Loading...
1// SPDX-License-Identifier: GPL-2.0-only
2/* (C) 1999 Jérôme de Vivie <devivie@info.enserb.u-bordeaux.fr>
3 * (C) 1999 Hervé Eychenne <eychenne@info.enserb.u-bordeaux.fr>
4 * (C) 2006-2012 Patrick McHardy <kaber@trash.net>
5 */
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");
26
27/* The algorithm used is the Simple Token Bucket Filter (TBF)
28 * see net/sched/sch_tbf.c in the linux source tree
29 */
30
31/* Rusty: This is my (non-mathematically-inclined) understanding of
32 this algorithm. The `average rate' in jiffies becomes your initial
33 amount of credit `credit' and the most credit you can ever have
34 `credit_cap'. The `peak rate' becomes the cost of passing the
35 test, `cost'.
36
37 `prev' tracks the last packet hit: you gain one credit per jiffy.
38 If you get credit balance more than this, the extra credit is
39 discarded. Every time the match passes, you lose `cost' credits;
40 if you don't have that many, the test fails.
41
42 See Alexey's formal explanation in net/sched/sch_tbf.c.
43
44 To get the maximum range, we multiply by this factor (ie. you get N
45 credits per jiffy). We want to allow a rate as low as 1 per day
46 (slowest userspace tool allows), which means
47 CREDITS_PER_JIFFY*HZ*60*60*24 < 2^32. ie. */
48#define MAX_CPJ (0xFFFFFFFF / (HZ*60*60*24))
49
50/* Repeated shift and or gives us all 1s, final shift and add 1 gives
51 * us the power of 2 below the theoretical max, so GCC simply does a
52 * shift. */
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 /* fastpath if there is nothing to update */
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/* Precision saver. */
95static u32 user2credits(u32 user)
96{
97 /* If multiplying would overflow... */
98 if (user > 0xFFFFFFFF / (HZ*CREDITS_PER_JIFFY))
99 /* Divide first. */
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 /* Check for overflow. */
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 /* For SMP, we only want to use one set of state. */
123 r->master = priv;
124 /* User avg in seconds * XT_LIMIT_SCALE: convert to jiffies *
125 128. */
126 priv->prev = jiffies;
127 priv->credit = user2credits(r->avg * r->burst); /* Credits full. */
128 if (r->cost == 0) {
129 r->credit_cap = priv->credit; /* Credits full. */
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/* To keep the full "prev" timestamp, the upper 32 bits are stored in the
156 * master pointer, which does not need to be preserved. */
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 /* CONFIG_NETFILTER_XTABLES_COMPAT */
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);
1/* (C) 1999 Jérôme de Vivie <devivie@info.enserb.u-bordeaux.fr>
2 * (C) 1999 Hervé Eychenne <eychenne@info.enserb.u-bordeaux.fr>
3 * (C) 2006-2012 Patrick McHardy <kaber@trash.net>
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License version 2 as
7 * published by the Free Software Foundation.
8 */
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 unsigned long prev;
22 uint32_t credit;
23};
24
25MODULE_LICENSE("GPL");
26MODULE_AUTHOR("Herve Eychenne <rv@wallfire.org>");
27MODULE_DESCRIPTION("Xtables: rate-limit match");
28MODULE_ALIAS("ipt_limit");
29MODULE_ALIAS("ip6t_limit");
30
31/* The algorithm used is the Simple Token Bucket Filter (TBF)
32 * see net/sched/sch_tbf.c in the linux source tree
33 */
34
35static DEFINE_SPINLOCK(limit_lock);
36
37/* Rusty: This is my (non-mathematically-inclined) understanding of
38 this algorithm. The `average rate' in jiffies becomes your initial
39 amount of credit `credit' and the most credit you can ever have
40 `credit_cap'. The `peak rate' becomes the cost of passing the
41 test, `cost'.
42
43 `prev' tracks the last packet hit: you gain one credit per jiffy.
44 If you get credit balance more than this, the extra credit is
45 discarded. Every time the match passes, you lose `cost' credits;
46 if you don't have that many, the test fails.
