all: unify code to handle static DNS file path

cmd/cli/cli.go

@@ -435,7 +435,7 @@ func run(appCallback *AppCallback, stopCh chan struct{}) {
 		p.resetDNS(false, true)
 		// Iterate over all physical interfaces and restore static DNS if a saved static config exists.
 		withEachPhysicalInterfaces("", "restore static DNS", func(i *net.Interface) error {
-			file := savedStaticDnsSettingsFilePath(i)
+			file := ctrld.SavedStaticDnsSettingsFilePath(i)
 			if _, err := os.Stat(file); err == nil {
 				if err := restoreDNS(i); err != nil {
 					mainLog.Load().Error().Err(err).Msgf("Could not restore static DNS on interface %s", i.Name)
@@ -1077,7 +1077,7 @@ func uninstall(p *prog, s service.Service) {
 
 		// Iterate over all physical interfaces and restore DNS if a saved static config exists.
 		withEachPhysicalInterfaces(p.runningIface, "restore static DNS", func(i *net.Interface) error {
-			file := savedStaticDnsSettingsFilePath(i)
+			file := ctrld.SavedStaticDnsSettingsFilePath(i)
 			if _, err := os.Stat(file); err == nil {
 				if err := restoreDNS(i); err != nil {
 					mainLog.Load().Error().Err(err).Msgf("Could not restore static DNS on interface %s", i.Name)

cmd/cli/commands.go

@@ -977,7 +977,7 @@ NOTE: Uninstalling will set DNS to values provided by DHCP.`,
 				}
 				// Static DNS settings files.
 				withEachPhysicalInterfaces("", "", func(i *net.Interface) error {
-					file := savedStaticDnsSettingsFilePath(i)
+					file := ctrld.SavedStaticDnsSettingsFilePath(i)
 					if _, err := os.Stat(file); err == nil {
 						files = append(files, file)
 					}

cmd/cli/os_darwin.go

@@ -8,6 +8,7 @@ import (
 	"os/exec"
 	"strings"
 
+	"github.com/Control-D-Inc/ctrld"
 	"github.com/Control-D-Inc/ctrld/internal/resolvconffile"
 )
 
@@ -84,7 +85,7 @@ func resetDNS(iface *net.Interface) error {
 // restoreDNS restores the DNS settings of the given interface.
 // this should only be executed upon turning off the ctrld service.
 func restoreDNS(iface *net.Interface) (err error) {
-	if ns := savedStaticNameservers(iface); len(ns) > 0 {
+	if ns := ctrld.SavedStaticNameservers(iface); len(ns) > 0 {
 		err = setDNS(iface, ns)
 	}
 	return err

cmd/cli/os_windows.go

@@ -16,6 +16,7 @@ import (
 	"golang.org/x/sys/windows/registry"
 	"golang.zx2c4.com/wireguard/windows/tunnel/winipcfg"
 
+	"github.com/Control-D-Inc/ctrld"
 	ctrldnet "github.com/Control-D-Inc/ctrld/internal/net"
 )
 
@@ -161,7 +162,7 @@ func resetDNS(iface *net.Interface) error {
 // restoreDNS restores the DNS settings of the given interface.
 // this should only be executed upon turning off the ctrld service.
 func restoreDNS(iface *net.Interface) (err error) {
-	if nss := savedStaticNameservers(iface); len(nss) > 0 {
+	if nss := ctrld.SavedStaticNameservers(iface); len(nss) > 0 {
 		v4ns := make([]string, 0, 2)
 		v6ns := make([]string, 0, 2)
 		for _, ns := range nss {

cmd/cli/prog.go

@@ -868,7 +868,7 @@ func (p *prog) dnsWatchdog(iface *net.Interface, nameservers []string) {
 						return net.ParseIP(s).IsLoopback()
 					})
 					// if we have a static config and no saved IPs already, save them
-					if len(staticDNS) > 0 && len(savedStaticNameservers(iface)) == 0 {
+					if len(staticDNS) > 0 && len(ctrld.SavedStaticNameservers(iface)) == 0 {
 						// Save these static DNS values so that they can be restored later.
 						if err := saveCurrentStaticDNS(iface); err != nil {
 							mainLog.Load().Debug().Err(err).Msgf("failed to save static DNS for interface %s", iface.Name)
@@ -898,7 +898,7 @@ func (p *prog) dnsWatchdog(iface *net.Interface, nameservers []string) {
 								return net.ParseIP(s).IsLoopback()
 							})
 							// if we have a static config and no saved IPs already, save them
-							if len(staticDNS) > 0 && len(savedStaticNameservers(i)) == 0 {
+							if len(staticDNS) > 0 && len(ctrld.SavedStaticNameservers(i)) == 0 {
 								// Save these static DNS values so that they can be restored later.
 								if err := saveCurrentStaticDNS(i); err != nil {
 									mainLog.Load().Debug().Err(err).Msgf("failed to save static DNS for interface %s", i.Name)
@@ -976,7 +976,7 @@ func (p *prog) resetDNSForRunningIface(isStart bool, restoreStatic bool) (runnin
 	}
 
