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 MODULE_LICENSE("GPL");
  13 MODULE_AUTHOR("Sam Johnston <samj@samj.net>");
  14 MODULE_DESCRIPTION("Xtables: countdown quota match");
  15 MODULE_ALIAS("ipt_quota");
  16 MODULE_ALIAS("ip6t_quota");
  17
  18 static DEFINE_SPINLOCK(quota_lock);
  19
  20 static bool
  21 quota_mt(const struct sk_buff *skb, const struct xt_match_param *par)
  22 {
  23         struct xt_quota_info *q =
  24                 ((const struct xt_quota_info *)par->matchinfo)->master;
  25         bool ret = q->flags & XT_QUOTA_INVERT;
  26
  27         spin_lock_bh(&quota_lock);
  28         if (q->quota >= skb->len) {
  29                 q->quota -= skb->len;
  30                 ret = !ret;
  31         } else {
  32                 /* we do not allow even small packets from now on */
  33                 q->quota = 0;
  34         }
  35         spin_unlock_bh(&quota_lock);
  36
  37         return ret;
  38 }
  39
  40 static bool
  41 quota_mt_check(const char *tablename, const void *entry,
  42                const struct xt_match *match, void *matchinfo,
  43                unsigned int hook_mask)
  44 {
  45         struct xt_quota_info *q = matchinfo;
  46
  47         if (q->flags & ~XT_QUOTA_MASK)
  48                 return false;
  49         /* For SMP, we only want to use one set of counters. */
  50         q->master = q;
  51         return true;
  52 }
  53
  54 static struct xt_match quota_mt_reg __read_mostly = {
  55         .name       = "quota",
  56         .revision   = 0,
  57         .family     = NFPROTO_UNSPEC,
  58         .match      = quota_mt,
  59         .checkentry = quota_mt_check,
  60         .matchsize  = sizeof(struct xt_quota_info),
  61         .me         = THIS_MODULE,
  62 };
  63
  64 static int __init quota_mt_init(void)
  65 {
  66         return xt_register_match(&quota_mt_reg);
  67 }
  68
  69 static void __exit quota_mt_exit(void)
  70 {
  71         xt_unregister_match(&quota_mt_reg);
  72 }
  73
  74 module_init(quota_mt_init);
  75 module_exit(quota_mt_exit);