net/core/lwtunnel.c - kernel/msm-4.19 - Gitiles

 /*
  * lwtunnel	Infrastructure for light weight tunnels like mpls
  *
  * Authors:	Roopa Prabhu, <roopa@cumulusnetworks.com>
  *
  *		This program is free software; you can redistribute it and/or
  *		modify it under the terms of the GNU General Public License
  *		as published by the Free Software Foundation; either version
  *		2 of the License, or (at your option) any later version.
  *
  */

 #include <linux/capability.h>
 #include <linux/module.h>
 #include <linux/types.h>
 #include <linux/kernel.h>
 #include <linux/slab.h>
 #include <linux/uaccess.h>
 #include <linux/skbuff.h>
 #include <linux/netdevice.h>
 #include <linux/lwtunnel.h>
 #include <linux/in.h>
 #include <linux/init.h>
 #include <linux/err.h>

 #include <net/lwtunnel.h>
 #include <net/rtnetlink.h>
 #include <net/ip6_fib.h>
 #include <net/nexthop.h>

 #ifdef CONFIG_MODULES

 static const char *lwtunnel_encap_str(enum lwtunnel_encap_types encap_type)
 {
 	/* Only lwt encaps implemented without using an interface for
 	 * the encap need to return a string here.
 	 */
 	switch (encap_type) {
 	case LWTUNNEL_ENCAP_MPLS:
 		return "MPLS";
 	case LWTUNNEL_ENCAP_ILA:
 		return "ILA";
 	case LWTUNNEL_ENCAP_SEG6:
 		return "SEG6";
 	case LWTUNNEL_ENCAP_BPF:
 		return "BPF";
 	case LWTUNNEL_ENCAP_IP6:
 	case LWTUNNEL_ENCAP_IP:
 	case LWTUNNEL_ENCAP_NONE:
 	case __LWTUNNEL_ENCAP_MAX:
 		/* should not have got here */
 		WARN_ON(1);
 		break;
 	}
 	return NULL;
 }

 #endif /* CONFIG_MODULES */

 struct lwtunnel_state *lwtunnel_state_alloc(int encap_len)
 {
 	struct lwtunnel_state *lws;

 	lws = kzalloc(sizeof(*lws) + encap_len, GFP_ATOMIC);

 	return lws;
 }
 EXPORT_SYMBOL(lwtunnel_state_alloc);

 static const struct lwtunnel_encap_ops __rcu *
 		lwtun_encaps[LWTUNNEL_ENCAP_MAX + 1] __read_mostly;

 int lwtunnel_encap_add_ops(const struct lwtunnel_encap_ops *ops,
 			   unsigned int num)
 {
 	if (num > LWTUNNEL_ENCAP_MAX)
 		return -ERANGE;

 	return !cmpxchg((const struct lwtunnel_encap_ops **)
 			&lwtun_encaps[num],
 			NULL, ops) ? 0 : -1;
 }
 EXPORT_SYMBOL(lwtunnel_encap_add_ops);

 int lwtunnel_encap_del_ops(const struct lwtunnel_encap_ops *ops,
 			   unsigned int encap_type)
 {
 	int ret;

 	if (encap_type == LWTUNNEL_ENCAP_NONE ||
 	    encap_type > LWTUNNEL_ENCAP_MAX)
 		return -ERANGE;

 	ret = (cmpxchg((const struct lwtunnel_encap_ops **)
 		       &lwtun_encaps[encap_type],
 		       ops, NULL) == ops) ? 0 : -1;

 	synchronize_net();

 	return ret;
 }
 EXPORT_SYMBOL(lwtunnel_encap_del_ops);

 int lwtunnel_build_state(u16 encap_type,
 			 struct nlattr *encap, unsigned int family,
 			 const void *cfg, struct lwtunnel_state **lws,
 			 struct netlink_ext_ack *extack)
 {
 	const struct lwtunnel_encap_ops *ops;
 	bool found = false;
 	int ret = -EINVAL;

