net/netfilter/nft_set_bitmap.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (c) 2017 Pablo Neira Ayuso <pablo@netfilter.org>
   4  */
   5
   6 #include <linux/kernel.h>
   7 #include <linux/init.h>
   8 #include <linux/module.h>
   9 #include <linux/list.h>
  10 #include <linux/netlink.h>
  11 #include <linux/netfilter.h>
  12 #include <linux/netfilter/nf_tables.h>
  13 #include <net/netfilter/nf_tables_core.h>
  14
  15 struct nft_bitmap_elem {
  16         struct nft_elem_priv    priv;
  17         struct list_head        head;
  18         struct nft_set_ext      ext;
  19 };
  20
  21 /* This bitmap uses two bits to represent one element. These two bits determine
  22  * the element state in the current and the future generation.
  23  *
  24  * An element can be in three states. The generation cursor is represented using
  25  * the ^ character, note that this cursor shifts on every successful transaction.
  26  * If no transaction is going on, we observe all elements are in the following
  27  * state:
  28  *
  29  * 11 = this element is active in the current generation. In case of no updates,
  30  * ^    it stays active in the next generation.
  31  * 00 = this element is inactive in the current generation. In case of no
  32  * ^    updates, it stays inactive in the next generation.
  33  *
  34  * On transaction handling, we observe these two temporary states:
  35  *
  36  * 01 = this element is inactive in the current generation and it becomes active
  37  * ^    in the next one. This happens when the element is inserted but commit
  38  *      path has not yet been executed yet, so activation is still pending. On
  39  *      transaction abortion, the element is removed.
  40  * 10 = this element is active in the current generation and it becomes inactive
  41  * ^    in the next one. This happens when the element is deactivated but commit
  42  *      path has not yet been executed yet, so removal is still pending. On
  43  *      transaction abortion, the next generation bit is reset to go back to
  44  *      restore its previous state.
  45  */
  46 struct nft_bitmap {
  47         struct  list_head       list;
  48         u16                     bitmap_size;
  49         u8                      bitmap[];
  50 };
  51
  52 static inline void nft_bitmap_location(const struct nft_set *set,
  53                                        const void *key,
  54                                        u32 *idx, u32 *off)
  55 {
  56         u32 k;
  57
  58         if (set->klen == 2)
  59                 k = *(u16 *)key;
  60         else
  61                 k = *(u8 *)key;
  62         k <<= 1;
  63
  64         *idx = k / BITS_PER_BYTE;
  65         *off = k % BITS_PER_BYTE;
  66 }
  67
  68 /* Fetch the two bits that represent the element and check if it is active based
  69  * on the generation mask.
  70  */
  71 static inline bool
  72 nft_bitmap_active(const u8 *bitmap, u32 idx, u32 off, u8 genmask)
  73 {
  74         return (bitmap[idx] & (0x3 << off)) & (genmask << off);
  75 }
  76
  77 INDIRECT_CALLABLE_SCOPE
  78 bool nft_bitmap_lookup(const struct net *net, const struct nft_set *set,
  79                        const u32 *key, const struct nft_set_ext **ext)
  80 {
  81         const struct nft_bitmap *priv = nft_set_priv(set);
  82         u8 genmask = nft_genmask_cur(net);
  83         u32 idx, off;
  84
  85         nft_bitmap_location(set, key, &idx, &off);
  86
  87         return nft_bitmap_active(priv->bitmap, idx, off, genmask);
  88 }
  89
  90 static struct nft_bitmap_elem *
  91 nft_bitmap_elem_find(const struct net *net,
  92                      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                                 lockdep_is_held(&nft_pernet(net)->commit_mutex)) {
 100                 if (memcmp(nft_set_ext_key(&be->ext),
 101                            nft_set_ext_key(&this->ext), set->klen) ||
 102                     !nft_set_elem_active(&be->ext, genmask))
 103                         continue;
 104
 105                 return be;
 106         }
 107         return NULL;
 108 }
 109
 110 static struct nft_elem_priv *
 111 nft_bitmap_get(const struct net *net, const struct nft_set *set,
 112                const struct nft_set_elem *elem, unsigned int flags)
 113 {
 114         const struct nft_bitmap *priv = nft_set_priv(set);
