wgengine: move DNS configuration out of wgengine/router.

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

cmd/tailscaled/tailscaled.go

@@ -350,6 +350,13 @@ func tryEngine(logf logger.Logf, linkMon *monitor.Mon, name string) (e wgengine.
 			return nil, false, err
 		}
 		conf.Router = r
+		tunname, err := dev.Name()
+		if err != nil {
+			r.Close()
+			dev.Close()
+			return nil, false, err
+		}
+		conf.DNS = dns.NewOSConfigurator(logf, tunname)
 	}
 	e, err = wgengine.NewUserspaceEngine(logf, conf)
 	if err != nil {

internal/deepprint/deepprint_test.go

@@ -9,7 +9,6 @@ import (
 	"testing"
 
 	"inet.af/netaddr"
-	"tailscale.com/net/dns"
 	"tailscale.com/wgengine/router"
 	"tailscale.com/wgengine/wgcfg"
 )
@@ -45,9 +44,9 @@ func getVal() []interface{} {
 			},
 		},
 		&router.Config{
-			DNS: dns.OSConfig{
+			Routes: []netaddr.IPPrefix{
-				Nameservers: []netaddr.IP{netaddr.IPv4(8, 8, 8, 8)},
+				netaddr.MustParseIPPrefix("1.2.3.0/24"),
-				Domains:     []string{"tailscale.net"},
+				netaddr.MustParseIPPrefix("1234::/64"),
 			},
 		},
 		map[string]string{

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{}
 }

wgengine/router/router.go

@@ -9,7 +9,6 @@ package router
 import (
 	"github.com/tailscale/wireguard-go/tun"
 	"inet.af/netaddr"
-	"tailscale.com/net/dns"
 	"tailscale.com/types/logger"
 	"tailscale.com/types/preftype"
 )
@@ -58,11 +57,7 @@ type Config struct {
 	// this node has chosen to use.
 	Routes []netaddr.IPPrefix
 
-	// Set internally by wgengine, must not be set elsewhere.
-	DNS dns.OSConfig
-
 	// Linux-only things below, ignored on other platforms.
-
 	SubnetRoutes     []netaddr.IPPrefix     // subnets being advertised to other Tailscale nodes
 	SNATSubnetRoutes bool                   // SNAT traffic to local subnets
 	NetfilterMode    preftype.NetfilterMode // how much to manage netfilter rules

wgengine/router/router_linux.go

@@ -18,7 +18,6 @@ import (
 	"github.com/go-multierror/multierror"
 	"github.com/tailscale/wireguard-go/tun"
 	"inet.af/netaddr"
-	"tailscale.com/net/dns"
 	"tailscale.com/net/tsaddr"
 	"tailscale.com/types/logger"
 	"tailscale.com/types/preftype"
@@ -102,8 +101,6 @@ type linuxRouter struct {
 	v6Available     bool
 	v6NATAvailable  bool
 
-	dns *dns.Manager
-
 	ipt4 netfilterRunner
 	ipt6 netfilterRunner
 	cmd  commandRunner
@@ -158,7 +155,6 @@ func newUserspaceRouterAdvanced(logf logger.Logf, tunname string, netfilter4, ne
 		ipt4: netfilter4,
 		ipt6: netfilter6,
 		cmd:  cmd,
-		dns:  dns.NewManager(logf, tunname),
 	}, nil
 }
 
@@ -180,9 +176,6 @@ func (r *linuxRouter) Up() error {
 }
 
 func (r *linuxRouter) Close() error {
-	if err := r.dns.Down(); err != nil {
-		return fmt.Errorf("dns down: %w", err)
-	}
 	if err := r.downInterface(); err != nil {
 		return err
 	}
@@ -206,10 +199,6 @@ func (r *linuxRouter) Set(cfg *Config) error {
 		cfg = &shutdownConfig
 	}
 
-	if err := r.dns.Set(cfg.DNS); err != nil {
-		errs = append(errs, fmt.Errorf("dns set: %w", err))
-	}
-
 	if err := r.setNetfilterMode(cfg.NetfilterMode); err != nil {
 		errs = append(errs, err)
 	}

wgengine/router/router_openbsd.go

@@ -12,7 +12,6 @@ import (
 
 	"github.com/tailscale/wireguard-go/tun"
 	"inet.af/netaddr"
-	"tailscale.com/net/dns"
 	"tailscale.com/types/logger"
 )
 