 	if (encap_type == LWTUNNEL_ENCAP_NONE ||
 	    encap_type > LWTUNNEL_ENCAP_MAX) {
 		NL_SET_ERR_MSG_ATTR(extack, encap,
 				    "Unknown LWT encapsulation type");
 		return ret;
 	}

 	ret = -EOPNOTSUPP;
 	rcu_read_lock();
 	ops = rcu_dereference(lwtun_encaps[encap_type]);
 	if (likely(ops && ops->build_state && try_module_get(ops->owner))) {
 		found = true;
 		ret = ops->build_state(encap, family, cfg, lws, extack);
 		if (ret)
 			module_put(ops->owner);
 	}
 	rcu_read_unlock();

 	/* don't rely on -EOPNOTSUPP to detect match as build_state
 	 * handlers could return it
 	 */
 	if (!found) {
 		NL_SET_ERR_MSG_ATTR(extack, encap,
 				    "LWT encapsulation type not supported");
 	}

 	return ret;
 }
 EXPORT_SYMBOL(lwtunnel_build_state);

 int lwtunnel_valid_encap_type(u16 encap_type, struct netlink_ext_ack *extack)
 {
 	const struct lwtunnel_encap_ops *ops;
 	int ret = -EINVAL;

 	if (encap_type == LWTUNNEL_ENCAP_NONE ||
 	    encap_type > LWTUNNEL_ENCAP_MAX) {
 		NL_SET_ERR_MSG(extack, "Unknown lwt encapsulation type");
 		return ret;
 	}

 	rcu_read_lock();
 	ops = rcu_dereference(lwtun_encaps[encap_type]);
 	rcu_read_unlock();
 #ifdef CONFIG_MODULES
 	if (!ops) {
 		const char *encap_type_str = lwtunnel_encap_str(encap_type);

 		if (encap_type_str) {
 			__rtnl_unlock();
 			request_module("rtnl-lwt-%s", encap_type_str);
 			rtnl_lock();

 			rcu_read_lock();
 			ops = rcu_dereference(lwtun_encaps[encap_type]);
 			rcu_read_unlock();
 		}
 	}
 #endif
 	ret = ops ? 0 : -EOPNOTSUPP;
 	if (ret < 0)
 		NL_SET_ERR_MSG(extack, "lwt encapsulation type not supported");

 	return ret;
 }
 EXPORT_SYMBOL(lwtunnel_valid_encap_type);

 int lwtunnel_valid_encap_type_attr(struct nlattr *attr, int remaining,
 				   struct netlink_ext_ack *extack)
 {
 	struct rtnexthop *rtnh = (struct rtnexthop *)attr;
 	struct nlattr *nla_entype;
 	struct nlattr *attrs;
 	u16 encap_type;
 	int attrlen;

 	while (rtnh_ok(rtnh, remaining)) {
 		attrlen = rtnh_attrlen(rtnh);
 		if (attrlen > 0) {
 			attrs = rtnh_attrs(rtnh);
 			nla_entype = nla_find(attrs, attrlen, RTA_ENCAP_TYPE);

 			if (nla_entype) {
 				encap_type = nla_get_u16(nla_entype);

 				if (lwtunnel_valid_encap_type(encap_type,
 							      extack) != 0)
 					return -EOPNOTSUPP;
 			}
 		}
 		rtnh = rtnh_next(rtnh, &remaining);
 	}

 	return 0;
 }
 EXPORT_SYMBOL(lwtunnel_valid_encap_type_attr);

 void lwtstate_free(struct lwtunnel_state *lws)
 {
 	const struct lwtunnel_encap_ops *ops = lwtun_encaps[lws->type];

 	if (ops->destroy_state) {
 		ops->destroy_state(lws);
 		kfree_rcu(lws, rcu);
 	} else {
 		kfree(lws);
 	}
 	module_put(ops->owner);
 }
 EXPORT_SYMBOL(lwtstate_free);

