[]IPAddr{
			{IP: IPv6loopback},
			{IP: ParseIP("fe80::1"), Zone: "eth0"},
		},
		testInetaddr,
		&TCPAddr{IP: IPv6loopback, Port: 5682},
		addrList{
			&TCPAddr{IP: IPv6loopback, Port: 5682},
			&TCPAddr{IP: ParseIP("fe80::1"), Port: 5682, Zone: "eth0"},
		},
		nil,
		nil,
	},
	{
		nil,
		[]IPAddr{
			{IP: IPv4(127, 0, 0, 1)},
			{IP: IPv4(192, 168, 0, 1)},
			{IP: IPv6loopback},

		resolveUDPAddrTests = append(resolveUDPAddrTests, resolveUDPAddrTest{"udp6", "localhost:3", &UDPAddr{IP: IPv6loopback, Port: 3}, nil})
		resolveIPAddrTests = append(resolveIPAddrTests, resolveIPAddrTest{"ip6", "localhost", &IPAddr{IP: IPv6loopback}, nil})

		// Issue 20911: don't return IPv4 addresses for

		}
	}

	var isloopback bool
	switch ra := ra.(type) {
	case *syscall.SockaddrInet4:
		isloopback = ra.Addr[0] == 127
	case *syscall.SockaddrInet6:
		isloopback = ra.Addr == [16]byte(IPv6loopback)
	default:
		panic("unexpected type in connect")
	}
	if isloopback {
		// This makes ConnectEx() fails faster if the target port on the localhost
		// is not reachable, instead of waiting for 2s.

//
// Do not remove or change the type signature.
// See go.dev/issue/67401.
//
//go:linkname loopbackIP
func loopbackIP(net string) IP {
	if net != "" && net[len(net)-1] == '6' {
		return IPv6loopback
	}
	return IP{127, 0, 0, 1}