net/ipv6/netfilter/nf_nat_l3proto_ipv6.c - kernel/common.git - Git at Google

 /*
  * Copyright (c) 2011 Patrick McHardy <kaber@trash.net>
  *
  * 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.
  *
  * Development of IPv6 NAT funded by Astaro.
  */
 #include <linux/types.h>
 #include <linux/module.h>
 #include <linux/skbuff.h>
 #include <linux/ipv6.h>
 #include <linux/netfilter.h>
 #include <linux/netfilter_ipv6.h>
 #include <net/secure_seq.h>
 #include <net/checksum.h>
 #include <net/ip6_checksum.h>
 #include <net/ip6_route.h>
 #include <net/ipv6.h>

 #include <net/netfilter/nf_conntrack_core.h>
 #include <net/netfilter/nf_conntrack.h>
 #include <net/netfilter/nf_nat_core.h>
 #include <net/netfilter/nf_nat_l3proto.h>
 #include <net/netfilter/nf_nat_l4proto.h>

 static const struct nf_nat_l3proto nf_nat_l3proto_ipv6;

 #ifdef CONFIG_XFRM
 static void nf_nat_ipv6_decode_session(struct sk_buff *skb,
 				       const struct nf_conn *ct,
 				       enum ip_conntrack_dir dir,
 				       unsigned long statusbit,
 				       struct flowi *fl)
 {
 	const struct nf_conntrack_tuple *t = &ct->tuplehash[dir].tuple;
 	struct flowi6 *fl6 = &fl->u.ip6;

 	if (ct->status & statusbit) {
 		fl6->daddr = t->dst.u3.in6;
 		if (t->dst.protonum == IPPROTO_TCP ||
 		    t->dst.protonum == IPPROTO_UDP ||
 		    t->dst.protonum == IPPROTO_UDPLITE ||
 		    t->dst.protonum == IPPROTO_DCCP ||
 		    t->dst.protonum == IPPROTO_SCTP)
 			fl6->fl6_dport = t->dst.u.all;
 	}

 	statusbit ^= IPS_NAT_MASK;

 	if (ct->status & statusbit) {
 		fl6->saddr = t->src.u3.in6;
 		if (t->dst.protonum == IPPROTO_TCP ||
 		    t->dst.protonum == IPPROTO_UDP ||
 		    t->dst.protonum == IPPROTO_UDPLITE ||
 		    t->dst.protonum == IPPROTO_DCCP ||
 		    t->dst.protonum == IPPROTO_SCTP)
 			fl6->fl6_sport = t->src.u.all;
 	}
 }
 #endif

 static bool nf_nat_ipv6_in_range(const struct nf_conntrack_tuple *t,
 				 const struct nf_nat_range *range)
 {
 	return ipv6_addr_cmp(&t->src.u3.in6, &range->min_addr.in6) >= 0 &&
 	       ipv6_addr_cmp(&t->src.u3.in6, &range->max_addr.in6) <= 0;
 }

 static u32 nf_nat_ipv6_secure_port(const struct nf_conntrack_tuple *t,
 				   __be16 dport)
 {
 	return secure_ipv6_port_ephemeral(t->src.u3.ip6, t->dst.u3.ip6, dport);
 }

 static bool nf_nat_ipv6_manip_pkt(struct sk_buff *skb,
 				  unsigned int iphdroff,
 				  const struct nf_nat_l4proto *l4proto,
 				  const struct nf_conntrack_tuple *target,
 				  enum nf_nat_manip_type maniptype)
 {
 	struct ipv6hdr *ipv6h;
 	__be16 frag_off;
 	int hdroff;
 	u8 nexthdr;

 	if (!skb_make_writable(skb, iphdroff + sizeof(*ipv6h)))
 		return false;

 	ipv6h = (void *)skb->data + iphdroff;
 	nexthdr = ipv6h->nexthdr;
 	hdroff = ipv6_skip_exthdr(skb, iphdroff + sizeof(*ipv6h),
 				  &nexthdr, &frag_off);
 	if (hdroff < 0)
 		goto manip_addr;

 	if ((frag_off & htons(~0x7)) == 0 &&
 	    !l4proto->manip_pkt(skb, &nf_nat_l3proto_ipv6, iphdroff, hdroff,
 				target, maniptype))
 		return false;

