Merge 8085324449 into f8cd07fb8a

cmd/tailscaled/tailscaled.go

@@ -771,7 +771,7 @@ func tryEngine(logf logger.Logf, sys *tsd.System, name string) (onlyNetstack boo
 			// configuration being unavailable (from the noop
 			// manager). More in Issue 4017.
 			// TODO(bradfitz): add a Synology-specific DNS manager.
-			conf.DNS, err = dns.NewOSConfigurator(logf, sys.HealthTracker.Get(), sys.PolicyClientOrDefault(), sys.ControlKnobs(), "") // empty interface name
+			conf.DNS, err = dns.NewOSConfigurator(logf, sys.HealthTracker.Get(), sys.Bus.Get(), sys.PolicyClientOrDefault(), sys.ControlKnobs(), "") // empty interface name
 			if err != nil {
 				return false, fmt.Errorf("dns.NewOSConfigurator: %w", err)
 			}
@@ -805,7 +805,7 @@ func tryEngine(logf logger.Logf, sys *tsd.System, name string) (onlyNetstack boo
 			return false, fmt.Errorf("creating router: %w", err)
 		}
 
-		d, err := dns.NewOSConfigurator(logf, sys.HealthTracker.Get(), sys.PolicyClientOrDefault(), sys.ControlKnobs(), devName)
+		d, err := dns.NewOSConfigurator(logf, sys.HealthTracker.Get(), sys.Bus.Get(), sys.PolicyClientOrDefault(), sys.ControlKnobs(), devName)
 		if err != nil {
 			dev.Close()
 			r.Close()

net/dns/direct.go

@@ -21,6 +21,7 @@ import (
 	"slices"
 	"strings"
 	"sync"
+	"sync/atomic"
 	"time"
 
 	"tailscale.com/feature"
@@ -29,6 +30,7 @@ import (
 	"tailscale.com/net/tsaddr"
 	"tailscale.com/types/logger"
 	"tailscale.com/util/dnsname"
+	"tailscale.com/util/eventbus"
 	"tailscale.com/version/distro"
 )
 
@@ -135,6 +137,11 @@ type directManager struct {
 	// but is better than having non-functioning DNS.
 	renameBroken bool
 
+	trampleCount  atomic.Int64
+	trampleTimer  *time.Timer
+	eventClient   *eventbus.Client
+	trampleDNSPub *eventbus.Publisher[TrampleDNS]
+
 	ctx      context.Context    // valid until Close
 	ctxClose context.CancelFunc // closes ctx
 
@@ -145,11 +152,13 @@ type directManager struct {
 }
 
 //lint:ignore U1000 used in manager_{freebsd,openbsd}.go
-func newDirectManager(logf logger.Logf, health *health.Tracker) *directManager {
-	return newDirectManagerOnFS(logf, health, directFS{})
+func newDirectManager(logf logger.Logf, health *health.Tracker, bus *eventbus.Bus) *directManager {
+	return newDirectManagerOnFS(logf, health, bus, directFS{})
 }
 
-func newDirectManagerOnFS(logf logger.Logf, health *health.Tracker, fs wholeFileFS) *directManager {
+var trampleWatchDuration = 5 * time.Second
+
+func newDirectManagerOnFS(logf logger.Logf, health *health.Tracker, bus *eventbus.Bus, fs wholeFileFS) *directManager {
 	ctx, cancel := context.WithCancel(context.Background())
 	m := &directManager{
 		logf:     logf,
@@ -158,6 +167,13 @@ func newDirectManagerOnFS(logf logger.Logf, health *health.Tracker, fs wholeFile
 		ctx:      ctx,
 		ctxClose: cancel,
 	}
+	if bus != nil {
+		m.eventClient = bus.Client("dns.directManager")
+		m.trampleDNSPub = eventbus.Publish[TrampleDNS](m.eventClient)
+	}
+	m.trampleTimer = time.AfterFunc(trampleWatchDuration, func() {
+		m.trampleCount.Store(0)
+	})
 	go m.runFileWatcher()
 	return m
 }
@@ -481,10 +497,26 @@ func (m *directManager) checkForFileTrample() {
 	}
 	m.logf("trample: resolv.conf changed from what we expected. did some other program interfere? current contents: %q", show)
 	m.health.SetUnhealthy(resolvTrampleWarnable, nil)
+	if m.trampleDNSPub != nil {
+		n := m.trampleCount.Add(1)
+
+		if n < 10 {
+			m.trampleDNSPub.Publish(TrampleDNS{
+				LastTrample:       time.Now(),
+				TramplesInTimeout: n,
+			})
+			m.trampleTimer.Reset(trampleWatchDuration)
+		} else {
+			m.logf("trample: resolv.conf was trampled too many times (%d). Abandoning trying to fix it.", n)
+		}
+	}
 }
 