 int lwtunnel_fill_encap(struct sk_buff *skb, struct lwtunnel_state *lwtstate)
 {
 	const struct lwtunnel_encap_ops *ops;
 	struct nlattr *nest;
 	int ret;

 	if (!lwtstate)
 		return 0;

 	if (lwtstate->type == LWTUNNEL_ENCAP_NONE ||
 	    lwtstate->type > LWTUNNEL_ENCAP_MAX)
 		return 0;

 	nest = nla_nest_start(skb, RTA_ENCAP);
 	if (!nest)
 		return -EMSGSIZE;

 	ret = -EOPNOTSUPP;
 	rcu_read_lock();
 	ops = rcu_dereference(lwtun_encaps[lwtstate->type]);
 	if (likely(ops && ops->fill_encap))
 		ret = ops->fill_encap(skb, lwtstate);
 	rcu_read_unlock();

 	if (ret)
 		goto nla_put_failure;
 	nla_nest_end(skb, nest);
 	ret = nla_put_u16(skb, RTA_ENCAP_TYPE, lwtstate->type);
 	if (ret)
 		goto nla_put_failure;

 	return 0;

 nla_put_failure:
 	nla_nest_cancel(skb, nest);

 	return (ret == -EOPNOTSUPP ? 0 : ret);
 }
 EXPORT_SYMBOL(lwtunnel_fill_encap);

 int lwtunnel_get_encap_size(struct lwtunnel_state *lwtstate)
 {
 	const struct lwtunnel_encap_ops *ops;
 	int ret = 0;

 	if (!lwtstate)
 		return 0;

 	if (lwtstate->type == LWTUNNEL_ENCAP_NONE ||
 	    lwtstate->type > LWTUNNEL_ENCAP_MAX)
 		return 0;

 	rcu_read_lock();
 	ops = rcu_dereference(lwtun_encaps[lwtstate->type]);
 	if (likely(ops && ops->get_encap_size))
 		ret = nla_total_size(ops->get_encap_size(lwtstate));
 	rcu_read_unlock();

 	return ret;
 }
 EXPORT_SYMBOL(lwtunnel_get_encap_size);

 int lwtunnel_cmp_encap(struct lwtunnel_state *a, struct lwtunnel_state *b)
 {
 	const struct lwtunnel_encap_ops *ops;
 	int ret = 0;

 	if (!a && !b)
 		return 0;

 	if (!a || !b)
 		return 1;

 	if (a->type != b->type)
 		return 1;

 	if (a->type == LWTUNNEL_ENCAP_NONE ||
 	    a->type > LWTUNNEL_ENCAP_MAX)
 		return 0;

 	rcu_read_lock();
 	ops = rcu_dereference(lwtun_encaps[a->type]);
 	if (likely(ops && ops->cmp_encap))
 		ret = ops->cmp_encap(a, b);
 	rcu_read_unlock();

 	return ret;
 }
 EXPORT_SYMBOL(lwtunnel_cmp_encap);

 int lwtunnel_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 {
 	struct dst_entry *dst = skb_dst(skb);
 	const struct lwtunnel_encap_ops *ops;
 	struct lwtunnel_state *lwtstate;
 	int ret = -EINVAL;

 	if (!dst)
 		goto drop;
 	lwtstate = dst->lwtstate;

 	if (lwtstate->type == LWTUNNEL_ENCAP_NONE ||
 	    lwtstate->type > LWTUNNEL_ENCAP_MAX)
 		return 0;

 	ret = -EOPNOTSUPP;
 	rcu_read_lock();
 	ops = rcu_dereference(lwtun_encaps[lwtstate->type]);
 	if (likely(ops && ops->output))
 		ret = ops->output(net, sk, skb);
 	rcu_read_unlock();