 	/* must reload, offset might have changed */
 	ipv6h = (void *)skb->data + iphdroff;

 manip_addr:
 	if (maniptype == NF_NAT_MANIP_SRC)
 		ipv6h->saddr = target->src.u3.in6;
 	else
 		ipv6h->daddr = target->dst.u3.in6;

 	return true;
 }

 static void nf_nat_ipv6_csum_update(struct sk_buff *skb,
 				    unsigned int iphdroff, __sum16 *check,
 				    const struct nf_conntrack_tuple *t,
 				    enum nf_nat_manip_type maniptype)
 {
 	const struct ipv6hdr *ipv6h = (struct ipv6hdr *)(skb->data + iphdroff);
 	const struct in6_addr *oldip, *newip;

 	if (maniptype == NF_NAT_MANIP_SRC) {
 		oldip = &ipv6h->saddr;
 		newip = &t->src.u3.in6;
 	} else {
 		oldip = &ipv6h->daddr;
 		newip = &t->dst.u3.in6;
 	}
 	inet_proto_csum_replace16(check, skb, oldip->s6_addr32,
 				  newip->s6_addr32, true);
 }

 static void nf_nat_ipv6_csum_recalc(struct sk_buff *skb,
 				    u8 proto, void *data, __sum16 *check,
 				    int datalen, int oldlen)
 {
 	if (skb->ip_summed != CHECKSUM_PARTIAL) {
 		const struct ipv6hdr *ipv6h = ipv6_hdr(skb);

 		skb->ip_summed = CHECKSUM_PARTIAL;
 		skb->csum_start = skb_headroom(skb) + skb_network_offset(skb) +
 			(data - (void *)skb->data);
 		skb->csum_offset = (void *)check - data;
 		*check = ~csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr,
 					  datalen, proto, 0);
 	} else
 		inet_proto_csum_replace2(check, skb,
 					 htons(oldlen), htons(datalen), true);
 }

 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
 static int nf_nat_ipv6_nlattr_to_range(struct nlattr *tb[],
 				       struct nf_nat_range *range)
 {
 	if (tb[CTA_NAT_V6_MINIP]) {
 		nla_memcpy(&range->min_addr.ip6, tb[CTA_NAT_V6_MINIP],
 			   sizeof(struct in6_addr));
 		range->flags |= NF_NAT_RANGE_MAP_IPS;
 	}

 	if (tb[CTA_NAT_V6_MAXIP])
 		nla_memcpy(&range->max_addr.ip6, tb[CTA_NAT_V6_MAXIP],
 			   sizeof(struct in6_addr));
 	else
 		range->max_addr = range->min_addr;

 	return 0;
 }
 #endif

 static const struct nf_nat_l3proto nf_nat_l3proto_ipv6 = {
 	.l3proto		= NFPROTO_IPV6,
 	.secure_port		= nf_nat_ipv6_secure_port,
 	.in_range		= nf_nat_ipv6_in_range,
 	.manip_pkt		= nf_nat_ipv6_manip_pkt,
 	.csum_update		= nf_nat_ipv6_csum_update,
 	.csum_recalc		= nf_nat_ipv6_csum_recalc,
 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
 	.nlattr_to_range	= nf_nat_ipv6_nlattr_to_range,
 #endif
 #ifdef CONFIG_XFRM
 	.decode_session	= nf_nat_ipv6_decode_session,
 #endif
 };

 int nf_nat_icmpv6_reply_translation(struct sk_buff *skb,
 				    struct nf_conn *ct,
 				    enum ip_conntrack_info ctinfo,
 				    unsigned int hooknum,
 				    unsigned int hdrlen)
 {
 	struct {
 		struct icmp6hdr	icmp6;
 		struct ipv6hdr	ip6;
 	} *inside;
 	enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
 	enum nf_nat_manip_type manip = HOOK2MANIP(hooknum);
 	const struct nf_nat_l4proto *l4proto;
 	struct nf_conntrack_tuple target;
 	unsigned long statusbit;

 	WARN_ON(ctinfo != IP_CT_RELATED && ctinfo != IP_CT_RELATED_REPLY);

 	if (!skb_make_writable(skb, hdrlen + sizeof(*inside)))
 		return 0;
 	if (nf_ip6_checksum(skb, hooknum, hdrlen, IPPROTO_ICMPV6))
 		return 0;

 	inside = (void *)skb->data + hdrlen;
 	if (inside->icmp6.icmp6_type == NDISC_REDIRECT) {
 		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 direction */
 	if (dir == IP_CT_DIR_REPLY)
 		statusbit ^= IPS_NAT_MASK;

 	if (!(ct->status & statusbit))
 		return 1;

 	l4proto = __nf_nat_l4proto_find(NFPROTO_IPV6, inside->ip6.nexthdr);
 	if (!nf_nat_ipv6_manip_pkt(skb, hdrlen + sizeof(inside->icmp6),
 				   l4proto, &ct->tuplehash[!dir].tuple, !manip))
 		return 0;

