| /* |
| * 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/workqueue.h> |
| #include <linux/mm.h> |
| #include <linux/module.h> |
| #include <linux/slab.h> |
| #include <linux/netdevice.h> |
| #include <linux/skbuff.h> |
| #include <linux/string.h> |
| #include <linux/types.h> |
| #include <net/net_namespace.h> |
| #include <linux/sched.h> |
| #include <linux/prefetch.h> |
| |
| #include <net/dst.h> |
| |
| /* |
| * Theory of operations: |
| * 1) We use a list, protected by a spinlock, to add |
| * new entries from both BH and non-BH context. |
| * 2) In order to keep spinlock held for a small delay, |
| * we use a second list where are stored long lived |
| * entries, that are handled by the garbage collect thread |
| * fired by a workqueue. |
| * 3) This list is guarded by a mutex, |
| * so that the gc_task and dst_dev_event() can be synchronized. |
| */ |
| |
| /* |
| * We want to keep lock & list close together |
| * to dirty as few cache lines as possible in __dst_free(). |
| * As this is not a very strong hint, we dont force an alignment on SMP. |
| */ |
| static struct { |
| spinlock_t lock; |
| struct dst_entry *list; |
| unsigned long timer_inc; |
| unsigned long timer_expires; |
| } dst_garbage = { |
| .lock = __SPIN_LOCK_UNLOCKED(dst_garbage.lock), |
| .timer_inc = DST_GC_MAX, |
| }; |
| static void dst_gc_task(struct work_struct *work); |
| static void ___dst_free(struct dst_entry *dst); |
| |
| static DECLARE_DELAYED_WORK(dst_gc_work, dst_gc_task); |
| |
| static DEFINE_MUTEX(dst_gc_mutex); |
| /* |
| * long lived entries are maintained in this list, guarded by dst_gc_mutex |
| */ |
| static struct dst_entry *dst_busy_list; |
| |
| static void dst_gc_task(struct work_struct *work) |
| { |
| int delayed = 0; |
| int work_performed = 0; |
| unsigned long expires = ~0L; |
| struct dst_entry *dst, *next, head; |
| struct dst_entry *last = &head; |
| |
| mutex_lock(&dst_gc_mutex); |
| next = dst_busy_list; |
| |
| loop: |
| while ((dst = next) != NULL) { |
| next = dst->next; |
| prefetch(&next->next); |
| cond_resched(); |
| if (likely(atomic_read(&dst->__refcnt))) { |
| last->next = dst; |
| last = dst; |
| delayed++; |
| continue; |
| } |
| work_performed++; |
| |
| 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 > 0) |
| continue; |
| |
| ___dst_free(dst); |
| dst->next = next; |
| next = dst; |
| } |
| } |
| |
| spin_lock_bh(&dst_garbage.lock); |
| next = dst_garbage.list; |
| if (next) { |
| dst_garbage.list = NULL; |
| spin_unlock_bh(&dst_garbage.lock); |
| goto loop; |
| } |
| last->next = NULL; |
| dst_busy_list = head.next; |
| if (!dst_busy_list) |
| dst_garbage.timer_inc = DST_GC_MAX; |
| else { |
| /* |
| * if we freed less than 1/10 of delayed entries, |
| * we can sleep longer. |
| */ |
| if (work_performed <= delayed/10) { |
| dst_garbage.timer_expires += dst_garbage.timer_inc; |
| if (dst_garbage.timer_expires > DST_GC_MAX) |
| dst_garbage.timer_expires = DST_GC_MAX; |
| dst_garbage.timer_inc += DST_GC_INC; |
| } else { |
| dst_garbage.timer_inc = DST_GC_INC; |
| dst_garbage.timer_expires = DST_GC_MIN; |
| } |
| expires = dst_garbage.timer_expires; |
| /* |
| * if the next desired timer is more than 4 seconds in the |
