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 <asm/semaphore.h>
  27 #include <linux/security.h>
  28
  29 struct flow_cache_entry {
  30         struct flow_cache_entry *next;
  31         u16                     family;
  32         u8                      dir;
  33         struct flowi            key;
  34         u32                     genid;
  35         u32                     sk_sid;
  36         void                    *object;
  37         atomic_t                *object_ref;
  38 };
  39
  40 atomic_t flow_cache_genid = ATOMIC_INIT(0);
  41
  42 static u32 flow_hash_shift;
  43 #define flow_hash_size  (1 << flow_hash_shift)
  44 static DEFINE_PER_CPU(struct flow_cache_entry **, flow_tables) = { NULL };
  45
  46 #define flow_table(cpu) (per_cpu(flow_tables, cpu))
  47
  48 static kmem_cache_t *flow_cachep __read_mostly;
  49
  50 static int flow_lwm, flow_hwm;
  51
  52 struct flow_percpu_info {
  53         int hash_rnd_recalc;
  54         u32 hash_rnd;
  55         int count;
  56 } ____cacheline_aligned;
  57 static DEFINE_PER_CPU(struct flow_percpu_info, flow_hash_info) = { 0 };
  58
  59 #define flow_hash_rnd_recalc(cpu) \
  60         (per_cpu(flow_hash_info, cpu).hash_rnd_recalc)
  61 #define flow_hash_rnd(cpu) \
  62         (per_cpu(flow_hash_info, cpu).hash_rnd)
  63 #define flow_count(cpu) \
  64         (per_cpu(flow_hash_info, cpu).count)
  65
  66 static struct timer_list flow_hash_rnd_timer;
  67
  68 #define FLOW_HASH_RND_PERIOD    (10 * 60 * HZ)
  69
  70 struct flow_flush_info {
  71         atomic_t cpuleft;
  72         struct completion completion;
  73 };
  74 static DEFINE_PER_CPU(struct tasklet_struct, flow_flush_tasklets) = { NULL };
  75
  76 #define flow_flush_tasklet(cpu) (&per_cpu(flow_flush_tasklets, cpu))
  77
  78 static void flow_cache_new_hashrnd(unsigned long arg)
  79 {
  80         int i;
  81
  82         for_each_possible_cpu(i)
  83                 flow_hash_rnd_recalc(i) = 1;
  84
  85         flow_hash_rnd_timer.expires = jiffies + FLOW_HASH_RND_PERIOD;
  86         add_timer(&flow_hash_rnd_timer);
  87 }
  88
  89 static void __flow_cache_shrink(int cpu, int shrink_to)
  90 {
  91         struct flow_cache_entry *fle, **flp;
  92         int i;
  93
  94         for (i = 0; i < flow_hash_size; i++) {
  95                 int k = 0;
  96
  97                 flp = &flow_table(cpu)[i];
  98                 while ((fle = *flp) != NULL && k < shrink_to) {
  99                         k++;
 100                         flp = &fle->next;
 101                 }
 102                 while ((fle = *flp) != NULL) {
 103                         *flp = fle->next;
 104                         if (fle->object)
 105                                 atomic_dec(fle->object_ref);
 106                         kmem_cache_free(flow_cachep, fle);
 107                         flow_count(cpu)--;
 108                 }
 109         }
 110 }
 111
 112 static void flow_cache_shrink(int cpu)
 113 {
 114         int shrink_to = flow_lwm / flow_hash_size;
 115
 116         __flow_cache_shrink(cpu, shrink_to);
 117 }
 118
 119 static void flow_new_hash_rnd(int cpu)
 120 {
 121         get_random_bytes(&flow_hash_rnd(cpu), sizeof(u32));
 122         flow_hash_rnd_recalc(cpu) = 0;
 123
 124         __flow_cache_shrink(cpu, 0);
 125 }
 126
 127 static u32 flow_hash_code(struct flowi *key, int cpu)
 128 {
 129         u32 *k = (u32 *) key;
 130
 131         return (jhash2(k, (sizeof(*key) / sizeof(u32)), flow_hash_rnd(cpu)) &
 132                 (flow_hash_size - 1));
 133 }
 134
 135 #if (BITS_PER_LONG == 64)
 136 typedef u64 flow_compare_t;
 137 #else
 138 typedef u32 flow_compare_t;
 139 #endif
 140
 141 extern void flowi_is_missized(void);
 142
 143 /* I hear what you're saying, use memcmp.  But memcmp cannot make
 144  * important assumptions that we can here, such as alignment and
 145  * constant size.