 	if (skb->ip_summed != CHECKSUM_PARTIAL) {
 		struct ipv6hdr *ipv6h = ipv6_hdr(skb);
 		inside = (void *)skb->data + hdrlen;
 		inside->icmp6.icmp6_cksum = 0;
 		inside->icmp6.icmp6_cksum =
 			csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr,
 					skb->len - hdrlen, IPPROTO_ICMPV6,
 					skb_checksum(skb, hdrlen,
 						     skb->len - hdrlen, 0));
 	}

 	nf_ct_invert_tuplepr(&target, &ct->tuplehash[!dir].tuple);
 	l4proto = __nf_nat_l4proto_find(NFPROTO_IPV6, IPPROTO_ICMPV6);
 	if (!nf_nat_ipv6_manip_pkt(skb, 0, l4proto, &target, manip))
 		return 0;

 	return 1;
 }
 EXPORT_SYMBOL_GPL(nf_nat_icmpv6_reply_translation);

 unsigned int
 nf_nat_ipv6_fn(void *priv, struct sk_buff *skb,
 	       const struct nf_hook_state *state,
 	       unsigned int (*do_chain)(void *priv,
 					struct sk_buff *skb,
 					const struct nf_hook_state *state,
 					struct nf_conn *ct))
 {
 	struct nf_conn *ct;
 	enum ip_conntrack_info ctinfo;
 	struct nf_conn_nat *nat;
 	enum nf_nat_manip_type maniptype = HOOK2MANIP(state->hook);
 	__be16 frag_off;
 	int hdrlen;
 	u8 nexthdr;

 	ct = nf_ct_get(skb, &ctinfo);
 	/* Can't track?  It's not due to stress, or conntrack would
 	 * have dropped it.  Hence it's the user's responsibilty to
 	 * packet filter it out, or implement conntrack/NAT for that
 	 * protocol. 8) --RR
 	 */
 	if (!ct)
 		return NF_ACCEPT;

 	nat = nfct_nat(ct);

 	switch (ctinfo) {
 	case IP_CT_RELATED:
 	case IP_CT_RELATED_REPLY:
 		nexthdr = ipv6_hdr(skb)->nexthdr;
 		hdrlen = ipv6_skip_exthdr(skb, sizeof(struct ipv6hdr),
 					  &nexthdr, &frag_off);

 		if (hdrlen >= 0 && nexthdr == IPPROTO_ICMPV6) {
 			if (!nf_nat_icmpv6_reply_translation(skb, ct, ctinfo,
 							     state->hook,
 							     hdrlen))
 				return NF_DROP;
 			else
 				return NF_ACCEPT;
 		}
 		/* Fall thru... (Only ICMPs can be IP_CT_IS_REPLY) */
 	case IP_CT_NEW:
 		/* Seen it before?  This can happen for loopback, retrans,
 		 * or local packets.
 		 */
 		if (!nf_nat_initialized(ct, maniptype)) {
 			unsigned int ret;

 			ret = do_chain(priv, skb, state, ct);
 			if (ret != NF_ACCEPT)
 				return ret;

 			if (nf_nat_initialized(ct, HOOK2MANIP(state->hook)))
 				break;

 			ret = nf_nat_alloc_null_binding(ct, state->hook);
 			if (ret != NF_ACCEPT)
 				return ret;
 		} else {
 			pr_debug("Already setup manip %s for ct %p\n",
 				 maniptype == NF_NAT_MANIP_SRC ? "SRC" : "DST",
 				 ct);
 			if (nf_nat_oif_changed(state->hook, ctinfo, nat, state->out))
 				goto oif_changed;
 		}
 		break;

 	default:
 		/* ESTABLISHED */
 		WARN_ON(ctinfo != IP_CT_ESTABLISHED &&
 			ctinfo != IP_CT_ESTABLISHED_REPLY);
 		if (nf_nat_oif_changed(state->hook, ctinfo, nat, state->out))
 			goto oif_changed;
 	}

 	return nf_nat_packet(ct, ctinfo, state->hook, skb);

 oif_changed:
 	nf_ct_kill_acct(ct, ctinfo, skb);
 	return NF_DROP;
 }
 EXPORT_SYMBOL_GPL(nf_nat_ipv6_fn);

 unsigned int
 nf_nat_ipv6_in(void *priv, struct sk_buff *skb,
 	       const struct nf_hook_state *state,
 	       unsigned int (*do_chain)(void *priv,
 					struct sk_buff *skb,
 					const struct nf_hook_state *state,
 					struct nf_conn *ct))
 {
 	unsigned int ret;
 	struct in6_addr daddr = ipv6_hdr(skb)->daddr;

