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/jhash.h>
  16 #include <linux/netlink.h>
  17 #include <linux/vmalloc.h>
  18 #include <linux/netfilter.h>
  19 #include <linux/netfilter/nf_tables.h>
  20 #include <net/netfilter/nf_tables.h>
  21
  22 #define NFT_HASH_MIN_SIZE       4
  23
  24 struct nft_hash {
  25         struct nft_hash_table __rcu     *tbl;
  26 };
  27
  28 struct nft_hash_table {
  29         unsigned int                    size;
  30         unsigned int                    elements;
  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         if (is_vmalloc_addr(tbl))
  80                 vfree(tbl);
  81         else
  82                 kfree(tbl);
  83 }
  84
  85 static struct nft_hash_table *nft_hash_tbl_alloc(unsigned int nbuckets)
  86 {
  87         struct nft_hash_table *tbl;
  88         size_t size;
  89
  90         size = sizeof(*tbl) + nbuckets * sizeof(tbl->buckets[0]);
  91         tbl = kzalloc(size, GFP_KERNEL | __GFP_REPEAT | __GFP_NOWARN);
  92         if (tbl == NULL)
  93                 tbl = vzalloc(size);
  94         if (tbl == NULL)
  95                 return NULL;
  96         tbl->size = nbuckets;
  97
  98         return tbl;
  99 }
 100
 101 static void nft_hash_chain_unzip(const struct nft_set *set,
 102                                  const struct nft_hash_table *ntbl,
 103                                  struct nft_hash_table *tbl, unsigned int n)
 104 {
 105         struct nft_hash_elem *he, *last, *next;
 106         unsigned int h;
 107
 108         he = nft_dereference(tbl->buckets[n]);
 109         if (he == NULL)
 110                 return;
 111         h = nft_hash_data(&he->key, ntbl->size, set->klen);
 112
 113         /* Find last element of first chain hashing to bucket h */
 114         last = he;
 115         nft_hash_for_each_entry(he, he->next) {
 116                 if (nft_hash_data(&he->key, ntbl->size, set->klen) != h)
 117                         break;
 118                 last = he;
 119         }
 120
 121         /* Unlink first chain from the old table */
 122         RCU_INIT_POINTER(tbl->buckets[n], last->next);
 123
 124         /* If end of chain reached, done */
 125         if (he == NULL)
 126                 return;
 127
 128         /* Find first element of second chain hashing to bucket h */
 129         next = NULL;
 130         nft_hash_for_each_entry(he, he->next) {
 131                 if (nft_hash_data(&he->key, ntbl->size, set->klen) != h)
 132                         continue;
 133                 next = he;
 134                 break;
 135         }
 136
 137         /* Link the two chains */
 138         RCU_INIT_POINTER(last->next, next);
 139 }
 140
 141 static int nft_hash_tbl_expand(const struct nft_set *set, struct nft_hash *priv)
 142 {
 143         struct nft_hash_table *tbl = nft_dereference(priv->tbl), *ntbl;
 144         struct nft_hash_elem *he;
 145         unsigned int i, h;
 146         bool complete;
 147
 148         ntbl = nft_hash_tbl_alloc(tbl->size * 2);
 149         if (ntbl == NULL)
 150                 return -ENOMEM;
 151
 152         /* Link new table's buckets to first element in the old table
 153          * hashing to the new bucket.
 154          */
 155         for (i = 0; i < ntbl->size; i++) {
 156                 h = i < tbl->size ? i : i - tbl->size;
 157                 nft_hash_for_each_entry(he, tbl->buckets[h]) {
 158                         if (nft_hash_data(&he->key, ntbl->size, set->klen) != i)
 159                                 continue;
 160                         RCU_INIT_POINTER(ntbl->buckets[i], he);
 161                         break;
 162                 }
 163         }
 164         ntbl->elements = tbl->elements;
 165
 166         /* Publish new table */
 167         rcu_assign_pointer(priv->tbl, ntbl);
 168
 169         /* Unzip interleaved hash chains */
 170         do {
 171                 /* Wait for readers to use new table/unzipped chains */
 172                 synchronize_rcu();
 173
 174                 complete = true;
 175                 for (i = 0; i < tbl->size; i++) {
 176                         nft_hash_chain_unzip(set, ntbl, tbl, i);
 177                         if (tbl->buckets[i] != NULL)
 178                                 complete = false;
 179                 }
 180         } while (!complete);
 181
 182         nft_hash_tbl_free(tbl);
 183         return 0;
 184 }
 185
 186 static int nft_hash_tbl_shrink(const struct nft_set *set, struct nft_hash *priv)
 187 {
 188         struct nft_hash_table *tbl = nft_dereference(priv->tbl), *ntbl;
 189         struct nft_hash_elem __rcu **pprev;
 190         unsigned int i;
 191
 192         ntbl = nft_hash_tbl_alloc(tbl->size / 2);
 193         if (ntbl == NULL)
 194                 return -ENOMEM;
 195
 196         for (i = 0; i < ntbl->size; i++) {
 197                 ntbl->buckets[i] = tbl->buckets[i];
 198
 199                 for (pprev = &ntbl->buckets[i]; *pprev != NULL;
 200                      pprev = &nft_dereference(*pprev)->next)
 201                         ;
 202                 RCU_INIT_POINTER(*pprev, tbl->buckets[i + ntbl->size]);
 203         }
 204         ntbl->elements = tbl->elements;
 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         tbl->elements++;
 241
 242         /* Expand table when exceeding 75% load */
 243         if (tbl->elements > tbl->size / 4 * 3)
 244                 nft_hash_tbl_expand(set, priv);
 245
 246         return 0;
 247 }
 248
