include/net/dst.h - kernel/msm-4.9 - Gitiles

 /*
  * net/dst.h	Protocol independent destination cache definitions.
  *
  * Authors:	Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
  *
  */

 #ifndef _NET_DST_H
 #define _NET_DST_H

 #include <net/dst_ops.h>
 #include <linux/netdevice.h>
 #include <linux/rtnetlink.h>
 #include <linux/rcupdate.h>
 #include <linux/bug.h>
 #include <linux/jiffies.h>
 #include <net/neighbour.h>
 #include <asm/processor.h>

 #define DST_GC_MIN	(HZ/10)
 #define DST_GC_INC	(HZ/2)
 #define DST_GC_MAX	(120*HZ)

 /* Each dst_entry has reference count and sits in some parent list(s).
  * When it is removed from parent list, it is "freed" (dst_free).
  * After this it enters dead state (dst->obsolete > 0) and if its refcnt
  * is zero, it can be destroyed immediately, otherwise it is added
  * to gc list and garbage collector periodically checks the refcnt.
  */

 struct sk_buff;

 struct dst_entry {
 	struct rcu_head		rcu_head;
 	struct dst_entry	*child;
 	struct net_device       *dev;
 	struct  dst_ops	        *ops;
 	unsigned long		_metrics;
 	unsigned long           expires;
 	struct dst_entry	*path;
 	struct dst_entry	*from;
 #ifdef CONFIG_XFRM
 	struct xfrm_state	*xfrm;
 #else
 	void			*__pad1;
 #endif
 	int			(*input)(struct sk_buff *);
 	int			(*output)(struct sk_buff *);

 	unsigned short		flags;
 #define DST_HOST		0x0001
 #define DST_NOXFRM		0x0002
 #define DST_NOPOLICY		0x0004
 #define DST_NOHASH		0x0008
 #define DST_NOCACHE		0x0010
 #define DST_NOCOUNT		0x0020
 #define DST_FAKE_RTABLE		0x0040
 #define DST_XFRM_TUNNEL		0x0080
 #define DST_XFRM_QUEUE		0x0100

 	unsigned short		pending_confirm;

 	short			error;

 	/* A non-zero value of dst->obsolete forces by-hand validation
 	 * of the route entry.  Positive values are set by the generic
 	 * dst layer to indicate that the entry has been forcefully
 	 * destroyed.
 	 *
 	 * Negative values are used by the implementation layer code to
 	 * force invocation of the dst_ops->check() method.
 	 */
 	short			obsolete;
 #define DST_OBSOLETE_NONE	0
 #define DST_OBSOLETE_DEAD	2
 #define DST_OBSOLETE_FORCE_CHK	-1
 #define DST_OBSOLETE_KILL	-2
 	unsigned short		header_len;	/* more space at head required */
 	unsigned short		trailer_len;	/* space to reserve at tail */
 #ifdef CONFIG_IP_ROUTE_CLASSID
 	__u32			tclassid;
 #else
 	__u32			__pad2;
 #endif

 	/*
 	 * Align __refcnt to a 64 bytes alignment
 	 * (L1_CACHE_SIZE would be too much)
 	 */
 #ifdef CONFIG_64BIT
 	long			__pad_to_align_refcnt[2];
 #endif
 	/*
 	 * __refcnt wants to be on a different cache line from
 	 * input/output/ops or performance tanks badly
 	 */
 	atomic_t		__refcnt;	/* client references	*/
 	int			__use;
 	unsigned long		lastuse;
 	union {
 		struct dst_entry	*next;
 		struct rtable __rcu	*rt_next;
 		struct rt6_info		*rt6_next;
 		struct dn_route __rcu	*dn_next;
 	};
 };

 u32 *dst_cow_metrics_generic(struct dst_entry *dst, unsigned long old);
 extern const u32 dst_default_metrics[];

