_lock(&nf_ct_cache_mutex);

        write_lock_bh(&nf_ct_cache_lock);
        if (--nf_ct_cache[features].use > 0) {
                write_unlock_bh(&nf_ct_cache_lock);
                mutex_unlock(&nf_ct_cache_mutex);
                return;
        }
        cachep = nf_ct_cache[features].cachep;
        name = nf_ct_cache[features].name;
        nf_ct_cache[features].cachep = NULL;
        nf_ct_cache[features].name = NULL;
        nf_ct_cache[features].size = 0;
        write_unlock_bh(&nf_ct_cache_lock);

        synchronize_net();

        kmem_cache_destroy(cachep);
        kfree(name);

        mutex_unlock(&nf_ct_cache_mutex);
}

int
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)
{
        NF_CT_TUPLE_U_BLANK(tuple);

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

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

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

int
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)
{
        NF_CT_TUPLE_U_BLANK(inverse);

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

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

        inverse->dst.protonum = orig->dst.protonum;
        return l4proto->invert_tuple(inverse, orig);
}

static void
clean_from_lists(struct nf_conn *ct)
{
        DEBUGP("clean_from_lists(%p)\n", ct);
        list_del(&ct->tuplehash[IP_CT_DIR_ORIGINAL].list);
        list_del(&ct->tuplehash[IP_CT_DIR_REPLY].list);

        /* 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 nf_conntrack_l3proto *l3proto;
        struct nf_conntrack_l4proto *l4proto;

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

        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 */
        l3proto = __nf_ct_l3proto_find(ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.l3num);
        if (l3proto && l3proto->destroy)
                l3proto->destroy(ct);

        l4proto = __nf_ct_l4proto_find(ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.l3num, ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.protonum);
        if (l4proto && l4proto->destroy)
                l4proto->destroy(ct);

        if (nf_conntrack_destroyed)
                nf_conntrack_destroyed(ct);

        write_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(list_empty(&ct->tuplehash[IP_CT_DIR_ORIGINAL].list));
                list_del(&ct->tuplehash[IP_CT_DIR_ORIGINAL].list);
        }

        NF_CT_STAT_INC(delete);
        write_unlock_bh(&nf_conntrack_lock);

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

        DEBUGP("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;

        write_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(delete_list);
        clean_from_lists(ct);
        write_unlock_bh(&nf_conntrack_lock);
        nf_ct_put(ct);
}

struct nf_conntrack_tuple_hash *
__nf_conntrack_find(const struct nf_conntrack_tuple *tuple,
                    const struct nf_conn *ignored_conntrack)
{
        struct nf_conntrack_tuple_hash *h;
        unsigned int hash = hash_conntrack(tuple);

        list_for_each_entry(h, &nf_conntrack_hash[hash], list) {
                if (nf_ct_tuplehash_to_ctrack(h) != ignored_conntrack &&
                    nf_ct_tuple_equal(tuple, &h->tuple)) {
                        NF_CT_STAT_INC(found);
                        return h;
                }
                NF_CT_STAT_INC(searched);
        }

        return NULL;
}

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

        read_lock_bh(&nf_conntrack_lock);
        h = __nf_conntrack_find(tuple, ignored_conntrack);
        if (h)
                atomic_inc(&nf_ct_tuplehash_to_ctrack(h)->ct_general.use);
        read_unlock_bh(&nf_conntrack_lock);

        return h;
}

static void __nf_conntrack_hash_insert(struct nf_conn *ct,
                                       unsigned int hash,
                                       unsigned int repl_hash) 
{
        ct->id = ++nf_conntrack_next_id;
        list_add(&ct->tuplehash[IP_CT_DIR_ORIGINAL].list,
                 &nf_conntrack_hash[hash]);
        list_add(&ct->tuplehash[IP_CT_DIR_REPLY].list,
                 &nf_conntrack_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);

        write_lock_bh(&nf_conntrack_lock);
        __nf_conntrack_hash_insert(ct, hash, repl_hash);
        write_unlock_bh(&nf_conntrack_lock);
}

