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6#include <linux/kernel.h>
7#include <linux/init.h>
8#include <linux/module.h>
9#include <linux/netlink.h>
10#include <linux/netfilter.h>
11#include <linux/netfilter/nf_tables.h>
12#include <linux/static_key.h>
13#include <net/netfilter/nf_tables.h>
14#include <net/netfilter/nf_tables_core.h>
15
16static DEFINE_PER_CPU(struct rnd_state, nft_numgen_prandom_state);
17
18struct nft_ng_inc {
19 enum nft_registers dreg:8;
20 u32 modulus;
21 atomic_t counter;
22 u32 offset;
23};
24
25static u32 nft_ng_inc_gen(struct nft_ng_inc *priv)
26{
27 u32 nval, oval;
28
29 do {
30 oval = atomic_read(&priv->counter);
31 nval = (oval + 1 < priv->modulus) ? oval + 1 : 0;
32 } while (atomic_cmpxchg(&priv->counter, oval, nval) != oval);
33
34 return nval + priv->offset;
35}
36
37static void nft_ng_inc_eval(const struct nft_expr *expr,
38 struct nft_regs *regs,
39 const struct nft_pktinfo *pkt)
40{
41 struct nft_ng_inc *priv = nft_expr_priv(expr);
42
43 regs->data[priv->dreg] = nft_ng_inc_gen(priv);
44}
45
46static const struct nla_policy nft_ng_policy[NFTA_NG_MAX + 1] = {
47 [NFTA_NG_DREG] = { .type = NLA_U32 },
48 [NFTA_NG_MODULUS] = { .type = NLA_U32 },
49 [NFTA_NG_TYPE] = { .type = NLA_U32 },
50 [NFTA_NG_OFFSET] = { .type = NLA_U32 },
51};
52
53static int nft_ng_inc_init(const struct nft_ctx *ctx,
54 const struct nft_expr *expr,
55 const struct nlattr * const tb[])
56{
57 struct nft_ng_inc *priv = nft_expr_priv(expr);
58
59 if (tb[NFTA_NG_OFFSET])
60 priv->offset = ntohl(nla_get_be32(tb[NFTA_NG_OFFSET]));
61
62 priv->modulus = ntohl(nla_get_be32(tb[NFTA_NG_MODULUS]));
63 if (priv->modulus == 0)
64 return -ERANGE;
65
66 if (priv->offset + priv->modulus - 1 < priv->offset)
67 return -EOVERFLOW;
68
69 priv->dreg = nft_parse_register(tb[NFTA_NG_DREG]);
70 atomic_set(&priv->counter, priv->modulus - 1);
71
72 return nft_validate_register_store(ctx, priv->dreg, NULL,
73 NFT_DATA_VALUE, sizeof(u32));
74}
75
76static int nft_ng_dump(struct sk_buff *skb, enum nft_registers dreg,
77 u32 modulus, enum nft_ng_types type, u32 offset)
78{
79 if (nft_dump_register(skb, NFTA_NG_DREG, dreg))
80 goto nla_put_failure;
81 if (nla_put_be32(skb, NFTA_NG_MODULUS, htonl(modulus)))
82 goto nla_put_failure;
83 if (nla_put_be32(skb, NFTA_NG_TYPE, htonl(type)))
84 goto nla_put_failure;
85 if (nla_put_be32(skb, NFTA_NG_OFFSET, htonl(offset)))
86 goto nla_put_failure;
87
88 return 0;
89
90nla_put_failure:
91 return -1;
92}
93
94static int nft_ng_inc_dump(struct sk_buff *skb, const struct nft_expr *expr)
95{
96 const struct nft_ng_inc *priv = nft_expr_priv(expr);
97
98 return nft_ng_dump(skb, priv->dreg, priv->modulus, NFT_NG_INCREMENTAL,
99 priv->offset);
100}
101
102struct nft_ng_random {
103 enum nft_registers dreg:8;
104 u32 modulus;
105 u32 offset;
106};
107
108static u32 nft_ng_random_gen(struct nft_ng_random *priv)
109{
110 struct rnd_state *state = this_cpu_ptr(&nft_numgen_prandom_state);
111