 func (m *directManager) Close() error {
 	m.ctxClose()
+	if m.eventClient != nil {
+		m.eventClient.Close()
+	}
 
 	// We used to keep a file for the tailscale config and symlinked
 	// to it, but then we stopped because /etc/resolv.conf being a

net/dns/direct_linux_test.go

@@ -0,0 +1,109 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build linux
+
+package dns
+
+import (
+	"context"
+	"fmt"
+	"net/netip"
+	"os"
+	"path/filepath"
+	"testing"
+	"testing/synctest"
+
+	"github.com/illarion/gonotify/v3"
+
+	"tailscale.com/util/dnsname"
+	"tailscale.com/util/eventbus/eventbustest"
+)
+
+func TestDNSTrampleRecovery(t *testing.T) {
+	HookWatchFile.Set(watchFile)
+	synctest.Test(t, func(t *testing.T) {
+		tmp := t.TempDir()
+		if err := os.MkdirAll(filepath.Join(tmp, "etc"), 0700); err != nil {
+			t.Fatal(err)
+		}
+		resolvPath := "/etc/resolv.conf"
+		fs := directFS{prefix: tmp}
+		readFile := func(t *testing.T, path string) string {
+			t.Helper()
+			b, err := fs.ReadFile(path)
+			if err != nil {
+				t.Fatal(err)
+			}
+			return string(b)
+		}
+
+		bus := eventbustest.NewBus(t)
+		eventbustest.LogAllEvents(t, bus)
+		m := newDirectManagerOnFS(t.Logf, nil, bus, fs)
+		defer m.Close()
+
+		if err := m.SetDNS(OSConfig{
+			Nameservers:   []netip.Addr{netip.MustParseAddr("8.8.8.8"), netip.MustParseAddr("8.8.4.4")},
+			SearchDomains: []dnsname.FQDN{"ts.net.", "ts-dns.test."},
+			MatchDomains:  []dnsname.FQDN{"ignored."},
+		}); err != nil {
+			t.Fatal(err)
+		}
+
+		want := `# resolv.conf(5) file generated by tailscale
+# For more info, see https://tailscale.com/s/resolvconf-overwrite
+# DO NOT EDIT THIS FILE BY HAND -- CHANGES WILL BE OVERWRITTEN
+
+nameserver 8.8.8.8
+nameserver 8.8.4.4
+search ts.net ts-dns.test
+`
+		if got := readFile(t, resolvPath); got != want {
+			t.Fatalf("resolv.conf:\n%s, want:\n%s", got, want)
+		}
+
+		tw := eventbustest.NewWatcher(t, bus)
+
+		trample := "Hvem er det som tramper på min bro?"
+		if err := fs.WriteFile(resolvPath, []byte(trample), 0644); err != nil {
+			t.Fatal(err)
+		}
+		synctest.Wait()
+
+		if err := eventbustest.Expect(tw, eventbustest.Type[TrampleDNS]()); err != nil {
+			t.Errorf("did not see trample event: %s", err)
+		}
+	})
+}
+
+// watchFile is generally copied from linuxtrample, but cancels the context
+// after one trample to end the test.
+func watchFile(ctx context.Context, dir, filename string, cb func()) error {
+	ctx, cancel := context.WithCancel(ctx)
+	defer cancel()
+
+	const events = gonotify.IN_ATTRIB |
+		gonotify.IN_CLOSE_WRITE |
+		gonotify.IN_CREATE |
+		gonotify.IN_DELETE |
+		gonotify.IN_MODIFY |
+		gonotify.IN_MOVE
+
+	watcher, err := gonotify.NewDirWatcher(ctx, events, dir)
+	if err != nil {
+		return fmt.Errorf("NewDirWatcher: %w", err)
+	}
+
+	for {
+		select {
+		case event := <-watcher.C:
+			if event.Name == filename {
+				cb()
+				cancel()
+			}
+		case <-ctx.Done():
+			return ctx.Err()
+		}
+	}
+}

