net/netfilter/xt_quota.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * netfilter module to enforce network quotas
   4  *
   5  * Sam Johnston <samj@samj.net>
   6  */
   7 #include <linux/skbuff.h>
   8 #include <linux/slab.h>
   9 #include <linux/spinlock.h>
  10
  11 #include <linux/netfilter/x_tables.h>
  12 #include <linux/netfilter/xt_quota.h>
  13 #include <linux/module.h>
  14
  15 struct xt_quota_priv {
  16         spinlock_t      lock;
  17         uint64_t        quota;
  18 };
  19
  20 MODULE_LICENSE("GPL");
  21 MODULE_AUTHOR("Sam Johnston <samj@samj.net>");
  22 MODULE_DESCRIPTION("Xtables: countdown quota match");
  23 MODULE_ALIAS("ipt_quota");
  24 MODULE_ALIAS("ip6t_quota");
  25
  26 static bool
  27 quota_mt(const struct sk_buff *skb, struct xt_action_param *par)
  28 {
  29         struct xt_quota_info *q = (void *)par->matchinfo;
  30         struct xt_quota_priv *priv = q->master;
  31         bool ret = q->flags & XT_QUOTA_INVERT;
  32
  33         spin_lock_bh(&priv->lock);
  34         if (priv->quota >= skb->len) {
  35                 priv->quota -= skb->len;
  36                 ret = !ret;
  37         } else {
  38                 /* we do not allow even small packets from now on */
  39                 priv->quota = 0;
  40         }
  41         spin_unlock_bh(&priv->lock);
  42
  43         return ret;
  44 }
  45
  46 static int quota_mt_check(const struct xt_mtchk_param *par)
  47 {
  48         struct xt_quota_info *q = par->matchinfo;
  49
  50         if (q->flags & ~XT_QUOTA_MASK)
  51                 return -EINVAL;
  52
  53         q->master = kmalloc(sizeof(*q->master), GFP_KERNEL);
  54         if (q->master == NULL)
  55                 return -ENOMEM;
  56
  57         spin_lock_init(&q->master->lock);
  58         q->master->quota = q->quota;
  59         return 0;
  60 }
  61
  62 static void quota_mt_destroy(const struct xt_mtdtor_param *par)
  63 {
  64         const struct xt_quota_info *q = par->matchinfo;
  65
  66         kfree(q->master);
  67 }
  68
  69 static struct xt_match quota_mt_reg __read_mostly = {
  70         .name       = "quota",
  71         .revision   = 0,
  72         .family     = NFPROTO_UNSPEC,
  73         .match      = quota_mt,
  74         .checkentry = quota_mt_check,
  75         .destroy    = quota_mt_destroy,
  76         .matchsize  = sizeof(struct xt_quota_info),
  77         .usersize   = offsetof(struct xt_quota_info, master),
  78         .me         = THIS_MODULE,
  79 };
  80
  81 static int __init quota_mt_init(void)
  82 {
  83         return xt_register_match(&quota_mt_reg);
  84 }
  85
  86 static void __exit quota_mt_exit(void)
  87 {
  88         xt_unregister_match(&quota_mt_reg);
  89 }
  90
  91 module_init(quota_mt_init);
  92 module_exit(quota_mt_exit);