 #define DST_METRICS_READ_ONLY		0x1UL
 #define DST_METRICS_FORCE_OVERWRITE	0x2UL
 #define DST_METRICS_FLAGS		0x3UL
 #define __DST_METRICS_PTR(Y)	\
 	((u32 *)((Y) & ~DST_METRICS_FLAGS))
 #define DST_METRICS_PTR(X)	__DST_METRICS_PTR((X)->_metrics)

 static inline bool dst_metrics_read_only(const struct dst_entry *dst)
 {
 	return dst->_metrics & DST_METRICS_READ_ONLY;
 }

 static inline void dst_metrics_set_force_overwrite(struct dst_entry *dst)
 {
 	dst->_metrics |= DST_METRICS_FORCE_OVERWRITE;
 }

 void __dst_destroy_metrics_generic(struct dst_entry *dst, unsigned long old);

 static inline void dst_destroy_metrics_generic(struct dst_entry *dst)
 {
 	unsigned long val = dst->_metrics;
 	if (!(val & DST_METRICS_READ_ONLY))
 		__dst_destroy_metrics_generic(dst, val);
 }

 static inline u32 *dst_metrics_write_ptr(struct dst_entry *dst)
 {
 	unsigned long p = dst->_metrics;

 	BUG_ON(!p);

 	if (p & DST_METRICS_READ_ONLY)
 		return dst->ops->cow_metrics(dst, p);
 	return __DST_METRICS_PTR(p);
 }

 /* This may only be invoked before the entry has reached global
  * visibility.
  */
 static inline void dst_init_metrics(struct dst_entry *dst,
 				    const u32 *src_metrics,
 				    bool read_only)
 {
 	dst->_metrics = ((unsigned long) src_metrics) |
 		(read_only ? DST_METRICS_READ_ONLY : 0);
 }

 static inline void dst_copy_metrics(struct dst_entry *dest, const struct dst_entry *src)
 {
 	u32 *dst_metrics = dst_metrics_write_ptr(dest);

 	if (dst_metrics) {
 		u32 *src_metrics = DST_METRICS_PTR(src);

 		memcpy(dst_metrics, src_metrics, RTAX_MAX * sizeof(u32));
 	}
 }

 static inline u32 *dst_metrics_ptr(struct dst_entry *dst)
 {
 	return DST_METRICS_PTR(dst);
 }

 static inline u32
 dst_metric_raw(const struct dst_entry *dst, const int metric)
 {
 	u32 *p = DST_METRICS_PTR(dst);

 	return p[metric-1];
 }

 static inline u32
 dst_metric(const struct dst_entry *dst, const int metric)
 {
 	WARN_ON_ONCE(metric == RTAX_HOPLIMIT ||
 		     metric == RTAX_ADVMSS ||
 		     metric == RTAX_MTU);
 	return dst_metric_raw(dst, metric);
 }

 static inline u32
 dst_metric_advmss(const struct dst_entry *dst)
 {
 	u32 advmss = dst_metric_raw(dst, RTAX_ADVMSS);

 	if (!advmss)
 		advmss = dst->ops->default_advmss(dst);

 	return advmss;
 }

 static inline void dst_metric_set(struct dst_entry *dst, int metric, u32 val)
 {
 	u32 *p = dst_metrics_write_ptr(dst);

 	if (p)
 		p[metric-1] = val;
 }

 static inline u32
 dst_feature(const struct dst_entry *dst, u32 feature)
 {
 	return dst_metric(dst, RTAX_FEATURES) & feature;
 }

 static inline u32 dst_mtu(const struct dst_entry *dst)
 {
 	return dst->ops->mtu(dst);
 }

