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         void                    *object;
  35         atomic_t                *object_ref;
  36 };
  37
  38 atomic_t flow_cache_genid = ATOMIC_INIT(0);
  39
  40 static u32 flow_hash_shift;
  41 #define flow_hash_size  (1 << flow_hash_shift)
  42 static DEFINE_PER_CPU(struct flow_cache_entry **, flow_tables) = { NULL };
  43
  44 #define flow_table(cpu) (per_cpu(flow_tables, cpu))
  45
  46 static struct kmem_cache *flow_cachep __read_mostly;
  47
  48 static int flow_lwm, flow_hwm;
  49
  50 struct flow_percpu_info {
  51         int hash_rnd_recalc;
  52         u32 hash_rnd;
  53         int count;
  54 };
  55 static DEFINE_PER_CPU(struct flow_percpu_info, flow_hash_info) = { 0 };
  56
  57 #define flow_hash_rnd_recalc(cpu) \
  58         (per_cpu(flow_hash_info, cpu).hash_rnd_recalc)
  59 #define flow_hash_rnd(cpu) \
  60         (per_cpu(flow_hash_info, cpu).hash_rnd)
  61 #define flow_count(cpu) \
  62         (per_cpu(flow_hash_info, cpu).count)
  63
  64 static struct timer_list flow_hash_rnd_timer;
  65
  66 #define FLOW_HASH_RND_PERIOD    (10 * 60 * HZ)
  67
  68 struct flow_flush_info {
  69         atomic_t cpuleft;
  70         struct completion completion;
  71 };
  72 static DEFINE_PER_CPU(struct tasklet_struct, flow_flush_tasklets) = { NULL };
  73
  74 #define flow_flush_tasklet(cpu) (&per_cpu(flow_flush_tasklets, cpu))
  75
  76 static void flow_cache_new_hashrnd(unsigned long arg)
  77 {
  78         int i;
  79
  80         for_each_possible_cpu(i)
  81                 flow_hash_rnd_recalc(i) = 1;
  82
  83         flow_hash_rnd_timer.expires = jiffies + FLOW_HASH_RND_PERIOD;
  84         add_timer(&flow_hash_rnd_timer);
  85 }
  86
  87 static void flow_entry_kill(int cpu, struct flow_cache_entry *fle)
  88 {
  89         if (fle->object)
  90                 atomic_dec(fle->object_ref);
  91         kmem_cache_free(flow_cachep, fle);
  92         flow_count(cpu)--;
  93 }
  94
  95 static void __flow_cache_shrink(int cpu, int shrink_to)
  96 {
  97         struct flow_cache_entry *fle, **flp;
  98         int i;
  99
 100         for (i = 0; i < flow_hash_size; i++) {
 101                 int k = 0;
 102
 103                 flp = &flow_table(cpu)[i];
 104                 while ((fle = *flp) != NULL && k < shrink_to) {
 105                         k++;
 106                         flp = &fle->next;
 107                 }
 108                 while ((fle = *flp) != NULL) {
 109                         *flp = fle->next;
 110                         flow_entry_kill(cpu, fle);
 111                 }
 112         }
 113 }
 114
 115 static void flow_cache_shrink(int cpu)
 116 {
 117         int shrink_to = flow_lwm / flow_hash_size;
 118
 119         __flow_cache_shrink(cpu, shrink_to);
 120 }
 121
 122 static void flow_new_hash_rnd(int cpu)
 123 {
 124         get_random_bytes(&flow_hash_rnd(cpu), sizeof(u32));
 125         flow_hash_rnd_recalc(cpu) = 0;
 126
 127         __flow_cache_shrink(cpu, 0);
 128 }
 129
 130 static u32 flow_hash_code(struct flowi *key, int cpu)
 131 {
 132         u32 *k = (u32 *) key;
 133
 134         return (jhash2(k, (sizeof(*key) / sizeof(u32)), flow_hash_rnd(cpu)) &
 135                 (flow_hash_size - 1));
 136 }
 137
 138 #if (BITS_PER_LONG == 64)
 139 typedef u64 flow_compare_t;
 140 #else
 141 typedef u32 flow_compare_t;
 142 #endif
 143
 144 /* I hear what you're saying, use memcmp.  But memcmp cannot make
 145  * important assumptions that we can here, such as alignment and
 146  * constant size.
