net/netfilter/nft_hash.c

   1 /*
   2  * Copyright (c) 2008-2014 Patrick McHardy <kaber@trash.net>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  *
   8  * Development of this code funded by Astaro AG (http://www.astaro.com/)
   9  */
  10
  11 #include <linux/kernel.h>
  12 #include <linux/init.h>
  13 #include <linux/module.h>
  14 #include <linux/list.h>
  15 #include <linux/log2.h>
  16 #include <linux/jhash.h>
  17 #include <linux/netlink.h>
  18 #include <linux/vmalloc.h>
  19 #include <linux/netfilter.h>
  20 #include <linux/netfilter/nf_tables.h>
  21 #include <net/netfilter/nf_tables.h>
  22
  23 #define NFT_HASH_MIN_SIZE       4UL
  24
  25 struct nft_hash {
  26         struct nft_hash_table __rcu     *tbl;
  27 };
  28
  29 struct nft_hash_table {
  30         unsigned int                    size;
  31         struct nft_hash_elem __rcu      *buckets[];
  32 };
  33
  34 struct nft_hash_elem {
  35         struct nft_hash_elem __rcu      *next;
  36         struct nft_data                 key;
  37         struct nft_data                 data[];
  38 };
  39
  40 #define nft_hash_for_each_entry(i, head) \
  41         for (i = nft_dereference(head); i != NULL; i = nft_dereference(i->next))
  42 #define nft_hash_for_each_entry_rcu(i, head) \
  43         for (i = rcu_dereference(head); i != NULL; i = rcu_dereference(i->next))
  44
  45 static u32 nft_hash_rnd __read_mostly;
  46 static bool nft_hash_rnd_initted __read_mostly;
  47
  48 static unsigned int nft_hash_data(const struct nft_data *data,
  49                                   unsigned int hsize, unsigned int len)
  50 {
  51         unsigned int h;
  52
  53         h = jhash(data->data, len, nft_hash_rnd);
  54         return h & (hsize - 1);
  55 }
  56
  57 static bool nft_hash_lookup(const struct nft_set *set,
  58                             const struct nft_data *key,
  59                             struct nft_data *data)
  60 {
  61         const struct nft_hash *priv = nft_set_priv(set);
  62         const struct nft_hash_table *tbl = rcu_dereference(priv->tbl);
  63         const struct nft_hash_elem *he;
  64         unsigned int h;
  65
  66         h = nft_hash_data(key, tbl->size, set->klen);
  67         nft_hash_for_each_entry_rcu(he, tbl->buckets[h]) {
  68                 if (nft_data_cmp(&he->key, key, set->klen))
  69                         continue;
  70                 if (set->flags & NFT_SET_MAP)
  71                         nft_data_copy(data, he->data);
  72                 return true;
  73         }
  74         return false;
  75 }
  76
  77 static void nft_hash_tbl_free(const struct nft_hash_table *tbl)
  78 {
  79         kvfree(tbl);
  80 }
  81
  82 static unsigned int nft_hash_tbl_size(unsigned int nelem)
  83 {
  84         return max(roundup_pow_of_two(nelem * 4 / 3), NFT_HASH_MIN_SIZE);
  85 }
  86
  87 static struct nft_hash_table *nft_hash_tbl_alloc(unsigned int nbuckets)
  88 {
  89         struct nft_hash_table *tbl;
  90         size_t size;
  91
  92         size = sizeof(*tbl) + nbuckets * sizeof(tbl->buckets[0]);
  93         tbl = kzalloc(size, GFP_KERNEL | __GFP_REPEAT | __GFP_NOWARN);
  94         if (tbl == NULL)
  95                 tbl = vzalloc(size);
  96         if (tbl == NULL)
  97                 return NULL;
  98         tbl->size = nbuckets;
  99
 100         return tbl;
 101 }
 102
 103 static void nft_hash_chain_unzip(const struct nft_set *set,
 104                                  const struct nft_hash_table *ntbl,
 105                                  struct nft_hash_table *tbl, unsigned int n)
 106 {
 107         struct nft_hash_elem *he, *last, *next;
 108         unsigned int h;
 109
 110         he = nft_dereference(tbl->buckets[n]);
 111         if (he == NULL)
 112                 return;
 113         h = nft_hash_data(&he->key, ntbl->size, set->klen);
 114
 115         /* Find last element of first chain hashing to bucket h */
