ipvs: convert lblc scheduler to rcu
[linux-3.10.git] / net / netfilter / xt_statistic.c
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 ((net_random() & 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);