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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 <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>

#define NF_CONNTRACK_VERSION  "0.5.0"

DEFINE_RWLOCK(nf_conntrack_lock);
EXPORT_SYMBOL_GPL(nf_conntrack_lock);

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

unsigned int nf_conntrack_htable_size __read_mostly;
EXPORT_SYMBOL_GPL(nf_conntrack_htable_size);

int nf_conntrack_max __read_mostly;
EXPORT_SYMBOL_GPL(nf_conntrack_max);

struct hlist_head *nf_conntrack_hash __read_mostly;
EXPORT_SYMBOL_GPL(nf_conntrack_hash);

struct nf_conn nf_conntrack_untracked __read_mostly;
EXPORT_SYMBOL_GPL(nf_conntrack_untracked);

unsigned int nf_ct_log_invalid __read_mostly;
HLIST_HEAD(unconfirmed);
static int nf_conntrack_vmalloc __read_mostly;
static struct kmem_cache *nf_conntrack_cachep __read_mostly;

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

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 = jhash2(tuple->src.u3.all, ARRAY_SIZE(tuple->src.u3.all),
               (tuple->src.l3num << 16) | tuple->dst.protonum);
      b = jhash2(tuple->dst.u3.all, ARRAY_SIZE(tuple->dst.u3.all),
               ((__force __u16)tuple->src.u.all << 16) |
                (__force __u16)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_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);
}
EXPORT_SYMBOL_GPL(nf_ct_get_tuple);

int 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 0;
      }

      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);

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);
}
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_del(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnode);
      hlist_del(&ct->tuplehash[IP_CT_DIR_REPLY].hnode);

      /* 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_l4proto *l4proto;

      pr_debug("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 */
      rcu_read_lock();
      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);

      nf_ct_ext_destroy(ct);

      rcu_read_unlock();

      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(hlist_unhashed(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnode));
            hlist_del(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnode);
      }

      NF_CT_STAT_INC(delete);
      write_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 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();
      }

      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;
      struct hlist_node *n;
      unsigned int hash = hash_conntrack(tuple);

      hlist_for_each_entry(h, n, &nf_conntrack_hash[hash], hnode) {
            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;
}
EXPORT_SYMBOL_GPL(__nf_conntrack_find);

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

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

      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)
{
      hlist_add_head(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnode,
                   &nf_conntrack_hash[hash]);
      hlist_add_head(&ct->tuplehash[IP_CT_DIR_REPLY].hnode,
                   &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);
}
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_node *n;
      enum ip_conntrack_info ctinfo;

      ct = nf_ct_get(skb, &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));
      pr_debug("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. */
      hlist_for_each_entry(h, n, &nf_conntrack_hash[hash], hnode)
            if (nf_ct_tuple_equal(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple,
                              &h->tuple))
                  goto out;
      hlist_for_each_entry(h, n, &nf_conntrack_hash[repl_hash], hnode)
            if (nf_ct_tuple_equal(&ct->tuplehash[IP_CT_DIR_REPLY].tuple,
                              &h->tuple))
                  goto out;

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

      __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, skb);
#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, skb);
#endif
      nf_conntrack_event_cache(master_ct(ct) ?
                         IPCT_RELATED : IPCT_NEW, skb);
      return NF_ACCEPT;

out:
      NF_CT_STAT_INC(insert_failed);
      write_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 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;
}
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 int early_drop(unsigned int hash)
{
      /* Use oldest entry, which is roughly LRU */
      struct nf_conntrack_tuple_hash *h;
      struct nf_conn *ct = NULL, *tmp;
      struct hlist_node *n;
      unsigned int i, cnt = 0;
      int dropped = 0;

      read_lock_bh(&nf_conntrack_lock);
      for (i = 0; i < nf_conntrack_htable_size; i++) {
            hlist_for_each_entry(h, n, &nf_conntrack_hash[hash], hnode) {
                  tmp = nf_ct_tuplehash_to_ctrack(h);
                  if (!test_bit(IPS_ASSURED_BIT, &tmp->status))
                        ct = tmp;
                  cnt++;
            }
            if (ct || cnt >= NF_CT_EVICTION_RANGE)
                  break;
            hash = (hash + 1) % nf_conntrack_htable_size;
      }
      if (ct)
            atomic_inc(&ct->ct_general.use);
      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_ATOMIC(early_drop);
      }
      nf_ct_put(ct);
      return dropped;
}

struct nf_conn *nf_conntrack_alloc(const struct nf_conntrack_tuple *orig,
                           const struct nf_conntrack_tuple *repl)
{
      struct nf_conn *conntrack = NULL;

