linux/net/netfilter/xt_quota.c
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   1/*
   2 * netfilter module to enforce network quotas
   3 *
   4 * Sam Johnston <samj@samj.net>
   5 */
   6#include <linux/skbuff.h>
   7#include <linux/slab.h>
   8#include <linux/spinlock.h>
   9
  10#include <linux/netfilter/x_tables.h>
  11#include <linux/netfilter/xt_quota.h>
  12#include <linux/module.h>
  13
  14struct xt_quota_priv {
  15        spinlock_t      lock;
  16        uint64_t        quota;
  17};
  18
  19MODULE_LICENSE("GPL");
  20MODULE_AUTHOR("Sam Johnston <samj@samj.net>");
  21MODULE_DESCRIPTION("Xtables: countdown quota match");
  22MODULE_ALIAS("ipt_quota");
  23MODULE_ALIAS("ip6t_quota");
  24
  25static bool
  26quota_mt(const struct sk_buff *skb, struct xt_action_param *par)
  27{
  28        struct xt_quota_info *q = (void *)par->matchinfo;
  29        struct xt_quota_priv *priv = q->master;
  30        bool ret = q->flags & XT_QUOTA_INVERT;
  31
  32        spin_lock_bh(&priv->lock);
  33        if (priv->quota >= skb->len) {
  34                priv->quota -= skb->len;
  35                ret = !ret;
  36        } else {
  37                /* we do not allow even small packets from now on */
  38                priv->quota = 0;
  39        }
  40        spin_unlock_bh(&priv->lock);
  41
  42        return ret;
  43}
  44
  45static int quota_mt_check(const struct xt_mtchk_param *par)
  46{
  47        struct xt_quota_info *q = par->matchinfo;
  48
  49        if (q->flags & ~XT_QUOTA_MASK)
  50                return -EINVAL;
  51
  52        q->master = kmalloc(sizeof(*q->master), GFP_KERNEL);
  53        if (q->master == NULL)
  54                return -ENOMEM;
  55
  56        spin_lock_init(&q->master->lock);
  57        q->master->quota = q->quota;
  58        return 0;
  59}
  60
  61static void quota_mt_destroy(const struct xt_mtdtor_param *par)
  62{
  63        const struct xt_quota_info *q = par->matchinfo;
  64
  65        kfree(q->master);
  66}
  67
  68static struct xt_match quota_mt_reg __read_mostly = {
  69        .name       = "quota",
  70        .revision   = 0,
  71        .family     = NFPROTO_UNSPEC,
  72        .match      = quota_mt,
  73        .checkentry = quota_mt_check,
  74        .destroy    = quota_mt_destroy,
  75        .matchsize  = sizeof(struct xt_quota_info),
  76        .me         = THIS_MODULE,
  77};
  78
  79static int __init quota_mt_init(void)
  80{
  81        return xt_register_match(&quota_mt_reg);
  82}
  83
  84static void __exit quota_mt_exit(void)
  85{
  86        xt_unregister_match(&quota_mt_reg);
  87}
  88
  89module_init(quota_mt_init);
  90module_exit(quota_mt_exit);
  91
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