text: /* NAT for netfilter; shared with compatibility layer. */
  
  /* (C) 1999-2001 Paul `Rusty' Russell
   * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.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/module.h>
  #include <linux/types.h>
  #include <linux/timer.h>
  #include <linux/skbuff.h>
  #include <linux/gfp.h>
  #include <net/checksum.h>
  #include <net/icmp.h>
  #include <net/ip.h>
  #include <net/tcp.h>  /* For tcp_prot in getorigdst */
  #include <linux/icmp.h>
  #include <linux/udp.h>
  #include <linux/jhash.h>
  
  #include <linux/netfilter_ipv4.h>
  #include <net/netfilter/nf_conntrack.h>
  #include <net/netfilter/nf_conntrack_core.h>
  #include <net/netfilter/nf_nat.h>
  #include <net/netfilter/nf_nat_protocol.h>
  #include <net/netfilter/nf_nat_core.h>
  #include <net/netfilter/nf_nat_helper.h>
  #include <net/netfilter/nf_conntrack_helper.h>
  #include <net/netfilter/nf_conntrack_l3proto.h>
  #include <net/netfilter/nf_conntrack_zones.h>
  
  static DEFINE_SPINLOCK(nf_nat_lock);
  
  static struct nf_conntrack_l3proto *l3proto __read_mostly;
  
  #define MAX_IP_NAT_PROTO 256
  static const struct nf_nat_protocol __rcu *nf_nat_protos[MAX_IP_NAT_PROTO]
  						__read_mostly;
  
  static inline const struct nf_nat_protocol *
  __nf_nat_proto_find(u_int8_t protonum)
  {
  	return rcu_dereference(nf_nat_protos[protonum]);
  }
  
  /* We keep an extra hash for each conntrack, for fast searching. */
  static inline unsigned int
  hash_by_src(const struct net *net, u16 zone,
  	    const struct nf_conntrack_tuple *tuple)
  {
  	unsigned int hash;
  
  	/* Original src, to ensure we map it consistently if poss. */
  	hash = jhash_3words((__force u32)tuple->src.u3.ip,
  			    (__force u32)tuple->src.u.all ^ zone,
  			    tuple->dst.protonum, nf_conntrack_hash_rnd);
  	return ((u64)hash * net->ipv4.nat_htable_size) >> 32;
  }
  
  /* Is this tuple already taken? (not by us) */
  int
  nf_nat_used_tuple(const struct nf_conntrack_tuple *tuple,
  		  const struct nf_conn *ignored_conntrack)
  {
  	/* Conntrack tracking doesn't keep track of outgoing tuples; only
  	   incoming ones.  NAT means they don't have a fixed mapping,
  	   so we invert the tuple and look for the incoming reply.
  
  	   We could keep a separate hash if this proves too slow. */
  	struct nf_conntrack_tuple reply;
  
  	nf_ct_invert_tuplepr(&reply, tuple);
  	return nf_conntrack_tuple_taken(&reply, ignored_conntrack);
  }
  EXPORT_SYMBOL(nf_nat_used_tuple);
  
  /* If we source map this tuple so reply looks like reply_tuple, will
   * that meet the constraints of range. */
  static int
  in_range(const struct nf_conntrack_tuple *tuple,
  	 const struct nf_nat_ipv4_range *range)
  {
  	const struct nf_nat_protocol *proto;
  	int ret = 0;
  
