Fix DHCP DNS reset handling (#4800)

AGENTS.md

@@ -190,3 +190,4 @@ When the user corrects an agent approach, add or tighten one concrete rule here
 - Log install/uninstall package names and package-manager IDs before queuing background runspace work; do not rely on runspace host output for the package identity.
 - For Win11 Creator, start each new ISO modification in a fresh `WinUtil_Win11ISO_*` temp directory; existing-work detection is only for resuming/exporting already modified media.
 - For Script Analyzer cleanup, fix actionable source warnings first and do not globally suppress accepted convention warnings such as plural names, `ShouldProcess` on UI helpers, `$global:sync`, or compile-time cross-file false positives.
+- For DNS DHCP reset, keep the cmdlet reset and explicitly set IPv4 and IPv6 DNS source to DHCP.

functions/private/Set-WinUtilDNS.ps1

@@ -12,25 +12,38 @@ function Set-WinUtilDNS {
 
     #>
     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 $DNSProvider was not found in configuration."
+                return
+            }
+        }
+
         Foreach ($Adapter in $Adapters) {
             if($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
             } else {
-                Write-WinUtilLog -Component "DNS" -Message "Setting IPv4 DNS on adapter $($Adapter.Name) (ifIndex: $($Adapter.ifIndex)) to $($sync.configs.dns.$DNSProvider.Primary), $($sync.configs.dns.$DNSProvider.Secondary)."
+                Write-WinUtilLog -Component "DNS" -Message "Setting IPv4 DNS on adapter $($Adapter.Name) (ifIndex: $($Adapter.ifIndex)) to $($dns.Primary), $($dns.Secondary)."
-                Set-DnsClientServerAddress -InterfaceIndex $Adapter.ifIndex -ServerAddresses ("$($sync.configs.dns.$DNSProvider.Primary)", "$($sync.configs.dns.$DNSProvider.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 $($sync.configs.dns.$DNSProvider.Primary6), $($sync.configs.dns.$DNSProvider.Secondary6)."
+                Write-WinUtilLog -Component "DNS" -Message "Setting IPv6 DNS on adapter $($Adapter.Name) (ifIndex: $($Adapter.ifIndex)) to $($dns.Primary6), $($dns.Secondary6)."
-                Set-DnsClientServerAddress -InterfaceIndex $Adapter.ifIndex -ServerAddresses ("$($sync.configs.dns.$DNSProvider.Primary6)", "$($sync.configs.dns.$DNSProvider.Secondary6)")
+                Set-DnsClientServerAddress -InterfaceIndex $Adapter.ifIndex -ServerAddresses ($dns.Primary6, $dns.Secondary6)
             }
         }
         Write-WinUtilLog -Component "DNS" -Message "DNS provider change completed: $DNSProvider"

functions/public/Invoke-WPFtweaksbutton.ps1

@@ -70,7 +70,9 @@ function Invoke-WPFtweaksbutton {
       }
     }
 
-    Set-WinUtilDNS -DNSProvider $dnsProvider
+    if ($dnsProvider -ne "Default") {
+      Set-WinUtilDNS -DNSProvider $dnsProvider
+    }
 
     for ($i = 0; $i -lt $tweaks.Count; $i++) {
       Set-WinUtilProgressBar -Label "Applying $($tweaks[$i])" -Percent ($completedSteps / $totalSteps * 100)

