netfilter: nfnetlink_acct: Adding quota support to accounting framework

nfacct objects already support accounting at the byte and packet
level.  As such it is a natural extension to add the possiblity to
define a ceiling limit for both metrics.

All the support for quotas itself is added to nfnetlink acctounting
framework to stay coherent with current accounting object management.
Quota limit checks are implemented in xt_nfacct filter where
statistic collection is already done.

Pablo Neira Ayuso has also contributed to this feature.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/linux/netfilter/nfnetlink_acct.h

@@ -3,11 +3,17 @@
 
 #include <uapi/linux/netfilter/nfnetlink_acct.h>
 
+enum {
+	NFACCT_NO_QUOTA		= -1,
+	NFACCT_UNDERQUOTA,
+	NFACCT_OVERQUOTA,
+};
 
 struct nf_acct;
 
 struct nf_acct *nfnl_acct_find_get(const char *filter_name);
 void nfnl_acct_put(struct nf_acct *acct);
 void nfnl_acct_update(const struct sk_buff *skb, struct nf_acct *nfacct);
-
+extern int nfnl_acct_overquota(const struct sk_buff *skb,
+			      struct nf_acct *nfacct);
 #endif /* _NFNL_ACCT_H */