  	/* If we are supposed to map IPs, then we must be in the
  	   range specified, otherwise let this drag us onto a new src IP. */
  	if (range->flags & NF_NAT_RANGE_MAP_IPS) {
  		if (ntohl(tuple->src.u3.ip) < ntohl(range->min_ip) ||
  		    ntohl(tuple->src.u3.ip) > ntohl(range->max_ip))
  			return 0;
  	}
  
  	rcu_read_lock();
  	proto = __nf_nat_proto_find(tuple->dst.protonum);
  	if (!(range->flags & NF_NAT_RANGE_PROTO_SPECIFIED) ||
  	    proto->in_range(tuple, NF_NAT_MANIP_SRC,
  			    &range->min, &range->max))
  		ret = 1;
  	rcu_read_unlock();
  
  	return ret;
  }
  
  static inline int
  same_src(const struct nf_conn *ct,
  	 const struct nf_conntrack_tuple *tuple)
  {
  	const struct nf_conntrack_tuple *t;
  
  	t = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
  	return (t->dst.protonum == tuple->dst.protonum &&
  		t->src.u3.ip == tuple->src.u3.ip &&
  		t->src.u.all == tuple->src.u.all);
  }
  
  /* Only called for SRC manip */
  static int
  find_appropriate_src(struct net *net, u16 zone,
  		     const struct nf_conntrack_tuple *tuple,
  		     struct nf_conntrack_tuple *result,
  		     const struct nf_nat_ipv4_range *range)
  {
  	unsigned int h = hash_by_src(net, zone, tuple);
  	const struct nf_conn_nat *nat;
  	const struct nf_conn *ct;
  	const struct hlist_node *n;
  
  	rcu_read_lock();
  	hlist_for_each_entry_rcu(nat, n, &net->ipv4.nat_bysource[h], bysource) {
  		ct = nat->ct;
  		if (same_src(ct, tuple) && nf_ct_zone(ct) == zone) {
  			/* Copy source part from reply tuple. */
  			nf_ct_invert_tuplepr(result,
  				       &ct->tuplehash[IP_CT_DIR_REPLY].tuple);
  			result->dst = tuple->dst;
  
  			if (in_range(result, range)) {
  				rcu_read_unlock();
  				return 1;
  			}
  		}
  	}
  	rcu_read_unlock();
  	return 0;
  }
  
  /* For [FUTURE] fragmentation handling, we want the least-used
     src-ip/dst-ip/proto triple.  Fairness doesn't come into it.  Thus
     if the range specifies 1.2.3.4 ports 10000-10005 and 1.2.3.5 ports
     1-65535, we don't do pro-rata allocation based on ports; we choose
     the ip with the lowest src-ip/dst-ip/proto usage.
  */
  static void
  find_best_ips_proto(u16 zone, struct nf_conntrack_tuple *tuple,
  		    const struct nf_nat_ipv4_range *range,
  		    const struct nf_conn *ct,
  		    enum nf_nat_manip_type maniptype)
  {
  	__be32 *var_ipp;
  	/* Host order */
  	u_int32_t minip, maxip, j;
  
  	/* No IP mapping?  Do nothing. */
  	if (!(range->flags & NF_NAT_RANGE_MAP_IPS))
  		return;
  
  	if (maniptype == NF_NAT_MANIP_SRC)
  		var_ipp = &tuple->src.u3.ip;
  	else
  		var_ipp = &tuple->dst.u3.ip;
  
  	/* Fast path: only one choice. */
  	if (range->min_ip == range->max_ip) {
  		*var_ipp = range->min_ip;
  		return;
  	}
  
  	/* Hashing source and destination IPs gives a fairly even
  	 * spread in practice (if there are a small number of IPs
  	 * involved, there usually aren't that many connections
  	 * anyway).  The consistency means that servers see the same
  	 * client coming from the same IP (some Internet Banking sites
  	 * like this), even across reboots. */
  	minip = ntohl(range->min_ip);
  	maxip = ntohl(range->max_ip);
  	j = jhash_2words((__force u32)tuple->src.u3.ip,
  			 range->flags & NF_NAT_RANGE_PERSISTENT ?
  				0 : (__force u32)tuple->dst.u3.ip ^ zone, 0);
  	j = ((u64)j * (maxip - minip + 1)) >> 32;
  	*var_ipp = htonl(minip + j);
  }
  
