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 #include <linux/module.h>
  20
  21 struct xt_statistic_priv {
  22         atomic_t count;
  23 } ____cacheline_aligned_in_smp;
  24
  25 MODULE_LICENSE("GPL");
  26 MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
  27 MODULE_DESCRIPTION("Xtables: statistics-based matching (\"Nth\", random)");
  28 MODULE_ALIAS("ipt_statistic");
  29 MODULE_ALIAS("ip6t_statistic");
  30
  31 static bool
  32 statistic_mt(const struct sk_buff *skb, struct xt_action_param *par)
  33 {
  34         const struct xt_statistic_info *info = par->matchinfo;
  35         bool ret = info->flags & XT_STATISTIC_INVERT;
  36         int nval, oval;
  37
  38         switch (info->mode) {
  39         case XT_STATISTIC_MODE_RANDOM:
  40                 if ((prandom_u32() & 0x7FFFFFFF) < info->u.random.probability)
  41                         ret = !ret;
  42                 break;
  43         case XT_STATISTIC_MODE_NTH:
  44                 do {
  45                         oval = atomic_read(&info->master->count);
  46                         nval = (oval == info->u.nth.every) ? 0 : oval + 1;
  47                 } while (atomic_cmpxchg(&info->master->count, oval, nval) != oval);
  48                 if (nval == 0)
  49                         ret = !ret;
  50                 break;
  51         }
  52
  53         return ret;
  54 }
  55
  56 static int 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 -EINVAL;
  63
  64         info->master = kzalloc(sizeof(*info->master), GFP_KERNEL);
  65         if (info->master == NULL)
  66                 return -ENOMEM;
  67         atomic_set(&info->master->count, info->u.nth.count);
  68
  69         return 0;
  70 }
  71
  72 static void statistic_mt_destroy(const struct xt_mtdtor_param *par)
  73 {
  74         const struct xt_statistic_info *info = par->matchinfo;
  75
  76         kfree(info->master);
  77 }
  78
  79 static struct xt_match xt_statistic_mt_reg __read_mostly = {
  80         .name       = "statistic",
  81         .revision   = 0,
  82         .family     = NFPROTO_UNSPEC,
  83         .match      = statistic_mt,
  84         .checkentry = statistic_mt_check,
  85         .destroy    = statistic_mt_destroy,
  86         .matchsize  = sizeof(struct xt_statistic_info),
  87         .me         = THIS_MODULE,
  88 };
  89
  90 static int __init statistic_mt_init(void)
  91 {
  92         return xt_register_match(&xt_statistic_mt_reg);
  93 }
  94
  95 static void __exit statistic_mt_exit(void)
  96 {
  97         xt_unregister_match(&xt_statistic_mt_reg);
  98 }
  99
 100 module_init(statistic_mt_init);
 101 module_exit(statistic_mt_exit);