      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);
            if (!early_drop(hash)) {
                  atomic_dec(&nf_conntrack_count);
                  if (net_ratelimit())
                        printk(KERN_WARNING
                               "nf_conntrack: table full, dropping"
                               " packet.\n");
                  return ERR_PTR(-ENOMEM);
            }
      }

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

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

      return conntrack;
}
EXPORT_SYMBOL_GPL(nf_conntrack_alloc);

void nf_conntrack_free(struct nf_conn *conntrack)
{
      nf_ct_ext_free(conntrack);
      kmem_cache_free(nf_conntrack_cachep, conntrack);
      atomic_dec(&nf_conntrack_count);
}
EXPORT_SYMBOL_GPL(nf_conntrack_free);

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

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

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

      write_lock_bh(&nf_conntrack_lock);
      exp = nf_ct_find_expectation(tuple);
      if (exp) {
            pr_debug("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;
            if (exp->helper) {
                  help = nf_ct_helper_ext_add(conntrack, GFP_ATOMIC);
                  if (help)
                        rcu_assign_pointer(help->helper, exp->helper);
            }

#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_conntrack_helper *helper;

            helper = __nf_ct_helper_find(&repl_tuple);
            if (helper) {
                  help = nf_ct_helper_ext_add(conntrack, GFP_ATOMIC);
                  if (help)
                        rcu_assign_pointer(help->helper, helper);
            }
            NF_CT_STAT_INC(new);
      }

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

      write_unlock_bh(&nf_conntrack_lock);

      if (exp) {
            if (exp->expectfn)
                  exp->expectfn(conntrack, exp);
            nf_ct_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, 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(&tuple);
      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)) {
                  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(int 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(ignore);
            return NF_ACCEPT;
      }

      /* rcu_read_lock()ed by nf_hook_slow */
      l3proto = __nf_ct_l3proto_find((u_int16_t)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(error);
            NF_CT_STAT_INC_ATOMIC(invalid);
            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(skb, dataoff, &ctinfo, pf, hooknum)) <= 0) {
            NF_CT_STAT_INC_ATOMIC(error);
            NF_CT_STAT_INC_ATOMIC(invalid);
            return -ret;
      }

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

      if (IS_ERR(ct)) {
            /* Too stressed to deal. */
            NF_CT_STAT_INC_ATOMIC(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(invalid);
            return -ret;
      }

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

      return ret;
}
EXPORT_SYMBOL_GPL(nf_conntrack_in);

int nf_ct_invert_tuplepr(struct nf_conntrack_tuple *inverse,
                   const struct nf_conntrack_tuple *orig)
{
      int 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);
      struct nf_conntrack_helper *helper;

      write_lock_bh(&nf_conntrack_lock);
      /* 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 && help->expecting != 0))
            goto out;

      helper = __nf_ct_helper_find(newreply);
      if (helper == NULL) {
            if (help)
                  rcu_assign_pointer(help->helper, NULL);
            goto out;
      }

      if (help == NULL) {
            help = nf_ct_helper_ext_add(ct, GFP_ATOMIC);
            if (help == NULL)
                  goto out;
      } else {
            memset(&help->help, 0, sizeof(help->help));
      }

      rcu_assign_pointer(help->helper, helper);
out:
      write_unlock_bh(&nf_conntrack_lock);
}
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);

      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 - skb_network_offset(skb);