 116         last = he;
 117         nft_hash_for_each_entry(he, he->next) {
 118                 if (nft_hash_data(&he->key, ntbl->size, set->klen) != h)
 119                         break;
 120                 last = he;
 121         }
 122
 123         /* Unlink first chain from the old table */
 124         RCU_INIT_POINTER(tbl->buckets[n], last->next);
 125
 126         /* If end of chain reached, done */
 127         if (he == NULL)
 128                 return;
 129
 130         /* Find first element of second chain hashing to bucket h */
 131         next = NULL;
 132         nft_hash_for_each_entry(he, he->next) {
 133                 if (nft_hash_data(&he->key, ntbl->size, set->klen) != h)
 134                         continue;
 135                 next = he;
 136                 break;
 137         }
 138
 139         /* Link the two chains */
 140         RCU_INIT_POINTER(last->next, next);
 141 }
 142
 143 static int nft_hash_tbl_expand(const struct nft_set *set, struct nft_hash *priv)
 144 {
 145         struct nft_hash_table *tbl = nft_dereference(priv->tbl), *ntbl;
 146         struct nft_hash_elem *he;
 147         unsigned int i, h;
 148         bool complete;
 149
 150         ntbl = nft_hash_tbl_alloc(tbl->size * 2);
 151         if (ntbl == NULL)
 152                 return -ENOMEM;
 153
 154         /* Link new table's buckets to first element in the old table
 155          * hashing to the new bucket.
 156          */
 157         for (i = 0; i < ntbl->size; i++) {
 158                 h = i < tbl->size ? i : i - tbl->size;
 159                 nft_hash_for_each_entry(he, tbl->buckets[h]) {
 160                         if (nft_hash_data(&he->key, ntbl->size, set->klen) != i)
 161                                 continue;
 162                         RCU_INIT_POINTER(ntbl->buckets[i], he);
 163                         break;
 164                 }
 165         }
 166
 167         /* Publish new table */
 168         rcu_assign_pointer(priv->tbl, ntbl);
 169
 170         /* Unzip interleaved hash chains */
 171         do {
 172                 /* Wait for readers to use new table/unzipped chains */
 173                 synchronize_rcu();
 174
 175                 complete = true;
 176                 for (i = 0; i < tbl->size; i++) {
 177                         nft_hash_chain_unzip(set, ntbl, tbl, i);
 178                         if (tbl->buckets[i] != NULL)
 179                                 complete = false;
 180                 }
 181         } while (!complete);
 182
 183         nft_hash_tbl_free(tbl);
 184         return 0;
 185 }
 186
 187 static int nft_hash_tbl_shrink(const struct nft_set *set, struct nft_hash *priv)
 188 {
 189         struct nft_hash_table *tbl = nft_dereference(priv->tbl), *ntbl;
 190         struct nft_hash_elem __rcu **pprev;
 191         unsigned int i;
 192
 193         ntbl = nft_hash_tbl_alloc(tbl->size / 2);
 194         if (ntbl == NULL)
 195                 return -ENOMEM;
 196
 197         for (i = 0; i < ntbl->size; i++) {
 198                 ntbl->buckets[i] = tbl->buckets[i];
 199
 200                 for (pprev = &ntbl->buckets[i]; *pprev != NULL;
 201                      pprev = &nft_dereference(*pprev)->next)
 202                         ;
 203                 RCU_INIT_POINTER(*pprev, tbl->buckets[i + ntbl->size]);
 204         }
 205
 206         /* Publish new table */
 207         rcu_assign_pointer(priv->tbl, ntbl);
 208         synchronize_rcu();
 209
 210         nft_hash_tbl_free(tbl);
 211         return 0;
 212 }
 213
 214 static int nft_hash_insert(const struct nft_set *set,
 215                            const struct nft_set_elem *elem)
 216 {
 217         struct nft_hash *priv = nft_set_priv(set);
 218         struct nft_hash_table *tbl = nft_dereference(priv->tbl);
 219         struct nft_hash_elem *he;
 220         unsigned int size, h;
 221
 222         if (elem->flags != 0)