 /* RTT metrics are stored in milliseconds for user ABI, but used as jiffies */
 static inline unsigned long dst_metric_rtt(const struct dst_entry *dst, int metric)
 {
 	return msecs_to_jiffies(dst_metric(dst, metric));
 }

 static inline u32
 dst_allfrag(const struct dst_entry *dst)
 {
 	int ret = dst_feature(dst,  RTAX_FEATURE_ALLFRAG);
 	return ret;
 }

 static inline int
 dst_metric_locked(const struct dst_entry *dst, int metric)
 {
 	return dst_metric(dst, RTAX_LOCK) & (1<<metric);
 }

 static inline void dst_hold(struct dst_entry *dst)
 {
 	/*
 	 * If your kernel compilation stops here, please check
 	 * __pad_to_align_refcnt declaration in struct dst_entry
 	 */
 	BUILD_BUG_ON(offsetof(struct dst_entry, __refcnt) & 63);
 	atomic_inc(&dst->__refcnt);
 }

 static inline void dst_use(struct dst_entry *dst, unsigned long time)
 {
 	dst_hold(dst);
 	dst->__use++;
 	dst->lastuse = time;
 }

 static inline void dst_use_noref(struct dst_entry *dst, unsigned long time)
 {
 	dst->__use++;
 	dst->lastuse = time;
 }

 static inline struct dst_entry *dst_clone(struct dst_entry *dst)
 {
 	if (dst)
 		atomic_inc(&dst->__refcnt);
 	return dst;
 }

 void dst_release(struct dst_entry *dst);

 static inline void refdst_drop(unsigned long refdst)
 {
 	if (!(refdst & SKB_DST_NOREF))
 		dst_release((struct dst_entry *)(refdst & SKB_DST_PTRMASK));
 }

 /**
  * skb_dst_drop - drops skb dst
  * @skb: buffer
  *
  * Drops dst reference count if a reference was taken.
  */
 static inline void skb_dst_drop(struct sk_buff *skb)
 {
 	if (skb->_skb_refdst) {
 		refdst_drop(skb->_skb_refdst);
 		skb->_skb_refdst = 0UL;
 	}
 }

 static inline void skb_dst_copy(struct sk_buff *nskb, const struct sk_buff *oskb)
 {
 	nskb->_skb_refdst = oskb->_skb_refdst;
 	if (!(nskb->_skb_refdst & SKB_DST_NOREF))
 		dst_clone(skb_dst(nskb));
 }

 /**
  * skb_dst_force - makes sure skb dst is refcounted
  * @skb: buffer
  *
  * If dst is not yet refcounted, let's do it
  */
 static inline void skb_dst_force(struct sk_buff *skb)
 {
 	if (skb_dst_is_noref(skb)) {
 		WARN_ON(!rcu_read_lock_held());
 		skb->_skb_refdst &= ~SKB_DST_NOREF;
 		dst_clone(skb_dst(skb));
 	}
 }


 /**
  *	__skb_tunnel_rx - prepare skb for rx reinsert
  *	@skb: buffer
  *	@dev: tunnel device
  *	@net: netns for packet i/o
  *
  *	After decapsulation, packet is going to re-enter (netif_rx()) our stack,
  *	so make some cleanups. (no accounting done)
  */
 static inline void __skb_tunnel_rx(struct sk_buff *skb, struct net_device *dev,
 				   struct net *net)
 {
 	skb->dev = dev;

 	/*
 	 * Clear hash so that we can recalulate the hash for the
 	 * encapsulated packet, unless we have already determine the hash
 	 * over the L4 4-tuple.
 	 */
 	skb_clear_hash_if_not_l4(skb);
 	skb_set_queue_mapping(skb, 0);
 	skb_scrub_packet(skb, !net_eq(net, dev_net(dev)));
 }

 /**
  *	skb_tunnel_rx - prepare skb for rx reinsert
  *	@skb: buffer
  *	@dev: tunnel device
  *
  *	After decapsulation, packet is going to re-enter (netif_rx()) our stack,
  *	so make some cleanups, and perform accounting.
  *	Note: this accounting is not SMP safe.
  */
 static inline void skb_tunnel_rx(struct sk_buff *skb, struct net_device *dev,
 				 struct net *net)
 {
 	/* TODO : stats should be SMP safe */
 	dev->stats.rx_packets++;
 	dev->stats.rx_bytes += skb->len;
 	__skb_tunnel_rx(skb, dev, net);
 }

