linux/net/netfilter/nft_set_bitmap.c
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   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
  15struct nft_bitmap_elem {
  16        struct list_head        head;
  17        struct nft_set_ext      ext;
  18};
  19
  20/* This bitmap uses two bits to represent one element. These two bits determine
  21 * the element state in the current and the future generation.
  22 *
  23 * An element can be in three states. The generation cursor is represented using
  24 * the ^ character, note that this cursor shifts on every succesful transaction.
  25 * If no transaction is going on, we observe all elements are in the following
  26 * state:
  27 *
  28 * 11 = this element is active in the current generation. In case of no updates,
  29 * ^    it stays active in the next generation.
  30 * 00 = this element is inactive in the current generation. In case of no
  31 * ^    updates, it stays inactive in the next generation.
  32 *
  33 * On transaction handling, we observe these two temporary states:
  34 *
  35 * 01 = this element is inactive in the current generation and it becomes active
  36 * ^    in the next one. This happens when the element is inserted but commit
  37 *      path has not yet been executed yet, so activation is still pending. On
  38 *      transaction abortion, the element is removed.
  39 * 10 = this element is active in the current generation and it becomes inactive
  40 * ^    in the next one. This happens when the element is deactivated but commit
  41 *      path has not yet been executed yet, so removal is still pending. On
  42 *      transation abortion, the next generation bit is reset to go back to
  43 *      restore its previous state.
  44 */
  45struct nft_bitmap {
  46        struct  list_head       list;
  47        u16                     bitmap_size;
  48        u8                      bitmap[];
  49};
  50
  51static inline void nft_bitmap_location(const struct nft_set *set,
  52                                       const void *key,
  53                                       u32 *idx, u32 *off)
  54{
  55        u32 k;
  56
  57        if (set->klen == 2)
  58                k = *(u16 *)key;
  59        else
  60                k = *(u8 *)key;
  61        k <<= 1;
  62
  63        *idx = k / BITS_PER_BYTE;
  64        *off = k % BITS_PER_BYTE;
  65}
  66
  67/* Fetch the two bits that represent the element and check if it is active based
  68 * on the generation mask.
  69 */
  70static inline bool
  71nft_bitmap_active(const u8 *bitmap, u32 idx, u32 off, u8 genmask)
  72{
  73        return (bitmap[idx] & (0x3 << off)) & (genmask << off);
  74}
  75
  76static bool nft_bitmap_lookup(const struct net *net, const struct nft_set *set,
  77                              const u32 *key, const struct nft_set_ext **ext)
  78{
  79        const struct nft_bitmap *priv = nft_set_priv(set);
  80        u8 genmask = nft_genmask_cur(net);
  81        u32 idx, off;
  82
  83        nft_bitmap_location(set, key, &idx, &off);
  84
  85        return nft_bitmap_active(priv->bitmap, idx, off, genmask);
  86}
  87
  88static struct nft_bitmap_elem *
  89nft_bitmap_elem_find(const struct nft_set *set, struct nft_bitmap_elem *this,
  90                     u8 genmask)
  91{
  92        const struct nft_bitmap *priv = nft_set_priv(set);
  93        struct nft_bitmap_elem *be;
  94
  95        list_for_each_entry_rcu(be, &priv->list, head) {
  96                if (memcmp(nft_set_ext_key(&be->ext),
  97                           nft_set_ext_key(&this->ext), set->klen) ||
  98                    !nft_set_elem_active(&be->ext, genmask))
  99                        continue;
 100
 101                return be;
 102        }
 103        return NULL;
 104}
 105
 106static void *nft_bitmap_get(const struct net *net, const struct nft_set *set,
 107                            const struct nft_set_elem *elem, unsigned int flags)
 108{
 109        const struct nft_bitmap *priv = nft_set_priv(set);
 110        u8 genmask = nft_genmask_cur(net);
 111        struct nft_bitmap_elem *be;
 112
 113        list_for_each_entry_rcu(be, &priv->list, head) {
 114                if (memcmp(nft_set_ext_key(&be->ext), elem->key.val.data, set->klen) ||
 115                    !nft_set_elem_active(&be->ext, genmask))
 116                        continue;
 117
 118                return be;
 119        }
 120        return ERR_PTR(-ENOENT);
 121}
 122
