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9#include <linux/module.h>
10#include <linux/skbuff.h>
11#include <linux/spinlock.h>
12#include <linux/interrupt.h>
13
14#include <linux/netfilter/x_tables.h>
15#include <linux/netfilter/xt_limit.h>
16
17struct xt_limit_priv {
18 unsigned long prev;
19 uint32_t credit;
20};
21
22MODULE_LICENSE("GPL");
23MODULE_AUTHOR("Herve Eychenne <rv@wallfire.org>");
24MODULE_DESCRIPTION("Xtables: rate-limit match");
25MODULE_ALIAS("ipt_limit");
26MODULE_ALIAS("ip6t_limit");
27
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29
30
31
32static DEFINE_SPINLOCK(limit_lock);
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50
51#define MAX_CPJ (0xFFFFFFFF / (HZ*60*60*24))
52
53
54
55
56#define _POW2_BELOW2(x) ((x)|((x)>>1))
57#define _POW2_BELOW4(x) (_POW2_BELOW2(x)|_POW2_BELOW2((x)>>2))
58#define _POW2_BELOW8(x) (_POW2_BELOW4(x)|_POW2_BELOW4((x)>>4))
59#define _POW2_BELOW16(x) (_POW2_BELOW8(x)|_POW2_BELOW8((x)>>8))
60#define _POW2_BELOW32(x) (_POW2_BELOW16(x)|_POW2_BELOW16((x)>>16))
61#define POW2_BELOW32(x) ((_POW2_BELOW32(x)>>1) + 1)
62
63#define CREDITS_PER_JIFFY POW2_BELOW32(MAX_CPJ)
64
65static bool
66limit_mt(const struct sk_buff *skb, const struct xt_match_param *par)
67{
68 const struct xt_rateinfo *r = par->matchinfo;
69 struct xt_limit_priv *priv = r->master;
70 unsigned long now = jiffies;
71
72 spin_lock_bh(&limit_lock);
73 priv->credit += (now - xchg(&priv->prev, now)) * CREDITS_PER_JIFFY;
74 if (priv->credit > r->credit_cap)
75 priv->credit = r->credit_cap;
76
77 if (priv->credit >= r->cost) {
78
79 priv->credit -= r->cost;
80 spin_unlock_bh(&limit_lock);
81 return true;
82 }
83
84 spin_unlock_bh(&limit_lock);
85 return false;
86}
87
88
89static u_int32_t
90user2credits(u_int32_t user)
91{
92
93 if (user > 0xFFFFFFFF / (HZ*CREDITS_PER_JIFFY))
94
95 return (user / XT_LIMIT_SCALE) * HZ * CREDITS_PER_JIFFY;
96
97 return (user * HZ * CREDITS_PER_JIFFY) / XT_LIMIT_SCALE;
98}
99
100static bool limit_mt_check(const struct xt_mtchk_param *par)
101{
102 struct xt_rateinfo *r = par->matchinfo;
103 struct xt_limit_priv *priv;
104
105
106 if (r->burst == 0
107 || user2credits(r->avg * r->burst) < user2credits(r->avg)) {
108 printk("Overflow in xt_limit, try lower: %u/%u\n",
109 r->avg, r->burst);
110 return false;
111 }
112
113 priv = kmalloc(sizeof(*priv), GFP_KERNEL);
114 if (priv == NULL)
115 return false;
116
117
118 r->master = priv;
119 if (r->cost == 0) {
120
121
122 priv->prev = jiffies;
123 priv->credit = user2credits(r->avg * r->burst);
124 r->credit_cap = user2credits(r->avg * r->burst);
125 r->cost = user2credits(r->avg);
126 }
127 return true;
128}
129
130static void limit_mt_destroy(const struct xt_mtdtor_param *par)
131{
132 const struct xt_rateinfo *info = par->matchinfo;
133
134 kfree(info->master);
135}
136
137#ifdef CONFIG_COMPAT
138struct compat_xt_rateinfo {
139 u_int32_t avg;
140 u_int32_t burst;
141
142 compat_ulong_t prev;
143 u_int32_t credit;
144 u_int32_t credit_cap, cost;
145
146 u_int32_t master;
147};
148
149
150
151static void limit_mt_compat_from_user(void *dst, void *src)
152{
153 const struct compat_xt_rateinfo *cm = src;
154 struct xt_rateinfo m = {
155 .avg = cm->avg,
156 .burst = cm->burst,
157 .prev = cm->prev | (unsigned long)cm->master << 32,
158 .credit = cm->credit,
159 .credit_cap = cm->credit_cap,
160 .cost = cm->cost,
161 };
162 memcpy(dst, &m, sizeof(m));
163}
164
165static int limit_mt_compat_to_user(void __user *dst, void *src)
166{
167 const struct xt_rateinfo *m = src;
168 struct compat_xt_rateinfo cm = {
169 .avg = m->avg,
170 .burst = m->burst,
171 .prev = m->prev,
172 .credit = m->credit,
173 .credit_cap = m->credit_cap,
174 .cost = m->cost,
175 .master = m->prev >> 32,
176 };
177 return copy_to_user(dst, &cm, sizeof(cm)) ? -EFAULT : 0;
178}
179#endif
180
181static struct xt_match limit_mt_reg __read_mostly = {
182 .name = "limit",
183 .revision = 0,
184 .family = NFPROTO_UNSPEC,
185 .match = limit_mt,
186 .checkentry = limit_mt_check,
187 .destroy = limit_mt_destroy,
188 .matchsize = sizeof(struct xt_rateinfo),
189#ifdef CONFIG_COMPAT
190 .compatsize = sizeof(struct compat_xt_rateinfo),
191 .compat_from_user = limit_mt_compat_from_user,
192 .compat_to_user = limit_mt_compat_to_user,
193#endif
194 .me = THIS_MODULE,
195};
196
197static int __init limit_mt_init(void)
198{
199 return xt_register_match(&limit_mt_reg);
200}
201
202static void __exit limit_mt_exit(void)
203{
204 xt_unregister_match(&limit_mt_reg);
205}
206
207module_init(limit_mt_init);
208module_exit(limit_mt_exit);
209