 /* Children define the path of the packet through the
  * Linux networking.  Thus, destinations are stackable.
  */

 static inline struct dst_entry *skb_dst_pop(struct sk_buff *skb)
 {
 	struct dst_entry *child = dst_clone(skb_dst(skb)->child);

 	skb_dst_drop(skb);
 	return child;
 }

 int dst_discard(struct sk_buff *skb);
 void *dst_alloc(struct dst_ops *ops, struct net_device *dev, int initial_ref,
 		int initial_obsolete, unsigned short flags);
 void __dst_free(struct dst_entry *dst);
 struct dst_entry *dst_destroy(struct dst_entry *dst);

 static inline void dst_free(struct dst_entry *dst)
 {
 	if (dst->obsolete > 0)
 		return;
 	if (!atomic_read(&dst->__refcnt)) {
 		dst = dst_destroy(dst);
 		if (!dst)
 			return;
 	}
 	__dst_free(dst);
 }

 static inline void dst_rcu_free(struct rcu_head *head)
 {
 	struct dst_entry *dst = container_of(head, struct dst_entry, rcu_head);
 	dst_free(dst);
 }

 static inline void dst_confirm(struct dst_entry *dst)
 {
 	dst->pending_confirm = 1;
 }

 static inline int dst_neigh_output(struct dst_entry *dst, struct neighbour *n,
 				   struct sk_buff *skb)
 {
 	const struct hh_cache *hh;

 	if (dst->pending_confirm) {
 		unsigned long now = jiffies;

 		dst->pending_confirm = 0;
 		/* avoid dirtying neighbour */
 		if (n->confirmed != now)
 			n->confirmed = now;
 	}

 	hh = &n->hh;
 	if ((n->nud_state & NUD_CONNECTED) && hh->hh_len)
 		return neigh_hh_output(hh, skb);
 	else
 		return n->output(n, skb);
 }

 static inline struct neighbour *dst_neigh_lookup(const struct dst_entry *dst, const void *daddr)
 {
 	struct neighbour *n = dst->ops->neigh_lookup(dst, NULL, daddr);
 	return IS_ERR(n) ? NULL : n;
 }

 static inline struct neighbour *dst_neigh_lookup_skb(const struct dst_entry *dst,
 						     struct sk_buff *skb)
 {
 	struct neighbour *n =  dst->ops->neigh_lookup(dst, skb, NULL);
 	return IS_ERR(n) ? NULL : n;
 }

 static inline void dst_link_failure(struct sk_buff *skb)
 {
 	struct dst_entry *dst = skb_dst(skb);
 	if (dst && dst->ops && dst->ops->link_failure)
 		dst->ops->link_failure(skb);
 }

 static inline void dst_set_expires(struct dst_entry *dst, int timeout)
 {
 	unsigned long expires = jiffies + timeout;

 	if (expires == 0)
 		expires = 1;

 	if (dst->expires == 0 || time_before(expires, dst->expires))
 		dst->expires = expires;
 }

 /* Output packet to network from transport.  */
 static inline int dst_output(struct sk_buff *skb)
 {
 	return skb_dst(skb)->output(skb);
 }

 /* Input packet from network to transport.  */
 static inline int dst_input(struct sk_buff *skb)
 {
 	return skb_dst(skb)->input(skb);
 }

 static inline struct dst_entry *dst_check(struct dst_entry *dst, u32 cookie)
 {
 	if (dst->obsolete)
 		dst = dst->ops->check(dst, cookie);
 	return dst;
 }

 void dst_init(void);

 /* Flags for xfrm_lookup flags argument. */
 enum {
 	XFRM_LOOKUP_ICMP = 1 << 0,
 };

 struct flowi;
 #ifndef CONFIG_XFRM
 static inline struct dst_entry *xfrm_lookup(struct net *net,
 					    struct dst_entry *dst_orig,
 					    const struct flowi *fl, struct sock *sk,
 					    int flags)
 {
 	return dst_orig;
 }

 static inline struct xfrm_state *dst_xfrm(const struct dst_entry *dst)
 {
 	return NULL;
 }

