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/random.h>
13#include <linux/static_key.h>
14#include <net/netfilter/nf_tables.h>
15#include <net/netfilter/nf_tables_core.h>
16
17struct nft_ng_inc {
18 u8 dreg;
19 u32 modulus;
20 atomic_t *counter;
21 u32 offset;
22};
23
24static u32 nft_ng_inc_gen(struct nft_ng_inc *priv)
25{
26 u32 nval, oval;
27
28 do {
29 oval = atomic_read(v: priv->counter);
30 nval = (oval + 1 < priv->modulus) ? oval + 1 : 0;
31 } while (atomic_cmpxchg(v: priv->counter, old: oval, new: nval) != oval);
32
33 return nval + priv->offset;
34}
35
36static void nft_ng_inc_eval(const struct nft_expr *expr,
37 struct nft_regs *regs,
38 const struct nft_pktinfo *pkt)
39{
40 struct nft_ng_inc *priv = nft_expr_priv(expr);
41
42 regs->data[priv->dreg] = nft_ng_inc_gen(priv);
43}
44
45static const struct nla_policy nft_ng_policy[NFTA_NG_MAX + 1] = {
46 [NFTA_NG_DREG] = { .type = NLA_U32 },
47 [NFTA_NG_MODULUS] = { .type = NLA_U32 },
48 [NFTA_NG_TYPE] = { .type = NLA_U32 },
49 [NFTA_NG_OFFSET] = { .type = NLA_U32 },
50};
51
52static int nft_ng_inc_init(const struct nft_ctx *ctx,
53 const struct nft_expr *expr,
54 const struct nlattr * const tb[])
55{
56 struct nft_ng_inc *priv = nft_expr_priv(expr);
57 int err;
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->counter = kmalloc(size: sizeof(*priv->counter), GFP_KERNEL);
70 if (!priv->counter)
71 return -ENOMEM;
72
73 atomic_set(v: priv->counter, i: priv->modulus - 1);
74
75 err = nft_parse_register_store(ctx, attr: tb[NFTA_NG_DREG], dreg: &priv->dreg,
76 NULL, type: NFT_DATA_VALUE, len: sizeof(u32));
77 if (err < 0)
78 goto err;
79
80 return 0;
81err:
82 kfree(objp: priv->counter);
83
84 return err;
85}
86
87static bool nft_ng_inc_reduce(struct nft_regs_track *track,
88 const struct nft_expr *expr)
89{
90 const struct nft_ng_inc *priv = nft_expr_priv(expr);
91
92 nft_reg_track_cancel(track, dreg: priv->dreg, NFT_REG32_SIZE);
93
94 return false;
95}
96
97static int nft_ng_dump(struct sk_buff *skb, enum nft_registers dreg,
98 u32 modulus, enum nft_ng_types type, u32 offset)
99{
100 if (nft_dump_register(skb, attr: NFTA_NG_DREG, reg: dreg))
101 goto nla_put_failure;
102 if (nla_put_be32(skb, attrtype: NFTA_NG_MODULUS, htonl(modulus)))
103 goto nla_put_failure;
104 if (nla_put_be32(skb, attrtype: NFTA_NG_TYPE, htonl(type)))
105 goto nla_put_failure;
106 if (nla_put_be32(skb, attrtype: NFTA_NG_OFFSET, htonl(offset)))
107 goto nla_put_failure;
108
109 return 0;
110
111nla_put_failure:
112 return -1;
113}
114
115static int nft_ng_inc_dump(struct sk_buff *skb,
116 const struct nft_expr *expr, bool reset)
117{
118 const struct nft_ng_inc *priv = nft_expr_priv(expr);
119
120 return nft_ng_dump(skb, dreg: priv->dreg, modulus: priv->modulus, type: NFT_NG_INCREMENTAL,
121 offset: priv->offset);
122}
123
124static void nft_ng_inc_destroy(const struct nft_ctx *ctx,
125 const struct nft_expr *expr)
126{
127 const struct nft_ng_inc *priv = nft_expr_priv(expr);
128
129 kfree(objp: priv->counter);
130}
131
132struct nft_ng_random {
133 u8 dreg;
134 u32 modulus;
135 u32 offset;
136};
137
138static u32 nft_ng_random_gen(const struct nft_ng_random *priv)
139{
140 return reciprocal_scale(val: get_random_u32(), ep_ro: priv->modulus) + priv->offset;
141}
142
