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 void *nft_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(nft_set_ext_key(&be->ext), elem->key.val.data, set->klen) ||
118 		    !nft_set_elem_active(&be->ext, genmask))
119 			continue;
120 
121 		return be;
122 	}
123 	return ERR_PTR(-ENOENT);
124 }
125 
126 static int nft_bitmap_insert(const struct net *net, const struct nft_set *set,
127 			     const struct nft_set_elem *elem,
128 			     struct nft_set_ext **ext)
129 {
130 	struct nft_bitmap *priv = nft_set_priv(set);
131 	struct nft_bitmap_elem *new = elem->priv, *be;
132 	u8 genmask = nft_genmask_next(net);
133 	u32 idx, off;
134 
135 	be = nft_bitmap_elem_find(set, new, genmask);
136 	if (be) {
137 		*ext = &be->ext;
138 		return -EEXIST;
139 	}
140 
141 	nft_bitmap_location(set, nft_set_ext_key(&new->ext), &idx, &off);
142 	/* Enter 01 state. */
143 	priv->bitmap[idx] |= (genmask << off);
144 	list_add_tail_rcu(&new->head, &priv->list);
145 
146 	return 0;
147 }
148 
149 static void nft_bitmap_remove(const struct net *net,
150 			      const struct nft_set *set,
151 			      const struct nft_set_elem *elem)
152 {
153 	struct nft_bitmap *priv = nft_set_priv(set);
154 	struct nft_bitmap_elem *be = elem->priv;
155 	u8 genmask = nft_genmask_next(net);
156 	u32 idx, off;
157 
158 	nft_bitmap_location(set, nft_set_ext_key(&be->ext), &idx, &off);
159 	/* Enter 00 state. */
160 	priv->bitmap[idx] &= ~(genmask << off);
161 	list_del_rcu(&be->head);
162 }
163 
164 static void nft_bitmap_activate(const struct net *net,
165 				const struct nft_set *set,
166 				const struct nft_set_elem *elem)
167 {
168 	struct nft_bitmap *priv = nft_set_priv(set);
169 	struct nft_bitmap_elem *be = elem->priv;
170 	u8 genmask = nft_genmask_next(net);
171 	u32 idx, off;
172 
173 	nft_bitmap_location(set, nft_set_ext_key(&be->ext), &idx, &off);
174 	/* Enter 11 state. */
175 	priv->bitmap[idx] |= (genmask << off);
176 	nft_set_elem_change_active(net, set, &be->ext);
177 }
178 
179 static bool nft_bitmap_flush(const struct net *net,
180 			     const struct nft_set *set, void *_be)
181 {
182 	struct nft_bitmap *priv = nft_set_priv(set);
183 	u8 genmask = nft_genmask_next(net);
184 	struct nft_bitmap_elem *be = _be;
185 	u32 idx, off;
186 
187 	nft_bitmap_location(set, nft_set_ext_key(&be->ext), &idx, &off);
188 	/* Enter 10 state, similar to deactivation. */
189 	priv->bitmap[idx] &= ~(genmask << off);
190 	nft_set_elem_change_active(net, set, &be->ext);
191 
192 	return true;
193 }
194 
195 static void *nft_bitmap_deactivate(const struct net *net,
196 				   const struct nft_set *set,
197 				   const struct nft_set_elem *elem)
198 {
199 	struct nft_bitmap *priv = nft_set_priv(set);
200 	struct nft_bitmap_elem *this = elem->priv, *be;
201 	u8 genmask = nft_genmask_next(net);
202 	u32 idx, off;
203 
204 	nft_bitmap_location(set, elem->key.val.data, &idx, &off);
205 
206 	be = nft_bitmap_elem_find(set, this, genmask);
207 	if (!be)
208 		return NULL;
209 
210 	/* Enter 10 state. */
211 	priv->bitmap[idx] &= ~(genmask << off);
212 	nft_set_elem_change_active(net, set, &be->ext);
213 
214 	return be;
215 }
216 
217 static void nft_bitmap_walk(const struct nft_ctx *ctx,
218 			    struct nft_set *set,
219 			    struct nft_set_iter *iter)
220 {
221 	const struct nft_bitmap *priv = nft_set_priv(set);
222 	struct nft_bitmap_elem *be;
223 	struct nft_set_elem elem;
224 
225 	list_for_each_entry_rcu(be, &priv->list, head) {
226 		if (iter->count < iter->skip)
227 			goto cont;
228 		if (!nft_set_elem_active(&be->ext, iter->genmask))
229 			goto cont;
230 
231 		elem.priv = be;
232 
233 		iter->err = iter->fn(ctx, set, iter, &elem);
234 
235 		if (iter->err < 0)
236 			return;
237 cont:
238 		iter->count++;
239 	}
240 }
241 
242 /* The bitmap size is pow(2, key length in bits) / bits per byte. This is
243  * multiplied by two since each element takes two bits. For 8 bit keys, the
244  * bitmap consumes 66 bytes. For 16 bit keys, 16388 bytes.
