create ikuai dm message

def create_dm_pkg(secret,username):
    ''' create ikuai dm message'''
    secret = tools.EncodeString(secret)
    username = tools.EncodeString(username)
    pkg_format = '>HHHH32sHH32s'
    pkg_vals = [
        IK_RAD_PKG_VER,
        IK_RAD_PKG_AUTH,
        IK_RAD_PKG_USR_PWD_TAG,
        len(secret),
        secret.ljust(32,'\x00'),
        IK_RAD_PKG_CMD_ARGS_TAG,
        len(username),
        username.ljust(32,'\x00')
    ]
    return struct.pack(pkg_format,*pkg_vals)