Private/Get-NameserverList.ps1
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function Get-NameServerList { [OutputType([Collections.Generic.List[DnsClient.NameServer]])] [CmdletBinding()] param( [string[]]$NameServer, [switch]$IgnoreActive ) # Since Powershell can't coerce an array of IP addresses into # the IReadonlyCollection[NameServer] list we need for the # QueryServer* methods in LookupClient and we also want to # allow users to use FQDNs for nameservers, we'll do some # extra work here to make things "just work" # Unless called with -IgnoreActive, this method should always # return a valid nameserver list that can be called using # LookupClient.QueryServer* methods. if (-not $NameServer -or $NameServer.Count -eq 0) { if ($IgnoreActive) { Write-Debug "Returning null nameservers" return $null } elseif ($script:ActiveNameServers) { Write-Debug "Returning ActiveNameServers" return ,$script:ActiveNameServers } else { Write-Debug "Returning default nameservers" return ,(Get-LookupClient).NameServers } } $nsList = [Collections.Generic.List[DnsClient.NameServer]]::new() foreach ($val in $NameServer) { # each value here should be an FQDN or IP # optionally followed by a ":PORT" if (-not $val) { Write-Warning "Skipping null nameserver value" continue } # split the nameserver from the port if it exists $nsString, $port = $val.Split(':') if ([String]::IsNullOrWhiteSpace($nsString)) { Write-Warning "Skipping empty nameserver value" continue } # if it's just an IP address, we're done if ($ip = $nsString -as [ipaddress]) { # WARNING: The [ipaddress] conversion will happily accept # integer values and convert them to an IP # (e.g. '1' -as [ipaddress] = 0.0.0.1) # Technically this is a "feature", but may bite people unaware. if ($port -and ($port -as [int]) -gt 0) { $ns = [DnsClient.NameServer]::new($ip, $port) } else { $ns = [DnsClient.NameServer]::new($ip) } $nsList.Add($ns) Write-Debug "Parsed nameserver as $ns" continue } # It's not an IP address, so we'll try and resolve it using the # default system resolver. $response = Resolve-Dns $nsString if ($response.Answers.Count -gt 0) { # If there are multiple answers, we're only going to use the first one # Time will tell if that comes back to bit us. if ($port -and ($port -as [int]) -gt 0) { $ns = [DnsClient.NameServer]::new($response.Answers[0].Address, $port) } else { $ns = [DnsClient.NameServer]::new($response.Answers[0].Address) } $nsList.Add($ns) Write-Debug "Parsed nameserver as $ns" } else { Write-Warning "Unable to resolve nameserver $nsString to an IP address. Skipping." } } # return what we've got if there is anything if ($nsList.Count -gt 0) { Write-Debug "Returning converted nameservers" return ,$nsList } elseif (-not $IgnoreActive) { Write-Debug "Returning default nameservers" return ,(Get-LookupClient).NameServers } else { Write-Debug "Returning null nameservers" return $null } } |