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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                 atomic_dec(&xfrm->flow_cache_gc_count);
 98                 WARN_ON(atomic_read(&xfrm->flow_cache_gc_count) < 0);
 99         }
100 }
101 
102 static void flow_cache_queue_garbage(struct flow_cache_percpu *fcp,
103                                      int deleted, struct list_head *gc_list,
104                                      struct netns_xfrm *xfrm)
105 {
106         if (deleted) {
107                 atomic_add(deleted, &xfrm->flow_cache_gc_count);
108                 fcp->hash_count -= deleted;
109                 spin_lock_bh(&xfrm->flow_cache_gc_lock);
110                 list_splice_tail(gc_list, &xfrm->flow_cache_gc_list);
111                 spin_unlock_bh(&xfrm->flow_cache_gc_lock);
112                 schedule_work(&xfrm->flow_cache_gc_work);
113         }
114 }
115 
116 static void __flow_cache_shrink(struct flow_cache *fc,
117                                 struct flow_cache_percpu *fcp,
118                                 int shrink_to)
119 {
120         struct flow_cache_entry *fle;
121         struct hlist_node *tmp;
122         LIST_HEAD(gc_list);
123         int i, deleted = 0;
124         struct netns_xfrm *xfrm = container_of(fc, struct netns_xfrm,
125                                                 flow_cache_global);
126 
127         for (i = 0; i < flow_cache_hash_size(fc); i++) {
128                 int saved = 0;
129 
130                 hlist_for_each_entry_safe(fle, tmp,
131                                           &fcp->hash_table[i], u.hlist) {
132                         if (saved < shrink_to &&
133                             flow_entry_valid(fle, xfrm)) {
134                                 saved++;
135                         } else {
136                                 deleted++;
137                                 hlist_del(&fle->u.hlist);
138                                 list_add_tail(&fle->u.gc_list, &gc_list);
139                         }
140                 }
141         }
142 
143         flow_cache_queue_garbage(fcp, deleted, &gc_list, xfrm);
144 }
145 
146 static void flow_cache_shrink(struct flow_cache *fc,
147                               struct flow_cache_percpu *fcp)
148 {
149         int shrink_to = fc->low_watermark / flow_cache_hash_size(fc);
150 
151         __flow_cache_shrink(fc, fcp, shrink_to);
152 }
153 
154 static void flow_new_hash_rnd(struct flow_cache *fc,
155                               struct flow_cache_percpu *fcp)
156 {
157         get_random_bytes(&fcp->hash_rnd, sizeof(u32));
158         fcp->hash_rnd_recalc = 0;
159         __flow_cache_shrink(fc, fcp, 0);
160 }
161 
162 static u32 flow_hash_code(struct flow_cache *fc,
163                           struct flow_cache_percpu *fcp,
164                           const struct flowi *key,
165                           size_t keysize)
166 {
167         const u32 *k = (const u32 *) key;
168         const u32 length = keysize * sizeof(flow_compare_t) / sizeof(u32);
169 
170         return jhash2(k, length, fcp->hash_rnd)
171                 & (flow_cache_hash_size(fc) - 1);
172 }
173 
174 /* I hear what you're saying, use memcmp.  But memcmp cannot make
175  * important assumptions that we can here, such as alignment.
