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
  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 net_device *in,
  29              const struct net_device *out, const struct xt_match *match,
  30              const void *matchinfo, int offset, unsigned int protoff,
  31              bool *hotdrop)
  32 {
  33         struct xt_statistic_info *info = (struct xt_statistic_info *)matchinfo;
  34         bool ret = info->flags & XT_STATISTIC_INVERT;
  35
  36         switch (info->mode) {
  37         case XT_STATISTIC_MODE_RANDOM:
  38                 if ((net_random() & 0x7FFFFFFF) < info->u.random.probability)
  39                         ret = !ret;
  40                 break;
  41         case XT_STATISTIC_MODE_NTH:
  42                 info = info->master;
  43                 spin_lock_bh(&nth_lock);
  44                 if (info->u.nth.count++ == info->u.nth.every) {
  45                         info->u.nth.count = 0;
  46                         ret = !ret;
  47                 }
  48                 spin_unlock_bh(&nth_lock);
  49                 break;
  50         }
  51
  52         return ret;
  53 }
  54
  55 static bool
  56 statistic_mt_check(const char *tablename, const void *entry,
  57                    const struct xt_match *match, void *matchinfo,
  58                    unsigned int hook_mask)
  59 {
  60         struct xt_statistic_info *info = matchinfo;
  61
  62         if (info->mode > XT_STATISTIC_MODE_MAX ||
  63             info->flags & ~XT_STATISTIC_MASK)
  64                 return false;
  65         info->master = info;
  66         return true;
  67 }
  68
  69 static struct xt_match statistic_mt_reg[] __read_mostly = {
  70         {
  71                 .name           = "statistic",
  72                 .family         = AF_INET,
  73                 .checkentry     = statistic_mt_check,
  74                 .match          = statistic_mt,
  75                 .matchsize      = sizeof(struct xt_statistic_info),
  76                 .me             = THIS_MODULE,
  77         },
  78         {
  79                 .name           = "statistic",
  80                 .family         = AF_INET6,
  81                 .checkentry     = statistic_mt_check,
  82                 .match          = statistic_mt,
  83                 .matchsize      = sizeof(struct xt_statistic_info),
  84                 .me             = THIS_MODULE,
  85         },
  86 };
  87
  88 static int __init statistic_mt_init(void)
  89 {
  90         return xt_register_matches(statistic_mt_reg,
  91                ARRAY_SIZE(statistic_mt_reg));
  92 }
  93
  94 static void __exit statistic_mt_exit(void)
  95 {
  96         xt_unregister_matches(statistic_mt_reg,
  97                               ARRAY_SIZE(statistic_mt_reg));
  98 }
  99
 100 module_init(statistic_mt_init);
 101 module_exit(statistic_mt_exit);