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)
33 static bool ebt_limit_match(const struct sk_buff
*skb
,
34 const struct net_device
*in
, const struct net_device
*out
,
35 const void *data
, unsigned int datalen
)
37 struct ebt_limit_info
*info
= (struct ebt_limit_info
*)data
;
38 unsigned long now
= jiffies
;
40 spin_lock_bh(&limit_lock
);
41 info
->credit
+= (now
- xchg(&info
->prev
, now
)) * CREDITS_PER_JIFFY
;
42 if (info
->credit
> info
->credit_cap
)
43 info
->credit
= info
->credit_cap
;
45 if (info
->credit
>= info
->cost
) {
46 /* We're not limited. */
47 info
->credit
-= info
->cost
;
48 spin_unlock_bh(&limit_lock
);
52 spin_unlock_bh(&limit_lock
);
56 /* Precision saver. */
58 user2credits(u_int32_t user
)
60 /* If multiplying would overflow... */
61 if (user
> 0xFFFFFFFF / (HZ
*CREDITS_PER_JIFFY
))
63 return (user
/ EBT_LIMIT_SCALE
) * HZ
* CREDITS_PER_JIFFY
;
65 return (user
* HZ
* CREDITS_PER_JIFFY
) / EBT_LIMIT_SCALE
;
68 static bool ebt_limit_check(const char *tablename
, unsigned int hookmask
,
69 const struct ebt_entry
*e
, void *data
, unsigned int datalen
)
71 struct ebt_limit_info
*info
= data
;
73 /* Check for overflow. */
74 if (info
->burst
== 0 ||
75 user2credits(info
->avg
* info
->burst
) < user2credits(info
->avg
)) {
76 printk("Overflow in ebt_limit, try lower: %u/%u\n",
77 info
->avg
, info
->burst
);
81 /* User avg in seconds * EBT_LIMIT_SCALE: convert to jiffies * 128. */
83 info
->credit
= user2credits(info
->avg
* info
->burst
);
84 info
->credit_cap
= user2credits(info
->avg
* info
->burst
);
85 info
->cost
= user2credits(info
->avg
);
89 static struct ebt_match ebt_limit_reg __read_mostly
= {
90 .name
= EBT_LIMIT_MATCH
,
91 .match
= ebt_limit_match
,
92 .check
= ebt_limit_check
,
93 .matchsize
= XT_ALIGN(sizeof(struct ebt_limit_info
)),
97 static int __init
ebt_limit_init(void)
99 return ebt_register_match(&ebt_limit_reg
);
102 static void __exit
ebt_limit_fini(void)
104 ebt_unregister_match(&ebt_limit_reg
);
107 module_init(ebt_limit_init
);
108 module_exit(ebt_limit_fini
);
109 MODULE_DESCRIPTION("Ebtables: Rate-limit match");
110 MODULE_LICENSE("GPL");