Get and set settings for DNS

internal/dns/loop.go

@@ -18,11 +18,14 @@ type Looper interface {
 	Restart()
 	Start()
 	Stop()
+	GetSettings() (settings settings.DNS)
+	SetSettings(settings settings.DNS)
 }
 
 type looper struct {
 	conf             Configurator
 	settings         settings.DNS
+	settingsMutex    sync.RWMutex
 	logger           logging.Logger
 	streamMerger     command.StreamMerger
 	uid              int
@@ -30,6 +33,9 @@ type looper struct {
 	restart          chan struct{}
 	start            chan struct{}
 	stop             chan struct{}
+	updateTicker     chan struct{}
+	tickerReady      bool
+	tickerReadyMutex sync.Mutex
 }
 
 func NewLooper(conf Configurator, settings settings.DNS, logger logging.Logger,
@@ -44,6 +50,7 @@ func NewLooper(conf Configurator, settings settings.DNS, logger logging.Logger,
 		restart:      make(chan struct{}),
 		start:        make(chan struct{}),
 		stop:         make(chan struct{}),
+		updateTicker: make(chan struct{}),
 	}
 }
 
@@ -51,6 +58,35 @@ func (l *looper) Restart() { l.restart <- struct{}{} }
 func (l *looper) Start()   { l.start <- struct{}{} }
 func (l *looper) Stop()    { l.stop <- struct{}{} }
 
+func (l *looper) GetSettings() (settings settings.DNS) {
+	l.settingsMutex.RLock()
+	defer l.settingsMutex.RUnlock()
+	return l.settings
+}
+
+func (l *looper) SetSettings(settings settings.DNS) {
+	l.settingsMutex.Lock()
+	defer l.settingsMutex.Unlock()
+	updatePeriodDiffers := l.settings.UpdatePeriod != settings.UpdatePeriod
+	l.settings = settings
+	l.settingsMutex.Unlock()
+	if updatePeriodDiffers {
+		l.updateTicker <- struct{}{}
+	}
+}
+
+func (l *looper) isEnabled() bool {
+	l.settingsMutex.RLock()
+	defer l.settingsMutex.RUnlock()
+	return l.settings.Enabled
+}
+
+func (l *looper) setEnabled(enabled bool) {
+	l.settingsMutex.Lock()
+	defer l.settingsMutex.Unlock()
+	l.settings.Enabled = enabled
+}
+
 func (l *looper) logAndWait(ctx context.Context, err error) {
 	l.logger.Warn(err)
 	l.logger.Info("attempting restart in 10 seconds")
@@ -82,23 +118,25 @@ func (l *looper) Run(ctx context.Context, wg *sync.WaitGroup) {
 	var unboundCancel context.CancelFunc = func() {}
 	var waitError chan error
 	triggeredRestart := false
-	l.settings.Enabled = true
+	l.setEnabled(true)
 	for ctx.Err() == nil {
-		for !l.settings.Enabled {
+		for !l.isEnabled() {
 			// wait for a signal to re-enable
 			select {
 			case <-l.stop:
 				l.logger.Info("already disabled")
 			case <-l.restart:
-				l.settings.Enabled = true
+				l.setEnabled(true)
 			case <-l.start:
-				l.settings.Enabled = true
+				l.setEnabled(true)
 			case <-ctx.Done():
 				unboundCancel()
 				return
 			}
 		}
 
