1 files changed, 426 insertions, 0 deletions

diff --git a/net/core/dst.c b/net/core/dst.c
new file mode 100644
index 00000000..8246d47a
--- /dev/null
+++ b/net/core/dst.c
@@ -0,0 +1,426 @@
+/*
+ * 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 > 1)
+				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, int 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;
+	RCU_INIT_POINTER(dst->_neighbour, NULL);
+	dst->hh = NULL;
+#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->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 = 2;
+}
+
+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;
+	struct neighbour *neigh;
+	struct hh_cache *hh;
+
+	smp_rmb();
+
+again:
+	neigh = rcu_dereference_protected(dst->_neighbour, 1);
+	hh = dst->hh;
+	child = dst->child;
+
+	dst->hh = NULL;
+	if (hh)
+		hh_cache_put(hh);
+
+	if (neigh) {
+		RCU_INIT_POINTER(dst->_neighbour, NULL);
+		neigh_release(neigh);
+	}
+
+	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);
+
+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) && !newrefcnt) {
+			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)
+{
+	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
+	 */
+	if (unlikely(dst->flags & DST_NOCACHE)) {
+		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 {
+		struct neighbour *neigh;
+
+		dst->dev = dev_net(dst->dev)->loopback_dev;
+		dev_hold(dst->dev);
+		dev_put(dev);
+		rcu_read_lock();
+		neigh = dst_get_neighbour(dst);
+		if (neigh && neigh->dev == dev) {
+			neigh->dev = dst->dev;
+			dev_hold(dst->dev);
+			dev_put(dev);
+		}
+		rcu_read_unlock();
+	}
+}
+
+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);
+}