feat(DNS): Add static cleanup funcs

To aid CLI in cleaning up configuration we expose static functions that know how to handle each provider and platform linked to https://github.com/fosrl/cli/issues/38

dns/override/dns_override_android.go

@@ -16,6 +16,7 @@ func RestoreDNSOverride() error {
 }
 
 // CleanupStaleState is a no-op on Android as DNS configuration is handled by the VpnService API
-func CleanupStaleState() error {
+func CleanupStaleState(interfaceName string) error {
+	_ = interfaceName
 	return nil
-}
+}

dns/override/dns_override_darwin.go

@@ -68,7 +68,8 @@ func RestoreDNSOverride() error {
 // to ensure DNS is working properly.
 //
 // On macOS, this cleans up any scutil DNS keys that were created but not removed.
-func CleanupStaleState() error {
+func CleanupStaleState(interfaceName string) error {
+	_ = interfaceName
 	if err := platform.CleanupStaleDarwinDNS(); err != nil {
 		logger.Warn("Failed to cleanup stale Darwin DNS config: %v", err)
 		return fmt.Errorf("Darwin DNS cleanup: %w", err)

dns/override/dns_override_ios.go

@@ -15,6 +15,7 @@ func RestoreDNSOverride() error {
 }
 
 // CleanupStaleState is a no-op on iOS as DNS configuration is handled by the system
-func CleanupStaleState() error {
+func CleanupStaleState(interfaceName string) error {
+	_ = interfaceName
 	return nil
-}
+}

dns/override/dns_override_unix.go

@@ -106,11 +106,11 @@ func RestoreDNSOverride() error {
 //
 // It checks and cleans up stale state from all supported DNS managers:
 // - NetworkManager: removes /etc/NetworkManager/conf.d/olm-dns.conf
-// - resolvconf: removes entry for the "olm" interface
+// - resolvconf: removes entry for the provided interface
 // - File-based: restores /etc/resolv.conf from backup if it exists
 //
 // This is safe to call even if no stale state exists.
-func CleanupStaleState() error {
+func CleanupStaleState(interfaceName string) error {
 	var errs []error
 
 	// Clean up NetworkManager stale config
@@ -121,8 +121,8 @@ func CleanupStaleState() error {
 		logger.Debug("NetworkManager DNS cleanup completed")
 	}
 
-	// Clean up resolvconf stale entries (use default interface name "olm")
-	if err := platform.CleanupStaleResolvconfDNS("olm"); err != nil {
+	// Clean up resolvconf stale entries for the provided interface
+	if err := platform.CleanupStaleResolvconfDNS(interfaceName); err != nil {
 		logger.Warn("Failed to cleanup stale resolvconf DNS config: %v", err)
 		errs = append(errs, fmt.Errorf("resolvconf cleanup: %w", err))
 	} else {

dns/override/dns_override_windows.go

@@ -69,10 +69,11 @@ func RestoreDNSOverride() error {
 //
 // On Windows, DNS configuration is tied to the interface GUID. When the WireGuard
 // interface is recreated, it gets a new GUID, so there's no stale state to clean up.
-func CleanupStaleState() error {
+func CleanupStaleState(interfaceName string) error {
 	// Windows DNS configuration via registry is interface-specific.
 	// When the WireGuard interface is recreated, it gets a new GUID,
 	// so there's no leftover state to clean up from previous sessions.
+	_ = interfaceName
 	logger.Debug("Windows DNS cleanup: no stale state to clean (interface-specific)")
 	return nil
 }