code: func getPathAttrFlags(typ BGPAttrType, length int) BGPAttrFlag {
  	flags := PathAttrFlags[typ]
  	if length > 255 {
  		flags |= BGP_ATTR_FLAG_EXTENDED_LENGTH
  	}
  	return flags
  }
docs: // getPathAttrFlags returns BGP Path Attribute flags value from its type and
  // length (byte length of value field).