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TOMOYO Linux Cross Reference
Linux/net/core/flow.c

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  1 /* flow.c: Generic flow cache.
  2  *
  3  * Copyright (C) 2003 Alexey N. Kuznetsov (kuznet@ms2.inr.ac.ru)
  4  * Copyright (C) 2003 David S. Miller (davem@redhat.com)
  5  */
  6 
  7 #include <linux/kernel.h>
  8 #include <linux/module.h>
  9 #include <linux/list.h>
 10 #include <linux/jhash.h>
 11 #include <linux/interrupt.h>
 12 #include <linux/mm.h>
 13 #include <linux/random.h>
 14 #include <linux/init.h>
 15 #include <linux/slab.h>
 16 #include <linux/smp.h>
 17 #include <linux/completion.h>
 18 #include <linux/percpu.h>
 19 #include <linux/bitops.h>
 20 #include <linux/notifier.h>
 21 #include <linux/cpu.h>
 22 #include <linux/cpumask.h>
 23 #include <linux/mutex.h>
 24 #include <net/flow.h>
 25 #include <linux/atomic.h>
 26 #include <linux/security.h>
 27 #include <net/net_namespace.h>
 28 
 29 struct flow_cache_entry {
 30         union {
 31                 struct hlist_node       hlist;
 32                 struct list_head        gc_list;
 33         } u;
 34         struct net                      *net;
 35         u16                             family;
 36         u8                              dir;
 37         u32                             genid;
 38         struct flowi                    key;
 39         struct flow_cache_object        *object;
 40 };
 41 
 42 struct flow_flush_info {
 43         struct flow_cache               *cache;
 44         atomic_t                        cpuleft;
 45         struct completion               completion;
 46 };
 47 
 48 static struct kmem_cache *flow_cachep __read_mostly;
 49 
 50 #define flow_cache_hash_size(cache)     (1 << (cache)->hash_shift)
 51 #define FLOW_HASH_RND_PERIOD            (10 * 60 * HZ)
 52 
 53 static void flow_cache_new_hashrnd(unsigned long arg)
 54 {
 55         struct flow_cache *fc = (void *) arg;
 56         int i;
 57 
 58         for_each_possible_cpu(i)
 59                 per_cpu_ptr(fc->percpu, i)->hash_rnd_recalc = 1;
 60 
 61         fc->rnd_timer.expires = jiffies + FLOW_HASH_RND_PERIOD;
 62         add_timer(&fc->rnd_timer);
 63 }
 64 
 65 static int flow_entry_valid(struct flow_cache_entry *fle,
 66                                 struct netns_xfrm *xfrm)
 67 {
 68         if (atomic_read(&xfrm->flow_cache_genid) != fle->genid)
 69                 return 0;
 70         if (fle->object && !fle->object->ops->check(fle->object))
 71                 return 0;
 72         return 1;
 73 }
 74 
 75 static void flow_entry_kill(struct flow_cache_entry *fle,
 76                                 struct netns_xfrm *xfrm)
 77 {
 78         if (fle->object)
 79                 fle->object->ops->delete(fle->object);
 80         kmem_cache_free(flow_cachep, fle);
 81 }
 82 
 83 static void flow_cache_gc_task(struct work_struct *work)
 84 {
 85         struct list_head gc_list;
 86         struct flow_cache_entry *fce, *n;
 87         struct netns_xfrm *xfrm = container_of(work, struct netns_xfrm,
 88                                                 flow_cache_gc_work);
 89 
 90         INIT_LIST_HEAD(&gc_list);
 91         spin_lock_bh(&xfrm->flow_cache_gc_lock);
