// SPDX-License-Identifier: GPL-2.0-or-later

  /*

   *	IPv6 tunneling device

   *	Linux INET6 implementation
   *
   *	Authors:

   *	Ville Nuorvala		<vnuorval@tcs.hut.fi>

   *	Yasuyuki Kozakai	<kozakai@linux-ipv6.org>

   *

   *      Based on:

   *      linux/net/ipv6/sit.c and linux/net/ipv4/ipip.c

   *
   *      RFC 2473

   */

  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

  #include <linux/module.h>

  #include <linux/capability.h>

  #include <linux/errno.h>
  #include <linux/types.h>
  #include <linux/sockios.h>

  #include <linux/icmp.h>

  #include <linux/if.h>
  #include <linux/in.h>
  #include <linux/ip.h>

  #include <linux/net.h>
  #include <linux/in6.h>
  #include <linux/netdevice.h>
  #include <linux/if_arp.h>
  #include <linux/icmpv6.h>
  #include <linux/init.h>
  #include <linux/route.h>
  #include <linux/rtnetlink.h>
  #include <linux/netfilter_ipv6.h>

  #include <linux/slab.h>

  #include <linux/hash.h>

  #include <linux/etherdevice.h>

  #include <linux/uaccess.h>

  #include <linux/atomic.h>

  #include <net/icmp.h>

  #include <net/ip.h>

  #include <net/ip_tunnels.h>

  #include <net/ipv6.h>

  #include <net/ip6_route.h>
  #include <net/addrconf.h>
  #include <net/ip6_tunnel.h>
  #include <net/xfrm.h>
  #include <net/dsfield.h>
  #include <net/inet_ecn.h>

  #include <net/net_namespace.h>
  #include <net/netns/generic.h>

  #include <net/dst_metadata.h>

  
  MODULE_AUTHOR("Ville Nuorvala");

  MODULE_DESCRIPTION("IPv6 tunneling device");

  MODULE_LICENSE("GPL");

  MODULE_ALIAS_RTNL_LINK("ip6tnl");

  MODULE_ALIAS_NETDEV("ip6tnl0");

  #define IP6_TUNNEL_HASH_SIZE_SHIFT  5
  #define IP6_TUNNEL_HASH_SIZE (1 << IP6_TUNNEL_HASH_SIZE_SHIFT)

  static bool log_ecn_error = true;
  module_param(log_ecn_error, bool, 0644);
  MODULE_PARM_DESC(log_ecn_error, "Log packets received with corrupted ECN");

  static u32 HASH(const struct in6_addr *addr1, const struct in6_addr *addr2)
  {
  	u32 hash = ipv6_addr_hash(addr1) ^ ipv6_addr_hash(addr2);

  	return hash_32(hash, IP6_TUNNEL_HASH_SIZE_SHIFT);

  }

  static int ip6_tnl_dev_init(struct net_device *dev);

  static void ip6_tnl_dev_setup(struct net_device *dev);

  static struct rtnl_link_ops ip6_link_ops __read_mostly;

  static unsigned int ip6_tnl_net_id __read_mostly;

  struct ip6_tnl_net {

  	/* the IPv6 tunnel fallback device */
  	struct net_device *fb_tnl_dev;

  	/* lists for storing tunnels in use */

  	struct ip6_tnl __rcu *tnls_r_l[IP6_TUNNEL_HASH_SIZE];

  	struct ip6_tnl __rcu *tnls_wc[1];
  	struct ip6_tnl __rcu **tnls[2];

  	struct ip6_tnl __rcu *collect_md_tun;

  };

  static inline int ip6_tnl_mpls_supported(void)
  {
  	return IS_ENABLED(CONFIG_MPLS);
  }

  static struct net_device_stats *ip6_get_stats(struct net_device *dev)
  {

  	struct pcpu_sw_netstats tmp, sum = { 0 };

  	int i;
  
  	for_each_possible_cpu(i) {

  		unsigned int start;

  		const struct pcpu_sw_netstats *tstats =
  						   per_cpu_ptr(dev->tstats, i);

  		do {

  			start = u64_stats_fetch_begin_irq(&tstats->syncp);

  			tmp.rx_packets = tstats->rx_packets;
  			tmp.rx_bytes = tstats->rx_bytes;
  			tmp.tx_packets = tstats->tx_packets;
  			tmp.tx_bytes =  tstats->tx_bytes;

  		} while (u64_stats_fetch_retry_irq(&tstats->syncp, start));

  
  		sum.rx_packets += tmp.rx_packets;
  		sum.rx_bytes   += tmp.rx_bytes;
  		sum.tx_packets += tmp.tx_packets;
  		sum.tx_bytes   += tmp.tx_bytes;

  	}
  	dev->stats.rx_packets = sum.rx_packets;
  	dev->stats.rx_bytes   = sum.rx_bytes;
  	dev->stats.tx_packets = sum.tx_packets;
  	dev->stats.tx_bytes   = sum.tx_bytes;
  	return &dev->stats;
  }

  #define for_each_ip6_tunnel_rcu(start) \
  	for (t = rcu_dereference(start); t; t = rcu_dereference(t->next))

  /**

   * ip6_tnl_lookup - fetch tunnel matching the end-point addresses

   *   @net: network namespace

   *   @link: ifindex of underlying interface

   *   @remote: the address of the tunnel exit-point
   *   @local: the address of the tunnel entry-point

   *

   * Return:

   *   tunnel matching given end-points if found,

   *   else fallback tunnel if its device is up,

   *   else %NULL
   **/
  
  static struct ip6_tnl *

  ip6_tnl_lookup(struct net *net, int link,
  	       const struct in6_addr *remote, const struct in6_addr *local)

  {

  	unsigned int hash = HASH(remote, local);

  	struct ip6_tnl *t, *cand = NULL;

  	struct ip6_tnl_net *ip6n = net_generic(net, ip6_tnl_net_id);

  	struct in6_addr any;

  	for_each_ip6_tunnel_rcu(ip6n->tnls_r_l[hash]) {

  		if (!ipv6_addr_equal(local, &t->parms.laddr) ||
  		    !ipv6_addr_equal(remote, &t->parms.raddr) ||
  		    !(t->dev->flags & IFF_UP))
  			continue;
  
  		if (link == t->parms.link)

  			return t;

  		else
  			cand = t;