/* Confirm a connection given skb; places it in hash table */
int
__nf_conntrack_confirm(struct sk_buff **pskb)
{
        unsigned int hash, repl_hash;
        struct nf_conntrack_tuple_hash *h;
        struct nf_conn *ct;
        struct nf_conn_help *help;
        enum ip_conntrack_info ctinfo;

        ct = nf_ct_get(*pskb, &ctinfo);

        /* 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));
        DEBUGP("Confirming conntrack %p\n", ct);

        write_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. */
        list_for_each_entry(h, &nf_conntrack_hash[hash], list)
                if (nf_ct_tuple_equal(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple,
                                      &h->tuple))
                        goto out;
        list_for_each_entry(h, &nf_conntrack_hash[repl_hash], list)
                if (nf_ct_tuple_equal(&ct->tuplehash[IP_CT_DIR_REPLY].tuple,
                                      &h->tuple))
                        goto out;

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

        __nf_conntrack_hash_insert(ct, hash, repl_hash);
        /* 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);
        NF_CT_STAT_INC(insert);
        write_unlock_bh(&nf_conntrack_lock);
        help = nfct_help(ct);
        if (help && help->helper)
                nf_conntrack_event_cache(IPCT_HELPER, *pskb);
#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, *pskb);
#endif
        nf_conntrack_event_cache(master_ct(ct) ?
                                 IPCT_RELATED : IPCT_NEW, *pskb);
        return NF_ACCEPT;

out:
        NF_CT_STAT_INC(insert_failed);
        write_unlock_bh(&nf_conntrack_lock);
        return NF_DROP;
}

/* 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 nf_conntrack_tuple_hash *h;

        read_lock_bh(&nf_conntrack_lock);
        h = __nf_conntrack_find(tuple, ignored_conntrack);
        read_unlock_bh(&nf_conntrack_lock);

        return h != NULL;
}

/* There's a small race here where we may free a just-assured
   connection.  Too bad: we're in trouble anyway. */
static int early_drop(struct list_head *chain)
{
        /* Traverse backwards: gives us oldest, which is roughly LRU */
        struct nf_conntrack_tuple_hash *h;
        struct nf_conn *ct = NULL, *tmp;
        int dropped = 0;

        read_lock_bh(&nf_conntrack_lock);
        list_for_each_entry_reverse(h, chain, list) {
                tmp = nf_ct_tuplehash_to_ctrack(h);
                if (!test_bit(IPS_ASSURED_BIT, &tmp->status)) {
                        ct = tmp;
                        atomic_inc(&ct->ct_general.use);
                        break;
                }
        }
        read_unlock_bh(&nf_conntrack_lock);

        if (!ct)
                return dropped;

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

static struct nf_conn *
__nf_conntrack_alloc(const struct nf_conntrack_tuple *orig,
                     const struct nf_conntrack_tuple *repl,
                     const struct nf_conntrack_l3proto *l3proto)
{
        struct nf_conn *conntrack = NULL;
        u_int32_t features = 0;
        struct nf_conntrack_helper *helper;

        if (unlikely(!nf_conntrack_hash_rnd_initted)) {
                get_random_bytes(&nf_conntrack_hash_rnd, 4);
                nf_conntrack_hash_rnd_initted = 1;
        }

        /* We don't want any race condition at early drop stage */
        atomic_inc(&nf_conntrack_count);

        if (nf_conntrack_max
            && atomic_read(&nf_conntrack_count) > nf_conntrack_max) {
                unsigned int hash = hash_conntrack(orig);
                /* Try dropping from this hash chain. */
                if (!early_drop(&nf_conntrack_hash[hash])) {
                        atomic_dec(&nf_conntrack_count);
                        if (net_ratelimit())
                                printk(KERN_WARNING
                                       "nf_conntrack: table full, dropping"
                                       " packet.\n");
                        return ERR_PTR(-ENOMEM);
                }
        }

        /*  find features needed by this conntrack. */
        features = l3proto->get_features(orig);

