req.nh.nlmsg_len = NLMSG_LENGTH(sizeof(req.rt));
req.rt.rtm_family = AF_INET6;
req.rt.rtm_dst_len = prefixlen;
req.rt.rtm_table = RT_TABLE_MAIN;
req.nh.nlmsg_len = NLMSG_LENGTH(sizeof(req.rt));
req.rt.rtm_family = AF_INET6;
req.rt.rtm_dst_len = prefixlen;
req.rt.rtm_table = RT_TABLE_MAIN;