  	}

  
  	memset(&any, 0, sizeof(any));
  	hash = HASH(&any, local);
  	for_each_ip6_tunnel_rcu(ip6n->tnls_r_l[hash]) {

  		if (!ipv6_addr_equal(local, &t->parms.laddr) ||
  		    !ipv6_addr_any(&t->parms.raddr) ||
  		    !(t->dev->flags & IFF_UP))
  			continue;
  
  		if (link == t->parms.link)

  			return t;

  		else if (!cand)
  			cand = t;

  	}
  
  	hash = HASH(remote, &any);
  	for_each_ip6_tunnel_rcu(ip6n->tnls_r_l[hash]) {

  		if (!ipv6_addr_equal(remote, &t->parms.raddr) ||
  		    !ipv6_addr_any(&t->parms.laddr) ||
  		    !(t->dev->flags & IFF_UP))
  			continue;
  
  		if (link == t->parms.link)

  			return t;

  		else if (!cand)
  			cand = t;

  	}

  	if (cand)
  		return cand;

  	t = rcu_dereference(ip6n->collect_md_tun);

  	if (t && t->dev->flags & IFF_UP)

  		return t;

  	t = rcu_dereference(ip6n->tnls_wc[0]);
  	if (t && (t->dev->flags & IFF_UP))

  		return t;
  
  	return NULL;
  }
  
  /**

   * ip6_tnl_bucket - get head of list matching given tunnel parameters

   *   @p: parameters containing tunnel end-points

   *
   * Description:

   *   ip6_tnl_bucket() returns the head of the list matching the

   *   &struct in6_addr entries laddr and raddr in @p.
   *

   * Return: head of IPv6 tunnel list

   **/

  static struct ip6_tnl __rcu **

  ip6_tnl_bucket(struct ip6_tnl_net *ip6n, const struct __ip6_tnl_parm *p)

  {

  	const struct in6_addr *remote = &p->raddr;
  	const struct in6_addr *local = &p->laddr;

  	unsigned int h = 0;

  	int prio = 0;
  
  	if (!ipv6_addr_any(remote) || !ipv6_addr_any(local)) {
  		prio = 1;

  		h = HASH(remote, local);

  	}

  	return &ip6n->tnls[prio][h];

  }
  
  /**

   * ip6_tnl_link - add tunnel to hash table

   *   @t: tunnel to be added
   **/
  
  static void

  ip6_tnl_link(struct ip6_tnl_net *ip6n, struct ip6_tnl *t)

  {

  	struct ip6_tnl __rcu **tp = ip6_tnl_bucket(ip6n, &t->parms);

  	if (t->parms.collect_md)
  		rcu_assign_pointer(ip6n->collect_md_tun, t);

  	rcu_assign_pointer(t->next , rtnl_dereference(*tp));
  	rcu_assign_pointer(*tp, t);

  }
  
  /**

   * ip6_tnl_unlink - remove tunnel from hash table

   *   @t: tunnel to be removed
   **/
  
  static void

  ip6_tnl_unlink(struct ip6_tnl_net *ip6n, struct ip6_tnl *t)

  {

  	struct ip6_tnl __rcu **tp;
  	struct ip6_tnl *iter;

  	if (t->parms.collect_md)
  		rcu_assign_pointer(ip6n->collect_md_tun, NULL);

  	for (tp = ip6_tnl_bucket(ip6n, &t->parms);
  	     (iter = rtnl_dereference(*tp)) != NULL;
  	     tp = &iter->next) {
  		if (t == iter) {

  			rcu_assign_pointer(*tp, t->next);

  			break;
  		}
  	}
  }

  static void ip6_dev_free(struct net_device *dev)
  {

  	struct ip6_tnl *t = netdev_priv(dev);

  	gro_cells_destroy(&t->gro_cells);

  	dst_cache_destroy(&t->dst_cache);

  	free_percpu(dev->tstats);

  }

  static int ip6_tnl_create2(struct net_device *dev)
  {
  	struct ip6_tnl *t = netdev_priv(dev);
  	struct net *net = dev_net(dev);
  	struct ip6_tnl_net *ip6n = net_generic(net, ip6_tnl_net_id);
  	int err;
  
  	t = netdev_priv(dev);

  	dev->rtnl_link_ops = &ip6_link_ops;

  	err = register_netdevice(dev);
  	if (err < 0)
  		goto out;
  
  	strcpy(t->parms.name, dev->name);

  
  	dev_hold(dev);
  	ip6_tnl_link(ip6n, t);
  	return 0;
  
  out:
  	return err;
  }

  /**

   * ip6_tnl_create - create a new tunnel

   *   @net: network namespace

   *   @p: tunnel parameters

   *
   * Description:
   *   Create tunnel matching given parameters.

   *
   * Return:

   *   created tunnel or error pointer

   **/

  static struct ip6_tnl *ip6_tnl_create(struct net *net, struct __ip6_tnl_parm *p)

  {
  	struct net_device *dev;
  	struct ip6_tnl *t;
  	char name[IFNAMSIZ];

  	int err = -E2BIG;

  	if (p->name[0]) {
  		if (!dev_valid_name(p->name))
  			goto failed;

  		strlcpy(name, p->name, IFNAMSIZ);

  	} else {

  		sprintf(name, "ip6tnl%%d");

  	}
  	err = -ENOMEM;

  	dev = alloc_netdev(sizeof(*t), name, NET_NAME_UNKNOWN,
  			   ip6_tnl_dev_setup);

  	if (!dev)

  		goto failed;

  	dev_net_set(dev, net);

  	t = netdev_priv(dev);

  	t->parms = *p;

  	t->net = dev_net(dev);

  	err = ip6_tnl_create2(dev);

  	if (err < 0)
  		goto failed_free;

  	return t;

  
  failed_free:

  	free_netdev(dev);

  failed:

  	return ERR_PTR(err);

  }
  
  /**

   * ip6_tnl_locate - find or create tunnel matching given parameters

   *   @net: network namespace

   *   @p: tunnel parameters

   *   @create: != 0 if allowed to create new tunnel if no match found
   *
   * Description:

   *   ip6_tnl_locate() first tries to locate an existing tunnel

   *   based on @parms. If this is unsuccessful, but @create is set a new
   *   tunnel device is created and registered for use.
   *
   * Return:

   *   matching tunnel or error pointer

   **/

  static struct ip6_tnl *ip6_tnl_locate(struct net *net,

  		struct __ip6_tnl_parm *p, int create)

