net/netfilter/nft_set_bitmap.c

   1 /*
   2  * Copyright (c) 2017 Pablo Neira Ayuso <pablo@netfilter.org>
   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
   9 #include <linux/kernel.h>
  10 #include <linux/init.h>
  11 #include <linux/module.h>
  12 #include <linux/list.h>
  13 #include <linux/netlink.h>
  14 #include <linux/netfilter.h>
  15 #include <linux/netfilter/nf_tables.h>
  16 #include <net/netfilter/nf_tables.h>
  17
  18 struct nft_bitmap_elem {
  19         struct list_head        head;
  20         struct nft_set_ext      ext;
  21 };
  22
  23 /* This bitmap uses two bits to represent one element. These two bits determine
  24  * the element state in the current and the future generation.
  25  *
  26  * An element can be in three states. The generation cursor is represented using
  27  * the ^ character, note that this cursor shifts on every succesful transaction.
  28  * If no transaction is going on, we observe all elements are in the following
  29  * state:
  30  *
  31  * 11 = this element is active in the current generation. In case of no updates,
  32  * ^    it stays active in the next generation.
  33  * 00 = this element is inactive in the current generation. In case of no
  34  * ^    updates, it stays inactive in the next generation.
  35  *
  36  * On transaction handling, we observe these two temporary states:
  37  *
  38  * 01 = this element is inactive in the current generation and it becomes active
  39  * ^    in the next one. This happens when the element is inserted but commit
  40  *      path has not yet been executed yet, so activation is still pending. On
  41  *      transaction abortion, the element is removed.
  42  * 10 = this element is active in the current generation and it becomes inactive
  43  * ^    in the next one. This happens when the element is deactivated but commit
  44  *      path has not yet been executed yet, so removal is still pending. On
  45  *      transation abortion, the next generation bit is reset to go back to
  46  *      restore its previous state.
  47  */
  48 struct nft_bitmap {
  49         struct  list_head       list;
  50         u16                     bitmap_size;
  51         u8                      bitmap[];
  52 };
  53
  54 static inline void nft_bitmap_location(const struct nft_set *set,
  55                                        const void *key,
  56                                        u32 *idx, u32 *off)
  57 {
  58         u32 k;
  59
  60         if (set->klen == 2)
  61                 k = *(u16 *)key;
  62         else
  63                 k = *(u8 *)key;
  64         k <<= 1;
  65
  66         *idx = k / BITS_PER_BYTE;
  67         *off = k % BITS_PER_BYTE;
  68 }
  69
  70 /* Fetch the two bits that represent the element and check if it is active based
  71  * on the generation mask.
  72  */
  73 static inline bool
  74 nft_bitmap_active(const u8 *bitmap, u32 idx, u32 off, u8 genmask)
  75 {
  76         return (bitmap[idx] & (0x3 << off)) & (genmask << off);
  77 }
  78
  79 static bool nft_bitmap_lookup(const struct net *net, const struct nft_set *set,
  80                               const u32 *key, const struct nft_set_ext **ext)
  81 {
  82         const struct nft_bitmap *priv = nft_set_priv(set);
  83         u8 genmask = nft_genmask_cur(net);
  84         u32 idx, off;
  85
  86         nft_bitmap_location(set, key, &idx, &off);
  87
  88         return nft_bitmap_active(priv->bitmap, idx, off, genmask);
  89 }
  90
  91 static struct nft_bitmap_elem *
  92 nft_bitmap_elem_find(const struct nft_set *set, struct nft_bitmap_elem *this,
  93                      u8 genmask)
  94 {
  95         const struct nft_bitmap *priv = nft_set_priv(set);
  96         struct nft_bitmap_elem *be;
  97
  98         list_for_each_entry_rcu(be, &priv->list, head) {
  99                 if (memcmp(nft_set_ext_key(&be->ext),
 100                            nft_set_ext_key(&this->ext), set->klen) ||
 101                     !nft_set_elem_active(&be->ext, genmask))
 102                         continue;
 103
 104                 return be;
 105         }
 106         return NULL;
 107 }
 108
 109 static void *nft_bitmap_get(const struct net *net, const struct nft_set *set,
 110                             const struct nft_set_elem *elem, unsigned int flags)
 111 {
 112         const struct nft_bitmap *priv = nft_set_priv(set);
 113         u8 genmask = nft_genmask_cur(net);
 114         struct nft_bitmap_elem *be;
 115
 116         list_for_each_entry_rcu(be, &priv->list, head) {
 117                 if (memcmp(nft_set_ext_key(&be->ext), elem->key.val.data, set->klen) ||
 118                     !nft_set_elem_active(&be->ext, genmask))
