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         struct flow_cache_entry         *next;
  30         u16                             family;
  31         u8                              dir;
  32         u32                             genid;
  33         struct flowi                    key;
  34         struct flow_cache_object        *object;
  35 };
  36
  37 struct flow_cache_percpu {
  38         struct flow_cache_entry         **hash_table;
  39         int                             hash_count;
  40         u32                             hash_rnd;
  41         int                             hash_rnd_recalc;
  42         struct tasklet_struct           flush_tasklet;
  43 };
  44
  45 struct flow_flush_info {
  46         struct flow_cache               *cache;
  47         atomic_t                        cpuleft;
  48         struct completion               completion;
  49 };
  50
  51 struct flow_cache {
  52         u32                             hash_shift;
  53         unsigned long                   order;
  54         struct flow_cache_percpu        *percpu;
  55         struct notifier_block           hotcpu_notifier;
  56         int                             low_watermark;
  57         int                             high_watermark;
  58         struct timer_list               rnd_timer;
  59 };
  60
  61 atomic_t flow_cache_genid = ATOMIC_INIT(0);
  62 static struct flow_cache flow_cache_global;
  63 static struct kmem_cache *flow_cachep;
  64
  65 #define flow_cache_hash_size(cache)     (1 << (cache)->hash_shift)
  66 #define FLOW_HASH_RND_PERIOD            (10 * 60 * HZ)
  67
  68 static void flow_cache_new_hashrnd(unsigned long arg)
  69 {
  70         struct flow_cache *fc = (void *) arg;
  71         int i;
  72
  73         for_each_possible_cpu(i)
  74                 per_cpu_ptr(fc->percpu, i)->hash_rnd_recalc = 1;
  75
  76         fc->rnd_timer.expires = jiffies + FLOW_HASH_RND_PERIOD;
  77         add_timer(&fc->rnd_timer);
  78 }
  79
  80 static int flow_entry_valid(struct flow_cache_entry *fle)
  81 {
  82         if (atomic_read(&flow_cache_genid) != fle->genid)
  83                 return 0;
  84         if (fle->object && !fle->object->ops->check(fle->object))
  85                 return 0;
  86         return 1;
  87 }
  88
  89 static void flow_entry_kill(struct flow_cache *fc,
  90                             struct flow_cache_percpu *fcp,
  91                             struct flow_cache_entry *fle)
  92 {
  93         if (fle->object)
  94                 fle->object->ops->delete(fle->object);
  95         kmem_cache_free(flow_cachep, fle);
  96         fcp->hash_count--;
  97 }
  98
  99 static void __flow_cache_shrink(struct flow_cache *fc,
 100                                 struct flow_cache_percpu *fcp,
 101                                 int shrink_to)
 102 {
 103         struct flow_cache_entry *fle, **flp;
 104         int i;
 105
 106         for (i = 0; i < flow_cache_hash_size(fc); i++) {
 107                 int saved = 0;
 108
 109                 flp = &fcp->hash_table[i];
 110                 while ((fle = *flp) != NULL) {
 111                         if (saved < shrink_to &&
 112                             flow_entry_valid(fle)) {
 113                                 saved++;
 114                                 flp = &fle->next;
 115                         } else {
 116                                 *flp = fle->next;
 117                                 flow_entry_kill(fc, fcp, fle);
 118                         }
 119                 }
 120         }
 121 }
 122
 123 static void flow_cache_shrink(struct flow_cache *fc,
 124                               struct flow_cache_percpu *fcp)
 125 {
 126         int shrink_to = fc->low_watermark / flow_cache_hash_size(fc);
 127
 128         __flow_cache_shrink(fc, fcp, shrink_to);
 129 }
 130
 131 static void flow_new_hash_rnd(struct flow_cache *fc,
 132                               struct flow_cache_percpu *fcp)
 133 {
 134         get_random_bytes(&fcp->hash_rnd, sizeof(u32));
 135         fcp->hash_rnd_recalc = 0;
 136         __flow_cache_shrink(fc, fcp, 0);
 137 }
 138
 139 static u32 flow_hash_code(struct flow_cache *fc,
 140                           struct flow_cache_percpu *fcp,
 141                           struct flowi *key)
 142 {
 143         u32 *k = (u32 *) key;
 144
 145         return (jhash2(k, (sizeof(*key) / sizeof(u32)), fcp->hash_rnd)
 146                 & (flow_cache_hash_size(fc) - 1));
 147 }
 148
 149 #if (BITS_PER_LONG == 64)
 150 typedef u64 flow_compare_t;
 151 #else
 152 typedef u32 flow_compare_t;
 153 #endif
 154
 155 /* I hear what you're saying, use memcmp.  But memcmp cannot make
 156  * important assumptions that we can here, such as alignment and
 157  * constant size.
