net/dns: replace managerImpl with OSConfigurator in code.

Signed-off-by: David Anderson <danderson@tailscale.com>

net/dns/direct.go

@@ -110,12 +110,11 @@ func isResolvedRunning() bool {
 // or as cleanup if the program terminates unexpectedly.
 type directManager struct{}
 
-func newDirectManager() managerImpl {
+func newDirectManager() directManager {
 	return directManager{}
 }
 
-// Up implements managerImpl.
+func (m directManager) Set(config OSConfig) error {
-func (m directManager) Up(config OSConfig) error {
 	// Write the tsConf file.
 	buf := new(bytes.Buffer)
 	writeResolvConf(buf, config.Nameservers, config.Domains)
@@ -160,8 +159,11 @@ func (m directManager) Up(config OSConfig) error {
 	return nil
 }
 
-// Down implements managerImpl.
+func (m directManager) RoutingMode() RoutingMode {
-func (m directManager) Down() error {
+	return RoutingModeNone
+}
+
+func (m directManager) Close() error {
 	if _, err := os.Stat(backupConf); err != nil {
 		// If the backup file does not exist, then Up never ran successfully.
 		if os.IsNotExist(err) {

net/dns/manager.go

@@ -23,19 +23,11 @@ import (
 // Such operations should be wrapped in a timeout context.
 const reconfigTimeout = time.Second
 
-type managerImpl interface {
-	// Up updates system DNS settings to match the given configuration.
-	Up(OSConfig) error
-	// Down undoes the effects of Up.
-	// It is idempotent and performs no action if Up has never been called.
-	Down() error
-}
-
 // Manager manages system DNS settings.
 type Manager struct {
 	logf logger.Logf
 
-	impl managerImpl
+	impl OSConfigurator
 
 	config OSConfig
 }
@@ -60,7 +52,7 @@ func (m *Manager) Set(config OSConfig) error {
 	m.logf("Set: %+v", config)
 
 	if len(config.Nameservers) == 0 {
-		err := m.impl.Down()
+		err := m.impl.Set(OSConfig{})
 		// If we save the config, we will not retry next time. Only do this on success.
 		if err == nil {
 			m.config = config
@@ -68,7 +60,7 @@ func (m *Manager) Set(config OSConfig) error {
 		return err
 	}
 
-	err := m.impl.Up(config)
+	err := m.impl.Set(config)
 	// If we save the config, we will not retry next time. Only do this on success.
 	if err == nil {
 		m.config = config
@@ -78,11 +70,11 @@ func (m *Manager) Set(config OSConfig) error {
 }
 
 func (m *Manager) Up() error {
-	return m.impl.Up(m.config)
+	return m.impl.Set(m.config)
 }
 
 func (m *Manager) Down() error {
-	return m.impl.Down()
+	return m.impl.Close()
 }
 
 // Cleanup restores the system DNS configuration to its original state

net/dns/manager_default.go

@@ -8,7 +8,7 @@ package dns
 
 import "tailscale.com/types/logger"
 
-func newManager(logger.Logf, string) managerImpl {
+func newManager(logger.Logf, string) OSConfigurator {
 	// TODO(dmytro): on darwin, we should use a macOS-specific method such as scutil.
 	// This is currently not implemented. Editing /etc/resolv.conf does not work,
 	// as most applications use the system resolver, which disregards it.

net/dns/manager_freebsd.go

@@ -6,7 +6,7 @@ package dns
 
 import "tailscale.com/types/logger"
 
-func newManager(logf logger.Logf, _ string) managerImpl {
+func newManager(logf logger.Logf, _ string) OSConfigurator {
 	switch {
 	case isResolvconfActive():
 		return newResolvconfManager(logf)

net/dns/manager_linux.go

@@ -6,7 +6,7 @@ package dns
 
 import "tailscale.com/types/logger"
 
-func newManager(logf logger.Logf, interfaceName string) managerImpl {
+func newManager(logf logger.Logf, interfaceName string) OSConfigurator {
 	switch {
 	case isResolvedActive():
 		return newResolvedManager()

net/dns/manager_openbsd.go

@@ -6,6 +6,6 @@ package dns
 
 import "tailscale.com/types/logger"
 
-func newManager(logger.Logf, string) managerImpl {
+func newManager(logger.Logf, string) OSConfigurator {
 	return newDirectManager()
 }

net/dns/manager_windows.go

@@ -25,7 +25,7 @@ type windowsManager struct {
 	guid string
 }
 
-func newManager(logf logger.Logf, interfaceName string) managerImpl {
+func newManager(logf logger.Logf, interfaceName string) OSConfigurator {
 	return windowsManager{
 		logf: logf,
 		guid: interfaceName,
@@ -64,7 +64,7 @@ func (m windowsManager) setDomains(basePath string, domains []string) error {
 	return setRegistryString(path, "SearchList", value)
 }
 
-func (m windowsManager) Up(config OSConfig) error {
+func (m windowsManager) Set(config OSConfig) error {
 	var ipsv4 []string
 	var ipsv6 []string
 