 	if (ret == -EOPNOTSUPP)
 		goto drop;

 	return ret;

 drop:
 	kfree_skb(skb);

 	return ret;
 }
 EXPORT_SYMBOL(lwtunnel_output);

 int lwtunnel_xmit(struct sk_buff *skb)
 {
 	struct dst_entry *dst = skb_dst(skb);
 	const struct lwtunnel_encap_ops *ops;
 	struct lwtunnel_state *lwtstate;
 	int ret = -EINVAL;

 	if (!dst)
 		goto drop;

 	lwtstate = dst->lwtstate;

 	if (lwtstate->type == LWTUNNEL_ENCAP_NONE ||
 	    lwtstate->type > LWTUNNEL_ENCAP_MAX)
 		return 0;

 	ret = -EOPNOTSUPP;
 	rcu_read_lock();
 	ops = rcu_dereference(lwtun_encaps[lwtstate->type]);
 	if (likely(ops && ops->xmit))
 		ret = ops->xmit(skb);
 	rcu_read_unlock();

 	if (ret == -EOPNOTSUPP)
 		goto drop;

 	return ret;

 drop:
 	kfree_skb(skb);

 	return ret;
 }
 EXPORT_SYMBOL(lwtunnel_xmit);

 int lwtunnel_input(struct sk_buff *skb)
 {
 	struct dst_entry *dst = skb_dst(skb);
 	const struct lwtunnel_encap_ops *ops;
 	struct lwtunnel_state *lwtstate;
 	int ret = -EINVAL;

 	if (!dst)
 		goto drop;
 	lwtstate = dst->lwtstate;

 	if (lwtstate->type == LWTUNNEL_ENCAP_NONE ||
 	    lwtstate->type > LWTUNNEL_ENCAP_MAX)
 		return 0;

 	ret = -EOPNOTSUPP;
 	rcu_read_lock();
 	ops = rcu_dereference(lwtun_encaps[lwtstate->type]);
 	if (likely(ops && ops->input))
 		ret = ops->input(skb);
 	rcu_read_unlock();

 	if (ret == -EOPNOTSUPP)
 		goto drop;

 	return ret;

 drop:
 	kfree_skb(skb);

 	return ret;
 }
 EXPORT_SYMBOL(lwtunnel_input);
	/*
	* lwtunnel Infrastructure for light weight tunnels like mpls
	*
	* Authors: Roopa Prabhu, <roopa@cumulusnetworks.com>
	*
	* This program is free software; you can redistribute it and/or
	* modify it under the terms of the GNU General Public License
	* as published by the Free Software Foundation; either version
	* 2 of the License, or (at your option) any later version.
	*
	*/

	#include <linux/capability.h>
	#include <linux/module.h>
	#include <linux/types.h>
	#include <linux/kernel.h>
	#include <linux/slab.h>
	#include <linux/uaccess.h>
	#include <linux/skbuff.h>
	#include <linux/netdevice.h>
	#include <linux/lwtunnel.h>
	#include <linux/in.h>
	#include <linux/init.h>
	#include <linux/err.h>

	#include <net/lwtunnel.h>
	#include <net/rtnetlink.h>
	#include <net/ip6_fib.h>
	#include <net/nexthop.h>

	#ifdef CONFIG_MODULES

	static const char *lwtunnel_encap_str(enum lwtunnel_encap_types encap_type)
	{
	/* Only lwt encaps implemented without using an interface for
	* the encap need to return a string here.
	*/
	switch (encap_type) {
	case LWTUNNEL_ENCAP_MPLS:
	return "MPLS";
	case LWTUNNEL_ENCAP_ILA:
	return "ILA";
	case LWTUNNEL_ENCAP_SEG6:
	return "SEG6";
	case LWTUNNEL_ENCAP_BPF:
	return "BPF";
	case LWTUNNEL_ENCAP_IP6:
	case LWTUNNEL_ENCAP_IP:
	case LWTUNNEL_ENCAP_NONE:
	case __LWTUNNEL_ENCAP_MAX:
	/* should not have got here */
	WARN_ON(1);
	break;
	}
	return NULL;
	}

