1 /*
2 * Copyright (c) 2006 Patrick McHardy <kaber@trash.net>
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License version 2 as
6 * published by the Free Software Foundation.
7 *
8 * Based on ipt_random and ipt_nth by Fabrice MARIE <fabrice@netfilter.org>.
9 */
10
11 #include <linux/init.h>
12 #include <linux/spinlock.h>
13 #include <linux/skbuff.h>
14 #include <linux/net.h>
15 #include <linux/slab.h>
16
17 #include <linux/netfilter/xt_statistic.h>
18 #include <linux/netfilter/x_tables.h>
19 #include <linux/module.h>
20
21 struct xt_statistic_priv {
22 atomic_t count;
23 } ____cacheline_aligned_in_smp;
24
25 MODULE_LICENSE("GPL");
26 MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
27 MODULE_DESCRIPTION("Xtables: statistics-based matching (\"Nth\", random)");
28 MODULE_ALIAS("ipt_statistic");
29 MODULE_ALIAS("ip6t_statistic");
30
31 static bool
32 statistic_mt(const struct sk_buff *skb, struct xt_action_param *par)
33 {
34 const struct xt_statistic_info *info = par->matchinfo;
35 bool ret = info->flags & XT_STATISTIC_INVERT;
36 int nval, oval;
37
38 switch (info->mode) {
39 case XT_STATISTIC_MODE_RANDOM:
40 if ((prandom_u32() & 0x7FFFFFFF) < info->u.random.probability)
41 ret = !ret;
42 break;
43 case XT_STATISTIC_MODE_NTH:
44 do {
45 oval = atomic_read(&info->master->count);
46 nval = (oval == info->u.nth.every) ? 0 : oval + 1;
47 } while (atomic_cmpxchg(&info->master->count, oval, nval) != oval);
48 if (nval == 0)
49 ret = !ret;
50 break;
51 }
52
53 return ret;
54 }
55
56 static int statistic_mt_check(const struct xt_mtchk_param *par)
57 {
58 struct xt_statistic_info *info = par->matchinfo;
59
60 if (info->mode > XT_STATISTIC_MODE_MAX ||
61 info->flags & ~XT_STATISTIC_MASK)
62 return -EINVAL;
63
64 info->master = kzalloc(sizeof(*info->master), GFP_KERNEL);
65 if (info->master == NULL)
66 return -ENOMEM;
67 atomic_set(&info->master->count, info->u.nth.count);
68
69 return 0;
70 }
71
72 static void statistic_mt_destroy(const struct xt_mtdtor_param *par)
73 {
74 const struct xt_statistic_info *info = par->matchinfo;
75
76 kfree(info->master);
77 }
78
79 static struct xt_match xt_statistic_mt_reg __read_mostly = {
80 .name = "statistic",
81 .revision = 0,
82 .family = NFPROTO_UNSPEC,
83 .match = statistic_mt,
84 .checkentry = statistic_mt_check,
85 .destroy = statistic_mt_destroy,
86 .matchsize = sizeof(struct xt_statistic_info),
87 .me = THIS_MODULE,
88 };
89
90 static int __init statistic_mt_init(void)
91 {
92 return xt_register_match(&xt_statistic_mt_reg);
93 }
94
95 static void __exit statistic_mt_exit(void)
96 {
97 xt_unregister_match(&xt_statistic_mt_reg);
98 }
99
100 module_init(statistic_mt_init);
101 module_exit(statistic_mt_exit);
102
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.