Run raSender with single goroutine

The current structure is unnecessarily complicated. Fix it.

Signed-off-by: Yutaro Hayakawa <yutaro.hayakawa@isovalent.com>

ra_sender.go

@@ -7,7 +7,6 @@ import (
 	"log/slog"
 	"net/netip"
 	"reflect"
-	"sync"
 	"time"
 
 	"github.com/mdlayher/ndp"
@@ -20,14 +19,9 @@ type raSender struct {
 
 	initialConfig *InterfaceConfig
 	reloadCh      chan *InterfaceConfig
-	stopCh        any
+	stopCh        chan any
 	sock          rAdvSocket
-
-	childWg       *sync.WaitGroup
-	childReloadCh []chan *InterfaceConfig
-	childStopCh   []chan any
-
-	socketCtor rAdvSocketCtor
+	socketCtor    rAdvSocketCtor
 }
 
 func newRASender(initialConfig *InterfaceConfig, ctor rAdvSocketCtor, logger *slog.Logger) *raSender {
@@ -36,19 +30,19 @@ func newRASender(initialConfig *InterfaceConfig, ctor rAdvSocketCtor, logger *sl
 		initialConfig: initialConfig,
 		reloadCh:      make(chan *InterfaceConfig),
 		stopCh:        make(chan any),
-		childWg:       &sync.WaitGroup{},
-		childReloadCh: []chan *InterfaceConfig{},
-		childStopCh:   []chan any{},
 		socketCtor:    ctor,
 	}
 }
 
 func (s *raSender) run(ctx context.Context) {
+	// The current desired configuration
+	config := s.initialConfig
+
 	// Create the socket
 	err := retry.Constant(ctx, time.Second, func(ctx context.Context) error {
 		var err error
 
-		s.sock, err = s.socketCtor(s.initialConfig.Name)
+		s.sock, err = s.socketCtor(config.Name)
 		if err != nil {
 			// These are the unrecoverable errors we're aware of now.
 			if errors.Is(err, unix.EPERM) || errors.Is(err, unix.EINVAL) {
@@ -64,59 +58,24 @@ func (s *raSender) run(ctx context.Context) {
 		return
 	}
 
-	s.spawnChild(ctx, s.runUnsolicitedRASender)
-	s.childWg.Wait()
-	s.sock.close()
-}
-
-func (s *raSender) reload(ctx context.Context, newConfig *InterfaceConfig) error {
-	for _, ch := range s.childReloadCh {
-		select {
-		case ch <- newConfig:
-		case <-ctx.Done():
-			return ctx.Err()
-		}
-	}
-	return nil
-}
-
-func (s *raSender) stop() {
-	for _, ch := range s.childStopCh {
-		close(ch)
-	}
-}
-
-func (s *raSender) spawnChild(ctx context.Context, f func(context.Context, chan *InterfaceConfig, chan any)) {
-	s.childWg.Add(1)
-	reloadCh := make(chan *InterfaceConfig)
-	stopCh := make(chan any)
-	s.childReloadCh = append(s.childReloadCh, reloadCh)
-	s.childStopCh = append(s.childStopCh, stopCh)
-	go f(ctx, reloadCh, stopCh)
-}
-
-func (s *raSender) runUnsolicitedRASender(ctx context.Context, reloadCh chan *InterfaceConfig, stopCh chan any) {
-	defer s.childWg.Done()
-
-	// The current desired configuration
-	config := s.initialConfig
-
 reload:
 	for {
 		msg := &ndp.RouterAdvertisement{
 			// TODO: Make this configurable
 			RouterLifetime: 1800 * time.Second,
 		}
 
+		// For unsolicited RA
 		ticker := time.NewTicker(time.Duration(config.RAIntervalMilliseconds) * time.Millisecond)
+
 		for {
 			select {
 			case <-ticker.C:
 				err := s.sock.sendRA(ctx, netip.IPv6LinkLocalAllNodes(), msg)
 				if err != nil {
 					continue
 				}
-			case newConfig := <-reloadCh:
+			case newConfig := <-s.reloadCh:
 				if reflect.DeepEqual(config, newConfig) {
 					s.logger.Info("No configuration change. Skip reloading.")
 					continue
@@ -126,11 +85,26 @@ reload:
 				continue reload
 			case <-ctx.Done():
 				s.logger.Info("Context is done. Stopping.")
-				return
-			case <-stopCh:
+				break reload
+			case <-s.stopCh:
 				s.logger.Info("Stop event received. Stopping.")
-				return
+				break reload
 			}
 		}
 	}
+
+	s.sock.close()
+}
+
+func (s *raSender) reload(ctx context.Context, newConfig *InterfaceConfig) error {
+	select {
+	case s.reloadCh <- newConfig:
+	case <-ctx.Done():
+		return ctx.Err()
+	}
+	return nil
+}
+
+func (s *raSender) stop() {
+	close(s.stopCh)
 }