wip

ipn/ipnlocal/local.go

@@ -146,9 +146,9 @@ type LocalBackend struct {
 	backendLogID          logid.PublicID
 	unregisterNetMon      func()
 	unregisterHealthWatch func()
-	portpoll              *portlist.Poller // may be nil
-	portpollOnce          sync.Once        // guards starting readPoller
-	gotPortPollRes        chan struct{}    // closed upon first readPoller result
+	portpoll              chan portlist.Update // may be nil
+	portpollOnce          sync.Once            // guards starting readPoller
+	gotPortPollRes        chan struct{}        // closed upon first readPoller result
 	newDecompressor       func() (controlclient.Decompressor, error)
 	varRoot               string         // or empty if SetVarRoot never called
 	logFlushFunc          func()         // or nil if SetLogFlusher wasn't called
@@ -292,7 +292,8 @@ func NewLocalBackend(logf logger.Logf, logID logid.PublicID, sys *tsd.System, lo
 	osshare.SetFileSharingEnabled(false, logf)
 
 	ctx, cancel := context.WithCancel(context.Background())
-	portpoll, err := portlist.NewPoller()
+	var p portlist.Poller
+	portUpdates, err := p.Run(ctx)
 	if err != nil {
 		logf("skipping portlist: %s", err)
 	}
@@ -310,7 +311,7 @@ func NewLocalBackend(logf logger.Logf, logID logid.PublicID, sys *tsd.System, lo
 		pm:             pm,
 		backendLogID:   logID,
 		state:          ipn.NoState,
-		portpoll:       portpoll,
+		portpoll:       portUpdates,
 		em:             newExpiryManager(logf),
 		gotPortPollRes: make(chan struct{}),
 		loginFlags:     loginFlags,
@@ -1377,7 +1378,6 @@ func (b *LocalBackend) Start(opts ipn.Options) error {
 
 	if b.portpoll != nil {
 		b.portpollOnce.Do(func() {
-			go b.portpoll.Run(b.ctx)
 			go b.readPoller()
 
 			// Give the poller a second to get results to
@@ -1814,12 +1814,17 @@ func dnsMapsEqual(new, old *netmap.NetworkMap) bool {
 func (b *LocalBackend) readPoller() {
 	n := 0
 	for {
-		ports, ok := <-b.portpoll.Updates()
+		update, ok := <-b.portpoll
 		if !ok {
 			return
 		}
+		if update.Err() != nil {
+			// TODO(marwan-at-work): do we need to log this?
+			// TODO(marwan-at-work): should we return or keep trying?
+			return
+		}
 		sl := []tailcfg.Service{}
-		for _, p := range ports {
+		for _, p := range update.List() {
 			s := tailcfg.Service{
 				Proto:       tailcfg.ServiceProto(p.Proto),
 				Port:        p.Port,

portlist/poller.go

@@ -29,7 +29,7 @@ type Poller struct {
 	// This field should only be changed before calling Run.
 	IncludeLocalhost bool
 
-	c chan List // unbuffered
+	c chan Update // unbuffered
 
 	// os, if non-nil, is an OS-specific implementation of the portlist getting
 	// code. When non-nil, it's responsible for getting the complete list of
@@ -52,6 +52,23 @@ type Poller struct {
 	prev List // most recent data, not aliasing scratch
 }
 
+// Update is sent by Poller to indicate
+// an update has been made to the machine's
+// open ports. Receiver of this struct must
+// check the Err() method before calling List().
+type Update struct {
+	list List
+	err  error
+}
+
+func (u *Update) Err() error {
+	return u.err
+}
+
+func (u *Update) List() List {
+	return u.list
+}
+
 // osImpl is the OS-specific implementation of getting the open listening ports.
 type osImpl interface {
 	Close() error
@@ -71,32 +88,6 @@ type osImpl interface {
 
 var errUnimplemented = errors.New("portlist poller not implemented on " + runtime.GOOS)
 
-// NewPoller returns a new portlist Poller. It returns an error
-// if the portlist couldn't be obtained.
-func NewPoller() (*Poller, error) {
-	if debugDisablePortlist() {
-		return nil, errors.New("portlist disabled by envknob")
-	}
-	p := &Poller{
-		c:       make(chan List),
-		runDone: make(chan struct{}),
-	}
-	p.closeCtx, p.closeCtxCancel = context.WithCancel(context.Background())
-	p.osOnce.Do(p.initOSField)
-	if p.os == nil {
-		return nil, errUnimplemented
-	}
-
-	// Do one initial poll synchronously so we can return an error
-	// early.
-	if pl, err := p.getList(); err != nil {
-		return nil, err
-	} else {
-		p.setPrev(pl)
-	}
-	return p, nil
-}
-
 func (p *Poller) setPrev(pl List) {
 	// Make a copy, as the pass in pl slice aliases pl.scratch and we don't want
 	// that to except to the caller.
@@ -112,11 +103,15 @@ func (p *Poller) initOSField() {
 // Updates return the channel that receives port list updates.
 //
 // The channel is closed when the Poller is closed.
-func (p *Poller) Updates() <-chan List { return p.c }
+func (p *Poller) Updates() <-chan Update { return p.c }
 