net/dns/manager.go

@@ -55,6 +55,8 @@ type Manager struct {
 	logf   logger.Logf
 	health *health.Tracker
 
+	eventClient *eventbus.Client
+
 	activeQueriesAtomic int32
 
 	ctx       context.Context    // good until Down
@@ -69,10 +71,10 @@ type Manager struct {
 	config *Config    // Tracks the last viable DNS configuration set by Set.  nil on failures other than compilation failures or if set has never been called.
 }
 
-// NewManagers created a new manager from the given config.
+// NewManager created a new manager from the given config.
 //
 // knobs may be nil.
-func NewManager(logf logger.Logf, oscfg OSConfigurator, health *health.Tracker, dialer *tsdial.Dialer, linkSel resolver.ForwardLinkSelector, knobs *controlknobs.Knobs, goos string) *Manager {
+func NewManager(logf logger.Logf, oscfg OSConfigurator, health *health.Tracker, dialer *tsdial.Dialer, linkSel resolver.ForwardLinkSelector, knobs *controlknobs.Knobs, goos string, bus *eventbus.Bus) *Manager {
 	if !buildfeatures.HasDNS {
 		return nil
 	}
@@ -96,6 +98,22 @@ func NewManager(logf logger.Logf, oscfg OSConfigurator, health *health.Tracker,
 		goos:     goos,
 	}
 
+	if bus != nil {
+		m.eventClient = bus.Client("dns.Manager")
+		eventbus.SubscribeFunc(m.eventClient, func(trample TrampleDNS) {
+			m.mu.Lock()
+			defer m.mu.Unlock()
+			if m.config == nil {
+				m.logf("resolve.conf was trampled, but there is no DNS config")
+				return
+			}
+			m.logf("resolve.conf was trampled, setting existing config again")
+			if err := m.setLocked(*m.config); err != nil {
+				m.logf("error setting DNS config: %s", err)
+			}
+		})
+	}
+
 	m.ctx, m.ctxCancel = context.WithCancel(context.Background())
 	m.logf("using %T", m.os)
 	return m
@@ -178,9 +196,7 @@ func (m *Manager) setLocked(cfg Config) error {
 		m.config = nil
 		return err
 	}
-	if err := m.os.SetDNS(ocfg); err != nil {
-		m.config = nil
-		m.health.SetUnhealthy(osConfigurationSetWarnable, health.Args{health.ArgError: err.Error()})
+	if err := m.setDNSLocked(ocfg); err != nil {
 		return err
 	}
 
@@ -190,6 +206,15 @@ func (m *Manager) setLocked(cfg Config) error {
 	return nil
 }
 
+func (m *Manager) setDNSLocked(ocfg OSConfig) error {
+	if err := m.os.SetDNS(ocfg); err != nil {
+		m.config = nil
+		m.health.SetUnhealthy(osConfigurationSetWarnable, health.Args{health.ArgError: err.Error()})
+		return err
+	}
+	return nil
+}
+
 // compileHostEntries creates a list of single-label resolutions possible
 // from the configured hosts and search domains.
 // The entries are compiled in the order of the search domains, then the hosts.
@@ -457,6 +482,11 @@ const (
 	maxReqSizeTCP = 4096
 )
 
