2 * net/core/dst.c Protocol independent destination cache.
4 * Authors: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
8 #include <linux/bitops.h>
9 #include <linux/errno.h>
10 #include <linux/init.h>
11 #include <linux/kernel.h>
12 #include <linux/workqueue.h>
14 #include <linux/module.h>
15 #include <linux/slab.h>
16 #include <linux/netdevice.h>
17 #include <linux/skbuff.h>
18 #include <linux/string.h>
19 #include <linux/types.h>
20 #include <net/net_namespace.h>
21 #include <linux/sched.h>
22 #include <linux/prefetch.h>
27 * Theory of operations:
28 * 1) We use a list, protected by a spinlock, to add
29 * new entries from both BH and non-BH context.
30 * 2) In order to keep spinlock held for a small delay,
31 * we use a second list where are stored long lived
32 * entries, that are handled by the garbage collect thread
33 * fired by a workqueue.
34 * 3) This list is guarded by a mutex,
35 * so that the gc_task and dst_dev_event() can be synchronized.
39 * We want to keep lock & list close together
40 * to dirty as few cache lines as possible in __dst_free().
41 * As this is not a very strong hint, we dont force an alignment on SMP.
45 struct dst_entry
*list
;
46 unsigned long timer_inc
;
47 unsigned long timer_expires
;
49 .lock
= __SPIN_LOCK_UNLOCKED(dst_garbage
.lock
),
50 .timer_inc
= DST_GC_MAX
,
52 static void dst_gc_task(struct work_struct
*work
);
53 static void ___dst_free(struct dst_entry
*dst
);
55 static DECLARE_DELAYED_WORK(dst_gc_work
, dst_gc_task
);
57 static DEFINE_MUTEX(dst_gc_mutex
);
59 * long lived entries are maintained in this list, guarded by dst_gc_mutex
61 static struct dst_entry
*dst_busy_list
;
63 static void dst_gc_task(struct work_struct
*work
)
66 int work_performed
= 0;
67 unsigned long expires
= ~0L;
68 struct dst_entry
*dst
, *next
, head
;
69 struct dst_entry
*last
= &head
;
71 mutex_lock(&dst_gc_mutex
);
75 while ((dst
= next
) != NULL
) {
77 prefetch(&next
->next
);
79 if (likely(atomic_read(&dst
->__refcnt
))) {
87 dst
= dst_destroy(dst
);
89 /* NOHASH and still referenced. Unless it is already
90 * on gc list, invalidate it and add to gc list.
92 * Note: this is temporary. Actually, NOHASH dst's
93 * must be obsoleted when parent is obsoleted.
94 * But we do not have state "obsoleted, but
95 * referenced by parent", so it is right.
97 if (dst
->obsolete
> 1)
106 spin_lock_bh(&dst_garbage
.lock
);
107 next
= dst_garbage
.list
;
109 dst_garbage
.list
= NULL
;
110 spin_unlock_bh(&dst_garbage
.lock
);
114 dst_busy_list
= head
.next
;
116 dst_garbage
.timer_inc
= DST_GC_MAX
;
119 * if we freed less than 1/10 of delayed entries,
120 * we can sleep longer.
122 if (work_performed
<= delayed
/10) {
123 dst_garbage
.timer_expires
+= dst_garbage
.timer_inc
;
124 if (dst_garbage
.timer_expires
> DST_GC_MAX
)
125 dst_garbage
.timer_expires
= DST_GC_MAX
;
126 dst_garbage
.timer_inc
+= DST_GC_INC
;
128 dst_garbage
.timer_inc
= DST_GC_INC
;
129 dst_garbage
.timer_expires
= DST_GC_MIN
;
131 expires
= dst_garbage
.timer_expires
;
133 * if the next desired timer is more than 4 seconds in the
134 * future then round the timer to whole seconds
137 expires
= round_jiffies_relative(expires
);
138 schedule_delayed_work(&dst_gc_work
, expires
);
141 spin_unlock_bh(&dst_garbage
.lock
);
142 mutex_unlock(&dst_gc_mutex
);
145 int dst_discard(struct sk_buff
*skb
)
150 EXPORT_SYMBOL(dst_discard
);
152 const u32 dst_default_metrics
[RTAX_MAX
];
154 void *dst_alloc(struct dst_ops
*ops
, struct net_device
*dev
,
155 int initial_ref
, int initial_obsolete
, int flags
)
157 struct dst_entry
*dst
;
159 if (ops
->gc
&& dst_entries_get_fast(ops
) > ops
->gc_thresh
) {
163 dst
= kmem_cache_alloc(ops
->kmem_cachep
, GFP_ATOMIC
);
171 dst_init_metrics(dst
, dst_default_metrics
, true);
174 dst
->neighbour
= NULL
;
179 dst
->input
= dst_discard
;
180 dst
->output
= dst_discard
;
182 dst
->obsolete
= initial_obsolete
;
184 dst
->trailer_len
= 0;
185 #ifdef CONFIG_IP_ROUTE_CLASSID
188 atomic_set(&dst
->__refcnt
, initial_ref
);
190 dst
->lastuse
= jiffies
;
193 dst_entries_add(ops
, 1);
196 EXPORT_SYMBOL(dst_alloc
);
198 static void ___dst_free(struct dst_entry
*dst
)
200 /* The first case (dev==NULL) is required, when
201 protocol module is unloaded.
