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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (c) 2016 Laura Garcia <nevola@gmail.com>
4 */
5
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 u8 dreg;
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 atomic_set(&priv->counter, priv->modulus - 1);
70
71 return nft_parse_register_store(ctx, tb[NFTA_NG_DREG], &priv->dreg,
72 NULL, NFT_DATA_VALUE, sizeof(u32));
73}
74
75static int nft_ng_dump(struct sk_buff *skb, enum nft_registers dreg,
76 u32 modulus, enum nft_ng_types type, u32 offset)
77{
78 if (nft_dump_register(skb, NFTA_NG_DREG, dreg))
79 goto nla_put_failure;
80 if (nla_put_be32(skb, NFTA_NG_MODULUS, htonl(modulus)))
81 goto nla_put_failure;
82 if (nla_put_be32(skb, NFTA_NG_TYPE, htonl(type)))
83 goto nla_put_failure;
84 if (nla_put_be32(skb, NFTA_NG_OFFSET, htonl(offset)))
85 goto nla_put_failure;
86
87 return 0;
88
89nla_put_failure:
90 return -1;
91}
92
93static int nft_ng_inc_dump(struct sk_buff *skb, const struct nft_expr *expr)
94{
95 const struct nft_ng_inc *priv = nft_expr_priv(expr);
96
97 return nft_ng_dump(skb, priv->dreg, priv->modulus, NFT_NG_INCREMENTAL,
98 priv->offset);
99}
100
101struct nft_ng_random {
102 u8 dreg;
103 u32 modulus;
104 u32 offset;
105};
106
107static u32 nft_ng_random_gen(struct nft_ng_random *priv)
108{
109 struct rnd_state *state = this_cpu_ptr(&nft_numgen_prandom_state);
110
111 return reciprocal_scale(prandom_u32_state(state), priv->modulus) +
112 priv->offset;
113}
114
115static void nft_ng_random_eval(const struct nft_expr *expr,
116 struct nft_regs *regs,
117 const struct nft_pktinfo *pkt)
118{
119 struct nft_ng_random *priv = nft_expr_priv(expr);
120
121 regs->data[priv->dreg] = nft_ng_random_gen(priv);
122}
123
124static int nft_ng_random_init(const struct nft_ctx *ctx,
125 const struct nft_expr *expr,
126 const struct nlattr * const tb[])
127{
128 struct nft_ng_random *priv = nft_expr_priv(expr);
129
130 if (tb[NFTA_NG_OFFSET])
131 priv->offset = ntohl(nla_get_be32(tb[NFTA_NG_OFFSET]));
132
133 priv->modulus = ntohl(nla_get_be32(tb[NFTA_NG_MODULUS]));
134 if (priv->modulus == 0)
135 return -ERANGE;
136
137 if (priv->offset + priv->modulus - 1 < priv->offset)
138 return -EOVERFLOW;
139
140 prandom_init_once(&nft_numgen_prandom_state);
141
142 return nft_parse_register_store(ctx, tb[NFTA_NG_DREG], &priv->dreg,
143 NULL, NFT_DATA_VALUE, sizeof(u32));
144}
145
146static int nft_ng_random_dump(struct sk_buff *skb, const struct nft_expr *expr)
147{
148 const struct nft_ng_random *priv = nft_expr_priv(expr);
149
150 return nft_ng_dump(skb, priv->dreg, priv->modulus, NFT_NG_RANDOM,
151 priv->offset);
152}
153
154static struct nft_expr_type nft_ng_type;
155static const struct nft_expr_ops nft_ng_inc_ops = {
156 .type = &nft_ng_type,
157 .size = NFT_EXPR_SIZE(sizeof(struct nft_ng_inc)),
158 .eval = nft_ng_inc_eval,
159 .init = nft_ng_inc_init,
160 .dump = nft_ng_inc_dump,
161};
162
163static const struct nft_expr_ops nft_ng_random_ops = {
164 .type = &nft_ng_type,
165 .size = NFT_EXPR_SIZE(sizeof(struct nft_ng_random)),
166 .eval = nft_ng_random_eval,
167 .init = nft_ng_random_init,
168 .dump = nft_ng_random_dump,
169};
170
171static const struct nft_expr_ops *
172nft_ng_select_ops(const struct nft_ctx *ctx, const struct nlattr * const tb[])
173{
174 u32 type;
175
176 if (!tb[NFTA_NG_DREG] ||
177 !tb[NFTA_NG_MODULUS] ||
178 !tb[NFTA_NG_TYPE])
179 return ERR_PTR(-EINVAL);
180
181 type = ntohl(nla_get_be32(tb[NFTA_NG_TYPE]));
182
183 switch (type) {
184 case NFT_NG_INCREMENTAL:
185 return &nft_ng_inc_ops;
186 case NFT_NG_RANDOM:
187 return &nft_ng_random_ops;
188 }
189
190 return ERR_PTR(-EINVAL);
191}
192
193static struct nft_expr_type nft_ng_type __read_mostly = {
194 .name = "numgen",
195 .select_ops = nft_ng_select_ops,
196 .policy = nft_ng_policy,
197 .maxattr = NFTA_NG_MAX,
198 .owner = THIS_MODULE,
199};
200
201static int __init nft_ng_module_init(void)
202{
203 return nft_register_expr(&nft_ng_type);
204}
205
206static void __exit nft_ng_module_exit(void)
207{
208 nft_unregister_expr(&nft_ng_type);
209}
210
211module_init(nft_ng_module_init);
212module_exit(nft_ng_module_exit);
213
214MODULE_LICENSE("GPL");
215MODULE_AUTHOR("Laura Garcia <nevola@gmail.com>");
216MODULE_ALIAS_NFT_EXPR("numgen");
217MODULE_DESCRIPTION("nftables number generator module");