+type TrampleDNS struct {
+	LastTrample       time.Time
+	TramplesInTimeout int64
+}
+
 // dnsTCPSession services DNS requests sent over TCP.
 type dnsTCPSession struct {
 	m *Manager
@@ -585,6 +615,9 @@ func (m *Manager) Down() error {
 	if err := m.os.Close(); err != nil {
 		return err
 	}
+	if m.eventClient != nil {
+		m.eventClient.Close()
+	}
 	m.resolver.Close()
 	return nil
 }
@@ -605,7 +638,7 @@ func CleanUp(logf logger.Logf, netMon *netmon.Monitor, bus *eventbus.Bus, health
 	if !buildfeatures.HasDNS {
 		return
 	}
-	oscfg, err := NewOSConfigurator(logf, health, policyclient.Get(), nil, interfaceName)
+	oscfg, err := NewOSConfigurator(logf, health, bus, policyclient.Get(), nil, interfaceName)
 	if err != nil {
 		logf("creating dns cleanup: %v", err)
 		return
@@ -613,12 +646,10 @@ func CleanUp(logf logger.Logf, netMon *netmon.Monitor, bus *eventbus.Bus, health
 	d := &tsdial.Dialer{Logf: logf}
 	d.SetNetMon(netMon)
 	d.SetBus(bus)
-	dns := NewManager(logf, oscfg, health, d, nil, nil, runtime.GOOS)
+	dns := NewManager(logf, oscfg, health, d, nil, nil, runtime.GOOS, bus)
 	if err := dns.Down(); err != nil {
 		logf("dns down: %v", err)
 	}
 }
 
-var (
-	metricDNSQueryErrorQueue = clientmetric.NewCounter("dns_query_local_error_queue")
-)
+var metricDNSQueryErrorQueue = clientmetric.NewCounter("dns_query_local_error_queue")

net/dns/manager_darwin.go

@@ -13,14 +13,15 @@ import (
 	"tailscale.com/net/dns/resolvconffile"
 	"tailscale.com/net/tsaddr"
 	"tailscale.com/types/logger"
+	"tailscale.com/util/eventbus"
 	"tailscale.com/util/mak"
 	"tailscale.com/util/syspolicy/policyclient"
 )
 
 // NewOSConfigurator creates a new OS configurator.
 //
-// The health tracker and the knobs may be nil and are ignored on this platform.
-func NewOSConfigurator(logf logger.Logf, _ *health.Tracker, _ policyclient.Client, _ *controlknobs.Knobs, ifName string) (OSConfigurator, error) {
+// The health tracker, bus and the knobs may be nil and are ignored on this platform.
+func NewOSConfigurator(logf logger.Logf, _ *health.Tracker, _ *eventbus.Bus, _ policyclient.Client, _ *controlknobs.Knobs, ifName string) (OSConfigurator, error) {
 	return &darwinConfigurator{logf: logf, ifName: ifName}, nil
 }
 

net/dns/manager_default.go

@@ -9,12 +9,13 @@ import (
 	"tailscale.com/control/controlknobs"
 	"tailscale.com/health"
 	"tailscale.com/types/logger"
+	"tailscale.com/util/eventbus"
 	"tailscale.com/util/syspolicy/policyclient"
 )
 
 // NewOSConfigurator creates a new OS configurator.
 //
 // The health tracker and the knobs may be nil and are ignored on this platform.
-func NewOSConfigurator(logger.Logf, *health.Tracker, policyclient.Client, *controlknobs.Knobs, string) (OSConfigurator, error) {
+func NewOSConfigurator(logger.Logf, *health.Tracker, *eventbus.Bus, policyclient.Client, *controlknobs.Knobs, string) (OSConfigurator, error) {
 	return NewNoopManager()
 }

net/dns/manager_freebsd.go

@@ -10,16 +10,17 @@ import (
 	"tailscale.com/control/controlknobs"
 	"tailscale.com/health"
 	"tailscale.com/types/logger"
+	"tailscale.com/util/eventbus"
 	"tailscale.com/util/syspolicy/policyclient"
 )
 
