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 xt_match_param
*par
)
36 struct ebt_limit_info
*info
= (void *)par
->matchinfo
;
37 unsigned long now
= jiffies
;
39 spin_lock_bh(&limit_lock
);
40 info
->credit
+= (now
- xchg(&info
->prev
, now
)) * CREDITS_PER_JIFFY
;
41 if (info
->credit
> info
->credit_cap
)
42 info
->credit
= info
->credit_cap
;
44 if (info
->credit
>= info
->cost
) {
45 /* We're not limited. */
46 info
->credit
-= info
->cost
;
47 spin_unlock_bh(&limit_lock
);
51 spin_unlock_bh(&limit_lock
);
55 /* Precision saver. */
57 user2credits(u_int32_t user
)
59 /* If multiplying would overflow... */
60 if (user
> 0xFFFFFFFF / (HZ
*CREDITS_PER_JIFFY
))
62 return (user
/ EBT_LIMIT_SCALE
) * HZ
* CREDITS_PER_JIFFY
;
64 return (user
* HZ
* CREDITS_PER_JIFFY
) / EBT_LIMIT_SCALE
;
68 ebt_limit_mt_check(const char *table
, const void *e
,
69 const struct xt_match
*match
, void *data
,
70 unsigned int hook_mask
)
72 struct ebt_limit_info
*info
= data
;
74 /* Check for overflow. */
75 if (info
->burst
== 0 ||
76 user2credits(info
->avg
* info
->burst
) < user2credits(info
->avg
)) {
77 printk("Overflow in ebt_limit, try lower: %u/%u\n",
78 info
->avg
, info
->burst
);
82 /* User avg in seconds * EBT_LIMIT_SCALE: convert to jiffies * 128. */
84 info
->credit
= user2credits(info
->avg
* info
->burst
);
85 info
->credit_cap
= user2credits(info
->avg
* info
->burst
);
86 info
->cost
= user2credits(info
->avg
);
90 static struct xt_match ebt_limit_mt_reg __read_mostly
= {
93 .family
= NFPROTO_BRIDGE
,
94 .match
= ebt_limit_mt
,
95 .checkentry
= ebt_limit_mt_check
,
96 .matchsize
= XT_ALIGN(sizeof(struct ebt_limit_info
)),
100 static int __init
ebt_limit_init(void)
102 return xt_register_match(&ebt_limit_mt_reg
);
105 static void __exit
ebt_limit_fini(void)
107 xt_unregister_match(&ebt_limit_mt_reg
);
110 module_init(ebt_limit_init
);
111 module_exit(ebt_limit_fini
);
112 MODULE_DESCRIPTION("Ebtables: Rate-limit match");
113 MODULE_LICENSE("GPL");