return listen("tcp6", "[::1]:0")
		}
	case "unix", "unixpacket":
		return listen(network, testUnixAddr(t))
	}

	t.Helper()
	t.Fatalf("%s is not supported", network)
	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++ {