/*
 * 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;
        struct xfrm_state       *xfrm;

        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;
#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);
        int                     entry_size;

        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)
{
        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 dst_entry **dst_p, struct flowi *fl,
                       struct sock *sk, int flags)
{
        return 0;
} 
static inline int __xfrm_lookup(struct dst_entry **dst_p, struct flowi *fl,
                                struct sock *sk, int flags)
{
        return 0;
}
#else
extern int xfrm_lookup(struct dst_entry **dst_p, struct flowi *fl,
                       struct sock *sk, int flags);
extern int __xfrm_lookup(struct dst_entry **dst_p, struct flowi *fl,
                         struct sock *sk, int flags);
#endif
#endif

#endif /* _NET_DST_H */