/* * net/dst.c Protocol independent destination cache. * * Authors: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru> * */ #include <asm/system.h> #include <asm/bitops.h> #include <linux/types.h> #include <linux/kernel.h> #include <linux/sched.h> #include <linux/mm.h> #include <linux/string.h> #include <linux/errno.h> #include <linux/netdevice.h> #include <linux/skbuff.h> #include <linux/init.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; static atomic_t dst_total = ATOMIC_INIT(0); static spinlock_t dst_lock = SPIN_LOCK_UNLOCKED; 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 struct timer_list dst_gc_timer = { data: DST_GC_MIN, function: dst_run_gc }; 43 static void dst_run_gc(unsigned long dummy) { int delayed = 0; struct dst_entry * dst, **dstp; 48 if (!spin_trylock(&dst_lock)) { mod_timer(&dst_gc_timer, jiffies + HZ/10); 50 return; } del_timer(&dst_gc_timer); dstp = &dst_garbage_list; 56 while ((dst = *dstp) != NULL) { 57 if (atomic_read(&dst->__refcnt)) { dstp = &dst->next; delayed++; 60 continue; } *dstp = dst->next; dst_destroy(dst); } 65 if (!dst_garbage_list) { dst_gc_timer_inc = DST_GC_MAX; 67 goto out; } 69 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; 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: 80 spin_unlock(&dst_lock); } 83 static int dst_discard(struct sk_buff *skb) { kfree_skb(skb); 86 return 0; } 89 static int dst_blackhole(struct sk_buff *skb) { kfree_skb(skb); 92 return 0; } 95 void * dst_alloc(struct dst_ops * ops) { struct dst_entry * dst; 99 if (ops->gc && atomic_read(&ops->entries) > ops->gc_thresh) { 100 if (ops->gc()) 101 return NULL; } dst = kmem_cache_alloc(ops->kmem_cachep, SLAB_ATOMIC); 104 if (!dst) 105 return NULL; memset(dst, 0, ops->entry_size); dst->ops = ops; dst->lastuse = jiffies; dst->input = dst_discard; dst->output = dst_blackhole; atomic_inc(&dst_total); atomic_inc(&ops->entries); 113 return dst; } 116 void __dst_free(struct dst_entry * dst) { 118 spin_lock_bh(&dst_lock); /* The first case (dev==NULL) is required, when protocol module is unloaded. */ 123 if (dst->dev == NULL || !(dst->dev->flags&IFF_UP)) { dst->input = dst_discard; dst->output = dst_blackhole; } dst->obsolete = 2; dst->next = dst_garbage_list; dst_garbage_list = dst; 130 if (dst_gc_timer_inc > DST_GC_INC) { del_timer(&dst_gc_timer); dst_gc_timer_inc = DST_GC_INC; dst_gc_timer_expires = DST_GC_MIN; dst_gc_timer.expires = jiffies + dst_gc_timer_expires; add_timer(&dst_gc_timer); } 138 spin_unlock_bh(&dst_lock); } 141 void dst_destroy(struct dst_entry * dst) { struct neighbour *neigh = dst->neighbour; struct hh_cache *hh = dst->hh; dst->hh = NULL; 147 if (hh && atomic_dec_and_test(&hh->hh_refcnt)) kfree(hh); 150 if (neigh) { dst->neighbour = NULL; neigh_release(neigh); } atomic_dec(&dst->ops->entries); 157 if (dst->ops->destroy) dst->ops->destroy(dst); 159 if (dst->dev) dev_put(dst->dev); atomic_dec(&dst_total); kmem_cache_free(dst->ops->kmem_cachep, dst); } 165 static int dst_dev_event(struct notifier_block *this, unsigned long event, void *ptr) { struct net_device *dev = ptr; struct dst_entry *dst; 170 switch (event) { 171 case NETDEV_UNREGISTER: 172 case NETDEV_DOWN: 173 spin_lock_bh(&dst_lock); 174 for (dst = dst_garbage_list; dst; dst = dst->next) { 175 if (dst->dev == dev) { /* 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_. */ if (event!=NETDEV_DOWN && !(dev->features & NETIF_F_DYNALLOC) && 184 dst->output == dst_blackhole) { dst->dev = &loopback_dev; dev_put(dev); dev_hold(&loopback_dev); dst->output = dst_discard; 189 if (dst->neighbour && dst->neighbour->dev == dev) { dst->neighbour->dev = &loopback_dev; dev_put(dev); dev_hold(&loopback_dev); } 194 } else { dst->input = dst_discard; dst->output = dst_blackhole; } } } 200 spin_unlock_bh(&dst_lock); 201 break; } 203 return NOTIFY_DONE; } struct notifier_block dst_dev_notifier = { dst_dev_event, NULL, 0 }; 212 void __init dst_init(void) { register_netdevice_notifier(&dst_dev_notifier); }