 147  */
 148 static int flow_key_compare(struct flowi *key1, struct flowi *key2)
 149 {
 150         flow_compare_t *k1, *k1_lim, *k2;
 151         const int n_elem = sizeof(struct flowi) / sizeof(flow_compare_t);
 152
 153         BUILD_BUG_ON(sizeof(struct flowi) % sizeof(flow_compare_t));
 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 net *net, struct flowi *key, 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                     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, GFP_ATOMIC);
 211                 if (fle) {
 212                         fle->next = *head;
 213                         *head = fle;
 214                         fle->family = family;
 215                         fle->dir = dir;
 216                         memcpy(&fle->key, key, sizeof(*key));
 217                         fle->object = NULL;
 218                         flow_count(cpu)++;
 219                 }
 220         }
 221
 222 nocache:
 223         {
 224                 int err;
 225                 void *obj;
 226                 atomic_t *obj_ref;
 227
 228                 err = resolver(net, key, family, dir, &obj, &obj_ref);
 229
 230                 if (fle && !err) {
 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                 if (err)
 244                         obj = ERR_PTR(err);
 245                 return obj;
 246         }
 247 }
 248
 249 static void flow_cache_flush_tasklet(unsigned long data)
 250 {
 251         struct flow_flush_info *info = (void *)data;
 252         int i;
 253         int cpu;
 254
 255         cpu = smp_processor_id();
 256         for (i = 0; i < flow_hash_size; i++) {
 257                 struct flow_cache_entry *fle;
 258
 259                 fle = flow_table(cpu)[i];
 260                 for (; fle; fle = fle->next) {
 261                         unsigned genid = atomic_read(&flow_cache_genid);
 262
 263                         if (!fle->object || fle->genid == genid)
 264                                 continue;
 265
 266                         fle->object = NULL;
 267                         atomic_dec(fle->object_ref);
 268                 }
 269         }
 270
 271         if (atomic_dec_and_test(&info->cpuleft))
 272                 complete(&info->completion);
 273 }
 274
 275 static void flow_cache_flush_per_cpu(void *) __attribute__((__unused__));
 276 static void flow_cache_flush_per_cpu(void *data)
 277 {
 278         struct flow_flush_info *info = data;
 279         int cpu;
 280         struct tasklet_struct *tasklet;
 281
 282         cpu = smp_processor_id();
 283
 284         tasklet = flow_flush_tasklet(cpu);
 285         tasklet->data = (unsigned long)info;
 286         tasklet_schedule(tasklet);
 287 }
 288
 289 void flow_cache_flush(void)
 290 {
 291         struct flow_flush_info info;
 292         static DEFINE_MUTEX(flow_flush_sem);
 293
 294         /* Don't want cpus going down or up during this. */
 295         get_online_cpus();
 296         mutex_lock(&flow_flush_sem);
 297         atomic_set(&info.cpuleft, num_online_cpus());
 298         init_completion(&info.completion);
 299
 300         local_bh_disable();
 301         smp_call_function(flow_cache_flush_per_cpu, &info, 0);
 302         flow_cache_flush_tasklet((unsigned long)&info);
 303         local_bh_enable();
 304
 305         wait_for_completion(&info.completion);
 306         mutex_unlock(&flow_flush_sem);
 307         put_online_cpus();
 308 }
 309
 310 static void __init flow_cache_cpu_prepare(int cpu)
 311 {
 312         struct tasklet_struct *tasklet;
 313         unsigned long order;
 314
 315         for (order = 0;
 316              (PAGE_SIZE << order) <
 317                      (sizeof(struct flow_cache_entry *)*flow_hash_size);
 318              order++)
 319                 /* NOTHING */;
 320
 321         flow_table(cpu) = (struct flow_cache_entry **)
 322                 __get_free_pages(GFP_KERNEL|__GFP_ZERO, order);
 323         if (!flow_table(cpu))
 324                 panic("NET: failed to allocate flow cache order %lu\n", 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 static int flow_cache_cpu(struct notifier_block *nfb,
 334                           unsigned long action,
 335                           void *hcpu)
 336 {
 337         if (action == CPU_DEAD || action == CPU_DEAD_FROZEN)
 338                 __flow_cache_shrink((unsigned long)hcpu, 0);
 339         return NOTIFY_OK;
 340 }
 341
 342 static int __init flow_cache_init(void)
 343 {
 344         int i;
 345
 346         flow_cachep = kmem_cache_create("flow_cache",
 347                                         sizeof(struct flow_cache_entry),
 348                                         0, SLAB_PANIC,
 349                                         NULL);
 350         flow_hash_shift = 10;
 351         flow_lwm = 2 * flow_hash_size;
 352         flow_hwm = 4 * flow_hash_size;
 353
 354         setup_timer(&flow_hash_rnd_timer, flow_cache_new_hashrnd, 0);
 355         flow_hash_rnd_timer.expires = jiffies + FLOW_HASH_RND_PERIOD;
 356         add_timer(&flow_hash_rnd_timer);
 357
 358         for_each_possible_cpu(i)
 359                 flow_cache_cpu_prepare(i);
 360
 361         hotcpu_notifier(flow_cache_cpu, 0);
 362         return 0;
 363 }
 364
 365 module_init(flow_cache_init);
 366
 367 EXPORT_SYMBOL(flow_cache_genid);
 368 EXPORT_SYMBOL(flow_cache_lookup);