 #else
 struct dst_entry *xfrm_lookup(struct net *net, struct dst_entry *dst_orig,
 			      const struct flowi *fl, struct sock *sk,
 			      int flags);

 /* skb attached with this dst needs transformation if dst->xfrm is valid */
 static inline struct xfrm_state *dst_xfrm(const struct dst_entry *dst)
 {
 	return dst->xfrm;
 }
 #endif

 #endif /* _NET_DST_H */
	/*
	* net/dst.h Protocol independent destination cache definitions.
	*
	* Authors: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
	*
	*/

	#ifndef _NET_DST_H
	#define _NET_DST_H

	#include <net/dst_ops.h>
	#include <linux/netdevice.h>
	#include <linux/rtnetlink.h>
	#include <linux/rcupdate.h>
	#include <linux/bug.h>
	#include <linux/jiffies.h>
	#include <net/neighbour.h>
	#include <asm/processor.h>

	#define DST_GC_MIN (HZ/10)
	#define DST_GC_INC (HZ/2)
	#define DST_GC_MAX (120*HZ)

	/* Each dst_entry has reference count and sits in some parent list(s).
	* When it is removed from parent list, it is "freed" (dst_free).
	* After this it enters dead state (dst->obsolete > 0) and if its refcnt
	* is zero, it can be destroyed immediately, otherwise it is added
	* to gc list and garbage collector periodically checks the refcnt.
	*/

	struct sk_buff;

	struct dst_entry {
	struct rcu_head rcu_head;
	struct dst_entry *child;
	struct net_device *dev;
	struct dst_ops *ops;
	unsigned long _metrics;
	unsigned long expires;
	struct dst_entry *path;
	struct dst_entry *from;
	#ifdef CONFIG_XFRM
	struct xfrm_state *xfrm;
	#else
	void *__pad1;
	#endif
	int (input)(struct sk_buff );
	int (output)(struct sk_buff );

	unsigned short flags;
	#define DST_HOST 0x0001
	#define DST_NOXFRM 0x0002
	#define DST_NOPOLICY 0x0004
	#define DST_NOHASH 0x0008
	#define DST_NOCACHE 0x0010
	#define DST_NOCOUNT 0x0020
	#define DST_FAKE_RTABLE 0x0040
	#define DST_XFRM_TUNNEL 0x0080
	#define DST_XFRM_QUEUE 0x0100

	unsigned short pending_confirm;

	short error;

	/* A non-zero value of dst->obsolete forces by-hand validation
	* of the route entry. Positive values are set by the generic
	* dst layer to indicate that the entry has been forcefully
	* destroyed.
	*
	* Negative values are used by the implementation layer code to
	* force invocation of the dst_ops->check() method.
	*/
	short obsolete;
	#define DST_OBSOLETE_NONE 0
	#define DST_OBSOLETE_DEAD 2
	#define DST_OBSOLETE_FORCE_CHK -1
	#define DST_OBSOLETE_KILL -2
	unsigned short header_len; /* more space at head required */
	unsigned short trailer_len; /* space to reserve at tail */
	#ifdef CONFIG_IP_ROUTE_CLASSID
	__u32 tclassid;
	#else
	__u32 __pad2;
	#endif

	/*
	* Align __refcnt to a 64 bytes alignment
	* (L1_CACHE_SIZE would be too much)
	*/
	#ifdef CONFIG_64BIT
	long __pad_to_align_refcnt[2];
	#endif
	/*
	* __refcnt wants to be on a different cache line from
	* input/output/ops or performance tanks badly
	*/
	atomic_t __refcnt; /* client references */
	int __use;
	unsigned long lastuse;
	union {
	struct dst_entry *next;
	struct rtable __rcu *rt_next;
	struct rt6_info *rt6_next;
	struct dn_route __rcu *dn_next;
	};
	};

	u32 dst_cow_metrics_generic(struct dst_entry dst, unsigned long old);
	extern const u32 dst_default_metrics[];

