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