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 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  */
  45 struct nft_bitmap {
  46         struct  list_head       list;
  47         u16                     bitmap_size;
  48         u8                      bitmap[];
  49 };
  50
  51 static 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  */
  70 static inline bool
  71 nft_bitmap_active(const u8 *bitmap, u32 idx, u32 off, u8 genmask)
  72 {
  73         return (bitmap[idx] & (0x3 << off)) & (genmask << off);
  74 }
  75
  76 static 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
  88 static struct nft_bitmap_elem *
  89 nft_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
 106 static 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
 123 static 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
 146 static 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
 161 static 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
 176 static 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
 192 static 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
 214 static 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;
 234 cont:
 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  */
 243 static inline u32 nft_bitmap_size(u32 klen)
 244 {
 245         return ((2 << ((klen * BITS_PER_BYTE) - 1)) / BITS_PER_BYTE) << 1;
 246 }
 247
 248 static inline u64 nft_bitmap_total_size(u32 klen)
 249 {
 250         return sizeof(struct nft_bitmap) + nft_bitmap_size(klen);
 251 }
 252
 253 static 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
 261 static 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
 273 static 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
 282 static 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
 298 const 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 };