 	ret = nf_nat_ipv6_fn(priv, skb, state, do_chain);
 	if (ret != NF_DROP && ret != NF_STOLEN &&
 	    ipv6_addr_cmp(&daddr, &ipv6_hdr(skb)->daddr))
 		skb_dst_drop(skb);

 	return ret;
 }
 EXPORT_SYMBOL_GPL(nf_nat_ipv6_in);

 unsigned int
 nf_nat_ipv6_out(void *priv, struct sk_buff *skb,
 		const struct nf_hook_state *state,
 		unsigned int (*do_chain)(void *priv,
 					 struct sk_buff *skb,
 					 const struct nf_hook_state *state,
 					 struct nf_conn *ct))
 {
 #ifdef CONFIG_XFRM
 	const struct nf_conn *ct;
 	enum ip_conntrack_info ctinfo;
 	int err;
 #endif
 	unsigned int ret;

 	/* root is playing with raw sockets. */
 	if (skb->len < sizeof(struct ipv6hdr))
 		return NF_ACCEPT;

 	ret = nf_nat_ipv6_fn(priv, skb, state, do_chain);
 #ifdef CONFIG_XFRM
 	if (ret != NF_DROP && ret != NF_STOLEN &&
 	    !(IP6CB(skb)->flags & IP6SKB_XFRM_TRANSFORMED) &&
 	    (ct = nf_ct_get(skb, &ctinfo)) != NULL) {
 		enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);

 		if (!nf_inet_addr_cmp(&ct->tuplehash[dir].tuple.src.u3,
 				      &ct->tuplehash[!dir].tuple.dst.u3) ||
 		    (ct->tuplehash[dir].tuple.dst.protonum != IPPROTO_ICMPV6 &&
 		     ct->tuplehash[dir].tuple.src.u.all !=
 		     ct->tuplehash[!dir].tuple.dst.u.all)) {
 			err = nf_xfrm_me_harder(state->net, skb, AF_INET6);
 			if (err < 0)
 				ret = NF_DROP_ERR(err);
 		}
 	}
 #endif
 	return ret;
 }
 EXPORT_SYMBOL_GPL(nf_nat_ipv6_out);

 unsigned int
 nf_nat_ipv6_local_fn(void *priv, struct sk_buff *skb,
 		     const struct nf_hook_state *state,
 		     unsigned int (*do_chain)(void *priv,
 					      struct sk_buff *skb,
 					      const struct nf_hook_state *state,
 					      struct nf_conn *ct))
 {
 	const struct nf_conn *ct;
 	enum ip_conntrack_info ctinfo;
 	unsigned int ret;
 	int err;

 	/* root is playing with raw sockets. */
 	if (skb->len < sizeof(struct ipv6hdr))
 		return NF_ACCEPT;

 	ret = nf_nat_ipv6_fn(priv, skb, state, do_chain);
 	if (ret != NF_DROP && ret != NF_STOLEN &&
 	    (ct = nf_ct_get(skb, &ctinfo)) != NULL) {
 		enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);

 		if (!nf_inet_addr_cmp(&ct->tuplehash[dir].tuple.dst.u3,
 				      &ct->tuplehash[!dir].tuple.src.u3)) {
 			err = ip6_route_me_harder(state->net, skb);
 			if (err < 0)
 				ret = NF_DROP_ERR(err);
 		}
 #ifdef CONFIG_XFRM
 		else if (!(IP6CB(skb)->flags & IP6SKB_XFRM_TRANSFORMED) &&
 			 ct->tuplehash[dir].tuple.dst.protonum != IPPROTO_ICMPV6 &&
 			 ct->tuplehash[dir].tuple.dst.u.all !=
 			 ct->tuplehash[!dir].tuple.src.u.all) {
 			err = nf_xfrm_me_harder(state->net, skb, AF_INET6);
 			if (err < 0)
 				ret = NF_DROP_ERR(err);
 		}
 #endif
 	}
 	return ret;
 }
 EXPORT_SYMBOL_GPL(nf_nat_ipv6_local_fn);

 static int __init nf_nat_l3proto_ipv6_init(void)
 {
 	int err;

 	err = nf_nat_l4proto_register(NFPROTO_IPV6, &nf_nat_l4proto_icmpv6);
 	if (err < 0)
 		goto err1;
 	err = nf_nat_l3proto_register(&nf_nat_l3proto_ipv6);
 	if (err < 0)
 		goto err2;
 	return err;

 err2:
 	nf_nat_l4proto_unregister(NFPROTO_IPV6, &nf_nat_l4proto_icmpv6);
 err1:
 	return err;
 }

 static void __exit nf_nat_l3proto_ipv6_exit(void)
 {
 	nf_nat_l3proto_unregister(&nf_nat_l3proto_ipv6);
 	nf_nat_l4proto_unregister(NFPROTO_IPV6, &nf_nat_l4proto_icmpv6);
 }

