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/spinlock.h>
   8
   9 #include <linux/netfilter/x_tables.h>
  10 #include <linux/netfilter/xt_quota.h>
  11
  12 struct xt_quota_priv {
  13         uint64_t quota;
  14 };
  15
  16 MODULE_LICENSE("GPL");
  17 MODULE_AUTHOR("Sam Johnston <samj@samj.net>");
  18 MODULE_DESCRIPTION("Xtables: countdown quota match");
  19 MODULE_ALIAS("ipt_quota");
  20 MODULE_ALIAS("ip6t_quota");
  21
  22 static DEFINE_SPINLOCK(quota_lock);
  23
  24 static bool
  25 quota_mt(const struct sk_buff *skb, const struct xt_match_param *par)
  26 {
  27         struct xt_quota_info *q = (void *)par->matchinfo;
  28         struct xt_quota_priv *priv = q->master;
  29         bool ret = q->flags & XT_QUOTA_INVERT;
  30
  31         spin_lock_bh(&quota_lock);
  32         if (priv->quota >= skb->len) {
  33                 priv->quota -= skb->len;
  34                 ret = !ret;
  35         } else {
  36                 /* we do not allow even small packets from now on */
  37                 priv->quota = 0;
  38         }
  39         /* Copy quota back to matchinfo so that iptables can display it */
  40         q->quota = priv->quota;
  41         spin_unlock_bh(&quota_lock);
  42
  43         return ret;
  44 }
  45
  46 static bool 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 false;
  52
  53         q->master = kmalloc(sizeof(*q->master), GFP_KERNEL);
  54         if (q->master == NULL)
  55                 return false;
  56
  57         q->master->quota = q->quota;
  58         return true;
  59 }
  60
  61 static 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
  68 static 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
  79 static int __init quota_mt_init(void)
  80 {
  81         return xt_register_match(&quota_mt_reg);
  82 }
  83
  84 static void __exit quota_mt_exit(void)
  85 {
  86         xt_unregister_match(&quota_mt_reg);
  87 }
  88
  89 module_init(quota_mt_init);
  90 module_exit(quota_mt_exit);