            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);
}
EXPORT_SYMBOL_GPL(__nf_ct_refresh_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(skb, CTA_PROTO_SRC_PORT, sizeof(u_int16_t),
            &tuple->src.u.tcp.port);
      NLA_PUT(skb, CTA_PROTO_DST_PORT, sizeof(u_int16_t),
            &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 = *(__be16 *)nla_data(tb[CTA_PROTO_SRC_PORT]);
      t->dst.u.tcp.port = *(__be16 *)nla_data(tb[CTA_PROTO_DST_PORT]);

      return 0;
}
EXPORT_SYMBOL_GPL(nf_ct_port_nlattr_to_tuple);
#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);
}
EXPORT_SYMBOL_GPL(__nf_conntrack_attach);

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;
      struct hlist_node *n;

      write_lock_bh(&nf_conntrack_lock);
      for (; *bucket < nf_conntrack_htable_size; (*bucket)++) {
            hlist_for_each_entry(h, n, &nf_conntrack_hash[*bucket], hnode) {
                  ct = nf_ct_tuplehash_to_ctrack(h);
                  if (iter(ct, data))
                        goto found;
            }
      }
      hlist_for_each_entry(h, n, &unconfirmed, hnode) {
            ct = nf_ct_tuplehash_to_ctrack(h);
            if (iter(ct, data))
                  set_bit(IPS_DYING_BIT, &ct->status);
      }
      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);
      }
}
EXPORT_SYMBOL_GPL(nf_ct_iterate_cleanup);

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

void nf_ct_free_hashtable(struct hlist_head *hash, int vmalloced, 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(void)
{
      nf_ct_iterate_cleanup(kill_all, NULL);
}
EXPORT_SYMBOL_GPL(nf_conntrack_flush);

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

      rcu_assign_pointer(nf_ct_destroy, NULL);

      kmem_cache_destroy(nf_conntrack_cachep);
      nf_ct_free_hashtable(nf_conntrack_hash, nf_conntrack_vmalloc,
                       nf_conntrack_htable_size);

      nf_conntrack_proto_fini();
      nf_conntrack_helper_fini();
      nf_conntrack_expect_fini();
}

struct hlist_head *nf_ct_alloc_hashtable(int *sizep, int *vmalloced)
{
      struct hlist_head *hash;
      unsigned int size, i;

      *vmalloced = 0;

      size = *sizep = roundup(*sizep, PAGE_SIZE / sizeof(struct hlist_head));
      hash = (void*)__get_free_pages(GFP_KERNEL|__GFP_NOWARN,
                               get_order(sizeof(struct hlist_head)
                                     * size));
      if (!hash) {
            *vmalloced = 1;
            printk(KERN_WARNING "nf_conntrack: falling back to vmalloc.\n");
            hash = vmalloc(sizeof(struct hlist_head) * size);
      }

      if (hash)
            for (i = 0; i < size; i++)
                  INIT_HLIST_HEAD(&hash[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, hashsize, vmalloced;
      int old_vmalloced, old_size;
      int rnd;
      struct hlist_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 = nf_ct_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 (!hlist_empty(&nf_conntrack_hash[i])) {
                  h = hlist_entry(nf_conntrack_hash[i].first,
                              struct nf_conntrack_tuple_hash, hnode);
                  hlist_del(&h->hnode);
                  bucket = __hash_conntrack(&h->tuple, hashsize, rnd);
                  hlist_add_head(&h->hnode, &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);

      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);

int __init nf_conntrack_init(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_hash = nf_ct_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;
      }

      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, 0, NULL);
      if (!nf_conntrack_cachep) {
            printk(KERN_ERR "Unable to create nf_conn slab cache\n");
            goto err_free_hash;
      }

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

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

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

      /* For use by REJECT target */
      rcu_assign_pointer(ip_ct_attach, __nf_conntrack_attach);
      rcu_assign_pointer(nf_ct_destroy, destroy_conntrack);

      /* 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_fini_expect:
      nf_conntrack_expect_fini();
out_fini_proto:
      nf_conntrack_proto_fini();
err_free_conntrack_slab:
      kmem_cache_destroy(nf_conntrack_cachep);
err_free_hash:
      nf_ct_free_hashtable(nf_conntrack_hash, nf_conntrack_vmalloc,
                       nf_conntrack_htable_size);
err_out:
      return -ENOMEM;
}

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