| * future then round the timer to whole seconds |
| */ |
| if (expires > 4*HZ) |
| expires = round_jiffies_relative(expires); |
| schedule_delayed_work(&dst_gc_work, expires); |
| } |
| |
| spin_unlock_bh(&dst_garbage.lock); |
| mutex_unlock(&dst_gc_mutex); |
| } |
| |
| int dst_discard(struct sk_buff *skb) |
| { |
| kfree_skb(skb); |
| return 0; |
| } |
| EXPORT_SYMBOL(dst_discard); |
| |
| const u32 dst_default_metrics[RTAX_MAX]; |
| |
| void *dst_alloc(struct dst_ops *ops, struct net_device *dev, |
| int initial_ref, int initial_obsolete, unsigned short flags) |
| { |
| struct dst_entry *dst; |
| |
| if (ops->gc && dst_entries_get_fast(ops) > ops->gc_thresh) { |
| if (ops->gc(ops)) |
| return NULL; |
| } |
| dst = kmem_cache_alloc(ops->kmem_cachep, GFP_ATOMIC); |
| if (!dst) |
| return NULL; |
| dst->child = NULL; |
| dst->dev = dev; |
| if (dev) |
| dev_hold(dev); |
| dst->ops = ops; |
| dst_init_metrics(dst, dst_default_metrics, true); |
| dst->expires = 0UL; |
| dst->path = dst; |
| #ifdef CONFIG_XFRM |
| dst->xfrm = NULL; |
| #endif |
| dst->input = dst_discard; |
| dst->output = dst_discard; |
| dst->error = 0; |
| dst->obsolete = initial_obsolete; |
| dst->header_len = 0; |
| dst->trailer_len = 0; |
| #ifdef CONFIG_IP_ROUTE_CLASSID |
| dst->tclassid = 0; |
| #endif |
| atomic_set(&dst->__refcnt, initial_ref); |
| dst->__use = 0; |
| dst->lastuse = jiffies; |
| dst->flags = flags; |
| dst->pending_confirm = 0; |
| dst->next = NULL; |
| if (!(flags & DST_NOCOUNT)) |
| dst_entries_add(ops, 1); |
| return dst; |
| } |
| EXPORT_SYMBOL(dst_alloc); |
| |
| 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->output = dst_discard; |
| dst->obsolete = DST_OBSOLETE_DEAD; |
| } |
| |
| void __dst_free(struct dst_entry *dst) |
| { |
| spin_lock_bh(&dst_garbage.lock); |
| ___dst_free(dst); |
| dst->next = dst_garbage.list; |
| dst_garbage.list = dst; |
| if (dst_garbage.timer_inc > DST_GC_INC) { |
| dst_garbage.timer_inc = DST_GC_INC; |
| dst_garbage.timer_expires = DST_GC_MIN; |
| cancel_delayed_work(&dst_gc_work); |
| schedule_delayed_work(&dst_gc_work, dst_garbage.timer_expires); |
| } |
| spin_unlock_bh(&dst_garbage.lock); |
| } |
| EXPORT_SYMBOL(__dst_free); |
| |
| struct dst_entry *dst_destroy(struct dst_entry * dst) |
| { |
| struct dst_entry *child; |
| |
| smp_rmb(); |
| |
| again: |
| child = dst->child; |
| |
| if (!(dst->flags & DST_NOCOUNT)) |
| dst_entries_add(dst->ops, -1); |
| |
| if (dst->ops->destroy) |
| dst->ops->destroy(dst); |
| if (dst->dev) |
| dev_put(dst->dev); |
| 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; |
| } |
| EXPORT_SYMBOL(dst_destroy); |
| |
| static void dst_rcu_destroy(struct rcu_head *head) |
| { |
| struct dst_entry *dst = container_of(head, struct dst_entry, rcu_head); |
| |
| dst = dst_destroy(dst); |
| if (dst) |
| __dst_free(dst); |
| } |
| |
| void dst_release(struct dst_entry *dst) |
| { |
| if (dst) { |
| int newrefcnt; |
| |
| newrefcnt = atomic_dec_return(&dst->__refcnt); |
| WARN_ON(newrefcnt < 0); |
| if (unlikely(dst->flags & (DST_NOCACHE | DST_RCU_FREE)) && !newrefcnt) { |
| if (dst->flags & DST_RCU_FREE) { |
| call_rcu_bh(&dst->rcu_head, dst_rcu_destroy); |
| } else { |