	#define DST_METRICS_READ_ONLY 0x1UL
	#define DST_METRICS_FORCE_OVERWRITE 0x2UL
	#define DST_METRICS_FLAGS 0x3UL
	#define __DST_METRICS_PTR(Y) \
	((u32 *)((Y) & ~DST_METRICS_FLAGS))
	#define DST_METRICS_PTR(X) __DST_METRICS_PTR((X)->_metrics)

	static inline bool dst_metrics_read_only(const struct dst_entry *dst)
	{
	return dst->_metrics & DST_METRICS_READ_ONLY;
	}

	static inline void dst_metrics_set_force_overwrite(struct dst_entry *dst)
	{
	dst->_metrics \|= DST_METRICS_FORCE_OVERWRITE;
	}

	void __dst_destroy_metrics_generic(struct dst_entry *dst, unsigned long old);

	static inline void dst_destroy_metrics_generic(struct dst_entry *dst)
	{
	unsigned long val = dst->_metrics;
	if (!(val & DST_METRICS_READ_ONLY))
	__dst_destroy_metrics_generic(dst, val);
	}

	static inline u32 dst_metrics_write_ptr(struct dst_entry dst)
	{
	unsigned long p = dst->_metrics;

	BUG_ON(!p);

	if (p & DST_METRICS_READ_ONLY)
	return dst->ops->cow_metrics(dst, p);
	return __DST_METRICS_PTR(p);
	}

	/* This may only be invoked before the entry has reached global
	* visibility.
	*/
	static inline void dst_init_metrics(struct dst_entry *dst,
	const u32 *src_metrics,
	bool read_only)
	{
	dst->_metrics = ((unsigned long) src_metrics) \|
	(read_only ? DST_METRICS_READ_ONLY : 0);
	}

	static inline void dst_copy_metrics(struct dst_entry dest, const struct dst_entry src)
	{
	u32 *dst_metrics = dst_metrics_write_ptr(dest);

	if (dst_metrics) {
	u32 *src_metrics = DST_METRICS_PTR(src);

	memcpy(dst_metrics, src_metrics, RTAX_MAX * sizeof(u32));
	}
	}

	static inline u32 dst_metrics_ptr(struct dst_entry dst)
	{
	return DST_METRICS_PTR(dst);
	}

	static inline u32
	dst_metric_raw(const struct dst_entry *dst, const int metric)
	{
	u32 *p = DST_METRICS_PTR(dst);

	return p[metric-1];
	}

	static inline u32
	dst_metric(const struct dst_entry *dst, const int metric)
	{
	WARN_ON_ONCE(metric == RTAX_HOPLIMIT \|\|
	metric == RTAX_ADVMSS \|\|
	metric == RTAX_MTU);
	return dst_metric_raw(dst, metric);
	}

	static inline u32
	dst_metric_advmss(const struct dst_entry *dst)
	{
	u32 advmss = dst_metric_raw(dst, RTAX_ADVMSS);

	if (!advmss)
	advmss = dst->ops->default_advmss(dst);

	return advmss;
	}

	static inline void dst_metric_set(struct dst_entry *dst, int metric, u32 val)
	{
	u32 *p = dst_metrics_write_ptr(dst);

	if (p)
	p[metric-1] = val;
	}

	static inline u32
	dst_feature(const struct dst_entry *dst, u32 feature)
	{
	return dst_metric(dst, RTAX_FEATURES) & feature;
	}

	static inline u32 dst_mtu(const struct dst_entry *dst)
	{
	return dst->ops->mtu(dst);
	}

