mptcp: add ADD_ADDR related mibs

This patch added two mibs for ADD_ADDR, MPTCP_MIB_ADDADDR for receiving
of the ADD_ADDR suboption with echo-flag=0, and MPTCP_MIB_ECHOADD for
receiving the ADD_ADDR suboption with echo-flag=1.

Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Co-developed-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Geliang Tang <geliangtang@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/mptcp/mib.h b/net/mptcp/mib.h
index 937a177..cdeea37 100644
--- a/net/mptcp/mib.h
+++ b/net/mptcp/mib.h
@@ -20,6 +20,8 @@ enum linux_mptcp_mib_field {
 	MPTCP_MIB_OFOMERGE,		/* Segments merged in OoO queue */
 	MPTCP_MIB_NODSSWINDOW,		/* Segments not in MPTCP windows */
 	MPTCP_MIB_DUPDATA,		/* Segments discarded due to duplicate DSS */
+	MPTCP_MIB_ADDADDR,		/* Received ADD_ADDR with echo-flag=0 */
+	MPTCP_MIB_ECHOADD,		/* Received ADD_ADDR with echo-flag=1 */
 	__MPTCP_MIB_MAX
 };