temp2

// true: up, not loopback func judgeNic(intf net.Interface) bool { return (intf.Flags&net.FlagUp != 0) && // Mao: not reliable. it is administrative state, not running state. 2022.06.21 // a chance for golang contribution (intf.Flags&net.FlagLoopback == 0) }

func judgeIPv6(ip *net.IP) bool { return ip.To4() == nil }

// Get GUA, ULA // not loopback, link-local func getIPv6AddressGuaUla() (addresses []string) { result := []string{}

intfs, err := net.Interfaces()
if err != nil {
	log.Printf("Fail to get Interfaces, %s\n", err.Error())
	return result
}
for _, intf := range intfs {
	log.Printf("NIC name: %s, flags: %s\n", intf.Name, intf.Flags)
	if judgeNic(intf) {
		addrs, err := intf.Addrs()
		if err != nil {
			log.Printf("Fail to get Addrs, %s\n", err.Error())
			continue
		}
		for _, addr := range addrs {
			if ip, ok := addr.(*net.IPNet); ok {
				if judgeIPv6(&ip.IP) && (ip.IP.IsGlobalUnicast() || ip.IP.IsPrivate()) { // allow GUA, ULA
					result = append(result, ip.IP.String())
				} else {
					//log.Println("Filtered: ", ip.IP.String())
				}
			}
		}
	}
}
log.Println("Available IPv6 addresses: ", result)
return result

}