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Linux/net/netfilter/nft_numgen.c

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  1 /*
  2  * Copyright (c) 2016 Laura Garcia <nevola@gmail.com>
  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 
 10 #include <linux/kernel.h>
 11 #include <linux/init.h>
 12 #include <linux/module.h>
 13 #include <linux/netlink.h>
 14 #include <linux/netfilter.h>
 15 #include <linux/netfilter/nf_tables.h>
 16 #include <linux/static_key.h>
 17 #include <net/netfilter/nf_tables.h>
 18 #include <net/netfilter/nf_tables_core.h>
 19 
 20 static DEFINE_PER_CPU(struct rnd_state, nft_numgen_prandom_state);
 21 
 22 struct nft_ng_inc {
 23         enum nft_registers      dreg:8;
 24         u32                     modulus;
 25         atomic_t                counter;
 26         u32                     offset;
 27         struct nft_set          *map;
 28 };
 29 
 30 static u32 nft_ng_inc_gen(struct nft_ng_inc *priv)
 31 {
 32         u32 nval, oval;
 33 
 34         do {
 35                 oval = atomic_read(&priv->counter);
 36                 nval = (oval + 1 < priv->modulus) ? oval + 1 : 0;
 37         } while (atomic_cmpxchg(&priv->counter, oval, nval) != oval);
 38 
 39         return nval + priv->offset;
 40 }
 41 
 42 static void nft_ng_inc_eval(const struct nft_expr *expr,
 43                             struct nft_regs *regs,
 44                             const struct nft_pktinfo *pkt)
 45 {
 46         struct nft_ng_inc *priv = nft_expr_priv(expr);
 47 
 48         regs->data[priv->dreg] = nft_ng_inc_gen(priv);
 49 }
 50 
 51 static void nft_ng_inc_map_eval(const struct nft_expr *expr,
 52                                 struct nft_regs *regs,
 53                                 const struct nft_pktinfo *pkt)
 54 {
 55         struct nft_ng_inc *priv = nft_expr_priv(expr);
 56         const struct nft_set *map = priv->map;
 57         const struct nft_set_ext *ext;
 58         u32 result;
 59         bool found;
 60 
 61         result = nft_ng_inc_gen(priv);
 62         found = map->ops->lookup(nft_net(pkt), map, &result, &ext);
 63 
 64         if (!found)
 65                 return;
 66 
 67         nft_data_copy(&regs->data[priv->dreg],
 68                       nft_set_ext_data(ext), map->dlen);
 69 }
 70 
 71 static const struct nla_policy nft_ng_policy[NFTA_NG_MAX + 1] = {
 72         [NFTA_NG_DREG]          = { .type = NLA_U32 },
 73         [NFTA_NG_MODULUS]       = { .type = NLA_U32 },
 74         [NFTA_NG_TYPE]          = { .type = NLA_U32 },
 75         [NFTA_NG_OFFSET]        = { .type = NLA_U32 },
 76         [NFTA_NG_SET_NAME]      = { .type = NLA_STRING,
 77                                     .len = NFT_SET_MAXNAMELEN - 1 },
 78         [NFTA_NG_SET_ID]        = { .type = NLA_U32 },
 79 };
 80 
 81 static int nft_ng_inc_init(const struct nft_ctx *ctx,
 82                            const struct nft_expr *expr,
 83                            const struct nlattr * const tb[])
 84 {
 85         struct nft_ng_inc *priv = nft_expr_priv(expr);
 86 
 87         if (tb[NFTA_NG_OFFSET])
 88                 priv->offset = ntohl(nla_get_be32(tb[NFTA_NG_OFFSET]));
 89 
 90         priv->modulus = ntohl(nla_get_be32(tb[NFTA_NG_MODULUS]));
 91         if (priv->modulus == 0)
 92                 return -ERANGE;
 93 
 94         if (priv->offset + priv->modulus - 1 < priv->offset)
 95                 return -EOVERFLOW;
 96 
 97         priv->dreg = nft_parse_register(tb[NFTA_NG_DREG]);
 98         atomic_set(&priv->counter, priv->modulus - 1);
 99 
100         return nft_validate_register_store(ctx, priv->dreg, NULL,
101                                            NFT_DATA_VALUE, sizeof(u32));
102 }
103 
104 static int nft_ng_inc_map_init(const struct nft_ctx *ctx,
105                                const struct nft_expr *expr,
106                                const struct nlattr * const tb[])
107 {
108         struct nft_ng_inc *priv = nft_expr_priv(expr);
109         u8 genmask = nft_genmask_next(ctx->net);
110 
111         nft_ng_inc_init(ctx, expr, tb);
112 
113         priv->map = nft_set_lookup_global(ctx->net, ctx->table,
114                                           tb[NFTA_NG_SET_NAME],
115                                           tb[NFTA_NG_SET_ID], genmask);