  /* Manipulate the tuple into the range given.  For NF_INET_POST_ROUTING,
   * we change the source to map into the range.  For NF_INET_PRE_ROUTING
   * and NF_INET_LOCAL_OUT, we change the destination to map into the
   * range.  It might not be possible to get a unique tuple, but we try.
   * At worst (or if we race), we will end up with a final duplicate in
   * __ip_conntrack_confirm and drop the packet. */
  static void
  get_unique_tuple(struct nf_conntrack_tuple *tuple,
  		 const struct nf_conntrack_tuple *orig_tuple,
  		 const struct nf_nat_ipv4_range *range,
  		 struct nf_conn *ct,
  		 enum nf_nat_manip_type maniptype)
  {
  	struct net *net = nf_ct_net(ct);
  	const struct nf_nat_protocol *proto;
  	u16 zone = nf_ct_zone(ct);
  
  	/* 1) If this srcip/proto/src-proto-part is currently mapped,
  	   and that same mapping gives a unique tuple within the given
  	   range, use that.
  
  	   This is only required for source (ie. NAT/masq) mappings.
  	   So far, we don't do local source mappings, so multiple
  	   manips not an issue.  */
  	if (maniptype == NF_NAT_MANIP_SRC &&
  	    !(range->flags & NF_NAT_RANGE_PROTO_RANDOM)) {
  		/* try the original tuple first */
  		if (in_range(orig_tuple, range)) {
  			if (!nf_nat_used_tuple(orig_tuple, ct)) {
  				*tuple = *orig_tuple;
  				return;
  			}
  		} else if (find_appropriate_src(net, zone, orig_tuple, tuple,
  			   range)) {
  			pr_debug("get_unique_tuple: Found current src map\n");
  			if (!nf_nat_used_tuple(tuple, ct))
  				return;
  		}
  	}
  
  	/* 2) Select the least-used IP/proto combination in the given
  	   range. */
  	*tuple = *orig_tuple;
  	find_best_ips_proto(zone, tuple, range, ct, maniptype);
  
  	/* 3) The per-protocol part of the manip is made to map into
  	   the range to make a unique tuple. */
  
  	rcu_read_lock();
  	proto = __nf_nat_proto_find(orig_tuple->dst.protonum);
  
  	/* Only bother mapping if it's not already in range and unique */
  	if (!(range->flags & NF_NAT_RANGE_PROTO_RANDOM)) {
  		if (range->flags & NF_NAT_RANGE_PROTO_SPECIFIED) {
  			if (proto->in_range(tuple, maniptype, &range->min,
  					    &range->max) &&
  			    (range->min.all == range->max.all ||
  			     !nf_nat_used_tuple(tuple, ct)))
  				goto out;
  		} else if (!nf_nat_used_tuple(tuple, ct)) {
  			goto out;
  		}
  	}
  
  	/* Last change: get protocol to try to obtain unique tuple. */
  	proto->unique_tuple(tuple, range, maniptype, ct);
  out:
  	rcu_read_unlock();
  }
  
  unsigned int
  nf_nat_setup_info(struct nf_conn *ct,
  		  const struct nf_nat_ipv4_range *range,
  		  enum nf_nat_manip_type maniptype)
  {
  	struct net *net = nf_ct_net(ct);
  	struct nf_conntrack_tuple curr_tuple, new_tuple;
  	struct nf_conn_nat *nat;
  
  	/* nat helper or nfctnetlink also setup binding */
  	nat = nfct_nat(ct);
  	if (!nat) {
  		nat = nf_ct_ext_add(ct, NF_CT_EXT_NAT, GFP_ATOMIC);
  		if (nat == NULL) {
  			pr_debug("failed to add NAT extension\n");
  			return NF_ACCEPT;
  		}
  	}
  
  	NF_CT_ASSERT(maniptype == NF_NAT_MANIP_SRC ||
  		     maniptype == NF_NAT_MANIP_DST);
  	BUG_ON(nf_nat_initialized(ct, maniptype));
  