176  */
177 static int flow_key_compare(const struct flowi *key1, const struct flowi *key2,
178                             size_t keysize)
179 {
180         const flow_compare_t *k1, *k1_lim, *k2;
181 
182         k1 = (const flow_compare_t *) key1;
183         k1_lim = k1 + keysize;
184 
185         k2 = (const flow_compare_t *) key2;
186 
187         do {
188                 if (*k1++ != *k2++)
189                         return 1;
190         } while (k1 < k1_lim);
191 
192         return 0;
193 }
194 
195 struct flow_cache_object *
196 flow_cache_lookup(struct net *net, const struct flowi *key, u16 family, u8 dir,
197                   flow_resolve_t resolver, void *ctx)
198 {
199         struct flow_cache *fc = &net->xfrm.flow_cache_global;
200         struct flow_cache_percpu *fcp;
201         struct flow_cache_entry *fle, *tfle;
202         struct flow_cache_object *flo;
203         size_t keysize;
204         unsigned int hash;
205 
206         local_bh_disable();
207         fcp = this_cpu_ptr(fc->percpu);
208 
209         fle = NULL;
210         flo = NULL;
211 
212         keysize = flow_key_size(family);
213         if (!keysize)
214                 goto nocache;
215 
216         /* Packet really early in init?  Making flow_cache_init a
217          * pre-smp initcall would solve this.  --RR */
218         if (!fcp->hash_table)
219                 goto nocache;
220 
221         if (fcp->hash_rnd_recalc)
222                 flow_new_hash_rnd(fc, fcp);
223 
224         hash = flow_hash_code(fc, fcp, key, keysize);
225         hlist_for_each_entry(tfle, &fcp->hash_table[hash], u.hlist) {
226                 if (tfle->net == net &&
227                     tfle->family == family &&
228                     tfle->dir == dir &&
229                     flow_key_compare(key, &tfle->key, keysize) == 0) {
230                         fle = tfle;
231                         break;
232                 }
233         }
234 
235         if (unlikely(!fle)) {
236                 if (fcp->hash_count > fc->high_watermark)
237                         flow_cache_shrink(fc, fcp);
238 
239                 if (fcp->hash_count > 2 * fc->high_watermark ||
240                     atomic_read(&net->xfrm.flow_cache_gc_count) > fc->high_watermark) {
241                         atomic_inc(&net->xfrm.flow_cache_genid);
242                         flo = ERR_PTR(-ENOBUFS);
243                         goto ret_object;
244                 }
245 
246                 fle = kmem_cache_alloc(flow_cachep, GFP_ATOMIC);
247                 if (fle) {
248                         fle->net = net;
249                         fle->family = family;
250                         fle->dir = dir;
251                         memcpy(&fle->key, key, keysize * sizeof(flow_compare_t));
252                         fle->object = NULL;
253                         hlist_add_head(&fle->u.hlist, &fcp->hash_table[hash]);
254                         fcp->hash_count++;
255                 }
256         } else if (likely(fle->genid == atomic_read(&net->xfrm.flow_cache_genid))) {
257                 flo = fle->object;
258                 if (!flo)
259                         goto ret_object;
260                 flo = flo->ops->get(flo);
261                 if (flo)
262                         goto ret_object;
263         } else if (fle->object) {
264                 flo = fle->object;
265                 flo->ops->delete(flo);
266                 fle->object = NULL;
267         }
268 
269 nocache:
270         flo = NULL;
271         if (fle) {
272                 flo = fle->object;
273                 fle->object = NULL;
274         }
275         flo = resolver(net, key, family, dir, flo, ctx);
276         if (fle) {
277                 fle->genid = atomic_read(&net->xfrm.flow_cache_genid);
278                 if (!IS_ERR(flo))
279                         fle->object = flo;
280                 else
281                         fle->genid--;
282         } else {
283                 if (!IS_ERR_OR_NULL(flo))
284                         flo->ops->delete(flo);
285         }
286 ret_object:
287         local_bh_enable();
288         return flo;
289 }
290 EXPORT_SYMBOL(flow_cache_lookup);
291 
292 static void flow_cache_flush_tasklet(unsigned long data)
293 {
294         struct flow_flush_info *info = (void *)data;
295         struct flow_cache *fc = info->cache;
296         struct flow_cache_percpu *fcp;
297         struct flow_cache_entry *fle;
298         struct hlist_node *tmp;
299         LIST_HEAD(gc_list);
300         int i, deleted = 0;
301         struct netns_xfrm *xfrm = container_of(fc, struct netns_xfrm,
302                                                 flow_cache_global);
303 
304         fcp = this_cpu_ptr(fc->percpu);
305         for (i = 0; i < flow_cache_hash_size(fc); i++) {
306                 hlist_for_each_entry_safe(fle, tmp,
307                                           &fcp->hash_table[i], u.hlist) {
308                         if (flow_entry_valid(fle, xfrm))
309                                 continue;
310 
311                         deleted++;
312                         hlist_del(&fle->u.hlist);
313                         list_add_tail(&fle->u.gc_list, &gc_list);
314                 }
315         }
316 
317         flow_cache_queue_garbage(fcp, deleted, &gc_list, xfrm);
318 
319         if (atomic_dec_and_test(&info->cpuleft))
320                 complete(&info->completion);
321 }
322 
323 /*
324  * Return whether a cpu needs flushing.  Conservatively, we assume
325  * the presence of any entries means the core may require flushing,
326  * since the flow_cache_ops.check() function may assume it's running
327  * on the same core as the per-cpu cache component.