 92         list_splice_tail_init(&xfrm->flow_cache_gc_list, &gc_list);
 93         spin_unlock_bh(&xfrm->flow_cache_gc_lock);
 94 
 95         list_for_each_entry_safe(fce, n, &gc_list, u.gc_list)
 96                 flow_entry_kill(fce, xfrm);
 97 }
 98 
 99 static void flow_cache_queue_garbage(struct flow_cache_percpu *fcp,
100                                      int deleted, struct list_head *gc_list,
101                                      struct netns_xfrm *xfrm)
102 {
103         if (deleted) {
104                 fcp->hash_count -= deleted;
105                 spin_lock_bh(&xfrm->flow_cache_gc_lock);
106                 list_splice_tail(gc_list, &xfrm->flow_cache_gc_list);
107                 spin_unlock_bh(&xfrm->flow_cache_gc_lock);
108                 schedule_work(&xfrm->flow_cache_gc_work);
109         }
110 }
111 
112 static void __flow_cache_shrink(struct flow_cache *fc,
113                                 struct flow_cache_percpu *fcp,
114                                 int shrink_to)
115 {
116         struct flow_cache_entry *fle;
117         struct hlist_node *tmp;
118         LIST_HEAD(gc_list);
119         int i, deleted = 0;
120         struct netns_xfrm *xfrm = container_of(fc, struct netns_xfrm,
121                                                 flow_cache_global);
122 
123         for (i = 0; i < flow_cache_hash_size(fc); i++) {
124                 int saved = 0;
125 
126                 hlist_for_each_entry_safe(fle, tmp,
127                                           &fcp->hash_table[i], u.hlist) {
128                         if (saved < shrink_to &&
129                             flow_entry_valid(fle, xfrm)) {
130                                 saved++;
131                         } else {
132                                 deleted++;
133                                 hlist_del(&fle->u.hlist);
134                                 list_add_tail(&fle->u.gc_list, &gc_list);
135                         }
136                 }
137         }
138 
139         flow_cache_queue_garbage(fcp, deleted, &gc_list, xfrm);
140 }
141 
142 static void flow_cache_shrink(struct flow_cache *fc,
143                               struct flow_cache_percpu *fcp)
144 {
145         int shrink_to = fc->low_watermark / flow_cache_hash_size(fc);
146 
147         __flow_cache_shrink(fc, fcp, shrink_to);
148 }
149 
150 static void flow_new_hash_rnd(struct flow_cache *fc,
151                               struct flow_cache_percpu *fcp)
152 {
153         get_random_bytes(&fcp->hash_rnd, sizeof(u32));
154         fcp->hash_rnd_recalc = 0;
155         __flow_cache_shrink(fc, fcp, 0);
156 }
157 
158 static u32 flow_hash_code(struct flow_cache *fc,
159                           struct flow_cache_percpu *fcp,
160                           const struct flowi *key,
161                           size_t keysize)
162 {
163         const u32 *k = (const u32 *) key;
164         const u32 length = keysize * sizeof(flow_compare_t) / sizeof(u32);
165 
166         return jhash2(k, length, fcp->hash_rnd)
167                 & (flow_cache_hash_size(fc) - 1);
168 }
169 
170 /* I hear what you're saying, use memcmp.  But memcmp cannot make
171  * important assumptions that we can here, such as alignment.
