}

func TestProhibitionaryDialArg(t *testing.T) {
	testenv.MustHaveExternalNetwork(t)

	switch runtime.GOOS {
	case "plan9":
		t.Skipf("not supported on %s", runtime.GOOS)
	}
	if !supportsIPv4map() {
		t.Skip("mapping ipv4 address inside ipv6 address not supported")
	}

	ln, err := Listen("tcp", "[::]:0")
	if err != nil {
		t.Fatal(err)
	}
	defer ln.Close()