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TOMOYO Linux Cross Reference
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 };
 28 
 29 static void nft_ng_inc_eval(const struct nft_expr *expr,
 30                             struct nft_regs *regs,
 31                             const struct nft_pktinfo *pkt)
 32 {
 33         struct nft_ng_inc *priv = nft_expr_priv(expr);
 34         u32 nval, oval;
 35 
 36         do {
 37                 oval = atomic_read(&priv->counter);
 38                 nval = (oval + 1 < priv->modulus) ? oval + 1 : 0;
 39         } while (atomic_cmpxchg(&priv->counter, oval, nval) != oval);
 40 
 41         regs->data[priv->dreg] = nval + priv->offset;
 42 }
 43 
 44 static const struct nla_policy nft_ng_policy[NFTA_NG_MAX + 1] = {
 45         [NFTA_NG_DREG]          = { .type = NLA_U32 },
 46         [NFTA_NG_MODULUS]       = { .type = NLA_U32 },
 47         [NFTA_NG_TYPE]          = { .type = NLA_U32 },
 48         [NFTA_NG_OFFSET]        = { .type = NLA_U32 },
 49 };
 50 
 51 static int nft_ng_inc_init(const struct nft_ctx *ctx,
 52                            const struct nft_expr *expr,
 53                            const struct nlattr * const tb[])
 54 {
 55         struct nft_ng_inc *priv = nft_expr_priv(expr);
 56 
 57         if (tb[NFTA_NG_OFFSET])
 58                 priv->offset = ntohl(nla_get_be32(tb[NFTA_NG_OFFSET]));
 59 
 60         priv->modulus = ntohl(nla_get_be32(tb[NFTA_NG_MODULUS]));
 61         if (priv->modulus == 0)
 62                 return -ERANGE;
 63 
 64         if (priv->offset + priv->modulus - 1 < priv->offset)
 65                 return -EOVERFLOW;
 66 
 67         priv->dreg = nft_parse_register(tb[NFTA_NG_DREG]);
 68         atomic_set(&priv->counter, priv->modulus - 1);
 69 
 70         return nft_validate_register_store(ctx, priv->dreg, NULL,
 71                                            NFT_DATA_VALUE, sizeof(u32));
 72 }
 73 
 74 static int nft_ng_dump(struct sk_buff *skb, enum nft_registers dreg,
 75                        u32 modulus, enum nft_ng_types type, u32 offset)
 76 {
 77         if (nft_dump_register(skb, NFTA_NG_DREG, dreg))
 78                 goto nla_put_failure;
 79         if (nla_put_be32(skb, NFTA_NG_MODULUS, htonl(modulus)))
 80                 goto nla_put_failure;
 81         if (nla_put_be32(skb, NFTA_NG_TYPE, htonl(type)))
 82                 goto nla_put_failure;
 83         if (nla_put_be32(skb, NFTA_NG_OFFSET, htonl(offset)))
 84                 goto nla_put_failure;
 85 
 86         return 0;
 87 
 88 nla_put_failure:
 89         return -1;
 90 }
 91 
 92 static int nft_ng_inc_dump(struct sk_buff *skb, const struct nft_expr *expr)
 93 {
 94         const struct nft_ng_inc *priv = nft_expr_priv(expr);
 95 
 96         return nft_ng_dump(skb, priv->dreg, priv->modulus, NFT_NG_INCREMENTAL,
 97                            priv->offset);
 98 }
 99 
100 struct nft_ng_random {
101         enum nft_registers      dreg:8;
102         u32                     modulus;
103         u32                     offset;
104 };
105 
106 static void nft_ng_random_eval(const struct nft_expr *expr,
107                                struct nft_regs *regs,
108                                const struct nft_pktinfo *pkt)
109 {
110         struct nft_ng_random *priv = nft_expr_priv(expr);
111         struct rnd_state *state = this_cpu_ptr(&nft_numgen_prandom_state);
112         u32 val;
113 