@@ -113,6 +113,10 @@ func (m windowsManager) Up(config OSConfig) error {
 	return nil
 }
 
-func (m windowsManager) Down() error {
+func (m windowsManager) RoutingMode() RoutingMode {
-	return m.Up(OSConfig{Nameservers: nil, Domains: nil})
+	return RoutingModeNone
+}
+
+func (m windowsManager) Close() error {
+	return m.Set(OSConfig{})
 }

net/dns/nm.go

@@ -53,7 +53,7 @@ type nmManager struct {
 	interfaceName string
 }
 
-func newNMManager(interfaceName string) managerImpl {
+func newNMManager(interfaceName string) nmManager {
 	return nmManager{
 		interfaceName: interfaceName,
 	}
@@ -61,8 +61,7 @@ func newNMManager(interfaceName string) managerImpl {
 
 type nmConnectionSettings map[string]map[string]dbus.Variant
 
-// Up implements managerImpl.
+func (m nmManager) Set(config OSConfig) error {
-func (m nmManager) Up(config OSConfig) error {
 	ctx, cancel := context.WithTimeout(context.Background(), reconfigTimeout)
 	defer cancel()
 
@@ -199,7 +198,8 @@ func (m nmManager) Up(config OSConfig) error {
 	return nil
 }
 
-// Down implements managerImpl.
+func (m nmManager) RoutingMode() RoutingMode { return RoutingModeNone }
-func (m nmManager) Down() error {
+
-	return m.Up(OSConfig{Nameservers: nil, Domains: nil})
+func (m nmManager) Close() error {
+	return m.Set(OSConfig{})
 }

net/dns/noop.go

@@ -8,12 +8,10 @@ package dns
 
 type noopManager struct{}
 
-// Up implements managerImpl.
+func (m noopManager) Set(OSConfig) error       { return nil }
-func (m noopManager) Up(OSConfig) error { return nil }
+func (m noopManager) RoutingMode() RoutingMode { return RoutingModeNone }
+func (m noopManager) Close() error             { return nil }
 
-// Down implements managerImpl.
+func newNoopManager() noopManager {
-func (m noopManager) Down() error { return nil }
-
-func newNoopManager() managerImpl {
 	return noopManager{}
 }

net/dns/osconfig.go

@@ -27,7 +27,7 @@ type OSConfigurator interface {
 	// If cfg nil or the zero value, all Tailscale-related DNS
 	// configuration is removed.
 	// Set must not be called after Close.
-	Set(cfg *OSConfig) error
+	Set(cfg OSConfig) error
 	// DNSRoutingMode reports the DNS routing capabilities of this OS
 	// configurator.
 	RoutingMode() RoutingMode

net/dns/resolvconf.go

@@ -101,7 +101,7 @@ type resolvconfManager struct {
 	impl resolvconfImpl
 }
 
-func newResolvconfManager(logf logger.Logf) managerImpl {
+func newResolvconfManager(logf logger.Logf) resolvconfManager {
 	impl := getResolvconfImpl()
 	logf("resolvconf implementation is %s", impl)
 
@@ -115,8 +115,7 @@ func newResolvconfManager(logf logger.Logf) managerImpl {
 // when running resolvconfLegacy, hopefully placing our config first.
 const resolvconfConfigName = "tun-tailscale.inet"
 
-// Up implements managerImpl.
+func (m resolvconfManager) Set(config OSConfig) error {
-func (m resolvconfManager) Up(config OSConfig) error {
 	stdin := new(bytes.Buffer)
 	writeResolvConf(stdin, config.Nameservers, config.Domains) // dns_direct.go
 
@@ -139,8 +138,11 @@ func (m resolvconfManager) Up(config OSConfig) error {
 	return nil
 }
 
-// Down implements managerImpl.
+func (m resolvconfManager) RoutingMode() RoutingMode {
-func (m resolvconfManager) Down() error {
+	return RoutingModeNone
+}
+
+func (m resolvconfManager) Close() error {
 	var cmd *exec.Cmd
 	switch m.impl {
 	case resolvconfOpenresolv:

net/dns/resolved.go

@@ -77,12 +77,12 @@ func isResolvedActive() bool {
 // resolvedManager uses the systemd-resolved DBus API.
 type resolvedManager struct{}
 
-func newResolvedManager() managerImpl {
+func newResolvedManager() resolvedManager {
 	return resolvedManager{}
 }
 
 // Up implements managerImpl.
-func (m resolvedManager) Up(config OSConfig) error {
+func (m resolvedManager) Set(config OSConfig) error {
 	ctx, cancel := context.WithTimeout(context.Background(), reconfigTimeout)
 	defer cancel()
 
@@ -151,8 +151,11 @@ func (m resolvedManager) Up(config OSConfig) error {
 	return nil
 }
 
-// Down implements managerImpl.
+func (m resolvedManager) RoutingMode() RoutingMode {
-func (m resolvedManager) Down() error {
+	return RoutingModeNone
+}
+
+func (m resolvedManager) Close() error {
 	ctx, cancel := context.WithTimeout(context.Background(), reconfigTimeout)
 	defer cancel()