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 int nft_bitmap_insert(const struct net *net, const struct nft_set *set, 110 const struct nft_set_elem *elem, 111 struct nft_set_ext **ext) 112 { 113 struct nft_bitmap *priv = nft_set_priv(set); 114 struct nft_bitmap_elem *new = elem->priv, *be; 115 u8 genmask = nft_genmask_next(net); 116 u32 idx, off; 117 118 be = nft_bitmap_elem_find(set, new, genmask); 119 if (be) { 120 *ext = &be->ext; 121 return -EEXIST; 122 } 123 124 nft_bitmap_location(set, nft_set_ext_key(&new->ext), &idx, &off); 125 /* Enter 01 state. */ 126 priv->bitmap[idx] |= (genmask << off); 127 list_add_tail_rcu(&new->head, &priv->list); 128 129 return 0; 130 } 131 132 static void nft_bitmap_remove(const struct net *net, 133 const struct nft_set *set, 134 const struct nft_set_elem *elem) 135 { 136 struct nft_bitmap *priv = nft_set_priv(set); 137 struct nft_bitmap_elem *be = elem->priv; 138 u8 genmask = nft_genmask_next(net); 139 u32 idx, off; 140 141 nft_bitmap_location(set, nft_set_ext_key(&be->ext), &idx, &off); 142 /* Enter 00 state. */ 143 priv->bitmap[idx] &= ~(genmask << off); 144 list_del_rcu(&be->head); 145 } 146 147 static void nft_bitmap_activate(const struct net *net, 148 const struct nft_set *set, 149 const struct nft_set_elem *elem) 150 { 151 struct nft_bitmap *priv = nft_set_priv(set); 152 struct nft_bitmap_elem *be = elem->priv; 153 u8 genmask = nft_genmask_next(net); 154 u32 idx, off; 155 156 nft_bitmap_location(set, nft_set_ext_key(&be->ext), &idx, &off); 157 /* Enter 11 state. */ 158 priv->bitmap[idx] |= (genmask << off); 159 nft_set_elem_change_active(net, set, &be->ext); 160 } 161 162 static bool nft_bitmap_flush(const struct net *net, 163 const struct nft_set *set, void *_be) 164 { 165 struct nft_bitmap *priv = nft_set_priv(set); 166 u8 genmask = nft_genmask_next(net); 167 struct nft_bitmap_elem *be = _be; 168 u32 idx, off; 169 170 nft_bitmap_location(set, nft_set_ext_key(&be->ext), &idx, &off); 171 /* Enter 10 state, similar to deactivation. */ 172 priv->bitmap[idx] &= ~(genmask << off); 173 nft_set_elem_change_active(net, set, &be->ext); 174 175 return true; 176 } 177 178 static void *nft_bitmap_deactivate(const struct net *net, 179 const struct nft_set *set, 180 const struct nft_set_elem *elem) 181 { 182 struct nft_bitmap *priv = nft_set_priv(set); 183 struct nft_bitmap_elem *this = elem->priv, *be; 184 u8 genmask = nft_genmask_next(net); 185 u32 idx, off; 186 187 nft_bitmap_location(set, elem->key.val.data, &idx, &off); 188 189 be = nft_bitmap_elem_find(set, this, genmask); 190 if (!be) 191 return NULL; 192 193 /* Enter 10 state. */ 194 priv->bitmap[idx] &= ~(genmask << off); 195 nft_set_elem_change_active(net, set, &be->ext); 196 197 return be; 198 } 199 200 static void nft_bitmap_walk(const struct nft_ctx *ctx, 201 struct nft_set *set, 202 struct nft_set_iter *iter) 203 { 204 const struct nft_bitmap *priv = nft_set_priv(set); 205 struct nft_bitmap_elem *be; 206 struct nft_set_elem elem; 207 208 list_for_each_entry_rcu(be, &priv->list, head) { 209 if (iter->count < iter->skip) 210 goto cont; 211 if (!nft_set_elem_active(&be->ext, iter->genmask)) 212 goto cont; 213 214 elem.priv = be; 215 216 iter->err = iter->fn(ctx, set, iter, &elem); 217 218 if (iter->err < 0) 219 return; 220 cont: 221 iter->count++; 222 } 223 } 224 225 /* The bitmap size is pow(2, key length in bits) / bits per byte. This is 226 * multiplied by two since each element takes two bits. For 8 bit keys, the 227 * bitmap consumes 66 bytes. For 16 bit keys, 16388 bytes. 