 115         u8 genmask = nft_genmask_cur(net);
 116         struct nft_bitmap_elem *be;
 117
 118         list_for_each_entry_rcu(be, &priv->list, head) {
 119                 if (memcmp(nft_set_ext_key(&be->ext), elem->key.val.data, set->klen) ||
 120                     !nft_set_elem_active(&be->ext, genmask))
 121                         continue;
 122
 123                 return &be->priv;
 124         }
 125         return ERR_PTR(-ENOENT);
 126 }
 127
 128 static int nft_bitmap_insert(const struct net *net, const struct nft_set *set,
 129                              const struct nft_set_elem *elem,
 130                              struct nft_elem_priv **elem_priv)
 131 {
 132         struct nft_bitmap_elem *new = nft_elem_priv_cast(elem->priv), *be;
 133         struct nft_bitmap *priv = nft_set_priv(set);
 134         u8 genmask = nft_genmask_next(net);
 135         u32 idx, off;
 136
 137         be = nft_bitmap_elem_find(net, set, new, genmask);
 138         if (be) {
 139                 *elem_priv = &be->priv;
 140                 return -EEXIST;
 141         }
 142
 143         nft_bitmap_location(set, nft_set_ext_key(&new->ext), &idx, &off);
 144         /* Enter 01 state. */
 145         priv->bitmap[idx] |= (genmask << off);
 146         list_add_tail_rcu(&new->head, &priv->list);
 147
 148         return 0;
 149 }
 150
 151 static void nft_bitmap_remove(const struct net *net, const struct nft_set *set,
 152                               struct nft_elem_priv *elem_priv)
 153 {
 154         struct nft_bitmap_elem *be = nft_elem_priv_cast(elem_priv);
 155         struct nft_bitmap *priv = nft_set_priv(set);
 156         u8 genmask = nft_genmask_next(net);
 157         u32 idx, off;
 158
 159         nft_bitmap_location(set, nft_set_ext_key(&be->ext), &idx, &off);
 160         /* Enter 00 state. */
 161         priv->bitmap[idx] &= ~(genmask << off);
 162         list_del_rcu(&be->head);
 163 }
 164
 165 static void nft_bitmap_activate(const struct net *net,
 166                                 const struct nft_set *set,
 167                                 struct nft_elem_priv *elem_priv)
 168 {
 169         struct nft_bitmap_elem *be = nft_elem_priv_cast(elem_priv);
 170         struct nft_bitmap *priv = nft_set_priv(set);
 171         u8 genmask = nft_genmask_next(net);
 172         u32 idx, off;
 173
 174         nft_bitmap_location(set, nft_set_ext_key(&be->ext), &idx, &off);
 175         /* Enter 11 state. */
 176         priv->bitmap[idx] |= (genmask << off);
 177         nft_clear(net, &be->ext);
 178 }
 179
 180 static void nft_bitmap_flush(const struct net *net,
 181                              const struct nft_set *set,
 182                              struct nft_elem_priv *elem_priv)
 183 {
 184         struct nft_bitmap_elem *be = nft_elem_priv_cast(elem_priv);
 185         struct nft_bitmap *priv = nft_set_priv(set);
 186         u8 genmask = nft_genmask_next(net);
 187         u32 idx, off;
 188
 189         nft_bitmap_location(set, nft_set_ext_key(&be->ext), &idx, &off);
 190         /* Enter 10 state, similar to deactivation. */
 191         priv->bitmap[idx] &= ~(genmask << off);
 192         nft_set_elem_change_active(net, set, &be->ext);
 193 }
 194
 195 static struct nft_elem_priv *
 196 nft_bitmap_deactivate(const struct net *net, const struct nft_set *set,
 197                       const struct nft_set_elem *elem)
 198 {
 199         struct nft_bitmap_elem *this = nft_elem_priv_cast(elem->priv), *be;
 200         struct nft_bitmap *priv = nft_set_priv(set);
 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(net, 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->priv;
 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
 224         list_for_each_entry_rcu(be, &priv->list, head) {
 225                 if (iter->count < iter->skip)
 226                         goto cont;
 227
 228                 iter->err = iter->fn(ctx, set, iter, &be->priv);
 229
 230                 if (iter->err < 0)
 231                         return;
 232 cont:
 233                 iter->count++;
 234         }
 235 }
 236
 237 /* The bitmap size is pow(2, key length in bits) / bits per byte. This is
 238  * multiplied by two since each element takes two bits. For 8 bit keys, the
 239  * bitmap consumes 66 bytes. For 16 bit keys, 16388 bytes.
