LXR linux/net/netfilter/xt

   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 * Copyright (c) 2006 Patrick McHardy <kaber@trash.net>
   4 *
   5 * Based on ipt_random and ipt_nth by Fabrice MARIE <fabrice@netfilter.org>.
   6 */
   7
   8#include <linux/init.h>
   9#include <linux/spinlock.h>
  10#include <linux/skbuff.h>
  11#include <linux/net.h>
  12#include <linux/slab.h>
  13
  14#include <linux/netfilter/xt_statistic.h>
  15#include <linux/netfilter/x_tables.h>
  16#include <linux/module.h>
  17
  18struct xt_statistic_priv {
  19        atomic_t count;
  20} ____cacheline_aligned_in_smp;
  21
  22MODULE_LICENSE("GPL");
  23MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
  24MODULE_DESCRIPTION("Xtables: statistics-based matching (\"Nth\", random)");
  25MODULE_ALIAS("ipt_statistic");
  26MODULE_ALIAS("ip6t_statistic");
  27
  28static bool
  29statistic_mt(const struct sk_buff *skb, struct xt_action_param *par)
  30{
  31        const struct xt_statistic_info *info = par->matchinfo;
  32        bool ret = info->flags & XT_STATISTIC_INVERT;
  33        int nval, oval;
  34
  35        switch (info->mode) {
  36        case XT_STATISTIC_MODE_RANDOM:
  37                if ((prandom_u32() & 0x7FFFFFFF) < info->u.random.probability)
  38                        ret = !ret;
  39                break;
  40        case XT_STATISTIC_MODE_NTH:
  41                do {
  42                        oval = atomic_read(&info->master->count);
  43                        nval = (oval == info->u.nth.every) ? 0 : oval + 1;
  44                } while (atomic_cmpxchg(&info->master->count, oval, nval) != oval);
  45                if (nval == 0)
  46                        ret = !ret;
  47                break;
  48        }
  49
  50        return ret;
  51}
  52
  53static int statistic_mt_check(const struct xt_mtchk_param *par)
  54{
  55        struct xt_statistic_info *info = par->matchinfo;
  56
  57        if (info->mode > XT_STATISTIC_MODE_MAX ||
  58            info->flags & ~XT_STATISTIC_MASK)
  59                return -EINVAL;
  60
  61        info->master = kzalloc(sizeof(*info->master), GFP_KERNEL);
  62        if (info->master == NULL)
  63                return -ENOMEM;
  64        atomic_set(&info->master->count, info->u.nth.count);
  65
  66        return 0;
  67}
  68
  69static void statistic_mt_destroy(const struct xt_mtdtor_param *par)
  70{
  71        const struct xt_statistic_info *info = par->matchinfo;
  72
  73        kfree(info->master);
  74}
  75
  76static struct xt_match xt_statistic_mt_reg __read_mostly = {
  77        .name       = "statistic",
  78        .revision   = 0,
  79        .family     = NFPROTO_UNSPEC,
  80        .match      = statistic_mt,
  81        .checkentry = statistic_mt_check,
  82        .destroy    = statistic_mt_destroy,
  83        .matchsize  = sizeof(struct xt_statistic_info),
  84        .usersize   = offsetof(struct xt_statistic_info, master),
  85        .me         = THIS_MODULE,
  86};
  87
  88static int __init statistic_mt_init(void)
  89{
  90        return xt_register_match(&xt_statistic_mt_reg);
  91}
  92
  93static void __exit statistic_mt_exit(void)
  94{
  95        xt_unregister_match(&xt_statistic_mt_reg);
  96}
  97
  98module_init(statistic_mt_init);
  99module_exit(statistic_mt_exit);
 100