  {

  	const struct in6_addr *remote = &p->raddr;
  	const struct in6_addr *local = &p->laddr;

  	struct ip6_tnl __rcu **tp;

  	struct ip6_tnl *t;

  	struct ip6_tnl_net *ip6n = net_generic(net, ip6_tnl_net_id);

  	for (tp = ip6_tnl_bucket(ip6n, p);
  	     (t = rtnl_dereference(*tp)) != NULL;
  	     tp = &t->next) {

  		if (ipv6_addr_equal(local, &t->parms.laddr) &&

  		    ipv6_addr_equal(remote, &t->parms.raddr) &&
  		    p->link == t->parms.link) {

  			if (create)

  				return ERR_PTR(-EEXIST);

  			return t;

  		}

  	}
  	if (!create)

  		return ERR_PTR(-ENODEV);

  	return ip6_tnl_create(net, p);

  }
  
  /**

   * ip6_tnl_dev_uninit - tunnel device uninitializer

   *   @dev: the device to be destroyed

   *

   * Description:

   *   ip6_tnl_dev_uninit() removes tunnel from its list

   **/
  
  static void

  ip6_tnl_dev_uninit(struct net_device *dev)

  {

  	struct ip6_tnl *t = netdev_priv(dev);

  	struct net *net = t->net;

  	struct ip6_tnl_net *ip6n = net_generic(net, ip6_tnl_net_id);

  	if (dev == ip6n->fb_tnl_dev)

  		RCU_INIT_POINTER(ip6n->tnls_wc[0], NULL);

  	else

  		ip6_tnl_unlink(ip6n, t);

  	dst_cache_reset(&t->dst_cache);

  	dev_put(dev);
  }
  
  /**
   * parse_tvl_tnl_enc_lim - handle encapsulation limit option
   *   @skb: received socket buffer
   *

   * Return:
   *   0 if none was found,

   *   else index to encapsulation limit
   **/

  __u16 ip6_tnl_parse_tlv_enc_lim(struct sk_buff *skb, __u8 *raw)

  {

  	const struct ipv6hdr *ipv6h = (const struct ipv6hdr *)raw;
  	unsigned int nhoff = raw - skb->data;
  	unsigned int off = nhoff + sizeof(*ipv6h);
  	u8 next, nexthdr = ipv6h->nexthdr;

  
  	while (ipv6_ext_hdr(nexthdr) && nexthdr != NEXTHDR_NONE) {

  		struct ipv6_opt_hdr *hdr;

  		u16 optlen;
  
  		if (!pskb_may_pull(skb, off + sizeof(*hdr)))

  			break;

  		hdr = (struct ipv6_opt_hdr *)(skb->data + off);

  		if (nexthdr == NEXTHDR_FRAGMENT) {
  			struct frag_hdr *frag_hdr = (struct frag_hdr *) hdr;
  			if (frag_hdr->frag_off)
  				break;
  			optlen = 8;
  		} else if (nexthdr == NEXTHDR_AUTH) {

  			optlen = ipv6_authlen(hdr);

  		} else {
  			optlen = ipv6_optlen(hdr);
  		}

  		/* cache hdr->nexthdr, since pskb_may_pull() might
  		 * invalidate hdr
  		 */
  		next = hdr->nexthdr;

  		if (nexthdr == NEXTHDR_DEST) {

  			u16 i = 2;
  
  			/* Remember : hdr is no longer valid at this point. */
  			if (!pskb_may_pull(skb, off + optlen))
  				break;

  			while (1) {
  				struct ipv6_tlv_tnl_enc_lim *tel;
  
  				/* No more room for encapsulation limit */

  				if (i + sizeof(*tel) > optlen)

  					break;

  				tel = (struct ipv6_tlv_tnl_enc_lim *)(skb->data + off + i);

  				/* return index of option if found and valid */
  				if (tel->type == IPV6_TLV_TNL_ENCAP_LIMIT &&
  				    tel->length == 1)

  					return i + off - nhoff;

  				/* else jump to next option */
  				if (tel->type)
  					i += tel->length + 2;
  				else
  					i++;
  			}
  		}

  		nexthdr = next;

  		off += optlen;
  	}
  	return 0;
  }

  EXPORT_SYMBOL(ip6_tnl_parse_tlv_enc_lim);

  
  /**

   * ip6_tnl_err - tunnel error handler

   *
   * Description:

   *   ip6_tnl_err() should handle errors in the tunnel according

   *   to the specifications in RFC 2473.
   **/

  static int

  ip6_tnl_err(struct sk_buff *skb, __u8 ipproto, struct inet6_skb_parm *opt,

  	    u8 *type, u8 *code, int *msg, __u32 *info, int offset)

  {

  	const struct ipv6hdr *ipv6h = (const struct ipv6hdr *)skb->data;
  	struct net *net = dev_net(skb->dev);

  	u8 rel_type = ICMPV6_DEST_UNREACH;
  	u8 rel_code = ICMPV6_ADDR_UNREACH;

  	__u32 rel_info = 0;

  	struct ip6_tnl *t;

  	int err = -ENOENT;

  	int rel_msg = 0;
  	u8 tproto;
  	__u16 len;

  	/* If the packet doesn't contain the original IPv6 header we are
  	   in trouble since we might need the source address for further

  	   processing of the error. */

  	rcu_read_lock();

  	t = ip6_tnl_lookup(dev_net(skb->dev), skb->dev->ifindex, &ipv6h->daddr, &ipv6h->saddr);

  	if (!t)

  		goto out;

  	tproto = READ_ONCE(t->parms.proto);

  	if (tproto != ipproto && tproto != 0)

  		goto out;

  	err = 0;

  	switch (*type) {

  	case ICMPV6_DEST_UNREACH:

  		net_dbg_ratelimited("%s: Path to destination invalid or inactive!
  ",
  				    t->parms.name);

  		rel_msg = 1;
  		break;
  	case ICMPV6_TIME_EXCEED:

  		if ((*code) == ICMPV6_EXC_HOPLIMIT) {

  			net_dbg_ratelimited("%s: Too small hop limit or routing loop in tunnel!
  ",
  					    t->parms.name);

  			rel_msg = 1;
  		}
  		break;

  	case ICMPV6_PARAMPROB: {
  		struct ipv6_tlv_tnl_enc_lim *tel;
  		__u32 teli;

  		teli = 0;

  		if ((*code) == ICMPV6_HDR_FIELD)

  			teli = ip6_tnl_parse_tlv_enc_lim(skb, skb->data);

  		if (teli && teli == *info - 2) {

  			tel = (struct ipv6_tlv_tnl_enc_lim *) &skb->data[teli];
  			if (tel->encap_limit == 0) {

  				net_dbg_ratelimited("%s: Too small encapsulation limit or routing loop in tunnel!
  ",
  						    t->parms.name);

  				rel_msg = 1;
  			}

  		} else {

  			net_dbg_ratelimited("%s: Recipient unable to parse tunneled packet!
  ",
  					    t->parms.name);

