Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 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 | |
| 21 | static 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 | |
| 34 | static 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. */ |
| 58 | static u_int32_t |
| 59 | user2credits(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 | |
| 69 | static 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 | |
| 93 | static 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 | |
Andrew Morton | 65b4b4e | 2006-03-28 16:37:06 -0800 | [diff] [blame] | 101 | static int __init ebt_limit_init(void) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 102 | { |
| 103 | return ebt_register_match(&ebt_limit_reg); |
| 104 | } |
| 105 | |
Andrew Morton | 65b4b4e | 2006-03-28 16:37:06 -0800 | [diff] [blame] | 106 | static void __exit ebt_limit_fini(void) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 107 | { |
| 108 | ebt_unregister_match(&ebt_limit_reg); |
| 109 | } |
| 110 | |
Andrew Morton | 65b4b4e | 2006-03-28 16:37:06 -0800 | [diff] [blame] | 111 | module_init(ebt_limit_init); |
| 112 | module_exit(ebt_limit_fini); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 113 | MODULE_LICENSE("GPL"); |