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Linux/net/netfilter/xt_statistic.c

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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 #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);
102 

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