116 
117         return PTR_ERR_OR_ZERO(priv->map);
118 }
119 
120 static int nft_ng_dump(struct sk_buff *skb, enum nft_registers dreg,
121                        u32 modulus, enum nft_ng_types type, u32 offset)
122 {
123         if (nft_dump_register(skb, NFTA_NG_DREG, dreg))
124                 goto nla_put_failure;
125         if (nla_put_be32(skb, NFTA_NG_MODULUS, htonl(modulus)))
126                 goto nla_put_failure;
127         if (nla_put_be32(skb, NFTA_NG_TYPE, htonl(type)))
128                 goto nla_put_failure;
129         if (nla_put_be32(skb, NFTA_NG_OFFSET, htonl(offset)))
130                 goto nla_put_failure;
131 
132         return 0;
133 
134 nla_put_failure:
135         return -1;
136 }
137 
138 static int nft_ng_inc_dump(struct sk_buff *skb, const struct nft_expr *expr)
139 {
140         const struct nft_ng_inc *priv = nft_expr_priv(expr);
141 
142         return nft_ng_dump(skb, priv->dreg, priv->modulus, NFT_NG_INCREMENTAL,
143                            priv->offset);
144 }
145 
146 static int nft_ng_inc_map_dump(struct sk_buff *skb,
147                                const struct nft_expr *expr)
148 {
149         const struct nft_ng_inc *priv = nft_expr_priv(expr);
150 
151         if (nft_ng_dump(skb, priv->dreg, priv->modulus,
152                         NFT_NG_INCREMENTAL, priv->offset) ||
153             nla_put_string(skb, NFTA_NG_SET_NAME, priv->map->name))
154                 goto nla_put_failure;
155 
156         return 0;
157 
158 nla_put_failure:
159         return -1;
160 }
161 
162 struct nft_ng_random {
163         enum nft_registers      dreg:8;
164         u32                     modulus;
165         u32                     offset;
166         struct nft_set          *map;
167 };
168 
169 static u32 nft_ng_random_gen(struct nft_ng_random *priv)
170 {
171         struct rnd_state *state = this_cpu_ptr(&nft_numgen_prandom_state);
172 
173         return reciprocal_scale(prandom_u32_state(state), priv->modulus) +
174                priv->offset;
175 }
176 
177 static void nft_ng_random_eval(const struct nft_expr *expr,
178                                struct nft_regs *regs,
179                                const struct nft_pktinfo *pkt)
180 {
181         struct nft_ng_random *priv = nft_expr_priv(expr);
182 
183         regs->data[priv->dreg] = nft_ng_random_gen(priv);
184 }
185 
186 static void nft_ng_random_map_eval(const struct nft_expr *expr,
187                                    struct nft_regs *regs,
188                                    const struct nft_pktinfo *pkt)
189 {
190         struct nft_ng_random *priv = nft_expr_priv(expr);
191         const struct nft_set *map = priv->map;
192         const struct nft_set_ext *ext;
193         u32 result;
194         bool found;
195 
196         result = nft_ng_random_gen(priv);
197         found = map->ops->lookup(nft_net(pkt), map, &result, &ext);
198         if (!found)
199                 return;
200 
201         nft_data_copy(&regs->data[priv->dreg],
202                       nft_set_ext_data(ext), map->dlen);
203 }
204 
205 static int nft_ng_random_init(const struct nft_ctx *ctx,
206                               const struct nft_expr *expr,
207                               const struct nlattr * const tb[])
208 {
209         struct nft_ng_random *priv = nft_expr_priv(expr);
210 
211         if (tb[NFTA_NG_OFFSET])
212                 priv->offset = ntohl(nla_get_be32(tb[NFTA_NG_OFFSET]));
213 
214         priv->modulus = ntohl(nla_get_be32(tb[NFTA_NG_MODULUS]));
215         if (priv->modulus == 0)
216                 return -ERANGE;
217 
218         if (priv->offset + priv->modulus - 1 < priv->offset)
219                 return -EOVERFLOW;
220 
221         prandom_init_once(&nft_numgen_prandom_state);
222 
223         priv->dreg = nft_parse_register(tb[NFTA_NG_DREG]);
224 
225         return nft_validate_register_store(ctx, priv->dreg, NULL,
226                                            NFT_DATA_VALUE, sizeof(u32));
227 }
228 
229 static int nft_ng_random_map_init(const struct nft_ctx *ctx,
230                                   const struct nft_expr *expr,
231                                   const struct nlattr * const tb[])
232 {
233         struct nft_ng_random *priv = nft_expr_priv(expr);
