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1 | /* | |
2 | * Copyright (c) 2006 Patrick McHardy <kaber@trash.net> | |
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 | * Based on ipt_random and ipt_nth by Fabrice MARIE <fabrice@netfilter.org>. | |
9 | */ | |
10 | ||
11 | #include <linux/init.h> | |
12 | #include <linux/spinlock.h> | |
13 | #include <linux/skbuff.h> | |
14 | #include <linux/net.h> | |
15 | #include <linux/slab.h> | |
16 | ||
17 | #include <linux/netfilter/xt_statistic.h> | |
18 | #include <linux/netfilter/x_tables.h> | |
19 | #include <linux/module.h> | |
20 | ||
21 | struct xt_statistic_priv { | |
22 | atomic_t count; | |
23 | } ____cacheline_aligned_in_smp; | |
24 | ||
25 | MODULE_LICENSE("GPL"); | |
26 | MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>"); | |
27 | MODULE_DESCRIPTION("Xtables: statistics-based matching (\"Nth\", random)"); | |
28 | MODULE_ALIAS("ipt_statistic"); | |
29 | MODULE_ALIAS("ip6t_statistic"); | |
30 | ||
31 | static bool | |
32 | statistic_mt(const struct sk_buff *skb, struct xt_action_param *par) | |
33 | { | |
34 | const struct xt_statistic_info *info = par->matchinfo; | |
35 | bool ret = info->flags & XT_STATISTIC_INVERT; | |
36 | int nval, oval; | |
37 | ||
38 | switch (info->mode) { | |
39 | case XT_STATISTIC_MODE_RANDOM: | |
40 | if ((prandom_u32() & 0x7FFFFFFF) < info->u.random.probability) | |
41 | ret = !ret; | |
42 | break; | |
43 | case XT_STATISTIC_MODE_NTH: | |
44 | do { | |
45 | oval = atomic_read(&info->master->count); | |
46 | nval = (oval == info->u.nth.every) ? 0 : oval + 1; | |
47 | } while (atomic_cmpxchg(&info->master->count, oval, nval) != oval); | |
48 | if (nval == 0) | |
49 | ret = !ret; | |
50 | break; | |
51 | } | |
52 | ||
53 | return ret; | |
54 | } | |
55 | ||
56 | static int statistic_mt_check(const struct xt_mtchk_param *par) | |
57 | { | |
58 | struct xt_statistic_info *info = par->matchinfo; | |
59 | ||
60 | if (info->mode > XT_STATISTIC_MODE_MAX || | |
61 | info->flags & ~XT_STATISTIC_MASK) | |
62 | return -EINVAL; | |
63 | ||
64 | info->master = kzalloc(sizeof(*info->master), GFP_KERNEL); | |
65 | if (info->master == NULL) | |
66 | return -ENOMEM; | |
67 | atomic_set(&info->master->count, info->u.nth.count); | |
68 | ||
69 | return 0; | |
70 | } | |
71 | ||
72 | static void statistic_mt_destroy(const struct xt_mtdtor_param *par) | |
73 | { | |
74 | const struct xt_statistic_info *info = par->matchinfo; | |
75 | ||
76 | kfree(info->master); | |
77 | } | |
78 | ||
79 | static struct xt_match xt_statistic_mt_reg __read_mostly = { | |
80 | .name = "statistic", | |
81 | .revision = 0, | |
82 | .family = NFPROTO_UNSPEC, | |
83 | .match = statistic_mt, | |
84 | .checkentry = statistic_mt_check, | |
85 | .destroy = statistic_mt_destroy, | |
86 | .matchsize = sizeof(struct xt_statistic_info), | |
87 | .me = THIS_MODULE, | |
88 | }; | |
89 | ||
90 | static int __init statistic_mt_init(void) | |
91 | { | |
92 | return xt_register_match(&xt_statistic_mt_reg); | |
93 | } | |
94 | ||
95 | static void __exit statistic_mt_exit(void) | |
96 | { | |
97 | xt_unregister_match(&xt_statistic_mt_reg); | |
98 | } | |
99 | ||
100 | module_init(statistic_mt_init); | |
101 | module_exit(statistic_mt_exit); |