  	/* What we've got will look like inverse of reply. Normally
  	   this is what is in the conntrack, except for prior
  	   manipulations (future optimization: if num_manips == 0,
  	   orig_tp =
  	   conntrack->tuplehash[IP_CT_DIR_ORIGINAL].tuple) */
  	nf_ct_invert_tuplepr(&curr_tuple,
  			     &ct->tuplehash[IP_CT_DIR_REPLY].tuple);
  
  	get_unique_tuple(&new_tuple, &curr_tuple, range, ct, maniptype);
  
  	if (!nf_ct_tuple_equal(&new_tuple, &curr_tuple)) {
  		struct nf_conntrack_tuple reply;
  
  		/* Alter conntrack table so will recognize replies. */
  		nf_ct_invert_tuplepr(&reply, &new_tuple);
  		nf_conntrack_alter_reply(ct, &reply);
  
  		/* Non-atomic: we own this at the moment. */
  		if (maniptype == NF_NAT_MANIP_SRC)
  			ct->status |= IPS_SRC_NAT;
  		else
  			ct->status |= IPS_DST_NAT;
  	}
  
  	if (maniptype == NF_NAT_MANIP_SRC) {
  		unsigned int srchash;
  
  		srchash = hash_by_src(net, nf_ct_zone(ct),
  				      &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
  		spin_lock_bh(&nf_nat_lock);
  		/* nf_conntrack_alter_reply might re-allocate extension area */
  		nat = nfct_nat(ct);
  		nat->ct = ct;
  		hlist_add_head_rcu(&nat->bysource,
  				   &net->ipv4.nat_bysource[srchash]);
  		spin_unlock_bh(&nf_nat_lock);
  	}
  
  	/* It's done. */
  	if (maniptype == NF_NAT_MANIP_DST)
  		ct->status |= IPS_DST_NAT_DONE;
  	else
  		ct->status |= IPS_SRC_NAT_DONE;
  
  	return NF_ACCEPT;
  }
  EXPORT_SYMBOL(nf_nat_setup_info);
  
  /* Returns true if succeeded. */
  static bool
  manip_pkt(u_int16_t proto,
  	  struct sk_buff *skb,
  	  unsigned int iphdroff,
  	  const struct nf_conntrack_tuple *target,
  	  enum nf_nat_manip_type maniptype)
  {
  	struct iphdr *iph;
  	const struct nf_nat_protocol *p;
  
  	if (!skb_make_writable(skb, iphdroff + sizeof(*iph)))
  		return false;
  
  	iph = (void *)skb->data + iphdroff;
  
  	/* Manipulate protcol part. */
  
  	/* rcu_read_lock()ed by nf_hook_slow */
  	p = __nf_nat_proto_find(proto);
  	if (!p->manip_pkt(skb, iphdroff, target, maniptype))
  		return false;
  
  	iph = (void *)skb->data + iphdroff;
  
  	if (maniptype == NF_NAT_MANIP_SRC) {
  		csum_replace4(&iph->check, iph->saddr, target->src.u3.ip);
  		iph->saddr = target->src.u3.ip;
  	} else {
  		csum_replace4(&iph->check, iph->daddr, target->dst.u3.ip);
  		iph->daddr = target->dst.u3.ip;
  	}
  	return true;
  }
  
  /* Do packet manipulations according to nf_nat_setup_info. */
  unsigned int nf_nat_packet(struct nf_conn *ct,
  			   enum ip_conntrack_info ctinfo,
  			   unsigned int hooknum,
  			   struct sk_buff *skb)
  {
  	enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
  	unsigned long statusbit;
  	enum nf_nat_manip_type mtype = HOOK2MANIP(hooknum);
  
  	if (mtype == NF_NAT_MANIP_SRC)
  		statusbit = IPS_SRC_NAT;
  	else
  		statusbit = IPS_DST_NAT;
  