  		}
  		break;

  	}
  	case ICMPV6_PKT_TOOBIG: {
  		__u32 mtu;

  		ip6_update_pmtu(skb, net, htonl(*info), 0, 0,
  				sock_net_uid(net, NULL));

  		mtu = *info - offset;

  		if (mtu < IPV6_MIN_MTU)
  			mtu = IPV6_MIN_MTU;

  		len = sizeof(*ipv6h) + ntohs(ipv6h->payload_len);
  		if (len > mtu) {

  			rel_type = ICMPV6_PKT_TOOBIG;
  			rel_code = 0;
  			rel_info = mtu;
  			rel_msg = 1;
  		}
  		break;

  	}

  	case NDISC_REDIRECT:
  		ip6_redirect(skb, net, skb->dev->ifindex, 0,
  			     sock_net_uid(net, NULL));
  		break;

  	}

  
  	*type = rel_type;
  	*code = rel_code;
  	*info = rel_info;
  	*msg = rel_msg;
  
  out:

  	rcu_read_unlock();

  	return err;
  }
  
  static int

  ip4ip6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,

  	   u8 type, u8 code, int offset, __be32 info)

  {

  	__u32 rel_info = ntohl(info);

  	const struct iphdr *eiph;

  	struct sk_buff *skb2;
  	int err, rel_msg = 0;
  	u8 rel_type = type;
  	u8 rel_code = code;

  	struct rtable *rt;

  	struct flowi4 fl4;

  	err = ip6_tnl_err(skb, IPPROTO_IPIP, opt, &rel_type, &rel_code,
  			  &rel_msg, &rel_info, offset);

  	if (err < 0)
  		return err;
  
  	if (rel_msg == 0)
  		return 0;
  
  	switch (rel_type) {
  	case ICMPV6_DEST_UNREACH:
  		if (rel_code != ICMPV6_ADDR_UNREACH)
  			return 0;
  		rel_type = ICMP_DEST_UNREACH;
  		rel_code = ICMP_HOST_UNREACH;
  		break;
  	case ICMPV6_PKT_TOOBIG:
  		if (rel_code != 0)
  			return 0;
  		rel_type = ICMP_DEST_UNREACH;
  		rel_code = ICMP_FRAG_NEEDED;
  		break;
  	default:
  		return 0;
  	}
  
  	if (!pskb_may_pull(skb, offset + sizeof(struct iphdr)))
  		return 0;
  
  	skb2 = skb_clone(skb, GFP_ATOMIC);
  	if (!skb2)
  		return 0;

  	skb_dst_drop(skb2);

  	skb_pull(skb2, offset);

  	skb_reset_network_header(skb2);

  	eiph = ip_hdr(skb2);

  
  	/* Try to guess incoming interface */

  	rt = ip_route_output_ports(dev_net(skb->dev), &fl4, NULL, eiph->saddr,
  				   0, 0, 0, IPPROTO_IPIP, RT_TOS(eiph->tos), 0);

  	if (IS_ERR(rt))

  		goto out;

  	skb2->dev = rt->dst.dev;

  	ip_rt_put(rt);

  
  	/* route "incoming" packet */
  	if (rt->rt_flags & RTCF_LOCAL) {

  		rt = ip_route_output_ports(dev_net(skb->dev), &fl4, NULL,

  					   eiph->daddr, eiph->saddr, 0, 0,
  					   IPPROTO_IPIP, RT_TOS(eiph->tos), 0);

  		if (IS_ERR(rt) || rt->dst.dev->type != ARPHRD_TUNNEL6) {

  			if (!IS_ERR(rt))
  				ip_rt_put(rt);

  			goto out;
  		}

  		skb_dst_set(skb2, &rt->dst);

  	} else {

  		if (ip_route_input(skb2, eiph->daddr, eiph->saddr, eiph->tos,
  				   skb2->dev) ||

  		    skb_dst(skb2)->dev->type != ARPHRD_TUNNEL6)

  			goto out;
  	}
  
  	/* change mtu on this route */
  	if (rel_type == ICMP_DEST_UNREACH && rel_code == ICMP_FRAG_NEEDED) {

  		if (rel_info > dst_mtu(skb_dst(skb2)))

  			goto out;

  		skb_dst_update_pmtu_no_confirm(skb2, rel_info);

  	}

  	icmp_send(skb2, rel_type, rel_code, htonl(rel_info));

  
  out:
  	kfree_skb(skb2);
  	return 0;
  }
  
  static int

  ip6ip6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,

  	   u8 type, u8 code, int offset, __be32 info)

  {

  	__u32 rel_info = ntohl(info);
  	int err, rel_msg = 0;

  	u8 rel_type = type;
  	u8 rel_code = code;

  	err = ip6_tnl_err(skb, IPPROTO_IPV6, opt, &rel_type, &rel_code,
  			  &rel_msg, &rel_info, offset);

  	if (err < 0)
  		return err;
  
  	if (rel_msg && pskb_may_pull(skb, offset + sizeof(struct ipv6hdr))) {

  		struct rt6_info *rt;
  		struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC);

  		if (!skb2)

  			return 0;

  		skb_dst_drop(skb2);

  		skb_pull(skb2, offset);

  		skb_reset_network_header(skb2);

  
  		/* Try to guess incoming interface */

  		rt = rt6_lookup(dev_net(skb->dev), &ipv6_hdr(skb2)->saddr,

  				NULL, 0, skb2, 0);

  		if (rt && rt->dst.dev)
  			skb2->dev = rt->dst.dev;

  		icmpv6_send(skb2, rel_type, rel_code, rel_info);

  		ip6_rt_put(rt);

  
  		kfree_skb(skb2);
  	}

  
  	return 0;