228 */ 229 static inline u32 nft_bitmap_size(u32 klen) 230 { 231 return ((2 << ((klen * BITS_PER_BYTE) - 1)) / BITS_PER_BYTE) << 1; 232 } 233 234 static inline u32 nft_bitmap_total_size(u32 klen) 235 { 236 return sizeof(struct nft_bitmap) + nft_bitmap_size(klen); 237 } 238 239 static unsigned int nft_bitmap_privsize(const struct nlattr * const nla[], 240 const struct nft_set_desc *desc) 241 { 242 u32 klen = ntohl(nla_get_be32(nla[NFTA_SET_KEY_LEN])); 243 244 return nft_bitmap_total_size(klen); 245 } 246 247 static int nft_bitmap_init(const struct nft_set *set, 248 const struct nft_set_desc *desc, 249 const struct nlattr * const nla[]) 250 { 251 struct nft_bitmap *priv = nft_set_priv(set); 252 253 INIT_LIST_HEAD(&priv->list); 254 priv->bitmap_size = nft_bitmap_size(set->klen); 255 256 return 0; 257 } 258 259 static void nft_bitmap_destroy(const struct nft_set *set) 260 { 261 struct nft_bitmap *priv = nft_set_priv(set); 262 struct nft_bitmap_elem *be, *n; 263 264 list_for_each_entry_safe(be, n, &priv->list, head) 265 nft_set_elem_destroy(set, be, true); 266 } 267 268 static bool nft_bitmap_estimate(const struct nft_set_desc *desc, u32 features, 269 struct nft_set_estimate *est) 270 { 271 /* Make sure bitmaps we don't get bitmaps larger than 16 Kbytes. */ 272 if (desc->klen > 2) 273 return false; 274 275 est->size = nft_bitmap_total_size(desc->klen); 276 est->lookup = NFT_SET_CLASS_O_1; 277 est->space = NFT_SET_CLASS_O_1; 278 279 return true; 280 } 281 282 static struct nft_set_type nft_bitmap_type; 283 static struct nft_set_ops nft_bitmap_ops __read_mostly = { 284 .type = &nft_bitmap_type, 285 .privsize = nft_bitmap_privsize, 286 .elemsize = offsetof(struct nft_bitmap_elem, ext), 287 .estimate = nft_bitmap_estimate, 288 .init = nft_bitmap_init, 289 .destroy = nft_bitmap_destroy, 290 .insert = nft_bitmap_insert, 291 .remove = nft_bitmap_remove, 292 .deactivate = nft_bitmap_deactivate, 293 .flush = nft_bitmap_flush, 294 .activate = nft_bitmap_activate, 295 .lookup = nft_bitmap_lookup, 296 .walk = nft_bitmap_walk, 297 }; 298 299 static struct nft_set_type nft_bitmap_type __read_mostly = { 300 .ops = &nft_bitmap_ops, 301 .owner = THIS_MODULE, 302 }; 303 304 static int __init nft_bitmap_module_init(void) 305 { 306 return nft_register_set(&nft_bitmap_type); 307 } 308 309 static void __exit nft_bitmap_module_exit(void) 310 { 311 nft_unregister_set(&nft_bitmap_type); 312 } 313 314 module_init(nft_bitmap_module_init); 315 module_exit(nft_bitmap_module_exit); 316 317 MODULE_LICENSE("GPL"); 318 MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>"); 319 MODULE_ALIAS_NFT_SET(); 320