 249 static void nft_hash_elem_destroy(const struct nft_set *set,
 250                                   struct nft_hash_elem *he)
 251 {
 252         nft_data_uninit(&he->key, NFT_DATA_VALUE);
 253         if (set->flags & NFT_SET_MAP)
 254                 nft_data_uninit(he->data, set->dtype);
 255         kfree(he);
 256 }
 257
 258 static void nft_hash_remove(const struct nft_set *set,
 259                             const struct nft_set_elem *elem)
 260 {
 261         struct nft_hash *priv = nft_set_priv(set);
 262         struct nft_hash_table *tbl = nft_dereference(priv->tbl);
 263         struct nft_hash_elem *he, __rcu **pprev;
 264
 265         pprev = elem->cookie;
 266         he = nft_dereference((*pprev));
 267
 268         RCU_INIT_POINTER(*pprev, he->next);
 269         synchronize_rcu();
 270         kfree(he);
 271         tbl->elements--;
 272
 273         /* Shrink table beneath 30% load */
 274         if (tbl->elements < tbl->size * 3 / 10 &&
 275             tbl->size > NFT_HASH_MIN_SIZE)
 276                 nft_hash_tbl_shrink(set, priv);
 277 }
 278
 279 static int nft_hash_get(const struct nft_set *set, struct nft_set_elem *elem)
 280 {
 281         const struct nft_hash *priv = nft_set_priv(set);
 282         const struct nft_hash_table *tbl = nft_dereference(priv->tbl);
 283         struct nft_hash_elem __rcu * const *pprev;
 284         struct nft_hash_elem *he;
 285         unsigned int h;
 286
 287         h = nft_hash_data(&elem->key, tbl->size, set->klen);
 288         pprev = &tbl->buckets[h];
 289         nft_hash_for_each_entry(he, tbl->buckets[h]) {
 290                 if (nft_data_cmp(&he->key, &elem->key, set->klen)) {
 291                         pprev = &he->next;
 292                         continue;
 293                 }
 294
 295                 elem->cookie = (void *)pprev;
 296                 elem->flags = 0;
 297                 if (set->flags & NFT_SET_MAP)
 298                         nft_data_copy(&elem->data, he->data);
 299                 return 0;
 300         }
 301         return -ENOENT;
 302 }
 303
 304 static void nft_hash_walk(const struct nft_ctx *ctx, const struct nft_set *set,
 305                           struct nft_set_iter *iter)
 306 {
 307         const struct nft_hash *priv = nft_set_priv(set);
 308         const struct nft_hash_table *tbl = nft_dereference(priv->tbl);
 309         const struct nft_hash_elem *he;
 310         struct nft_set_elem elem;
 311         unsigned int i;
 312
 313         for (i = 0; i < tbl->size; i++) {
 314                 nft_hash_for_each_entry(he, tbl->buckets[i]) {
 315                         if (iter->count < iter->skip)
 316                                 goto cont;
 317
 318                         memcpy(&elem.key, &he->key, sizeof(elem.key));
 319                         if (set->flags & NFT_SET_MAP)
 320                                 memcpy(&elem.data, he->data, sizeof(elem.data));
 321                         elem.flags = 0;
 322
 323                         iter->err = iter->fn(ctx, set, iter, &elem);
 324                         if (iter->err < 0)
 325                                 return;
 326 cont:
 327                         iter->count++;
 328                 }
 329         }
 330 }
 331
 332 static unsigned int nft_hash_privsize(const struct nlattr * const nla[])
 333 {
 334         return sizeof(struct nft_hash);
 335 }
 336
 337 static int nft_hash_init(const struct nft_set *set,
 338                          const struct nlattr * const tb[])
 339 {
 340         struct nft_hash *priv = nft_set_priv(set);
 341         struct nft_hash_table *tbl;
 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         tbl = nft_hash_tbl_alloc(NFT_HASH_MIN_SIZE);
 349         if (tbl == NULL)
 350                 return -ENOMEM;
 351         RCU_INIT_POINTER(priv->tbl, tbl);
 352         return 0;
 353 }
 354
 355 static void nft_hash_destroy(const struct nft_set *set)
 356 {
 357         const struct nft_hash *priv = nft_set_priv(set);
 358         const struct nft_hash_table *tbl = nft_dereference(priv->tbl);
 359         struct nft_hash_elem *he, *next;
 360         unsigned int i;
 361
 362         for (i = 0; i < tbl->size; i++) {
 363                 for (he = nft_dereference(tbl->buckets[i]); he != NULL;
 364                      he = next) {
 365                         next = nft_dereference(he->next);
 366                         nft_hash_elem_destroy(set, he);
 367                 }
 368         }
 369         kfree(tbl);
 370 }
 371
 372 static struct nft_set_ops nft_hash_ops __read_mostly = {
 373         .privsize       = nft_hash_privsize,
 374         .init           = nft_hash_init,
 375         .destroy        = nft_hash_destroy,
 376         .get            = nft_hash_get,
 377         .insert         = nft_hash_insert,
 378         .remove         = nft_hash_remove,
 379         .lookup         = nft_hash_lookup,
 380         .walk           = nft_hash_walk,
 381         .features       = NFT_SET_MAP,
 382         .owner          = THIS_MODULE,
 383 };
 384
 385 static int __init nft_hash_module_init(void)
 386 {
 387         return nft_register_set(&nft_hash_ops);
 388 }
 389
 390 static void __exit nft_hash_module_exit(void)
 391 {
 392         nft_unregister_set(&nft_hash_ops);
 393 }
 394
 395 module_init(nft_hash_module_init);
 396 module_exit(nft_hash_module_exit);
 397
 398 MODULE_LICENSE("GPL");
 399 MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
 400 MODULE_ALIAS_NFT_SET();