Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/cooloney...
[linux-2.6] / net / netfilter / xt_statistic.c
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
19 MODULE_LICENSE("GPL");
20 MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
21 MODULE_DESCRIPTION("Xtables: statistics-based matching (\"Nth\", random)");
22 MODULE_ALIAS("ipt_statistic");
23 MODULE_ALIAS("ip6t_statistic");
24
25 static DEFINE_SPINLOCK(nth_lock);
26
27 static bool
28 statistic_mt(const struct sk_buff *skb, const struct xt_match_param *par)
29 {
30         struct xt_statistic_info *info = (void *)par->matchinfo;
31         bool ret = info->flags & XT_STATISTIC_INVERT;
32
33         switch (info->mode) {
34         case XT_STATISTIC_MODE_RANDOM:
35                 if ((net_random() & 0x7FFFFFFF) < info->u.random.probability)
36                         ret = !ret;
37                 break;
38         case XT_STATISTIC_MODE_NTH:
39                 info = info->master;
40                 spin_lock_bh(&nth_lock);
41                 if (info->u.nth.count++ == info->u.nth.every) {
42                         info->u.nth.count = 0;
43                         ret = !ret;
44                 }
45                 spin_unlock_bh(&nth_lock);
46                 break;
47         }
48
49         return ret;
50 }
51
52 static bool statistic_mt_check(const struct xt_mtchk_param *par)
53 {
54         struct xt_statistic_info *info = par->matchinfo;
55
56         if (info->mode > XT_STATISTIC_MODE_MAX ||
57             info->flags & ~XT_STATISTIC_MASK)
58                 return false;
59         info->master = info;
60         return true;
61 }
62
63 static struct xt_match xt_statistic_mt_reg __read_mostly = {
64         .name       = "statistic",
65         .revision   = 0,
66         .family     = NFPROTO_UNSPEC,
67         .match      = statistic_mt,
68         .checkentry = statistic_mt_check,
69         .matchsize  = sizeof(struct xt_statistic_info),
70         .me         = THIS_MODULE,
71 };
72
73 static int __init statistic_mt_init(void)
74 {
75         return xt_register_match(&xt_statistic_mt_reg);
76 }
77
78 static void __exit statistic_mt_exit(void)
79 {
80         xt_unregister_match(&xt_statistic_mt_reg);
81 }
82
83 module_init(statistic_mt_init);
84 module_exit(statistic_mt_exit);