| dst = dst_destroy(dst); |
| if (dst) |
| __dst_free(dst); |
| } |
| } |
| } |
| } |
| EXPORT_SYMBOL(dst_release); |
| |
| u32 *dst_cow_metrics_generic(struct dst_entry *dst, unsigned long old) |
| { |
| u32 *p = kmalloc(sizeof(u32) * RTAX_MAX, GFP_ATOMIC); |
| |
| if (p) { |
| u32 *old_p = __DST_METRICS_PTR(old); |
| unsigned long prev, new; |
| |
| memcpy(p, old_p, sizeof(u32) * RTAX_MAX); |
| |
| new = (unsigned long) p; |
| prev = cmpxchg(&dst->_metrics, old, new); |
| |
| if (prev != old) { |
| kfree(p); |
| p = __DST_METRICS_PTR(prev); |
| if (prev & DST_METRICS_READ_ONLY) |
| p = NULL; |
| } |
| } |
| return p; |
| } |
| EXPORT_SYMBOL(dst_cow_metrics_generic); |
| |
| /* Caller asserts that dst_metrics_read_only(dst) is false. */ |
| void __dst_destroy_metrics_generic(struct dst_entry *dst, unsigned long old) |
| { |
| unsigned long prev, new; |
| |
| new = ((unsigned long) dst_default_metrics) | DST_METRICS_READ_ONLY; |
| prev = cmpxchg(&dst->_metrics, old, new); |
| if (prev == old) |
| kfree(__DST_METRICS_PTR(old)); |
| } |
| EXPORT_SYMBOL(__dst_destroy_metrics_generic); |
| |
| /** |
| * skb_dst_set_noref - sets skb dst, without a reference |
| * @skb: buffer |
| * @dst: dst entry |
| * |
| * Sets skb dst, assuming a reference was not taken on dst |
| * skb_dst_drop() should not dst_release() this dst |
| */ |
| void skb_dst_set_noref(struct sk_buff *skb, struct dst_entry *dst) |
| { |
| bool hold; |
| |
| WARN_ON(!rcu_read_lock_held() && !rcu_read_lock_bh_held()); |
| /* If dst not in cache, we must take a reference, because |
| * dst_release() will destroy dst as soon as its refcount becomes zero |
| */ |
| hold = (dst->flags & (DST_NOCACHE | DST_RCU_FREE)) == DST_NOCACHE; |
| if (unlikely(hold)) { |
| dst_hold(dst); |
| skb_dst_set(skb, dst); |
| } else { |
| skb->_skb_refdst = (unsigned long)dst | SKB_DST_NOREF; |
| } |
| } |
| EXPORT_SYMBOL(skb_dst_set_noref); |
| |
| /* 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 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->output = dst_discard; |
| } else { |
| dst->dev = dev_net(dst->dev)->loopback_dev; |
| dev_hold(dst->dev); |
| dev_put(dev); |
| } |
| } |
| |
| static int dst_dev_event(struct notifier_block *this, unsigned long event, |
| void *ptr) |
| { |
| struct net_device *dev = ptr; |
| struct dst_entry *dst, *last = NULL; |
| |
| switch (event) { |
| case NETDEV_UNREGISTER: |
| case NETDEV_DOWN: |
| mutex_lock(&dst_gc_mutex); |
| for (dst = dst_busy_list; dst; dst = dst->next) { |
| last = dst; |
| dst_ifdown(dst, dev, event != NETDEV_DOWN); |
| } |
| |
| spin_lock_bh(&dst_garbage.lock); |
| dst = dst_garbage.list; |
| dst_garbage.list = NULL; |
| spin_unlock_bh(&dst_garbage.lock); |
| |
| if (last) |
| last->next = dst; |
| else |
| dst_busy_list = dst; |
| for (; dst; dst = dst->next) |
| dst_ifdown(dst, dev, event != NETDEV_DOWN); |
| mutex_unlock(&dst_gc_mutex); |
| break; |
| } |
| return NOTIFY_DONE; |
| } |
| |
| static struct notifier_block dst_dev_notifier = { |
| .notifier_call = dst_dev_event, |
| .priority = -10, /* must be called after other network notifiers */ |
| }; |
| |
| void __init dst_init(void) |
| { |
| register_netdevice_notifier(&dst_dev_notifier); |
| } |