  	/* Invert if this is reply dir. */
  	if (dir == IP_CT_DIR_REPLY)
  		statusbit ^= IPS_NAT_MASK;
  
  	/* Non-atomic: these bits don't change. */
  	if (ct->status & statusbit) {
  		struct nf_conntrack_tuple target;
  
  		/* We are aiming to look like inverse of other direction. */
  		nf_ct_invert_tuplepr(&target, &ct->tuplehash[!dir].tuple);
  
  		if (!manip_pkt(target.dst.protonum, skb, 0, &target, mtype))
  			return NF_DROP;
  	}
  	return NF_ACCEPT;
  }
  EXPORT_SYMBOL_GPL(nf_nat_packet);
  
  /* Dir is direction ICMP is coming from (opposite to packet it contains) */
  int nf_nat_icmp_reply_translation(struct nf_conn *ct,
  				  enum ip_conntrack_info ctinfo,
  				  unsigned int hooknum,
  				  struct sk_buff *skb)
  {
  	struct {
  		struct icmphdr icmp;
  		struct iphdr ip;
  	} *inside;
  	struct nf_conntrack_tuple target;
  	int hdrlen = ip_hdrlen(skb);
  	enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
  	unsigned long statusbit;
  	enum nf_nat_manip_type manip = HOOK2MANIP(hooknum);
  
  	if (!skb_make_writable(skb, hdrlen + sizeof(*inside)))
  		return 0;
  
  	inside = (void *)skb->data + hdrlen;
  
  	/* We're actually going to mangle it beyond trivial checksum
  	   adjustment, so make sure the current checksum is correct. */
  	if (nf_ip_checksum(skb, hooknum, hdrlen, 0))
  		return 0;
  
  	/* Must be RELATED */
  	NF_CT_ASSERT(skb->nfctinfo == IP_CT_RELATED ||
  		     skb->nfctinfo == IP_CT_RELATED_REPLY);
  
  	/* Redirects on non-null nats must be dropped, else they'll
  	   start talking to each other without our translation, and be
  	   confused... --RR */
  	if (inside->icmp.type == ICMP_REDIRECT) {
  		/* If NAT isn't finished, assume it and drop. */
  		if ((ct->status & IPS_NAT_DONE_MASK) != IPS_NAT_DONE_MASK)
  			return 0;
  
  		if (ct->status & IPS_NAT_MASK)
  			return 0;
  	}
  
  	if (manip == NF_NAT_MANIP_SRC)
  		statusbit = IPS_SRC_NAT;
  	else
  		statusbit = IPS_DST_NAT;
  
  	/* Invert if this is reply dir. */
  	if (dir == IP_CT_DIR_REPLY)
  		statusbit ^= IPS_NAT_MASK;
  
  	if (!(ct->status & statusbit))
  		return 1;
  
  	pr_debug("icmp_reply_translation: translating error %p manip %u "
  		 "dir %s\n", skb, manip,
  		 dir == IP_CT_DIR_ORIGINAL ? "ORIG" : "REPLY");
  
  	/* Change inner back to look like incoming packet.  We do the
  	   opposite manip on this hook to normal, because it might not
  	   pass all hooks (locally-generated ICMP).  Consider incoming
  	   packet: PREROUTING (DST manip), routing produces ICMP, goes
  	   through POSTROUTING (which must correct the DST manip). */
  	if (!manip_pkt(inside->ip.protocol, skb, hdrlen + sizeof(inside->icmp),
  		       &ct->tuplehash[!dir].tuple, !manip))
  		return 0;
  
  	if (skb->ip_summed != CHECKSUM_PARTIAL) {
  		/* Reloading "inside" here since manip_pkt inner. */
  		inside = (void *)skb->data + hdrlen;
  		inside->icmp.checksum = 0;
  		inside->icmp.checksum =
  			csum_fold(skb_checksum(skb, hdrlen,
  					       skb->len - hdrlen, 0));
  	}
  