	/* RTT metrics are stored in milliseconds for user ABI, but used as jiffies */
	static inline unsigned long dst_metric_rtt(const struct dst_entry *dst, int metric)
	{
	return msecs_to_jiffies(dst_metric(dst, metric));
	}

	static inline u32
	dst_allfrag(const struct dst_entry *dst)
	{
	int ret = dst_feature(dst, RTAX_FEATURE_ALLFRAG);
	return ret;
	}

	static inline int
	dst_metric_locked(const struct dst_entry *dst, int metric)
	{
	return dst_metric(dst, RTAX_LOCK) & (1<<metric);
	}

	static inline void dst_hold(struct dst_entry *dst)
	{
	/*
	* If your kernel compilation stops here, please check
	* __pad_to_align_refcnt declaration in struct dst_entry
	*/
	BUILD_BUG_ON(offsetof(struct dst_entry, __refcnt) & 63);
	atomic_inc(&dst->__refcnt);
	}

	static inline void dst_use(struct dst_entry *dst, unsigned long time)
	{
	dst_hold(dst);
	dst->__use++;
	dst->lastuse = time;
	}

	static inline void dst_use_noref(struct dst_entry *dst, unsigned long time)
	{
	dst->__use++;
	dst->lastuse = time;
	}

	static inline struct dst_entry dst_clone(struct dst_entry dst)
	{
	if (dst)
	atomic_inc(&dst->__refcnt);
	return dst;
	}

	void dst_release(struct dst_entry *dst);

	static inline void refdst_drop(unsigned long refdst)
	{
	if (!(refdst & SKB_DST_NOREF))
	dst_release((struct dst_entry *)(refdst & SKB_DST_PTRMASK));
	}

	/**
	* skb_dst_drop - drops skb dst
	* @skb: buffer
	*
	* Drops dst reference count if a reference was taken.
	*/
	static inline void skb_dst_drop(struct sk_buff *skb)
	{
	if (skb->_skb_refdst) {
	refdst_drop(skb->_skb_refdst);
	skb->_skb_refdst = 0UL;
	}
	}

	static inline void skb_dst_copy(struct sk_buff nskb, const struct sk_buff oskb)
	{
	nskb->_skb_refdst = oskb->_skb_refdst;
	if (!(nskb->_skb_refdst & SKB_DST_NOREF))
	dst_clone(skb_dst(nskb));
	}

	/**
	* skb_dst_force - makes sure skb dst is refcounted
	* @skb: buffer
	*
	* If dst is not yet refcounted, let's do it
	*/
	static inline void skb_dst_force(struct sk_buff *skb)
	{
	if (skb_dst_is_noref(skb)) {
	WARN_ON(!rcu_read_lock_held());
	skb->_skb_refdst &= ~SKB_DST_NOREF;
	dst_clone(skb_dst(skb));
	}
	}


	/**
	* __skb_tunnel_rx - prepare skb for rx reinsert
	* @skb: buffer
	* @dev: tunnel device
	* @net: netns for packet i/o
	*
	* After decapsulation, packet is going to re-enter (netif_rx()) our stack,
	* so make some cleanups. (no accounting done)
	*/
	static inline void __skb_tunnel_rx(struct sk_buff skb, struct net_device dev,
	struct net *net)
	{
	skb->dev = dev;

	/*
	* Clear hash so that we can recalulate the hash for the
	* encapsulated packet, unless we have already determine the hash
	* over the L4 4-tuple.
	*/
	skb_clear_hash_if_not_l4(skb);
	skb_set_queue_mapping(skb, 0);
	skb_scrub_packet(skb, !net_eq(net, dev_net(dev)));
	}

	/**
	* skb_tunnel_rx - prepare skb for rx reinsert
	* @skb: buffer
	* @dev: tunnel device
	*
	* After decapsulation, packet is going to re-enter (netif_rx()) our stack,
	* so make some cleanups, and perform accounting.
	* Note: this accounting is not SMP safe.
	*/
	static inline void skb_tunnel_rx(struct sk_buff skb, struct net_device dev,
	struct net *net)
	{
	/* TODO : stats should be SMP safe */
	dev->stats.rx_packets++;
	dev->stats.rx_bytes += skb->len;
	__skb_tunnel_rx(skb, dev, net);
	}