  }

  static int
  mplsip6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
  	    u8 type, u8 code, int offset, __be32 info)
  {
  	__u32 rel_info = ntohl(info);
  	int err, rel_msg = 0;
  	u8 rel_type = type;
  	u8 rel_code = code;
  
  	err = ip6_tnl_err(skb, IPPROTO_MPLS, opt, &rel_type, &rel_code,
  			  &rel_msg, &rel_info, offset);
  	return err;
  }

  static int ip4ip6_dscp_ecn_decapsulate(const struct ip6_tnl *t,
  				       const struct ipv6hdr *ipv6h,
  				       struct sk_buff *skb)

  {
  	__u8 dsfield = ipv6_get_dsfield(ipv6h) & ~INET_ECN_MASK;
  
  	if (t->parms.flags & IP6_TNL_F_RCV_DSCP_COPY)

  		ipv4_change_dsfield(ip_hdr(skb), INET_ECN_MASK, dsfield);

  	return IP6_ECN_decapsulate(ipv6h, skb);

  }

  static int ip6ip6_dscp_ecn_decapsulate(const struct ip6_tnl *t,
  				       const struct ipv6hdr *ipv6h,
  				       struct sk_buff *skb)

  {

  	if (t->parms.flags & IP6_TNL_F_RCV_DSCP_COPY)

  		ipv6_copy_dscp(ipv6_get_dsfield(ipv6h), ipv6_hdr(skb));

  	return IP6_ECN_decapsulate(ipv6h, skb);

  }

  static inline int mplsip6_dscp_ecn_decapsulate(const struct ip6_tnl *t,
  					       const struct ipv6hdr *ipv6h,
  					       struct sk_buff *skb)
  {
  	/* ECN is not supported in AF_MPLS */
  	return 0;
  }

  __u32 ip6_tnl_get_cap(struct ip6_tnl *t,

  			     const struct in6_addr *laddr,
  			     const struct in6_addr *raddr)
  {

  	struct __ip6_tnl_parm *p = &t->parms;

  	int ltype = ipv6_addr_type(laddr);
  	int rtype = ipv6_addr_type(raddr);
  	__u32 flags = 0;
  
  	if (ltype == IPV6_ADDR_ANY || rtype == IPV6_ADDR_ANY) {
  		flags = IP6_TNL_F_CAP_PER_PACKET;
  	} else if (ltype & (IPV6_ADDR_UNICAST|IPV6_ADDR_MULTICAST) &&
  		   rtype & (IPV6_ADDR_UNICAST|IPV6_ADDR_MULTICAST) &&
  		   !((ltype|rtype) & IPV6_ADDR_LOOPBACK) &&
  		   (!((ltype|rtype) & IPV6_ADDR_LINKLOCAL) || p->link)) {
  		if (ltype&IPV6_ADDR_UNICAST)
  			flags |= IP6_TNL_F_CAP_XMIT;
  		if (rtype&IPV6_ADDR_UNICAST)
  			flags |= IP6_TNL_F_CAP_RCV;
  	}
  	return flags;
  }

  EXPORT_SYMBOL(ip6_tnl_get_cap);

  /* called with rcu_read_lock() */

  int ip6_tnl_rcv_ctl(struct ip6_tnl *t,

  				  const struct in6_addr *laddr,
  				  const struct in6_addr *raddr)

  {

  	struct __ip6_tnl_parm *p = &t->parms;

  	int ret = 0;

  	struct net *net = t->net;

  	if ((p->flags & IP6_TNL_F_CAP_RCV) ||
  	    ((p->flags & IP6_TNL_F_CAP_PER_PACKET) &&
  	     (ip6_tnl_get_cap(t, laddr, raddr) & IP6_TNL_F_CAP_RCV))) {

  		struct net_device *ldev = NULL;

  
  		if (p->link)

  			ldev = dev_get_by_index_rcu(net, p->link);

  		if ((ipv6_addr_is_multicast(laddr) ||

  		     likely(ipv6_chk_addr_and_flags(net, laddr, ldev, false,
  						    0, IFA_F_TENTATIVE))) &&

  		    ((p->flags & IP6_TNL_F_ALLOW_LOCAL_REMOTE) ||

  		     likely(!ipv6_chk_addr_and_flags(net, raddr, ldev, true,
  						     0, IFA_F_TENTATIVE))))

  			ret = 1;

  	}
  	return ret;
  }

  EXPORT_SYMBOL_GPL(ip6_tnl_rcv_ctl);

  static int __ip6_tnl_rcv(struct ip6_tnl *tunnel, struct sk_buff *skb,
  			 const struct tnl_ptk_info *tpi,
  			 struct metadata_dst *tun_dst,
  			 int (*dscp_ecn_decapsulate)(const struct ip6_tnl *t,
  						const struct ipv6hdr *ipv6h,
  						struct sk_buff *skb),
  			 bool log_ecn_err)

  {

  	struct pcpu_sw_netstats *tstats;

  	const struct ipv6hdr *ipv6h = ipv6_hdr(skb);

  	int err;

  	if ((!(tpi->flags & TUNNEL_CSUM) &&
  	     (tunnel->parms.i_flags & TUNNEL_CSUM)) ||
  	    ((tpi->flags & TUNNEL_CSUM) &&
  	     !(tunnel->parms.i_flags & TUNNEL_CSUM))) {
  		tunnel->dev->stats.rx_crc_errors++;
  		tunnel->dev->stats.rx_errors++;
  		goto drop;
  	}

  	if (tunnel->parms.i_flags & TUNNEL_SEQ) {
  		if (!(tpi->flags & TUNNEL_SEQ) ||
  		    (tunnel->i_seqno &&
  		     (s32)(ntohl(tpi->seq) - tunnel->i_seqno) < 0)) {
  			tunnel->dev->stats.rx_fifo_errors++;
  			tunnel->dev->stats.rx_errors++;
  			goto drop;

  		}

  		tunnel->i_seqno = ntohl(tpi->seq) + 1;
  	}

  	skb->protocol = tpi->proto;

  	/* Warning: All skb pointers will be invalidated! */
  	if (tunnel->dev->type == ARPHRD_ETHER) {
  		if (!pskb_may_pull(skb, ETH_HLEN)) {
  			tunnel->dev->stats.rx_length_errors++;
  			tunnel->dev->stats.rx_errors++;
  			goto drop;

  		}

  
  		ipv6h = ipv6_hdr(skb);
  		skb->protocol = eth_type_trans(skb, tunnel->dev);
  		skb_postpull_rcsum(skb, eth_hdr(skb), ETH_HLEN);
  	} else {
  		skb->dev = tunnel->dev;
  	}
  
  	skb_reset_network_header(skb);
  	memset(skb->cb, 0, sizeof(struct inet6_skb_parm));
  
