1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
|
/*
* ebt_limit
*
* Authors:
* Tom Marshall <tommy@home.tig-grr.com>
*
* Mostly copied from netfilter's ipt_limit.c, see that file for
* more explanation
*
* September, 2003
*
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/netdevice.h>
#include <linux/spinlock.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter_bridge/ebtables.h>
#include <linux/netfilter_bridge/ebt_limit.h>
static DEFINE_SPINLOCK(limit_lock);
#define MAX_CPJ (0xFFFFFFFF / (HZ*60*60*24))
#define _POW2_BELOW2(x) ((x)|((x)>>1))
#define _POW2_BELOW4(x) (_POW2_BELOW2(x)|_POW2_BELOW2((x)>>2))
#define _POW2_BELOW8(x) (_POW2_BELOW4(x)|_POW2_BELOW4((x)>>4))
#define _POW2_BELOW16(x) (_POW2_BELOW8(x)|_POW2_BELOW8((x)>>8))
#define _POW2_BELOW32(x) (_POW2_BELOW16(x)|_POW2_BELOW16((x)>>16))
#define POW2_BELOW32(x) ((_POW2_BELOW32(x)>>1) + 1)
#define CREDITS_PER_JIFFY POW2_BELOW32(MAX_CPJ)
static bool
ebt_limit_mt(const struct sk_buff *skb, struct xt_action_param *par)
{
struct ebt_limit_info *info = (void *)par->matchinfo;
unsigned long now = jiffies;
spin_lock_bh(&limit_lock);
info->credit += (now - xchg(&info->prev, now)) * CREDITS_PER_JIFFY;
if (info->credit > info->credit_cap)
info->credit = info->credit_cap;
if (info->credit >= info->cost) {
/* We're not limited. */
info->credit -= info->cost;
spin_unlock_bh(&limit_lock);
return true;
}
spin_unlock_bh(&limit_lock);
return false;
}
/* Precision saver. */
static u_int32_t
user2credits(u_int32_t user)
{
/* If multiplying would overflow... */
if (user > 0xFFFFFFFF / (HZ*CREDITS_PER_JIFFY))
/* Divide first. */
return (user / EBT_LIMIT_SCALE) * HZ * CREDITS_PER_JIFFY;
return (user * HZ * CREDITS_PER_JIFFY) / EBT_LIMIT_SCALE;
}
static int ebt_limit_mt_check(const struct xt_mtchk_param *par)
{
struct ebt_limit_info *info = par->matchinfo;
/* Check for overflow. */
if (info->burst == 0 ||
user2credits(info->avg * info->burst) < user2credits(info->avg)) {
pr_info("overflow, try lower: %u/%u\n",
info->avg, info->burst);
return -EINVAL;
}
/* User avg in seconds * EBT_LIMIT_SCALE: convert to jiffies * 128. */
info->prev = jiffies;
info->credit = user2credits(info->avg * info->burst);
info->credit_cap = user2credits(info->avg * info->burst);
info->cost = user2credits(info->avg);
return 0;
}
#ifdef CONFIG_COMPAT
/*
* no conversion function needed --
* only avg/burst have meaningful values in userspace.
*/
struct ebt_compat_limit_info {
compat_uint_t avg, burst;
compat_ulong_t prev;
compat_uint_t credit, credit_cap, cost;
};
#endif
static struct xt_match ebt_limit_mt_reg __read_mostly = {
.name = "limit",
.revision = 0,
.family = NFPROTO_BRIDGE,
.match = ebt_limit_mt,
.checkentry = ebt_limit_mt_check,
.matchsize = sizeof(struct ebt_limit_info),
#ifdef CONFIG_COMPAT
.compatsize = sizeof(struct ebt_compat_limit_info),
#endif
.me = THIS_MODULE,
};
static int __init ebt_limit_init(void)
{
return xt_register_match(&ebt_limit_mt_reg);
}
static void __exit ebt_limit_fini(void)
{
xt_unregister_match(&ebt_limit_mt_reg);
}
module_init(ebt_limit_init);
module_exit(ebt_limit_fini);
MODULE_DESCRIPTION("Ebtables: Rate-limit match");
MODULE_LICENSE("GPL");
|
