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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
  16 #include <linux/netfilter/xt_statistic.h>
  17 #include <linux/netfilter/x_tables.h>
  18
  19 MODULE_LICENSE("GPL");
  20 MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
  21 MODULE_DESCRIPTION("Xtables: statistics-based matching (\"Nth\", random)");
  22 MODULE_ALIAS("ipt_statistic");
  23 MODULE_ALIAS("ip6t_statistic");
  24
  25 static DEFINE_SPINLOCK(nth_lock);
  26
  27 static bool
  28 statistic_mt(const struct sk_buff *skb, const struct xt_match_param *par)
  29 {
  30         struct xt_statistic_info *info = (void *)par->matchinfo;
  31         bool ret = info->flags & XT_STATISTIC_INVERT;
  32
  33         switch (info->mode) {
  34         case XT_STATISTIC_MODE_RANDOM:
  35                 if ((net_random() & 0x7FFFFFFF) < info->u.random.probability)
  36                         ret = !ret;
  37                 break;
  38         case XT_STATISTIC_MODE_NTH:
  39                 info = info->master;
  40                 spin_lock_bh(&nth_lock);
  41                 if (info->u.nth.count++ == info->u.nth.every) {
  42                         info->u.nth.count = 0;
  43                         ret = !ret;
  44                 }
  45                 spin_unlock_bh(&nth_lock);
  46                 break;
  47         }
  48
  49         return ret;
  50 }
  51
  52 static bool
  53 statistic_mt_check(const char *tablename, const void *entry,
  54                    const struct xt_match *match, void *matchinfo,
  55                    unsigned int hook_mask)
  56 {
  57         struct xt_statistic_info *info = matchinfo;
  58
  59         if (info->mode > XT_STATISTIC_MODE_MAX ||
  60             info->flags & ~XT_STATISTIC_MASK)
  61                 return false;
  62         info->master = info;
  63         return true;
  64 }
  65
  66 static struct xt_match xt_statistic_mt_reg __read_mostly = {
  67         .name       = "statistic",
  68         .revision   = 0,
  69         .family     = NFPROTO_UNSPEC,
  70         .match      = statistic_mt,
  71         .checkentry = statistic_mt_check,
  72         .matchsize  = sizeof(struct xt_statistic_info),
  73         .me         = THIS_MODULE,
  74 };
  75
  76 static int __init statistic_mt_init(void)
  77 {
  78         return xt_register_match(&xt_statistic_mt_reg);
  79 }
  80
  81 static void __exit statistic_mt_exit(void)
  82 {
  83         xt_unregister_match(&xt_statistic_mt_reg);
  84 }
  85
  86 module_init(statistic_mt_init);
  87 module_exit(statistic_mt_exit);