 158  */
 159 static int flow_key_compare(struct flowi *key1, struct flowi *key2)
 160 {
 161         flow_compare_t *k1, *k1_lim, *k2;
 162         const int n_elem = sizeof(struct flowi) / sizeof(flow_compare_t);
 163
 164         BUILD_BUG_ON(sizeof(struct flowi) % sizeof(flow_compare_t));
 165
 166         k1 = (flow_compare_t *) key1;
 167         k1_lim = k1 + n_elem;
 168
 169         k2 = (flow_compare_t *) key2;
 170
 171         do {
 172                 if (*k1++ != *k2++)
 173                         return 1;
 174         } while (k1 < k1_lim);
 175
 176         return 0;
 177 }
 178
 179 struct flow_cache_object *
 180 flow_cache_lookup(struct net *net, struct flowi *key, u16 family, u8 dir,
 181                   flow_resolve_t resolver, void *ctx)
 182 {
 183         struct flow_cache *fc = &flow_cache_global;
 184         struct flow_cache_percpu *fcp;
 185         struct flow_cache_entry *fle, **head;
 186         struct flow_cache_object *flo;
 187         unsigned int hash;
 188
 189         local_bh_disable();
 190         fcp = per_cpu_ptr(fc->percpu, smp_processor_id());
 191
 192         fle = NULL;
 193         flo = NULL;
 194         /* Packet really early in init?  Making flow_cache_init a
 195          * pre-smp initcall would solve this.  --RR */
 196         if (!fcp->hash_table)
 197                 goto nocache;
 198
 199         if (fcp->hash_rnd_recalc)
 200                 flow_new_hash_rnd(fc, fcp);
 201
 202         hash = flow_hash_code(fc, fcp, key);
 203         head = &fcp->hash_table[hash];
 204         for (fle = *head; fle; fle = fle->next) {
 205                 if (fle->family == family &&
 206                     fle->dir == dir &&
 207                     flow_key_compare(key, &fle->key) == 0)
 208                         break;
 209         }
 210
 211         if (unlikely(!fle)) {
 212                 if (fcp->hash_count > fc->high_watermark)
 213                         flow_cache_shrink(fc, fcp);
 214
 215                 fle = kmem_cache_alloc(flow_cachep, GFP_ATOMIC);
 216                 if (fle) {
 217                         fle->next = *head;
 218                         *head = fle;
 219                         fle->family = family;
 220                         fle->dir = dir;
 221                         memcpy(&fle->key, key, sizeof(*key));
 222                         fle->object = NULL;
 223                         fcp->hash_count++;
 224                 }
 225         } else if (likely(fle->genid == atomic_read(&flow_cache_genid))) {
 226                 flo = fle->object;
 227                 if (!flo)
 228                         goto ret_object;
 229                 flo = flo->ops->get(flo);
 230                 if (flo)
 231                         goto ret_object;
 232         } else if (fle->object) {
 233                 flo = fle->object;
 234                 flo->ops->delete(flo);
 235                 fle->object = NULL;
 236         }
 237
 238 nocache:
 239         flo = NULL;
 240         if (fle) {
 241                 flo = fle->object;
 242                 fle->object = NULL;
 243         }
 244         flo = resolver(net, key, family, dir, flo, ctx);
 245         if (fle) {
 246                 fle->genid = atomic_read(&flow_cache_genid);
 247                 if (!IS_ERR(flo))
 248                         fle->object = flo;
 249                 else
 250                         fle->genid--;
 251         } else {
 252                 if (flo && !IS_ERR(flo))
 253                         flo->ops->delete(flo);
 254         }
 255 ret_object:
 256         local_bh_enable();
 257         return flo;
 258 }
 259
 260 static void flow_cache_flush_tasklet(unsigned long data)
 261 {
 262         struct flow_flush_info *info = (void *)data;
 263         struct flow_cache *fc = info->cache;
 264         struct flow_cache_percpu *fcp;
 265         int i;
 266
 267         fcp = per_cpu_ptr(fc->percpu, smp_processor_id());
 268         for (i = 0; i < flow_cache_hash_size(fc); i++) {
 269                 struct flow_cache_entry *fle;
 270
 271                 fle = fcp->hash_table[i];
 272                 for (; fle; fle = fle->next) {
 273                         if (flow_entry_valid(fle))
 274                                 continue;