	#endif /* CONFIG_MODULES */

	struct lwtunnel_state *lwtunnel_state_alloc(int encap_len)
	{
	struct lwtunnel_state *lws;

	lws = kzalloc(sizeof(*lws) + encap_len, GFP_ATOMIC);

	return lws;
	}
	EXPORT_SYMBOL(lwtunnel_state_alloc);

	static const struct lwtunnel_encap_ops __rcu *
	lwtun_encaps[LWTUNNEL_ENCAP_MAX + 1] __read_mostly;

	int lwtunnel_encap_add_ops(const struct lwtunnel_encap_ops *ops,
	unsigned int num)
	{
	if (num > LWTUNNEL_ENCAP_MAX)
	return -ERANGE;

	return !cmpxchg((const struct lwtunnel_encap_ops **)
	&lwtun_encaps[num],
	NULL, ops) ? 0 : -1;
	}
	EXPORT_SYMBOL(lwtunnel_encap_add_ops);

	int lwtunnel_encap_del_ops(const struct lwtunnel_encap_ops *ops,
	unsigned int encap_type)
	{
	int ret;

	if (encap_type == LWTUNNEL_ENCAP_NONE \|\|
	encap_type > LWTUNNEL_ENCAP_MAX)
	return -ERANGE;

	ret = (cmpxchg((const struct lwtunnel_encap_ops **)
	&lwtun_encaps[encap_type],
	ops, NULL) == ops) ? 0 : -1;

	synchronize_net();

	return ret;
	}
	EXPORT_SYMBOL(lwtunnel_encap_del_ops);

	int lwtunnel_build_state(u16 encap_type,
	struct nlattr *encap, unsigned int family,
	const void cfg, struct lwtunnel_state *lws,
	struct netlink_ext_ack *extack)
	{
	const struct lwtunnel_encap_ops *ops;
	bool found = false;
	int ret = -EINVAL;

	if (encap_type == LWTUNNEL_ENCAP_NONE \|\|
	encap_type > LWTUNNEL_ENCAP_MAX) {
	NL_SET_ERR_MSG_ATTR(extack, encap,
	"Unknown LWT encapsulation type");
	return ret;
	}

	ret = -EOPNOTSUPP;
	rcu_read_lock();
	ops = rcu_dereference(lwtun_encaps[encap_type]);
	if (likely(ops && ops->build_state && try_module_get(ops->owner))) {
	found = true;
	ret = ops->build_state(encap, family, cfg, lws, extack);
	if (ret)
	module_put(ops->owner);
	}
	rcu_read_unlock();

	/* don't rely on -EOPNOTSUPP to detect match as build_state
	* handlers could return it
	*/
	if (!found) {
	NL_SET_ERR_MSG_ATTR(extack, encap,
	"LWT encapsulation type not supported");
	}

	return ret;
	}
	EXPORT_SYMBOL(lwtunnel_build_state);

	int lwtunnel_valid_encap_type(u16 encap_type, struct netlink_ext_ack *extack)
	{
	const struct lwtunnel_encap_ops *ops;
	int ret = -EINVAL;

	if (encap_type == LWTUNNEL_ENCAP_NONE \|\|
	encap_type > LWTUNNEL_ENCAP_MAX) {
	NL_SET_ERR_MSG(extack, "Unknown lwt encapsulation type");
	return ret;
	}

	rcu_read_lock();
	ops = rcu_dereference(lwtun_encaps[encap_type]);
	rcu_read_unlock();
	#ifdef CONFIG_MODULES
	if (!ops) {
	const char *encap_type_str = lwtunnel_encap_str(encap_type);