        /* FIXME: protect helper list per RCU */
        read_lock_bh(&nf_conntrack_lock);
        helper = __nf_ct_helper_find(repl);
        if (helper)
                features |= NF_CT_F_HELP;
        read_unlock_bh(&nf_conntrack_lock);

        DEBUGP("nf_conntrack_alloc: features=0x%x\n", features);

        read_lock_bh(&nf_ct_cache_lock);

        if (unlikely(!nf_ct_cache[features].use)) {
                DEBUGP("nf_conntrack_alloc: not supported features = 0x%x\n",
                        features);
                goto out;
        }

        conntrack = kmem_cache_alloc(nf_ct_cache[features].cachep, GFP_ATOMIC);
        if (conntrack == NULL) {
                DEBUGP("nf_conntrack_alloc: Can't alloc conntrack from cache\n");
                goto out;
        }

        memset(conntrack, 0, nf_ct_cache[features].size);
        conntrack->features = features;
        atomic_set(&conntrack->ct_general.use, 1);
        conntrack->ct_general.destroy = destroy_conntrack;
        conntrack->tuplehash[IP_CT_DIR_ORIGINAL].tuple = *orig;
        conntrack->tuplehash[IP_CT_DIR_REPLY].tuple = *repl;
        /* Don't set timer yet: wait for confirmation */
        init_timer(&conntrack->timeout);
        conntrack->timeout.data = (unsigned long)conntrack;
        conntrack->timeout.function = death_by_timeout;
        read_unlock_bh(&nf_ct_cache_lock);

        return conntrack;
out:
        read_unlock_bh(&nf_ct_cache_lock);
        atomic_dec(&nf_conntrack_count);
        return conntrack;
}

struct nf_conn *nf_conntrack_alloc(const struct nf_conntrack_tuple *orig,
                                   const struct nf_conntrack_tuple *repl)
{
        struct nf_conntrack_l3proto *l3proto;

        l3proto = __nf_ct_l3proto_find(orig->src.l3num);
        return __nf_conntrack_alloc(orig, repl, l3proto);
}

void nf_conntrack_free(struct nf_conn *conntrack)
{
        u_int32_t features = conntrack->features;
        NF_CT_ASSERT(features >= NF_CT_F_BASIC && features < NF_CT_F_NUM);
        DEBUGP("nf_conntrack_free: features = 0x%x, conntrack=%p\n", features,
               conntrack);
        kmem_cache_free(nf_ct_cache[features].cachep, conntrack);
        atomic_dec(&nf_conntrack_count);
}

/* 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(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 *conntrack;
        struct nf_conntrack_tuple repl_tuple;
        struct nf_conntrack_expect *exp;

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

        conntrack = __nf_conntrack_alloc(tuple, &repl_tuple, l3proto);
        if (conntrack == NULL || IS_ERR(conntrack)) {
                DEBUGP("Can't allocate conntrack.\n");
                return (struct nf_conntrack_tuple_hash *)conntrack;
        }

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

        write_lock_bh(&nf_conntrack_lock);
        exp = find_expectation(tuple);

        if (exp) {
                DEBUGP("conntrack: expectation arrives ct=%p exp=%p\n",
                        conntrack, exp);
                /* Welcome, Mr. Bond.  We've been expecting you... */
                __set_bit(IPS_EXPECTED_BIT, &conntrack->status);
                conntrack->master = exp->master;
#ifdef CONFIG_NF_CONNTRACK_MARK
                conntrack->mark = exp->master->mark;
#endif
#ifdef CONFIG_NF_CONNTRACK_SECMARK
                conntrack->secmark = exp->master->secmark;
#endif
                nf_conntrack_get(&conntrack->master->ct_general);
                NF_CT_STAT_INC(expect_new);
        } else {
                struct nf_conn_help *help = nfct_help(conntrack);

                if (help)
                        help->helper = __nf_ct_helper_find(&repl_tuple);
                NF_CT_STAT_INC(new);
        }