pester/dns.Tests.ps1

@@ -0,0 +1,118 @@
+#===========================================================================
+# Tests - DNS
+#===========================================================================
+
+BeforeAll {
+    $script:repoRoot = (Resolve-Path (Join-Path $PSScriptRoot "..")).Path
+
+    function Get-NetAdapter { }
+    function Set-DnsClientServerAddress {
+        param(
+            $InterfaceIndex,
+            $ServerAddresses,
+            [switch]$ResetServerAddresses
+        )
+    }
+    function netsh {
+        param(
+            [Parameter(ValueFromRemainingArguments = $true)]
+            [string[]]$Arguments
+        )
+    }
+    function Write-WinUtilLog {
+        param($Message, $Level, $Component)
+    }
+
+    . (Join-Path $script:repoRoot "functions\private\Set-WinUtilDNS.ps1")
+}
+
+Describe "Set-WinUtilDNS" {
+    BeforeEach {
+        $script:sync = [Hashtable]::Synchronized(@{
+            configs = @{
+                dns = @{
+                    Cloudflare = [pscustomobject]@{
+                        Primary = "1.1.1.1"
+                        Secondary = "1.0.0.1"
+                        Primary6 = "2606:4700:4700::1111"
+                        Secondary6 = "2606:4700:4700::1001"
+                    }
+                }
+            }
+        })
+
+        Mock Get-NetAdapter {
+            [pscustomobject]@{
+                Name = "Ethernet"
+                Status = "Up"
+                ifIndex = 7
+            }
+        }
+        Mock Set-DnsClientServerAddress { }
+        Mock netsh { }
+        Mock Write-WinUtilLog { }
+        Mock Write-Warning { }
+        Mock Write-Host { }
+    }
+
+    AfterEach {
+        Remove-Variable -Name sync -Scope Script -ErrorAction SilentlyContinue
+    }
+
+    It "sets IPv4 and IPv6 DNS server addresses separately" {
+        Set-WinUtilDNS -DNSProvider "Cloudflare"
+
+        Should -Invoke -CommandName Set-DnsClientServerAddress -Times 1 -Exactly -ParameterFilter {
+            $InterfaceIndex -eq 7 -and
+                $ServerAddresses.Count -eq 2 -and
+                $ServerAddresses[0] -eq "1.1.1.1" -and
+                $ServerAddresses[1] -eq "1.0.0.1"
+        }
+        Should -Invoke -CommandName Set-DnsClientServerAddress -Times 1 -Exactly -ParameterFilter {
+            $InterfaceIndex -eq 7 -and
+                $ServerAddresses.Count -eq 2 -and
+                $ServerAddresses[0] -eq "2606:4700:4700::1111" -and
+                $ServerAddresses[1] -eq "2606:4700:4700::1001"
+        }
+        Should -Invoke -CommandName Set-DnsClientServerAddress -Times 0 -Exactly -ParameterFilter {
+            $ServerAddresses.Count -eq 4
+        }
+    }
+
+    It "resets DNS to DHCP for IPv4 and IPv6" {
+        Set-WinUtilDNS -DNSProvider "DHCP"
+
+        Should -Invoke -CommandName Set-DnsClientServerAddress -Times 1 -Exactly -ParameterFilter {
+            $InterfaceIndex -eq 7 -and
+                $ResetServerAddresses -eq $true
+        }
+        Should -Invoke -CommandName netsh -Times 1 -Exactly -ParameterFilter {
+            $Arguments[0] -eq "interface" -and
+                $Arguments[1] -eq "ip" -and
+                $Arguments[2] -eq "set" -and
+                $Arguments[3] -eq "dnsservers" -and
+                $Arguments[4] -eq "name=Ethernet" -and
+                $Arguments[5] -eq "source=dhcp"
+        }
+        Should -Invoke -CommandName netsh -Times 1 -Exactly -ParameterFilter {
+            $Arguments[0] -eq "interface" -and
+                $Arguments[1] -eq "ipv6" -and
+                $Arguments[2] -eq "set" -and
+                $Arguments[3] -eq "dnsservers" -and
+                $Arguments[4] -eq "name=Ethernet" -and
+                $Arguments[5] -eq "source=dhcp"
+        }
+    }
+
+    It "catches DNS setter failures so the tweak runspace can continue" {
+        Mock Set-DnsClientServerAddress { throw "DNS failed" }
+
+        { Set-WinUtilDNS -DNSProvider "Cloudflare" } | Should -Not -Throw
+
+        Should -Invoke -CommandName Write-WinUtilLog -Times 1 -Exactly -ParameterFilter {
+            $Level -eq "ERROR" -and
+                $Component -eq "DNS" -and
+                $Message -like "Unable to set DNS provider Cloudflare*"
+        }
+    }
+}