47
48 See Alexey's formal explanation in net/sched/sch_tbf.c.
49
50 To get the maxmum range, we multiply by this factor (ie. you get N
51 credits per jiffy). We want to allow a rate as low as 1 per day
52 (slowest userspace tool allows), which means
53 CREDITS_PER_JIFFY*HZ*60*60*24 < 2^32. ie. */
54#define MAX_CPJ (0xFFFFFFFF / (HZ*60*60*24))
55
56/* Repeated shift and or gives us all 1s, final shift and add 1 gives
57 * us the power of 2 below the theoretical max, so GCC simply does a
58 * shift. */
59#define _POW2_BELOW2(x) ((x)|((x)>>1))
60#define _POW2_BELOW4(x) (_POW2_BELOW2(x)|_POW2_BELOW2((x)>>2))
61#define _POW2_BELOW8(x) (_POW2_BELOW4(x)|_POW2_BELOW4((x)>>4))
62#define _POW2_BELOW16(x) (_POW2_BELOW8(x)|_POW2_BELOW8((x)>>8))
63#define _POW2_BELOW32(x) (_POW2_BELOW16(x)|_POW2_BELOW16((x)>>16))
64#define POW2_BELOW32(x) ((_POW2_BELOW32(x)>>1) + 1)
65
66#define CREDITS_PER_JIFFY POW2_BELOW32(MAX_CPJ)
67
68static bool
69limit_mt(const struct sk_buff *skb, struct xt_action_param *par)
70{
71 const struct xt_rateinfo *r = par->matchinfo;
72 struct xt_limit_priv *priv = r->master;
73 unsigned long now = jiffies;
74
75 spin_lock_bh(&limit_lock);
76 priv->credit += (now - xchg(&priv->prev, now)) * CREDITS_PER_JIFFY;
77 if (priv->credit > r->credit_cap)
78 priv->credit = r->credit_cap;
79
80 if (priv->credit >= r->cost) {
81 /* We're not limited. */
82 priv->credit -= r->cost;
83 spin_unlock_bh(&limit_lock);
84 return true;
85 }
86
87 spin_unlock_bh(&limit_lock);
88 return false;
89}
90
91/* Precision saver. */
92static u32 user2credits(u32 user)
93{
94 /* If multiplying would overflow... */
95 if (user > 0xFFFFFFFF / (HZ*CREDITS_PER_JIFFY))
96 /* Divide first. */
97 return (user / XT_LIMIT_SCALE) * HZ * CREDITS_PER_JIFFY;
98
99 return (user * HZ * CREDITS_PER_JIFFY) / XT_LIMIT_SCALE;
100}
101
102static int limit_mt_check(const struct xt_mtchk_param *par)
103{
104 struct xt_rateinfo *r = par->matchinfo;
105 struct xt_limit_priv *priv;
106
107 /* Check for overflow. */
108 if (r->burst == 0
109 || user2credits(r->avg * r->burst) < user2credits(r->avg)) {
110 pr_info("Overflow, try lower: %u/%u\n",
111 r->avg, r->burst);
112 return -ERANGE;
113 }
114
115 priv = kmalloc(sizeof(*priv), GFP_KERNEL);
116 if (priv == NULL)
117 return -ENOMEM;
118
119 /* For SMP, we only want to use one set of state. */
120 r->master = priv;
121 /* User avg in seconds * XT_LIMIT_SCALE: convert to jiffies *
122 128. */
123 priv->prev = jiffies;
124 priv->credit = user2credits(r->avg * r->burst); /* Credits full. */
125 if (r->cost == 0) {
126 r->credit_cap = priv->credit; /* Credits full. */
127 r->cost = user2credits(r->avg);
128 }
129 return 0;
130}
131
132static void limit_mt_destroy(const struct xt_mtdtor_param *par)
133{
134 const struct xt_rateinfo *info = par->matchinfo;
135
136 kfree(info->master);
137}
138
139#ifdef CONFIG_COMPAT
140struct compat_xt_rateinfo {
141 u_int32_t avg;
142 u_int32_t burst;
143
144 compat_ulong_t prev;
145 u_int32_t credit;
146 u_int32_t credit_cap, cost;
147
148 u_int32_t master;
149};
150
151/* To keep the full "prev" timestamp, the upper 32 bits are stored in the
152 * master pointer, which does not need to be preserved. */
153static void limit_mt_compat_from_user(void *dst, const void *src)
154{
155 const struct compat_xt_rateinfo *cm = src;
156 struct xt_rateinfo m = {
157 .avg = cm->avg,
158 .burst = cm->burst,
159 .prev = cm->prev | (unsigned long)cm->master << 32,
160 .credit = cm->credit,
161 .credit_cap = cm->credit_cap,
162 .cost = cm->cost,
163 };
164 memcpy(dst, &m, sizeof(m));
165}
166
167static int limit_mt_compat_to_user(void __user *dst, const void *src)
168{
169 const struct xt_rateinfo *m = src;
170 struct compat_xt_rateinfo cm = {
171 .avg = m->avg,
172 .burst = m->burst,
173 .prev = m->prev,
174 .credit = m->credit,
175 .credit_cap = m->credit_cap,
176 .cost = m->cost,
177 .master = m->prev >> 32,
178 };
179 return copy_to_user(dst, &cm, sizeof(cm)) ? -EFAULT : 0;
180}
181#endif /* CONFIG_COMPAT */
182
183static struct xt_match limit_mt_reg __read_mostly = {
184 .name = "limit",
185 .revision = 0,
186 .family = NFPROTO_UNSPEC,
187 .match = limit_mt,
188 .checkentry = limit_mt_check,
189 .destroy = limit_mt_destroy,
190 .matchsize = sizeof(struct xt_rateinfo),
191#ifdef CONFIG_COMPAT
192 .compatsize = sizeof(struct compat_xt_rateinfo),
193 .compat_from_user = limit_mt_compat_from_user,
194 .compat_to_user = limit_mt_compat_to_user,
195#endif
196 .me = THIS_MODULE,
197};
198
199static int __init limit_mt_init(void)
200{
201 return xt_register_match(&limit_mt_reg);
202}
203
204static void __exit limit_mt_exit(void)
205{
206 xt_unregister_match(&limit_mt_reg);
207}
208
209module_init(limit_mt_init);
210module_exit(limit_mt_exit);