	if (encap_type_str) {
	__rtnl_unlock();
	request_module("rtnl-lwt-%s", encap_type_str);
	rtnl_lock();

	rcu_read_lock();
	ops = rcu_dereference(lwtun_encaps[encap_type]);
	rcu_read_unlock();
	}
	}
	#endif
	ret = ops ? 0 : -EOPNOTSUPP;
	if (ret < 0)
	NL_SET_ERR_MSG(extack, "lwt encapsulation type not supported");

	return ret;
	}
	EXPORT_SYMBOL(lwtunnel_valid_encap_type);

	int lwtunnel_valid_encap_type_attr(struct nlattr *attr, int remaining,
	struct netlink_ext_ack *extack)
	{
	struct rtnexthop rtnh = (struct rtnexthop )attr;
	struct nlattr *nla_entype;
	struct nlattr *attrs;
	u16 encap_type;
	int attrlen;

	while (rtnh_ok(rtnh, remaining)) {
	attrlen = rtnh_attrlen(rtnh);
	if (attrlen > 0) {
	attrs = rtnh_attrs(rtnh);
	nla_entype = nla_find(attrs, attrlen, RTA_ENCAP_TYPE);

	if (nla_entype) {
	encap_type = nla_get_u16(nla_entype);

	if (lwtunnel_valid_encap_type(encap_type,
	extack) != 0)
	return -EOPNOTSUPP;
	}
	}
	rtnh = rtnh_next(rtnh, &remaining);
	}

	return 0;
	}
	EXPORT_SYMBOL(lwtunnel_valid_encap_type_attr);

	void lwtstate_free(struct lwtunnel_state *lws)
	{
	const struct lwtunnel_encap_ops *ops = lwtun_encaps[lws->type];

	if (ops->destroy_state) {
	ops->destroy_state(lws);
	kfree_rcu(lws, rcu);
	} else {
	kfree(lws);
	}
	module_put(ops->owner);
	}
	EXPORT_SYMBOL(lwtstate_free);

	int lwtunnel_fill_encap(struct sk_buff skb, struct lwtunnel_state lwtstate)
	{
	const struct lwtunnel_encap_ops *ops;
	struct nlattr *nest;
	int ret;

	if (!lwtstate)
	return 0;

	if (lwtstate->type == LWTUNNEL_ENCAP_NONE \|\|
	lwtstate->type > LWTUNNEL_ENCAP_MAX)
	return 0;

	nest = nla_nest_start(skb, RTA_ENCAP);
	if (!nest)
	return -EMSGSIZE;

	ret = -EOPNOTSUPP;
	rcu_read_lock();
	ops = rcu_dereference(lwtun_encaps[lwtstate->type]);
	if (likely(ops && ops->fill_encap))
	ret = ops->fill_encap(skb, lwtstate);
	rcu_read_unlock();

	if (ret)
	goto nla_put_failure;
	nla_nest_end(skb, nest);
	ret = nla_put_u16(skb, RTA_ENCAP_TYPE, lwtstate->type);
	if (ret)
	goto nla_put_failure;

	return 0;

	nla_put_failure:
	nla_nest_cancel(skb, nest);

	return (ret == -EOPNOTSUPP ? 0 : ret);
	}
	EXPORT_SYMBOL(lwtunnel_fill_encap);

	int lwtunnel_get_encap_size(struct lwtunnel_state *lwtstate)
	{
	const struct lwtunnel_encap_ops *ops;
	int ret = 0;

	if (!lwtstate)
	return 0;

	if (lwtstate->type == LWTUNNEL_ENCAP_NONE \|\|
	lwtstate->type > LWTUNNEL_ENCAP_MAX)
	return 0;

	rcu_read_lock();
	ops = rcu_dereference(lwtun_encaps[lwtstate->type]);
	if (likely(ops && ops->get_encap_size))
	ret = nla_total_size(ops->get_encap_size(lwtstate));
	rcu_read_unlock();

