wgengine: move DNS configuration out of wgengine/router.

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

net/dns/manager.go

@@ -33,11 +33,11 @@ type Manager struct {
 }
 
 // NewManagers created a new manager from the given config.
-func NewManager(logf logger.Logf, interfaceName string) *Manager {
+func NewManager(logf logger.Logf, oscfg OSConfigurator) *Manager {
 	logf = logger.WithPrefix(logf, "dns: ")
 	m := &Manager{
 		logf: logf,
-		impl: newManager(logf, interfaceName),
+		impl: oscfg,
 	}
 
 	m.logf("using %T", m.impl)
@@ -81,7 +81,8 @@ func (m *Manager) Down() error {
 // in case the Tailscale daemon terminated without closing the router.
 // No other state needs to be instantiated before this runs.
 func Cleanup(logf logger.Logf, interfaceName string) {
-	dns := NewManager(logf, interfaceName)
+	oscfg := NewOSConfigurator(logf, interfaceName)
+	dns := NewManager(logf, oscfg)
 	if err := dns.Down(); err != nil {
 		logf("dns down: %v", err)
 	}

net/dns/manager_default.go

@@ -8,9 +8,9 @@ package dns
 
 import "tailscale.com/types/logger"
 
-func newManager(logger.Logf, string) OSConfigurator {
+func NewOSConfigurator(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.
-	return newNoopManager()
+	return NewNoopManager()
 }

net/dns/manager_freebsd.go

@@ -6,7 +6,7 @@ package dns
 
 import "tailscale.com/types/logger"
 
-func newManager(logf logger.Logf, _ string) OSConfigurator {
+func NewOSConfigurator(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) OSConfigurator {
+func NewOSConfigurator(logf logger.Logf, interfaceName string) OSConfigurator {
 	switch {
 	// TODO: rework NetworkManager and resolved support.
 	// case isResolvedActive():

net/dns/manager_openbsd.go

@@ -6,6 +6,6 @@ package dns
 
 import "tailscale.com/types/logger"
 
-func newManager(logger.Logf, string) OSConfigurator {
+func NewOSConfigurator(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) OSConfigurator {
+func NewOSConfigurator(logf logger.Logf, interfaceName string) OSConfigurator {
 	return windowsManager{
 		logf: logf,
 		guid: interfaceName,

net/dns/noop.go

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !linux,!freebsd,!openbsd,!windows
-
 package dns
 
 type noopManager struct{}
@@ -12,6 +10,6 @@ func (m noopManager) Set(OSConfig) error       { return nil }
 func (m noopManager) RoutingMode() RoutingMode { return RoutingModeNone }
 func (m noopManager) Close() error             { return nil }
 
-func newNoopManager() noopManager {
+func NewNoopManager() noopManager {
 	return noopManager{}
 }