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d2912cb1 | 1 | // SPDX-License-Identifier: GPL-2.0-only |
db955170 MG |
2 | /* (C) 1999 Jérôme de Vivie <devivie@info.enserb.u-bordeaux.fr> |
3 | * (C) 1999 Hervé Eychenne <eychenne@info.enserb.u-bordeaux.fr> | |
f229f6ce | 4 | * (C) 2006-2012 Patrick McHardy <kaber@trash.net> |
1da177e4 | 5 | */ |
8bee4bad | 6 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
1da177e4 | 7 | |
5a0e3ad6 | 8 | #include <linux/slab.h> |
1da177e4 LT |
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 | 16 | |
acc738fe | 17 | struct xt_limit_priv { |
2cb4bbd7 | 18 | spinlock_t lock; |
acc738fe JE |
19 | unsigned long prev; |
20 | uint32_t credit; | |
21 | }; | |
22 | ||
1da177e4 LT |
23 | MODULE_LICENSE("GPL"); |
24 | MODULE_AUTHOR("Herve Eychenne <rv@wallfire.org>"); | |
2ae15b64 | 25 | MODULE_DESCRIPTION("Xtables: rate-limit match"); |
2e4e6a17 HW |
26 | MODULE_ALIAS("ipt_limit"); |
27 | MODULE_ALIAS("ip6t_limit"); | |
1da177e4 LT |
28 | |
29 | /* The algorithm used is the Simple Token Bucket Filter (TBF) | |
30 | * see net/sched/sch_tbf.c in the linux source tree | |
31 | */ | |
32 | ||
1da177e4 LT |
33 | /* Rusty: This is my (non-mathematically-inclined) understanding of |
34 | this algorithm. The `average rate' in jiffies becomes your initial | |
35 | amount of credit `credit' and the most credit you can ever have | |
36 | `credit_cap'. The `peak rate' becomes the cost of passing the | |
37 | test, `cost'. | |
38 | ||
39 | `prev' tracks the last packet hit: you gain one credit per jiffy. | |
40 | If you get credit balance more than this, the extra credit is | |
41 | discarded. Every time the match passes, you lose `cost' credits; | |
42 | if you don't have that many, the test fails. | |
43 | ||
44 | See Alexey's formal explanation in net/sched/sch_tbf.c. | |
45 | ||
010eacd9 | 46 | To get the maximum range, we multiply by this factor (ie. you get N |
1da177e4 LT |
47 | credits per jiffy). We want to allow a rate as low as 1 per day |
48 | (slowest userspace tool allows), which means | |
49 | CREDITS_PER_JIFFY*HZ*60*60*24 < 2^32. ie. */ | |
50 | #define MAX_CPJ (0xFFFFFFFF / (HZ*60*60*24)) | |
51 | ||
52 | /* Repeated shift and or gives us all 1s, final shift and add 1 gives | |
53 | * us the power of 2 below the theoretical max, so GCC simply does a | |
54 | * shift. */ | |
55 | #define _POW2_BELOW2(x) ((x)|((x)>>1)) | |
56 | #define _POW2_BELOW4(x) (_POW2_BELOW2(x)|_POW2_BELOW2((x)>>2)) | |
57 | #define _POW2_BELOW8(x) (_POW2_BELOW4(x)|_POW2_BELOW4((x)>>4)) | |
58 | #define _POW2_BELOW16(x) (_POW2_BELOW8(x)|_POW2_BELOW8((x)>>8)) | |
59 | #define _POW2_BELOW32(x) (_POW2_BELOW16(x)|_POW2_BELOW16((x)>>16)) | |
60 | #define POW2_BELOW32(x) ((_POW2_BELOW32(x)>>1) + 1) | |
61 | ||
62 | #define CREDITS_PER_JIFFY POW2_BELOW32(MAX_CPJ) | |
63 | ||
1d93a9cb | 64 | static bool |
62fc8051 | 65 | limit_mt(const struct sk_buff *skb, struct xt_action_param *par) |
1da177e4 | 66 | { |
acc738fe JE |
67 | const struct xt_rateinfo *r = par->matchinfo; |
68 | struct xt_limit_priv *priv = r->master; | |
1da177e4 LT |
69 | unsigned long now = jiffies; |
70 | ||
2cb4bbd7 | 71 | spin_lock_bh(&priv->lock); |
acc738fe JE |
72 | priv->credit += (now - xchg(&priv->prev, now)) * CREDITS_PER_JIFFY; |
73 | if (priv->credit > r->credit_cap) | |
74 | priv->credit = r->credit_cap; | |
1da177e4 | 75 | |
acc738fe | 76 | if (priv->credit >= r->cost) { |
1da177e4 | 77 | /* We're not limited. */ |
acc738fe | 78 | priv->credit -= r->cost; |
2cb4bbd7 | 79 | spin_unlock_bh(&priv->lock); |
1d93a9cb | 80 | return true; |
1da177e4 LT |
81 | } |
82 | ||
2cb4bbd7 | 83 | spin_unlock_bh(&priv->lock); |
1d93a9cb | 84 | return false; |
1da177e4 LT |
85 | } |
86 | ||
87 | /* Precision saver. */ | |
7a909ac7 | 88 | static u32 user2credits(u32 user) |
1da177e4 LT |
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 | ||
b0f38452 | 98 | static int limit_mt_check(const struct xt_mtchk_param *par) |
1da177e4 | 99 | { |
9b4fce7a | 100 | struct xt_rateinfo *r = par->matchinfo; |