172  */
173 static int flow_key_compare(const struct flowi *key1, const struct flowi *key2,
174                             size_t keysize)
175 {
176         const flow_compare_t *k1, *k1_lim, *k2;
177 
178         k1 = (const flow_compare_t *) key1;
179         k1_lim = k1 + keysize;
180 
181         k2 = (const flow_compare_t *) key2;
182 
183         do {
184                 if (*k1++ != *k2++)
185                         return 1;
186         } while (k1 < k1_lim);
187 
188         return 0;
189 }
190 
191 struct flow_cache_object *
192 flow_cache_lookup(struct net *net, const struct flowi *key, u16 family, u8 dir,
193                   flow_resolve_t resolver, void *ctx)
194 {
195         struct flow_cache *fc = &net->xfrm.flow_cache_global;
196         struct flow_cache_percpu *fcp;
197         struct flow_cache_entry *fle, *tfle;
198         struct flow_cache_object *flo;
199         size_t keysize;
200         unsigned int hash;
201 
202         local_bh_disable();
203         fcp = this_cpu_ptr(fc->percpu);
204 
205         fle = NULL;
206         flo = NULL;
207 
208         keysize = flow_key_size(family);
209         if (!keysize)
210                 goto nocache;
211 
212         /* Packet really early in init?  Making flow_cache_init a
213          * pre-smp initcall would solve this.  --RR */
214         if (!fcp->hash_table)
215                 goto nocache;
216 
217         if (fcp->hash_rnd_recalc)
218                 flow_new_hash_rnd(fc, fcp);
219 
220         hash = flow_hash_code(fc, fcp, key, keysize);
221         hlist_for_each_entry(tfle, &fcp->hash_table[hash], u.hlist) {
222                 if (tfle->net == net &&
223                     tfle->family == family &&
224                     tfle->dir == dir &&
225                     flow_key_compare(key, &tfle->key, keysize) == 0) {
226                         fle = tfle;
227                         break;
228                 }
229         }
230 
231         if (unlikely(!fle)) {
232                 if (fcp->hash_count > fc->high_watermark)
233                         flow_cache_shrink(fc, fcp);
234 
235                 fle = kmem_cache_alloc(flow_cachep, GFP_ATOMIC);
236                 if (fle) {
237                         fle->net = net;
238                         fle->family = family;
239                         fle->dir = dir;
240                         memcpy(&fle->key, key, keysize * sizeof(flow_compare_t));
241                         fle->object = NULL;
242                         hlist_add_head(&fle->u.hlist, &fcp->hash_table[hash]);
243                         fcp->hash_count++;
244                 }
245         } else if (likely(fle->genid == atomic_read(&net->xfrm.flow_cache_genid))) {
246                 flo = fle->object;
247                 if (!flo)
248                         goto ret_object;
249                 flo = flo->ops->get(flo);
250                 if (flo)
251                         goto ret_object;
252         } else if (fle->object) {
253                 flo = fle->object;
254                 flo->ops->delete(flo);
255                 fle->object = NULL;
256         }
257 
258 nocache:
259         flo = NULL;
260         if (fle) {
261                 flo = fle->object;
262                 fle->object = NULL;
263         }
264         flo = resolver(net, key, family, dir, flo, ctx);
265         if (fle) {
266                 fle->genid = atomic_read(&net->xfrm.flow_cache_genid);
267                 if (!IS_ERR(flo))
268                         fle->object = flo;
269                 else
270                         fle->genid--;
271         } else {
272                 if (!IS_ERR_OR_NULL(flo))
273                         flo->ops->delete(flo);
274         }
275 ret_object:
276         local_bh_enable();
277         return flo;
278 }
279 EXPORT_SYMBOL(flow_cache_lookup);
280 
281 static void flow_cache_flush_tasklet(unsigned long data)
282 {
283         struct flow_flush_info *info = (void *)data;
284         struct flow_cache *fc = info->cache;
285         struct flow_cache_percpu *fcp;
286         struct flow_cache_entry *fle;
287         struct hlist_node *tmp;
288         LIST_HEAD(gc_list);
289         int i, deleted = 0;
290         struct netns_xfrm *xfrm = container_of(fc, struct netns_xfrm,
291                                                 flow_cache_global);
292 
293         fcp = this_cpu_ptr(fc->percpu);
294         for (i = 0; i < flow_cache_hash_size(fc); i++) {
295                 hlist_for_each_entry_safe(fle, tmp,
296                                           &fcp->hash_table[i], u.hlist) {
297                         if (flow_entry_valid(fle, xfrm))
298                                 continue;
299 
300                         deleted++;
301                         hlist_del(&fle->u.hlist);
302                         list_add_tail(&fle->u.gc_list, &gc_list);
303                 }
304         }
305 
306         flow_cache_queue_garbage(fcp, deleted, &gc_list, xfrm);
307 
308         if (atomic_dec_and_test(&info->cpuleft))
309                 complete(&info->completion);
310 }
311 
312 /*
313  * Return whether a cpu needs flushing.  Conservatively, we assume
314  * the presence of any entries means the core may require flushing,
315  * since the flow_cache_ops.check() function may assume it's running
316  * on the same core as the per-cpu cache component.
