diff options
Diffstat (limited to 'net/bridge/netfilter/ebt_limit.c')
-rw-r--r-- | net/bridge/netfilter/ebt_limit.c | 113 |
1 files changed, 113 insertions, 0 deletions
diff --git a/net/bridge/netfilter/ebt_limit.c b/net/bridge/netfilter/ebt_limit.c new file mode 100644 index 0000000..637c884 --- /dev/null +++ b/net/bridge/netfilter/ebt_limit.c @@ -0,0 +1,113 @@ +/* + * 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 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"); |