328  */
329 static int flow_cache_percpu_empty(struct flow_cache *fc, int cpu)
330 {
331         struct flow_cache_percpu *fcp;
332         int i;
333 
334         fcp = per_cpu_ptr(fc->percpu, cpu);
335         for (i = 0; i < flow_cache_hash_size(fc); i++)
336                 if (!hlist_empty(&fcp->hash_table[i]))
337                         return 0;
338         return 1;
339 }
340 
341 static void flow_cache_flush_per_cpu(void *data)
342 {
343         struct flow_flush_info *info = data;
344         struct tasklet_struct *tasklet;
345 
346         tasklet = &this_cpu_ptr(info->cache->percpu)->flush_tasklet;
347         tasklet->data = (unsigned long)info;
348         tasklet_schedule(tasklet);
349 }
350 
351 void flow_cache_flush(struct net *net)
352 {
353         struct flow_flush_info info;
354         cpumask_var_t mask;
355         int i, self;
356 
357         /* Track which cpus need flushing to avoid disturbing all cores. */
358         if (!alloc_cpumask_var(&mask, GFP_KERNEL))
359                 return;
360         cpumask_clear(mask);
361 
362         /* Don't want cpus going down or up during this. */
363         get_online_cpus();
364         mutex_lock(&net->xfrm.flow_flush_sem);
365         info.cache = &net->xfrm.flow_cache_global;
366         for_each_online_cpu(i)
367                 if (!flow_cache_percpu_empty(info.cache, i))
368                         cpumask_set_cpu(i, mask);
369         atomic_set(&info.cpuleft, cpumask_weight(mask));
370         if (atomic_read(&info.cpuleft) == 0)
371                 goto done;
372 
373         init_completion(&info.completion);
374 
375         local_bh_disable();
376         self = cpumask_test_and_clear_cpu(smp_processor_id(), mask);
377         on_each_cpu_mask(mask, flow_cache_flush_per_cpu, &info, 0);
378         if (self)
379                 flow_cache_flush_tasklet((unsigned long)&info);
380         local_bh_enable();
381 
382         wait_for_completion(&info.completion);
383 
384 done:
385         mutex_unlock(&net->xfrm.flow_flush_sem);
386         put_online_cpus();
387         free_cpumask_var(mask);
388 }
389 
390 static void flow_cache_flush_task(struct work_struct *work)
391 {
392         struct netns_xfrm *xfrm = container_of(work, struct netns_xfrm,
393                                                 flow_cache_flush_work);
394         struct net *net = container_of(xfrm, struct net, xfrm);
395 
396         flow_cache_flush(net);
397 }
398 
399 void flow_cache_flush_deferred(struct net *net)
400 {
401         schedule_work(&net->xfrm.flow_cache_flush_work);
402 }
403 
404 static int flow_cache_cpu_prepare(struct flow_cache *fc, int cpu)
405 {
406         struct flow_cache_percpu *fcp = per_cpu_ptr(fc->percpu, cpu);
407         size_t sz = sizeof(struct hlist_head) * flow_cache_hash_size(fc);
408 
409         if (!fcp->hash_table) {
410                 fcp->hash_table = kzalloc_node(sz, GFP_KERNEL, cpu_to_node(cpu));
411                 if (!fcp->hash_table) {
412                         pr_err("NET: failed to allocate flow cache sz %zu\n", sz);
413                         return -ENOMEM;
414                 }
415                 fcp->hash_rnd_recalc = 1;
416                 fcp->hash_count = 0;
417                 tasklet_init(&fcp->flush_tasklet, flow_cache_flush_tasklet, 0);
418         }
419         return 0;
420 }
421 
422 static int flow_cache_cpu(struct notifier_block *nfb,
423                           unsigned long action,
424                           void *hcpu)
425 {
