net/core/flow.c

   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 <asm/atomic.h>
  26 #include <linux/security.h>
  27
  28 struct flow_cache_entry {
  29         union {
  30                 struct hlist_node       hlist;
  31                 struct list_head        gc_list;
  32         } u;
  33         u16                             family;
  34         u8                              dir;
  35         u32                             genid;
  36         struct flowi                    key;
  37         struct flow_cache_object        *object;
  38 };
  39
  40 struct flow_cache_percpu {
  41         struct hlist_head               *hash_table;
  42         int                             hash_count;
  43         u32                             hash_rnd;
  44         int                             hash_rnd_recalc;
  45         struct tasklet_struct           flush_tasklet;
  46 };
  47
  48 struct flow_flush_info {
  49         struct flow_cache               *cache;
  50         atomic_t                        cpuleft;
  51         struct completion               completion;
  52 };
  53
  54 struct flow_cache {
  55         u32                             hash_shift;
  56         unsigned long                   order;
  57         struct flow_cache_percpu        *percpu;
  58         struct notifier_block           hotcpu_notifier;
  59         int                             low_watermark;
  60         int                             high_watermark;
  61         struct timer_list               rnd_timer;
  62 };
  63
  64 atomic_t flow_cache_genid = ATOMIC_INIT(0);
  65 static struct flow_cache flow_cache_global;
  66 static struct kmem_cache *flow_cachep;
  67
  68 static DEFINE_SPINLOCK(flow_cache_gc_lock);
  69 static LIST_HEAD(flow_cache_gc_list);
  70
  71 #define flow_cache_hash_size(cache)     (1 << (cache)->hash_shift)
  72 #define FLOW_HASH_RND_PERIOD            (10 * 60 * HZ)
  73
  74 static void flow_cache_new_hashrnd(unsigned long arg)
  75 {
  76         struct flow_cache *fc = (void *) arg;
  77         int i;
  78
  79         for_each_possible_cpu(i)
  80                 per_cpu_ptr(fc->percpu, i)->hash_rnd_recalc = 1;
  81
  82         fc->rnd_timer.expires = jiffies + FLOW_HASH_RND_PERIOD;
  83         add_timer(&fc->rnd_timer);
  84 }
  85
  86 static int flow_entry_valid(struct flow_cache_entry *fle)
  87 {
  88         if (atomic_read(&flow_cache_genid) != fle->genid)
  89                 return 0;
  90         if (fle->object && !fle->object->ops->check(fle->object))
  91                 return 0;
  92         return 1;
  93 }
  94
  95 static void flow_entry_kill(struct flow_cache_entry *fle)
  96 {
  97         if (fle->object)
  98                 fle->object->ops->delete(fle->object);
  99         kmem_cache_free(flow_cachep, fle);
 100 }
 101
 102 static void flow_cache_gc_task(struct work_struct *work)
 103 {
 104         struct list_head gc_list;
 105         struct flow_cache_entry *fce, *n;
 106
 107         INIT_LIST_HEAD(&gc_list);
 108         spin_lock_bh(&flow_cache_gc_lock);
 109         list_splice_tail_init(&flow_cache_gc_list, &gc_list);
 110         spin_unlock_bh(&flow_cache_gc_lock);
 111
 112         list_for_each_entry_safe(fce, n, &gc_list, u.gc_list)
 113                 flow_entry_kill(fce);
 114 }
 115 static DECLARE_WORK(flow_cache_gc_work, flow_cache_gc_task);
 116
 117 static void flow_cache_queue_garbage(struct flow_cache_percpu *fcp,
 118                                      int deleted, struct list_head *gc_list)
 119 {
 120         if (deleted) {
 121                 fcp->hash_count -= deleted;
 122                 spin_lock_bh(&flow_cache_gc_lock);
