1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Copyright (c) 2006 Patrick McHardy <kaber@trash.net>
4  *
5  * Based on ipt_random and ipt_nth by Fabrice MARIE <fabrice@netfilter.org>.
6  */
7 
8 #include <linux/init.h>
9 #include <linux/spinlock.h>
10 #include <linux/skbuff.h>
11 #include <linux/net.h>
12 #include <linux/slab.h>
13 
14 #include <linux/netfilter/xt_statistic.h>
15 #include <linux/netfilter/x_tables.h>
16 #include <linux/module.h>
17 
18 struct xt_statistic_priv {
19 	atomic_t count;
20 } ____cacheline_aligned_in_smp;
21 
22 MODULE_LICENSE("GPL");
23 MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
24 MODULE_DESCRIPTION("Xtables: statistics-based matching (\"Nth\", random)");
25 MODULE_ALIAS("ipt_statistic");
26 MODULE_ALIAS("ip6t_statistic");
27 
28 static bool
statistic_mt(const struct sk_buff * skb,struct xt_action_param * par)29 statistic_mt(const struct sk_buff *skb, struct xt_action_param *par)
30 {
31 	const struct xt_statistic_info *info = par->matchinfo;
32 	bool ret = info->flags & XT_STATISTIC_INVERT;
33 	int nval, oval;
34 
35 	switch (info->mode) {
36 	case XT_STATISTIC_MODE_RANDOM:
37 		if ((get_random_u32() & 0x7FFFFFFF) < info->u.random.probability)
38 			ret = !ret;
39 		break;
40 	case XT_STATISTIC_MODE_NTH:
41 		do {
42 			oval = atomic_read(&info->master->count);
43 			nval = (oval == info->u.nth.every) ? 0 : oval + 1;
44 		} while (atomic_cmpxchg(&info->master->count, oval, nval) != oval);
45 		if (nval == 0)
46 			ret = !ret;
47 		break;
48 	}
49 
50 	return ret;
51 }
52 
statistic_mt_check(const struct xt_mtchk_param * par)53 static int statistic_mt_check(const struct xt_mtchk_param *par)
54 {
55 	struct xt_statistic_info *info = par->matchinfo;
56 
57 	if (info->mode > XT_STATISTIC_MODE_MAX ||
58 	    info->flags & ~XT_STATISTIC_MASK)
59 		return -EINVAL;
60 
61 	info->master = kzalloc(sizeof(*info->master), GFP_KERNEL);
62 	if (info->master == NULL)
63 		return -ENOMEM;
64 	atomic_set(&info->master->count, info->u.nth.count);
65 
66 	return 0;
67 }
68 
statistic_mt_destroy(const struct xt_mtdtor_param * par)69 static void statistic_mt_destroy(const struct xt_mtdtor_param *par)
70 {
71 	const struct xt_statistic_info *info = par->matchinfo;
72 
73 	kfree(info->master);
74 }
75 
76 static struct xt_match xt_statistic_mt_reg __read_mostly = {
77 	.name       = "statistic",
78 	.revision   = 0,
79 	.family     = NFPROTO_UNSPEC,
80 	.match      = statistic_mt,
81 	.checkentry = statistic_mt_check,
82 	.destroy    = statistic_mt_destroy,
83 	.matchsize  = sizeof(struct xt_statistic_info),
84 	.usersize   = offsetof(struct xt_statistic_info, master),
85 	.me         = THIS_MODULE,
86 };
87 
statistic_mt_init(void)88 static int __init statistic_mt_init(void)
89 {
90 	return xt_register_match(&xt_statistic_mt_reg);
91 }
92 
statistic_mt_exit(void)93 static void __exit statistic_mt_exit(void)
94 {
95 	xt_unregister_match(&xt_statistic_mt_reg);
96 }
97 
98 module_init(statistic_mt_init);
99 module_exit(statistic_mt_exit);
100