114         val = reciprocal_scale(prandom_u32_state(state), priv->modulus);
115         regs->data[priv->dreg] = val + priv->offset;
116 }
117 
118 static int nft_ng_random_init(const struct nft_ctx *ctx,
119                               const struct nft_expr *expr,
120                               const struct nlattr * const tb[])
121 {
122         struct nft_ng_random *priv = nft_expr_priv(expr);
123 
124         if (tb[NFTA_NG_OFFSET])
125                 priv->offset = ntohl(nla_get_be32(tb[NFTA_NG_OFFSET]));
126 
127         priv->modulus = ntohl(nla_get_be32(tb[NFTA_NG_MODULUS]));
128         if (priv->modulus == 0)
129                 return -ERANGE;
130 
131         if (priv->offset + priv->modulus - 1 < priv->offset)
132                 return -EOVERFLOW;
133 
134         prandom_init_once(&nft_numgen_prandom_state);
135 
136         priv->dreg = nft_parse_register(tb[NFTA_NG_DREG]);
137 
138         return nft_validate_register_store(ctx, priv->dreg, NULL,
139                                            NFT_DATA_VALUE, sizeof(u32));
140 }
141 
142 static int nft_ng_random_dump(struct sk_buff *skb, const struct nft_expr *expr)
143 {
144         const struct nft_ng_random *priv = nft_expr_priv(expr);
145 
146         return nft_ng_dump(skb, priv->dreg, priv->modulus, NFT_NG_RANDOM,
147                            priv->offset);
148 }
149 
150 static struct nft_expr_type nft_ng_type;
151 static const struct nft_expr_ops nft_ng_inc_ops = {
152         .type           = &nft_ng_type,
153         .size           = NFT_EXPR_SIZE(sizeof(struct nft_ng_inc)),
154         .eval           = nft_ng_inc_eval,
155         .init           = nft_ng_inc_init,
156         .dump           = nft_ng_inc_dump,
157 };
158 
159 static const struct nft_expr_ops nft_ng_random_ops = {
160         .type           = &nft_ng_type,
161         .size           = NFT_EXPR_SIZE(sizeof(struct nft_ng_random)),
162         .eval           = nft_ng_random_eval,
163         .init           = nft_ng_random_init,
164         .dump           = nft_ng_random_dump,
165 };
166 
167 static const struct nft_expr_ops *
168 nft_ng_select_ops(const struct nft_ctx *ctx, const struct nlattr * const tb[])
169 {
170         u32 type;
171 
172         if (!tb[NFTA_NG_DREG]    ||
173             !tb[NFTA_NG_MODULUS] ||
174             !tb[NFTA_NG_TYPE])
175                 return ERR_PTR(-EINVAL);
176 
177         type = ntohl(nla_get_be32(tb[NFTA_NG_TYPE]));
178 
179         switch (type) {
180         case NFT_NG_INCREMENTAL:
181                 return &nft_ng_inc_ops;
182         case NFT_NG_RANDOM:
183                 return &nft_ng_random_ops;
184         }
185 
186         return ERR_PTR(-EINVAL);
187 }
188 
189 static struct nft_expr_type nft_ng_type __read_mostly = {
190         .name           = "numgen",
191         .select_ops     = nft_ng_select_ops,
192         .policy         = nft_ng_policy,
193         .maxattr        = NFTA_NG_MAX,
194         .owner          = THIS_MODULE,
195 };
196 
197 static int __init nft_ng_module_init(void)
198 {
199         return nft_register_expr(&nft_ng_type);
200 }
201 
202 static void __exit nft_ng_module_exit(void)
203 {
204         nft_unregister_expr(&nft_ng_type);
205 }
206 
207 module_init(nft_ng_module_init);
208 module_exit(nft_ng_module_exit);
209 
210 MODULE_LICENSE("GPL");
211 MODULE_AUTHOR("Laura Garcia <nevola@gmail.com>");
212 MODULE_ALIAS_NFT_EXPR("numgen");
213 

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