acc738fe | 101 | struct xt_limit_priv *priv; |
1da177e4 | 102 | |
1da177e4 LT |
103 | /* Check for overflow. */ |
104 | if (r->burst == 0 | |
105 | || user2credits(r->avg * r->burst) < user2credits(r->avg)) { | |
b2606644 FW |
106 | pr_info_ratelimited("Overflow, try lower: %u/%u\n", |
107 | r->avg, r->burst); | |
4a5a5c73 | 108 | return -ERANGE; |
1da177e4 LT |
109 | } |
110 | ||
acc738fe JE |
111 | priv = kmalloc(sizeof(*priv), GFP_KERNEL); |
112 | if (priv == NULL) | |
4a5a5c73 | 113 | return -ENOMEM; |
acc738fe JE |
114 | |
115 | /* For SMP, we only want to use one set of state. */ | |
116 | r->master = priv; | |
82e6bfe2 JE |
117 | /* User avg in seconds * XT_LIMIT_SCALE: convert to jiffies * |
118 | 128. */ | |
119 | priv->prev = jiffies; | |
120 | priv->credit = user2credits(r->avg * r->burst); /* Credits full. */ | |
57dab5d0 | 121 | if (r->cost == 0) { |
7a909ac7 | 122 | r->credit_cap = priv->credit; /* Credits full. */ |
57dab5d0 PM |
123 | r->cost = user2credits(r->avg); |
124 | } | |
2cb4bbd7 LZ |
125 | spin_lock_init(&priv->lock); |
126 | ||
bd414ee6 | 127 | return 0; |
1da177e4 LT |
128 | } |
129 | ||
acc738fe JE |
130 | static void limit_mt_destroy(const struct xt_mtdtor_param *par) |
131 | { | |
132 | const struct xt_rateinfo *info = par->matchinfo; | |
133 | ||
134 | kfree(info->master); | |
135 | } | |
136 | ||
02c63cf7 PM |
137 | #ifdef CONFIG_COMPAT |
138 | struct compat_xt_rateinfo { | |
139 | u_int32_t avg; | |
140 | u_int32_t burst; | |
141 | ||
142 | compat_ulong_t prev; | |
143 | u_int32_t credit; | |
144 | u_int32_t credit_cap, cost; | |
145 | ||
146 | u_int32_t master; | |
147 | }; | |
148 | ||
149 | /* To keep the full "prev" timestamp, the upper 32 bits are stored in the | |
150 | * master pointer, which does not need to be preserved. */ | |
739674fb | 151 | static void limit_mt_compat_from_user(void *dst, const void *src) |
02c63cf7 | 152 | { |
a47362a2 | 153 | const struct compat_xt_rateinfo *cm = src; |
02c63cf7 PM |
154 | struct xt_rateinfo m = { |
155 | .avg = cm->avg, | |
156 | .burst = cm->burst, | |
157 | .prev = cm->prev | (unsigned long)cm->master << 32, | |
158 | .credit = cm->credit, | |
159 | .credit_cap = cm->credit_cap, | |
160 | .cost = cm->cost, | |
161 | }; | |
162 | memcpy(dst, &m, sizeof(m)); | |
163 | } | |
164 | ||
739674fb | 165 | static int limit_mt_compat_to_user(void __user *dst, const void *src) |
02c63cf7 | 166 | { |
a47362a2 | 167 | const struct xt_rateinfo *m = src; |
02c63cf7 PM |
168 | struct compat_xt_rateinfo cm = { |
169 | .avg = m->avg, | |
170 | .burst = m->burst, | |
171 | .prev = m->prev, | |
172 | .credit = m->credit, | |
173 | .credit_cap = m->credit_cap, | |
174 | .cost = m->cost, | |
175 | .master = m->prev >> 32, | |
176 | }; | |
177 | return copy_to_user(dst, &cm, sizeof(cm)) ? -EFAULT : 0; | |
178 | } | |
179 | #endif /* CONFIG_COMPAT */ | |
180 | ||
55b69e91 JE |
181 | static struct xt_match limit_mt_reg __read_mostly = { |
182 | .name = "limit", | |
183 | .revision = 0, | |
184 | .family = NFPROTO_UNSPEC, | |
185 | .match = limit_mt, | |
186 | .checkentry = limit_mt_check, | |
acc738fe | 187 | .destroy = limit_mt_destroy, |
55b69e91 | 188 | .matchsize = sizeof(struct xt_rateinfo), |
02c63cf7 | 189 | #ifdef CONFIG_COMPAT |
55b69e91 JE |
190 | .compatsize = sizeof(struct compat_xt_rateinfo), |
191 | .compat_from_user = limit_mt_compat_from_user, | |
192 | .compat_to_user = limit_mt_compat_to_user, | |
02c63cf7 | 193 | #endif |
1e98ffea | 194 | .usersize = offsetof(struct xt_rateinfo, prev), |
55b69e91 | 195 | .me = THIS_MODULE, |
1da177e4 LT |
196 | }; |
197 | ||
d3c5ee6d | 198 | static int __init limit_mt_init(void) |
1da177e4 | 199 | { |
55b69e91 | 200 | return xt_register_match(&limit_mt_reg); |
1da177e4 LT |
201 | } |
202 | ||
d3c5ee6d | 203 | static void __exit limit_mt_exit(void) |
1da177e4 | 204 | { |
55b69e91 | 205 | xt_unregister_match(&limit_mt_reg); |
1da177e4 LT |
206 | } |
207 | ||
d3c5ee6d JE |
208 | module_init(limit_mt_init); |
209 | module_exit(limit_mt_exit); |