 123                 list_splice_tail(gc_list, &flow_cache_gc_list);
 124                 spin_unlock_bh(&flow_cache_gc_lock);
 125                 schedule_work(&flow_cache_gc_work);
 126         }
 127 }
 128
 129 static void __flow_cache_shrink(struct flow_cache *fc,
 130                                 struct flow_cache_percpu *fcp,
 131                                 int shrink_to)
 132 {
 133         struct flow_cache_entry *fle;
 134         struct hlist_node *entry, *tmp;
 135         LIST_HEAD(gc_list);
 136         int i, deleted = 0;
 137
 138         for (i = 0; i < flow_cache_hash_size(fc); i++) {
 139                 int saved = 0;
 140
 141                 hlist_for_each_entry_safe(fle, entry, tmp,
 142                                           &fcp->hash_table[i], u.hlist) {
 143                         if (saved < shrink_to &&
 144                             flow_entry_valid(fle)) {
 145                                 saved++;
 146                         } else {
 147                                 deleted++;
 148                                 hlist_del(&fle->u.hlist);
 149                                 list_add_tail(&fle->u.gc_list, &gc_list);
 150                         }
 151                 }
 152         }
 153
 154         flow_cache_queue_garbage(fcp, deleted, &gc_list);
 155 }
 156
 157 static void flow_cache_shrink(struct flow_cache *fc,
 158                               struct flow_cache_percpu *fcp)
 159 {
 160         int shrink_to = fc->low_watermark / flow_cache_hash_size(fc);
 161
 162         __flow_cache_shrink(fc, fcp, shrink_to);
 163 }
 164
 165 static void flow_new_hash_rnd(struct flow_cache *fc,
 166                               struct flow_cache_percpu *fcp)
 167 {
 168         get_random_bytes(&fcp->hash_rnd, sizeof(u32));
 169         fcp->hash_rnd_recalc = 0;
 170         __flow_cache_shrink(fc, fcp, 0);
 171 }
 172
 173 static u32 flow_hash_code(struct flow_cache *fc,
 174                           struct flow_cache_percpu *fcp,
 175                           struct flowi *key)
 176 {
 177         u32 *k = (u32 *) key;
 178
 179         return (jhash2(k, (sizeof(*key) / sizeof(u32)), fcp->hash_rnd)
 180                 & (flow_cache_hash_size(fc) - 1));
 181 }
 182
 183 #if (BITS_PER_LONG == 64)
 184 typedef u64 flow_compare_t;
 185 #else
 186 typedef u32 flow_compare_t;
 187 #endif
 188
 189 /* I hear what you're saying, use memcmp.  But memcmp cannot make
 190  * important assumptions that we can here, such as alignment and
 191  * constant size.
 192  */
 193 static int flow_key_compare(struct flowi *key1, struct flowi *key2)
 194 {
 195         flow_compare_t *k1, *k1_lim, *k2;
 196         const int n_elem = sizeof(struct flowi) / sizeof(flow_compare_t);
 197
 198         BUILD_BUG_ON(sizeof(struct flowi) % sizeof(flow_compare_t));
 199
 200         k1 = (flow_compare_t *) key1;
 201         k1_lim = k1 + n_elem;
 202
 203         k2 = (flow_compare_t *) key2;
 204
 205         do {
 206                 if (*k1++ != *k2++)
 207                         return 1;
 208         } while (k1 < k1_lim);
 209
 210         return 0;
 211 }
 212
 213 struct flow_cache_object *
 214 flow_cache_lookup(struct net *net, struct flowi *key, u16 family, u8 dir,
 215                   flow_resolve_t resolver, void *ctx)
 216 {
 217         struct flow_cache *fc = &flow_cache_global;
 218         struct flow_cache_percpu *fcp;
 219         struct flow_cache_entry *fle, *tfle;
 220         struct hlist_node *entry;
 221         struct flow_cache_object *flo;
 222         unsigned int hash;
 223
 224         local_bh_disable();
 225         fcp = per_cpu_ptr(fc->percpu, smp_processor_id());
 226