        /* Overload tuple linked list to put us in unconfirmed list. */
        list_add(&conntrack->tuplehash[IP_CT_DIR_ORIGINAL].list, &unconfirmed);

        write_unlock_bh(&nf_conntrack_lock);

        if (exp) {
                if (exp->expectfn)
                        exp->expectfn(conntrack, exp);
                nf_conntrack_expect_put(exp);
        }

        return &conntrack->tuplehash[IP_CT_DIR_ORIGINAL];
}

/* On success, returns conntrack ptr, sets skb->nfct and ctinfo */
static inline struct nf_conn *
resolve_normal_ct(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, (unsigned int)(skb->nh.raw - skb->data),
                             dataoff, l3num, protonum, &tuple, l3proto,
                             l4proto)) {
                DEBUGP("resolve_normal_ct: Can't get tuple\n");
                return NULL;
        }

        /* look for tuple match */
        h = nf_conntrack_find_get(&tuple, NULL);
        if (!h) {
                h = init_conntrack(&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)) {
                        DEBUGP("nf_conntrack_in: normal packet for %p\n", ct);
                        *ctinfo = IP_CT_ESTABLISHED;
                } else if (test_bit(IPS_EXPECTED_BIT, &ct->status)) {
                        DEBUGP("nf_conntrack_in: related packet for %p\n", ct);
                        *ctinfo = IP_CT_RELATED;
                } else {
                        DEBUGP("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(int pf, unsigned int hooknum, struct sk_buff **pskb)
{
        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 ((*pskb)->nfct) {
                NF_CT_STAT_INC(ignore);
                return NF_ACCEPT;
        }

        l3proto = __nf_ct_l3proto_find((u_int16_t)pf);
        if ((ret = l3proto->prepare(pskb, hooknum, &dataoff, &protonum)) <= 0) {
                DEBUGP("not prepared to track yet or error occured\n");
                return -ret;
        }

        l4proto = __nf_ct_l4proto_find((u_int16_t)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(*pskb, dataoff, &ctinfo, pf, hooknum)) <= 0) {
                NF_CT_STAT_INC(error);
                NF_CT_STAT_INC(invalid);
                return -ret;
        }

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

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

        NF_CT_ASSERT((*pskb)->nfct);

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

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

        return ret;
}

int nf_ct_invert_tuplepr(struct nf_conntrack_tuple *inverse,
                         const struct nf_conntrack_tuple *orig)
{
        return nf_ct_invert_tuple(inverse, orig,
                                  __nf_ct_l3proto_find(orig->src.l3num),
                                  __nf_ct_l4proto_find(orig->src.l3num,
                                                     orig->dst.protonum));
}

/* 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);

        write_lock_bh(&nf_conntrack_lock);

        /* Only update if this is not a fixed timeout */
        if (test_bit(IPS_FIXED_TIMEOUT_BIT, &ct->status)) {
                write_unlock_bh(&nf_conntrack_lock);
                return;
        }

        /* 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;
                }
        }

#ifdef CONFIG_NF_CT_ACCT
        if (do_acct) {
                ct->counters[CTINFO2DIR(ctinfo)].packets++;
                ct->counters[CTINFO2DIR(ctinfo)].bytes +=
                        skb->len - (unsigned int)(skb->nh.raw - skb->data);

                if ((ct->counters[CTINFO2DIR(ctinfo)].packets & 0x80000000)
                    || (ct->counters[CTINFO2DIR(ctinfo)].bytes & 0x80000000))
                        event |= IPCT_COUNTER_FILLING;
        }
#endif

        write_unlock_bh(&nf_conntrack_lock);

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

#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_nfattr(struct sk_buff *skb,
                               const struct nf_conntrack_tuple *tuple)
{
        NFA_PUT(skb, CTA_PROTO_SRC_PORT, sizeof(u_int16_t),
                &tuple->src.u.tcp.port);
        NFA_PUT(skb, CTA_PROTO_DST_PORT, sizeof(u_int16_t),
                &tuple->dst.u.tcp.port);
        return 0;

nfattr_failure:
        return -1;
}

static const size_t cta_min_proto[CTA_PROTO_MAX] = {
        [CTA_PROTO_SRC_PORT-1]  = sizeof(u_int16_t),
        [CTA_PROTO_DST_PORT-1]  = sizeof(u_int16_t)
};