 223                 return -EINVAL;
 224
 225         size = sizeof(*he);
 226         if (set->flags & NFT_SET_MAP)
 227                 size += sizeof(he->data[0]);
 228
 229         he = kzalloc(size, GFP_KERNEL);
 230         if (he == NULL)
 231                 return -ENOMEM;
 232
 233         nft_data_copy(&he->key, &elem->key);
 234         if (set->flags & NFT_SET_MAP)
 235                 nft_data_copy(he->data, &elem->data);
 236
 237         h = nft_hash_data(&he->key, tbl->size, set->klen);
 238         RCU_INIT_POINTER(he->next, tbl->buckets[h]);
 239         rcu_assign_pointer(tbl->buckets[h], he);
 240
 241         /* Expand table when exceeding 75% load */
 242         if (set->nelems + 1 > tbl->size / 4 * 3)
 243                 nft_hash_tbl_expand(set, priv);
 244
 245         return 0;
 246 }
 247
 248 static void nft_hash_elem_destroy(const struct nft_set *set,
 249                                   struct nft_hash_elem *he)
 250 {
 251         nft_data_uninit(&he->key, NFT_DATA_VALUE);
 252         if (set->flags & NFT_SET_MAP)
 253                 nft_data_uninit(he->data, set->dtype);
 254         kfree(he);
 255 }
 256
 257 static void nft_hash_remove(const struct nft_set *set,
 258                             const struct nft_set_elem *elem)
 259 {
 260         struct nft_hash *priv = nft_set_priv(set);
 261         struct nft_hash_table *tbl = nft_dereference(priv->tbl);
 262         struct nft_hash_elem *he, __rcu **pprev;
 263
 264         pprev = elem->cookie;
 265         he = nft_dereference((*pprev));
 266
 267         RCU_INIT_POINTER(*pprev, he->next);
 268         synchronize_rcu();
 269         kfree(he);
 270
 271         /* Shrink table beneath 30% load */
 272         if (set->nelems - 1 < tbl->size * 3 / 10 &&
 273             tbl->size > NFT_HASH_MIN_SIZE)
 274                 nft_hash_tbl_shrink(set, priv);
 275 }
 276
 277 static int nft_hash_get(const struct nft_set *set, struct nft_set_elem *elem)
 278 {
 279         const struct nft_hash *priv = nft_set_priv(set);
 280         const struct nft_hash_table *tbl = nft_dereference(priv->tbl);
 281         struct nft_hash_elem __rcu * const *pprev;
 282         struct nft_hash_elem *he;
 283         unsigned int h;
 284
 285         h = nft_hash_data(&elem->key, tbl->size, set->klen);
 286         pprev = &tbl->buckets[h];
 287         nft_hash_for_each_entry(he, tbl->buckets[h]) {
 288                 if (nft_data_cmp(&he->key, &elem->key, set->klen)) {
 289                         pprev = &he->next;
 290                         continue;
 291                 }
 292
 293                 elem->cookie = (void *)pprev;
 294                 elem->flags = 0;
 295                 if (set->flags & NFT_SET_MAP)
 296                         nft_data_copy(&elem->data, he->data);
 297                 return 0;
 298         }
 299         return -ENOENT;
 300 }
 301
 302 static void nft_hash_walk(const struct nft_ctx *ctx, const struct nft_set *set,
 303                           struct nft_set_iter *iter)
 304 {
 305         const struct nft_hash *priv = nft_set_priv(set);
 306         const struct nft_hash_table *tbl = nft_dereference(priv->tbl);
 307         const struct nft_hash_elem *he;
 308         struct nft_set_elem elem;
 309         unsigned int i;
 310
 311         for (i = 0; i < tbl->size; i++) {
 312                 nft_hash_for_each_entry(he, tbl->buckets[i]) {
 313                         if (iter->count < iter->skip)
 314                                 goto cont;
 315
 316                         memcpy(&elem.key, &he->key, sizeof(elem.key));
 317                         if (set->flags & NFT_SET_MAP)
 318                                 memcpy(&elem.data, he->data, sizeof(elem.data));
 319                         elem.flags = 0;
 320
 321                         iter->err = iter->fn(ctx, set, iter, &elem);
 322                         if (iter->err < 0)
 323                                 return;