245  */
246 static inline u32 nft_bitmap_size(u32 klen)
247 {
248 	return ((2 << ((klen * BITS_PER_BYTE) - 1)) / BITS_PER_BYTE) << 1;
249 }
250 
251 static inline u32 nft_bitmap_total_size(u32 klen)
252 {
253 	return sizeof(struct nft_bitmap) + nft_bitmap_size(klen);
254 }
255 
256 static unsigned int nft_bitmap_privsize(const struct nlattr * const nla[],
257 					const struct nft_set_desc *desc)
258 {
259 	u32 klen = ntohl(nla_get_be32(nla[NFTA_SET_KEY_LEN]));
260 
261 	return nft_bitmap_total_size(klen);
262 }
263 
264 static int nft_bitmap_init(const struct nft_set *set,
265 			 const struct nft_set_desc *desc,
266 			 const struct nlattr * const nla[])
267 {
268 	struct nft_bitmap *priv = nft_set_priv(set);
269 
270 	INIT_LIST_HEAD(&priv->list);
271 	priv->bitmap_size = nft_bitmap_size(set->klen);
272 
273 	return 0;
274 }
275 
276 static void nft_bitmap_destroy(const struct nft_set *set)
277 {
278 	struct nft_bitmap *priv = nft_set_priv(set);
279 	struct nft_bitmap_elem *be, *n;
280 
281 	list_for_each_entry_safe(be, n, &priv->list, head)
282 		nft_set_elem_destroy(set, be, true);
283 }
284 
285 static bool nft_bitmap_estimate(const struct nft_set_desc *desc, u32 features,
286 				struct nft_set_estimate *est)
287 {
288 	/* Make sure bitmaps we don't get bitmaps larger than 16 Kbytes. */
289 	if (desc->klen > 2)
290 		return false;
291 
292 	est->size   = nft_bitmap_total_size(desc->klen);
293 	est->lookup = NFT_SET_CLASS_O_1;
294 	est->space  = NFT_SET_CLASS_O_1;
295 
296 	return true;
297 }
298 
299 static struct nft_set_type nft_bitmap_type;
300 static struct nft_set_ops nft_bitmap_ops __read_mostly = {
301 	.type		= &nft_bitmap_type,
302 	.privsize	= nft_bitmap_privsize,
303 	.elemsize	= offsetof(struct nft_bitmap_elem, ext),
304 	.estimate	= nft_bitmap_estimate,
305 	.init		= nft_bitmap_init,
306 	.destroy	= nft_bitmap_destroy,
307 	.insert		= nft_bitmap_insert,
308 	.remove		= nft_bitmap_remove,
309 	.deactivate	= nft_bitmap_deactivate,
310 	.flush		= nft_bitmap_flush,
311 	.activate	= nft_bitmap_activate,
312 	.lookup		= nft_bitmap_lookup,
313 	.walk		= nft_bitmap_walk,
314 	.get		= nft_bitmap_get,
315 };
316 
317 static struct nft_set_type nft_bitmap_type __read_mostly = {
318 	.ops		= &nft_bitmap_ops,
319 	.owner		= THIS_MODULE,
320 };
321 
322 static int __init nft_bitmap_module_init(void)
323 {
324 	return nft_register_set(&nft_bitmap_type);
325 }
326 
327 static void __exit nft_bitmap_module_exit(void)
328 {
329 	nft_unregister_set(&nft_bitmap_type);
330 }
331 
332 module_init(nft_bitmap_module_init);
333 module_exit(nft_bitmap_module_exit);
334 
335 MODULE_LICENSE("GPL");
336 MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>");
337 MODULE_ALIAS_NFT_SET();
338