int nf_ct_port_nfattr_to_tuple(struct nfattr *tb[],
                               struct nf_conntrack_tuple *t)
{
        if (!tb[CTA_PROTO_SRC_PORT-1] || !tb[CTA_PROTO_DST_PORT-1])
                return -EINVAL;

        if (nfattr_bad_size(tb, CTA_PROTO_MAX, cta_min_proto))
                return -EINVAL;

        t->src.u.tcp.port = *(__be16 *)NFA_DATA(tb[CTA_PROTO_SRC_PORT-1]);
        t->dst.u.tcp.port = *(__be16 *)NFA_DATA(tb[CTA_PROTO_DST_PORT-1]);

        return 0;
}
#endif

/* Used by ipt_REJECT and ip6t_REJECT. */
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);
}

static inline int
do_iter(const struct nf_conntrack_tuple_hash *i,
        int (*iter)(struct nf_conn *i, void *data),
        void *data)
{
        return iter(nf_ct_tuplehash_to_ctrack(i), data);
}

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

        write_lock_bh(&nf_conntrack_lock);
        for (; *bucket < nf_conntrack_htable_size; (*bucket)++) {
                list_for_each_entry(h, &nf_conntrack_hash[*bucket], list) {
                        ct = nf_ct_tuplehash_to_ctrack(h);
                        if (iter(ct, data))
                                goto found;
                }
        }
        list_for_each_entry(h, &unconfirmed, list) {
                ct = nf_ct_tuplehash_to_ctrack(h);
                if (iter(ct, data))
                        goto found;
        }
        write_unlock_bh(&nf_conntrack_lock);
        return NULL;
found:
        atomic_inc(&ct->ct_general.use);
        write_unlock_bh(&nf_conntrack_lock);
        return ct;
}

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

        while ((ct = get_next_corpse(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);
        }
}

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

static void free_conntrack_hash(struct list_head *hash, int vmalloced, int size)
{
        if (vmalloced)
                vfree(hash);
        else
                free_pages((unsigned long)hash, 
                           get_order(sizeof(struct list_head) * size));
}

void nf_conntrack_flush()
{
        nf_ct_iterate_cleanup(kill_all, NULL);
}

/* Mishearing the voices in his head, our hero wonders how he's
   supposed to kill the mall. */
void nf_conntrack_cleanup(void)
{
        int i;

        ip_ct_attach = NULL;

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

        nf_ct_event_cache_flush();
 i_see_dead_people:
        nf_conntrack_flush();
        if (atomic_read(&nf_conntrack_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();

        for (i = 0; i < NF_CT_F_NUM; i++) {
                if (nf_ct_cache[i].use == 0)
                        continue;

                NF_CT_ASSERT(nf_ct_cache[i].use == 1);
                nf_ct_cache[i].use = 1;
                nf_conntrack_unregister_cache(i);
        }
        kmem_cache_destroy(nf_conntrack_expect_cachep);
        free_conntrack_hash(nf_conntrack_hash, nf_conntrack_vmalloc,
                            nf_conntrack_htable_size);

        nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_generic);

        /* free l3proto protocol tables */
        for (i = 0; i < PF_MAX; i++)
                if (nf_ct_protos[i]) {
                        kfree(nf_ct_protos[i]);
                        nf_ct_protos[i] = NULL;
                }
}

static struct list_head *alloc_hashtable(int size, int *vmalloced)
{
        struct list_head *hash;
        unsigned int i;

