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db955170 MG |
1 | /* (C) 1999 Jérôme de Vivie <devivie@info.enserb.u-bordeaux.fr> |
2 | * (C) 1999 Hervé Eychenne <eychenne@info.enserb.u-bordeaux.fr> | |
1da177e4 LT |
3 | * |
4 | * This program is free software; you can redistribute it and/or modify | |
5 | * it under the terms of the GNU General Public License version 2 as | |
6 | * published by the Free Software Foundation. | |
7 | */ | |
8 | ||
9 | #include <linux/module.h> | |
10 | #include <linux/skbuff.h> | |
11 | #include <linux/spinlock.h> | |
12 | #include <linux/interrupt.h> | |
13 | ||
2e4e6a17 HW |
14 | #include <linux/netfilter/x_tables.h> |
15 | #include <linux/netfilter/xt_limit.h> | |
1da177e4 LT |
16 | |
17 | MODULE_LICENSE("GPL"); | |
18 | MODULE_AUTHOR("Herve Eychenne <rv@wallfire.org>"); | |
2ae15b64 | 19 | MODULE_DESCRIPTION("Xtables: rate-limit match"); |
2e4e6a17 HW |
20 | MODULE_ALIAS("ipt_limit"); |
21 | MODULE_ALIAS("ip6t_limit"); | |
1da177e4 LT |
22 | |
23 | /* The algorithm used is the Simple Token Bucket Filter (TBF) | |
24 | * see net/sched/sch_tbf.c in the linux source tree | |
25 | */ | |
26 | ||
27 | static DEFINE_SPINLOCK(limit_lock); | |
28 | ||
29 | /* Rusty: This is my (non-mathematically-inclined) understanding of | |
30 | this algorithm. The `average rate' in jiffies becomes your initial | |
31 | amount of credit `credit' and the most credit you can ever have | |
32 | `credit_cap'. The `peak rate' becomes the cost of passing the | |
33 | test, `cost'. | |
34 | ||
35 | `prev' tracks the last packet hit: you gain one credit per jiffy. | |
36 | If you get credit balance more than this, the extra credit is | |
37 | discarded. Every time the match passes, you lose `cost' credits; | |
38 | if you don't have that many, the test fails. | |
39 | ||
40 | See Alexey's formal explanation in net/sched/sch_tbf.c. | |
41 | ||
42 | To get the maxmum range, we multiply by this factor (ie. you get N | |
43 | credits per jiffy). We want to allow a rate as low as 1 per day | |
44 | (slowest userspace tool allows), which means | |
45 | CREDITS_PER_JIFFY*HZ*60*60*24 < 2^32. ie. */ | |
46 | #define MAX_CPJ (0xFFFFFFFF / (HZ*60*60*24)) | |
47 | ||
48 | /* Repeated shift and or gives us all 1s, final shift and add 1 gives | |
49 | * us the power of 2 below the theoretical max, so GCC simply does a | |
50 | * shift. */ | |
51 | #define _POW2_BELOW2(x) ((x)|((x)>>1)) | |
52 | #define _POW2_BELOW4(x) (_POW2_BELOW2(x)|_POW2_BELOW2((x)>>2)) | |
53 | #define _POW2_BELOW8(x) (_POW2_BELOW4(x)|_POW2_BELOW4((x)>>4)) | |
54 | #define _POW2_BELOW16(x) (_POW2_BELOW8(x)|_POW2_BELOW8((x)>>8)) | |
55 | #define _POW2_BELOW32(x) (_POW2_BELOW16(x)|_POW2_BELOW16((x)>>16)) | |
56 | #define POW2_BELOW32(x) ((_POW2_BELOW32(x)>>1) + 1) | |
57 | ||
58 | #define CREDITS_PER_JIFFY POW2_BELOW32(MAX_CPJ) | |
