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 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 */
46struct nft_bitmap {
47 struct list_head list;
48 u16 bitmap_size;
49 u8 bitmap[];
50};
51
52static 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 */
71static inline bool
72nft_bitmap_active(const u8 *bitmap, u32 idx, u32 off, u8 genmask)
73{
74 return (bitmap[idx] & (0x3 << off)) & (genmask << off);
75}
76
77INDIRECT_CALLABLE_SCOPE
78bool 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: &idx, off: &off);
86
87 return nft_bitmap_active(bitmap: priv->bitmap, idx, off, genmask);
88}
89
90static struct nft_bitmap_elem *
91nft_bitmap_elem_find(const struct nft_set *set, struct nft_bitmap_elem *this,
92 u8 genmask)
93{
94 const struct nft_bitmap *priv = nft_set_priv(set);
95 struct nft_bitmap_elem *be;
96
97 list_for_each_entry_rcu(be, &priv->list, head) {
98 if (memcmp(p: nft_set_ext_key(ext: &be->ext),
99 q: nft_set_ext_key(ext: &this->ext), size: set->klen) ||
100 !nft_set_elem_active(ext: &be->ext, genmask))
101 continue;
102
103 return be;
104 }
105 return NULL;
106}
107
108static struct nft_elem_priv *
109nft_bitmap_get(const struct net *net, const struct nft_set *set,
110 const struct nft_set_elem *elem, unsigned int flags)
111{
112 const struct nft_bitmap *priv = nft_set_priv(set);
113 u8 genmask = nft_genmask_cur(net);
114 struct nft_bitmap_elem *be;
115
116 list_for_each_entry_rcu(be, &priv->list, head) {
117 if (memcmp(p: nft_set_ext_key(ext: &be->ext), q: elem->key.val.data, size: set->klen) ||
118 !nft_set_elem_active(ext: &be->ext, genmask))
119 continue;
120
121 return &be->priv;
122 }
123 return ERR_PTR(error: -ENOENT);
124}
125
126static int nft_bitmap_insert(const struct net *net, const struct nft_set *set,
127 const struct nft_set_elem *elem,
128 struct nft_elem_priv **elem_priv)
129{
130 struct nft_bitmap_elem *new = nft_elem_priv_cast(priv: elem->priv), *be;
131 struct nft_bitmap *priv = nft_set_priv(set);
132 u8 genmask = nft_genmask_next(net);
133 u32 idx, off;
134
135 be = nft_bitmap_elem_find(set, this: new, genmask);
136 if (be) {
137 *elem_priv = &be->priv;
138 return -EEXIST;
139 }
140
141 nft_bitmap_location(set, key: nft_set_ext_key(ext: &new->ext), idx: &idx, off: &off);
142 /* Enter 01 state. */
143 priv->bitmap[idx] |= (genmask << off);
144 list_add_tail_rcu(new: &new->head, head: &priv->list);
145
146 return 0;
147}
148
149static void nft_bitmap_remove(const struct net *net, const struct nft_set *set,
150 struct nft_elem_priv *elem_priv)
151{
152 struct nft_bitmap_elem *be = nft_elem_priv_cast(priv: elem_priv);
153 struct nft_bitmap *priv = nft_set_priv(set);
154 u8 genmask = nft_genmask_next(net);
155 u32 idx, off;
156
157 nft_bitmap_location(set, key: nft_set_ext_key(ext: &be->ext), idx: &idx, off: &off);
158 /* Enter 00 state. */
159 priv->bitmap[idx] &= ~(genmask << off);
160 list_del_rcu(entry: &be->head);
161}
162
163static void nft_bitmap_activate(const struct net *net,
164 const struct nft_set *set,
165 struct nft_elem_priv *elem_priv)
166{
167 struct nft_bitmap_elem *be = nft_elem_priv_cast(priv: elem_priv);
168 struct nft_bitmap *priv = nft_set_priv(set);
169 u8 genmask = nft_genmask_next(net);
170 u32 idx, off;
171
172 nft_bitmap_location(set, key: nft_set_ext_key(ext: &be->ext), idx: &idx, off: &off);
173 /* Enter 11 state. */
174 priv->bitmap[idx] |= (genmask << off);
175 nft_set_elem_change_active(net, set, ext: &be->ext);
176}
177
178static void nft_bitmap_flush(const struct net *net,
179 const struct nft_set *set,
180 struct nft_elem_priv *elem_priv)
181{
182 struct nft_bitmap_elem *be = nft_elem_priv_cast(priv: elem_priv);
183 struct nft_bitmap *priv = nft_set_priv(set);
184 u8 genmask = nft_genmask_next(net);
185 u32 idx, off;
186
187 nft_bitmap_location(set, key: nft_set_ext_key(ext: &be->ext), idx: &idx, off: &off);
188 /* Enter 10 state, similar to deactivation. */
189 priv->bitmap[idx] &= ~(genmask << off);
190 nft_set_elem_change_active(net, set, ext: &be->ext);
191}
192
193static struct nft_elem_priv *
194nft_bitmap_deactivate(const struct net *net, const struct nft_set *set,
195 const struct nft_set_elem *elem)
196{
197 struct nft_bitmap_elem *this = nft_elem_priv_cast(priv: elem->priv), *be;
198 struct nft_bitmap *priv = nft_set_priv(set);
199 u8 genmask = nft_genmask_next(net);
200 u32 idx, off;
201
202 nft_bitmap_location(set, key: elem->key.val.data, idx: &idx, off: &off);
203
204 be = nft_bitmap_elem_find(set, this, genmask);
205 if (!be)
206 return NULL;
207
208 /* Enter 10 state. */
209 priv->bitmap[idx] &= ~(genmask << off);
210 nft_set_elem_change_active(net, set, ext: &be->ext);
211
212 return &be->priv;
213}
214
215static void nft_bitmap_walk(const struct nft_ctx *ctx,
216 struct nft_set *set,
217 struct nft_set_iter *iter)
218{
219 const struct nft_bitmap *priv = nft_set_priv(set);
220 struct nft_bitmap_elem *be;
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(ext: &be->ext, genmask: iter->genmask))
226 goto cont;
227
228 iter->err = iter->fn(ctx, set, iter, &be->priv);
229
230 if (iter->err < 0)
231 return;
232cont:
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 */
241static inline u32 nft_bitmap_size(u32 klen)
242{
243 return ((2 << ((klen * BITS_PER_BYTE) - 1)) / BITS_PER_BYTE) << 1;
244}
245
246static inline u64 nft_bitmap_total_size(u32 klen)
247{
248 return sizeof(struct nft_bitmap) + nft_bitmap_size(klen);
249}
250
251static 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
259static 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(list: &priv->list);
268 priv->bitmap_size = nft_bitmap_size(klen: set->klen);
269
270 return 0;
271}
272
273static 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, elem_priv: &be->priv);
281}
282
283static 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(klen: desc->klen);
293 est->lookup = NFT_SET_CLASS_O_1;
294 est->space = NFT_SET_CLASS_O_1;
295
296 return true;
297}
298
299const 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};
316

source code of linux/net/netfilter/nft_set_bitmap.c