HDLC_MAX_MRU       18 include/uapi/linux/hdlc.h #define HDLC_MAX_MRU (HDLC_MAX_MTU + 10 + 14 + 4) /* for ETH+VLAN over FR */
HDLC_MAX_MRU       20 include/uapi/linux/hdlc.h #define HDLC_MAX_MRU 1600 /* as required for FR network */