 119                         continue;
 120
 121                 return be;
 122         }
 123         return ERR_PTR(-ENOENT);
 124 }
 125
 126 static int nft_bitmap_insert(const struct net *net, const struct nft_set *set,
 127                              const struct nft_set_elem *elem,
 128                              struct nft_set_ext **ext)
 129 {
 130         struct nft_bitmap *priv = nft_set_priv(set);
 131         struct nft_bitmap_elem *new = elem->priv, *be;
 132         u8 genmask = nft_genmask_next(net);
 133         u32 idx, off;
 134
 135         be = nft_bitmap_elem_find(set, new, genmask);
 136         if (be) {
 137                 *ext = &be->ext;
 138                 return -EEXIST;
 139         }
 140
 141         nft_bitmap_location(set, nft_set_ext_key(&new->ext), &idx, &off);
 142         /* Enter 01 state. */
 143         priv->bitmap[idx] |= (genmask << off);
 144         list_add_tail_rcu(&new->head, &priv->list);
 145
 146         return 0;
 147 }
 148
 149 static void nft_bitmap_remove(const struct net *net,
 150                               const struct nft_set *set,
 151                               const struct nft_set_elem *elem)
 152 {
 153         struct nft_bitmap *priv = nft_set_priv(set);
 154         struct nft_bitmap_elem *be = elem->priv;
 155         u8 genmask = nft_genmask_next(net);
 156         u32 idx, off;
 157
 158         nft_bitmap_location(set, nft_set_ext_key(&be->ext), &idx, &off);
 159         /* Enter 00 state. */
 160         priv->bitmap[idx] &= ~(genmask << off);
 161         list_del_rcu(&be->head);
 162 }
 163
 164 static void nft_bitmap_activate(const struct net *net,
 165                                 const struct nft_set *set,
 166                                 const struct nft_set_elem *elem)
 167 {
 168         struct nft_bitmap *priv = nft_set_priv(set);
 169         struct nft_bitmap_elem *be = elem->priv;
 170         u8 genmask = nft_genmask_next(net);
 171         u32 idx, off;
 172
 173         nft_bitmap_location(set, nft_set_ext_key(&be->ext), &idx, &off);
 174         /* Enter 11 state. */
 175         priv->bitmap[idx] |= (genmask << off);
 176         nft_set_elem_change_active(net, set, &be->ext);
 177 }
 178
 179 static bool nft_bitmap_flush(const struct net *net,
 180                              const struct nft_set *set, void *_be)
 181 {
 182         struct nft_bitmap *priv = nft_set_priv(set);
 183         u8 genmask = nft_genmask_next(net);
 184         struct nft_bitmap_elem *be = _be;
 185         u32 idx, off;
 186
 187         nft_bitmap_location(set, nft_set_ext_key(&be->ext), &idx, &off);
 188         /* Enter 10 state, similar to deactivation. */
 189         priv->bitmap[idx] &= ~(genmask << off);
 190         nft_set_elem_change_active(net, set, &be->ext);
 191
 192         return true;
 193 }
 194
 195 static void *nft_bitmap_deactivate(const struct net *net,
 196                                    const struct nft_set *set,
 197                                    const struct nft_set_elem *elem)
 198 {
 199         struct nft_bitmap *priv = nft_set_priv(set);
 200         struct nft_bitmap_elem *this = elem->priv, *be;
 201         u8 genmask = nft_genmask_next(net);
 202         u32 idx, off;
 203
 204         nft_bitmap_location(set, elem->key.val.data, &idx, &off);
 205
 206         be = nft_bitmap_elem_find(set, this, genmask);
 207         if (!be)
 208                 return NULL;
 209
 210         /* Enter 10 state. */
 211         priv->bitmap[idx] &= ~(genmask << off);
 212         nft_set_elem_change_active(net, set, &be->ext);
 213
 214         return be;
 215 }
 216
 217 static void nft_bitmap_walk(const struct nft_ctx *ctx,
 218                             struct nft_set *set,
 219                             struct nft_set_iter *iter)
 220 {
 221         const struct nft_bitmap *priv = nft_set_priv(set);
 222         struct nft_bitmap_elem *be;
 223         struct nft_set_elem elem;
 224
 225         list_for_each_entry_rcu(be, &priv->list, head) {
 226                 if (iter->count < iter->skip)
 227                         goto cont;
 228                 if (!nft_set_elem_active(&be->ext, iter->genmask))
 229                         goto cont;
 230
 231                 elem.priv = be;
 232
 233                 iter->err = iter->fn(ctx, set, iter, &elem);
 234
 235                 if (iter->err < 0)
 236                         return;
 237 cont:
 238                 iter->count++;
 239         }
 240 }
 241
 242 /* The bitmap size is pow(2, key length in bits) / bits per byte. This is
 243  * multiplied by two since each element takes two bits. For 8 bit keys, the
 244  * bitmap consumes 66 bytes. For 16 bit keys, 16388 bytes.