 227         fle = NULL;
 228         flo = NULL;
 229         /* Packet really early in init?  Making flow_cache_init a
 230          * pre-smp initcall would solve this.  --RR */
 231         if (!fcp->hash_table)
 232                 goto nocache;
 233
 234         if (fcp->hash_rnd_recalc)
 235                 flow_new_hash_rnd(fc, fcp);
 236
 237         hash = flow_hash_code(fc, fcp, key);
 238         hlist_for_each_entry(tfle, entry, &fcp->hash_table[hash], u.hlist) {
 239                 if (tfle->family == family &&
 240                     tfle->dir == dir &&
 241                     flow_key_compare(key, &tfle->key) == 0) {
 242                         fle = tfle;
 243                         break;
 244                 }
 245         }
 246
 247         if (unlikely(!fle)) {
 248                 if (fcp->hash_count > fc->high_watermark)
 249                         flow_cache_shrink(fc, fcp);
 250
 251                 fle = kmem_cache_alloc(flow_cachep, GFP_ATOMIC);
 252                 if (fle) {
 253                         fle->family = family;
 254                         fle->dir = dir;
 255                         memcpy(&fle->key, key, sizeof(*key));
 256                         fle->object = NULL;
 257                         hlist_add_head(&fle->u.hlist, &fcp->hash_table[hash]);
 258                         fcp->hash_count++;
 259                 }
 260         } else if (likely(fle->genid == atomic_read(&flow_cache_genid))) {
 261                 flo = fle->object;
 262                 if (!flo)
 263                         goto ret_object;
 264                 flo = flo->ops->get(flo);
 265                 if (flo)
 266                         goto ret_object;
 267         } else if (fle->object) {
 268                 flo = fle->object;
 269                 flo->ops->delete(flo);
 270                 fle->object = NULL;
 271         }
 272
 273 nocache:
 274         flo = NULL;
 275         if (fle) {
 276                 flo = fle->object;
 277                 fle->object = NULL;
 278         }
 279         flo = resolver(net, key, family, dir, flo, ctx);
 280         if (fle) {
 281                 fle->genid = atomic_read(&flow_cache_genid);
 282                 if (!IS_ERR(flo))
 283                         fle->object = flo;
 284                 else
 285                         fle->genid--;
 286         } else {
 287                 if (flo && !IS_ERR(flo))
 288                         flo->ops->delete(flo);
 289         }
 290 ret_object:
 291         local_bh_enable();
 292         return flo;
 293 }
 294
 295 static void flow_cache_flush_tasklet(unsigned long data)
 296 {
 297         struct flow_flush_info *info = (void *)data;
 298         struct flow_cache *fc = info->cache;
 299         struct flow_cache_percpu *fcp;
 300         struct flow_cache_entry *fle;
 301         struct hlist_node *entry, *tmp;
 302         LIST_HEAD(gc_list);
 303         int i, deleted = 0;
 304
 305         fcp = per_cpu_ptr(fc->percpu, smp_processor_id());
 306         for (i = 0; i < flow_cache_hash_size(fc); i++) {
 307                 hlist_for_each_entry_safe(fle, entry, tmp,
 308                                           &fcp->hash_table[i], u.hlist) {
 309                         if (flow_entry_valid(fle))
 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);
 319
 320         if (atomic_dec_and_test(&info->cpuleft))
 321                 complete(&info->completion);
 322 }
 323
 324 static void flow_cache_flush_per_cpu(void *data)
 325 {
 326         struct flow_flush_info *info = data;
 327         int cpu;
 328         struct tasklet_struct *tasklet;
 329
 330         cpu = smp_processor_id();