317  */
318 static int flow_cache_percpu_empty(struct flow_cache *fc, int cpu)
319 {
320         struct flow_cache_percpu *fcp;
321         int i;
322 
323         fcp = per_cpu_ptr(fc->percpu, cpu);
324         for (i = 0; i < flow_cache_hash_size(fc); i++)
325                 if (!hlist_empty(&fcp->hash_table[i]))
326                         return 0;
327         return 1;
328 }
329 
330 static void flow_cache_flush_per_cpu(void *data)
331 {
332         struct flow_flush_info *info = data;
333         struct tasklet_struct *tasklet;
334 
335         tasklet = &this_cpu_ptr(info->cache->percpu)->flush_tasklet;
336         tasklet->data = (unsigned long)info;
337         tasklet_schedule(tasklet);
338 }
339 
340 void flow_cache_flush(struct net *net)
341 {
342         struct flow_flush_info info;
343         cpumask_var_t mask;
344         int i, self;
345 
346         /* Track which cpus need flushing to avoid disturbing all cores. */
347         if (!alloc_cpumask_var(&mask, GFP_KERNEL))
348                 return;
349         cpumask_clear(mask);
350 
351         /* Don't want cpus going down or up during this. */
352         get_online_cpus();
353         mutex_lock(&net->xfrm.flow_flush_sem);
354         info.cache = &net->xfrm.flow_cache_global;
355         for_each_online_cpu(i)
356                 if (!flow_cache_percpu_empty(info.cache, i))
357                         cpumask_set_cpu(i, mask);
358         atomic_set(&info.cpuleft, cpumask_weight(mask));
359         if (atomic_read(&info.cpuleft) == 0)
360                 goto done;
361 
362         init_completion(&info.completion);
363 
364         local_bh_disable();
365         self = cpumask_test_and_clear_cpu(smp_processor_id(), mask);
366         on_each_cpu_mask(mask, flow_cache_flush_per_cpu, &info, 0);
367         if (self)
368                 flow_cache_flush_tasklet((unsigned long)&info);
369         local_bh_enable();
370 
371         wait_for_completion(&info.completion);
372 
373 done:
374         mutex_unlock(&net->xfrm.flow_flush_sem);
375         put_online_cpus();
376         free_cpumask_var(mask);
377 }
378 
379 static void flow_cache_flush_task(struct work_struct *work)
380 {
381         struct netns_xfrm *xfrm = container_of(work, struct netns_xfrm,
382                                                 flow_cache_flush_work);
383         struct net *net = container_of(xfrm, struct net, xfrm);
384 
385         flow_cache_flush(net);
386 }
387 
388 void flow_cache_flush_deferred(struct net *net)
389 {
390         schedule_work(&net->xfrm.flow_cache_flush_work);
391 }
392 
393 static int flow_cache_cpu_prepare(struct flow_cache *fc, int cpu)
394 {
395         struct flow_cache_percpu *fcp = per_cpu_ptr(fc->percpu, cpu);
396         size_t sz = sizeof(struct hlist_head) * flow_cache_hash_size(fc);
397 
398         if (!fcp->hash_table) {
399                 fcp->hash_table = kzalloc_node(sz, GFP_KERNEL, cpu_to_node(cpu));
400                 if (!fcp->hash_table) {
401                         pr_err("NET: failed to allocate flow cache sz %zu\n", sz);
402                         return -ENOMEM;
403                 }
404                 fcp->hash_rnd_recalc = 1;
405                 fcp->hash_count = 0;
406                 tasklet_init(&fcp->flush_tasklet, flow_cache_flush_tasklet, 0);
407         }
408         return 0;
409 }
410 
411 static int flow_cache_cpu(struct notifier_block *nfb,
412                           unsigned long action,
413                           void *hcpu)
414 {