	/* Children define the path of the packet through the
	* Linux networking. Thus, destinations are stackable.
	*/

	static inline struct dst_entry skb_dst_pop(struct sk_buff skb)
	{
	struct dst_entry *child = dst_clone(skb_dst(skb)->child);

	skb_dst_drop(skb);
	return child;
	}

	int dst_discard(struct sk_buff *skb);
	void dst_alloc(struct dst_ops ops, struct net_device *dev, int initial_ref,
	int initial_obsolete, unsigned short flags);
	void __dst_free(struct dst_entry *dst);
	struct dst_entry dst_destroy(struct dst_entry dst);

	static inline void dst_free(struct dst_entry *dst)
	{
	if (dst->obsolete > 0)
	return;
	if (!atomic_read(&dst->__refcnt)) {
	dst = dst_destroy(dst);
	if (!dst)
	return;
	}
	__dst_free(dst);
	}

	static inline void dst_rcu_free(struct rcu_head *head)
	{
	struct dst_entry *dst = container_of(head, struct dst_entry, rcu_head);
	dst_free(dst);
	}

	static inline void dst_confirm(struct dst_entry *dst)
	{
	dst->pending_confirm = 1;
	}

	static inline int dst_neigh_output(struct dst_entry dst, struct neighbour n,
	struct sk_buff *skb)
	{
	const struct hh_cache *hh;

	if (dst->pending_confirm) {
	unsigned long now = jiffies;

	dst->pending_confirm = 0;
	/* avoid dirtying neighbour */
	if (n->confirmed != now)
	n->confirmed = now;
	}

	hh = &n->hh;
	if ((n->nud_state & NUD_CONNECTED) && hh->hh_len)
	return neigh_hh_output(hh, skb);
	else
	return n->output(n, skb);
	}

	static inline struct neighbour dst_neigh_lookup(const struct dst_entry dst, const void *daddr)
	{
	struct neighbour *n = dst->ops->neigh_lookup(dst, NULL, daddr);
	return IS_ERR(n) ? NULL : n;
	}

	static inline struct neighbour dst_neigh_lookup_skb(const struct dst_entry dst,
	struct sk_buff *skb)
	{
	struct neighbour *n = dst->ops->neigh_lookup(dst, skb, NULL);
	return IS_ERR(n) ? NULL : n;
	}

	static inline void dst_link_failure(struct sk_buff *skb)
	{
	struct dst_entry *dst = skb_dst(skb);
	if (dst && dst->ops && dst->ops->link_failure)
	dst->ops->link_failure(skb);
	}

	static inline void dst_set_expires(struct dst_entry *dst, int timeout)
	{
	unsigned long expires = jiffies + timeout;

	if (expires == 0)
	expires = 1;

	if (dst->expires == 0 \|\| time_before(expires, dst->expires))
	dst->expires = expires;
	}

	/* Output packet to network from transport. */
	static inline int dst_output(struct sk_buff *skb)
	{
	return skb_dst(skb)->output(skb);
	}

	/* Input packet from network to transport. */
	static inline int dst_input(struct sk_buff *skb)
	{
	return skb_dst(skb)->input(skb);
	}

	static inline struct dst_entry dst_check(struct dst_entry dst, u32 cookie)
	{
	if (dst->obsolete)
	dst = dst->ops->check(dst, cookie);
	return dst;
	}

	void dst_init(void);

	/* Flags for xfrm_lookup flags argument. */
	enum {
	XFRM_LOOKUP_ICMP = 1 << 0,
	};

	struct flowi;
	#ifndef CONFIG_XFRM
	static inline struct dst_entry xfrm_lookup(struct net net,
	struct dst_entry *dst_orig,
	const struct flowi fl, struct sock sk,
	int flags)
	{
	return dst_orig;
	}

	static inline struct xfrm_state dst_xfrm(const struct dst_entry dst)
	{
	return NULL;
	}

	#else
	struct dst_entry xfrm_lookup(struct net net, struct dst_entry *dst_orig,
	const struct flowi fl, struct sock sk,
	int flags);

	/* skb attached with this dst needs transformation if dst->xfrm is valid */
	static inline struct xfrm_state dst_xfrm(const struct dst_entry dst)
	{
	return dst->xfrm;
	}
	#endif

	#endif /* _NET_DST_H */