release/src-rt-6.x/linux/linux-2.6/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 struct xt_statistic_priv {
  20         uint32_t count;
  21 };
  22
  23 MODULE_LICENSE("GPL");
  24 MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
  25 MODULE_DESCRIPTION("Xtables: statistics-based matching (\"Nth\", random)");
  26 MODULE_ALIAS("ipt_statistic");
  27 MODULE_ALIAS("ip6t_statistic");
  28
  29 static DEFINE_SPINLOCK(nth_lock);
  30
  31 static int
  32 match(const struct sk_buff *skb,
  33       const struct net_device *in, const struct net_device *out,
  34       const struct xt_match *match, const void *matchinfo,
  35       int offset, unsigned int protoff, int *hotdrop)
  36 {
  37         const struct xt_statistic_info *info = matchinfo;
  38         int ret = info->flags & XT_STATISTIC_INVERT ? 1 : 0;
  39
  40         switch (info->mode) {
  41         case XT_STATISTIC_MODE_RANDOM:
  42                 if ((net_random() & 0x7FFFFFFF) < info->u.random.probability)
  43                         ret ^= 1;
  44                 break;
  45         case XT_STATISTIC_MODE_NTH:
  46                 spin_lock_bh(&nth_lock);
  47                 if (info->master->count++ == info->u.nth.every) {
  48                         info->master->count = 0;
  49                         ret ^= 1;
  50                 }
  51                 spin_unlock_bh(&nth_lock);
  52                 break;
  53         }
  54
  55         return ret;
  56 }
  57
  58 static int
  59 checkentry(const char *tablename, const void *entry,
  60            const struct xt_match *match, void *matchinfo,
  61            unsigned int hook_mask)
  62 {
  63         struct xt_statistic_info *info = (struct xt_statistic_info *)matchinfo;
  64
  65         if (info->mode > XT_STATISTIC_MODE_MAX ||
  66             info->flags & ~XT_STATISTIC_MASK)
  67                 return 0;
  68
  69         info->master = kzalloc(sizeof(*info->master), GFP_KERNEL);
  70         if (info->master == NULL) {
  71                 printk(KERN_ERR KBUILD_MODNAME ": Out of memory\n");
  72                 return 0;
  73         }
  74         info->master->count = info->u.nth.count;
  75
  76         return 1;
  77 }
  78
  79 static void statistic_mt_destroy(const struct xt_match *match, void *matchinfo)
  80 {
  81         const struct xt_statistic_info *info = matchinfo;
  82
  83         kfree(info->master);
  84 }
  85
  86 static struct xt_match xt_statistic_match[] = {
  87         {
  88                 .name           = "statistic",
  89                 .family         = AF_INET,
  90                 .checkentry     = checkentry,
  91                 .match          = match,
  92                 .destroy        = statistic_mt_destroy,
  93                 .matchsize      = sizeof(struct xt_statistic_info),
  94                 .me             = THIS_MODULE,
  95         },
  96         {
  97                 .name           = "statistic",
  98                 .family         = AF_INET6,
  99                 .checkentry     = checkentry,
 100                 .match          = match,
 101                 .destroy        = statistic_mt_destroy,
 102                 .matchsize      = sizeof(struct xt_statistic_info),
 103                 .me             = THIS_MODULE,
 104         },
 105 };
 106
 107 static int __init xt_statistic_init(void)
 108 {
 109         return xt_register_matches(xt_statistic_match,
 110                                    ARRAY_SIZE(xt_statistic_match));
 111 }
 112
 113 static void __exit xt_statistic_fini(void)
 114 {
 115         xt_unregister_matches(xt_statistic_match,
 116                               ARRAY_SIZE(xt_statistic_match));
 117 }
 118
 119 module_init(xt_statistic_init);
 120 module_exit(xt_statistic_fini);