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; 288 289 est->size = nft_bitmap_total_size(desc->klen); 290 est->lookup = NFT_SET_CLASS_O_1; 291 est->space = NFT_SET_CLASS_O_1; 292 293 return true; 294 } 295 296 struct nft_set_type nft_set_bitmap_type __read_mostly = { 297 .owner = THIS_MODULE, 298 .ops = { 299 .privsize = nft_bitmap_privsize, 300 .elemsize = offsetof(struct nft_bitmap_elem, ext), 301 .estimate = nft_bitmap_estimate, 302 .init = nft_bitmap_init, 303 .destroy = nft_bitmap_destroy, 304 .insert = nft_bitmap_insert, 305 .remove = nft_bitmap_remove, 306 .deactivate = nft_bitmap_deactivate, 307 .flush = nft_bitmap_flush, 308 .activate = nft_bitmap_activate, 309 .lookup = nft_bitmap_lookup, 310 .walk = nft_bitmap_walk, 311 .get = nft_bitmap_get, 312 }, 313 }; 314