  	/* Change outer to look the reply to an incoming packet
  	 * (proto 0 means don't invert per-proto part). */
  	nf_ct_invert_tuplepr(&target, &ct->tuplehash[!dir].tuple);
  	if (!manip_pkt(0, skb, 0, &target, manip))
  		return 0;
  
  	return 1;
  }
  EXPORT_SYMBOL_GPL(nf_nat_icmp_reply_translation);
  
  /* Protocol registration. */
  int nf_nat_protocol_register(const struct nf_nat_protocol *proto)
  {
  	int ret = 0;
  
  	spin_lock_bh(&nf_nat_lock);
  	if (rcu_dereference_protected(
  			nf_nat_protos[proto->protonum],
  			lockdep_is_held(&nf_nat_lock)
  			) != &nf_nat_unknown_protocol) {
  		ret = -EBUSY;
  		goto out;
  	}
  	RCU_INIT_POINTER(nf_nat_protos[proto->protonum], proto);
   out:
  	spin_unlock_bh(&nf_nat_lock);
  	return ret;
  }
  EXPORT_SYMBOL(nf_nat_protocol_register);
  
  /* No one stores the protocol anywhere; simply delete it. */
  void nf_nat_protocol_unregister(const struct nf_nat_protocol *proto)
  {
  	spin_lock_bh(&nf_nat_lock);
  	RCU_INIT_POINTER(nf_nat_protos[proto->protonum],
  			   &nf_nat_unknown_protocol);
  	spin_unlock_bh(&nf_nat_lock);
  	synchronize_rcu();
  }
  EXPORT_SYMBOL(nf_nat_protocol_unregister);
  
  /* No one using conntrack by the time this called. */
  static void nf_nat_cleanup_conntrack(struct nf_conn *ct)
  {
  	struct nf_conn_nat *nat = nf_ct_ext_find(ct, NF_CT_EXT_NAT);
  
  	if (nat == NULL || nat->ct == NULL)
  		return;
  
  	NF_CT_ASSERT(nat->ct->status & IPS_SRC_NAT_DONE);
  
  	spin_lock_bh(&nf_nat_lock);
  	hlist_del_rcu(&nat->bysource);
  	spin_unlock_bh(&nf_nat_lock);
  }
  
  static void nf_nat_move_storage(void *new, void *old)
  {
  	struct nf_conn_nat *new_nat = new;
  	struct nf_conn_nat *old_nat = old;
  	struct nf_conn *ct = old_nat->ct;
  
  	if (!ct || !(ct->status & IPS_SRC_NAT_DONE))
  		return;
  
  	spin_lock_bh(&nf_nat_lock);
  	hlist_replace_rcu(&old_nat->bysource, &new_nat->bysource);
  	spin_unlock_bh(&nf_nat_lock);
  }
  
  static struct nf_ct_ext_type nat_extend __read_mostly = {
  	.len		= sizeof(struct nf_conn_nat),
  	.align		= __alignof__(struct nf_conn_nat),
  	.destroy	= nf_nat_cleanup_conntrack,
  	.move		= nf_nat_move_storage,
  	.id		= NF_CT_EXT_NAT,
  	.flags		= NF_CT_EXT_F_PREALLOC,
  };
  
  #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
  
  #include <linux/netfilter/nfnetlink.h>
  #include <linux/netfilter/nfnetlink_conntrack.h>
  
  static const struct nla_policy protonat_nla_policy[CTA_PROTONAT_MAX+1] = {
  	[CTA_PROTONAT_PORT_MIN]	= { .type = NLA_U16 },
  	[CTA_PROTONAT_PORT_MAX]	= { .type = NLA_U16 },
  };
  