 324 cont:
 325                         iter->count++;
 326                 }
 327         }
 328 }
 329
 330 static unsigned int nft_hash_privsize(const struct nlattr * const nla[])
 331 {
 332         return sizeof(struct nft_hash);
 333 }
 334
 335 static int nft_hash_init(const struct nft_set *set,
 336                          const struct nft_set_desc *desc,
 337                          const struct nlattr * const tb[])
 338 {
 339         struct nft_hash *priv = nft_set_priv(set);
 340         struct nft_hash_table *tbl;
 341         unsigned int size;
 342
 343         if (unlikely(!nft_hash_rnd_initted)) {
 344                 get_random_bytes(&nft_hash_rnd, 4);
 345                 nft_hash_rnd_initted = true;
 346         }
 347
 348         size = NFT_HASH_MIN_SIZE;
 349         if (desc->size)
 350                 size = nft_hash_tbl_size(desc->size);
 351
 352         tbl = nft_hash_tbl_alloc(size);
 353         if (tbl == NULL)
 354                 return -ENOMEM;
 355         RCU_INIT_POINTER(priv->tbl, tbl);
 356         return 0;
 357 }
 358
 359 static void nft_hash_destroy(const struct nft_set *set)
 360 {
 361         const struct nft_hash *priv = nft_set_priv(set);
 362         const struct nft_hash_table *tbl = nft_dereference(priv->tbl);
 363         struct nft_hash_elem *he, *next;
 364         unsigned int i;
 365
 366         for (i = 0; i < tbl->size; i++) {
 367                 for (he = nft_dereference(tbl->buckets[i]); he != NULL;
 368                      he = next) {
 369                         next = nft_dereference(he->next);
 370                         nft_hash_elem_destroy(set, he);
 371                 }
 372         }
 373         kfree(tbl);
 374 }
 375
 376 static bool nft_hash_estimate(const struct nft_set_desc *desc, u32 features,
 377                               struct nft_set_estimate *est)
 378 {
 379         unsigned int esize;
 380
 381         esize = sizeof(struct nft_hash_elem);
 382         if (features & NFT_SET_MAP)
 383                 esize += FIELD_SIZEOF(struct nft_hash_elem, data[0]);
 384
 385         if (desc->size) {
 386                 est->size = sizeof(struct nft_hash) +
 387                             nft_hash_tbl_size(desc->size) *
 388                             sizeof(struct nft_hash_elem *) +
 389                             desc->size * esize;
 390         } else {
 391                 /* Resizing happens when the load drops below 30% or goes
 392                  * above 75%. The average of 52.5% load (approximated by 50%)
 393                  * is used for the size estimation of the hash buckets,
 394                  * meaning we calculate two buckets per element.
 395                  */
 396                 est->size = esize + 2 * sizeof(struct nft_hash_elem *);
 397         }
 398
 399         est->class = NFT_SET_CLASS_O_1;
 400
 401         return true;
 402 }
 403
 404 static struct nft_set_ops nft_hash_ops __read_mostly = {
 405         .privsize       = nft_hash_privsize,
 406         .estimate       = nft_hash_estimate,
 407         .init           = nft_hash_init,
 408         .destroy        = nft_hash_destroy,
 409         .get            = nft_hash_get,
 410         .insert         = nft_hash_insert,
 411         .remove         = nft_hash_remove,
 412         .lookup         = nft_hash_lookup,
 413         .walk           = nft_hash_walk,
 414         .features       = NFT_SET_MAP,
 415         .owner          = THIS_MODULE,
 416 };
 417
 418 static int __init nft_hash_module_init(void)
 419 {
 420         return nft_register_set(&nft_hash_ops);
 421 }
 422
 423 static void __exit nft_hash_module_exit(void)
 424 {
 425         nft_unregister_set(&nft_hash_ops);
 426 }
 427
 428 module_init(nft_hash_module_init);
 429 module_exit(nft_hash_module_exit);
 430
 431 MODULE_LICENSE("GPL");
 432 MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
 433 MODULE_ALIAS_NFT_SET();