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/*
* ebt_limit
*
* Authors:
* Tom Marshall <tommy@home.tig-grr.com>
*
* Mostly copied from netfilter's ipt_limit.c, see that file for
* more explanation
*
* September, 2003
*
*/
#include <linux/netfilter_bridge/ebtables.h>
#include <linux/netfilter_bridge/ebt_limit.h>
#include <linux/module.h>
#include <linux/netdevice.h>
#include <linux/spinlock.h>
static DEFINE_SPINLOCK(limit_lock);
#define MAX_CPJ (0xFFFFFFFF / (HZ*60*60*24))
#define _POW2_BELOW2(x) ((x)|((x)>>1))
#define _POW2_BELOW4(x) (_POW2_BELOW2(x)|_POW2_BELOW2((x)>>2))
#define _POW2_BELOW8(x) (_POW2_BELOW4(x)|_POW2_BELOW4((x)>>4))
#define _POW2_BELOW16(x) (_POW2_BELOW8(x)|_POW2_BELOW8((x)>>8))
#define _POW2_BELOW32(x) (_POW2_BELOW16(x)|_POW2_BELOW16((x)>>16))
#define POW2_BELOW32(x) ((_POW2_BELOW32(x)>>1) + 1)
#define CREDITS_PER_JIFFY POW2_BELOW32(MAX_CPJ)
static int ebt_limit_match(const struct sk_buff *skb,
const struct net_device *in, const struct net_device *out,
const void *data, unsigned int datalen)
{
struct ebt_limit_info *info = (struct ebt_limit_info *)data;
unsigned long now = jiffies;
spin_lock_bh(&limit_lock);
info->credit += (now - xchg(&info->prev, now)) * CREDITS_PER_JIFFY;
if (info->credit > info->credit_cap)
info->credit = info->credit_cap;
if (info->credit >= info->cost) {
/* We're not limited. */
info->credit -= info->cost;
spin_unlock_bh(&limit_lock);
return EBT_MATCH;
}
spin_unlock_bh(&limit_lock);
return EBT_NOMATCH;
}
/* Precision saver. */
static u_int32_t
user2credits(u_int32_t user)
{
/* If multiplying would overflow... */
if (user > 0xFFFFFFFF / (HZ*CREDITS_PER_JIFFY))
/* Divide first. */
return (user / EBT_LIMIT_SCALE) * HZ * CREDITS_PER_JIFFY;
return (user * HZ * CREDITS_PER_JIFFY) / EBT_LIMIT_SCALE;
}
static int ebt_limit_check(const char *tablename, unsigned int hookmask,
const struct ebt_entry *e, void *data, unsigned int datalen)
{
struct ebt_limit_info *info = (struct ebt_limit_info *)data;
if (datalen != EBT_ALIGN(sizeof(struct ebt_limit_info)))
return -EINVAL;
/* Check for overflow. */
if (info->burst == 0 ||
user2credits(info->avg * info->burst) < user2credits(info->avg)) {
printk("Overflow in ebt_limit, try lower: %u/%u\n",
info->avg, info->burst);
return -EINVAL;
}
/* User avg in seconds * EBT_LIMIT_SCALE: convert to jiffies * 128. */
info->prev = jiffies;
info->credit = user2credits(info->avg * info->burst);
info->credit_cap = user2credits(info->avg * info->burst);
info->cost = user2credits(info->avg);
return 0;
}
static struct ebt_match ebt_limit_reg =
{
.name = EBT_LIMIT_MATCH,
.match = ebt_limit_match,
.check = ebt_limit_check,
.me = THIS_MODULE,
};
static int __init ebt_limit_init(void)
{
return ebt_register_match(&ebt_limit_reg);
}
static void __exit ebt_limit_fini(void)
{
ebt_unregister_match(&ebt_limit_reg);
}
module_init(ebt_limit_init);
module_exit(ebt_limit_fini);
MODULE_LICENSE("GPL");
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