        *vmalloced = 0; 
        hash = (void*)__get_free_pages(GFP_KERNEL, 
                                       get_order(sizeof(struct list_head)
                                                 * size));
        if (!hash) { 
                *vmalloced = 1;
                printk(KERN_WARNING "nf_conntrack: falling back to vmalloc.\n");
                hash = vmalloc(sizeof(struct list_head) * size);
        }

        if (hash)
                for (i = 0; i < size; i++) 
                        INIT_LIST_HEAD(&hash[i]);

        return hash;
}

int set_hashsize(const char *val, struct kernel_param *kp)
{
        int i, bucket, hashsize, vmalloced;
        int old_vmalloced, old_size;
        int rnd;
        struct list_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_strtol(val, NULL, 0);
        if (!hashsize)
                return -EINVAL;

        hash = alloc_hashtable(hashsize, &vmalloced);
        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, 4);

        write_lock_bh(&nf_conntrack_lock);
        for (i = 0; i < nf_conntrack_htable_size; i++) {
                while (!list_empty(&nf_conntrack_hash[i])) {
                        h = list_entry(nf_conntrack_hash[i].next,
                                       struct nf_conntrack_tuple_hash, list);
                        list_del(&h->list);
                        bucket = __hash_conntrack(&h->tuple, hashsize, rnd);
                        list_add_tail(&h->list, &hash[bucket]);
                }
        }
        old_size = nf_conntrack_htable_size;
        old_vmalloced = nf_conntrack_vmalloc;
        old_hash = nf_conntrack_hash;

        nf_conntrack_htable_size = hashsize;
        nf_conntrack_vmalloc = vmalloced;
        nf_conntrack_hash = hash;
        nf_conntrack_hash_rnd = rnd;
        write_unlock_bh(&nf_conntrack_lock);

        free_conntrack_hash(old_hash, old_vmalloced, old_size);
        return 0;
}

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

int __init nf_conntrack_init(void)
{
        unsigned int i;
        int ret;

        /* Idea from tcp.c: use 1/16384 of memory.  On i386: 32MB
         * machine has 256 buckets.  >= 1GB machines have 8192 buckets. */
        if (!nf_conntrack_htable_size) {
                nf_conntrack_htable_size
                        = (((num_physpages << PAGE_SHIFT) / 16384)
                           / sizeof(struct list_head));
                if (num_physpages > (1024 * 1024 * 1024 / PAGE_SIZE))
                        nf_conntrack_htable_size = 8192;
                if (nf_conntrack_htable_size < 16)
                        nf_conntrack_htable_size = 16;
        }
        nf_conntrack_max = 8 * 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_hash = alloc_hashtable(nf_conntrack_htable_size,
                                            &nf_conntrack_vmalloc);
        if (!nf_conntrack_hash) {
                printk(KERN_ERR "Unable to create nf_conntrack_hash\n");
                goto err_out;
        }

        ret = nf_conntrack_register_cache(NF_CT_F_BASIC, "nf_conntrack:basic",
                                          sizeof(struct nf_conn));
        if (ret < 0) {
                printk(KERN_ERR "Unable to create nf_conn slab cache\n");
                goto err_free_hash;
        }

        nf_conntrack_expect_cachep = kmem_cache_create("nf_conntrack_expect",
                                        sizeof(struct nf_conntrack_expect),
                                        0, 0, NULL, NULL);
        if (!nf_conntrack_expect_cachep) {
                printk(KERN_ERR "Unable to create nf_expect slab cache\n");
                goto err_free_conntrack_slab;
        }

        ret = nf_conntrack_l4proto_register(&nf_conntrack_l4proto_generic);
        if (ret < 0)
                goto out_free_expect_slab;

        /* Don't NEED lock here, but good form anyway. */
        write_lock_bh(&nf_conntrack_lock);
        for (i = 0; i < AF_MAX; i++)
                nf_ct_l3protos[i] = &nf_conntrack_l3proto_generic;
        write_unlock_bh(&nf_conntrack_lock);

        /* For use by REJECT target */
        ip_ct_attach = __nf_conntrack_attach;

        /* Set up fake conntrack:
            - to never be deleted, not in any hashes */
        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 ret;

out_free_expect_slab:
        kmem_cache_destroy(nf_conntrack_expect_cachep);
err_free_conntrack_slab:
        nf_conntrack_unregister_cache(NF_CT_F_BASIC);
err_free_hash:
        free_conntrack_hash(nf_conntrack_hash, nf_conntrack_vmalloc,
                            nf_conntrack_htable_size);
err_out:
        return -ENOMEM;
}