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/*
* netfilter module to enforce network quotas
*
* Sam Johnston <samj@samj.net>
*/
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter/xt_quota.h>
#include <linux/module.h>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Sam Johnston <samj@samj.net>");
MODULE_DESCRIPTION("Xtables: countdown quota match");
MODULE_ALIAS("ipt_quota");
MODULE_ALIAS("ip6t_quota");
static bool
quota_mt(const struct sk_buff *skb, struct xt_action_param *par)
{
struct xt_quota_info *q = (void *)par->matchinfo;
u64 current_count = atomic64_read(&q->counter);
bool ret = q->flags & XT_QUOTA_INVERT;
u64 old_count, new_count;
do {
if (current_count == 1)
return ret;
if (current_count <= skb->len) {
atomic64_set(&q->counter, 1);
return ret;
}
old_count = current_count;
new_count = current_count - skb->len;
current_count = atomic64_cmpxchg(&q->counter, old_count,
new_count);
} while (current_count != old_count);
return !ret;
}
static int quota_mt_check(const struct xt_mtchk_param *par)
{
struct xt_quota_info *q = par->matchinfo;
BUILD_BUG_ON(sizeof(atomic64_t) != sizeof(__u64));
if (q->flags & ~XT_QUOTA_MASK)
return -EINVAL;
if (atomic64_read(&q->counter) > q->quota + 1)
return -ERANGE;
if (atomic64_read(&q->counter) == 0)
atomic64_set(&q->counter, q->quota + 1);
return 0;
}
static struct xt_match quota_mt_reg __read_mostly = {
.name = "quota",
.revision = 0,
.family = NFPROTO_UNSPEC,
.match = quota_mt,
.checkentry = quota_mt_check,
.matchsize = sizeof(struct xt_quota_info),
.me = THIS_MODULE,
};
static int __init quota_mt_init(void)
{
return xt_register_match("a_mt_reg);
}
static void __exit quota_mt_exit(void)
{
xt_unregister_match("a_mt_reg);
}
module_init(quota_mt_init);
module_exit(quota_mt_exit);
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