112 return reciprocal_scale(prandom_u32_state(state), priv->modulus) +
113 priv->offset;
114}
115
116static void nft_ng_random_eval(const struct nft_expr *expr,
117 struct nft_regs *regs,
118 const struct nft_pktinfo *pkt)
119{
120 struct nft_ng_random *priv = nft_expr_priv(expr);
121
122 regs->data[priv->dreg] = nft_ng_random_gen(priv);
123}
124
125static int nft_ng_random_init(const struct nft_ctx *ctx,
126 const struct nft_expr *expr,
127 const struct nlattr * const tb[])
128{
129 struct nft_ng_random *priv = nft_expr_priv(expr);
130
131 if (tb[NFTA_NG_OFFSET])
132 priv->offset = ntohl(nla_get_be32(tb[NFTA_NG_OFFSET]));
133
134 priv->modulus = ntohl(nla_get_be32(tb[NFTA_NG_MODULUS]));
135 if (priv->modulus == 0)
136 return -ERANGE;
137
138 if (priv->offset + priv->modulus - 1 < priv->offset)
139 return -EOVERFLOW;
140
141 prandom_init_once(&nft_numgen_prandom_state);
142
143 priv->dreg = nft_parse_register(tb[NFTA_NG_DREG]);
144
145 return nft_validate_register_store(ctx, priv->dreg, NULL,
146 NFT_DATA_VALUE, sizeof(u32));
147}
148
149static int nft_ng_random_dump(struct sk_buff *skb, const struct nft_expr *expr)
150{
151 const struct nft_ng_random *priv = nft_expr_priv(expr);
152
153 return nft_ng_dump(skb, priv->dreg, priv->modulus, NFT_NG_RANDOM,
154 priv->offset);
155}
156
157static struct nft_expr_type nft_ng_type;
158static const struct nft_expr_ops nft_ng_inc_ops = {
159 .type = &nft_ng_type,
160 .size = NFT_EXPR_SIZE(sizeof(struct nft_ng_inc)),
161 .eval = nft_ng_inc_eval,
162 .init = nft_ng_inc_init,
163 .dump = nft_ng_inc_dump,
164};
165
166static const struct nft_expr_ops nft_ng_random_ops = {
167 .type = &nft_ng_type,
168 .size = NFT_EXPR_SIZE(sizeof(struct nft_ng_random)),
169 .eval = nft_ng_random_eval,
170 .init = nft_ng_random_init,
171 .dump = nft_ng_random_dump,
172};
173
174static const struct nft_expr_ops *
175nft_ng_select_ops(const struct nft_ctx *ctx, const struct nlattr * const tb[])
176{
177 u32 type;
178
179 if (!tb[NFTA_NG_DREG] ||
180 !tb[NFTA_NG_MODULUS] ||
181 !tb[NFTA_NG_TYPE])
182 return ERR_PTR(-EINVAL);
183
184 type = ntohl(nla_get_be32(tb[NFTA_NG_TYPE]));
185
186 switch (type) {
187 case NFT_NG_INCREMENTAL:
188 return &nft_ng_inc_ops;
189 case NFT_NG_RANDOM:
190 return &nft_ng_random_ops;
191 }
192
193 return ERR_PTR(-EINVAL);
194}
195
196static struct nft_expr_type nft_ng_type __read_mostly = {
197 .name = "numgen",
198 .select_ops = nft_ng_select_ops,
199 .policy = nft_ng_policy,
200 .maxattr = NFTA_NG_MAX,
201 .owner = THIS_MODULE,
202};
203
204static int __init nft_ng_module_init(void)
205{
206 return nft_register_expr(&nft_ng_type);
207}
208
209static void __exit nft_ng_module_exit(void)
210{
211 nft_unregister_expr(&nft_ng_type);
212}
213
214module_init(nft_ng_module_init);
215module_exit(nft_ng_module_exit);
216
217MODULE_LICENSE("GPL");
218MODULE_AUTHOR("Laura Garcia <nevola@gmail.com>");
219MODULE_ALIAS_NFT_EXPR("numgen");
220MODULE_DESCRIPTION("nftables number generator module");
221
