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

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