	return ret;
	}
	EXPORT_SYMBOL(lwtunnel_get_encap_size);

	int lwtunnel_cmp_encap(struct lwtunnel_state a, struct lwtunnel_state b)
	{
	const struct lwtunnel_encap_ops *ops;
	int ret = 0;

	if (!a && !b)
	return 0;

	if (!a \|\| !b)
	return 1;

	if (a->type != b->type)
	return 1;

	if (a->type == LWTUNNEL_ENCAP_NONE \|\|
	a->type > LWTUNNEL_ENCAP_MAX)
	return 0;

	rcu_read_lock();
	ops = rcu_dereference(lwtun_encaps[a->type]);
	if (likely(ops && ops->cmp_encap))
	ret = ops->cmp_encap(a, b);
	rcu_read_unlock();

	return ret;
	}
	EXPORT_SYMBOL(lwtunnel_cmp_encap);

	int lwtunnel_output(struct net net, struct sock sk, struct sk_buff *skb)
	{
	struct dst_entry *dst = skb_dst(skb);
	const struct lwtunnel_encap_ops *ops;
	struct lwtunnel_state *lwtstate;
	int ret = -EINVAL;

	if (!dst)
	goto drop;
	lwtstate = dst->lwtstate;

	if (lwtstate->type == LWTUNNEL_ENCAP_NONE \|\|
	lwtstate->type > LWTUNNEL_ENCAP_MAX)
	return 0;

	ret = -EOPNOTSUPP;
	rcu_read_lock();
	ops = rcu_dereference(lwtun_encaps[lwtstate->type]);
	if (likely(ops && ops->output))
	ret = ops->output(net, sk, skb);
	rcu_read_unlock();

	if (ret == -EOPNOTSUPP)
	goto drop;

	return ret;

	drop:
	kfree_skb(skb);

	return ret;
	}
	EXPORT_SYMBOL(lwtunnel_output);

	int lwtunnel_xmit(struct sk_buff *skb)
	{
	struct dst_entry *dst = skb_dst(skb);
	const struct lwtunnel_encap_ops *ops;
	struct lwtunnel_state *lwtstate;
	int ret = -EINVAL;

	if (!dst)
	goto drop;

	lwtstate = dst->lwtstate;

	if (lwtstate->type == LWTUNNEL_ENCAP_NONE \|\|
	lwtstate->type > LWTUNNEL_ENCAP_MAX)
	return 0;

	ret = -EOPNOTSUPP;
	rcu_read_lock();
	ops = rcu_dereference(lwtun_encaps[lwtstate->type]);
	if (likely(ops && ops->xmit))
	ret = ops->xmit(skb);
	rcu_read_unlock();

	if (ret == -EOPNOTSUPP)
	goto drop;

	return ret;

	drop:
	kfree_skb(skb);

	return ret;
	}
	EXPORT_SYMBOL(lwtunnel_xmit);

	int lwtunnel_input(struct sk_buff *skb)
	{
	struct dst_entry *dst = skb_dst(skb);
	const struct lwtunnel_encap_ops *ops;
	struct lwtunnel_state *lwtstate;
	int ret = -EINVAL;

	if (!dst)
	goto drop;
	lwtstate = dst->lwtstate;

	if (lwtstate->type == LWTUNNEL_ENCAP_NONE \|\|
	lwtstate->type > LWTUNNEL_ENCAP_MAX)
	return 0;

	ret = -EOPNOTSUPP;
	rcu_read_lock();
	ops = rcu_dereference(lwtun_encaps[lwtstate->type]);
	if (likely(ops && ops->input))
	ret = ops->input(skb);
	rcu_read_unlock();

	if (ret == -EOPNOTSUPP)
	goto drop;

	return ret;

	drop:
	kfree_skb(skb);

	return ret;
	}
	EXPORT_SYMBOL(lwtunnel_input);