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(priv->counter);
30		nval = (oval + 1 < priv->modulus) ? oval + 1 : 0;
31	} while (atomic_cmpxchg(priv->counter, oval, 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(sizeof(*priv->counter), GFP_KERNEL);
70	if (!priv->counter)
71		return -ENOMEM;
72
73	atomic_set(priv->counter, priv->modulus - 1);
74
75	err = nft_parse_register_store(ctx, tb[NFTA_NG_DREG], &priv->dreg,
76				       NULL, NFT_DATA_VALUE, sizeof(u32));
77	if (err < 0)
78		goto err;
79
80	return 0;
81err:
82	kfree(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, 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, NFTA_NG_DREG, dreg))
101		goto nla_put_failure;
102	if (nla_put_be32(skb, NFTA_NG_MODULUS, htonl(modulus)))
103		goto nla_put_failure;
104	if (nla_put_be32(skb, NFTA_NG_TYPE, htonl(type)))
105		goto nla_put_failure;
106	if (nla_put_be32(skb, 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, priv->dreg, priv->modulus, NFT_NG_INCREMENTAL,
121			   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(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(get_random_u32(), 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, tb[NFTA_NG_DREG], &priv->dreg,
169					NULL, NFT_DATA_VALUE, 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, priv->dreg, priv->modulus, NFT_NG_RANDOM,
178			   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, 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(-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(-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