cmd/tailscaled: graceful shutdown (#534)

Signed-off-by: Dmytro Shynkevych <dmytro@tailscale.com>

cmd/tailscaled/tailscaled.go

@@ -15,8 +15,10 @@ import (
 	"net/http"
 	"net/http/pprof"
 	"os"
+	"os/signal"
 	"runtime"
 	"runtime/debug"
+	"syscall"
 	"time"
 
 	"github.com/apenwarr/fixconsole"
@@ -27,6 +29,7 @@ import (
 	"tailscale.com/types/logger"
 	"tailscale.com/wgengine"
 	"tailscale.com/wgengine/magicsock"
+	"tailscale.com/wgengine/router"
 )
 
 // globalStateKey is the ipn.StateKey that tailscaled loads on
@@ -52,6 +55,7 @@ func main() {
 		defaultTunName = "tun"
 	}
 
+	cleanup := getopt.BoolLong("cleanup", 0, "clean up system state and exit")
 	fake := getopt.BoolLong("fake", 0, "fake tunnel+routing instead of tuntap")
 	debug := getopt.StringLong("debug", 0, "", "Address of debug server")
 	tunname := getopt.StringLong("tun", 0, defaultTunName, "tunnel interface name")
@@ -73,6 +77,11 @@ func main() {
 		log.Fatalf("too many non-flag arguments: %#v", getopt.Args()[0])
 	}
 
+	if *cleanup {
+		router.Cleanup(logf, *tunname)
+		return
+	}
+
 	if *statepath == "" {
 		log.Fatalf("--state is required")
 	}
@@ -98,6 +107,20 @@ func main() {
 	}
 	e = wgengine.NewWatchdog(e)
 
+	ctx, cancel := context.WithCancel(context.Background())
+	// Exit gracefully by cancelling the ipnserver context in most common cases:
+	// interrupted from the TTY or killed by a service manager.
+	go func() {
+		interrupt := make(chan os.Signal, 1)
+		signal.Notify(interrupt, syscall.SIGINT, syscall.SIGTERM)
+		select {
+		case <-interrupt:
+			cancel()
+		case <-ctx.Done():
+			// continue
+		}
+	}()
+
 	opts := ipnserver.Options{
 		SocketPath:         *socketpath,
 		Port:               41112,
@@ -107,15 +130,13 @@ func main() {
 		SurviveDisconnects: true,
 		DebugMux:           debugMux,
 	}
-	err = ipnserver.Run(context.Background(), logf, pol.PublicID.String(), opts, e)
+	err = ipnserver.Run(ctx, logf, pol.PublicID.String(), opts, e)
 	if err != nil {
 		log.Fatalf("tailscaled: %v", err)
 	}
 
-	// TODO(crawshaw): It would be nice to start a timeout context the moment a signal
-	// is received and use that timeout to give us a moment to finish uploading logs
-	// here. But the signal is handled inside ipnserver.Run, so some plumbing is needed.
-	ctx, cancel := context.WithCancel(context.Background())
+	// Finish uploading logs after closing everything else.
+	ctx, cancel = context.WithTimeout(context.Background(), time.Second)
 	cancel()
 	pol.Shutdown(ctx)
 }

cmd/tailscaled/tailscaled.service

@@ -9,6 +9,7 @@ StartLimitBurst=0
 [Service]
 EnvironmentFile=/etc/default/tailscaled
 ExecStart=/usr/sbin/tailscaled --state=/var/lib/tailscale/tailscaled.state --socket=/run/tailscale/tailscaled.sock --port $PORT $FLAGS
+ExecStopPost=/usr/sbin/tailscaled --cleanup
 
 Restart=on-failure
 

ipn/ipnserver/server.go

@@ -224,6 +224,7 @@ func Run(rctx context.Context, logf logger.Logf, logid string, opts Options, e w
 	}
 	stopAll()
 
+	b.Shutdown()
 	return rctx.Err()
 }
 

ipn/local.go

@@ -49,6 +49,7 @@ type LocalBackend struct {
 	store           StateStore
 	backendLogID    string
 	portpoll        *portlist.Poller // may be nil
+	portpollOnce    sync.Once
 	newDecompressor func() (controlclient.Decompressor, error)
 
 	// TODO: these fields are accessed unsafely by concurrent
@@ -387,8 +388,10 @@ func (b *LocalBackend) Start(opts Options) error {
 	// At this point, we have finished using hostinfo without synchronization,
 	// so it is safe to start readPoller which concurrently writes to it.
 	if b.portpoll != nil {
-		go b.portpoll.Run(b.ctx)
-		go b.readPoller()
+		b.portpollOnce.Do(func() {
+			go b.portpoll.Run(b.ctx)
+			go b.readPoller()
+		})
 	}
 
 	b.mu.Lock()

wgengine/router/router.go

@@ -35,6 +35,13 @@ func New(logf logger.Logf, wgdev *device.Device, tundev tun.Device) (Router, err
 	return newUserspaceRouter(logf, wgdev, tundev)
 }
 
+// Cleanup restores the system network configuration to its original state
+// in case the Tailscale daemon terminated without closing the router.
+// No other state needs to be instantiated before this runs.
+func Cleanup(logf logger.Logf, interfaceName string) {
+	// TODO(dmytro): implement this.
+}
+
 // NetfilterMode is the firewall management mode to use when
 // programming the Linux network stack.
 type NetfilterMode int