59 | ||
1d93a9cb | 60 | static bool |
d3c5ee6d JE |
61 | limit_mt(const struct sk_buff *skb, const struct net_device *in, |
62 | const struct net_device *out, const struct xt_match *match, | |
63 | const void *matchinfo, int offset, unsigned int protoff, | |
64 | bool *hotdrop) | |
1da177e4 | 65 | { |
a47362a2 JE |
66 | struct xt_rateinfo *r = |
67 | ((const struct xt_rateinfo *)matchinfo)->master; | |
1da177e4 LT |
68 | unsigned long now = jiffies; |
69 | ||
70 | spin_lock_bh(&limit_lock); | |
71 | r->credit += (now - xchg(&r->prev, now)) * CREDITS_PER_JIFFY; | |
72 | if (r->credit > r->credit_cap) | |
73 | r->credit = r->credit_cap; | |
74 | ||
75 | if (r->credit >= r->cost) { | |
76 | /* We're not limited. */ | |
77 | r->credit -= r->cost; | |
78 | spin_unlock_bh(&limit_lock); | |
1d93a9cb | 79 | return true; |
1da177e4 LT |
80 | } |
81 | ||
601e68e1 | 82 | spin_unlock_bh(&limit_lock); |
1d93a9cb | 83 | return false; |
1da177e4 LT |
84 | } |
85 | ||
86 | /* Precision saver. */ | |
87 | static u_int32_t | |
88 | user2credits(u_int32_t user) | |
89 | { | |
90 | /* If multiplying would overflow... */ | |
91 | if (user > 0xFFFFFFFF / (HZ*CREDITS_PER_JIFFY)) | |
92 | /* Divide first. */ | |
2e4e6a17 | 93 | return (user / XT_LIMIT_SCALE) * HZ * CREDITS_PER_JIFFY; |
1da177e4 | 94 | |
2e4e6a17 | 95 | return (user * HZ * CREDITS_PER_JIFFY) / XT_LIMIT_SCALE; |
1da177e4 LT |
96 | } |
97 | ||
ccb79bdc | 98 | static bool |
d3c5ee6d JE |
99 | limit_mt_check(const char *tablename, const void *inf, |
100 | const struct xt_match *match, void *matchinfo, | |
101 | unsigned int hook_mask) | |
1da177e4 | 102 | { |
2e4e6a17 | 103 | struct xt_rateinfo *r = matchinfo; |
1da177e4 | 104 | |
1da177e4 LT |
105 | /* Check for overflow. */ |
106 | if (r->burst == 0 | |
107 | || user2credits(r->avg * r->burst) < user2credits(r->avg)) { | |
2e4e6a17 | 108 | printk("Overflow in xt_limit, try lower: %u/%u\n", |
1da177e4 | 109 | r->avg, r->burst); |
ccb79bdc | 110 | return false; |
1da177e4 LT |
111 | } |
112 | ||
1da177e4 LT |
113 | /* For SMP, we only want to use one set of counters. */ |
114 | r->master = r; | |
57dab5d0 PM |
115 | if (r->cost == 0) { |
116 | /* User avg in seconds * XT_LIMIT_SCALE: convert to jiffies * | |
117 | 128. */ | |
118 | r->prev = jiffies; | |
119 | r->credit = user2credits(r->avg * r->burst); /* Credits full. */ | |
120 | r->credit_cap = user2credits(r->avg * r->burst); /* Credits full. */ | |
121 | r->cost = user2credits(r->avg); | |
122 | } | |
ccb79bdc | 123 | return true; |
1da177e4 LT |
124 | } |
125 | ||
02c63cf7 PM |
126 | #ifdef CONFIG_COMPAT |
127 | struct compat_xt_rateinfo { | |
128 | u_int32_t avg; | |
129 | u_int32_t burst; | |
130 | ||
131 | compat_ulong_t prev; | |
132 | u_int32_t credit; | |
133 | u_int32_t credit_cap, cost; | |
134 | ||
135 | u_int32_t master; | |
136 | }; | |
137 | ||
