From 1da662b8735070809afacaba9e51ac171452c757 Mon Sep 17 00:00:00 2001 From: Bart De Schuymer Date: Thu, 18 Sep 2003 18:48:56 +0000 Subject: *** empty log message *** --- kernel/linux/net/bridge/netfilter/ebt_limit.c | 123 ++++++++++++++++++++++++++ 1 file changed, 123 insertions(+) create mode 100644 kernel/linux/net/bridge/netfilter/ebt_limit.c (limited to 'kernel') diff --git a/kernel/linux/net/bridge/netfilter/ebt_limit.c b/kernel/linux/net/bridge/netfilter/ebt_limit.c new file mode 100644 index 0000000..5947e56 --- /dev/null +++ b/kernel/linux/net/bridge/netfilter/ebt_limit.c @@ -0,0 +1,123 @@ +/* + * ebt_limit + * + * Authors: + * Tom Marshall + * + * Mostly copied from netfilter's ipt_limit.c + * + * September, 2003 + * + */ + +#include +#include +#include + +#include +#include + +/* The algorithm used is the Simple Token Bucket Filter (TBF) + * see net/sched/sch_tbf.c in the linux source tree + */ + +static spinlock_t limit_lock = SPIN_LOCK_UNLOCKED; + +/* Rusty: This is my (non-mathematically-inclined) understanding of + this algorithm. The `average rate' in jiffies becomes your initial + amount of credit `credit' and the most credit you can ever have + `credit_cap'. The `peak rate' becomes the cost of passing the + test, `cost'. + + `prev' tracks the last packet hit: you gain one credit per jiffy. + If you get credit balance more than this, the extra credit is + discarded. Every time the match passes, you lose `cost' credits; + if you don't have that many, the test fails. + + See Alexey's formal explanation in net/sched/sch_tbf.c. + + To avoid underflow, we multiply by 128 (ie. you get 128 credits per + jiffy). Hence a cost of 2^32-1, means one pass per 32768 seconds + at 1024HZ (or one every 9 hours). A cost of 1 means 12800 passes + per second at 100HZ. */ + +#define CREDITS_PER_JIFFY 128 + +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: %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 = +{ + {NULL, NULL}, EBT_LIMIT_MATCH, ebt_limit_match, ebt_limit_check, NULL, + 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); +EXPORT_NO_SYMBOLS; +MODULE_LICENSE("GPL"); -- cgit v1.2.3