 MODULE_LICENSE("GPL");
 MODULE_ALIAS("nf-nat-" __stringify(AF_INET6));

 module_init(nf_nat_l3proto_ipv6_init);
 module_exit(nf_nat_l3proto_ipv6_exit);
	/*
	* Copyright (c) 2011 Patrick McHardy <kaber@trash.net>
	*
	* 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.
	*
	* Development of IPv6 NAT funded by Astaro.
	*/
	#include <linux/types.h>
	#include <linux/module.h>
	#include <linux/skbuff.h>
	#include <linux/ipv6.h>
	#include <linux/netfilter.h>
	#include <linux/netfilter_ipv6.h>
	#include <net/secure_seq.h>
	#include <net/checksum.h>
	#include <net/ip6_checksum.h>
	#include <net/ip6_route.h>
	#include <net/ipv6.h>

	#include <net/netfilter/nf_conntrack_core.h>
	#include <net/netfilter/nf_conntrack.h>
	#include <net/netfilter/nf_nat_core.h>
	#include <net/netfilter/nf_nat_l3proto.h>
	#include <net/netfilter/nf_nat_l4proto.h>

	static const struct nf_nat_l3proto nf_nat_l3proto_ipv6;

	#ifdef CONFIG_XFRM
	static void nf_nat_ipv6_decode_session(struct sk_buff *skb,
	const struct nf_conn *ct,
	enum ip_conntrack_dir dir,
	unsigned long statusbit,
	struct flowi *fl)
	{
	const struct nf_conntrack_tuple *t = &ct->tuplehash[dir].tuple;
	struct flowi6 *fl6 = &fl->u.ip6;

	if (ct->status & statusbit) {
	fl6->daddr = t->dst.u3.in6;
	if (t->dst.protonum == IPPROTO_TCP \|\|
	t->dst.protonum == IPPROTO_UDP \|\|
	t->dst.protonum == IPPROTO_UDPLITE \|\|
	t->dst.protonum == IPPROTO_DCCP \|\|
	t->dst.protonum == IPPROTO_SCTP)
	fl6->fl6_dport = t->dst.u.all;
	}

	statusbit ^= IPS_NAT_MASK;

	if (ct->status & statusbit) {
	fl6->saddr = t->src.u3.in6;
	if (t->dst.protonum == IPPROTO_TCP \|\|
	t->dst.protonum == IPPROTO_UDP \|\|
	t->dst.protonum == IPPROTO_UDPLITE \|\|
	t->dst.protonum == IPPROTO_DCCP \|\|
	t->dst.protonum == IPPROTO_SCTP)
	fl6->fl6_sport = t->src.u.all;
	}
	}
	#endif

	static bool nf_nat_ipv6_in_range(const struct nf_conntrack_tuple *t,
	const struct nf_nat_range *range)
	{
	return ipv6_addr_cmp(&t->src.u3.in6, &range->min_addr.in6) >= 0 &&
	ipv6_addr_cmp(&t->src.u3.in6, &range->max_addr.in6) <= 0;
	}

	static u32 nf_nat_ipv6_secure_port(const struct nf_conntrack_tuple *t,
	__be16 dport)
	{
	return secure_ipv6_port_ephemeral(t->src.u3.ip6, t->dst.u3.ip6, dport);
	}

	static bool nf_nat_ipv6_manip_pkt(struct sk_buff *skb,
	unsigned int iphdroff,
	const struct nf_nat_l4proto *l4proto,
	const struct nf_conntrack_tuple *target,
	enum nf_nat_manip_type maniptype)
	{
	struct ipv6hdr *ipv6h;
	__be16 frag_off;
	int hdroff;
	u8 nexthdr;

	if (!skb_make_writable(skb, iphdroff + sizeof(*ipv6h)))
	return false;

	ipv6h = (void *)skb->data + iphdroff;
	nexthdr = ipv6h->nexthdr;
	hdroff = ipv6_skip_exthdr(skb, iphdroff + sizeof(*ipv6h),
	&nexthdr, &frag_off);
	if (hdroff < 0)
	goto manip_addr;

	if ((frag_off & htons(~0x7)) == 0 &&
	!l4proto->manip_pkt(skb, &nf_nat_l3proto_ipv6, iphdroff, hdroff,
	target, maniptype))
	return false;