138 | /* To keep the full "prev" timestamp, the upper 32 bits are stored in the | |
139 | * master pointer, which does not need to be preserved. */ | |
d3c5ee6d | 140 | static void limit_mt_compat_from_user(void *dst, void *src) |
02c63cf7 | 141 | { |
a47362a2 | 142 | const struct compat_xt_rateinfo *cm = src; |
02c63cf7 PM |
143 | struct xt_rateinfo m = { |
144 | .avg = cm->avg, | |
145 | .burst = cm->burst, | |
146 | .prev = cm->prev | (unsigned long)cm->master << 32, | |
147 | .credit = cm->credit, | |
148 | .credit_cap = cm->credit_cap, | |
149 | .cost = cm->cost, | |
150 | }; | |
151 | memcpy(dst, &m, sizeof(m)); | |
152 | } | |
153 | ||
d3c5ee6d | 154 | static int limit_mt_compat_to_user(void __user *dst, void *src) |
02c63cf7 | 155 | { |
a47362a2 | 156 | const struct xt_rateinfo *m = src; |
02c63cf7 PM |
157 | struct compat_xt_rateinfo cm = { |
158 | .avg = m->avg, | |
159 | .burst = m->burst, | |
160 | .prev = m->prev, | |
161 | .credit = m->credit, | |
162 | .credit_cap = m->credit_cap, | |
163 | .cost = m->cost, | |
164 | .master = m->prev >> 32, | |
165 | }; | |
166 | return copy_to_user(dst, &cm, sizeof(cm)) ? -EFAULT : 0; | |
167 | } | |
168 | #endif /* CONFIG_COMPAT */ | |
169 | ||
d3c5ee6d | 170 | static struct xt_match limit_mt_reg[] __read_mostly = { |
4470bbc7 PM |
171 | { |
172 | .name = "limit", | |
ee999d8b | 173 | .family = NFPROTO_IPV4, |
d3c5ee6d JE |
174 | .checkentry = limit_mt_check, |
175 | .match = limit_mt, | |
4470bbc7 | 176 | .matchsize = sizeof(struct xt_rateinfo), |
02c63cf7 PM |
177 | #ifdef CONFIG_COMPAT |
178 | .compatsize = sizeof(struct compat_xt_rateinfo), | |
d3c5ee6d JE |
179 | .compat_from_user = limit_mt_compat_from_user, |
180 | .compat_to_user = limit_mt_compat_to_user, | |
02c63cf7 | 181 | #endif |
4470bbc7 PM |
182 | .me = THIS_MODULE, |
183 | }, | |
184 | { | |
185 | .name = "limit", | |
ee999d8b | 186 | .family = NFPROTO_IPV6, |
d3c5ee6d JE |
187 | .checkentry = limit_mt_check, |
188 | .match = limit_mt, | |
4470bbc7 | 189 | .matchsize = sizeof(struct xt_rateinfo), |
34f4c429 PM |
190 | #ifdef CONFIG_COMPAT |
191 | .compatsize = sizeof(struct compat_xt_rateinfo), | |
192 | .compat_from_user = limit_mt_compat_from_user, | |
193 | .compat_to_user = limit_mt_compat_to_user, | |
194 | #endif | |
4470bbc7 PM |
195 | .me = THIS_MODULE, |
196 | }, | |
1da177e4 LT |
197 | }; |
198 | ||
d3c5ee6d | 199 | static int __init limit_mt_init(void) |
1da177e4 | 200 | { |
d3c5ee6d | 201 | return xt_register_matches(limit_mt_reg, ARRAY_SIZE(limit_mt_reg)); |
1da177e4 LT |
202 | } |
203 | ||
d3c5ee6d | 204 | static void __exit limit_mt_exit(void) |
1da177e4 | 205 | { |
d3c5ee6d | 206 | xt_unregister_matches(limit_mt_reg, ARRAY_SIZE(limit_mt_reg)); |
1da177e4 LT |
207 | } |
208 | ||
d3c5ee6d JE |
209 | module_init(limit_mt_init); |
210 | module_exit(limit_mt_exit); |