 // NewOSConfigurator creates a new OS configurator.
 //
 // The health tracker may be nil; the knobs may be nil and are ignored on this platform.
-func NewOSConfigurator(logf logger.Logf, health *health.Tracker, _ policyclient.Client, _ *controlknobs.Knobs, _ string) (OSConfigurator, error) {
+func NewOSConfigurator(logf logger.Logf, health *health.Tracker, bus *eventbus.Bus, _ policyclient.Client, _ *controlknobs.Knobs, _ string) (OSConfigurator, error) {
 	bs, err := os.ReadFile("/etc/resolv.conf")
 	if os.IsNotExist(err) {
-		return newDirectManager(logf, health), nil
+		return newDirectManager(logf, health, bus), nil
 	}
 	if err != nil {
 		return nil, fmt.Errorf("reading /etc/resolv.conf: %w", err)
@@ -29,16 +30,16 @@ func NewOSConfigurator(logf logger.Logf, health *health.Tracker, _ policyclient.
 	case "resolvconf":
 		switch resolvconfStyle() {
 		case "":
-			return newDirectManager(logf, health), nil
+			return newDirectManager(logf, health, bus), nil
 		case "debian":
 			return newDebianResolvconfManager(logf)
 		case "openresolv":
 			return newOpenresolvManager(logf)
 		default:
 			logf("[unexpected] got unknown flavor of resolvconf %q, falling back to direct manager", resolvconfStyle())
-			return newDirectManager(logf, health), nil
+			return newDirectManager(logf, health, bus), nil
 		}
 	default:
-		return newDirectManager(logf, health), nil
+		return newDirectManager(logf, health, bus), nil
 	}
 }

net/dns/manager_linux.go

@@ -21,6 +21,7 @@ import (
 	"tailscale.com/net/netaddr"
 	"tailscale.com/types/logger"
 	"tailscale.com/util/clientmetric"
+	"tailscale.com/util/eventbus"
 	"tailscale.com/util/syspolicy/policyclient"
 	"tailscale.com/version/distro"
 )
@@ -63,7 +64,7 @@ var (
 // NewOSConfigurator created a new OS configurator.
 //
 // The health tracker may be nil; the knobs may be nil and are ignored on this platform.
-func NewOSConfigurator(logf logger.Logf, health *health.Tracker, _ policyclient.Client, _ *controlknobs.Knobs, interfaceName string) (ret OSConfigurator, err error) {
+func NewOSConfigurator(logf logger.Logf, health *health.Tracker, bus *eventbus.Bus, _ policyclient.Client, _ *controlknobs.Knobs, interfaceName string) (ret OSConfigurator, err error) {
 	if !buildfeatures.HasDNS || distro.Get() == distro.JetKVM {
 		return NewNoopManager()
 	}
@@ -100,7 +101,7 @@ func NewOSConfigurator(logf logger.Logf, health *health.Tracker, _ policyclient.
 	logf("dns: using %q mode", mode)
 	switch mode {
 	case "direct":
-		return newDirectManagerOnFS(logf, health, env.fs), nil
+		return newDirectManagerOnFS(logf, health, bus, env.fs), nil
 	case "systemd-resolved":
 		if f, ok := optNewResolvedManager.GetOk(); ok {
 			return f(logf, health, interfaceName)
@@ -119,7 +120,7 @@ func NewOSConfigurator(logf logger.Logf, health *health.Tracker, _ policyclient.
 		logf("[unexpected] detected unknown DNS mode %q, using direct manager as last resort", mode)
 	}
 
-	return newDirectManagerOnFS(logf, health, env.fs), nil
+	return newDirectManagerOnFS(logf, health, bus, env.fs), nil
 }
 
 // newOSConfigEnv are the funcs newOSConfigurator needs, pulled out for testing.

net/dns/manager_openbsd.go

@@ -11,6 +11,7 @@ import (
 	"tailscale.com/control/controlknobs"
 	"tailscale.com/health"
 	"tailscale.com/types/logger"
+	"tailscale.com/util/eventbus"
 	"tailscale.com/util/syspolicy/policyclient"
 )
 
