cmd/cli: ensure DNS goroutines terminated before self-uninstall

Otherwise, these goroutines could mess up with what resetDNS function
do, reverting DHCP DNS settings to ctrld listeners.

cmd/cli/cli.go

@@ -1135,13 +1135,14 @@ func run(appCallback *AppCallback, stopCh chan struct{}) {
 	}
 	waitCh := make(chan struct{})
 	p := &prog{
-		waitCh:       waitCh,
-		stopCh:       stopCh,
-		reloadCh:     make(chan struct{}),
-		reloadDoneCh: make(chan struct{}),
-		apiReloadCh:  make(chan *ctrld.Config),
-		cfg:          &cfg,
-		appCallback:  appCallback,
+		waitCh:           waitCh,
+		stopCh:           stopCh,
+		reloadCh:         make(chan struct{}),
+		reloadDoneCh:     make(chan struct{}),
+		dnsWatcherStopCh: make(chan struct{}),
+		apiReloadCh:      make(chan *ctrld.Config),
+		cfg:              &cfg,
+		appCallback:      appCallback,
 	}
 	if homedir == "" {
 		if dir, err := userHomeDir(); err == nil {
@@ -1232,7 +1233,11 @@ func run(appCallback *AppCallback, stopCh chan struct{}) {
 			}
 
 			cdLogger := mainLog.Load().With().Str("mode", "cd").Logger()
-			_ = uninstallIfInvalidCdUID(err, p, cdLogger)
+			// Performs self-uninstallation if the ControlD device does not exist.
+			var uer *controld.UtilityErrorResponse
+			if errors.As(err, &uer) && uer.ErrorField.Code == controld.InvalidConfigCode {
+				_ = uninstallInvalidCdUID(p, cdLogger, false)
+			}
 			cdLogger.Fatal().Err(err).Msg("failed to fetch resolver config")
 		}
 	}
@@ -2696,23 +2701,23 @@ func doValidateCdRemoteConfig(cdUID string) {
 	v = oldV
 }
 
-// uninstallIfInvalidCdUID performs self-uninstallation if the ControlD device does not exist.
-func uninstallIfInvalidCdUID(err error, p *prog, logger zerolog.Logger) bool {
-	var uer *controld.UtilityErrorResponse
-	if errors.As(err, &uer) && uer.ErrorField.Code == controld.InvalidConfigCode {
-		s, err := newService(p, svcConfig)
-		if err != nil {
-			logger.Warn().Err(err).Msg("failed to create new service")
-			return false
-		}
+// uninstallInvalidCdUID performs self-uninstallation because the ControlD device does not exist.
+func uninstallInvalidCdUID(p *prog, logger zerolog.Logger, doStop bool) bool {
+	s, err := newService(p, svcConfig)
+	if err != nil {
+		logger.Warn().Err(err).Msg("failed to create new service")
+		return false
+	}
 
-		p.resetDNS()
+	p.resetDNS()
 
-		tasks := []task{{s.Uninstall, true}}
-		if doTasks(tasks) {
-			logger.Info().Msg("uninstalled service")
-			return true
+	tasks := []task{{s.Uninstall, true}}
+	if doTasks(tasks) {
+		logger.Info().Msg("uninstalled service")
+		if doStop {
+			_ = s.Stop()
 		}
+		return true
 	}
 	return false
 }

cmd/cli/dns_proxy.go

@@ -863,7 +863,7 @@ func (p *prog) doSelfUninstall(answer *dns.Msg) {
 		p.checkingSelfUninstall = true
 		_, err := controld.FetchResolverConfig(cdUID, rootCmd.Version, cdDev)
 		logger.Debug().Msg("maximum number of refused queries reached, checking device status")
-		selfUninstall(err, p, logger)
+		selfUninstallCheck(err, p, logger)
 
 		if err != nil {
 			logger.Warn().Err(err).Msg("could not fetch resolver config")

cmd/cli/prog.go

@@ -22,6 +22,7 @@ import (
 	"time"
 
 	"github.com/kardianos/service"
+	"github.com/rs/zerolog"
 	"github.com/spf13/viper"
 	"tailscale.com/net/interfaces"
 	"tailscale.com/net/tsaddr"
@@ -67,18 +68,19 @@ var svcConfig = &service.Config{
 var useSystemdResolved = false
 
 type prog struct {
-	mu              sync.Mutex
-	waitCh          chan struct{}
-	stopCh          chan struct{}
-	reloadCh        chan struct{} // For Windows.
-	reloadDoneCh    chan struct{}
-	apiReloadCh     chan *ctrld.Config
-	logConn         net.Conn
-	cs              *controlServer
-	csSetDnsDone    chan struct{}
-	csSetDnsOk      bool
-	dnsWatchDogOnce sync.Once
-	dnsWg           sync.WaitGroup
+	mu               sync.Mutex
+	waitCh           chan struct{}
+	stopCh           chan struct{}
+	reloadCh         chan struct{} // For Windows.
+	reloadDoneCh     chan struct{}
+	apiReloadCh      chan *ctrld.Config
+	logConn          net.Conn
+	cs               *controlServer
+	csSetDnsDone     chan struct{}
+	csSetDnsOk       bool
+	dnsWatchDogOnce  sync.Once
+	dnsWg            sync.WaitGroup
+	dnsWatcherStopCh chan struct{}
 
