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         struct flow_cache_percpu __percpu *percpu;
  57         struct notifier_block           hotcpu_notifier;
  58         int                             low_watermark;
  59         int                             high_watermark;
  60         struct timer_list               rnd_timer;
  61 };
  62
  63 atomic_t flow_cache_genid = ATOMIC_INIT(0);
  64 EXPORT_SYMBOL(flow_cache_genid);
  65 static struct flow_cache flow_cache_global;
  66 static struct kmem_cache *flow_cachep __read_mostly;
  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 typedef unsigned long flow_compare_t;
 184
 185 /* I hear what you're saying, use memcmp.  But memcmp cannot make
 186  * important assumptions that we can here, such as alignment and
 187  * constant size.
 188  */
 189 static int flow_key_compare(struct flowi *key1, struct flowi *key2)
 190 {
 191         flow_compare_t *k1, *k1_lim, *k2;
 192         const int n_elem = sizeof(struct flowi) / sizeof(flow_compare_t);
 193
 194         BUILD_BUG_ON(sizeof(struct flowi) % sizeof(flow_compare_t));
 195
 196         k1 = (flow_compare_t *) key1;
 197         k1_lim = k1 + n_elem;
 198
 199         k2 = (flow_compare_t *) key2;
 200
 201         do {
 202                 if (*k1++ != *k2++)
 203                         return 1;
 204         } while (k1 < k1_lim);
 205
 206         return 0;
 207 }
 208
 209 struct flow_cache_object *
 210 flow_cache_lookup(struct net *net, struct flowi *key, u16 family, u8 dir,
 211                   flow_resolve_t resolver, void *ctx)
 212 {
 213         struct flow_cache *fc = &flow_cache_global;
 214         struct flow_cache_percpu *fcp;
 215         struct flow_cache_entry *fle, *tfle;
 216         struct hlist_node *entry;
 217         struct flow_cache_object *flo;
 218         unsigned int hash;
 219
 220         local_bh_disable();
 221         fcp = this_cpu_ptr(fc->percpu);
 222
 223         fle = NULL;
 224         flo = NULL;
 225         /* Packet really early in init?  Making flow_cache_init a
 226          * pre-smp initcall would solve this.  --RR */
 227         if (!fcp->hash_table)
 228                 goto nocache;
 229
 230         if (fcp->hash_rnd_recalc)
 231                 flow_new_hash_rnd(fc, fcp);
 232
 233         hash = flow_hash_code(fc, fcp, key);
 234         hlist_for_each_entry(tfle, entry, &fcp->hash_table[hash], u.hlist) {
 235                 if (tfle->family == family &&
 236                     tfle->dir == dir &&
 237                     flow_key_compare(key, &tfle->key) == 0) {
 238                         fle = tfle;
 239                         break;
 240                 }
 241         }
 242
 243         if (unlikely(!fle)) {
 244                 if (fcp->hash_count > fc->high_watermark)
 245                         flow_cache_shrink(fc, fcp);
 246
 247                 fle = kmem_cache_alloc(flow_cachep, GFP_ATOMIC);
 248                 if (fle) {
 249                         fle->family = family;
 250                         fle->dir = dir;
 251                         memcpy(&fle->key, key, sizeof(*key));
 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(&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(&flow_cache_genid);
 278                 if (!IS_ERR(flo))
 279                         fle->object = flo;
 280                 else
 281                         fle->genid--;
 282         } else {
 283                 if (flo && !IS_ERR(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 *entry, *tmp;
 299         LIST_HEAD(gc_list);
 300         int i, deleted = 0;
 301
 302         fcp = this_cpu_ptr(fc->percpu);
 303         for (i = 0; i < flow_cache_hash_size(fc); i++) {
 304                 hlist_for_each_entry_safe(fle, entry, tmp,
 305                                           &fcp->hash_table[i], u.hlist) {
 306                         if (flow_entry_valid(fle))
 307                                 continue;
 308
 309                         deleted++;
 310                         hlist_del(&fle->u.hlist);
 311                         list_add_tail(&fle->u.gc_list, &gc_list);
 312                 }
 313         }
 314
 315         flow_cache_queue_garbage(fcp, deleted, &gc_list);
