XTLS/Xray-core · error

outbound interface cannot be the TUN interface

Error message

outbound interface cannot be the TUN interface

What it means

Error "outbound interface cannot be the TUN interface" thrown in XTLS/Xray-core.

Source

Thrown at proxy/tun/tun_darwin.go:488

		err1 = unix.SetsockoptInt(int(fd), unix.IPPROTO_IPV6, unix.IPV6_BOUND_IF, iface.Index)
		fallthrough
	case "tcp4", "udp4", "ip4":
		err2 = unix.SetsockoptInt(int(fd), unix.IPPROTO_IP, unix.IP_BOUND_IF, iface.Index)
	default:
		panic(network + " " + address)
	}

	return errors.Join(err1, err2)
}

func findOutboundInterface(tunIndex int, fixedName string) (*net.Interface, error) {
	if fixedName != "" {
		iface, err := net.InterfaceByName(fixedName)
		if err != nil {
			return nil, err
		}
		if iface.Index == tunIndex {
			return nil, errors.New("outbound interface cannot be the TUN interface")
		}
		return iface, nil
	}

	rib, err := route.FetchRIB(unix.AF_UNSPEC, route.RIBTypeRoute, 0)
	if err != nil {
		return nil, err
	}
	messages, err := route.ParseRIB(route.RIBTypeRoute, rib)
	if err != nil {
		return nil, err
	}

	var ipv6Index int
	for _, message := range messages {
		routeMessage, ok := message.(*route.RouteMessage)
		if !ok || routeMessage.Index == tunIndex {
			continue

View on GitHub (pinned to 7d214f8b09)

When it happens

Trigger: Thrown at proxy/tun/tun_darwin.go:488 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of XTLS/Xray-core@7d214f8b09 (2026-08-15). Data as JSON: /api/errors/512b9ee8a2842620. Report an issue: GitHub.