@@ -26,8 +25,6 @@ type openbsdRouter struct {
 	local4  netaddr.IPPrefix
 	local6  netaddr.IPPrefix
 	routes  map[netaddr.IPPrefix]struct{}
-
-	dns *dns.Manager
 }
 
 func newUserspaceRouter(logf logger.Logf, tundev tun.Device) (Router, error) {
@@ -39,7 +36,6 @@ func newUserspaceRouter(logf logger.Logf, tundev tun.Device) (Router, error) {
 	return &openbsdRouter{
 		logf:    logf,
 		tunname: tunname,
-		dns:     dns.NewManager(logf, tunname),
 	}, nil
 }
 
@@ -210,17 +206,10 @@ func (r *openbsdRouter) Set(cfg *Config) error {
 	r.local6 = localAddr6
 	r.routes = newRoutes
 
-	if err := r.dns.Set(cfg.DNS); err != nil {
-		errq = fmt.Errorf("dns set: %v", err)
-	}
-
 	return errq
 }
 
 func (r *openbsdRouter) Close() error {
-	if err := r.dns.Down(); err != nil {
-		return fmt.Errorf("dns down: %v", err)
-	}
 	cleanup(r.logf, r.tunname)
 	return nil
 }

wgengine/router/router_userspace_bsd.go

@@ -14,7 +14,6 @@ import (
 
 	"github.com/tailscale/wireguard-go/tun"
 	"inet.af/netaddr"
-	"tailscale.com/net/dns"
 	"tailscale.com/types/logger"
 	"tailscale.com/version"
 )
@@ -24,8 +23,6 @@ type userspaceBSDRouter struct {
 	tunname string
 	local   []netaddr.IPPrefix
 	routes  map[netaddr.IPPrefix]struct{}
-
-	dns *dns.Manager
 }
 
 func newUserspaceBSDRouter(logf logger.Logf, tundev tun.Device) (Router, error) {
@@ -37,7 +34,6 @@ func newUserspaceBSDRouter(logf logger.Logf, tundev tun.Device) (Router, error)
 	return &userspaceBSDRouter{
 		logf:    logf,
 		tunname: tunname,
-		dns:     dns.NewManager(logf, tunname),
 	}, nil
 }
 
@@ -183,18 +179,9 @@ func (r *userspaceBSDRouter) Set(cfg *Config) (reterr error) {
 	}
 	r.routes = newRoutes
 
-	if err := r.dns.Set(cfg.DNS); err != nil {
-		r.logf("DNS set: %v", err)
-		setErr(err)
-	}
-
 	return errq
 }
 
 func (r *userspaceBSDRouter) Close() error {
-	if err := r.dns.Down(); err != nil {
-		r.logf("dns down: %v", err)
-	}
-	// No interface cleanup is necessary during normal shutdown.
 	return nil
 }

wgengine/router/router_windows.go

@@ -29,7 +29,6 @@ type winRouter struct {
 	logf                func(fmt string, args ...interface{})
 	nativeTun           *tun.NativeTun
 	routeChangeCallback *winipcfg.RouteChangeCallback
-	dns                 *dns.Manager
 	firewall            *firewallTweaker
 
 	// firewallSubproc is a subprocess that runs a tweaked version of
@@ -53,7 +52,6 @@ func newUserspaceRouter(logf logger.Logf, tundev tun.Device) (Router, error) {
 	return &winRouter{
 		logf:      logf,
 		nativeTun: nativeTun,
-		dns:       dns.NewManager(logf, guid.String()),
 		firewall: &firewallTweaker{
 			logf:    logger.WithPrefix(logf, "firewall: "),
 			tunGUID: *guid,
@@ -92,10 +90,6 @@ func (r *winRouter) Set(cfg *Config) error {
 		return err
 	}
 
-	if err := r.dns.Set(cfg.DNS); err != nil {
-		return fmt.Errorf("dns set: %w", err)
-	}
-
 	// Flush DNS on router config change to clear cached DNS entries (solves #1430)
 	if err := dns.Flush(); err != nil {
 		r.logf("flushdns error: %v", err)
@@ -116,9 +110,6 @@ func hasDefaultRoute(routes []netaddr.IPPrefix) bool {
 func (r *winRouter) Close() error {
 	r.firewall.clear()
 