143static void nft_ng_random_eval(const struct nft_expr *expr,
144 struct nft_regs *regs,
145 const struct nft_pktinfo *pkt)
146{
147 struct nft_ng_random *priv = nft_expr_priv(expr);
148
149 regs->data[priv->dreg] = nft_ng_random_gen(priv);
150}
151
152static int nft_ng_random_init(const struct nft_ctx *ctx,
153 const struct nft_expr *expr,
154 const struct nlattr * const tb[])
155{
156 struct nft_ng_random *priv = nft_expr_priv(expr);
157
158 if (tb[NFTA_NG_OFFSET])
159 priv->offset = ntohl(nla_get_be32(tb[NFTA_NG_OFFSET]));
160
161 priv->modulus = ntohl(nla_get_be32(tb[NFTA_NG_MODULUS]));
162 if (priv->modulus == 0)
163 return -ERANGE;
164
165 if (priv->offset + priv->modulus - 1 < priv->offset)
166 return -EOVERFLOW;
167
168 return nft_parse_register_store(ctx, attr: tb[NFTA_NG_DREG], dreg: &priv->dreg,
169 NULL, type: NFT_DATA_VALUE, len: sizeof(u32));
170}
171
172static int nft_ng_random_dump(struct sk_buff *skb,
173 const struct nft_expr *expr, bool reset)
174{
175 const struct nft_ng_random *priv = nft_expr_priv(expr);
176
177 return nft_ng_dump(skb, dreg: priv->dreg, modulus: priv->modulus, type: NFT_NG_RANDOM,
178 offset: priv->offset);
179}
180
181static bool nft_ng_random_reduce(struct nft_regs_track *track,
182 const struct nft_expr *expr)
183{
184 const struct nft_ng_random *priv = nft_expr_priv(expr);
185
186 nft_reg_track_cancel(track, dreg: priv->dreg, NFT_REG32_SIZE);
187
188 return false;
189}
190
191static struct nft_expr_type nft_ng_type;
192static const struct nft_expr_ops nft_ng_inc_ops = {
193 .type = &nft_ng_type,
194 .size = NFT_EXPR_SIZE(sizeof(struct nft_ng_inc)),
195 .eval = nft_ng_inc_eval,
196 .init = nft_ng_inc_init,
197 .destroy = nft_ng_inc_destroy,
198 .dump = nft_ng_inc_dump,
199 .reduce = nft_ng_inc_reduce,
200};
201
202static const struct nft_expr_ops nft_ng_random_ops = {
203 .type = &nft_ng_type,
204 .size = NFT_EXPR_SIZE(sizeof(struct nft_ng_random)),
205 .eval = nft_ng_random_eval,
206 .init = nft_ng_random_init,
207 .dump = nft_ng_random_dump,
208 .reduce = nft_ng_random_reduce,
209};
210
211static const struct nft_expr_ops *
212nft_ng_select_ops(const struct nft_ctx *ctx, const struct nlattr * const tb[])
213{
214 u32 type;
215
216 if (!tb[NFTA_NG_DREG] ||
217 !tb[NFTA_NG_MODULUS] ||
218 !tb[NFTA_NG_TYPE])
219 return ERR_PTR(error: -EINVAL);
220
221 type = ntohl(nla_get_be32(tb[NFTA_NG_TYPE]));
222
223 switch (type) {
224 case NFT_NG_INCREMENTAL:
225 return &nft_ng_inc_ops;
226 case NFT_NG_RANDOM:
227 return &nft_ng_random_ops;
228 }
229
230 return ERR_PTR(error: -EINVAL);
231}
232
233static struct nft_expr_type nft_ng_type __read_mostly = {
234 .name = "numgen",
235 .select_ops = nft_ng_select_ops,
236 .policy = nft_ng_policy,
237 .maxattr = NFTA_NG_MAX,
238 .owner = THIS_MODULE,
239};
240
241static int __init nft_ng_module_init(void)
242{
243 return nft_register_expr(&nft_ng_type);
244}
245
246static void __exit nft_ng_module_exit(void)
247{
248 nft_unregister_expr(&nft_ng_type);
249}
250
251module_init(nft_ng_module_init);
252module_exit(nft_ng_module_exit);
253
254MODULE_LICENSE("GPL");
255MODULE_AUTHOR("Laura Garcia <nevola@gmail.com>");
256MODULE_ALIAS_NFT_EXPR("numgen");
257MODULE_DESCRIPTION("nftables number generator module");
258

source code of linux/net/netfilter/nft_numgen.c