mac80211: fix another race in aggregation start
[linux-2.6.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
20 struct xt_statistic_priv {
21         atomic_t count;
22 } ____cacheline_aligned_in_smp;
23
24 MODULE_LICENSE("GPL");
25 MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
26 MODULE_DESCRIPTION("Xtables: statistics-based matching (\"Nth\", random)");
27 MODULE_ALIAS("ipt_statistic");
28 MODULE_ALIAS("ip6t_statistic");
29
30 static bool
31 statistic_mt(const struct sk_buff *skb, struct xt_action_param *par)
32 {
33         const struct xt_statistic_info *info = par->matchinfo;
34         bool ret = info->flags & XT_STATISTIC_INVERT;
35         int nval, oval;
36
37         switch (info->mode) {
38         case XT_STATISTIC_MODE_RANDOM:
39                 if ((net_random() & 0x7FFFFFFF) < info->u.random.probability)
40                         ret = !ret;
41                 break;
42         case XT_STATISTIC_MODE_NTH:
43                 do {
44                         oval = atomic_read(&info->master->count);
45                         nval = (oval == info->u.nth.every) ? 0 : oval + 1;
46                 } while (atomic_cmpxchg(&info->master->count, oval, nval) != oval);
47                 if (nval == 0)
48                         ret = !ret;
49                 break;
50         }
51
52         return ret;
53 }
54
55 static int statistic_mt_check(const struct xt_mtchk_param *par)
56 {
57         struct xt_statistic_info *info = par->matchinfo;
58
59         if (info->mode > XT_STATISTIC_MODE_MAX ||
60             info->flags & ~XT_STATISTIC_MASK)
61                 return -EINVAL;
62
63         info->master = kzalloc(sizeof(*info->master), GFP_KERNEL);
64         if (info->master == NULL)
65                 return -ENOMEM;
66         atomic_set(&info->master->count, info->u.nth.count);
67
68         return 0;
69 }
70
71 static void statistic_mt_destroy(const struct xt_mtdtor_param *par)
72 {
73         const struct xt_statistic_info *info = par->matchinfo;
74
75         kfree(info->master);
76 }
77
78 static struct xt_match xt_statistic_mt_reg __read_mostly = {
79         .name       = "statistic",
80         .revision   = 0,
81         .family     = NFPROTO_UNSPEC,
82         .match      = statistic_mt,
83         .checkentry = statistic_mt_check,
84         .destroy    = statistic_mt_destroy,
85         .matchsize  = sizeof(struct xt_statistic_info),
86         .me         = THIS_MODULE,
87 };
88
89 static int __init statistic_mt_init(void)
90 {
91         return xt_register_match(&xt_statistic_mt_reg);
92 }
93
94 static void __exit statistic_mt_exit(void)
95 {
96         xt_unregister_match(&xt_statistic_mt_reg);
97 }
98
99 module_init(statistic_mt_init);
100 module_exit(statistic_mt_exit);