 240  */
 241 static inline u32 nft_bitmap_size(u32 klen)
 242 {
 243         return ((2 << ((klen * BITS_PER_BYTE) - 1)) / BITS_PER_BYTE) << 1;
 244 }
 245
 246 static inline u64 nft_bitmap_total_size(u32 klen)
 247 {
 248         return sizeof(struct nft_bitmap) + nft_bitmap_size(klen);
 249 }
 250
 251 static u64 nft_bitmap_privsize(const struct nlattr * const nla[],
 252                                const struct nft_set_desc *desc)
 253 {
 254         u32 klen = ntohl(nla_get_be32(nla[NFTA_SET_KEY_LEN]));
 255
 256         return nft_bitmap_total_size(klen);
 257 }
 258
 259 static int nft_bitmap_init(const struct nft_set *set,
 260                            const struct nft_set_desc *desc,
 261                            const struct nlattr * const nla[])
 262 {
 263         struct nft_bitmap *priv = nft_set_priv(set);
 264
 265         BUILD_BUG_ON(offsetof(struct nft_bitmap_elem, priv) != 0);
 266
 267         INIT_LIST_HEAD(&priv->list);
 268         priv->bitmap_size = nft_bitmap_size(set->klen);
 269
 270         return 0;
 271 }
 272
 273 static void nft_bitmap_destroy(const struct nft_ctx *ctx,
 274                                const struct nft_set *set)
 275 {
 276         struct nft_bitmap *priv = nft_set_priv(set);
 277         struct nft_bitmap_elem *be, *n;
 278
 279         list_for_each_entry_safe(be, n, &priv->list, head)
 280                 nf_tables_set_elem_destroy(ctx, set, &be->priv);
 281 }
 282
 283 static bool nft_bitmap_estimate(const struct nft_set_desc *desc, u32 features,
 284                                 struct nft_set_estimate *est)
 285 {
 286         /* Make sure bitmaps we don't get bitmaps larger than 16 Kbytes. */
 287         if (desc->klen > 2)
 288                 return false;
 289         else if (desc->expr)
 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 const struct nft_set_type nft_set_bitmap_type = {
 300         .ops            = {
 301                 .privsize       = nft_bitmap_privsize,
 302                 .elemsize       = offsetof(struct nft_bitmap_elem, ext),
 303                 .estimate       = nft_bitmap_estimate,
 304                 .init           = nft_bitmap_init,
 305                 .destroy        = nft_bitmap_destroy,
 306                 .insert         = nft_bitmap_insert,
 307                 .remove         = nft_bitmap_remove,
 308                 .deactivate     = nft_bitmap_deactivate,
 309                 .flush          = nft_bitmap_flush,
 310                 .activate       = nft_bitmap_activate,
 311                 .lookup         = nft_bitmap_lookup,
 312                 .walk           = nft_bitmap_walk,
 313                 .get            = nft_bitmap_get,
 314         },
 315 };