1 /*
2 * net/core/dst.c Protocol independent destination cache.
3 *
4 * Authors: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
5 *
6 */
7
8 #include <linux/bitops.h>
9 #include <linux/errno.h>
10 #include <linux/init.h>
11 #include <linux/kernel.h>
12 #include <linux/mm.h>
13 #include <linux/module.h>
14 #include <linux/netdevice.h>
15 #include <linux/sched.h>
16 #include <linux/skbuff.h>
17 #include <linux/string.h>
18 #include <linux/types.h>
19
20 #include <net/dst.h>
21
22 /* Locking strategy:
23 * 1) Garbage collection state of dead destination cache
24 * entries is protected by dst_lock.
25 * 2) GC is run only from BH context, and is the only remover
26 * of entries.
27 * 3) Entries are added to the garbage list from both BH
28 * and non-BH context, so local BH disabling is needed.
29 * 4) All operations modify state, so a spinlock is used.
30 */
31 static struct dst_entry *dst_garbage_list;
32 #if RT_CACHE_DEBUG >= 2
33 static atomic_t dst_total = ATOMIC_INIT(0);
34 #endif
35 static DEFINE_SPINLOCK(dst_lock);
36
37 static unsigned long dst_gc_timer_expires;
38 static unsigned long dst_gc_timer_inc = DST_GC_MAX;
39 static void dst_run_gc(unsigned long);
40 static void ___dst_free(struct dst_entry * dst);
41
42 static struct timer_list dst_gc_timer =
43 TIMER_INITIALIZER(dst_run_gc, DST_GC_MIN, 0);
44
45 static void dst_run_gc(unsigned long dummy)
46 {
47 int delayed = 0;
48 struct dst_entry * dst, **dstp;
49
50 if (!spin_trylock(&dst_lock)) {
51 mod_timer(&dst_gc_timer, jiffies + HZ/10);
52 return;
53 }
54
55
56 del_timer(&dst_gc_timer);
57 dstp = &dst_garbage_list;
58 while ((dst = *dstp) != NULL) {
59 if (atomic_read(&dst->__refcnt)) {
60 dstp = &dst->next;
61 delayed++;
62 continue;
63 }
64 *dstp = dst->next;
65
66 dst = dst_destroy(dst);
67 if (dst) {
68 /* NOHASH and still referenced. Unless it is already
69 * on gc list, invalidate it and add to gc list.
70 *
71 * Note: this is temporary. Actually, NOHASH dst's
72 * must be obsoleted when parent is obsoleted.
73 * But we do not have state "obsoleted, but
74 * referenced by parent", so it is right.
75 */
76 if (dst->obsolete > 1)
77 continue;
78
79 ___dst_free(dst);
80 dst->next = *dstp;
81 *dstp = dst;
82 dstp = &dst->next;
83 }
84 }
85 if (!dst_garbage_list) {
86 dst_gc_timer_inc = DST_GC_MAX;
87 goto out;
88 }
89 if ((dst_gc_timer_expires += dst_gc_timer_inc) > DST_GC_MAX)
90 dst_gc_timer_expires = DST_GC_MAX;
91 dst_gc_timer_inc += DST_GC_INC;
92 dst_gc_timer.expires = jiffies + dst_gc_timer_expires;
93 #if RT_CACHE_DEBUG >= 2
94 printk("dst_total: %d/%d %ld\n",
95 atomic_read(&dst_total), delayed, dst_gc_timer_expires);
96 #endif
97 add_timer(&dst_gc_timer);
98
99 out:
100 spin_unlock(&dst_lock);
101 }
102
103 static int dst_discard_in(struct sk_buff *skb)
104 {
105 kfree_skb(skb);
106 return 0;
107 }
108
109 static int dst_discard_out(struct sk_buff *skb)
110 {
111 kfree_skb(skb);
112 return 0;
113 }
114
115 void * dst_alloc(struct dst_ops * ops)
116 {
117 struct dst_entry * dst;
118
119 if (ops->gc && atomic_read(&ops->entries) > ops->gc_thresh) {
120 if (ops->gc())
121 return NULL;
122 }
123 dst = kmem_cache_alloc(ops->kmem_cachep, SLAB_ATOMIC);
124 if (!dst)
125 return NULL;
126 memset(dst, 0, ops->entry_size);
127 atomic_set(&dst->__refcnt, 0);
128 dst->ops = ops;
129 dst->lastuse = jiffies;
130 dst->path = dst;
131 dst->input = dst_discard_in;
132 dst->output = dst_discard_out;
133 #if RT_CACHE_DEBUG >= 2
134 atomic_inc(&dst_total);
135 #endif
136 atomic_inc(&ops->entries);
137 return dst;
138 }
139
140 static void ___dst_free(struct dst_entry * dst)
141 {
142 /* The first case (dev==NULL) is required, when
143 protocol module is unloaded.