 123static int nft_bitmap_insert(const struct net *net, const struct nft_set *set,
 124                             const struct nft_set_elem *elem,
 125                             struct nft_set_ext **ext)
 126{
 127        struct nft_bitmap *priv = nft_set_priv(set);
 128        struct nft_bitmap_elem *new = elem->priv, *be;
 129        u8 genmask = nft_genmask_next(net);
 130        u32 idx, off;
 131
 132        be = nft_bitmap_elem_find(set, new, genmask);
 133        if (be) {
 134                *ext = &be->ext;
 135                return -EEXIST;
 136        }
 137
 138        nft_bitmap_location(set, nft_set_ext_key(&new->ext), &idx, &off);
 139        /* Enter 01 state. */
 140        priv->bitmap[idx] |= (genmask << off);
 141        list_add_tail_rcu(&new->head, &priv->list);
 142
 143        return 0;
 144}
 145
 146static void nft_bitmap_remove(const struct net *net,
 147                              const struct nft_set *set,
 148                              const struct nft_set_elem *elem)
 149{
 150        struct nft_bitmap *priv = nft_set_priv(set);
 151        struct nft_bitmap_elem *be = elem->priv;
 152        u8 genmask = nft_genmask_next(net);
 153        u32 idx, off;
 154
 155        nft_bitmap_location(set, nft_set_ext_key(&be->ext), &idx, &off);
 156        /* Enter 00 state. */
 157        priv->bitmap[idx] &= ~(genmask << off);
 158        list_del_rcu(&be->head);
 159}
 160
 161static void nft_bitmap_activate(const struct net *net,
 162                                const struct nft_set *set,
 163                                const struct nft_set_elem *elem)
 164{
 165        struct nft_bitmap *priv = nft_set_priv(set);
 166        struct nft_bitmap_elem *be = elem->priv;
 167        u8 genmask = nft_genmask_next(net);
 168        u32 idx, off;
 169
 170        nft_bitmap_location(set, nft_set_ext_key(&be->ext), &idx, &off);
 171        /* Enter 11 state. */
 172        priv->bitmap[idx] |= (genmask << off);
 173        nft_set_elem_change_active(net, set, &be->ext);
 174}
 175
 176static bool nft_bitmap_flush(const struct net *net,
 177                             const struct nft_set *set, void *_be)
 178{
 179        struct nft_bitmap *priv = nft_set_priv(set);
 180        u8 genmask = nft_genmask_next(net);
 181        struct nft_bitmap_elem *be = _be;
 182        u32 idx, off;
 183
 184        nft_bitmap_location(set, nft_set_ext_key(&be->ext), &idx, &off);
 185        /* Enter 10 state, similar to deactivation. */
 186        priv->bitmap[idx] &= ~(genmask << off);
 187        nft_set_elem_change_active(net, set, &be->ext);
 188
 189        return true;
 190}
 191
 192static void *nft_bitmap_deactivate(const struct net *net,
 193                                   const struct nft_set *set,
 194                                   const struct nft_set_elem *elem)
 195{
 196        struct nft_bitmap *priv = nft_set_priv(set);
 197        struct nft_bitmap_elem *this = elem->priv, *be;
 198        u8 genmask = nft_genmask_next(net);
 199        u32 idx, off;
 200
 201        nft_bitmap_location(set, elem->key.val.data, &idx, &off);
 202
 203        be = nft_bitmap_elem_find(set, this, genmask);
 204        if (!be)
 205                return NULL;
 206
 207        /* Enter 10 state. */
 208        priv->bitmap[idx] &= ~(genmask << off);
 209        nft_set_elem_change_active(net, set, &be->ext);
 210
 211        return be;
 212}
 213
 214static void nft_bitmap_walk(const struct nft_ctx *ctx,
 215                            struct nft_set *set,
 216                            struct nft_set_iter *iter)
 217{
 218        const struct nft_bitmap *priv = nft_set_priv(set);
 219        struct nft_bitmap_elem *be;
 220        struct nft_set_elem elem;
 221
 222        list_for_each_entry_rcu(be, &priv->list, head) {
 223                if (iter->count < iter->skip)
 224                        goto cont;
 225                if (!nft_set_elem_active(&be->ext, iter->genmask))
 226                        goto cont;
 227
 228                elem.priv = be;
 229
 230                iter->err = iter->fn(ctx, set, iter, &elem);
 231
 232                if (iter->err < 0)
 233                        return;
 234cont:
 235                iter->count++;
 236        }
 237}
 238
 239/* The bitmap size is pow(2, key length in bits) / bits per byte. This is
 240 * multiplied by two since each element takes two bits. For 8 bit keys, the
 241 * bitmap consumes 66 bytes. For 16 bit keys, 16388 bytes.