 	cfg                  *ctrld.Config
 	localUpstreams       []string
@@ -261,7 +263,7 @@ func (p *prog) apiConfigReload() {
 		select {
 		case <-ticker.C:
 			resolverConfig, err := controld.FetchResolverConfig(cdUID, rootCmd.Version, cdDev)
-			selfUninstall(err, p, logger)
+			selfUninstallCheck(err, p, logger)
 			if err != nil {
 				logger.Warn().Err(err).Msg("could not fetch resolver config")
 				continue
@@ -650,6 +652,8 @@ func (p *prog) dnsWatchdog(iface *net.Interface, nameservers []string, allIfaces
 		logger := mainLog.Load().With().Str("iface", iface.Name).Logger()
 		for {
 			select {
+			case <-p.dnsWatcherStopCh:
+				return
 			case <-p.stopCh:
 				mainLog.Load().Debug().Msg("stop dns watchdog")
 				return
@@ -975,3 +979,16 @@ func dnsChanged(iface *net.Interface, nameservers []string) bool {
 	slices.Sort(curNameservers)
 	return !slices.Equal(curNameservers, nameservers)
 }
+
+// selfUninstallCheck checks if the error dues to controld.InvalidConfigCode, perform self-uninstall then.
+func selfUninstallCheck(uninstallErr error, p *prog, logger zerolog.Logger) {
+	var uer *controld.UtilityErrorResponse
+	if errors.As(uninstallErr, &uer) && uer.ErrorField.Code == controld.InvalidConfigCode {
+		// Ensure all DNS watchers goroutine are terminated, so it won't mess up with self-uninstall.
+		close(p.dnsWatcherStopCh)
+		p.dnsWg.Wait()
+
+		// Perform self-uninstall now.
+		selfUninstall(p, logger)
+	}
+}

cmd/cli/resolvconf.go

@@ -34,6 +34,8 @@ func (p *prog) watchResolvConf(iface *net.Interface, ns []netip.Addr, setDnsFn f
 
 	for {
 		select {
+		case <-p.dnsWatcherStopCh:
+			return
 		case <-p.stopCh:
 			mainLog.Load().Debug().Msgf("stopping watcher for %s", resolvConfPath)
 			return

cmd/cli/self_kill_others.go

@@ -8,8 +8,8 @@ import (
 	"github.com/rs/zerolog"
 )
 
-func selfUninstall(err error, p *prog, logger zerolog.Logger) {
-	if uninstallIfInvalidCdUID(err, p, logger) {
+func selfUninstall(p *prog, logger zerolog.Logger) {
+	if uninstallInvalidCdUID(p, logger, false) {
 		logger.Warn().Msgf("service was uninstalled because device %q does not exist", cdUID)
 		os.Exit(0)
 	}

cmd/cli/self_kill_unix.go

@@ -3,54 +3,43 @@
 package cli
 
 import (
-	"errors"
 	"fmt"
 	"os"
 	"os/exec"
 	"runtime"
 	"syscall"
 
-	"github.com/Control-D-Inc/ctrld/internal/controld"
 	"github.com/rs/zerolog"
 )
 
-func selfUninstall(uninstallErr error, p *prog, logger zerolog.Logger) {
-	var uer *controld.UtilityErrorResponse
-	if errors.As(uninstallErr, &uer) && uer.ErrorField.Code == controld.InvalidConfigCode {
-		if runtime.GOOS == "linux" {
-			s, err := newService(p, svcConfig)
-			if err != nil {
-				logger.Warn().Err(err).Msg("failed to create new service")
-			} else {
-				selfUninstallLinux(uninstallErr, p, logger)
-				_ = s.Stop()
-				os.Exit(0)
-			}
-		}
+func selfUninstall(p *prog, logger zerolog.Logger) {
+	if runtime.GOOS == "linux" {
+		selfUninstallLinux(p, logger)
+	}
 
-		bin, err := os.Executable()
-		if err != nil {
-			logger.Fatal().Err(err).Msg("could not determine executable")
-		}
-		args := []string{"uninstall"}
-		if !deactivationPinNotSet() {
-			args = append(args, fmt.Sprintf("--pin=%d", cdDeactivationPin))
-		}
-		cmd := exec.Command(bin, args...)
-		cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
-		if err := cmd.Start(); err != nil {
-			logger.Fatal().Err(err).Msg("could not start self uninstall command")
-		}
-		cmd.Stdout = os.Stdout
-		cmd.Stderr = os.Stderr
+	bin, err := os.Executable()
+	if err != nil {
+		logger.Fatal().Err(err).Msg("could not determine executable")
+	}
+	args := []string{"uninstall"}
+	if !deactivationPinNotSet() {
+		args = append(args, fmt.Sprintf("--pin=%d", cdDeactivationPin))
+	}
+	cmd := exec.Command(bin, args...)
+	cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
+	if err := cmd.Start(); err != nil {
+		logger.Fatal().Err(err).Msg("could not start self uninstall command")
+	}
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	logger.Warn().Msgf("service was uninstalled because device %q does not exist", cdUID)
+	_ = cmd.Wait()
+	os.Exit(0)
+}
+
+func selfUninstallLinux(p *prog, logger zerolog.Logger) {
+	if uninstallInvalidCdUID(p, logger, true) {
 		logger.Warn().Msgf("service was uninstalled because device %q does not exist", cdUID)
-		_ = cmd.Wait()
 		os.Exit(0)
 	}
 }
-
-func selfUninstallLinux(err error, p *prog, logger zerolog.Logger) {
-	if uninstallIfInvalidCdUID(err, p, logger) {
-		logger.Warn().Msgf("service was uninstalled because device %q does not exist", cdUID)
-	}
-}