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);