	/* must reload, offset might have changed */
	ipv6h = (void *)skb->data + iphdroff;

	manip_addr:
	if (maniptype == NF_NAT_MANIP_SRC)
	ipv6h->saddr = target->src.u3.in6;
	else
	ipv6h->daddr = target->dst.u3.in6;

	return true;
	}

	static void nf_nat_ipv6_csum_update(struct sk_buff *skb,
	unsigned int iphdroff, __sum16 *check,
	const struct nf_conntrack_tuple *t,
	enum nf_nat_manip_type maniptype)
	{
	const struct ipv6hdr ipv6h = (struct ipv6hdr )(skb->data + iphdroff);
	const struct in6_addr oldip, newip;

	if (maniptype == NF_NAT_MANIP_SRC) {
	oldip = &ipv6h->saddr;
	newip = &t->src.u3.in6;
	} else {
	oldip = &ipv6h->daddr;
	newip = &t->dst.u3.in6;
	}
	inet_proto_csum_replace16(check, skb, oldip->s6_addr32,
	newip->s6_addr32, true);
	}

	static void nf_nat_ipv6_csum_recalc(struct sk_buff *skb,
	u8 proto, void data, __sum16 check,
	int datalen, int oldlen)
	{
	if (skb->ip_summed != CHECKSUM_PARTIAL) {
	const struct ipv6hdr *ipv6h = ipv6_hdr(skb);

	skb->ip_summed = CHECKSUM_PARTIAL;
	skb->csum_start = skb_headroom(skb) + skb_network_offset(skb) +
	(data - (void *)skb->data);
	skb->csum_offset = (void *)check - data;
	*check = ~csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr,
	datalen, proto, 0);
	} else
	inet_proto_csum_replace2(check, skb,
	htons(oldlen), htons(datalen), true);
	}

	#if IS_ENABLED(CONFIG_NF_CT_NETLINK)
	static int nf_nat_ipv6_nlattr_to_range(struct nlattr *tb[],
	struct nf_nat_range *range)
	{
	if (tb[CTA_NAT_V6_MINIP]) {
	nla_memcpy(&range->min_addr.ip6, tb[CTA_NAT_V6_MINIP],
	sizeof(struct in6_addr));
	range->flags \|= NF_NAT_RANGE_MAP_IPS;
	}

	if (tb[CTA_NAT_V6_MAXIP])
	nla_memcpy(&range->max_addr.ip6, tb[CTA_NAT_V6_MAXIP],
	sizeof(struct in6_addr));
	else
	range->max_addr = range->min_addr;

	return 0;
	}
	#endif

	static const struct nf_nat_l3proto nf_nat_l3proto_ipv6 = {
	.l3proto = NFPROTO_IPV6,
	.secure_port = nf_nat_ipv6_secure_port,
	.in_range = nf_nat_ipv6_in_range,
	.manip_pkt = nf_nat_ipv6_manip_pkt,
	.csum_update = nf_nat_ipv6_csum_update,
	.csum_recalc = nf_nat_ipv6_csum_recalc,
	#if IS_ENABLED(CONFIG_NF_CT_NETLINK)
	.nlattr_to_range = nf_nat_ipv6_nlattr_to_range,
	#endif
	#ifdef CONFIG_XFRM
	.decode_session = nf_nat_ipv6_decode_session,
	#endif
	};

	int nf_nat_icmpv6_reply_translation(struct sk_buff *skb,
	struct nf_conn *ct,
	enum ip_conntrack_info ctinfo,
	unsigned int hooknum,
	unsigned int hdrlen)
	{
	struct {
	struct icmp6hdr icmp6;
	struct ipv6hdr ip6;
	} *inside;
	enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
	enum nf_nat_manip_type manip = HOOK2MANIP(hooknum);
	const struct nf_nat_l4proto *l4proto;
	struct nf_conntrack_tuple target;
	unsigned long statusbit;

	WARN_ON(ctinfo != IP_CT_RELATED && ctinfo != IP_CT_RELATED_REPLY);

	if (!skb_make_writable(skb, hdrlen + sizeof(*inside)))
	return 0;
	if (nf_ip6_checksum(skb, hooknum, hdrlen, IPPROTO_ICMPV6))
	return 0;

	inside = (void *)skb->data + hdrlen;
	if (inside->icmp6.icmp6_type == NDISC_REDIRECT) {
	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 direction */
	if (dir == IP_CT_DIR_REPLY)
	statusbit ^= IPS_NAT_MASK;

	if (!(ct->status & statusbit))
	return 1;

	l4proto = __nf_nat_l4proto_find(NFPROTO_IPV6, inside->ip6.nexthdr);
	if (!nf_nat_ipv6_manip_pkt(skb, hdrlen + sizeof(inside->icmp6),
	l4proto, &ct->tuplehash[!dir].tuple, !manip))
	return 0;