 	// Default logic: if there is a saved static DNS configuration, restore it.
-	saved := savedStaticNameservers(netIface)
+	saved := ctrld.SavedStaticNameservers(netIface)
 	if len(saved) > 0 && restoreStatic {
 		logger.Debug().Msgf("Restoring interface %q from saved static config: %v", netIface.Name, saved)
 		if err := setDNS(netIface, saved); err != nil {
@@ -1373,7 +1373,7 @@ func saveCurrentStaticDNS(iface *net.Interface) error {
 	default:
 		return errSaveCurrentStaticDNSNotSupported
 	}
-	file := savedStaticDnsSettingsFilePath(iface)
+	file := ctrld.SavedStaticDnsSettingsFilePath(iface)
 	ns, err := currentStaticDNS(iface)
 	if err != nil {
 		mainLog.Load().Warn().Err(err).Msgf("could not get current static DNS settings for %q", iface.Name)
@@ -1407,38 +1407,6 @@ func saveCurrentStaticDNS(iface *net.Interface) error {
 	return nil
 }
 
-// savedStaticDnsSettingsFilePath returns the path to saved DNS settings of the given interface.
-func savedStaticDnsSettingsFilePath(iface *net.Interface) string {
-	if iface == nil {
-		return ""
-	}
-	return absHomeDir(".dns_" + iface.Name)
-}
-
-// savedStaticNameservers returns the static DNS nameservers of the given interface.
-//
-//lint:ignore U1000 use in os_windows.go and os_darwin.go
-func savedStaticNameservers(iface *net.Interface) []string {
-	if iface == nil {
-		mainLog.Load().Debug().Msg("could not get saved static DNS settings for nil interface")
-		return nil
-	}
-	file := savedStaticDnsSettingsFilePath(iface)
-	if data, _ := os.ReadFile(file); len(data) > 0 {
-		saveValues := strings.Split(string(data), ",")
-		returnValues := []string{}
-		// check each one, if its in loopback range, remove it
-		for _, v := range saveValues {
-			if net.ParseIP(v).IsLoopback() {
-				continue
-			}
-			returnValues = append(returnValues, v)
-		}
-		return returnValues
-	}
-	return nil
-}
-
 // dnsChanged reports whether DNS settings for given interface was changed.
 // It returns false for a nil iface.
 //

nameservers_darwin.go

@@ -186,7 +186,7 @@ func getAllDHCPNameservers() []string {
 				Log(context.Background(), logger.Debug(),
 					"Failed to patch interface name %s: %v", drIfaceName, err)
 			}
-			staticNs, file := SavedStaticNameservers(drIface)
+			staticNs, file := SavedStaticNameserversAndPath(drIface)
 			Log(context.Background(), logger.Debug(),
 				"static dns servers from %s: %v", file, staticNs)
 			if len(staticNs) > 0 {

nameservers_windows.go

@@ -158,7 +158,7 @@ func getDNSServers(ctx context.Context) ([]string, error) {
 					0,                                    // DomainGuid - not needed
 					0,                                    // SiteName - not needed
 					uintptr(flags),                       // Flags
-					uintptr(unsafe.Pointer(&info))) // DomainControllerInfo - output
+					uintptr(unsafe.Pointer(&info)))       // DomainControllerInfo - output
 
 				if ret != 0 {
 					switch ret {
@@ -309,7 +309,7 @@ func getDNSServers(ctx context.Context) ([]string, error) {
 			Log(context.Background(), logger.Debug(),
 				"Failed to get interface by name %s: %v", drIfaceName, err)
 		} else {
-			staticNs, file := SavedStaticNameservers(drIface)
+			staticNs, file := SavedStaticNameserversAndPath(drIface)
 			Log(context.Background(), logger.Debug(),
 				"static dns servers from %s: %v", file, staticNs)
 			if len(staticNs) > 0 {

staticdns.go

@@ -54,13 +54,18 @@ func userHomeDir() (string, error) {
 
 // SavedStaticDnsSettingsFilePath returns the file path where the static DNS settings
 // for the provided interface are saved.
+//
+// The caller must ensure iface is non-nil.
 func SavedStaticDnsSettingsFilePath(iface *net.Interface) string {
 	// The file is stored in the user home directory under a hidden file.
 	return absHomeDir(".dns_" + iface.Name)
 }
 
-// SavedStaticNameservers returns the stored static nameservers for the given interface.
-func SavedStaticNameservers(iface *net.Interface) ([]string, string) {
+// SavedStaticNameserversAndPath returns the stored static nameservers for the given interface,
+// and the absolute path to file that stored the settings.
+//
+// The caller must ensure iface is non-nil.
+func SavedStaticNameserversAndPath(iface *net.Interface) ([]string, string) {
 	file := SavedStaticDnsSettingsFilePath(iface)
 	data, err := os.ReadFile(file)
 	if err != nil || len(data) == 0 {
@@ -77,3 +82,9 @@ func SavedStaticNameservers(iface *net.Interface) ([]string, string) {
 	}
 	return ns, file
 }
+
+// SavedStaticNameservers is like SavedStaticNameserversAndPath, but only returns the static nameservers.
+func SavedStaticNameservers(iface *net.Interface) []string {
+	nss, _ := SavedStaticNameserversAndPath(iface)
+	return nss
+}