Improve shutdown behaviour (fixes #891)

Author: neilalexander

cmd/yggdrasil/main.go

@@ -14,6 +14,7 @@ import (
 	"os/signal"
 	"regexp"
 	"strings"
+	"sync"
 	"syscall"
 
 	"golang.org/x/text/encoding/unicode"
@@ -183,8 +184,7 @@ func getArgs() yggArgs {
 }
 
 // The main function is responsible for configuring and starting Yggdrasil.
-func run(args yggArgs, ctx context.Context, done chan struct{}) {
-	defer close(done)
+func run(args yggArgs, ctx context.Context) {
 	// Create a new logger that logs output to stdout.
 	var logger *log.Logger
 	switch args.logto {
@@ -371,14 +371,11 @@ func run(args yggArgs, ctx context.Context, done chan struct{}) {
 	logger.Infof("Your public key is %s", hex.EncodeToString(public[:]))
 	logger.Infof("Your IPv6 address is %s", address.String())
 	logger.Infof("Your IPv6 subnet is %s", subnet.String())
-	// Catch interrupts from the operating system to exit gracefully.
+
+	// Block until we are told to shut down.
 	<-ctx.Done()
-	// Capture the service being stopped on Windows.
-	minwinsvc.SetOnExit(n.shutdown)
-	n.shutdown()
-}
 
-func (n *node) shutdown() {
+	// Shut down the node.
 	_ = n.admin.Stop()
 	_ = n.multicast.Stop()
 	_ = n.tun.Stop()
@@ -387,24 +384,19 @@ func (n *node) shutdown() {
 
 func main() {
 	args := getArgs()
-	hup := make(chan os.Signal, 1)
-	//signal.Notify(hup, os.Interrupt, syscall.SIGHUP)
-	term := make(chan os.Signal, 1)
-	signal.Notify(term, os.Interrupt, syscall.SIGTERM)
-	for {
-		done := make(chan struct{})
-		ctx, cancel := context.WithCancel(context.Background())
-		go run(args, ctx, done)
-		select {
-		case <-hup:
-			cancel()
-			<-done
-		case <-term:
-			cancel()
-			<-done
-			return
-		case <-done:
-			return
-		}
-	}
+
+	// Catch interrupts from the operating system to exit gracefully.
+	ctx, cancel := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
+
+	// Capture the service being stopped on Windows.
+	minwinsvc.SetOnExit(cancel)
+
+	// Start the node, block and then wait for it to shut down.
+	var wg sync.WaitGroup
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		run(args, ctx)
+	}()
+	wg.Wait()
 }