@@ -25,8 +26,8 @@ func (kv kv) String() string {
 // NewOSConfigurator created a new OS configurator.
 //
 // The health tracker may be nil; the knobs may be nil and are ignored on this platform.
-func NewOSConfigurator(logf logger.Logf, health *health.Tracker, _ policyclient.Client, _ *controlknobs.Knobs, interfaceName string) (OSConfigurator, error) {
-	return newOSConfigurator(logf, health, interfaceName,
+func NewOSConfigurator(logf logger.Logf, health *health.Tracker, bus *eventbus.Bus, _ policyclient.Client, _ *controlknobs.Knobs, interfaceName string) (OSConfigurator, error) {
+	return newOSConfigurator(logf, health, bus, interfaceName,
 		newOSConfigEnv{
 			rcIsResolvd: rcIsResolvd,
 			fs:          directFS{},
@@ -39,7 +40,7 @@ type newOSConfigEnv struct {
 	rcIsResolvd func(resolvConfContents []byte) bool
 }
 
-func newOSConfigurator(logf logger.Logf, health *health.Tracker, interfaceName string, env newOSConfigEnv) (ret OSConfigurator, err error) {
+func newOSConfigurator(logf logger.Logf, health *health.Tracker, bus *eventbus.Bus, interfaceName string, env newOSConfigEnv) (ret OSConfigurator, err error) {
 	var debug []kv
 	dbg := func(k, v string) {
 		debug = append(debug, kv{k, v})
@@ -54,7 +55,7 @@ func newOSConfigurator(logf logger.Logf, health *health.Tracker, interfaceName s
 	bs, err := env.fs.ReadFile(resolvConf)
 	if os.IsNotExist(err) {
 		dbg("rc", "missing")
-		return newDirectManager(logf, health), nil
+		return newDirectManager(logf, health, bus), nil
 	}
 	if err != nil {
 		return nil, fmt.Errorf("reading /etc/resolv.conf: %w", err)
@@ -66,7 +67,7 @@ func newOSConfigurator(logf logger.Logf, health *health.Tracker, interfaceName s
 	}
 
 	dbg("resolvd", "missing")
-	return newDirectManager(logf, health), nil
+	return newDirectManager(logf, health, bus), nil
 }
 
 func rcIsResolvd(resolvConfContents []byte) bool {

net/dns/manager_plan9.go

@@ -20,11 +20,12 @@ import (
 	"tailscale.com/control/controlknobs"
 	"tailscale.com/health"
 	"tailscale.com/types/logger"
+	"tailscale.com/util/eventbus"
 	"tailscale.com/util/set"
 	"tailscale.com/util/syspolicy/policyclient"
 )
 
-func NewOSConfigurator(logf logger.Logf, ht *health.Tracker, _ policyclient.Client, knobs *controlknobs.Knobs, interfaceName string) (OSConfigurator, error) {
+func NewOSConfigurator(logf logger.Logf, ht *health.Tracker, _ *eventbus.Bus, _ policyclient.Client, knobs *controlknobs.Knobs, interfaceName string) (OSConfigurator, error) {
 	return &plan9DNSManager{
 		logf:  logf,
 		ht:    ht,

net/dns/manager_solaris.go

@@ -7,9 +7,10 @@ import (
 	"tailscale.com/control/controlknobs"
 	"tailscale.com/health"
 	"tailscale.com/types/logger"
+	"tailscale.com/util/eventbus"
 	"tailscale.com/util/syspolicy/policyclient"
 )
 
-func NewOSConfigurator(logf logger.Logf, health *health.Tracker, _ policyclient.Client, _ *controlknobs.Knobs, iface string) (OSConfigurator, error) {
-	return newDirectManager(logf, health), nil
+func NewOSConfigurator(logf logger.Logf, health *health.Tracker, bus *eventbus.Bus, _ policyclient.Client, _ *controlknobs.Knobs, iface string) (OSConfigurator, error) {
+	return newDirectManager(logf, health, bus), nil
 }