 146  */
 147 static int flow_key_compare(struct flowi *key1, struct flowi *key2)
 148 {
 149         flow_compare_t *k1, *k1_lim, *k2;
 150         const int n_elem = sizeof(struct flowi) / sizeof(flow_compare_t);
 151
 152         if (sizeof(struct flowi) % sizeof(flow_compare_t))
 153                 flowi_is_missized();
 154
 155         k1 = (flow_compare_t *) key1;
 156         k1_lim = k1 + n_elem;
 157
 158         k2 = (flow_compare_t *) key2;
 159
 160         do {
 161                 if (*k1++ != *k2++)
 162                         return 1;
 163         } while (k1 < k1_lim);
 164
 165         return 0;
 166 }
 167
 168 void *flow_cache_lookup(struct flowi *key, u32 sk_sid, u16 family, u8 dir,
 169                         flow_resolve_t resolver)
 170 {
 171         struct flow_cache_entry *fle, **head;
 172         unsigned int hash;
 173         int cpu;
 174
 175         local_bh_disable();
 176         cpu = smp_processor_id();
 177
 178         fle = NULL;
 179         /* Packet really early in init?  Making flow_cache_init a
 180          * pre-smp initcall would solve this.  --RR */
 181         if (!flow_table(cpu))
 182                 goto nocache;
 183
 184         if (flow_hash_rnd_recalc(cpu))
 185                 flow_new_hash_rnd(cpu);
 186         hash = flow_hash_code(key, cpu);
 187
 188         head = &flow_table(cpu)[hash];
 189         for (fle = *head; fle; fle = fle->next) {
 190                 if (fle->family == family &&
 191                     fle->dir == dir &&
 192                     fle->sk_sid == sk_sid &&
 193                     flow_key_compare(key, &fle->key) == 0) {
 194                         if (fle->genid == atomic_read(&flow_cache_genid)) {
 195                                 void *ret = fle->object;
 196
 197                                 if (ret)
 198                                         atomic_inc(fle->object_ref);
 199                                 local_bh_enable();
 200
 201                                 return ret;
 202                         }
 203                         break;
 204                 }
 205         }
 206
 207         if (!fle) {
 208                 if (flow_count(cpu) > flow_hwm)
 209                         flow_cache_shrink(cpu);
 210
 211                 fle = kmem_cache_alloc(flow_cachep, SLAB_ATOMIC);
 212                 if (fle) {
 213                         fle->next = *head;
 214                         *head = fle;
 215                         fle->family = family;
 216                         fle->dir = dir;
 217                         fle->sk_sid = sk_sid;
 218                         memcpy(&fle->key, key, sizeof(*key));
 219                         fle->object = NULL;
 220                         flow_count(cpu)++;
 221                 }
 222         }
 223
 224 nocache:
 225         {
 226                 void *obj;
 227                 atomic_t *obj_ref;
 228
 229                 resolver(key, sk_sid, family, dir, &obj, &obj_ref);
 230
 231                 if (fle) {
 232                         fle->genid = atomic_read(&flow_cache_genid);
 233
 234                         if (fle->object)
 235                                 atomic_dec(fle->object_ref);
 236
 237                         fle->object = obj;
 238                         fle->object_ref = obj_ref;
 239                         if (obj)
 240                                 atomic_inc(fle->object_ref);
 241                 }
 242                 local_bh_enable();
 243
 244                 return obj;
 245         }
 246 }
 247
 248 static void flow_cache_flush_tasklet(unsigned long data)
 249 {
 250         struct flow_flush_info *info = (void *)data;
 251         int i;
 252         int cpu;
 253
 254         cpu = smp_processor_id();
 255         for (i = 0; i < flow_hash_size; i++) {
 256                 struct flow_cache_entry *fle;
 257
 258                 fle = flow_table(cpu)[i];
 259                 for (; fle; fle = fle->next) {
