/*
   * 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 <linux/netdevice.h>

  #include <linux/rtnetlink.h>
  #include <linux/rcupdate.h>
  #include <linux/jiffies.h>
  #include <net/neighbour.h>
  #include <asm/processor.h>
  
  /*
   * 0 - no debugging messages
   * 1 - rare events and bugs (default)
   * 2 - trace mode.
   */
  #define RT_CACHE_DEBUG		0
  
  #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;

  	short			error;
  	short			obsolete;

  	int			flags;
  #define DST_HOST		1
  #define DST_NOXFRM		2
  #define DST_NOPOLICY		4
  #define DST_NOHASH		8

  	unsigned long		expires;
  
  	unsigned short		header_len;	/* more space at head required */
  	unsigned short		trailer_len;	/* space to reserve at tail */

  	unsigned int		rate_tokens;

  	unsigned long		rate_last;	/* rate limiting for ICMP */

  	struct dst_entry	*path;

  	struct neighbour	*neighbour;
  	struct hh_cache		*hh;

  #ifdef CONFIG_XFRM

  	struct xfrm_state	*xfrm;

  #else
  	void			*__pad1;

  #endif

  	int			(*input)(struct sk_buff*);
  	int			(*output)(struct sk_buff*);

  	struct  dst_ops	        *ops;

  
  	u32			metrics[RTAX_MAX];
  
  #ifdef CONFIG_NET_CLS_ROUTE
  	__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];
  #else
  	long			__pad_to_align_refcnt[1];
  #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    *rt_next;
  		struct rt6_info   *rt6_next;
  		struct dn_route  *dn_next;
  	};

  };
  
  
  struct dst_ops
  {
  	unsigned short		family;

  	__be16			protocol;

  	unsigned		gc_thresh;

  	int			(*gc)(struct dst_ops *ops);

  	struct dst_entry *	(*check)(struct dst_entry *, __u32 cookie);
  	void			(*destroy)(struct dst_entry *);
  	void			(*ifdown)(struct dst_entry *,
  					  struct net_device *dev, int how);
  	struct dst_entry *	(*negative_advice)(struct dst_entry *);
  	void			(*link_failure)(struct sk_buff *);
  	void			(*update_pmtu)(struct dst_entry *dst, u32 mtu);

  	int			(*local_out)(struct sk_buff *skb);

  
  	atomic_t		entries;

  	struct kmem_cache 		*kmem_cachep;

  	struct net              *dst_net;

  };
  
  #ifdef __KERNEL__
  
  static inline u32
  dst_metric(const struct dst_entry *dst, int metric)
  {
  	return dst->metrics[metric-1];
  }
  
  static inline u32 dst_mtu(const struct dst_entry *dst)
  {
  	u32 mtu = dst_metric(dst, RTAX_MTU);
  	/*
  	 * Alexey put it here, so ask him about it :)
  	 */
  	barrier();
  	return mtu;
  }

  /* 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 void set_dst_metric_rtt(struct dst_entry *dst, int metric,
  				      unsigned long rtt)
  {
  	dst->metrics[metric-1] = jiffies_to_msecs(rtt);
  }

  static inline u32
  dst_allfrag(const struct dst_entry *dst)
  {
  	int ret = dst_metric(dst, RTAX_FEATURES) & RTAX_FEATURE_ALLFRAG;
  	/* Yes, _exactly_. This is paranoia. */
  	barrier();
  	return ret;
  }
  
  static inline int
  dst_metric_locked(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
  struct dst_entry * dst_clone(struct dst_entry * dst)
  {
  	if (dst)
  		atomic_inc(&dst->__refcnt);
  	return dst;
  }

  extern void dst_release(struct dst_entry *dst);

  
  /* Children define the path of the packet through the
   * Linux networking.  Thus, destinations are stackable.
   */
  
  static inline struct dst_entry *dst_pop(struct dst_entry *dst)
  {
  	struct dst_entry *child = dst_clone(dst->child);
  
  	dst_release(dst);
  	return child;
  }

  extern int dst_discard(struct sk_buff *skb);

  extern void * dst_alloc(struct dst_ops * ops);
  extern void __dst_free(struct dst_entry * dst);
  extern struct dst_entry *dst_destroy(struct dst_entry * dst);
  
  static inline void dst_free(struct dst_entry * dst)
  {
  	if (dst->obsolete > 1)
  		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)
  {
  	if (dst)
  		neigh_confirm(dst->neighbour);
  }
  
  static inline void dst_negative_advice(struct dst_entry **dst_p)
  {
  	struct dst_entry * dst = *dst_p;
  	if (dst && dst->ops->negative_advice)
  		*dst_p = dst->ops->negative_advice(dst);
  }
  
  static inline void dst_link_failure(struct sk_buff *skb)
  {
  	struct dst_entry * dst = skb->dst;
  	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->output(skb);

  }
  
  /* Input packet from network to transport.  */
  static inline int dst_input(struct sk_buff *skb)
  {

  	return skb->dst->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;
  }
  
  extern void		dst_init(void);

  /* Flags for xfrm_lookup flags argument. */
  enum {
  	XFRM_LOOKUP_WAIT = 1 << 0,

  	XFRM_LOOKUP_ICMP = 1 << 1,

  };

  struct flowi;
  #ifndef CONFIG_XFRM

  static inline int xfrm_lookup(struct net *net, struct dst_entry **dst_p,
  			      struct flowi *fl, struct sock *sk, int flags)

  {
  	return 0;
  } 

  static inline int __xfrm_lookup(struct net *net, struct dst_entry **dst_p,
  				struct flowi *fl, struct sock *sk, int flags)

  {
  	return 0;
  }

  #else

  extern int xfrm_lookup(struct net *net, struct dst_entry **dst_p,
  		       struct flowi *fl, struct sock *sk, int flags);
  extern int __xfrm_lookup(struct net *net, struct dst_entry **dst_p,
  			 struct flowi *fl, struct sock *sk, int flags);

  #endif
  #endif
  
  #endif /* _NET_DST_H */