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