"AddrPort.Port",
		"AddrPort.IsValid",
		"Prefix.IsSingleIP",
		"Prefix.Masked",
		"Prefix.IsValid",
		"PrefixFrom",
		"Prefix.Addr",
		"Prefix.Bits",
		"AddrFrom4",
		"IPv6LinkLocalAllNodes",
		"IPv6Unspecified",
		"MustParseAddr",
		"MustParseAddrPort",
		"MustParsePrefix",
		"appendDecimal",
		"appendHex",
		"uint128.addOne",
		"uint128.and",
		"uint128.bitsClearedFrom",
		"uint128.bitsSetFrom",

		resolveTCPAddrTests = append(resolveTCPAddrTests, resolveTCPAddrTest{"tcp", "[::]:4", &TCPAddr{IP: IPv6unspecified, Port: 4}, nil})
		resolveUDPAddrTests = append(resolveUDPAddrTests, resolveUDPAddrTest{"udp", "[::]:4", &UDPAddr{IP: IPv6unspecified, Port: 4}, nil})
		resolveIPAddrTests = append(resolveIPAddrTests, resolveIPAddrTest{"ip", "::", &IPAddr{IP: IPv6unspecified}, nil})
	}

	ifi := loopbackInterface()
	if ifi != nil {

	if err != nil {
		return nil, err
	}
	// Issue 18806: if the machine has halfway configured
	// IPv6 such that it can bind on "::" (IPv6unspecified)
	// but not connect back to that same address, fall
	// back to dialing 0.0.0.0.
	if len(ips) == 1 && ips[0].IP.Equal(IPv6unspecified) {
		ips = append(ips, IPAddr{IP: IPv4zero})
	}

	var filter func(IPAddr) bool
	if net != "" && net[len(net)-1] == '4' {

			std:  net.IPv6linklocalallrouters,
		},
		{
			name: "IPv6 loopback",
			ip:   IPv6Loopback(),
			std:  net.IPv6loopback,
		},
		{
			name: "IPv6 unspecified",
			ip:   IPv6Unspecified(),
			std:  net.IPv6unspecified,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			want := tt.std.String()
			got := tt.ip.String()

			if got != want {

	IPv4zero      = IPv4(0, 0, 0, 0)         // all zeros
)

// 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}

// 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} }

// IPv4Unspecified returns the IPv4 unspecified address "0.0.0.0".
func IPv4Unspecified() Addr { return AddrFrom4([4]byte{}) }

		{"IPv4zero", Var, 0},
		{"IPv6interfacelocalallnodes", Var, 0},
		{"IPv6len", Const, 0},
		{"IPv6linklocalallnodes", Var, 0},
		{"IPv6linklocalallrouters", Var, 0},
		{"IPv6loopback", Var, 0},
		{"IPv6unspecified", Var, 0},
		{"IPv6zero", Var, 0},
		{"Interface", Type, 0},
		{"Interface.Flags", Field, 0},
		{"Interface.HardwareAddr", Field, 0},
		{"Interface.Index", Field, 0},
		{"Interface.MTU", Field, 0},