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 net_device *in,
  22          const struct net_device *out, const struct xt_match *match,
  23          const void *matchinfo, int offset, unsigned int protoff,
  24          bool *hotdrop)
  25 {
  26         struct xt_quota_info *q =
  27                 ((const struct xt_quota_info *)matchinfo)->master;
  28         bool ret = q->flags & XT_QUOTA_INVERT;
  29
  30         spin_lock_bh(&quota_lock);
  31         if (q->quota >= skb->len) {
  32                 q->quota -= skb->len;
  33                 ret = !ret;
  34         } else {
  35                 /* we do not allow even small packets from now on */
  36                 q->quota = 0;
  37         }
  38         spin_unlock_bh(&quota_lock);
  39
  40         return ret;
  41 }
  42
  43 static bool
  44 quota_mt_check(const char *tablename, const void *entry,
  45                const struct xt_match *match, void *matchinfo,
  46                unsigned int hook_mask)
  47 {
  48         struct xt_quota_info *q = matchinfo;
  49
  50         if (q->flags & ~XT_QUOTA_MASK)
  51                 return false;
  52         /* For SMP, we only want to use one set of counters. */
  53         q->master = q;
  54         return true;
  55 }
  56
  57 static struct xt_match quota_mt_reg[] __read_mostly = {
  58         {
  59                 .name           = "quota",
  60                 .family         = AF_INET,
  61                 .checkentry     = quota_mt_check,
  62                 .match          = quota_mt,
  63                 .matchsize      = sizeof(struct xt_quota_info),
  64                 .me             = THIS_MODULE
  65         },
  66         {
  67                 .name           = "quota",
  68                 .family         = AF_INET6,
  69                 .checkentry     = quota_mt_check,
  70                 .match          = quota_mt,
  71                 .matchsize      = sizeof(struct xt_quota_info),
  72                 .me             = THIS_MODULE
  73         },
  74 };
  75
  76 static int __init quota_mt_init(void)
  77 {
  78         return xt_register_matches(quota_mt_reg, ARRAY_SIZE(quota_mt_reg));
  79 }
  80
  81 static void __exit quota_mt_exit(void)
  82 {
  83         xt_unregister_matches(quota_mt_reg, ARRAY_SIZE(quota_mt_reg));
  84 }
  85
  86 module_init(quota_mt_init);
  87 module_exit(quota_mt_exit);