net/dns/manager_tcp_test.go

@@ -93,7 +93,7 @@ func TestDNSOverTCP(t *testing.T) {
 	bus := eventbustest.NewBus(t)
 	dialer := tsdial.NewDialer(netmon.NewStatic())
 	dialer.SetBus(bus)
-	m := NewManager(t.Logf, &f, health.NewTracker(bus), dialer, nil, nil, "")
+	m := NewManager(t.Logf, &f, health.NewTracker(bus), dialer, nil, nil, "", bus)
 	m.resolver.TestOnlySetHook(f.SetResolver)
 	m.Set(Config{
 		Hosts: hosts(
@@ -181,7 +181,7 @@ func TestDNSOverTCP_TooLarge(t *testing.T) {
 	bus := eventbustest.NewBus(t)
 	dialer := tsdial.NewDialer(netmon.NewStatic())
 	dialer.SetBus(bus)
-	m := NewManager(log, &f, health.NewTracker(bus), dialer, nil, nil, "")
+	m := NewManager(log, &f, health.NewTracker(bus), dialer, nil, nil, "", bus)
 	m.resolver.TestOnlySetHook(f.SetResolver)
 	m.Set(Config{
 		Hosts:         hosts("andrew.ts.com.", "1.2.3.4"),

net/dns/manager_test.go

@@ -6,9 +6,11 @@ package dns
 import (
 	"errors"
 	"net/netip"
+	"reflect"
 	"runtime"
 	"strings"
 	"testing"
+	"testing/synctest"
 
 	"github.com/google/go-cmp/cmp"
 	"github.com/google/go-cmp/cmp/cmpopts"
@@ -936,7 +938,7 @@ func TestManager(t *testing.T) {
 			bus := eventbustest.NewBus(t)
 			dialer := tsdial.NewDialer(netmon.NewStatic())
 			dialer.SetBus(bus)
-			m := NewManager(t.Logf, &f, health.NewTracker(bus), dialer, nil, knobs, goos)
+			m := NewManager(t.Logf, &f, health.NewTracker(bus), dialer, nil, knobs, goos, bus)
 			m.resolver.TestOnlySetHook(f.SetResolver)
 
 			if err := m.Set(test.in); err != nil {
@@ -1045,7 +1047,7 @@ func TestConfigRecompilation(t *testing.T) {
 	bus := eventbustest.NewBus(t)
 	dialer := tsdial.NewDialer(netmon.NewStatic())
 	dialer.SetBus(bus)
-	m := NewManager(t.Logf, f, health.NewTracker(bus), dialer, nil, nil, "darwin")
+	m := NewManager(t.Logf, f, health.NewTracker(bus), dialer, nil, nil, "darwin", bus)
 
 	var managerConfig *resolver.Config
 	m.resolver.TestOnlySetHook(func(cfg resolver.Config) {
@@ -1078,3 +1080,39 @@ func TestConfigRecompilation(t *testing.T) {
 		t.Fatalf("Want non nil managerConfig.  Got nil")
 	}
 }
+
+func TestTrampleRetrample(t *testing.T) {
+	synctest.Test(t, func(t *testing.T) {
+		f := &fakeOSConfigurator{}
+		f.BaseConfig = OSConfig{
+			Nameservers: mustIPs("1.1.1.1"),
+		}
+
+		config := Config{
+			Routes:        upstreams("ts.net", "69.4.2.0", "foo.ts.net", ""),
+			SearchDomains: fqdns("foo.ts.net"),
+		}
+
+		bus := eventbustest.NewBus(t)
+		dialer := tsdial.NewDialer(netmon.NewStatic())
+		dialer.SetBus(bus)
+		m := NewManager(t.Logf, f, health.NewTracker(bus), dialer, nil, nil, "linux", bus)
+
+		// Initial set should error out and store the config
+		if err := m.Set(config); err != nil {
+			t.Fatalf("Want nil error. Got non-nil")
+		}
+
+		// Set no config
+		f.OSConfig = OSConfig{}
+
+		inj := eventbustest.NewInjector(t, bus)
+		eventbustest.Inject(inj, TrampleDNS{})
+		synctest.Wait()
+
+		t.Logf("OSConfig: %+v", f.OSConfig)
+		if reflect.DeepEqual(f.OSConfig, OSConfig{}) {
+			t.Errorf("Expected config to be set, got nil config")
+		}
+	})
+}

net/dns/manager_windows.go

@@ -29,6 +29,7 @@ import (
 	"tailscale.com/syncs"
 	"tailscale.com/types/logger"
 	"tailscale.com/util/dnsname"
+	"tailscale.com/util/eventbus"
 	"tailscale.com/util/syspolicy/pkey"
 	"tailscale.com/util/syspolicy/policyclient"
 	"tailscale.com/util/syspolicy/ptype"
@@ -57,8 +58,8 @@ type windowsManager struct {
 