  	__skb_tunnel_rx(skb, tunnel->dev, tunnel->net);
  
  	err = dscp_ecn_decapsulate(tunnel, ipv6h, skb);
  	if (unlikely(err)) {
  		if (log_ecn_err)
  			net_info_ratelimited("non-ECT from %pI6 with DS=%#x
  ",
  					     &ipv6h->saddr,
  					     ipv6_get_dsfield(ipv6h));
  		if (err > 1) {
  			++tunnel->dev->stats.rx_frame_errors;
  			++tunnel->dev->stats.rx_errors;
  			goto drop;

  		}

  	}

  	tstats = this_cpu_ptr(tunnel->dev->tstats);
  	u64_stats_update_begin(&tstats->syncp);
  	tstats->rx_packets++;
  	tstats->rx_bytes += skb->len;
  	u64_stats_update_end(&tstats->syncp);

  	skb_scrub_packet(skb, !net_eq(tunnel->net, dev_net(tunnel->dev)));

  	if (tun_dst)
  		skb_dst_set(skb, (struct dst_entry *)tun_dst);

  	gro_cells_receive(&tunnel->gro_cells, skb);
  	return 0;
  
  drop:

  	if (tun_dst)
  		dst_release((struct dst_entry *)tun_dst);

  	kfree_skb(skb);
  	return 0;
  }
  
  int ip6_tnl_rcv(struct ip6_tnl *t, struct sk_buff *skb,
  		const struct tnl_ptk_info *tpi,
  		struct metadata_dst *tun_dst,
  		bool log_ecn_err)
  {

  	int (*dscp_ecn_decapsulate)(const struct ip6_tnl *t,
  				    const struct ipv6hdr *ipv6h,
  				    struct sk_buff *skb);
  
  	dscp_ecn_decapsulate = ip6ip6_dscp_ecn_decapsulate;
  	if (tpi->proto == htons(ETH_P_IP))
  		dscp_ecn_decapsulate = ip4ip6_dscp_ecn_decapsulate;
  
  	return __ip6_tnl_rcv(t, skb, tpi, tun_dst, dscp_ecn_decapsulate,

  			     log_ecn_err);
  }
  EXPORT_SYMBOL(ip6_tnl_rcv);
  
  static const struct tnl_ptk_info tpi_v6 = {
  	/* no tunnel info required for ipxip6. */
  	.proto = htons(ETH_P_IPV6),
  };
  
  static const struct tnl_ptk_info tpi_v4 = {
  	/* no tunnel info required for ipxip6. */
  	.proto = htons(ETH_P_IP),
  };

  static const struct tnl_ptk_info tpi_mpls = {
  	/* no tunnel info required for mplsip6. */
  	.proto = htons(ETH_P_MPLS_UC),
  };

  static int ipxip6_rcv(struct sk_buff *skb, u8 ipproto,
  		      const struct tnl_ptk_info *tpi,
  		      int (*dscp_ecn_decapsulate)(const struct ip6_tnl *t,
  						  const struct ipv6hdr *ipv6h,
  						  struct sk_buff *skb))
  {
  	struct ip6_tnl *t;
  	const struct ipv6hdr *ipv6h = ipv6_hdr(skb);

  	struct metadata_dst *tun_dst = NULL;

  	int ret = -1;
  
  	rcu_read_lock();

  	t = ip6_tnl_lookup(dev_net(skb->dev), skb->dev->ifindex, &ipv6h->saddr, &ipv6h->daddr);

  
  	if (t) {

  		u8 tproto = READ_ONCE(t->parms.proto);

  
  		if (tproto != ipproto && tproto != 0)
  			goto drop;
  		if (!xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb))
  			goto drop;

  		ipv6h = ipv6_hdr(skb);

  		if (!ip6_tnl_rcv_ctl(t, &ipv6h->daddr, &ipv6h->saddr))
  			goto drop;
  		if (iptunnel_pull_header(skb, 0, tpi->proto, false))
  			goto drop;

  		if (t->parms.collect_md) {
  			tun_dst = ipv6_tun_rx_dst(skb, 0, 0, 0);
  			if (!tun_dst)

  				goto drop;

  		}
  		ret = __ip6_tnl_rcv(t, skb, tpi, tun_dst, dscp_ecn_decapsulate,

  				    log_ecn_error);

  	}

  	rcu_read_unlock();

  	return ret;
  
  drop:
  	rcu_read_unlock();

  	kfree_skb(skb);
  	return 0;

  }

  static int ip4ip6_rcv(struct sk_buff *skb)
  {

  	return ipxip6_rcv(skb, IPPROTO_IPIP, &tpi_v4,

  			  ip4ip6_dscp_ecn_decapsulate);

  }

  static int ip6ip6_rcv(struct sk_buff *skb)
  {

  	return ipxip6_rcv(skb, IPPROTO_IPV6, &tpi_v6,
  			  ip6ip6_dscp_ecn_decapsulate);

  }

  static int mplsip6_rcv(struct sk_buff *skb)
  {
  	return ipxip6_rcv(skb, IPPROTO_MPLS, &tpi_mpls,
  			  mplsip6_dscp_ecn_decapsulate);
  }

  struct ipv6_tel_txoption {
  	struct ipv6_txoptions ops;
  	__u8 dst_opt[8];
  };

  static void init_tel_txopt(struct ipv6_tel_txoption *opt, __u8 encap_limit)
  {
  	memset(opt, 0, sizeof(struct ipv6_tel_txoption));

  	opt->dst_opt[2] = IPV6_TLV_TNL_ENCAP_LIMIT;
  	opt->dst_opt[3] = 1;
  	opt->dst_opt[4] = encap_limit;
  	opt->dst_opt[5] = IPV6_TLV_PADN;
  	opt->dst_opt[6] = 1;

  	opt->ops.dst1opt = (struct ipv6_opt_hdr *) opt->dst_opt;

  	opt->ops.opt_nflen = 8;

  }
  
  /**

   * ip6_tnl_addr_conflict - compare packet addresses to tunnel's own

   *   @t: the outgoing tunnel device

   *   @hdr: IPv6 header from the incoming packet

   *
   * Description:

   *   Avoid trivial tunneling loop by checking that tunnel exit-point

   *   doesn't match source of incoming packet.
   *

   * Return:

