1 files changed, 779 insertions, 0 deletions

diff --git a/net/ipv4/netfilter/nf_nat_core.c b/net/ipv4/netfilter/nf_nat_core.c
new file mode 100644
index 00000000..3346de5d
--- /dev/null
+++ b/net/ipv4/netfilter/nf_nat_core.c
@@ -0,0 +1,779 @@
+/* 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_l4proto.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, 0);
+	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_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 & IP_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 & IP_NAT_RANGE_PROTO_SPECIFIED) ||
+	    proto->in_range(tuple, IP_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_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_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 & IP_NAT_RANGE_MAP_IPS))
+		return;
+
+	if (maniptype == IP_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 & IP_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_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 == IP_NAT_MANIP_SRC &&
+	    !(range->flags & IP_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 & IP_NAT_RANGE_PROTO_RANDOM)) {
+		if (range->flags & IP_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_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 == IP_NAT_MANIP_SRC ||
+		     maniptype == IP_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 == IP_NAT_MANIP_SRC)
+			ct->status |= IPS_SRC_NAT;
+		else
+			ct->status |= IPS_DST_NAT;
+	}
+
+	if (maniptype == IP_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 exntension aera */
+		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 == IP_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 == IP_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 == IP_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;
+	const struct nf_conntrack_l4proto *l4proto;
+	struct nf_conntrack_tuple inner, 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 == IP_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");
+
+	/* rcu_read_lock()ed by nf_hook_slow */
+	l4proto = __nf_ct_l4proto_find(PF_INET, inside->ip.protocol);
+
+	if (!nf_ct_get_tuple(skb, hdrlen + sizeof(struct icmphdr),
+			     (hdrlen +
+			      sizeof(struct icmphdr) + inside->ip.ihl * 4),
+			     (u_int16_t)AF_INET, inside->ip.protocol,
+			     &inner, l3proto, l4proto))
+		return 0;
+
+	/* 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_assign_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_assign_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 nf_nat_protocol *
+nf_nat_proto_find_get(u_int8_t protonum)
+{
+	const struct nf_nat_protocol *p;
+
+	rcu_read_lock();
+	p = __nf_nat_proto_find(protonum);
+	if (!try_module_get(p->me))
+		p = &nf_nat_unknown_protocol;
+	rcu_read_unlock();
+
+	return p;
+}
+
+static void
+nf_nat_proto_put(const struct nf_nat_protocol *p)
+{
+	module_put(p->me);
+}
+
+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_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;
+
+	npt = nf_nat_proto_find_get(nf_ct_protonum(ct));
+	if (npt->nlattr_to_range)
+		err = npt->nlattr_to_range(tb, range);
+	nf_nat_proto_put(npt);
+	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 },
+};
+
+static int
+nfnetlink_parse_nat(const struct nlattr *nat,
+		    const struct nf_conn *ct, struct nf_nat_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 |= IP_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_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 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_assign_pointer(nf_nat_protos[i], &nf_nat_unknown_protocol);
+	rcu_assign_pointer(nf_nat_protos[IPPROTO_TCP], &nf_nat_protocol_tcp);
+	rcu_assign_pointer(nf_nat_protos[IPPROTO_UDP], &nf_nat_protocol_udp);
+	rcu_assign_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);
+
+	BUG_ON(nf_nat_seq_adjust_hook != NULL);
+	rcu_assign_pointer(nf_nat_seq_adjust_hook, nf_nat_seq_adjust);
+	BUG_ON(nfnetlink_parse_nat_setup_hook != NULL);
+	rcu_assign_pointer(nfnetlink_parse_nat_setup_hook,
+			   nfnetlink_parse_nat_setup);
+	BUG_ON(nf_ct_nat_offset != NULL);
+	rcu_assign_pointer(nf_ct_nat_offset, nf_nat_get_offset);
+	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);
+	rcu_assign_pointer(nf_nat_seq_adjust_hook, NULL);
+	rcu_assign_pointer(nfnetlink_parse_nat_setup_hook, NULL);
+	rcu_assign_pointer(nf_ct_nat_offset, NULL);
+	synchronize_net();
+}
+
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("nf-nat-ipv4");
+
+module_init(nf_nat_init);
+module_exit(nf_nat_cleanup);