 // NewOSConfigurator created a new OS configurator.
 //
-// The health tracker and the knobs may be nil.
-func NewOSConfigurator(logf logger.Logf, health *health.Tracker, polc policyclient.Client, knobs *controlknobs.Knobs, interfaceName string) (OSConfigurator, error) {
+// The health tracker, eventbus and the knobs may be nil.
+func NewOSConfigurator(logf logger.Logf, health *health.Tracker, bus *eventbus.Bus, polc policyclient.Client, knobs *controlknobs.Knobs, interfaceName string) (OSConfigurator, error) {
 	if polc == nil {
 		panic("nil policyclient.Client")
 	}
@@ -163,7 +164,7 @@ func setTailscaleHosts(logf logger.Logf, prevHostsFile []byte, hosts []*HostEntr
 		header = "# TailscaleHostsSectionStart"
 		footer = "# TailscaleHostsSectionEnd"
 	)
-	var comments = []string{
+	comments := []string{
 		"# This section contains MagicDNS entries for Tailscale.",
 		"# Do not edit this section manually.",
 	}

net/dns/manager_windows_test.go

@@ -134,7 +134,7 @@ func TestManagerWindowsGPCopy(t *testing.T) {
 	}
 	defer delIfKey()
 
-	cfg, err := NewOSConfigurator(logf, nil, policyclient.NoPolicyClient{}, nil, fakeInterface.String())
+	cfg, err := NewOSConfigurator(logf, nil, nil, policyclient.NoPolicyClient{}, nil, fakeInterface.String())
 	if err != nil {
 		t.Fatalf("NewOSConfigurator: %v\n", err)
 	}
@@ -263,7 +263,7 @@ func runTest(t *testing.T, isLocal bool) {
 	}
 	defer delIfKey()
 
-	cfg, err := NewOSConfigurator(logf, nil, policyclient.NoPolicyClient{}, nil, fakeInterface.String())
+	cfg, err := NewOSConfigurator(logf, nil, nil, policyclient.NoPolicyClient{}, nil, fakeInterface.String())
 	if err != nil {
 		t.Fatalf("NewOSConfigurator: %v\n", err)
 	}

net/dns/wsl_windows.go

@@ -76,7 +76,7 @@ func (wm *wslManager) SetDNS(cfg OSConfig) error {
 	}
 	managers := make(map[string]*directManager)
 	for _, distro := range distros {
-		managers[distro] = newDirectManagerOnFS(wm.logf, wm.health, wslFS{
+		managers[distro] = newDirectManagerOnFS(wm.logf, wm.health, nil, wslFS{
 			user:   "root",
 			distro: distro,
 		})

wgengine/userspace.go

@@ -387,7 +387,7 @@ func NewUserspaceEngine(logf logger.Logf, conf Config) (_ Engine, reterr error)
 	conf.Dialer.SetTUNName(tunName)
 	conf.Dialer.SetNetMon(e.netMon)
 	conf.Dialer.SetBus(e.eventBus)
-	e.dns = dns.NewManager(logf, conf.DNS, e.health, conf.Dialer, fwdDNSLinkSelector{e, tunName}, conf.ControlKnobs, runtime.GOOS)
+	e.dns = dns.NewManager(logf, conf.DNS, e.health, conf.Dialer, fwdDNSLinkSelector{e, tunName}, conf.ControlKnobs, runtime.GOOS, e.eventBus)
 
 	// TODO: there's probably a better place for this
 	sockstats.SetNetMon(e.netMon)