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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
  20 struct xt_statistic_priv {
  21         uint32_t count;
  22 };
  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 DEFINE_SPINLOCK(nth_lock);
  31
  32 static bool
  33 statistic_mt(const struct sk_buff *skb, const struct xt_match_param *par)
  34 {
  35         const struct xt_statistic_info *info = par->matchinfo;
  36         bool ret = info->flags & XT_STATISTIC_INVERT;
  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                 spin_lock_bh(&nth_lock);
  45                 if (info->master->count++ == info->u.nth.every) {
  46                         info->master->count = 0;
  47                         ret = !ret;
  48                 }
  49                 spin_unlock_bh(&nth_lock);
  50                 break;
  51         }
  52
  53         return ret;
  54 }
  55
  56 static bool 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 false;
  63
  64         info->master = kzalloc(sizeof(*info->master), GFP_KERNEL);
  65         if (info->master == NULL) {
  66                 printk(KERN_ERR KBUILD_MODNAME ": Out of memory\n");
  67                 return false;
  68         }
  69         info->master->count = info->u.nth.count;
  70
  71         return true;
  72 }
  73
  74 static void statistic_mt_destroy(const struct xt_mtdtor_param *par)
  75 {
  76         const struct xt_statistic_info *info = par->matchinfo;
  77
  78         kfree(info->master);
  79 }
  80
  81 static struct xt_match xt_statistic_mt_reg __read_mostly = {
  82         .name       = "statistic",
  83         .revision   = 0,
  84         .family     = NFPROTO_UNSPEC,
  85         .match      = statistic_mt,
  86         .checkentry = statistic_mt_check,
  87         .destroy    = statistic_mt_destroy,
  88         .matchsize  = sizeof(struct xt_statistic_info),
  89         .me         = THIS_MODULE,
  90 };
  91
  92 static int __init statistic_mt_init(void)
  93 {
  94         return xt_register_match(&xt_statistic_mt_reg);
  95 }
  96
  97 static void __exit statistic_mt_exit(void)
  98 {
  99         xt_unregister_match(&xt_statistic_mt_reg);
 100 }
 101
 102 module_init(statistic_mt_init);
 103 module_exit(statistic_mt_exit);