203 if (dst
->dev
== NULL
|| !(dst
->dev
->flags
&IFF_UP
))
204 dst
->input
= dst
->output
= dst_discard
;
208 void __dst_free(struct dst_entry
*dst
)
210 spin_lock_bh(&dst_garbage
.lock
);
212 dst
->next
= dst_garbage
.list
;
213 dst_garbage
.list
= dst
;
214 if (dst_garbage
.timer_inc
> DST_GC_INC
) {
215 dst_garbage
.timer_inc
= DST_GC_INC
;
216 dst_garbage
.timer_expires
= DST_GC_MIN
;
217 cancel_delayed_work(&dst_gc_work
);
218 schedule_delayed_work(&dst_gc_work
, dst_garbage
.timer_expires
);
220 spin_unlock_bh(&dst_garbage
.lock
);
222 EXPORT_SYMBOL(__dst_free
);
224 struct dst_entry
*dst_destroy(struct dst_entry
* dst
)
226 struct dst_entry
*child
;
227 struct neighbour
*neigh
;
233 neigh
= dst
->neighbour
;
242 dst
->neighbour
= NULL
;
243 neigh_release(neigh
);
246 dst_entries_add(dst
->ops
, -1);
248 if (dst
->ops
->destroy
)
249 dst
->ops
->destroy(dst
);
252 kmem_cache_free(dst
->ops
->kmem_cachep
, dst
);
256 int nohash
= dst
->flags
& DST_NOHASH
;
258 if (atomic_dec_and_test(&dst
->__refcnt
)) {
259 /* We were real parent of this dst, so kill child. */
263 /* Child is still referenced, return it for freeing. */
266 /* Child is still in his hash table */
271 EXPORT_SYMBOL(dst_destroy
);
273 void dst_release(struct dst_entry
*dst
)
278 newrefcnt
= atomic_dec_return(&dst
->__refcnt
);
279 WARN_ON(newrefcnt
< 0);
280 if (unlikely(dst
->flags
& DST_NOCACHE
) && !newrefcnt
) {
281 dst
= dst_destroy(dst
);
287 EXPORT_SYMBOL(dst_release
);
289 u32
*dst_cow_metrics_generic(struct dst_entry
*dst
, unsigned long old
)
291 u32
*p
= kmalloc(sizeof(u32
) * RTAX_MAX
, GFP_ATOMIC
);
294 u32
*old_p
= __DST_METRICS_PTR(old
);
295 unsigned long prev
, new;
297 memcpy(p
, old_p
, sizeof(u32
) * RTAX_MAX
);
299 new = (unsigned long) p
;
300 prev
= cmpxchg(&dst
->_metrics
, old
, new);
304 p
= __DST_METRICS_PTR(prev
);
305 if (prev
& DST_METRICS_READ_ONLY
)
311 EXPORT_SYMBOL(dst_cow_metrics_generic
);
313 /* Caller asserts that dst_metrics_read_only(dst) is false. */
314 void __dst_destroy_metrics_generic(struct dst_entry
*dst
, unsigned long old
)
316 unsigned long prev
, new;
318 new = ((unsigned long) dst_default_metrics
) | DST_METRICS_READ_ONLY
;
319 prev
= cmpxchg(&dst
->_metrics
, old
, new);
321 kfree(__DST_METRICS_PTR(old
));
323 EXPORT_SYMBOL(__dst_destroy_metrics_generic
);
326 * skb_dst_set_noref - sets skb dst, without a reference
330 * Sets skb dst, assuming a reference was not taken on dst
331 * skb_dst_drop() should not dst_release() this dst
333 void skb_dst_set_noref(struct sk_buff
*skb
, struct dst_entry
*dst
)
335 WARN_ON(!rcu_read_lock_held() && !rcu_read_lock_bh_held());
336 /* If dst not in cache, we must take a reference, because
337 * dst_release() will destroy dst as soon as its refcount becomes zero
339 if (unlikely(dst
->flags
& DST_NOCACHE
)) {
341 skb_dst_set(skb
, dst
);
343 skb
->_skb_refdst
= (unsigned long)dst
| SKB_DST_NOREF
;
346 EXPORT_SYMBOL(skb_dst_set_noref
);
348 /* Dirty hack. We did it in 2.2 (in __dst_free),
349 * we have _very_ good reasons not to repeat
350 * this mistake in 2.3, but we have no choice
351 * now. _It_ _is_ _explicit_ _deliberate_
352 * _race_ _condition_.
354 * Commented and originally written by Alexey.
356 static void dst_ifdown(struct dst_entry
*dst
, struct net_device
*dev
,
359 if (dst
->ops
->ifdown
)
360 dst
->ops
->ifdown(dst
, dev
, unregister
);
366 dst
->input
= dst
->output
= dst_discard
;
368 dst
->dev
= dev_net(dst
->dev
)->loopback_dev
;
371 if (dst
->neighbour
&& dst
->neighbour
->dev
== dev
) {
372 dst
->neighbour
->dev
= dst
->dev
;
379 static int dst_dev_event(struct notifier_block
*this, unsigned long event
,
382 struct net_device
*dev
= ptr
;
383 struct dst_entry
*dst
, *last
= NULL
;
386 case NETDEV_UNREGISTER
:
388 mutex_lock(&dst_gc_mutex
);
389 for (dst
= dst_busy_list
; dst
; dst
= dst
->next
) {
391 dst_ifdown(dst
, dev
, event
!= NETDEV_DOWN
);
394 spin_lock_bh(&dst_garbage
.lock
);
395 dst
= dst_garbage
.list
;
396 dst_garbage
.list
= NULL
;
397 spin_unlock_bh(&dst_garbage
.lock
);
403 for (; dst
; dst
= dst
->next
)
404 dst_ifdown(dst
, dev
, event
!= NETDEV_DOWN
);
405 mutex_unlock(&dst_gc_mutex
);
411 static struct notifier_block dst_dev_notifier
= {
412 .notifier_call
= dst_dev_event
,
413 .priority
= -10, /* must be called after other network notifiers */
416 void __init
dst_init(void)
418 register_netdevice_notifier(&dst_dev_notifier
);