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                           const struct flowi *key,
 176                           size_t keysize)
 177 {
 178         const u32 *k = (const u32 *) key;
 179         const u32 length = keysize * sizeof(flow_compare_t) / sizeof(u32);
 180
 181         return jhash2(k, length, fcp->hash_rnd)
 182                 & (flow_cache_hash_size(fc) - 1);
 183 }
 184
 185 /* I hear what you're saying, use memcmp.  But memcmp cannot make
 186  * important assumptions that we can here, such as alignment.
 187  */
 188 static int flow_key_compare(const struct flowi *key1, const struct flowi *key2,
 189                             size_t keysize)
 190 {
 191         const flow_compare_t *k1, *k1_lim, *k2;
 192
 193         k1 = (const flow_compare_t *) key1;
 194         k1_lim = k1 + keysize;
 195
 196         k2 = (const flow_compare_t *) key2;
 197
 198         do {
 199                 if (*k1++ != *k2++)
 200                         return 1;
 201         } while (k1 < k1_lim);
 202
 203         return 0;
 204 }
 205
 206 struct flow_cache_object *
 207 flow_cache_lookup(struct net *net, const struct flowi *key, u16 family, u8 dir,
 208                   flow_resolve_t resolver, void *ctx)
 209 {
 210         struct flow_cache *fc = &flow_cache_global;
 211         struct flow_cache_percpu *fcp;
 212         struct flow_cache_entry *fle, *tfle;
 213         struct hlist_node *entry;
 214         struct flow_cache_object *flo;
 215         size_t keysize;
 216         unsigned int hash;
 217
 218         local_bh_disable();
 219         fcp = this_cpu_ptr(fc->percpu);
 220
 221         fle = NULL;
 222         flo = NULL;
 223
 224         keysize = flow_key_size(family);
 225         if (!keysize)
 226                 goto nocache;
 227
 228         /* Packet really early in init?  Making flow_cache_init a
 229          * pre-smp initcall would solve this.  --RR */
 230         if (!fcp->hash_table)
 231                 goto nocache;
 232
 233         if (fcp->hash_rnd_recalc)
 234                 flow_new_hash_rnd(fc, fcp);
 235
 236         hash = flow_hash_code(fc, fcp, key, keysize);
 237         hlist_for_each_entry(tfle, entry, &fcp->hash_table[hash], u.hlist) {
 238                 if (tfle->family == family &&
 239                     tfle->dir == dir &&
 240                     flow_key_compare(key, &tfle->key, keysize) == 0) {
 241                         fle = tfle;
 242                         break;
 243                 }
 244         }
 245
 246         if (unlikely(!fle)) {
 247                 if (fcp->hash_count > fc->high_watermark)
 248                         flow_cache_shrink(fc, fcp);
 249
 250                 fle = kmem_cache_alloc(flow_cachep, GFP_ATOMIC);
 251                 if (fle) {
 252                         fle->family = family;
 253                         fle->dir = dir;
 254                         memcpy(&fle->key, key, keysize * sizeof(flow_compare_t));
 255                         fle->object = NULL;
 256                         hlist_add_head(&fle->u.hlist, &fcp->hash_table[hash]);
 257                         fcp->hash_count++;
 258                 }
 259         } else if (likely(fle->genid == atomic_read(&flow_cache_genid))) {
 260                 flo = fle->object;
 261                 if (!flo)
 262                         goto ret_object;
 263                 flo = flo->ops->get(flo);
 264                 if (flo)
 265                         goto ret_object;
 266         } else if (fle->object) {
 267                 flo = fle->object;
 268                 flo->ops->delete(flo);
 269                 fle->object = NULL;
 270         }
 271
 272 nocache:
 273         flo = NULL;
 274         if (fle) {
 275                 flo = fle->object;