  static int nfnetlink_parse_nat_proto(struct nlattr *attr,
  				     const struct nf_conn *ct,
  				     struct nf_nat_ipv4_range *range)
  {
  	struct nlattr *tb[CTA_PROTONAT_MAX+1];
  	const struct nf_nat_protocol *npt;
  	int err;
  
  	err = nla_parse_nested(tb, CTA_PROTONAT_MAX, attr, protonat_nla_policy);
  	if (err < 0)
  		return err;
  
  	rcu_read_lock();
  	npt = __nf_nat_proto_find(nf_ct_protonum(ct));
  	if (npt->nlattr_to_range)
  		err = npt->nlattr_to_range(tb, range);
  	rcu_read_unlock();
  	return err;
  }
  
  static const struct nla_policy nat_nla_policy[CTA_NAT_MAX+1] = {
  	[CTA_NAT_MINIP]		= { .type = NLA_U32 },
  	[CTA_NAT_MAXIP]		= { .type = NLA_U32 },
  	[CTA_NAT_PROTO]		= { .type = NLA_NESTED },
  };
  
  static int
  nfnetlink_parse_nat(const struct nlattr *nat,
  		    const struct nf_conn *ct, struct nf_nat_ipv4_range *range)
  {
  	struct nlattr *tb[CTA_NAT_MAX+1];
  	int err;
  
  	memset(range, 0, sizeof(*range));
  
  	err = nla_parse_nested(tb, CTA_NAT_MAX, nat, nat_nla_policy);
  	if (err < 0)
  		return err;
  
  	if (tb[CTA_NAT_MINIP])
  		range->min_ip = nla_get_be32(tb[CTA_NAT_MINIP]);
  
  	if (!tb[CTA_NAT_MAXIP])
  		range->max_ip = range->min_ip;
  	else
  		range->max_ip = nla_get_be32(tb[CTA_NAT_MAXIP]);
  
  	if (range->min_ip)
  		range->flags |= NF_NAT_RANGE_MAP_IPS;
  
  	if (!tb[CTA_NAT_PROTO])
  		return 0;
  
  	err = nfnetlink_parse_nat_proto(tb[CTA_NAT_PROTO], ct, range);
  	if (err < 0)
  		return err;
  
  	return 0;
  }
  
  static int
  nfnetlink_parse_nat_setup(struct nf_conn *ct,
  			  enum nf_nat_manip_type manip,
  			  const struct nlattr *attr)
  {
  	struct nf_nat_ipv4_range range;
  
  	if (nfnetlink_parse_nat(attr, ct, &range) < 0)
  		return -EINVAL;
  	if (nf_nat_initialized(ct, manip))
  		return -EEXIST;
  
  	return nf_nat_setup_info(ct, &range, manip);
  }
  #else
  static int
  nfnetlink_parse_nat_setup(struct nf_conn *ct,
  			  enum nf_nat_manip_type manip,
  			  const struct nlattr *attr)
  {
  	return -EOPNOTSUPP;
  }
  #endif
  
  static int __net_init nf_nat_net_init(struct net *net)
  {
  	/* Leave them the same for the moment. */
  	net->ipv4.nat_htable_size = net->ct.htable_size;
  	net->ipv4.nat_bysource = nf_ct_alloc_hashtable(&net->ipv4.nat_htable_size, 0);
  	if (!net->ipv4.nat_bysource)
  		return -ENOMEM;
  	return 0;
  }
  
  /* Clear NAT section of all conntracks, in case we're loaded again. */
  static int clean_nat(struct nf_conn *i, void *data)
  {
  	struct nf_conn_nat *nat = nfct_nat(i);
  
  	if (!nat)
  		return 0;
  	memset(nat, 0, sizeof(*nat));
  	i->status &= ~(IPS_NAT_MASK | IPS_NAT_DONE_MASK | IPS_SEQ_ADJUST);
  	return 0;
  }
  
