// for loopback test.
func LoopbackInterface() (*net.Interface, error) {
	ift, err := net.Interfaces()
	if err != nil {
		return nil, errNoAvailableInterface
	}
	for _, ifi := range ift {
		if ifi.Flags&net.FlagLoopback != 0 && ifi.Flags&net.FlagUp != 0 {
			return &ifi, nil
		}
	}
	return nil, errNoAvailableInterface
}

// RoutedInterface returns a network interface that can route IP
// traffic and satisfies flags.

`

const (
	flagUp       = net.FlagUp | net.FlagBroadcast | net.FlagMulticast
	flagDown     = net.FlagBroadcast | net.FlagMulticast
	flagLoopback = net.FlagUp | net.FlagLoopback
	flagP2P      = net.FlagUp | net.FlagPointToPoint
)

func makeIntf(index int, name string, flags net.Flags) net.Interface {
	mac := net.HardwareAddr{0, 0x32, 0x7d, 0x69, 0xf7, byte(0x30 + index)}

	checkGetmac(t)

	ift, err := Interfaces()
	if err != nil {
		t.Fatal(err)
	}
	have := make(map[string]string)
	for _, ifi := range ift {
		if ifi.Flags&FlagLoopback != 0 {
			// no MAC address for loopback interfaces
			continue
		}
		have[ifi.Name] = ifi.HardwareAddr.String()
	}

	out, err := runCmd("getmac", "/fo", "list", "/v")
	if err != nil {

		{"ErrWriteToConnected", Var, 0},
		{"Error", Type, 0},
		{"FileConn", Func, 0},
		{"FileListener", Func, 0},
		{"FilePacketConn", Func, 0},
		{"FlagBroadcast", Const, 0},
		{"FlagLoopback", Const, 0},
		{"FlagMulticast", Const, 0},
		{"FlagPointToPoint", Const, 0},
		{"FlagRunning", Const, 20},
		{"FlagUp", Const, 0},
		{"Flags", Type, 0},
		{"HardwareAddr", Type, 0},

pkg mime/multipart, type Part struct, Header textproto.MIMEHeader
pkg mime/multipart, type Reader struct
pkg mime/multipart, type Writer struct
pkg net, const FlagBroadcast Flags
pkg net, const FlagLoopback Flags
pkg net, const FlagMulticast Flags
pkg net, const FlagPointToPoint Flags
pkg net, const FlagUp Flags
pkg net, const IPv4len ideal-int
pkg net, const IPv6len ideal-int

pkg math/big, method (*Rat) Float64() (float64, bool)
pkg math/big, method (*Rat) SetFloat64(float64) *Rat
pkg mime/multipart, method (*Writer) SetBoundary(string) error
pkg net, const FlagBroadcast = 2
pkg net, const FlagLoopback = 4
pkg net, const FlagMulticast = 16
pkg net, const FlagPointToPoint = 8
pkg net, const FlagUp = 1
pkg net, const IPv4len = 4
pkg net, const IPv6len = 16