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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
- *
- */
- #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
- #include <linux/module.h>
- #include <linux/netdevice.h>
- #include <linux/spinlock.h>
- #include <linux/netfilter/x_tables.h>
- #include <linux/netfilter_bridge/ebtables.h>
- #include <linux/netfilter_bridge/ebt_limit.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 bool
- ebt_limit_mt(const struct sk_buff *skb, struct xt_action_param *par)
- {
- struct ebt_limit_info *info = (void *)par->matchinfo;
- 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 true;
- }
- spin_unlock_bh(&limit_lock);
- return false;
- }
- /* 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_mt_check(const struct xt_mtchk_param *par)
- {
- struct ebt_limit_info *info = par->matchinfo;
- /* Check for overflow. */
- if (info->burst == 0 ||
- user2credits(info->avg * info->burst) < user2credits(info->avg)) {
- pr_info("overflow, 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;
- }
- #ifdef CONFIG_COMPAT
- /*
- * no conversion function needed --
- * only avg/burst have meaningful values in userspace.
- */
- struct ebt_compat_limit_info {
- compat_uint_t avg, burst;
- compat_ulong_t prev;
- compat_uint_t credit, credit_cap, cost;
- };
- #endif
- static struct xt_match ebt_limit_mt_reg __read_mostly = {
- .name = "limit",
- .revision = 0,
- .family = NFPROTO_BRIDGE,
- .match = ebt_limit_mt,
- .checkentry = ebt_limit_mt_check,
- .matchsize = sizeof(struct ebt_limit_info),
- #ifdef CONFIG_COMPAT
- .compatsize = sizeof(struct ebt_compat_limit_info),
- #endif
- .me = THIS_MODULE,
- };
- static int __init ebt_limit_init(void)
- {
- return xt_register_match(&ebt_limit_mt_reg);
- }
- static void __exit ebt_limit_fini(void)
- {
- xt_unregister_match(&ebt_limit_mt_reg);
- }
- module_init(ebt_limit_init);
- module_exit(ebt_limit_fini);
- MODULE_DESCRIPTION("Ebtables: Rate-limit match");
- MODULE_LICENSE("GPL");
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