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 #include <linux/module.h>
  13
  14 struct xt_quota_priv {
  15         spinlock_t      lock;
  16         uint64_t        quota;
  17 };
  18
  19 MODULE_LICENSE("GPL");
  20 MODULE_AUTHOR("Sam Johnston <samj@samj.net>");
  21 MODULE_DESCRIPTION("Xtables: countdown quota match");
  22 MODULE_ALIAS("ipt_quota");
  23 MODULE_ALIAS("ip6t_quota");
  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(&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
  45 static 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
  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         .usersize   = offsetof(struct xt_quota_info, master),
  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);