 // Close closes the Poller.
 // Run will return with a nil error.
 func (p *Poller) Close() error {
+	// Skip if uninitialized.
+	if p.os == nil {
+		return nil
+	}
 	p.closeCtxCancel()
 	<-p.runDone
 	if p.os != nil {
@@ -126,14 +121,14 @@ func (p *Poller) Close() error {
 }
 
 // send sends pl to p.c and returns whether it was successfully sent.
-func (p *Poller) send(ctx context.Context, pl List) (sent bool, err error) {
+func (p *Poller) send(ctx context.Context, pl List, listErr error) (sent bool) {
 	select {
-	case p.c <- pl:
-		return true, nil
+	case p.c <- Update{list: pl, err: listErr}:
+		return true
 	case <-ctx.Done():
-		return false, ctx.Err()
+		return false
 	case <-p.closeCtx.Done():
-		return false, nil
+		return false
 	}
 }
 
@@ -141,48 +136,82 @@ func (p *Poller) send(ctx context.Context, pl List) (sent bool, err error) {
 // is done, or the Close is called.
 //
 // Run may only be called once.
-func (p *Poller) Run(ctx context.Context) error {
+func (p *Poller) Run(ctx context.Context) (chan Update, error) {
+	if debugDisablePortlist() {
+		return nil, errors.New("portlist disabled by envknob")
+	}
+	if p.os != nil {
+		return nil, errors.New("method called more than once")
+	}
+	p.initOSField()
+	if p.os == nil {
+		return nil, errUnimplemented
+	}
+
+	p.c = make(chan Update)
+	p.runDone = make(chan struct{})
+	p.closeCtx, p.closeCtxCancel = context.WithCancel(context.Background())
+
+	// Do one initial poll synchronously so we can return an error
+	// early.
+	if pl, err := p.getList(); err != nil {
+		return nil, err
+	} else {
+		p.setPrev(pl)
+	}
+
 	tick := time.NewTicker(pollInterval)
 	defer tick.Stop()
-	return p.runWithTickChan(ctx, tick.C)
+	go p.runWithTickChan(ctx, tick.C)
+	return p.c, nil
 }
 
-func (p *Poller) runWithTickChan(ctx context.Context, tickChan <-chan time.Time) error {
+func (p *Poller) runWithTickChan(ctx context.Context, tickChan <-chan time.Time) {
 	defer close(p.runDone)
 	defer close(p.c)
 
 	// Send out the pre-generated initial value.
-	if sent, err := p.send(ctx, p.prev); !sent {
-		return err
+	if sent := p.send(ctx, p.prev, nil); !sent {
+		return
 	}
 
+	// Order of events:
+	// 1. If the context is done, exit
+	// 2. If the user called p.Close(), exit.
+	// 3. If we received a tick, then get the list
+	// 3B. If that error'd, send an error to the user.
+	// 3C. If the context or p.Close where called in the meantime, exit.
+	// 3D. If getList succeeded, skip if there are no updates.
+	// 3E. If there are indeed updates, send them, or exit if 1/2 are true.
+	// We check 1 & 2 in 3 places: top of the for-loop,
+	// whenever we send (which is two places: sending an error, or sending a list).
 	for {
 		select {
+		case <-ctx.Done():
+			return
+		case <-p.closeCtx.Done():
+			return
 		case <-tickChan:
 			pl, err := p.getList()
 			if err != nil {
-				return err
+				sent := p.send(ctx, nil, err)
+				if !sent {
+					return
+				}
+				continue
 			}
 			if pl.equal(p.prev) {
 				continue
 			}
 			p.setPrev(pl)
-			if sent, err := p.send(ctx, p.prev); !sent {
-				return err
+			if sent := p.send(ctx, p.prev, nil); !sent {
+				return
 			}
-		case <-ctx.Done():
-			return ctx.Err()
-		case <-p.closeCtx.Done():
-			return nil
 		}
 	}
 }
 
 func (p *Poller) getList() (List, error) {
-	if debugDisablePortlist() {
-		return nil, nil
-	}
-	p.osOnce.Do(p.initOSField)
 	var err error
 	p.scratch, err = p.os.AppendListeningPorts(p.scratch[:0])
 	return p.scratch, err

portlist/portlist_test.go

@@ -192,7 +192,7 @@ func TestPoller(t *testing.T) {
 		for pl := range p.Updates() {
 			// Look at all the pl slice memory to maximize
 			// chance of race detector seeing violations.
-			for _, v := range pl {
+			for _, v := range pl.List() {
 				if v == (Port{}) {
 					// Force use
 					panic("empty port")