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6#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
7
8#include <linux/slab.h>
9#include <linux/module.h>
10#include <linux/skbuff.h>
11#include <linux/interrupt.h>
12
13#include <linux/netfilter/x_tables.h>
14#include <linux/netfilter/xt_limit.h>
15
16struct xt_limit_priv {
17 unsigned long prev;
18 u32 credit;
19};
20
21MODULE_LICENSE("GPL");
22MODULE_AUTHOR("Herve Eychenne <rv@wallfire.org>");
23MODULE_DESCRIPTION("Xtables: rate-limit match");
24MODULE_ALIAS("ipt_limit");
25MODULE_ALIAS("ip6t_limit");
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47
48#define MAX_CPJ (0xFFFFFFFF / (HZ*60*60*24))
49
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51
52
53#define _POW2_BELOW2(x) ((x)|((x)>>1))
54#define _POW2_BELOW4(x) (_POW2_BELOW2(x)|_POW2_BELOW2((x)>>2))
55#define _POW2_BELOW8(x) (_POW2_BELOW4(x)|_POW2_BELOW4((x)>>4))
56#define _POW2_BELOW16(x) (_POW2_BELOW8(x)|_POW2_BELOW8((x)>>8))
57#define _POW2_BELOW32(x) (_POW2_BELOW16(x)|_POW2_BELOW16((x)>>16))
58#define POW2_BELOW32(x) ((_POW2_BELOW32(x)>>1) + 1)
59
60#define CREDITS_PER_JIFFY POW2_BELOW32(MAX_CPJ)
61
62static bool
63limit_mt(const struct sk_buff *skb, struct xt_action_param *par)
64{
65 const struct xt_rateinfo *r = par->matchinfo;
66 struct xt_limit_priv *priv = r->master;
67 unsigned long now;
68 u32 old_credit, new_credit, credit_increase = 0;
69 bool ret;
70
71
72 if ((READ_ONCE(priv->credit) < r->cost) && (READ_ONCE(priv->prev) == jiffies))
73 return false;
74
75 do {
76 now = jiffies;
77 credit_increase += (now - xchg(&priv->prev, now)) * CREDITS_PER_JIFFY;
78 old_credit = READ_ONCE(priv->credit);
79 new_credit = old_credit;
80 new_credit += credit_increase;
81 if (new_credit > r->credit_cap)
82 new_credit = r->credit_cap;
83 if (new_credit >= r->cost) {
84 ret = true;
85 new_credit -= r->cost;
86 } else {
87 ret = false;
88 }
89 } while (cmpxchg(&priv->credit, old_credit, new_credit) != old_credit);
90
91 return ret;
92}
93
94
95static u32 user2credits(u32 user)
96{
97
98 if (user > 0xFFFFFFFF / (HZ*CREDITS_PER_JIFFY))
99
100 return (user / XT_LIMIT_SCALE) * HZ * CREDITS_PER_JIFFY;
101
102 return (user * HZ * CREDITS_PER_JIFFY) / XT_LIMIT_SCALE;
103}
104
105static int limit_mt_check(const struct xt_mtchk_param *par)
106{
107 struct xt_rateinfo *r = par->matchinfo;
108 struct xt_limit_priv *priv;
109
110
111 if (r->burst == 0
112 || user2credits(r->avg * r->burst) < user2credits(r->avg)) {
113 pr_info_ratelimited("Overflow, try lower: %u/%u\n",
114 r->avg, r->burst);
115 return -ERANGE;
116 }
117
118 priv = kmalloc(sizeof(*priv), GFP_KERNEL);
119 if (priv == NULL)
120 return -ENOMEM;
121
122
123 r->master = priv;
124
125
126 priv->prev = jiffies;
127 priv->credit = user2credits(r->avg * r->burst);
128 if (r->cost == 0) {
129 r->credit_cap = priv->credit;
130 r->cost = user2credits(r->avg);
131 }
132
133 return 0;
134}
135
136static void limit_mt_destroy(const struct xt_mtdtor_param *par)
137{
138 const struct xt_rateinfo *info = par->matchinfo;
139
140 kfree(info->master);
141}
142
143#ifdef CONFIG_NETFILTER_XTABLES_COMPAT
144struct compat_xt_rateinfo {
145 u_int32_t avg;
146 u_int32_t burst;
147
148 compat_ulong_t prev;
149 u_int32_t credit;
150 u_int32_t credit_cap, cost;
151
152 u_int32_t master;
153};
154
155
156
157static void limit_mt_compat_from_user(void *dst, const void *src)
158{
159 const struct compat_xt_rateinfo *cm = src;
160 struct xt_rateinfo m = {
161 .avg = cm->avg,
162 .burst = cm->burst,
163 .prev = cm->prev | (unsigned long)cm->master << 32,
164 .credit = cm->credit,
165 .credit_cap = cm->credit_cap,
166 .cost = cm->cost,
167 };
168 memcpy(dst, &m, sizeof(m));
169}
170
171static int limit_mt_compat_to_user(void __user *dst, const void *src)
172{
173 const struct xt_rateinfo *m = src;
174 struct compat_xt_rateinfo cm = {
175 .avg = m->avg,
176 .burst = m->burst,
177 .prev = m->prev,
178 .credit = m->credit,
179 .credit_cap = m->credit_cap,
180 .cost = m->cost,
181 .master = m->prev >> 32,
182 };
183 return copy_to_user(dst, &cm, sizeof(cm)) ? -EFAULT : 0;
184}
185#endif
186
187static struct xt_match limit_mt_reg __read_mostly = {
188 .name = "limit",
189 .revision = 0,
190 .family = NFPROTO_UNSPEC,
191 .match = limit_mt,
192 .checkentry = limit_mt_check,
193 .destroy = limit_mt_destroy,
194 .matchsize = sizeof(struct xt_rateinfo),
195#ifdef CONFIG_NETFILTER_XTABLES_COMPAT
196 .compatsize = sizeof(struct compat_xt_rateinfo),
197 .compat_from_user = limit_mt_compat_from_user,
198 .compat_to_user = limit_mt_compat_to_user,
199#endif
200 .usersize = offsetof(struct xt_rateinfo, prev),
201 .me = THIS_MODULE,
202};
203
204static int __init limit_mt_init(void)
205{
206 return xt_register_match(&limit_mt_reg);
207}
208
209static void __exit limit_mt_exit(void)
210{
211 xt_unregister_match(&limit_mt_reg);
212}
213
214module_init(limit_mt_init);
215module_exit(limit_mt_exit);
216