1/* 2 * ebt_limit 3 * 4 * Authors: 5 * Tom Marshall <tommy@home.tig-grr.com> 6 * 7 * Mostly copied from netfilter's ipt_limit.c, see that file for 8 * more explanation 9 * 10 * September, 2003 11 * 12 */ 13 14#include <linux/netfilter_bridge/ebtables.h> 15#include <linux/netfilter_bridge/ebt_limit.h> 16#include <linux/module.h> 17 18#include <linux/netdevice.h> 19#include <linux/spinlock.h> 20 21static DEFINE_SPINLOCK(limit_lock); 22 23#define MAX_CPJ (0xFFFFFFFF / (HZ*60*60*24)) 24 25#define _POW2_BELOW2(x) ((x)|((x)>>1)) 26#define _POW2_BELOW4(x) (_POW2_BELOW2(x)|_POW2_BELOW2((x)>>2)) 27#define _POW2_BELOW8(x) (_POW2_BELOW4(x)|_POW2_BELOW4((x)>>4)) 28#define _POW2_BELOW16(x) (_POW2_BELOW8(x)|_POW2_BELOW8((x)>>8)) 29#define _POW2_BELOW32(x) (_POW2_BELOW16(x)|_POW2_BELOW16((x)>>16)) 30#define POW2_BELOW32(x) ((_POW2_BELOW32(x)>>1) + 1) 31 32#define CREDITS_PER_JIFFY POW2_BELOW32(MAX_CPJ) 33 34static int ebt_limit_match(const struct sk_buff *skb, 35 const struct net_device *in, const struct net_device *out, 36 const void *data, unsigned int datalen) 37{ 38 struct ebt_limit_info *info = (struct ebt_limit_info *)data; 39 unsigned long now = jiffies; 40 41 spin_lock_bh(&limit_lock); 42 info->credit += (now - xchg(&info->prev, now)) * CREDITS_PER_JIFFY; 43 if (info->credit > info->credit_cap) 44 info->credit = info->credit_cap; 45 46 if (info->credit >= info->cost) { 47 /* We're not limited. */ 48 info->credit -= info->cost; 49 spin_unlock_bh(&limit_lock); 50 return EBT_MATCH; 51 } 52 53 spin_unlock_bh(&limit_lock); 54 return EBT_NOMATCH; 55} 56 57/* Precision saver. */ 58static u_int32_t 59user2credits(u_int32_t user) 60{ 61 /* If multiplying would overflow... */ 62 if (user > 0xFFFFFFFF / (HZ*CREDITS_PER_JIFFY)) 63 /* Divide first. */ 64 return (user / EBT_LIMIT_SCALE) * HZ * CREDITS_PER_JIFFY; 65 66 return (user * HZ * CREDITS_PER_JIFFY) / EBT_LIMIT_SCALE; 67} 68 69static int ebt_limit_check(const char *tablename, unsigned int hookmask, 70 const struct ebt_entry *e, void *data, unsigned int datalen) 71{ 72 struct ebt_limit_info *info = (struct ebt_limit_info *)data; 73 74 if (datalen != EBT_ALIGN(sizeof(struct ebt_limit_info))) 75 return -EINVAL; 76 77 /* Check for overflow. */ 78 if (info->burst == 0 || 79 user2credits(info->avg * info->burst) < user2credits(info->avg)) { 80 printk("Overflow in ebt_limit, try lower: %u/%u\n", 81 info->avg, info->burst); 82 return -EINVAL; 83 } 84 85 /* User avg in seconds * EBT_LIMIT_SCALE: convert to jiffies * 128. */ 86 info->prev = jiffies; 87 info->credit = user2credits(info->avg * info->burst); 88 info->credit_cap = user2credits(info->avg * info->burst); 89 info->cost = user2credits(info->avg); 90 return 0; 91} 92 93static struct ebt_match ebt_limit_reg = 94{ 95 .name = EBT_LIMIT_MATCH, 96 .match = ebt_limit_match, 97 .check = ebt_limit_check, 98 .me = THIS_MODULE, 99}; 100 101static int __init ebt_limit_init(void) 102{ 103 return ebt_register_match(&ebt_limit_reg); 104} 105 106static void __exit ebt_limit_fini(void) 107{ 108 ebt_unregister_match(&ebt_limit_reg); 109} 110 111module_init(ebt_limit_init); 112module_exit(ebt_limit_fini); 113MODULE_LICENSE("GPL"); 114