 316
 317         if (atomic_dec_and_test(&info->cpuleft))
 318                 complete(&info->completion);
 319 }
 320
 321 static void flow_cache_flush_per_cpu(void *data)
 322 {
 323         struct flow_flush_info *info = data;
 324         int cpu;
 325         struct tasklet_struct *tasklet;
 326
 327         cpu = smp_processor_id();
 328         tasklet = &per_cpu_ptr(info->cache->percpu, cpu)->flush_tasklet;
 329         tasklet->data = (unsigned long)info;
 330         tasklet_schedule(tasklet);
 331 }
 332
 333 void flow_cache_flush(void)
 334 {
 335         struct flow_flush_info info;
 336         static DEFINE_MUTEX(flow_flush_sem);
 337
 338         /* Don't want cpus going down or up during this. */
 339         get_online_cpus();
 340         mutex_lock(&flow_flush_sem);
 341         info.cache = &flow_cache_global;
 342         atomic_set(&info.cpuleft, num_online_cpus());
 343         init_completion(&info.completion);
 344
 345         local_bh_disable();
 346         smp_call_function(flow_cache_flush_per_cpu, &info, 0);
 347         flow_cache_flush_tasklet((unsigned long)&info);
 348         local_bh_enable();
 349
 350         wait_for_completion(&info.completion);
 351         mutex_unlock(&flow_flush_sem);
 352         put_online_cpus();
 353 }
 354
 355 static int __cpuinit flow_cache_cpu_prepare(struct flow_cache *fc, int cpu)
 356 {
 357         struct flow_cache_percpu *fcp = per_cpu_ptr(fc->percpu, cpu);
 358         size_t sz = sizeof(struct hlist_head) * flow_cache_hash_size(fc);
 359
 360         if (!fcp->hash_table) {
 361                 fcp->hash_table = kzalloc_node(sz, GFP_KERNEL, cpu_to_node(cpu));
 362                 if (!fcp->hash_table) {
 363                         pr_err("NET: failed to allocate flow cache sz %zu\n", sz);
 364                         return -ENOMEM;
 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         return 0;
 371 }
 372
 373 static int __cpuinit flow_cache_cpu(struct notifier_block *nfb,
 374                           unsigned long action,
 375                           void *hcpu)
 376 {
 377         struct flow_cache *fc = container_of(nfb, struct flow_cache, hotcpu_notifier);
 378         int res, cpu = (unsigned long) hcpu;
 379         struct flow_cache_percpu *fcp = per_cpu_ptr(fc->percpu, cpu);
 380
 381         switch (action) {
 382         case CPU_UP_PREPARE:
 383         case CPU_UP_PREPARE_FROZEN:
 384                 res = flow_cache_cpu_prepare(fc, cpu);
 385                 if (res)
 386                         return notifier_from_errno(res);
 387                 break;
 388         case CPU_DEAD:
 389         case CPU_DEAD_FROZEN:
 390                 __flow_cache_shrink(fc, fcp, 0);
 391                 break;
 392         }
 393         return NOTIFY_OK;
 394 }
 395
 396 static int __init flow_cache_init(struct flow_cache *fc)
 397 {
 398         int i;
 399
 400         fc->hash_shift = 10;
 401         fc->low_watermark = 2 * flow_cache_hash_size(fc);
 402         fc->high_watermark = 4 * flow_cache_hash_size(fc);
 403
 404         fc->percpu = alloc_percpu(struct flow_cache_percpu);
 405         if (!fc->percpu)
 406                 return -ENOMEM;
 407
 408         for_each_online_cpu(i) {
 409                 if (flow_cache_cpu_prepare(fc, i))
 410                         return -ENOMEM;
 411         }
 412         fc->hotcpu_notifier = (struct notifier_block){
 413                 .notifier_call = flow_cache_cpu,
 414         };
 415         register_hotcpu_notifier(&fc->hotcpu_notifier);
 416
 417         setup_timer(&fc->rnd_timer, flow_cache_new_hashrnd,
 418                     (unsigned long) fc);
 419         fc->rnd_timer.expires = jiffies + FLOW_HASH_RND_PERIOD;
 420         add_timer(&fc->rnd_timer);
 421
 422         return 0;
 423 }
 424
 425 static int __init flow_cache_init_global(void)
 426 {
 427         flow_cachep = kmem_cache_create("flow_cache",
 428                                         sizeof(struct flow_cache_entry),
 429                                         0, SLAB_PANIC, NULL);
 430
 431         return flow_cache_init(&flow_cache_global);
 432 }
 433
 434 module_init(flow_cache_init_global);