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   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_ALIAS("ipt_quota");
  15 MODULE_ALIAS("ip6t_quota");
  16
  17 static DEFINE_SPINLOCK(quota_lock);
  18
  19 static bool
  20 match(const struct sk_buff *skb,
  21       const struct net_device *in, const struct net_device *out,
  22       const struct xt_match *match, const void *matchinfo,
  23       int offset, unsigned int protoff, bool *hotdrop)
  24 {
  25         struct xt_quota_info *q =
  26                 ((const struct xt_quota_info *)matchinfo)->master;
  27         bool ret = q->flags & XT_QUOTA_INVERT;
  28
  29         spin_lock_bh(&quota_lock);
  30         if (q->quota >= skb->len) {
  31                 q->quota -= skb->len;
  32                 ret = !ret;
  33         } else {
  34                 /* we do not allow even small packets from now on */
  35                 q->quota = 0;
  36         }
  37         spin_unlock_bh(&quota_lock);
  38
  39         return ret;
  40 }
  41
  42 static bool
  43 checkentry(const char *tablename, const void *entry,
  44            const struct xt_match *match, void *matchinfo,
  45            unsigned int hook_mask)
  46 {
  47         struct xt_quota_info *q = matchinfo;
  48
  49         if (q->flags & ~XT_QUOTA_MASK)
  50                 return false;
  51         /* For SMP, we only want to use one set of counters. */
  52         q->master = q;
  53         return true;
  54 }
  55
  56 static struct xt_match xt_quota_match[] = {
  57         {
  58                 .name           = "quota",
  59                 .family         = AF_INET,
  60                 .checkentry     = checkentry,
  61                 .match          = match,
  62                 .matchsize      = sizeof(struct xt_quota_info),
  63                 .me             = THIS_MODULE
  64         },
  65         {
  66                 .name           = "quota",
  67                 .family         = AF_INET6,
  68                 .checkentry     = checkentry,
  69                 .match          = match,
  70                 .matchsize      = sizeof(struct xt_quota_info),
  71                 .me             = THIS_MODULE
  72         },
  73 };
  74
  75 static int __init xt_quota_init(void)
  76 {
  77         return xt_register_matches(xt_quota_match, ARRAY_SIZE(xt_quota_match));
  78 }
  79
  80 static void __exit xt_quota_fini(void)
  81 {
  82         xt_unregister_matches(xt_quota_match, ARRAY_SIZE(xt_quota_match));
  83 }
  84
  85 module_init(xt_quota_init);
  86 module_exit(xt_quota_fini);