Make it even simpler by removing Init

ipn/ipnlocal/local.go

@@ -146,9 +146,8 @@ 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
+	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
@@ -292,12 +291,6 @@ func NewLocalBackend(logf logger.Logf, logID logid.PublicID, sys *tsd.System, lo
 	osshare.SetFileSharingEnabled(false, logf)
 
 	ctx, cancel := context.WithCancel(context.Background())
-	portpoll := new(portlist.Poller)
-	err = portpoll.Init()
-	if err != nil {
-		logf("skipping portlist: %s", err)
-		portpoll = nil
-	}
 
 	b := &LocalBackend{
 		ctx:            ctx,
@@ -312,7 +305,6 @@ func NewLocalBackend(logf logger.Logf, logID logid.PublicID, sys *tsd.System, lo
 		pm:             pm,
 		backendLogID:   logID,
 		state:          ipn.NoState,
-		portpoll:       portpoll,
 		em:             newExpiryManager(logf),
 		gotPortPollRes: make(chan struct{}),
 		loginFlags:     loginFlags,
@@ -1377,30 +1369,32 @@ func (b *LocalBackend) Start(opts ipn.Options) error {
 	b.updateFilterLocked(nil, ipn.PrefsView{})
 	b.mu.Unlock()
 
-	if b.portpoll != nil {
-		b.portpollOnce.Do(func() {
-			updates, err := b.portpoll.Run(b.ctx)
-			if err != nil {
-				b.logf("error running port poller: %v", err)
-				return
-			}
-			go b.readPoller(updates)
+	b.portpollOnce.Do(func() {
+		var p portlist.Poller
+		updates, err := p.Run(b.ctx)
+		if err != nil {
+			b.logf("skipping portlist: %s", err)
+			return
+		}
+		go func() {
+			defer p.Close()
+			b.readPoller(updates)
+		}()
 
-			// Give the poller a second to get results to
-			// prevent it from restarting our map poll
-			// HTTP request (via doSetHostinfoFilterServices >
-			// cli.SetHostinfo). In practice this is very quick.
-			t0 := time.Now()
-			timer := time.NewTimer(time.Second)
-			select {
-			case <-b.gotPortPollRes:
-				b.logf("[v1] got initial portlist info in %v", time.Since(t0).Round(time.Millisecond))
-				timer.Stop()
-			case <-timer.C:
-				b.logf("timeout waiting for initial portlist")
-			}
-		})
-	}
+		// Give the poller a second to get results to
+		// prevent it from restarting our map poll
+		// HTTP request (via doSetHostinfoFilterServices >
+		// cli.SetHostinfo). In practice this is very quick.
+		t0 := time.Now()
+		timer := time.NewTimer(time.Second)
+		select {
+		case <-b.gotPortPollRes:
+			b.logf("[v1] got initial portlist info in %v", time.Since(t0).Round(time.Millisecond))
+			timer.Stop()
+		case <-timer.C:
+			b.logf("timeout waiting for initial portlist")
+		}
+	})
 
 	discoPublic := b.e.DiscoPublicKey()
 
@@ -1818,16 +1812,11 @@ func dnsMapsEqual(new, old *netmap.NetworkMap) bool {
 // readPoller is a goroutine that receives service lists from
 // b.portpoll and propagates them into the controlclient's HostInfo.
 func (b *LocalBackend) readPoller(updates chan portlist.Update) {
-	defer b.portpoll.Close()
-	n := 0
-	for {
-		update, ok := <-updates
-		if !ok {
-			return
-		}
+	firstResults := true
+	for update := range updates {
 		if update.Error != nil {
 			b.logf("error polling os ports: %v", update.Error)
-			return // preserve all behavior, though we can just continue
+			return // preserve old behavior, though we can just continue and try again?
 		}
 		sl := []tailcfg.Service{}
 		for _, p := range update.List {
@@ -1851,8 +1840,8 @@ func (b *LocalBackend) readPoller(updates chan portlist.Update) {
 
 		b.doSetHostinfoFilterServices(hi)
 
-		n++
-		if n == 1 {
+		if firstResults {
+			firstResults = false
 			close(b.gotPortPollRes)
 		}
 	}

portlist/poller.go

@@ -97,20 +97,20 @@ func (p *Poller) setPrev(pl List) {
 	p.prev = slices.Clone(pl)
 }
 
-// Init is an optional method that makes sure the Poller is enabled
+// init makes sure the Poller is enabled
 // and the undelrying OS implementation is working properly.
 //
-// An error returned from Init is non-fatal and means
+// An error returned from init is non-fatal and means
 // that it's been administratively disabled or the underlying
 // OS is not implemented.
-func (p *Poller) Init() error {
+func (p *Poller) init() error {
 	p.initOnce.Do(func() {
-		p.initErr = p.init()
+		p.initErr = p.initWithErr()
 	})
 	return p.initErr
 }
 
-func (p *Poller) init() error {
+func (p *Poller) initWithErr() error {
 	if debugDisablePortlist() {
 		return errors.New("portlist disabled by envknob")
 	}
@@ -170,7 +170,7 @@ func (p *Poller) send(ctx context.Context, pl List, plErr error) (sent bool) {
 // Run may only be called once.
 func (p *Poller) Run(ctx context.Context) (chan Update, error) {
 	if p.os == nil {
-		err := p.Init()
+		err := p.init()
 		if err != nil {
 			return nil, fmt.Errorf("error initializing poller: %w", err)
 		}

portlist/portlist_test.go

@@ -179,7 +179,7 @@ func TestEqualLessThan(t *testing.T) {
 
 func TestPoller(t *testing.T) {
 	var p Poller
-	err := p.Init()
+	err := p.init()
 	if err != nil {
 		t.Skipf("not running test: %v", err)
 	}