 260                         unsigned genid = atomic_read(&flow_cache_genid);
 261
 262                         if (!fle->object || fle->genid == genid)
 263                                 continue;
 264
 265                         fle->object = NULL;
 266                         atomic_dec(fle->object_ref);
 267                 }
 268         }
 269
 270         if (atomic_dec_and_test(&info->cpuleft))
 271                 complete(&info->completion);
 272 }
 273
 274 static void flow_cache_flush_per_cpu(void *) __attribute__((__unused__));
 275 static void flow_cache_flush_per_cpu(void *data)
 276 {
 277         struct flow_flush_info *info = data;
 278         int cpu;
 279         struct tasklet_struct *tasklet;
 280
 281         cpu = smp_processor_id();
 282
 283         tasklet = flow_flush_tasklet(cpu);
 284         tasklet->data = (unsigned long)info;
 285         tasklet_schedule(tasklet);
 286 }
 287
 288 void flow_cache_flush(void)
 289 {
 290         struct flow_flush_info info;
 291         static DEFINE_MUTEX(flow_flush_sem);
 292
 293         /* Don't want cpus going down or up during this. */
 294         lock_cpu_hotplug();
 295         mutex_lock(&flow_flush_sem);
 296         atomic_set(&info.cpuleft, num_online_cpus());
 297         init_completion(&info.completion);
 298
 299         local_bh_disable();
 300         smp_call_function(flow_cache_flush_per_cpu, &info, 1, 0);
 301         flow_cache_flush_tasklet((unsigned long)&info);
 302         local_bh_enable();
 303
 304         wait_for_completion(&info.completion);
 305         mutex_unlock(&flow_flush_sem);
 306         unlock_cpu_hotplug();
 307 }
 308
 309 static void __devinit flow_cache_cpu_prepare(int cpu)
 310 {
 311         struct tasklet_struct *tasklet;
 312         unsigned long order;
 313
 314         for (order = 0;
 315              (PAGE_SIZE << order) <
 316                      (sizeof(struct flow_cache_entry *)*flow_hash_size);
 317              order++)
 318                 /* NOTHING */;
 319
 320         flow_table(cpu) = (struct flow_cache_entry **)
 321                 __get_free_pages(GFP_KERNEL|__GFP_ZERO, order);
 322         if (!flow_table(cpu))
 323                 panic("NET: failed to allocate flow cache order %lu\n", order);
 324
 325         flow_hash_rnd_recalc(cpu) = 1;
 326         flow_count(cpu) = 0;
 327
 328         tasklet = flow_flush_tasklet(cpu);
 329         tasklet_init(tasklet, flow_cache_flush_tasklet, 0);
 330 }
 331
 332 #ifdef CONFIG_HOTPLUG_CPU
 333 static int flow_cache_cpu(struct notifier_block *nfb,
 334                           unsigned long action,
 335                           void *hcpu)
 336 {
 337         if (action == CPU_DEAD)
 338                 __flow_cache_shrink((unsigned long)hcpu, 0);
 339         return NOTIFY_OK;
 340 }
 341 #endif /* CONFIG_HOTPLUG_CPU */
 342
 343 static int __init flow_cache_init(void)
 344 {
 345         int i;
 346
 347         flow_cachep = kmem_cache_create("flow_cache",
 348                                         sizeof(struct flow_cache_entry),
 349                                         0, SLAB_HWCACHE_ALIGN,
 350                                         NULL, NULL);
 351
 352         if (!flow_cachep)
 353                 panic("NET: failed to allocate flow cache slab\n");
 354
 355         flow_hash_shift = 10;
 356         flow_lwm = 2 * flow_hash_size;
 357         flow_hwm = 4 * flow_hash_size;
 358
 359         init_timer(&flow_hash_rnd_timer);
 360         flow_hash_rnd_timer.function = flow_cache_new_hashrnd;
 361         flow_hash_rnd_timer.expires = jiffies + FLOW_HASH_RND_PERIOD;
 362         add_timer(&flow_hash_rnd_timer);
 363
 364         for_each_possible_cpu(i)
 365                 flow_cache_cpu_prepare(i);
 366
 367         hotcpu_notifier(flow_cache_cpu, 0);
 368         return 0;
 369 }
 370
 371 module_init(flow_cache_init);
 372
 373 EXPORT_SYMBOL(flow_cache_genid);
 374 EXPORT_SYMBOL(flow_cache_lookup);