diff options
Diffstat (limited to 'net/ipv4/netfilter/ipt_limit.c')
| -rw-r--r-- | net/ipv4/netfilter/ipt_limit.c | 157 |
1 files changed, 157 insertions, 0 deletions
diff --git a/net/ipv4/netfilter/ipt_limit.c b/net/ipv4/netfilter/ipt_limit.c new file mode 100644 index 000000000000..0c24dcc703a5 --- /dev/null +++ b/net/ipv4/netfilter/ipt_limit.c @@ -0,0 +1,157 @@ +/* Kernel module to control the rate + * + * 2 September 1999: Changed from the target RATE to the match + * `limit', removed logging. Did I mention that + * Alexey is a fucking genius? + * Rusty Russell (rusty@rustcorp.com.au). */ + +/* (C) 1999 Jérôme de Vivie <devivie@info.enserb.u-bordeaux.fr> + * (C) 1999 Hervé Eychenne <eychenne@info.enserb.u-bordeaux.fr> + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + */ + +#include <linux/module.h> +#include <linux/skbuff.h> +#include <linux/spinlock.h> +#include <linux/interrupt.h> + +#include <linux/netfilter_ipv4/ip_tables.h> +#include <linux/netfilter_ipv4/ipt_limit.h> + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Herve Eychenne <rv@wallfire.org>"); +MODULE_DESCRIPTION("iptables rate limit match"); + +/* The algorithm used is the Simple Token Bucket Filter (TBF) + * see net/sched/sch_tbf.c in the linux source tree + */ + +static DEFINE_SPINLOCK(limit_lock); + +/* 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 get the maxmum range, we multiply by this factor (ie. you get N + credits per jiffy). We want to allow a rate as low as 1 per day + (slowest userspace tool allows), which means + CREDITS_PER_JIFFY*HZ*60*60*24 < 2^32. ie. */ +#define MAX_CPJ (0xFFFFFFFF / (HZ*60*60*24)) + +/* Repeated shift and or gives us all 1s, final shift and add 1 gives + * us the power of 2 below the theoretical max, so GCC simply does a + * shift. */ +#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 +ipt_limit_match(const struct sk_buff *skb, + const struct net_device *in, + const struct net_device *out, + const void *matchinfo, + int offset, + int *hotdrop) +{ + struct ipt_rateinfo *r = ((struct ipt_rateinfo *)matchinfo)->master; + unsigned long now = jiffies; + + spin_lock_bh(&limit_lock); + r->credit += (now - xchg(&r->prev, now)) * CREDITS_PER_JIFFY; + if (r->credit > r->credit_cap) + r->credit = r->credit_cap; + + if (r->credit >= r->cost) { + /* We're not limited. */ + r->credit -= r->cost; + spin_unlock_bh(&limit_lock); + return 1; + } + + spin_unlock_bh(&limit_lock); + return 0; +} + +/* 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 / IPT_LIMIT_SCALE) * HZ * CREDITS_PER_JIFFY; + + return (user * HZ * CREDITS_PER_JIFFY) / IPT_LIMIT_SCALE; +} + +static int +ipt_limit_checkentry(const char *tablename, + const struct ipt_ip *ip, + void *matchinfo, + unsigned int matchsize, + unsigned int hook_mask) +{ + struct ipt_rateinfo *r = matchinfo; + + if (matchsize != IPT_ALIGN(sizeof(struct ipt_rateinfo))) + return 0; + + /* Check for overflow. */ + if (r->burst == 0 + || user2credits(r->avg * r->burst) < user2credits(r->avg)) { + printk("Overflow in ipt_limit, try lower: %u/%u\n", + r->avg, r->burst); + return 0; + } + + /* User avg in seconds * IPT_LIMIT_SCALE: convert to jiffies * + 128. */ + r->prev = jiffies; + r->credit = user2credits(r->avg * r->burst); /* Credits full. */ + r->credit_cap = user2credits(r->avg * r->burst); /* Credits full. */ + r->cost = user2credits(r->avg); + + /* For SMP, we only want to use one set of counters. */ + r->master = r; + + return 1; +} + +static struct ipt_match ipt_limit_reg = { + .name = "limit", + .match = ipt_limit_match, + .checkentry = ipt_limit_checkentry, + .me = THIS_MODULE, +}; + +static int __init init(void) +{ + if (ipt_register_match(&ipt_limit_reg)) + return -EINVAL; + return 0; +} + +static void __exit fini(void) +{ + ipt_unregister_match(&ipt_limit_reg); +} + +module_init(init); +module_exit(fini); |