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/*
* Copyright (c) 2006 Patrick McHardy <kaber@trash.net>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* Based on ipt_random and ipt_nth by Fabrice MARIE <fabrice@netfilter.org>.
*/
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/skbuff.h>
#include <linux/net.h>
#include <linux/slab.h>
#include <linux/netfilter/xt_statistic.h>
#include <linux/netfilter/x_tables.h>
#include <linux/module.h>
struct xt_statistic_priv {
atomic_t count;
} ____cacheline_aligned_in_smp;
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
MODULE_DESCRIPTION("Xtables: statistics-based matching (\"Nth\", random)");
MODULE_ALIAS("ipt_statistic");
MODULE_ALIAS("ip6t_statistic");
static bool
statistic_mt(const struct sk_buff *skb, struct xt_action_param *par)
{
const struct xt_statistic_info *info = par->matchinfo;
bool ret = info->flags & XT_STATISTIC_INVERT;
int nval, oval;
switch (info->mode) {
case XT_STATISTIC_MODE_RANDOM:
if ((net_random() & 0x7FFFFFFF) < info->u.random.probability)
ret = !ret;
break;
case XT_STATISTIC_MODE_NTH:
do {
oval = atomic_read(&info->master->count);
nval = (oval == info->u.nth.every) ? 0 : oval + 1;
} while (atomic_cmpxchg(&info->master->count, oval, nval) != oval);
if (nval == 0)
ret = !ret;
break;
}
return ret;
}
static int statistic_mt_check(const struct xt_mtchk_param *par)
{
struct xt_statistic_info *info = par->matchinfo;
if (info->mode > XT_STATISTIC_MODE_MAX ||
info->flags & ~XT_STATISTIC_MASK)
return -EINVAL;
info->master = kzalloc(sizeof(*info->master), GFP_KERNEL);
if (info->master == NULL)
return -ENOMEM;
atomic_set(&info->master->count, info->u.nth.count);
return 0;
}
static void statistic_mt_destroy(const struct xt_mtdtor_param *par)
{
const struct xt_statistic_info *info = par->matchinfo;
kfree(info->master);
}
static struct xt_match xt_statistic_mt_reg __read_mostly = {
.name = "statistic",
.revision = 0,
.family = NFPROTO_UNSPEC,
.match = statistic_mt,
.checkentry = statistic_mt_check,
.destroy = statistic_mt_destroy,
.matchsize = sizeof(struct xt_statistic_info),
.me = THIS_MODULE,
};
static int __init statistic_mt_init(void)
{
return xt_register_match(&xt_statistic_mt_reg);
}
static void __exit statistic_mt_exit(void)
{
xt_unregister_match(&xt_statistic_mt_reg);
}
module_init(statistic_mt_init);
module_exit(statistic_mt_exit);
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