   *   1 if conflict,
   *   0 else
   **/

  static inline bool

  ip6_tnl_addr_conflict(const struct ip6_tnl *t, const struct ipv6hdr *hdr)

  {
  	return ipv6_addr_equal(&t->parms.raddr, &hdr->saddr);
  }

  int ip6_tnl_xmit_ctl(struct ip6_tnl *t,
  		     const struct in6_addr *laddr,
  		     const struct in6_addr *raddr)

  {

  	struct __ip6_tnl_parm *p = &t->parms;

  	int ret = 0;

  	struct net *net = t->net;

  	if (t->parms.collect_md)
  		return 1;

  	if ((p->flags & IP6_TNL_F_CAP_XMIT) ||
  	    ((p->flags & IP6_TNL_F_CAP_PER_PACKET) &&
  	     (ip6_tnl_get_cap(t, laddr, raddr) & IP6_TNL_F_CAP_XMIT))) {

  		struct net_device *ldev = NULL;

  		rcu_read_lock();

  		if (p->link)

  			ldev = dev_get_by_index_rcu(net, p->link);

  		if (unlikely(!ipv6_chk_addr_and_flags(net, laddr, ldev, false,
  						      0, IFA_F_TENTATIVE)))

  			pr_warn("%s xmit: Local address not yet configured!
  ",
  				p->name);

  		else if (!(p->flags & IP6_TNL_F_ALLOW_LOCAL_REMOTE) &&
  			 !ipv6_addr_is_multicast(raddr) &&

  			 unlikely(ipv6_chk_addr_and_flags(net, raddr, ldev,
  							  true, 0, IFA_F_TENTATIVE)))

  			pr_warn("%s xmit: Routing loop! Remote address found on this node!
  ",
  				p->name);

  		else
  			ret = 1;

  		rcu_read_unlock();

  	}
  	return ret;
  }

  EXPORT_SYMBOL_GPL(ip6_tnl_xmit_ctl);

  /**

   * ip6_tnl_xmit - encapsulate packet and send

   *   @skb: the outgoing socket buffer

   *   @dev: the outgoing tunnel device

   *   @dsfield: dscp code for outer header

   *   @fl6: flow of tunneled packet

   *   @encap_limit: encapsulation limit
   *   @pmtu: Path MTU is stored if packet is too big

   *   @proto: next header value

   *
   * Description:
   *   Build new header and do some sanity checks on the packet before sending
   *   it.
   *

   * Return:

   *   0 on success

   *   -1 fail
   *   %-EMSGSIZE message too big. return mtu in this case.

   **/

  int ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev, __u8 dsfield,
  		 struct flowi6 *fl6, int encap_limit, __u32 *pmtu,
  		 __u8 proto)

  {

  	struct ip6_tnl *t = netdev_priv(dev);

  	struct net *net = t->net;

  	struct net_device_stats *stats = &t->dev->stats;

  	struct ipv6hdr *ipv6h;

  	struct ipv6_tel_txoption opt;

  	struct dst_entry *dst = NULL, *ndst = NULL;

  	struct net_device *tdev;
  	int mtu;

  	unsigned int eth_hlen = t->dev->type == ARPHRD_ETHER ? ETH_HLEN : 0;

  	unsigned int psh_hlen = sizeof(struct ipv6hdr) + t->encap_hlen;
  	unsigned int max_headroom = psh_hlen;

  	bool use_cache = false;

  	u8 hop_limit;

  	int err = -1;

  	if (t->parms.collect_md) {
  		hop_limit = skb_tunnel_info(skb)->key.ttl;
  		goto route_lookup;
  	} else {
  		hop_limit = t->parms.hop_limit;
  	}

  	/* NBMA tunnel */
  	if (ipv6_addr_any(&t->parms.raddr)) {

  		if (skb->protocol == htons(ETH_P_IPV6)) {
  			struct in6_addr *addr6;
  			struct neighbour *neigh;
  			int addr_type;

  			if (!skb_dst(skb))
  				goto tx_err_link_failure;

  			neigh = dst_neigh_lookup(skb_dst(skb),
  						 &ipv6_hdr(skb)->daddr);
  			if (!neigh)
  				goto tx_err_link_failure;

  			addr6 = (struct in6_addr *)&neigh->primary_key;
  			addr_type = ipv6_addr_type(addr6);

  			if (addr_type == IPV6_ADDR_ANY)
  				addr6 = &ipv6_hdr(skb)->daddr;

  			memcpy(&fl6->daddr, addr6, sizeof(fl6->daddr));
  			neigh_release(neigh);
  		}

  	} else if (t->parms.proto != 0 && !(t->parms.flags &
  					    (IP6_TNL_F_USE_ORIG_TCLASS |
  					     IP6_TNL_F_USE_ORIG_FWMARK))) {
  		/* enable the cache only if neither the outer protocol nor the
  		 * routing decision depends on the current inner header value

  		 */
  		use_cache = true;
  	}
  
  	if (use_cache)

  		dst = dst_cache_get(&t->dst_cache);

  
  	if (!ip6_tnl_xmit_ctl(t, &fl6->saddr, &fl6->daddr))
  		goto tx_err_link_failure;

  	if (!dst) {

  route_lookup:

  		/* add dsfield to flowlabel for route lookup */
  		fl6->flowlabel = ip6_make_flowinfo(dsfield, fl6->flowlabel);

  		dst = ip6_route_output(net, NULL, fl6);

  		if (dst->error)

  			goto tx_err_link_failure;

  		dst = xfrm_lookup(net, dst, flowi6_to_flowi(fl6), NULL, 0);
  		if (IS_ERR(dst)) {
  			err = PTR_ERR(dst);
  			dst = NULL;

  			goto tx_err_link_failure;
  		}

  		if (t->parms.collect_md && ipv6_addr_any(&fl6->saddr) &&

  		    ipv6_dev_get_saddr(net, ip6_dst_idev(dst)->dev,
  				       &fl6->daddr, 0, &fl6->saddr))
  			goto tx_err_link_failure;

  		ndst = dst;