  static void __net_exit nf_nat_net_exit(struct net *net)
  {
  	nf_ct_iterate_cleanup(net, &clean_nat, NULL);
  	synchronize_rcu();
  	nf_ct_free_hashtable(net->ipv4.nat_bysource, net->ipv4.nat_htable_size);
  }
  
  static struct pernet_operations nf_nat_net_ops = {
  	.init = nf_nat_net_init,
  	.exit = nf_nat_net_exit,
  };
  
  static struct nf_ct_helper_expectfn follow_master_nat = {
  	.name		= "nat-follow-master",
  	.expectfn	= nf_nat_follow_master,
  };
  
  static struct nfq_ct_nat_hook nfq_ct_nat = {
  	.seq_adjust	= nf_nat_tcp_seq_adjust,
  };
  
  static int __init nf_nat_init(void)
  {
  	size_t i;
  	int ret;
  
  	need_ipv4_conntrack();
  
  	ret = nf_ct_extend_register(&nat_extend);
  	if (ret < 0) {
  		printk(KERN_ERR "nf_nat_core: Unable to register extension\n");
  		return ret;
  	}
  
  	ret = register_pernet_subsys(&nf_nat_net_ops);
  	if (ret < 0)
  		goto cleanup_extend;
  
  	/* Sew in builtin protocols. */
  	spin_lock_bh(&nf_nat_lock);
  	for (i = 0; i < MAX_IP_NAT_PROTO; i++)
  		RCU_INIT_POINTER(nf_nat_protos[i], &nf_nat_unknown_protocol);
  	RCU_INIT_POINTER(nf_nat_protos[IPPROTO_TCP], &nf_nat_protocol_tcp);
  	RCU_INIT_POINTER(nf_nat_protos[IPPROTO_UDP], &nf_nat_protocol_udp);
  	RCU_INIT_POINTER(nf_nat_protos[IPPROTO_ICMP], &nf_nat_protocol_icmp);
  	spin_unlock_bh(&nf_nat_lock);
  
  	/* Initialize fake conntrack so that NAT will skip it */
  	nf_ct_untracked_status_or(IPS_NAT_DONE_MASK);
  
  	l3proto = nf_ct_l3proto_find_get((u_int16_t)AF_INET);
  
  	nf_ct_helper_expectfn_register(&follow_master_nat);
  
  	BUG_ON(nf_nat_seq_adjust_hook != NULL);
  	RCU_INIT_POINTER(nf_nat_seq_adjust_hook, nf_nat_seq_adjust);
  	BUG_ON(nfnetlink_parse_nat_setup_hook != NULL);
  	RCU_INIT_POINTER(nfnetlink_parse_nat_setup_hook,
  			   nfnetlink_parse_nat_setup);
  	BUG_ON(nf_ct_nat_offset != NULL);
  	RCU_INIT_POINTER(nf_ct_nat_offset, nf_nat_get_offset);
  	RCU_INIT_POINTER(nfq_ct_nat_hook, &nfq_ct_nat);
  	return 0;
  
   cleanup_extend:
  	nf_ct_extend_unregister(&nat_extend);
  	return ret;
  }
  
  static void __exit nf_nat_cleanup(void)
  {
  	unregister_pernet_subsys(&nf_nat_net_ops);
  	nf_ct_l3proto_put(l3proto);
  	nf_ct_extend_unregister(&nat_extend);
  	nf_ct_helper_expectfn_unregister(&follow_master_nat);
  	RCU_INIT_POINTER(nf_nat_seq_adjust_hook, NULL);
  	RCU_INIT_POINTER(nfnetlink_parse_nat_setup_hook, NULL);
  	RCU_INIT_POINTER(nf_ct_nat_offset, NULL);
  	RCU_INIT_POINTER(nfq_ct_nat_hook, NULL);
  	synchronize_net();
  }
  
  MODULE_LICENSE("GPL");
  MODULE_ALIAS("nf-nat-ipv4");
  
  module_init(nf_nat_init);
  module_exit(nf_nat_cleanup);
  