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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> | |
f229f6ce | 3 | * (C) 2006-2012 Patrick McHardy <kaber@trash.net> |
1da177e4 LT |
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 | */ | |
8bee4bad | 9 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
1da177e4 | 10 | |
5a0e3ad6 | 11 | #include <linux/slab.h> |
1da177e4 LT |
12 | #include <linux/module.h> |
13 | #include <linux/skbuff.h> | |
14 | #include <linux/spinlock.h> | |
15 | #include <linux/interrupt.h> | |
16 | ||
2e4e6a17 HW |
17 | #include <linux/netfilter/x_tables.h> |
18 | #include <linux/netfilter/xt_limit.h> | |
1da177e4 | 19 | |
acc738fe JE |
20 | struct xt_limit_priv { |
21 | unsigned long prev; | |
22 | uint32_t credit; | |
23 | }; | |
24 | ||
1da177e4 LT |
25 | MODULE_LICENSE("GPL"); |
26 | MODULE_AUTHOR("Herve Eychenne <rv@wallfire.org>"); | |
2ae15b64 | 27 | MODULE_DESCRIPTION("Xtables: rate-limit match"); |
2e4e6a17 HW |
28 | MODULE_ALIAS("ipt_limit"); |
29 | MODULE_ALIAS("ip6t_limit"); | |
1da177e4 LT |
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 | ||
35 | static 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 | ||
1d93a9cb | 68 | static bool |
62fc8051 | 69 | limit_mt(const struct sk_buff *skb, struct xt_action_param *par) |
1da177e4 | 70 | { |
acc738fe JE |
71 | const struct xt_rateinfo *r = par->matchinfo; |
72 | struct xt_limit_priv *priv = r->master; | |
1da177e4 LT |
73 | unsigned long now = jiffies; |
74 | ||
75 | spin_lock_bh(&limit_lock); | |
acc738fe JE |
76 | priv->credit += (now - xchg(&priv->prev, now)) * CREDITS_PER_JIFFY; |
77 | if (priv->credit > r->credit_cap) | |
78 | priv->credit = r->credit_cap; | |
1da177e4 | 79 | |
acc738fe | 80 | if (priv->credit >= r->cost) { |
1da177e4 | 81 | /* We're not limited. */ |
acc738fe | 82 | priv->credit -= r->cost; |
1da177e4 | 83 | spin_unlock_bh(&limit_lock); |
1d93a9cb | 84 | return true; |
1da177e4 LT |
85 | } |
86 | ||
601e68e1 | 87 | spin_unlock_bh(&limit_lock); |
1d93a9cb | 88 | return false; |
1da177e4 LT |
89 | } |
90 | ||
91 | /* Precision saver. */ | |
7a909ac7 | 92 | static u32 user2credits(u32 user) |
1da177e4 LT |
93 | { |
94 | /* If multiplying would overflow... */ | |
95 | if (user > 0xFFFFFFFF / (HZ*CREDITS_PER_JIFFY)) | |
96 | /* Divide first. */ | |
2e4e6a17 | 97 | return (user / XT_LIMIT_SCALE) * HZ * CREDITS_PER_JIFFY; |
1da177e4 | 98 | |
2e4e6a17 | 99 | return (user * HZ * CREDITS_PER_JIFFY) / XT_LIMIT_SCALE; |
1da177e4 LT |
100 | } |
101 | ||
b0f38452 | 102 | static int limit_mt_check(const struct xt_mtchk_param *par) |
1da177e4 | 103 | { |
9b4fce7a | 104 | struct xt_rateinfo *r = par->matchinfo; |
acc738fe | 105 | struct xt_limit_priv *priv; |
1da177e4 | 106 | |
1da177e4 LT |
107 | /* Check for overflow. */ |
108 | if (r->burst == 0 | |
109 | || user2credits(r->avg * r->burst) < user2credits(r->avg)) { | |
8bee4bad JE |
110 | pr_info("Overflow, try lower: %u/%u\n", |
111 | r->avg, r->burst); | |
4a5a5c73 | 112 | return -ERANGE; |
1da177e4 LT |
113 | } |
114 | ||
acc738fe JE |
115 | priv = kmalloc(sizeof(*priv), GFP_KERNEL); |
116 | if (priv == NULL) | |
4a5a5c73 | 117 | return -ENOMEM; |
acc738fe JE |
118 | |
119 | /* For SMP, we only want to use one set of state. */ | |
120 | r->master = priv; | |
82e6bfe2 JE |
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. */ | |
57dab5d0 | 125 | if (r->cost == 0) { |
7a909ac7 | 126 | r->credit_cap = priv->credit; /* Credits full. */ |
57dab5d0 PM |
127 | r->cost = user2credits(r->avg); |
128 | } | |
bd414ee6 | 129 | return 0; |
1da177e4 LT |
130 | } |
131 | ||
acc738fe JE |
132 | static 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 | ||
02c63cf7 PM |
139 | #ifdef CONFIG_COMPAT |
140 | struct 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. */ | |
739674fb | 153 | static void limit_mt_compat_from_user(void *dst, const void *src) |
02c63cf7 | 154 | { |
a47362a2 | 155 | const struct compat_xt_rateinfo *cm = src; |
02c63cf7 PM |
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 | ||
739674fb | 167 | static int limit_mt_compat_to_user(void __user *dst, const void *src) |
02c63cf7 | 168 | { |
a47362a2 | 169 | const struct xt_rateinfo *m = src; |
02c63cf7 PM |
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 | ||
55b69e91 JE |
183 | static 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, | |
acc738fe | 189 | .destroy = limit_mt_destroy, |
55b69e91 | 190 | .matchsize = sizeof(struct xt_rateinfo), |
02c63cf7 | 191 | #ifdef CONFIG_COMPAT |
55b69e91 JE |
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, | |
02c63cf7 | 195 | #endif |
55b69e91 | 196 | .me = THIS_MODULE, |
1da177e4 LT |
197 | }; |
198 | ||
d3c5ee6d | 199 | static int __init limit_mt_init(void) |
1da177e4 | 200 | { |
55b69e91 | 201 | return xt_register_match(&limit_mt_reg); |
1da177e4 LT |
202 | } |
203 | ||
d3c5ee6d | 204 | static void __exit limit_mt_exit(void) |
1da177e4 | 205 | { |
55b69e91 | 206 | xt_unregister_match(&limit_mt_reg); |
1da177e4 LT |
207 | } |
208 | ||
d3c5ee6d JE |
209 | module_init(limit_mt_init); |
210 | module_exit(limit_mt_exit); |