234         u8 genmask = nft_genmask_next(ctx->net);
235 
236         nft_ng_random_init(ctx, expr, tb);
237         priv->map = nft_set_lookup_global(ctx->net, ctx->table,
238                                           tb[NFTA_NG_SET_NAME],
239                                           tb[NFTA_NG_SET_ID], genmask);
240         if (IS_ERR(priv->map))
241                 return PTR_ERR(priv->map);
242 
243         return 0;
244 }
245 
246 static int nft_ng_random_dump(struct sk_buff *skb, const struct nft_expr *expr)
247 {
248         const struct nft_ng_random *priv = nft_expr_priv(expr);
249 
250         return nft_ng_dump(skb, priv->dreg, priv->modulus, NFT_NG_RANDOM,
251                            priv->offset);
252 }
253 
254 static int nft_ng_random_map_dump(struct sk_buff *skb,
255                                   const struct nft_expr *expr)
256 {
257         const struct nft_ng_random *priv = nft_expr_priv(expr);
258 
259         if (nft_ng_dump(skb, priv->dreg, priv->modulus,
260                         NFT_NG_RANDOM, priv->offset) ||
261             nla_put_string(skb, NFTA_NG_SET_NAME, priv->map->name))
262                 goto nla_put_failure;
263 
264         return 0;
265 
266 nla_put_failure:
267         return -1;
268 }
269 
270 static struct nft_expr_type nft_ng_type;
271 static const struct nft_expr_ops nft_ng_inc_ops = {
272         .type           = &nft_ng_type,
273         .size           = NFT_EXPR_SIZE(sizeof(struct nft_ng_inc)),
274         .eval           = nft_ng_inc_eval,
275         .init           = nft_ng_inc_init,
276         .dump           = nft_ng_inc_dump,
277 };
278 
279 static const struct nft_expr_ops nft_ng_inc_map_ops = {
280         .type           = &nft_ng_type,
281         .size           = NFT_EXPR_SIZE(sizeof(struct nft_ng_inc)),
282         .eval           = nft_ng_inc_map_eval,
283         .init           = nft_ng_inc_map_init,
284         .dump           = nft_ng_inc_map_dump,
285 };
286 
287 static const struct nft_expr_ops nft_ng_random_ops = {
288         .type           = &nft_ng_type,
289         .size           = NFT_EXPR_SIZE(sizeof(struct nft_ng_random)),
290         .eval           = nft_ng_random_eval,
291         .init           = nft_ng_random_init,
292         .dump           = nft_ng_random_dump,
293 };
294 
295 static const struct nft_expr_ops nft_ng_random_map_ops = {
296         .type           = &nft_ng_type,
297         .size           = NFT_EXPR_SIZE(sizeof(struct nft_ng_random)),
298         .eval           = nft_ng_random_map_eval,
299         .init           = nft_ng_random_map_init,
300         .dump           = nft_ng_random_map_dump,
301 };
302 
303 static const struct nft_expr_ops *
304 nft_ng_select_ops(const struct nft_ctx *ctx, const struct nlattr * const tb[])
305 {
306         u32 type;
307 
308         if (!tb[NFTA_NG_DREG]    ||
309             !tb[NFTA_NG_MODULUS] ||
310             !tb[NFTA_NG_TYPE])
311                 return ERR_PTR(-EINVAL);
312 
313         type = ntohl(nla_get_be32(tb[NFTA_NG_TYPE]));
314 
315         switch (type) {
316         case NFT_NG_INCREMENTAL:
317                 if (tb[NFTA_NG_SET_NAME])
318                         return &nft_ng_inc_map_ops;
319                 return &nft_ng_inc_ops;
320         case NFT_NG_RANDOM:
321                 if (tb[NFTA_NG_SET_NAME])
322                         return &nft_ng_random_map_ops;
323                 return &nft_ng_random_ops;
324         }
325 
326         return ERR_PTR(-EINVAL);
327 }
328 
329 static struct nft_expr_type nft_ng_type __read_mostly = {
330         .name           = "numgen",
331         .select_ops     = nft_ng_select_ops,
332         .policy         = nft_ng_policy,
333         .maxattr        = NFTA_NG_MAX,
334         .owner          = THIS_MODULE,
335 };
336 
337 static int __init nft_ng_module_init(void)
338 {
339         return nft_register_expr(&nft_ng_type);
340 }
341 
342 static void __exit nft_ng_module_exit(void)
343 {
344         nft_unregister_expr(&nft_ng_type);
345 }
346 
347 module_init(nft_ng_module_init);
348 module_exit(nft_ng_module_exit);
349 
350 MODULE_LICENSE("GPL");
351 MODULE_AUTHOR("Laura Garcia <nevola@gmail.com>");
352 MODULE_ALIAS_NFT_EXPR("numgen");
353 

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