net/netfilter/xt_quota.c

   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
  13 struct xt_quota_priv {
  14         uint64_t quota;
  15 };
  16
  17 MODULE_LICENSE("GPL");
  18 MODULE_AUTHOR("Sam Johnston <samj@samj.net>");
  19 MODULE_DESCRIPTION("Xtables: countdown quota match");
  20 MODULE_ALIAS("ipt_quota");
  21 MODULE_ALIAS("ip6t_quota");
  22
  23 static DEFINE_SPINLOCK(quota_lock);
  24
  25 static bool
  26 quota_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(&quota_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         /* Copy quota back to matchinfo so that iptables can display it */
  41         q->quota = priv->quota;
  42         spin_unlock_bh(&quota_lock);
  43
  44         return ret;
  45 }
  46
  47 static int quota_mt_check(const struct xt_mtchk_param *par)
  48 {
  49         struct xt_quota_info *q = par->matchinfo;
  50
  51         if (q->flags & ~XT_QUOTA_MASK)
  52                 return -EINVAL;
  53
  54         q->master = kmalloc(sizeof(*q->master), GFP_KERNEL);
  55         if (q->master == NULL)
  56                 return -ENOMEM;
  57
  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         .me         = THIS_MODULE,
  78 };
  79
  80 static int __init quota_mt_init(void)
  81 {
  82         return xt_register_match(&quota_mt_reg);
  83 }
  84
  85 static void __exit quota_mt_exit(void)
  86 {
  87         xt_unregister_match(&quota_mt_reg);
  88 }
  89
  90 module_init(quota_mt_init);
  91 module_exit(quota_mt_exit);