144 */
145 if (dst->dev == NULL || !(dst->dev->flags&IFF_UP)) {
146 dst->input = dst_discard_in;
147 dst->output = dst_discard_out;
148 }
149 dst->obsolete = 2;
150 }
151
152 void __dst_free(struct dst_entry * dst)
153 {
154 spin_lock_bh(&dst_lock);
155 ___dst_free(dst);
156 dst->next = dst_garbage_list;
157 dst_garbage_list = dst;
158 if (dst_gc_timer_inc > DST_GC_INC) {
159 dst_gc_timer_inc = DST_GC_INC;
160 dst_gc_timer_expires = DST_GC_MIN;
161 mod_timer(&dst_gc_timer, jiffies + dst_gc_timer_expires);
162 }
163 spin_unlock_bh(&dst_lock);
164 }
165
166 struct dst_entry *dst_destroy(struct dst_entry * dst)
167 {
168 struct dst_entry *child;
169 struct neighbour *neigh;
170 struct hh_cache *hh;
171
172 smp_rmb();
173
174 again:
175 neigh = dst->neighbour;
176 hh = dst->hh;
177 child = dst->child;
178
179 dst->hh = NULL;
180 if (hh && atomic_dec_and_test(&hh->hh_refcnt))
181 kfree(hh);
182
183 if (neigh) {
184 dst->neighbour = NULL;
185 neigh_release(neigh);
186 }
187
188 atomic_dec(&dst->ops->entries);
189
190 if (dst->ops->destroy)
191 dst->ops->destroy(dst);
192 if (dst->dev)
193 dev_put(dst->dev);
194 #if RT_CACHE_DEBUG >= 2
195 atomic_dec(&dst_total);
196 #endif
197 kmem_cache_free(dst->ops->kmem_cachep, dst);
198
199 dst = child;
200 if (dst) {
201 if (atomic_dec_and_test(&dst->__refcnt)) {
202 /* We were real parent of this dst, so kill child. */
203 if (dst->flags&DST_NOHASH)
204 goto again;
205 } else {
206 /* Child is still referenced, return it for freeing. */
207 if (dst->flags&DST_NOHASH)
208 return dst;
209 /* Child is still in his hash table */
210 }
211 }
212 return NULL;
213 }
214
215 /* Dirty hack. We did it in 2.2 (in __dst_free),
216 * we have _very_ good reasons not to repeat
217 * this mistake in 2.3, but we have no choice
218 * now. _It_ _is_ _explicit_ _deliberate_
219 * _race_ _condition_.
220 *
221 * Commented and originally written by Alexey.
222 */
223 static inline void dst_ifdown(struct dst_entry *dst, struct net_device *dev,
224 int unregister)
225 {
226 if (dst->ops->ifdown)
227 dst->ops->ifdown(dst, dev, unregister);
228
229 if (dev != dst->dev)
230 return;
231
232 if (!unregister) {
233 dst->input = dst_discard_in;
234 dst->output = dst_discard_out;
235 } else {
236 dst->dev = &loopback_dev;
237 dev_hold(&loopback_dev);
238 dev_put(dev);
239 if (dst->neighbour && dst->neighbour->dev == dev) {
240 dst->neighbour->dev = &loopback_dev;
241 dev_put(dev);
242 dev_hold(&loopback_dev);
243 }
244 }
245 }
246
247 static int dst_dev_event(struct notifier_block *this, unsigned long event, void *ptr)
248 {
249 struct net_device *dev = ptr;
250 struct dst_entry *dst;
251
252 switch (event) {
253 case NETDEV_UNREGISTER:
254 case NETDEV_DOWN:
255 spin_lock_bh(&dst_lock);
256 for (dst = dst_garbage_list; dst; dst = dst->next) {
257 dst_ifdown(dst, dev, event != NETDEV_DOWN);
258 }
259 spin_unlock_bh(&dst_lock);
260 break;
261 }
262 return NOTIFY_DONE;
263 }
264
265 static struct notifier_block dst_dev_notifier = {
266 .notifier_call = dst_dev_event,
267 };
268
269 void __init dst_init(void)
270 {
271 register_netdevice_notifier(&dst_dev_notifier);
272 }
273
274 EXPORT_SYMBOL(__dst_free);
275 EXPORT_SYMBOL(dst_alloc);
276 EXPORT_SYMBOL(dst_destroy);
277
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