426         struct flow_cache *fc = container_of(nfb, struct flow_cache,
427                                                 hotcpu_notifier);
428         int res, cpu = (unsigned long) hcpu;
429         struct flow_cache_percpu *fcp = per_cpu_ptr(fc->percpu, cpu);
430 
431         switch (action) {
432         case CPU_UP_PREPARE:
433         case CPU_UP_PREPARE_FROZEN:
434                 res = flow_cache_cpu_prepare(fc, cpu);
435                 if (res)
436                         return notifier_from_errno(res);
437                 break;
438         case CPU_DEAD:
439         case CPU_DEAD_FROZEN:
440                 __flow_cache_shrink(fc, fcp, 0);
441                 break;
442         }
443         return NOTIFY_OK;
444 }
445 
446 int flow_cache_init(struct net *net)
447 {
448         int i;
449         struct flow_cache *fc = &net->xfrm.flow_cache_global;
450 
451         if (!flow_cachep)
452                 flow_cachep = kmem_cache_create("flow_cache",
453                                                 sizeof(struct flow_cache_entry),
454                                                 0, SLAB_PANIC, NULL);
455         spin_lock_init(&net->xfrm.flow_cache_gc_lock);
456         INIT_LIST_HEAD(&net->xfrm.flow_cache_gc_list);
457         INIT_WORK(&net->xfrm.flow_cache_gc_work, flow_cache_gc_task);
458         INIT_WORK(&net->xfrm.flow_cache_flush_work, flow_cache_flush_task);
459         mutex_init(&net->xfrm.flow_flush_sem);
460         atomic_set(&net->xfrm.flow_cache_gc_count, 0);
461 
462         fc->hash_shift = 10;
463         fc->low_watermark = 2 * flow_cache_hash_size(fc);
464         fc->high_watermark = 4 * flow_cache_hash_size(fc);
465 
466         fc->percpu = alloc_percpu(struct flow_cache_percpu);
467         if (!fc->percpu)
468                 return -ENOMEM;
469 
470         cpu_notifier_register_begin();
471 
472         for_each_online_cpu(i) {
473                 if (flow_cache_cpu_prepare(fc, i))
474                         goto err;
475         }
476         fc->hotcpu_notifier = (struct notifier_block){
477                 .notifier_call = flow_cache_cpu,
478         };
479         __register_hotcpu_notifier(&fc->hotcpu_notifier);
480 
481         cpu_notifier_register_done();
482 
483         setup_timer(&fc->rnd_timer, flow_cache_new_hashrnd,
484                     (unsigned long) fc);
485         fc->rnd_timer.expires = jiffies + FLOW_HASH_RND_PERIOD;
486         add_timer(&fc->rnd_timer);
487 
488         return 0;
489 
490 err:
491         for_each_possible_cpu(i) {
492                 struct flow_cache_percpu *fcp = per_cpu_ptr(fc->percpu, i);
493                 kfree(fcp->hash_table);
494                 fcp->hash_table = NULL;
495         }
496 
497         cpu_notifier_register_done();
498 
499         free_percpu(fc->percpu);
500         fc->percpu = NULL;
501 
502         return -ENOMEM;
503 }
504 EXPORT_SYMBOL(flow_cache_init);
505 
506 void flow_cache_fini(struct net *net)
507 {
508         int i;
509         struct flow_cache *fc = &net->xfrm.flow_cache_global;
510 
511         del_timer_sync(&fc->rnd_timer);
512         unregister_hotcpu_notifier(&fc->hotcpu_notifier);
513 
514         for_each_possible_cpu(i) {
515                 struct flow_cache_percpu *fcp = per_cpu_ptr(fc->percpu, i);
516                 kfree(fcp->hash_table);
517                 fcp->hash_table = NULL;
518         }
519 
520         free_percpu(fc->percpu);
521         fc->percpu = NULL;
522 }
523 EXPORT_SYMBOL(flow_cache_fini);
524 

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