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
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 ((prandom_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
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
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
88 static int __init statistic_mt_init(void)
89 {
90 return xt_register_match(&xt_statistic_mt_reg);
91 }
92
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
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