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9#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
10
11#include <linux/slab.h>
12#include <linux/module.h>
13#include <linux/skbuff.h>
14#include <linux/spinlock.h>
15#include <linux/interrupt.h>
16
17#include <linux/netfilter/x_tables.h>
18#include <linux/netfilter/xt_limit.h>
19
20struct xt_limit_priv {
21 spinlock_t lock;
22 unsigned long prev;
23 uint32_t credit;
24};
25
26MODULE_LICENSE("GPL");
27MODULE_AUTHOR("Herve Eychenne <rv@wallfire.org>");
28MODULE_DESCRIPTION("Xtables: rate-limit match");
29MODULE_ALIAS("ipt_limit");
30MODULE_ALIAS("ip6t_limit");
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52
53#define MAX_CPJ (0xFFFFFFFF / (HZ*60*60*24))
54
55
56
57
58#define _POW2_BELOW2(x) ((x)|((x)>>1))
59#define _POW2_BELOW4(x) (_POW2_BELOW2(x)|_POW2_BELOW2((x)>>2))
60#define _POW2_BELOW8(x) (_POW2_BELOW4(x)|_POW2_BELOW4((x)>>4))
61#define _POW2_BELOW16(x) (_POW2_BELOW8(x)|_POW2_BELOW8((x)>>8))
62#define _POW2_BELOW32(x) (_POW2_BELOW16(x)|_POW2_BELOW16((x)>>16))
63#define POW2_BELOW32(x) ((_POW2_BELOW32(x)>>1) + 1)
64
65#define CREDITS_PER_JIFFY POW2_BELOW32(MAX_CPJ)
66
67static bool
68limit_mt(const struct sk_buff *skb, struct xt_action_param *par)
69{
70 const struct xt_rateinfo *r = par->matchinfo;
71 struct xt_limit_priv *priv = r->master;
72 unsigned long now = jiffies;
73
74 spin_lock_bh(&priv->lock);
75 priv->credit += (now - xchg(&priv->prev, now)) * CREDITS_PER_JIFFY;
76 if (priv->credit > r->credit_cap)
77 priv->credit = r->credit_cap;
78
79 if (priv->credit >= r->cost) {
80
81 priv->credit -= r->cost;
82 spin_unlock_bh(&priv->lock);
83 return true;
84 }
85
86 spin_unlock_bh(&priv->lock);
87 return false;
88}
89
90
91static u32 user2credits(u32 user)
92{
93
94 if (user > 0xFFFFFFFF / (HZ*CREDITS_PER_JIFFY))
95
96 return (user / XT_LIMIT_SCALE) * HZ * CREDITS_PER_JIFFY;
97
98 return (user * HZ * CREDITS_PER_JIFFY) / XT_LIMIT_SCALE;
99}
100
101static int limit_mt_check(const struct xt_mtchk_param *par)
102{
103 struct xt_rateinfo *r = par->matchinfo;
104 struct xt_limit_priv *priv;
105
106
107 if (r->burst == 0
108 || user2credits(r->avg * r->burst) < user2credits(r->avg)) {
109 pr_info("Overflow, try lower: %u/%u\n",
110 r->avg, r->burst);
111 return -ERANGE;
112 }
113
114 priv = kmalloc(sizeof(*priv), GFP_KERNEL);
115 if (priv == NULL)
116 return -ENOMEM;
117
118
119 r->master = priv;
120
121
122 priv->prev = jiffies;
123 priv->credit = user2credits(r->avg * r->burst);
124 if (r->cost == 0) {
125 r->credit_cap = priv->credit;
126 r->cost = user2credits(r->avg);
127 }
128 spin_lock_init(&priv->lock);
129
130 return 0;
131}
132
133static void limit_mt_destroy(const struct xt_mtdtor_param *par)
134{
135 const struct xt_rateinfo *info = par->matchinfo;
136
137 kfree(info->master);
138}
139
140#ifdef CONFIG_COMPAT
141struct compat_xt_rateinfo {
142 u_int32_t avg;
143 u_int32_t burst;
144
145 compat_ulong_t prev;
146 u_int32_t credit;
147 u_int32_t credit_cap, cost;
148
149 u_int32_t master;
150};
151
152
153
154static void limit_mt_compat_from_user(void *dst, const void *src)
155{
156 const struct compat_xt_rateinfo *cm = src;
157 struct xt_rateinfo m = {
158 .avg = cm->avg,
159 .burst = cm->burst,
160 .prev = cm->prev | (unsigned long)cm->master << 32,
161 .credit = cm->credit,
162 .credit_cap = cm->credit_cap,
163 .cost = cm->cost,
164 };
165 memcpy(dst, &m, sizeof(m));
166}
167
168static int limit_mt_compat_to_user(void __user *dst, const void *src)
169{
170 const struct xt_rateinfo *m = src;
171 struct compat_xt_rateinfo cm = {
172 .avg = m->avg,
173 .burst = m->burst,
174 .prev = m->prev,
175 .credit = m->credit,
176 .credit_cap = m->credit_cap,
177 .cost = m->cost,
178 .master = m->prev >> 32,
179 };
180 return copy_to_user(dst, &cm, sizeof(cm)) ? -EFAULT : 0;
181}
182#endif
183
184static struct xt_match limit_mt_reg __read_mostly = {
185 .name = "limit",
186 .revision = 0,
187 .family = NFPROTO_UNSPEC,
188 .match = limit_mt,
189 .checkentry = limit_mt_check,
190 .destroy = limit_mt_destroy,
191 .matchsize = sizeof(struct xt_rateinfo),
192#ifdef CONFIG_COMPAT
193 .compatsize = sizeof(struct compat_xt_rateinfo),
194 .compat_from_user = limit_mt_compat_from_user,
195 .compat_to_user = limit_mt_compat_to_user,
196#else
197 .usersize = offsetof(struct xt_rateinfo, prev),
198#endif
199 .me = THIS_MODULE,
200};
201
202static int __init limit_mt_init(void)
203{
204 return xt_register_match(&limit_mt_reg);
205}
206
207static void __exit limit_mt_exit(void)
208{
209 xt_unregister_match(&limit_mt_reg);
210}
211
212module_init(limit_mt_init);
213module_exit(limit_mt_exit);
214