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
16#include <linux/netfilter/xt_statistic.h>
17#include <linux/netfilter/x_tables.h>
18
19MODULE_LICENSE("GPL");
20MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
21MODULE_DESCRIPTION("xtables statistical match module");
22MODULE_ALIAS("ipt_statistic");
23MODULE_ALIAS("ip6t_statistic");
24
25static DEFINE_SPINLOCK(nth_lock);
26
27static int
28match(const struct sk_buff *skb,
29      const struct net_device *in, const struct net_device *out,
30      const struct xt_match *match, const void *matchinfo,
31      int offset, unsigned int protoff, int *hotdrop)
32{
33	struct xt_statistic_info *info = (struct xt_statistic_info *)matchinfo;
34	int ret = info->flags & XT_STATISTIC_INVERT ? 1 : 0;
35
36	switch (info->mode) {
37	case XT_STATISTIC_MODE_RANDOM:
38		if ((net_random() & 0x7FFFFFFF) < info->u.random.probability)
39			ret ^= 1;
40		break;
41	case XT_STATISTIC_MODE_NTH:
42		info = info->master;
43		spin_lock_bh(&nth_lock);
44		if (info->u.nth.count++ == info->u.nth.every) {
45			info->u.nth.count = 0;
46			ret ^= 1;
47		}
48		spin_unlock_bh(&nth_lock);
49		break;
50	}
51
52	return ret;
53}
54
55static int
56checkentry(const char *tablename, const void *entry,
57	   const struct xt_match *match, void *matchinfo,
58	   unsigned int hook_mask)
59{
60	struct xt_statistic_info *info = (struct xt_statistic_info *)matchinfo;
61
62	if (info->mode > XT_STATISTIC_MODE_MAX ||
63	    info->flags & ~XT_STATISTIC_MASK)
64		return 0;
65	info->master = info;
66	return 1;
67}
68
69static struct xt_match xt_statistic_match[] = {
70	{
71		.name		= "statistic",
72		.family		= AF_INET,
73		.checkentry	= checkentry,
74		.match		= match,
75		.matchsize	= sizeof(struct xt_statistic_info),
76		.me		= THIS_MODULE,
77	},
78	{
79		.name		= "statistic",
80		.family		= AF_INET6,
81		.checkentry	= checkentry,
82		.match		= match,
83		.matchsize	= sizeof(struct xt_statistic_info),
84		.me		= THIS_MODULE,
85	},
86};
87
88static int __init xt_statistic_init(void)
89{
90	return xt_register_matches(xt_statistic_match,
91				   ARRAY_SIZE(xt_statistic_match));
92}
93
94static void __exit xt_statistic_fini(void)
95{
96	xt_unregister_matches(xt_statistic_match,
97			      ARRAY_SIZE(xt_statistic_match));
98}
99
100module_init(xt_statistic_init);
101module_exit(xt_statistic_fini);
102