winutil/functions/private/Set-WinUtilDNS.ps1

function Set-WinUtilDNS {
    <#

    .SYNOPSIS
        Sets the DNS of all interfaces that are in the "Up" state. It will lookup the values from the DNS.Json file

    .PARAMETER DNSProvider
        The DNS provider to set the DNS server to

    .EXAMPLE
        Set-WinUtilDNS -DNSProvider "google"

    #>
    param($DNSProvider)

    if($DNSProvider -eq "Default") {
        Write-WinUtilLog -Component "DNS" -Message "DNS provider is Default; no DNS changes applied."
        return
    }

    try {
        $Adapters = Get-NetAdapter | Where-Object {$_.Status -eq "Up"}
        Write-Host "Ensuring DNS is set to $DNSProvider on the following interfaces:"
        Write-Host $($Adapters | Out-String)
        Write-WinUtilLog -Component "DNS" -Message "Setting DNS provider to $DNSProvider for $(@($Adapters).Count) active adapter(s)."

        if($DNSProvider -ne "DHCP") {
            $dns = $sync.configs.dns.$DNSProvider
            if($null -eq $dns) {
                Write-Warning "DNS provider $DNSProvider was not found in configuration."
                Write-WinUtilLog -Level "ERROR" -Component "DNS" -Message "DNS provider $DNSProvider was not found in configuration."
                return
            }
        }

        $dohSupported = [bool](Get-Command Add-DnsClientDohServerAddress -ErrorAction SilentlyContinue)
        $dnscacheBase = "HKLM:\System\CurrentControlSet\Services\Dnscache\InterfaceSpecificParameters"

        Foreach ($Adapter in $Adapters) {
            $interfaceParams = "$dnscacheBase\$($Adapter.InterfaceGuid)"

            if($DNSProvider -eq "DHCP") {
                Write-WinUtilLog -Component "DNS" -Message "Resetting DNS to DHCP on adapter $($Adapter.Name) (ifIndex: $($Adapter.ifIndex))."
                Set-DnsClientServerAddress -InterfaceIndex $Adapter.ifIndex -ResetServerAddresses
                netsh interface ip set dnsservers name="$($Adapter.Name)" source=dhcp
                netsh interface ipv6 set dnsservers name="$($Adapter.Name)" source=dhcp

                $dohInterfaceSettings = "$interfaceParams\DohInterfaceSettings"
                if (Test-Path $dohInterfaceSettings) {
                    if ($dohSupported) {
                        $dohServerAddresses = @(
                            Get-ChildItem -Path "$dohInterfaceSettings\Doh" -ErrorAction SilentlyContinue
                            Get-ChildItem -Path "$dohInterfaceSettings\Doh6" -ErrorAction SilentlyContinue
                        ) | Select-Object -ExpandProperty PSChildName -Unique

                        foreach ($ip in $dohServerAddresses) {
                            if (Get-DnsClientDohServerAddress -ServerAddress $ip -ErrorAction SilentlyContinue) {
                                Write-WinUtilLog -Component "DNS" -Message "Removing DoH registration for $ip."
                                Remove-DnsClientDohServerAddress -ServerAddress $ip -Confirm:$false -ErrorAction Stop
                            }
                        }
                    }

                    Remove-Item -Path $dohInterfaceSettings -Recurse -Force -ErrorAction SilentlyContinue
                }
            } else {
                Write-WinUtilLog -Component "DNS" -Message "Setting IPv4 DNS on adapter $($Adapter.Name) (ifIndex: $($Adapter.ifIndex)) to $($dns.Primary), $($dns.Secondary)."
                Set-DnsClientServerAddress -InterfaceIndex $Adapter.ifIndex -ServerAddresses ($dns.Primary, $dns.Secondary)
                Write-WinUtilLog -Component "DNS" -Message "Setting IPv6 DNS on adapter $($Adapter.Name) (ifIndex: $($Adapter.ifIndex)) to $($dns.Primary6), $($dns.Secondary6)."
                Set-DnsClientServerAddress -InterfaceIndex $Adapter.ifIndex -ServerAddresses ($dns.Primary6, $dns.Secondary6)

                if ($dohSupported -and $dns.DohTemplate) {
                    $ips = @($dns.Primary, $dns.Secondary, $dns.Primary6, $dns.Secondary6) | Where-Object { $_ }
                    foreach ($ip in $ips) {
                        $existing = Get-DnsClientDohServerAddress -ServerAddress $ip -ErrorAction SilentlyContinue
                        if ($existing) {
                            Set-DnsClientDohServerAddress -ServerAddress $ip -DohTemplate $dns.DohTemplate -AllowFallbackToUdp $false -AutoUpgrade $true -ErrorAction Stop
                        } else {
                            Write-WinUtilLog -Component "DNS" -Message "Registering DoH template for $ip."
                            Add-DnsClientDohServerAddress -ServerAddress $ip -DohTemplate $dns.DohTemplate -AllowFallbackToUdp $false -AutoUpgrade $true -ErrorAction Stop
                        }
                        
                        $leaf = if ($ip.Contains(':')) { 'Doh6' } else { 'Doh' }
                        $regPath = "$interfaceParams\DohInterfaceSettings\$leaf\$ip"
                        
                        if (-not (Test-Path $regPath)) {
                            New-Item -Path $regPath -Force -ErrorAction Stop | Out-Null
                        }
                        New-ItemProperty -Path $regPath -Name "DohFlags" -Value 1 -PropertyType QWord -Force -ErrorAction Stop | Out-Null
                    }
                }
            }
        }
        if ($DNSProvider -ne "DHCP" -and $dohSupported -and $dns.DohTemplate) {
            Clear-DnsClientCache
        }
        Write-WinUtilLog -Component "DNS" -Message "DNS provider change completed: $DNSProvider"
    } catch {
        Write-Warning "DNS provider $DNSProvider was not completed because an error occurred."
        Write-Warning $psitem.Exception.Message
        Write-WinUtilLog -Level "ERROR" -Component "DNS" -Message "DNS provider $DNSProvider was not completed: $($psitem.Exception.Message)"
    }
}