  	}

  
  	tdev = dst->dev;
  
  	if (tdev == dev) {
  		stats->collisions++;

  		net_warn_ratelimited("%s: Local routing loop detected!
  ",
  				     t->parms.name);

  		goto tx_err_dst_release;
  	}

  	mtu = dst_mtu(dst) - eth_hlen - psh_hlen - t->tun_hlen;

  	if (encap_limit >= 0) {

  		max_headroom += 8;
  		mtu -= 8;
  	}

  	mtu = max(mtu, skb->protocol == htons(ETH_P_IPV6) ?
  		       IPV6_MIN_MTU : IPV4_MIN_MTU);

  	skb_dst_update_pmtu_no_confirm(skb, mtu);

  	if (skb->len - t->tun_hlen - eth_hlen > mtu && !skb_is_gso(skb)) {

  		*pmtu = mtu;
  		err = -EMSGSIZE;

  		goto tx_err_dst_release;
  	}

  	if (t->err_count > 0) {
  		if (time_before(jiffies,
  				t->err_time + IP6TUNNEL_ERR_TIMEO)) {
  			t->err_count--;
  
  			dst_link_failure(skb);
  		} else {
  			t->err_count = 0;
  		}
  	}

  	skb_scrub_packet(skb, !net_eq(t->net, dev_net(dev)));

  	/*
  	 * Okay, now see if we can stuff it in the buffer as-is.
  	 */
  	max_headroom += LL_RESERVED_SPACE(tdev);

  	if (skb_headroom(skb) < max_headroom || skb_shared(skb) ||
  	    (skb_cloned(skb) && !skb_clone_writable(skb, 0))) {

  		struct sk_buff *new_skb;

  		new_skb = skb_realloc_headroom(skb, max_headroom);
  		if (!new_skb)

  			goto tx_err_dst_release;
  
  		if (skb->sk)
  			skb_set_owner_w(new_skb, skb->sk);

  		consume_skb(skb);

  		skb = new_skb;
  	}

  	if (t->parms.collect_md) {
  		if (t->encap.type != TUNNEL_ENCAP_NONE)
  			goto tx_err_dst_release;
  	} else {

  		if (use_cache && ndst)

  			dst_cache_set_ip6(&t->dst_cache, ndst, &fl6->saddr);
  	}

  	skb_dst_set(skb, dst);

  	if (hop_limit == 0) {
  		if (skb->protocol == htons(ETH_P_IP))
  			hop_limit = ip_hdr(skb)->ttl;
  		else if (skb->protocol == htons(ETH_P_IPV6))
  			hop_limit = ipv6_hdr(skb)->hop_limit;
  		else
  			hop_limit = ip6_dst_hoplimit(dst);
  	}

  	/* Calculate max headroom for all the headers and adjust
  	 * needed_headroom if necessary.
  	 */

  	max_headroom = LL_RESERVED_SPACE(dst->dev) + sizeof(struct ipv6hdr)

  			+ dst->header_len + t->hlen;

  	if (max_headroom > dev->needed_headroom)
  		dev->needed_headroom = max_headroom;

  	skb_set_inner_ipproto(skb, proto);

  	err = ip6_tnl_encap(skb, t, &proto, fl6);
  	if (err)
  		return err;

  	if (encap_limit >= 0) {
  		init_tel_txopt(&opt, encap_limit);
  		ipv6_push_frag_opts(skb, &opt.ops, &proto);
  	}

  	skb_push(skb, sizeof(struct ipv6hdr));
  	skb_reset_network_header(skb);

  	ipv6h = ipv6_hdr(skb);

  	ip6_flow_hdr(ipv6h, dsfield,

  		     ip6_make_flowlabel(net, skb, fl6->flowlabel, true, fl6));

  	ipv6h->hop_limit = hop_limit;

  	ipv6h->nexthdr = proto;

  	ipv6h->saddr = fl6->saddr;
  	ipv6h->daddr = fl6->daddr;

  	ip6tunnel_xmit(NULL, skb, dev);

  	return 0;
  tx_err_link_failure:
  	stats->tx_carrier_errors++;
  	dst_link_failure(skb);
  tx_err_dst_release:

  	dst_release(dst);

  	return err;
  }

  EXPORT_SYMBOL(ip6_tnl_xmit);

  
  static inline int

  ipxip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev,
  		u8 protocol)

  {
  	struct ip6_tnl *t = netdev_priv(dev);

  	struct ipv6hdr *ipv6h;

  	const struct iphdr  *iph;

  	int encap_limit = -1;

  	__u16 offset;

  	struct flowi6 fl6;

  	__u8 dsfield, orig_dsfield;

  	__u32 mtu;

  	u8 tproto;

  	int err;

  	tproto = READ_ONCE(t->parms.proto);

  	if (tproto != protocol && tproto != 0)

  		return -1;

  	if (t->parms.collect_md) {
  		struct ip_tunnel_info *tun_info;
  		const struct ip_tunnel_key *key;

  		tun_info = skb_tunnel_info(skb);
  		if (unlikely(!tun_info || !(tun_info->mode & IP_TUNNEL_INFO_TX) ||
  			     ip_tunnel_info_af(tun_info) != AF_INET6))
  			return -1;
  		key = &tun_info->key;
  		memset(&fl6, 0, sizeof(fl6));

  		fl6.flowi6_proto = protocol;

  		fl6.saddr = key->u.ipv6.src;

  		fl6.daddr = key->u.ipv6.dst;
  		fl6.flowlabel = key->label;

  		dsfield =  key->tos;

  		switch (protocol) {
  		case IPPROTO_IPIP:
  			iph = ip_hdr(skb);
  			orig_dsfield = ipv4_get_dsfield(iph);
  			break;
  		case IPPROTO_IPV6:
  			ipv6h = ipv6_hdr(skb);
  			orig_dsfield = ipv6_get_dsfield(ipv6h);
  			break;
  		default:
  			orig_dsfield = dsfield;
  			break;
  		}

  	} else {
  		if (!(t->parms.flags & IP6_TNL_F_IGN_ENCAP_LIMIT))
  			encap_limit = t->parms.encap_limit;

  		if (protocol == IPPROTO_IPV6) {
  			offset = ip6_tnl_parse_tlv_enc_lim(skb,
  						skb_network_header(skb));
  			/* ip6_tnl_parse_tlv_enc_lim() might have
  			 * reallocated skb->head
  			 */
  			if (offset > 0) {
  				struct ipv6_tlv_tnl_enc_lim *tel;

  				tel = (void *)&skb_network_header(skb)[offset];
  				if (tel->encap_limit == 0) {
  					icmpv6_send(skb, ICMPV6_PARAMPROB,
  						ICMPV6_HDR_FIELD, offset + 2);
  					return -1;
  				}
  				encap_limit = tel->encap_limit - 1;

  			}