	if (skb->ip_summed != CHECKSUM_PARTIAL) {
	struct ipv6hdr *ipv6h = ipv6_hdr(skb);
	inside = (void *)skb->data + hdrlen;
	inside->icmp6.icmp6_cksum = 0;
	inside->icmp6.icmp6_cksum =
	csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr,
	skb->len - hdrlen, IPPROTO_ICMPV6,
	skb_checksum(skb, hdrlen,
	skb->len - hdrlen, 0));
	}

	nf_ct_invert_tuplepr(&target, &ct->tuplehash[!dir].tuple);
	l4proto = __nf_nat_l4proto_find(NFPROTO_IPV6, IPPROTO_ICMPV6);
	if (!nf_nat_ipv6_manip_pkt(skb, 0, l4proto, &target, manip))
	return 0;

	return 1;
	}
	EXPORT_SYMBOL_GPL(nf_nat_icmpv6_reply_translation);

	unsigned int
	nf_nat_ipv6_fn(void priv, struct sk_buff skb,
	const struct nf_hook_state *state,
	unsigned int (do_chain)(void priv,
	struct sk_buff *skb,
	const struct nf_hook_state *state,
	struct nf_conn *ct))
	{
	struct nf_conn *ct;
	enum ip_conntrack_info ctinfo;
	struct nf_conn_nat *nat;
	enum nf_nat_manip_type maniptype = HOOK2MANIP(state->hook);
	__be16 frag_off;
	int hdrlen;
	u8 nexthdr;

	ct = nf_ct_get(skb, &ctinfo);
	/* Can't track? It's not due to stress, or conntrack would
	* have dropped it. Hence it's the user's responsibilty to
	* packet filter it out, or implement conntrack/NAT for that
	* protocol. 8) --RR
	*/
	if (!ct)
	return NF_ACCEPT;

	nat = nfct_nat(ct);

	switch (ctinfo) {
	case IP_CT_RELATED:
	case IP_CT_RELATED_REPLY:
	nexthdr = ipv6_hdr(skb)->nexthdr;
	hdrlen = ipv6_skip_exthdr(skb, sizeof(struct ipv6hdr),
	&nexthdr, &frag_off);

	if (hdrlen >= 0 && nexthdr == IPPROTO_ICMPV6) {
	if (!nf_nat_icmpv6_reply_translation(skb, ct, ctinfo,
	state->hook,
	hdrlen))
	return NF_DROP;
	else
	return NF_ACCEPT;
	}
	/* Fall thru... (Only ICMPs can be IP_CT_IS_REPLY) */
	case IP_CT_NEW:
	/* Seen it before? This can happen for loopback, retrans,
	* or local packets.
	*/
	if (!nf_nat_initialized(ct, maniptype)) {
	unsigned int ret;

	ret = do_chain(priv, skb, state, ct);
	if (ret != NF_ACCEPT)
	return ret;

	if (nf_nat_initialized(ct, HOOK2MANIP(state->hook)))
	break;

	ret = nf_nat_alloc_null_binding(ct, state->hook);
	if (ret != NF_ACCEPT)
	return ret;
	} else {
	pr_debug("Already setup manip %s for ct %p\n",
	maniptype == NF_NAT_MANIP_SRC ? "SRC" : "DST",
	ct);
	if (nf_nat_oif_changed(state->hook, ctinfo, nat, state->out))
	goto oif_changed;
	}
	break;

	default:
	/* ESTABLISHED */
	WARN_ON(ctinfo != IP_CT_ESTABLISHED &&
	ctinfo != IP_CT_ESTABLISHED_REPLY);
	if (nf_nat_oif_changed(state->hook, ctinfo, nat, state->out))
	goto oif_changed;
	}

	return nf_nat_packet(ct, ctinfo, state->hook, skb);

	oif_changed:
	nf_ct_kill_acct(ct, ctinfo, skb);
	return NF_DROP;
	}
	EXPORT_SYMBOL_GPL(nf_nat_ipv6_fn);

	unsigned int
	nf_nat_ipv6_in(void priv, struct sk_buff skb,
	const struct nf_hook_state *state,
	unsigned int (do_chain)(void priv,
	struct sk_buff *skb,
	const struct nf_hook_state *state,
	struct nf_conn *ct))
	{
	unsigned int ret;
	struct in6_addr daddr = ipv6_hdr(skb)->daddr;

	ret = nf_nat_ipv6_fn(priv, skb, state, do_chain);
	if (ret != NF_DROP && ret != NF_STOLEN &&
	ipv6_addr_cmp(&daddr, &ipv6_hdr(skb)->daddr))
	skb_dst_drop(skb);

	return ret;
	}
	EXPORT_SYMBOL_GPL(nf_nat_ipv6_in);

	unsigned int
	nf_nat_ipv6_out(void priv, struct sk_buff skb,
	const struct nf_hook_state *state,
	unsigned int (do_chain)(void priv,
	struct sk_buff *skb,
	const struct nf_hook_state *state,
	struct nf_conn *ct))
	{
	#ifdef CONFIG_XFRM
	const struct nf_conn *ct;
	enum ip_conntrack_info ctinfo;
	int err;
	#endif
	unsigned int ret;

