| /* |
| * 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, const struct xt_match_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 false; |
| } |
| |
| /* 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 true; |
| } |
| |
| |
| #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"); |