+		settings := l.GetSettings()
+
 		// Setup
 		if err := l.conf.DownloadRootHints(l.uid, l.gid); err != nil {
 			l.logAndWait(ctx, err)
@@ -108,7 +146,7 @@ func (l *looper) Run(ctx context.Context, wg *sync.WaitGroup) {
 			l.logAndWait(ctx, err)
 			continue
 		}
-		if err := l.conf.MakeUnboundConf(l.settings, l.uid, l.gid); err != nil {
+		if err := l.conf.MakeUnboundConf(settings, l.uid, l.gid); err != nil {
 			l.logAndWait(ctx, err)
 			continue
 		}
@@ -120,7 +158,7 @@ func (l *looper) Run(ctx context.Context, wg *sync.WaitGroup) {
 			close(waitError)
 		}
 		unboundCtx, unboundCancel = context.WithCancel(context.Background())
-		stream, waitFn, err := l.conf.Start(unboundCtx, l.settings.VerbosityDetailsLevel)
+		stream, waitFn, err := l.conf.Start(unboundCtx, settings.VerbosityDetailsLevel)
 		if err != nil {
 			unboundCancel()
 			l.fallbackToUnencryptedDNS()
@@ -131,7 +169,7 @@ func (l *looper) Run(ctx context.Context, wg *sync.WaitGroup) {
 		// Started successfully
 		go l.streamMerger.Merge(unboundCtx, stream, command.MergeName("unbound"))
 		l.conf.UseDNSInternally(net.IP{127, 0, 0, 1})                                                  // use Unbound
-		if err := l.conf.UseDNSSystemWide(net.IP{127, 0, 0, 1}, l.settings.KeepNameserver); err != nil { // use Unbound
+		if err := l.conf.UseDNSSystemWide(net.IP{127, 0, 0, 1}, settings.KeepNameserver); err != nil { // use Unbound
 			l.logger.Error(err)
 		}
 		if err := l.conf.WaitForUnbound(); err != nil {
@@ -167,7 +205,7 @@ func (l *looper) Run(ctx context.Context, wg *sync.WaitGroup) {
 				unboundCancel()
 				<-waitError
 				close(waitError)
-				l.settings.Enabled = false
+				l.setEnabled(false)
 				stayHere = false
 			case err := <-waitError: // unexpected error
 				close(waitError)
@@ -182,25 +220,27 @@ func (l *looper) Run(ctx context.Context, wg *sync.WaitGroup) {
 }
 
 func (l *looper) fallbackToUnencryptedDNS() {
+	settings := l.GetSettings()
+
 	// Try with user provided plaintext ip address
-	targetIP := l.settings.PlaintextAddress
+	targetIP := settings.PlaintextAddress
 	if targetIP != nil {
 		l.logger.Info("falling back on plaintext DNS at address %s", targetIP)
 		l.conf.UseDNSInternally(targetIP)
-		if err := l.conf.UseDNSSystemWide(targetIP, l.settings.KeepNameserver); err != nil {
+		if err := l.conf.UseDNSSystemWide(targetIP, settings.KeepNameserver); err != nil {
 			l.logger.Error(err)
 		}
 		return
 	}
 
 	// Try with any IPv4 address from the providers chosen
-	for _, provider := range l.settings.Providers {
+	for _, provider := range settings.Providers {
 		data := constants.DNSProviderMapping()[provider]
 		for _, targetIP = range data.IPs {
 			if targetIP.To4() != nil {
 				l.logger.Info("falling back on plaintext DNS at address %s", targetIP)
 				l.conf.UseDNSInternally(targetIP)
-				if err := l.conf.UseDNSSystemWide(targetIP, l.settings.KeepNameserver); err != nil {
+				if err := l.conf.UseDNSSystemWide(targetIP, settings.KeepNameserver); err != nil {
 					l.logger.Error(err)
 				}
 				return
@@ -209,21 +249,33 @@ func (l *looper) fallbackToUnencryptedDNS() {
 	}
 
 	// No IPv4 address found
-	l.logger.Error("no ipv4 DNS address found for providers %s", l.settings.Providers)
+	l.logger.Error("no ipv4 DNS address found for providers %s", settings.Providers)
 }
 
 func (l *looper) RunRestartTicker(ctx context.Context) {
-	if l.settings.UpdatePeriod == 0 {
+	l.tickerReadyMutex.Lock()
-		return
+	l.tickerReady = true
+	l.tickerReadyMutex.Unlock()
+	var ticker *time.Ticker = nil
+	settings := l.GetSettings()
+	if settings.UpdatePeriod > 0 {
+		ticker = time.NewTicker(settings.UpdatePeriod)
 	}
-	ticker := time.NewTicker(l.settings.UpdatePeriod)
 	for {
 		select {
 		case <-ctx.Done():
+			if ticker != nil {
 				ticker.Stop()
+			}
 			return
 		case <-ticker.C:
 			l.restart <- struct{}{}
+		case <-l.updateTicker:
+			if ticker != nil {
+				ticker.Stop()
+			}
+			period := l.GetSettings().UpdatePeriod
+			ticker = time.NewTicker(period)
 		}
 	}
 }