rtnl: add a new type of msg to advertise protocol configuration

A new type is added to allow userland to monitor protocol configuration, like
IPv4 or IPv6.
For example, monitoring the state of the forwarding status of an interface of
the system.

Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/uapi/linux/netconf.h b/include/uapi/linux/netconf.h
new file mode 100644
index 0000000..d051372
--- /dev/null
+++ b/include/uapi/linux/netconf.h
@@ -0,0 +1,22 @@
+#ifndef _UAPI_LINUX_NETCONF_H_
+#define _UAPI_LINUX_NETCONF_H_
+
+#include <linux/types.h>
+#include <linux/netlink.h>
+
+struct netconfmsg {
+	__u8	ncm_family;
+};
+
+enum {
+	NETCONFA_UNSPEC,
+	NETCONFA_IFINDEX,
+	NETCONFA_FORWARDING,
+	__NETCONFA_MAX
+};
+#define NETCONFA_MAX	(__NETCONFA_MAX - 1)
+
+#define NETCONFA_IFINDEX_ALL		-1
+#define NETCONFA_IFINDEX_DEFAULT	-2
+
+#endif /* _UAPI_LINUX_NETCONF_H_ */