{"udp", "golang.org"},
	}
	results := map[[2]string][]IPAddr{
		{"udp", "golang.org"}: {
			{IP: IPv4(127, 0, 0, 1)},
			{IP: IPv6loopback},
		},
		{"udp4", "golang.org"}: {
			{IP: IPv4(127, 0, 0, 1)},
		},
		{"udp6", "golang.org"}: {
			{IP: IPv6loopback},
		},
	}
	calls := int32(0)
	waitCh := make(chan struct{})

		{"tcp4", "127.0.0.1", &TCPAddr{IP: ParseIP("127.0.0.1").To4()}, nil},
		{"tcp4", "127.0.0.1", &TCPAddr{IP: ParseIP("127.0.0.1").To16()}, nil},
		{"tcp4", "127.0.0.1", &TCPAddr{IP: IPv6loopback}, errNoSuitableAddress},
		{"tcp4", "127.0.0.1", &UDPAddr{}, &AddrError{Err: "some error"}},
		{"tcp4", "127.0.0.1", &UnixAddr{}, &AddrError{Err: "some error"}},

		{"tcp6", "::1", nil, nil},

	return nil
}

func newDualStackListener() (lns []*TCPListener, err error) {
	var args = []struct {
		network string
		TCPAddr
	}{
		{"tcp4", TCPAddr{IP: IPv4(127, 0, 0, 1)}},
		{"tcp6", TCPAddr{IP: IPv6loopback}},
	}
	for i := 0; i < 64; i++ {
		var port int
		var lns []*TCPListener
		for _, arg := range args {
			arg.TCPAddr.Port = port
			ln, err := ListenTCP(arg.network, &arg.TCPAddr)
			if err != nil {

)

// Well-known IPv6 addresses
var (
	IPv6zero                   = IP{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
	IPv6unspecified            = IP{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
	IPv6loopback               = IP{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1}
	IPv6interfacelocalallnodes = IP{0xff, 0x01, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x01}

	{IPv4allrouter, true, false},
	{IPv4zero, true, false},
	{IPv4(224, 0, 0, 1), true, false},
	{IPv4(127, 0, 0, 1), true, false},
	{IPv4(240, 0, 0, 1), true, false},
	{IPv6unspecified, false, true},
	{IPv6loopback, false, true},
	{IPv6interfacelocalallnodes, false, true},
	{IPv6linklocalallnodes, false, true},
	{IPv6linklocalallrouters, false, true},
	{ParseIP("ff05::a:b:c:d"), false, true},

					break
				}
			}

			if !found {
				t.Errorf("altNames does not contain DNSName %s", DNSName)
			}
		})
	}

	expectedIPAddresses := []string{"1.2.3.4", "127.0.0.1", net.IPv6loopback.String(), proxyIP}
	for _, IPAddress := range expectedIPAddresses {
		t.Run(IPAddress, func(t *testing.T) {
			found := false
			for _, val := range altNames.IPs {
				if val.Equal(netutils.ParseIPSloppy(IPAddress)) {

		t.Skip("both IPv4 and IPv6 are required")
	}

	for _, tt := range []struct {
		network string
		lit     string
		addr    *TCPAddr
	}{
		{"tcp4", "::1", nil},
		{"tcp4", "", &TCPAddr{IP: IPv6loopback}},
		// We don't test the {"tcp6", "byte sequence", nil}
		// case for now because there is no easy way to
		// control name resolution.
		{"tcp6", "", &TCPAddr{IP: IP{0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef}}},

	}

	// create AltNames with defaults DNSNames/IPs
	altNames := &certutil.AltNames{
		DNSNames: []string{cfg.NodeRegistration.Name, "localhost"},
		IPs:      []net.IP{advertiseAddress, net.IPv4(127, 0, 0, 1), net.IPv6loopback},
	}

	if cfg.Etcd.Local != nil {
		if certName == kubeadmconstants.EtcdServerCertName {
			appendSANsToAltNames(altNames, cfg.Etcd.Local.ServerCertSANs, kubeadmconstants.EtcdServerCertName)

// IPv6LinkLocalAllRouters returns the IPv6 link-local all routers multicast
// address ff02::2.
func IPv6LinkLocalAllRouters() Addr { return AddrFrom16([16]byte{0: 0xff, 1: 0x02, 15: 0x02}) }

// IPv6Loopback returns the IPv6 loopback address ::1.
func IPv6Loopback() Addr { return AddrFrom16([16]byte{15: 0x01}) }

// IPv6Unspecified returns the IPv6 unspecified address "::".
func IPv6Unspecified() Addr { return Addr{z: z6noz} }

	logger := klog.FromContext(ctx)
	primaryFamily := v1.IPv4Protocol
	nodeIPs := map[v1.IPFamily]net.IP{
		v1.IPv4Protocol: net.IPv4(127, 0, 0, 1),
		v1.IPv6Protocol: net.IPv6loopback,
	}

	if len(rawNodeIPs) > 0 {
		if !netutils.IsIPv4(rawNodeIPs[0]) {
			primaryFamily = v1.IPv6Protocol
		}
		nodeIPs[primaryFamily] = rawNodeIPs[0]
		if len(rawNodeIPs) > 1 {