 242 */
 243static inline u32 nft_bitmap_size(u32 klen)
 244{
 245        return ((2 << ((klen * BITS_PER_BYTE) - 1)) / BITS_PER_BYTE) << 1;
 246}
 247
 248static inline u64 nft_bitmap_total_size(u32 klen)
 249{
 250        return sizeof(struct nft_bitmap) + nft_bitmap_size(klen);
 251}
 252
 253static u64 nft_bitmap_privsize(const struct nlattr * const nla[],
 254                               const struct nft_set_desc *desc)
 255{
 256        u32 klen = ntohl(nla_get_be32(nla[NFTA_SET_KEY_LEN]));
 257
 258        return nft_bitmap_total_size(klen);
 259}
 260
 261static int nft_bitmap_init(const struct nft_set *set,
 262                           const struct nft_set_desc *desc,
 263                           const struct nlattr * const nla[])
 264{
 265        struct nft_bitmap *priv = nft_set_priv(set);
 266
 267        INIT_LIST_HEAD(&priv->list);
 268        priv->bitmap_size = nft_bitmap_size(set->klen);
 269
 270        return 0;
 271}
 272
 273static void nft_bitmap_destroy(const struct nft_set *set)
 274{
 275        struct nft_bitmap *priv = nft_set_priv(set);
 276        struct nft_bitmap_elem *be, *n;
 277
 278        list_for_each_entry_safe(be, n, &priv->list, head)
 279                nft_set_elem_destroy(set, be, true);
 280}
 281
 282static bool nft_bitmap_estimate(const struct nft_set_desc *desc, u32 features,
 283                                struct nft_set_estimate *est)
 284{
 285        /* Make sure bitmaps we don't get bitmaps larger than 16 Kbytes. */
 286        if (desc->klen > 2)
 287                return false;
 288        else if (desc->expr)
 289                return false;
 290
 291        est->size   = nft_bitmap_total_size(desc->klen);
 292        est->lookup = NFT_SET_CLASS_O_1;
 293        est->space  = NFT_SET_CLASS_O_1;
 294
 295        return true;
 296}
 297
 298const struct nft_set_type nft_set_bitmap_type = {
 299        .ops            = {
 300                .privsize       = nft_bitmap_privsize,
 301                .elemsize       = offsetof(struct nft_bitmap_elem, ext),
 302                .estimate       = nft_bitmap_estimate,
 303                .init           = nft_bitmap_init,
 304                .destroy        = nft_bitmap_destroy,
 305                .insert         = nft_bitmap_insert,
 306                .remove         = nft_bitmap_remove,
 307                .deactivate     = nft_bitmap_deactivate,
 308                .flush          = nft_bitmap_flush,
 309                .activate       = nft_bitmap_activate,
 310                .lookup         = nft_bitmap_lookup,
 311                .walk           = nft_bitmap_walk,
 312                .get            = nft_bitmap_get,
 313        },
 314};
 315