 276                 fle->object = NULL;
 277         }
 278         flo = resolver(net, key, family, dir, flo, ctx);
 279         if (fle) {
 280                 fle->genid = atomic_read(&flow_cache_genid);
 281                 if (!IS_ERR(flo))
 282                         fle->object = flo;
 283                 else
 284                         fle->genid--;
 285         } else {
 286                 if (flo && !IS_ERR(flo))
 287                         flo->ops->delete(flo);
 288         }
 289 ret_object:
 290         local_bh_enable();
 291         return flo;
 292 }
 293 EXPORT_SYMBOL(flow_cache_lookup);
 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 = this_cpu_ptr(fc->percpu);
 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 int __cpuinit flow_cache_cpu_prepare(struct flow_cache *fc, int cpu)
 359 {
 360         struct flow_cache_percpu *fcp = per_cpu_ptr(fc->percpu, cpu);
 361         size_t sz = sizeof(struct hlist_head) * flow_cache_hash_size(fc);
 362
 363         if (!fcp->hash_table) {
 364                 fcp->hash_table = kzalloc_node(sz, GFP_KERNEL, cpu_to_node(cpu));
 365                 if (!fcp->hash_table) {
 366                         pr_err("NET: failed to allocate flow cache sz %zu\n", sz);
 367                         return -ENOMEM;
 368                 }
 369                 fcp->hash_rnd_recalc = 1;
 370                 fcp->hash_count = 0;
 371                 tasklet_init(&fcp->flush_tasklet, flow_cache_flush_tasklet, 0);
 372         }
 373         return 0;
 374 }
 375
 376 static int __cpuinit flow_cache_cpu(struct notifier_block *nfb,
 377                           unsigned long action,
 378                           void *hcpu)
 379 {
 380         struct flow_cache *fc = container_of(nfb, struct flow_cache, hotcpu_notifier);
 381         int res, cpu = (unsigned long) hcpu;
 382         struct flow_cache_percpu *fcp = per_cpu_ptr(fc->percpu, cpu);
 383
 384         switch (action) {
 385         case CPU_UP_PREPARE:
 386         case CPU_UP_PREPARE_FROZEN:
 387                 res = flow_cache_cpu_prepare(fc, cpu);
 388                 if (res)
 389                         return notifier_from_errno(res);
 390                 break;
 391         case CPU_DEAD:
 392         case CPU_DEAD_FROZEN:
 393                 __flow_cache_shrink(fc, fcp, 0);
 394                 break;
 395         }
 396         return NOTIFY_OK;
 397 }
 398
 399 static int __init flow_cache_init(struct flow_cache *fc)
 400 {
 401         int i;
 402
 403         fc->hash_shift = 10;
 404         fc->low_watermark = 2 * flow_cache_hash_size(fc);
 405         fc->high_watermark = 4 * flow_cache_hash_size(fc);
 406
 407         fc->percpu = alloc_percpu(struct flow_cache_percpu);
 408         if (!fc->percpu)
 409                 return -ENOMEM;
 410
 411         for_each_online_cpu(i) {
 412                 if (flow_cache_cpu_prepare(fc, i))
 413                         return -ENOMEM;
 414         }
 415         fc->hotcpu_notifier = (struct notifier_block){
 416                 .notifier_call = flow_cache_cpu,
 417         };
 418         register_hotcpu_notifier(&fc->hotcpu_notifier);
 419
 420         setup_timer(&fc->rnd_timer, flow_cache_new_hashrnd,
 421                     (unsigned long) fc);
 422         fc->rnd_timer.expires = jiffies + FLOW_HASH_RND_PERIOD;
 423         add_timer(&fc->rnd_timer);
 424
 425         return 0;
 426 }
 427
 428 static int __init flow_cache_init_global(void)
 429 {
 430         flow_cachep = kmem_cache_create("flow_cache",
 431                                         sizeof(struct flow_cache_entry),
 432                                         0, SLAB_PANIC, NULL);
 433
 434         return flow_cache_init(&flow_cache_global);
 435 }
 436
 437 module_init(flow_cache_init_global);