5 * Tom Marshall <tommy@home.tig-grr.com>
7 * Mostly copied from netfilter's ipt_limit.c, see that file for
13 #include <linux/module.h>
14 #include <linux/netdevice.h>
15 #include <linux/spinlock.h>
16 #include <linux/netfilter/x_tables.h>
17 #include <linux/netfilter_bridge/ebtables.h>
18 #include <linux/netfilter_bridge/ebt_limit.h>
20 static DEFINE_SPINLOCK(limit_lock);
22 #define MAX_CPJ (0xFFFFFFFF / (HZ*60*60*24))
24 #define _POW2_BELOW2(x) ((x)|((x)>>1))
25 #define _POW2_BELOW4(x) (_POW2_BELOW2(x)|_POW2_BELOW2((x)>>2))
26 #define _POW2_BELOW8(x) (_POW2_BELOW4(x)|_POW2_BELOW4((x)>>4))
27 #define _POW2_BELOW16(x) (_POW2_BELOW8(x)|_POW2_BELOW8((x)>>8))
28 #define _POW2_BELOW32(x) (_POW2_BELOW16(x)|_POW2_BELOW16((x)>>16))
29 #define POW2_BELOW32(x) ((_POW2_BELOW32(x)>>1) + 1)
31 #define CREDITS_PER_JIFFY POW2_BELOW32(MAX_CPJ)
34 ebt_limit_mt(const struct sk_buff *skb, const struct net_device *in,
35 const struct net_device *out, const struct xt_match *match,
36 const void *data, int offset, unsigned int protoff, bool *hotdrop)
38 struct ebt_limit_info *info = (struct ebt_limit_info *)data;
39 unsigned long now = jiffies;
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;
46 if (info->credit >= info->cost) {
47 /* We're not limited. */
48 info->credit -= info->cost;
49 spin_unlock_bh(&limit_lock);
53 spin_unlock_bh(&limit_lock);
57 /* Precision saver. */
59 user2credits(u_int32_t user)
61 /* If multiplying would overflow... */
62 if (user > 0xFFFFFFFF / (HZ*CREDITS_PER_JIFFY))
64 return (user / EBT_LIMIT_SCALE) * HZ * CREDITS_PER_JIFFY;
66 return (user * HZ * CREDITS_PER_JIFFY) / EBT_LIMIT_SCALE;
70 ebt_limit_mt_check(const char *table, const void *e,
71 const struct xt_match *match, void *data,
72 unsigned int hook_mask)
74 struct ebt_limit_info *info = data;
76 /* Check for overflow. */
77 if (info->burst == 0 ||
78 user2credits(info->avg * info->burst) < user2credits(info->avg)) {
79 printk("Overflow in ebt_limit, try lower: %u/%u\n",
80 info->avg, info->burst);
84 /* User avg in seconds * EBT_LIMIT_SCALE: convert to jiffies * 128. */
86 info->credit = user2credits(info->avg * info->burst);
87 info->credit_cap = user2credits(info->avg * info->burst);
88 info->cost = user2credits(info->avg);
92 static struct ebt_match ebt_limit_reg __read_mostly = {
93 .name = EBT_LIMIT_MATCH,
95 .family = NFPROTO_BRIDGE,
96 .match = ebt_limit_mt,
97 .checkentry = ebt_limit_mt_check,
98 .matchsize = XT_ALIGN(sizeof(struct ebt_limit_info)),
102 static int __init ebt_limit_init(void)
104 return ebt_register_match(&ebt_limit_reg);
107 static void __exit ebt_limit_fini(void)
109 ebt_unregister_match(&ebt_limit_reg);
112 module_init(ebt_limit_init);
113 module_exit(ebt_limit_fini);
114 MODULE_DESCRIPTION("Ebtables: Rate-limit match");
115 MODULE_LICENSE("GPL");