	/* root is playing with raw sockets. */
	if (skb->len < sizeof(struct ipv6hdr))
	return NF_ACCEPT;

	ret = nf_nat_ipv6_fn(priv, skb, state, do_chain);
	#ifdef CONFIG_XFRM
	if (ret != NF_DROP && ret != NF_STOLEN &&
	!(IP6CB(skb)->flags & IP6SKB_XFRM_TRANSFORMED) &&
	(ct = nf_ct_get(skb, &ctinfo)) != NULL) {
	enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);

	if (!nf_inet_addr_cmp(&ct->tuplehash[dir].tuple.src.u3,
	&ct->tuplehash[!dir].tuple.dst.u3) \|\|
	(ct->tuplehash[dir].tuple.dst.protonum != IPPROTO_ICMPV6 &&
	ct->tuplehash[dir].tuple.src.u.all !=
	ct->tuplehash[!dir].tuple.dst.u.all)) {
	err = nf_xfrm_me_harder(state->net, skb, AF_INET6);
	if (err < 0)
	ret = NF_DROP_ERR(err);
	}
	}
	#endif
	return ret;
	}
	EXPORT_SYMBOL_GPL(nf_nat_ipv6_out);

	unsigned int
	nf_nat_ipv6_local_fn(void priv, struct sk_buff skb,
	const struct nf_hook_state *state,
	unsigned int (do_chain)(void priv,
	struct sk_buff *skb,
	const struct nf_hook_state *state,
	struct nf_conn *ct))
	{
	const struct nf_conn *ct;
	enum ip_conntrack_info ctinfo;
	unsigned int ret;
	int err;

	/* root is playing with raw sockets. */
	if (skb->len < sizeof(struct ipv6hdr))
	return NF_ACCEPT;

	ret = nf_nat_ipv6_fn(priv, skb, state, do_chain);
	if (ret != NF_DROP && ret != NF_STOLEN &&
	(ct = nf_ct_get(skb, &ctinfo)) != NULL) {
	enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);

	if (!nf_inet_addr_cmp(&ct->tuplehash[dir].tuple.dst.u3,
	&ct->tuplehash[!dir].tuple.src.u3)) {
	err = ip6_route_me_harder(state->net, skb);
	if (err < 0)
	ret = NF_DROP_ERR(err);
	}
	#ifdef CONFIG_XFRM
	else if (!(IP6CB(skb)->flags & IP6SKB_XFRM_TRANSFORMED) &&
	ct->tuplehash[dir].tuple.dst.protonum != IPPROTO_ICMPV6 &&
	ct->tuplehash[dir].tuple.dst.u.all !=
	ct->tuplehash[!dir].tuple.src.u.all) {
	err = nf_xfrm_me_harder(state->net, skb, AF_INET6);
	if (err < 0)
	ret = NF_DROP_ERR(err);
	}
	#endif
	}
	return ret;
	}
	EXPORT_SYMBOL_GPL(nf_nat_ipv6_local_fn);

	static int __init nf_nat_l3proto_ipv6_init(void)
	{
	int err;

	err = nf_nat_l4proto_register(NFPROTO_IPV6, &nf_nat_l4proto_icmpv6);
	if (err < 0)
	goto err1;
	err = nf_nat_l3proto_register(&nf_nat_l3proto_ipv6);
	if (err < 0)
	goto err2;
	return err;

	err2:
	nf_nat_l4proto_unregister(NFPROTO_IPV6, &nf_nat_l4proto_icmpv6);
	err1:
	return err;
	}

	static void __exit nf_nat_l3proto_ipv6_exit(void)
	{
	nf_nat_l3proto_unregister(&nf_nat_l3proto_ipv6);
	nf_nat_l4proto_unregister(NFPROTO_IPV6, &nf_nat_l4proto_icmpv6);
	}

	MODULE_LICENSE("GPL");
	MODULE_ALIAS("nf-nat-" __stringify(AF_INET6));

	module_init(nf_nat_l3proto_ipv6_init);
	module_exit(nf_nat_l3proto_ipv6_exit);