/* * net/core/dst.c	Protocol independent destination cache. * * Authors:		Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru> * */ #include <linux/bitops.h>#include <linux/errno.h>#include <linux/init.h>#include <linux/kernel.h>#include <linux/mm.h>#include <linux/module.h>#include <linux/netdevice.h>#include <linux/sched.h>#include <linux/skbuff.h>#include <linux/string.h>#include <linux/types.h> #include <net/dst.h> /* Locking strategy: * 1) Garbage collection state of dead destination cache *    entries is protected by dst_lock. * 2) GC is run only from BH context, and is the only remover *    of entries. * 3) Entries are added to the garbage list from both BH *    and non-BH context, so local BH disabling is needed. * 4) All operations modify state, so a spinlock is used. */static struct dst_entry 	*dst_garbage_list;#if RT_CACHE_DEBUG >= 2 static atomic_t			 dst_total = ATOMIC_INIT(0);#endifstatic DEFINE_SPINLOCK(dst_lock); static unsigned long dst_gc_timer_expires;static unsigned long dst_gc_timer_inc = DST_GC_MAX;static void dst_run_gc(unsigned long);static void ___dst_free(struct dst_entry * dst); static DEFINE_TIMER(dst_gc_timer, dst_run_gc, DST_GC_MIN, 0); static void dst_run_gc(unsigned long dummy){	int    delayed = 0;	int    work_performed;	struct dst_entry * dst, **dstp; 	if (!spin_trylock(&dst_lock)) {		mod_timer(&dst_gc_timer, jiffies + HZ/10);		return;	} 	del_timer(&dst_gc_timer);	dstp = &dst_garbage_list;	work_performed = 0;	while ((dst = *dstp) != NULL) {		if (atomic_read(&dst->__refcnt)) {			dstp = &dst->next;			delayed++;			continue;		}		*dstp = dst->next;		work_performed = 1; 		dst = dst_destroy(dst);		if (dst) {			/* NOHASH and still referenced. Unless it is already			 * on gc list, invalidate it and add to gc list.			 *			 * Note: this is temporary. Actually, NOHASH dst's			 * must be obsoleted when parent is obsoleted.			 * But we do not have state "obsoleted, but			 * referenced by parent", so it is right.			 */			if (dst->obsolete > 1)				continue; 			___dst_free(dst);			dst->next = *dstp;			*dstp = dst;			dstp = &dst->next;		}	}	if (!dst_garbage_list) {		dst_gc_timer_inc = DST_GC_MAX;		goto out;	}	if (!work_performed) {		if ((dst_gc_timer_expires += dst_gc_timer_inc) > DST_GC_MAX)			dst_gc_timer_expires = DST_GC_MAX;		dst_gc_timer_inc += DST_GC_INC;	} else {		dst_gc_timer_inc = DST_GC_INC;		dst_gc_timer_expires = DST_GC_MIN;	}	dst_gc_timer.expires = jiffies + dst_gc_timer_expires;#if RT_CACHE_DEBUG >= 2	printk("dst_total: %d/%d %ld\n",	       atomic_read(&dst_total), delayed,  dst_gc_timer_expires);#endif	add_timer(&dst_gc_timer); out:	spin_unlock(&dst_lock);} static int dst_discard_in(struct sk_buff *skb){	kfree_skb(skb);	return 0;} static int dst_discard_out(struct sk_buff *skb){	kfree_skb(skb);	return 0;} void * dst_alloc(struct dst_ops * ops){	struct dst_entry * dst; 	if (ops->gc && atomic_read(&ops->entries) > ops->gc_thresh) {		if (ops->gc())			return NULL;	}	dst = kmem_cache_alloc(ops->kmem_cachep, SLAB_ATOMIC);	if (!dst)		return NULL;	memset(dst, 0, ops->entry_size);	atomic_set(&dst->__refcnt, 0);	dst->ops = ops;	dst->lastuse = jiffies;	dst->path = dst;	dst->input = dst_discard_in;	dst->output = dst_discard_out;#if RT_CACHE_DEBUG >= 2 	atomic_inc(&dst_total);#endif	atomic_inc(&ops->entries);	return dst;} static void ___dst_free(struct dst_entry * dst){	/* The first case (dev==NULL) is required, when	   protocol module is unloaded.	 */	if (dst->dev == NULL || !(dst->dev->flags&IFF_UP)) {		dst->input = dst_discard_in;		dst->output = dst_discard_out;	}	dst->obsolete = 2;} void __dst_free(struct dst_entry * dst){	spin_lock_bh(&dst_lock);	___dst_free(dst);	dst->next = dst_garbage_list;	dst_garbage_list = dst;	if (dst_gc_timer_inc > DST_GC_INC) {		dst_gc_timer_inc = DST_GC_INC;		dst_gc_timer_expires = DST_GC_MIN;		mod_timer(&dst_gc_timer, jiffies + dst_gc_timer_expires);	}	spin_unlock_bh(&dst_lock);} struct dst_entry *dst_destroy(struct dst_entry * dst){	struct dst_entry *child;	struct neighbour *neigh;	struct hh_cache *hh; 	smp_rmb(); again:	neigh = dst->neighbour;	hh = dst->hh;	child = dst->child; 	dst->hh = NULL;	if (hh && atomic_dec_and_test(&hh->hh_refcnt))		kfree(hh); 	if (neigh) {		dst->neighbour = NULL;		neigh_release(neigh);	} 	atomic_dec(&dst->ops->entries); 	if (dst->ops->destroy)		dst->ops->destroy(dst);	if (dst->dev)		dev_put(dst->dev);#if RT_CACHE_DEBUG >= 2 	atomic_dec(&dst_total);#endif	kmem_cache_free(dst->ops->kmem_cachep, dst); 	dst = child;	if (dst) {		int nohash = dst->flags & DST_NOHASH; 		if (atomic_dec_and_test(&dst->__refcnt)) {			/* We were real parent of this dst, so kill child. */			if (nohash)				goto again;		} else {			/* Child is still referenced, return it for freeing. */			if (nohash)				return dst;			/* Child is still in his hash table */		}	}	return NULL;} /* Dirty hack. We did it in 2.2 (in __dst_free), * we have _very_ good reasons not to repeat * this mistake in 2.3, but we have no choice * now. _It_ _is_ _explicit_ _deliberate_ * _race_ _condition_. * * Commented and originally written by Alexey. */static inline void dst_ifdown(struct dst_entry *dst, struct net_device *dev,			      int unregister){	if (dst->ops->ifdown)		dst->ops->ifdown(dst, dev, unregister); 	if (dev != dst->dev)		return; 	if (!unregister) {		dst->input = dst_discard_in;		dst->output = dst_discard_out;	} else {		dst->dev = &loopback_dev;		dev_hold(&loopback_dev);		dev_put(dev);		if (dst->neighbour && dst->neighbour->dev == dev) {			dst->neighbour->dev = &loopback_dev;			dev_put(dev);			dev_hold(&loopback_dev);		}	}} static int dst_dev_event(struct notifier_block *this, unsigned long event, void *ptr){	struct net_device *dev = ptr;	struct dst_entry *dst; 	switch (event) {	case NETDEV_UNREGISTER:	case NETDEV_DOWN:		spin_lock_bh(&dst_lock);		for (dst = dst_garbage_list; dst; dst = dst->next) {			dst_ifdown(dst, dev, event != NETDEV_DOWN);		}		spin_unlock_bh(&dst_lock);		break;	}	return NOTIFY_DONE;} static struct notifier_block dst_dev_notifier = {	.notifier_call	= dst_dev_event,}; void __init dst_init(void){	register_netdevice_notifier(&dst_dev_notifier);} EXPORT_SYMBOL(__dst_free);EXPORT_SYMBOL(dst_alloc);EXPORT_SYMBOL(dst_destroy);