415         struct flow_cache *fc = container_of(nfb, struct flow_cache,
416                                                 hotcpu_notifier);
417         int res, cpu = (unsigned long) hcpu;
418         struct flow_cache_percpu *fcp = per_cpu_ptr(fc->percpu, cpu);
419 
420         switch (action) {
421         case CPU_UP_PREPARE:
422         case CPU_UP_PREPARE_FROZEN:
423                 res = flow_cache_cpu_prepare(fc, cpu);
424                 if (res)
425                         return notifier_from_errno(res);
426                 break;
427         case CPU_DEAD:
428         case CPU_DEAD_FROZEN:
429                 __flow_cache_shrink(fc, fcp, 0);
430                 break;
431         }
432         return NOTIFY_OK;
433 }
434 
435 int flow_cache_init(struct net *net)
436 {
437         int i;
438         struct flow_cache *fc = &net->xfrm.flow_cache_global;
439 
440         if (!flow_cachep)
441                 flow_cachep = kmem_cache_create("flow_cache",
442                                                 sizeof(struct flow_cache_entry),
443                                                 0, SLAB_PANIC, NULL);
444         spin_lock_init(&net->xfrm.flow_cache_gc_lock);
445         INIT_LIST_HEAD(&net->xfrm.flow_cache_gc_list);
446         INIT_WORK(&net->xfrm.flow_cache_gc_work, flow_cache_gc_task);
447         INIT_WORK(&net->xfrm.flow_cache_flush_work, flow_cache_flush_task);
448         mutex_init(&net->xfrm.flow_flush_sem);
449 
450         fc->hash_shift = 10;
451         fc->low_watermark = 2 * flow_cache_hash_size(fc);
452         fc->high_watermark = 4 * flow_cache_hash_size(fc);
453 
454         fc->percpu = alloc_percpu(struct flow_cache_percpu);
455         if (!fc->percpu)
456                 return -ENOMEM;
457 
458         cpu_notifier_register_begin();
459 
460         for_each_online_cpu(i) {
461                 if (flow_cache_cpu_prepare(fc, i))
462                         goto err;
463         }
464         fc->hotcpu_notifier = (struct notifier_block){
465                 .notifier_call = flow_cache_cpu,
466         };
467         __register_hotcpu_notifier(&fc->hotcpu_notifier);
468 
469         cpu_notifier_register_done();
470 
471         setup_timer(&fc->rnd_timer, flow_cache_new_hashrnd,
472                     (unsigned long) fc);
473         fc->rnd_timer.expires = jiffies + FLOW_HASH_RND_PERIOD;
474         add_timer(&fc->rnd_timer);
475 
476         return 0;
477 
478 err:
479         for_each_possible_cpu(i) {
480                 struct flow_cache_percpu *fcp = per_cpu_ptr(fc->percpu, i);
481                 kfree(fcp->hash_table);
482                 fcp->hash_table = NULL;
483         }
484 
485         cpu_notifier_register_done();
486 
487         free_percpu(fc->percpu);
488         fc->percpu = NULL;
489 
490         return -ENOMEM;
491 }
492 EXPORT_SYMBOL(flow_cache_init);
493 
494 void flow_cache_fini(struct net *net)
495 {
496         int i;
497         struct flow_cache *fc = &net->xfrm.flow_cache_global;
498 
499         del_timer_sync(&fc->rnd_timer);
500         unregister_hotcpu_notifier(&fc->hotcpu_notifier);
501 
502         for_each_possible_cpu(i) {
503                 struct flow_cache_percpu *fcp = per_cpu_ptr(fc->percpu, i);
504                 kfree(fcp->hash_table);
505                 fcp->hash_table = NULL;
506         }
507 
508         free_percpu(fc->percpu);
509         fc->percpu = NULL;
510 }
511 EXPORT_SYMBOL(flow_cache_fini);
512 

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