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