/* *  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 spinlock_t limit_lock = SPIN_LOCK_UNLOCKED;#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_tuser2credits(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 init(void){	return ebt_register_match(&ebt_limit_reg);}static void __exit fini(void){	ebt_unregister_match(&ebt_limit_reg);}module_init(init);module_exit(fini);MODULE_LICENSE("GPL");