git.rot13.org Git - linux/blob - 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 MODULE_LICENSE("GPL");
  15 MODULE_AUTHOR("Sam Johnston <samj@samj.net>");
  16 MODULE_DESCRIPTION("Xtables: countdown quota match");
  17 MODULE_ALIAS("ipt_quota");
  18 MODULE_ALIAS("ip6t_quota");
  19
  20 static bool
  21 quota_mt(const struct sk_buff *skb, struct xt_action_param *par)
  22 {
  23         struct xt_quota_info *q = (void *)par->matchinfo;
  24         u64 current_count = atomic64_read(&q->counter);
  25         bool ret = q->flags & XT_QUOTA_INVERT;
  26         u64 old_count, new_count;
  27
  28         do {
  29                 if (current_count == 1)
  30                         return ret;
  31                 if (current_count <= skb->len) {
  32                         atomic64_set(&q->counter, 1);
  33                         return ret;
  34                 }
  35                 old_count = current_count;
  36                 new_count = current_count - skb->len;
  37                 current_count = atomic64_cmpxchg(&q->counter, old_count,
  38                                                  new_count);
  39         } while (current_count != old_count);
  40         return !ret;
  41 }
  42
  43 static int quota_mt_check(const struct xt_mtchk_param *par)
  44 {
  45         struct xt_quota_info *q = par->matchinfo;
  46
  47         BUILD_BUG_ON(sizeof(atomic64_t) != sizeof(__u64));
  48
  49         if (q->flags & ~XT_QUOTA_MASK)
  50                 return -EINVAL;
  51         if (atomic64_read(&q->counter) > q->quota + 1)
  52                 return -ERANGE;
  53
  54         if (atomic64_read(&q->counter) == 0)
  55                 atomic64_set(&q->counter, q->quota + 1);
  56         return 0;
  57 }
  58
  59 static struct xt_match quota_mt_reg __read_mostly = {
  60         .name       = "quota",
  61         .revision   = 0,
  62         .family     = NFPROTO_UNSPEC,
  63         .match      = quota_mt,
  64         .checkentry = quota_mt_check,
  65         .matchsize  = sizeof(struct xt_quota_info),
  66         .me         = THIS_MODULE,
  67 };
  68
  69 static int __init quota_mt_init(void)
  70 {
  71         return xt_register_match(&quota_mt_reg);
  72 }
  73
  74 static void __exit quota_mt_exit(void)
  75 {
  76         xt_unregister_match(&quota_mt_reg);
  77 }
  78
  79 module_init(quota_mt_init);
  80 module_exit(quota_mt_exit);