 331         tasklet = &per_cpu_ptr(info->cache->percpu, cpu)->flush_tasklet;
 332         tasklet->data = (unsigned long)info;
 333         tasklet_schedule(tasklet);
 334 }
 335
 336 void flow_cache_flush(void)
 337 {
 338         struct flow_flush_info info;
 339         static DEFINE_MUTEX(flow_flush_sem);
 340
 341         /* Don't want cpus going down or up during this. */
 342         get_online_cpus();
 343         mutex_lock(&flow_flush_sem);
 344         info.cache = &flow_cache_global;
 345         atomic_set(&info.cpuleft, num_online_cpus());
 346         init_completion(&info.completion);
 347
 348         local_bh_disable();
 349         smp_call_function(flow_cache_flush_per_cpu, &info, 0);
 350         flow_cache_flush_tasklet((unsigned long)&info);
 351         local_bh_enable();
 352
 353         wait_for_completion(&info.completion);
 354         mutex_unlock(&flow_flush_sem);
 355         put_online_cpus();
 356 }
 357
 358 static void __init flow_cache_cpu_prepare(struct flow_cache *fc,
 359                                           struct flow_cache_percpu *fcp)
 360 {
 361         fcp->hash_table = (struct hlist_head *)
 362                 __get_free_pages(GFP_KERNEL|__GFP_ZERO, fc->order);
 363         if (!fcp->hash_table)
 364                 panic("NET: failed to allocate flow cache order %lu\n", fc->order);
 365
 366         fcp->hash_rnd_recalc = 1;
 367         fcp->hash_count = 0;
 368         tasklet_init(&fcp->flush_tasklet, flow_cache_flush_tasklet, 0);
 369 }
 370
 371 static int flow_cache_cpu(struct notifier_block *nfb,
 372                           unsigned long action,
 373                           void *hcpu)
 374 {
 375         struct flow_cache *fc = container_of(nfb, struct flow_cache, hotcpu_notifier);
 376         int cpu = (unsigned long) hcpu;
 377         struct flow_cache_percpu *fcp = per_cpu_ptr(fc->percpu, cpu);
 378
 379         if (action == CPU_DEAD || action == CPU_DEAD_FROZEN)
 380                 __flow_cache_shrink(fc, fcp, 0);
 381         return NOTIFY_OK;
 382 }
 383
 384 static int flow_cache_init(struct flow_cache *fc)
 385 {
 386         unsigned long order;
 387         int i;
 388
 389         fc->hash_shift = 10;
 390         fc->low_watermark = 2 * flow_cache_hash_size(fc);
 391         fc->high_watermark = 4 * flow_cache_hash_size(fc);
 392
 393         for (order = 0;
 394              (PAGE_SIZE << order) <
 395                      (sizeof(struct hlist_head)*flow_cache_hash_size(fc));
 396              order++)
 397                 /* NOTHING */;
 398         fc->order = order;
 399         fc->percpu = alloc_percpu(struct flow_cache_percpu);
 400
 401         setup_timer(&fc->rnd_timer, flow_cache_new_hashrnd,
 402                     (unsigned long) fc);
 403         fc->rnd_timer.expires = jiffies + FLOW_HASH_RND_PERIOD;
 404         add_timer(&fc->rnd_timer);
 405
 406         for_each_possible_cpu(i)
 407                 flow_cache_cpu_prepare(fc, per_cpu_ptr(fc->percpu, i));
 408
 409         fc->hotcpu_notifier = (struct notifier_block){
 410                 .notifier_call = flow_cache_cpu,
 411         };
 412         register_hotcpu_notifier(&fc->hotcpu_notifier);
 413
 414         return 0;
 415 }
 416
 417 static int __init flow_cache_init_global(void)
 418 {
 419         flow_cachep = kmem_cache_create("flow_cache",
 420                                         sizeof(struct flow_cache_entry),
 421                                         0, SLAB_PANIC, NULL);
 422
 423         return flow_cache_init(&flow_cache_global);
 424 }
 425
 426 module_init(flow_cache_init_global);
 427
 428 EXPORT_SYMBOL(flow_cache_genid);
 429 EXPORT_SYMBOL(flow_cache_lookup);