 275
 276                         if (fle->object)
 277                                 fle->object->ops->delete(fle->object);
 278                         fle->object = NULL;
 279                 }
 280         }
 281
 282         if (atomic_dec_and_test(&info->cpuleft))
 283                 complete(&info->completion);
 284 }
 285
 286 static void flow_cache_flush_per_cpu(void *data)
 287 {
 288         struct flow_flush_info *info = data;
 289         int cpu;
 290         struct tasklet_struct *tasklet;
 291
 292         cpu = smp_processor_id();
 293         tasklet = &per_cpu_ptr(info->cache->percpu, cpu)->flush_tasklet;
 294         tasklet->data = (unsigned long)info;
 295         tasklet_schedule(tasklet);
 296 }
 297
 298 void flow_cache_flush(void)
 299 {
 300         struct flow_flush_info info;
 301         static DEFINE_MUTEX(flow_flush_sem);
 302
 303         /* Don't want cpus going down or up during this. */
 304         get_online_cpus();
 305         mutex_lock(&flow_flush_sem);
 306         info.cache = &flow_cache_global;
 307         atomic_set(&info.cpuleft, num_online_cpus());
 308         init_completion(&info.completion);
 309
 310         local_bh_disable();
 311         smp_call_function(flow_cache_flush_per_cpu, &info, 0);
 312         flow_cache_flush_tasklet((unsigned long)&info);
 313         local_bh_enable();
 314
 315         wait_for_completion(&info.completion);
 316         mutex_unlock(&flow_flush_sem);
 317         put_online_cpus();
 318 }
 319
 320 static void __init flow_cache_cpu_prepare(struct flow_cache *fc,
 321                                           struct flow_cache_percpu *fcp)
 322 {
 323         fcp->hash_table = (struct flow_cache_entry **)
 324                 __get_free_pages(GFP_KERNEL|__GFP_ZERO, fc->order);
 325         if (!fcp->hash_table)
 326                 panic("NET: failed to allocate flow cache order %lu\n", fc->order);
 327
 328         fcp->hash_rnd_recalc = 1;
 329         fcp->hash_count = 0;
 330         tasklet_init(&fcp->flush_tasklet, flow_cache_flush_tasklet, 0);
 331 }
 332
 333 static int flow_cache_cpu(struct notifier_block *nfb,
 334                           unsigned long action,
 335                           void *hcpu)
 336 {
 337         struct flow_cache *fc = container_of(nfb, struct flow_cache, hotcpu_notifier);
 338         int cpu = (unsigned long) hcpu;
 339         struct flow_cache_percpu *fcp = per_cpu_ptr(fc->percpu, cpu);
 340
 341         if (action == CPU_DEAD || action == CPU_DEAD_FROZEN)
 342                 __flow_cache_shrink(fc, fcp, 0);
 343         return NOTIFY_OK;
 344 }
 345
 346 static int flow_cache_init(struct flow_cache *fc)
 347 {
 348         unsigned long order;
 349         int i;
 350
 351         fc->hash_shift = 10;
 352         fc->low_watermark = 2 * flow_cache_hash_size(fc);
 353         fc->high_watermark = 4 * flow_cache_hash_size(fc);
 354
 355         for (order = 0;
 356              (PAGE_SIZE << order) <
 357                      (sizeof(struct flow_cache_entry *)*flow_cache_hash_size(fc));
 358              order++)
 359                 /* NOTHING */;
 360         fc->order = order;
 361         fc->percpu = alloc_percpu(struct flow_cache_percpu);
 362
 363         setup_timer(&fc->rnd_timer, flow_cache_new_hashrnd,
 364                     (unsigned long) fc);
 365         fc->rnd_timer.expires = jiffies + FLOW_HASH_RND_PERIOD;
 366         add_timer(&fc->rnd_timer);
 367
 368         for_each_possible_cpu(i)
 369                 flow_cache_cpu_prepare(fc, per_cpu_ptr(fc->percpu, i));
 370
 371         fc->hotcpu_notifier = (struct notifier_block){
 372                 .notifier_call = flow_cache_cpu,
 373         };
 374         register_hotcpu_notifier(&fc->hotcpu_notifier);
 375
 376         return 0;
 377 }
 378
 379 static int __init flow_cache_init_global(void)
 380 {
 381         flow_cachep = kmem_cache_create("flow_cache",
 382                                         sizeof(struct flow_cache_entry),
 383                                         0, SLAB_PANIC, NULL);
 384
 385         return flow_cache_init(&flow_cache_global);
 386 }
 387
 388 module_init(flow_cache_init_global);
 389
 390 EXPORT_SYMBOL(flow_cache_genid);
 391 EXPORT_SYMBOL(flow_cache_lookup);