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[linux-2.6/next.git] / net / netfilter / xt_statistic.c
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1 /*
2 * Copyright (c) 2006 Patrick McHardy <kaber@trash.net>
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.
8 * Based on ipt_random and ipt_nth by Fabrice MARIE <fabrice@netfilter.org>.
9 */
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>
17 #include <linux/netfilter/xt_statistic.h>
18 #include <linux/netfilter/x_tables.h>
20 struct xt_statistic_priv {
21 atomic_t count;
22 } ____cacheline_aligned_in_smp;
24 MODULE_LICENSE("GPL");
25 MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
26 MODULE_DESCRIPTION("Xtables: statistics-based matching (\"Nth\", random)");
27 MODULE_ALIAS("ipt_statistic");
28 MODULE_ALIAS("ip6t_statistic");
30 static bool
31 statistic_mt(const struct sk_buff *skb, struct xt_action_param *par)
33 const struct xt_statistic_info *info = par->matchinfo;
34 bool ret = info->flags & XT_STATISTIC_INVERT;
35 int nval, oval;
37 switch (info->mode) {
38 case XT_STATISTIC_MODE_RANDOM:
39 if ((net_random() & 0x7FFFFFFF) < info->u.random.probability)
40 ret = !ret;
41 break;
42 case XT_STATISTIC_MODE_NTH:
43 do {
44 oval = atomic_read(&info->master->count);
45 nval = (oval == info->u.nth.every) ? 0 : oval + 1;
46 } while (atomic_cmpxchg(&info->master->count, oval, nval) != oval);
47 if (nval == 0)
48 ret = !ret;
49 break;
52 return ret;
55 static int statistic_mt_check(const struct xt_mtchk_param *par)
57 struct xt_statistic_info *info = par->matchinfo;
59 if (info->mode > XT_STATISTIC_MODE_MAX ||
60 info->flags & ~XT_STATISTIC_MASK)
61 return -EINVAL;
63 info->master = kzalloc(sizeof(*info->master), GFP_KERNEL);
64 if (info->master == NULL)
65 return -ENOMEM;
66 atomic_set(&info->master->count, info->u.nth.count);
68 return 0;
71 static void statistic_mt_destroy(const struct xt_mtdtor_param *par)
73 const struct xt_statistic_info *info = par->matchinfo;
75 kfree(info->master);
78 static struct xt_match xt_statistic_mt_reg __read_mostly = {
79 .name = "statistic",
80 .revision = 0,
81 .family = NFPROTO_UNSPEC,
82 .match = statistic_mt,
83 .checkentry = statistic_mt_check,
84 .destroy = statistic_mt_destroy,
85 .matchsize = sizeof(struct xt_statistic_info),
86 .me = THIS_MODULE,
89 static int __init statistic_mt_init(void)
91 return xt_register_match(&xt_statistic_mt_reg);
94 static void __exit statistic_mt_exit(void)
96 xt_unregister_match(&xt_statistic_mt_reg);
99 module_init(statistic_mt_init);
100 module_exit(statistic_mt_exit);