-	if err := r.dns.Down(); err != nil {
-		return fmt.Errorf("dns down: %w", err)
-	}
 	if r.routeChangeCallback != nil {
 		r.routeChangeCallback.Unregister()
 	}

wgengine/userspace.go

@@ -84,6 +84,7 @@ type userspaceEngine struct {
 	tundev            *tstun.Wrapper
 	wgdev             *device.Device
 	router            router.Router
+	dns               *dns.Manager
 	resolver          *resolver.Resolver
 	magicConn         *magicsock.Conn
 	linkMon           *monitor.Mon
@@ -143,6 +144,10 @@ type Config struct {
 	// If nil, a fake Router that does nothing is used.
 	Router router.Router
 
+	// DNS interfaces the Engine to the OS DNS resolver configuration.
+	// If nil, a fake OSConfigurator that does nothing is used.
+	DNS dns.OSConfigurator
+
 	// LinkMonitor optionally provides an existing link monitor to re-use.
 	// If nil, a new link monitor is created.
 	LinkMonitor *monitor.Mon
@@ -193,6 +198,10 @@ func NewUserspaceEngine(logf logger.Logf, conf Config) (_ Engine, reterr error)
 		logf("[v1] using fake (no-op) OS network configurator")
 		conf.Router = router.NewFake(logf)
 	}
+	if conf.DNS == nil {
+		logf("[v1] using fake (no-op) DNS configurator")
+		conf.DNS = dns.NewNoopManager()
+	}
 
 	tsTUNDev := tstun.Wrap(logf, conf.Tun)
 	closePool.add(tsTUNDev)
@@ -204,6 +213,7 @@ func NewUserspaceEngine(logf logger.Logf, conf Config) (_ Engine, reterr error)
 		waitCh:  make(chan struct{}),
 		tundev:  tsTUNDev,
 		router:  conf.Router,
+		dns:     dns.NewManager(logf, conf.DNS),
 		pingers: make(map[wgkey.Key]*pinger),
 	}
 	e.isLocalAddr.Store(genLocalAddrFunc(nil))
@@ -990,25 +1000,26 @@ func (e *userspaceEngine) Reconfig(cfg *wgcfg.Config, routerCfg *router.Config,
 			LocalDomains: dnsCfg.AuthoritativeSuffixes,
 			Routes:       map[string][]netaddr.IPPort{},
 		}
+		osCfg := dns.OSConfig{
+			Domains: dnsCfg.SearchDomains,
+		}
 		// We must proxy through quad-100 if MagicDNS hosts are in
 		// use, or there are any per-domain routes.
 		mustProxy := len(dnsCfg.Hosts) > 0 || len(dnsCfg.Routes) > 0
-		routerCfg.DNS = dns.OSConfig{
-			Domains: dnsCfg.SearchDomains,
-		}
 		if mustProxy {
-			routerCfg.DNS.Nameservers = []netaddr.IP{tsaddr.TailscaleServiceIP()}
+			osCfg.Nameservers = []netaddr.IP{tsaddr.TailscaleServiceIP()}
 			resolverCfg.Routes["."] = dnsCfg.DefaultResolvers
 			for suffix, resolvers := range dnsCfg.Routes {
 				resolverCfg.Routes[suffix] = resolvers
 			}
 		} else {
 			for _, resolver := range dnsCfg.DefaultResolvers {
-				routerCfg.DNS.Nameservers = append(routerCfg.DNS.Nameservers, resolver.IP)
+				osCfg.Nameservers = append(osCfg.Nameservers, resolver.IP)
 			}
 		}
-		routerCfg.DNS.Domains = dnsCfg.SearchDomains
+		osCfg.Domains = dnsCfg.SearchDomains
 		e.resolver.SetConfig(resolverCfg) // TODO: check error and propagate to health pkg
+		e.dns.Set(osCfg)                  // TODO: check error and propagate to health pkg
 		e.logf("wgengine: Reconfig: configuring router")
 		err := e.router.Set(routerCfg)
 		health.SetRouterHealth(err)