 245  */
 246 static inline u32 nft_bitmap_size(u32 klen)
 247 {
 248         return ((2 << ((klen * BITS_PER_BYTE) - 1)) / BITS_PER_BYTE) << 1;
 249 }
 250
 251 static inline u32 nft_bitmap_total_size(u32 klen)
 252 {
 253         return sizeof(struct nft_bitmap) + nft_bitmap_size(klen);
 254 }
 255
 256 static unsigned int nft_bitmap_privsize(const struct nlattr * const nla[],
 257                                         const struct nft_set_desc *desc)
 258 {
 259         u32 klen = ntohl(nla_get_be32(nla[NFTA_SET_KEY_LEN]));
 260
 261         return nft_bitmap_total_size(klen);
 262 }
 263
 264 static int nft_bitmap_init(const struct nft_set *set,
 265                          const struct nft_set_desc *desc,
 266                          const struct nlattr * const nla[])
 267 {
 268         struct nft_bitmap *priv = nft_set_priv(set);
 269
 270         INIT_LIST_HEAD(&priv->list);
 271         priv->bitmap_size = nft_bitmap_size(set->klen);
 272
 273         return 0;
 274 }
 275
 276 static void nft_bitmap_destroy(const struct nft_set *set)
 277 {
 278         struct nft_bitmap *priv = nft_set_priv(set);
 279         struct nft_bitmap_elem *be, *n;
 280
 281         list_for_each_entry_safe(be, n, &priv->list, head)
 282                 nft_set_elem_destroy(set, be, true);
 283 }
 284
 285 static bool nft_bitmap_estimate(const struct nft_set_desc *desc, u32 features,
 286                                 struct nft_set_estimate *est)
 287 {
 288         /* Make sure bitmaps we don't get bitmaps larger than 16 Kbytes. */
 289         if (desc->klen > 2)
 290                 return false;
 291
 292         est->size   = nft_bitmap_total_size(desc->klen);
 293         est->lookup = NFT_SET_CLASS_O_1;
 294         est->space  = NFT_SET_CLASS_O_1;
 295
 296         return true;
 297 }
 298
 299 static struct nft_set_type nft_bitmap_type;
 300 static struct nft_set_ops nft_bitmap_ops __read_mostly = {
 301         .type           = &nft_bitmap_type,
 302         .privsize       = nft_bitmap_privsize,
 303         .elemsize       = offsetof(struct nft_bitmap_elem, ext),
 304         .estimate       = nft_bitmap_estimate,
 305         .init           = nft_bitmap_init,
 306         .destroy        = nft_bitmap_destroy,
 307         .insert         = nft_bitmap_insert,
 308         .remove         = nft_bitmap_remove,
 309         .deactivate     = nft_bitmap_deactivate,
 310         .flush          = nft_bitmap_flush,
 311         .activate       = nft_bitmap_activate,
 312         .lookup         = nft_bitmap_lookup,
 313         .walk           = nft_bitmap_walk,
 314         .get            = nft_bitmap_get,
 315 };
 316
 317 static struct nft_set_type nft_bitmap_type __read_mostly = {
 318         .ops            = &nft_bitmap_ops,
 319         .owner          = THIS_MODULE,
 320 };
 321
 322 static int __init nft_bitmap_module_init(void)
 323 {
 324         return nft_register_set(&nft_bitmap_type);
 325 }
 326
 327 static void __exit nft_bitmap_module_exit(void)
 328 {
 329         nft_unregister_set(&nft_bitmap_type);
 330 }
 331
 332 module_init(nft_bitmap_module_init);
 333 module_exit(nft_bitmap_module_exit);
 334
 335 MODULE_LICENSE("GPL");
 336 MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>");
 337 MODULE_ALIAS_NFT_SET();