netfilter: nf_conntrack: add generic function to get len of generic policy

Usefull for all protocols which do not add additional data, such
as GRE or UDPlite.
Signed-off-by: Holger Eitzenberger <holger@eitzenberger.org>
Signed-off-by: Patrick McHardy <kaber@trash.net>

include/net/netfilter/nf_conntrack_l4proto.h

@@ -113,6 +113,7 @@ extern int nf_ct_port_tuple_to_nlattr(struct sk_buff *skb,
 				      const struct nf_conntrack_tuple *tuple);
 extern int nf_ct_port_nlattr_to_tuple(struct nlattr *tb[],
 				      struct nf_conntrack_tuple *t);
+extern int nf_ct_port_nlattr_tuple_size(void);
 extern const struct nla_policy nf_ct_port_nla_policy[];
 
 #ifdef CONFIG_SYSCTL

net/netfilter/nf_conntrack_core.c

@@ -921,6 +921,12 @@ int nf_ct_port_nlattr_to_tuple(struct nlattr *tb[],
 	return 0;
 }
 EXPORT_SYMBOL_GPL(nf_ct_port_nlattr_to_tuple);
+
+int nf_ct_port_nlattr_tuple_size(void)
+{
+	return nla_policy_len(nf_ct_port_nla_policy, CTA_PROTO_MAX + 1);
+}
+EXPORT_SYMBOL_GPL(nf_ct_port_nlattr_tuple_size);
 #endif
 
 /* Used by ipt_REJECT and ip6t_REJECT. */