ipn{,/ipnlocal}: set new Notify.FilesWaiting when server has file(s)

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

ipn/backend.go

@@ -68,6 +68,8 @@ type Notify struct {
 	BackendLogID  *string            // public logtail id used by backend
 	PingResult    *ipnstate.PingResult
 
+	FilesWaiting *empty.Message `json:",omitempty"`
+
 	// LocalTCPPort, if non-nil, informs the UI frontend which
 	// (non-zero) localhost TCP port it's listening on.
 	// This is currently only used by Tailscale when run in the

ipn/ipnlocal/local.go

@@ -107,6 +107,7 @@ type LocalBackend struct {
 	authURL          string
 	interact         bool
 	prevIfState      *interfaces.State
+	peerAPIServer    *peerAPIServer // or nil
 	peerAPIListeners []*peerAPIListener
 
 	// statusLock must be held before calling statusChanged.Wait() or
@@ -909,15 +910,20 @@ func (b *LocalBackend) readPoller() {
 // connected, the notification is dropped without being delivered.
 func (b *LocalBackend) send(n ipn.Notify) {
 	b.mu.Lock()
-	notify := b.notify
+	notifyFunc := b.notify
+	apiSrv := b.peerAPIServer
 	b.mu.Unlock()
 
-	if notify != nil {
-		n.Version = version.Long
-		notify(n)
-	} else {
+	if notifyFunc == nil {
 		b.logf("nil notify callback; dropping %+v", n)
+		return
+	}
+
+	n.Version = version.Long
+	if apiSrv != nil && apiSrv.hasFilesWaiting() {
+		n.FilesWaiting = &empty.Message{}
 	}
+	notifyFunc(n)
 }
 
 // popBrowserAuthNow shuts down the data plane and sends an auth URL
@@ -1489,6 +1495,7 @@ func (b *LocalBackend) initPeerAPIListener() {
 	b.mu.Lock()
 	defer b.mu.Unlock()
 
+	b.peerAPIServer = nil
 	for _, pln := range b.peerAPIListeners {
 		pln.Close()
 	}
@@ -1526,6 +1533,7 @@ func (b *LocalBackend) initPeerAPIListener() {
 		tunName:  tunName,
 		selfNode: selfNode,
 	}
+	b.peerAPIServer = ps
 
 	isNetstack := wgengine.IsNetstack(b.e)
 	for i, a := range b.netMap.Addresses {

ipn/ipnlocal/peerapi.go

@@ -22,7 +22,9 @@ import (
 	"strings"
 
 	"inet.af/netaddr"
+	"tailscale.com/ipn"
 	"tailscale.com/net/interfaces"
+	"tailscale.com/syncs"
 	"tailscale.com/tailcfg"
 	"tailscale.com/wgengine"
 )
@@ -30,10 +32,52 @@ import (
 var initListenConfig func(*net.ListenConfig, netaddr.IP, *interfaces.State, string) error
 
 type peerAPIServer struct {
-	b        *LocalBackend
-	rootDir  string
-	tunName  string
-	selfNode *tailcfg.Node
+	b          *LocalBackend
+	rootDir    string
+	tunName    string
+	selfNode   *tailcfg.Node
+	knownEmpty syncs.AtomicBool
+}
+
+const partialSuffix = ".tspartial"
+
+// hasFilesWaiting reports whether any files are buffered in the
+// tailscaled daemon storage.
+func (s *peerAPIServer) hasFilesWaiting() bool {
+	if s.rootDir == "" {
+		return false
+	}
+	if s.knownEmpty.Get() {
+		// Optimization: this is usually empty, so avoid opening
+		// the directory and checking. We can't cache the actual
+		// has-files-or-not values as the macOS/iOS client might
+		// in the future use+delete the files directly. So only
+		// keep this negative cache.
+		return false
+	}
+	f, err := os.Open(s.rootDir)
+	if err != nil {
+		return false
+	}
+	defer f.Close()
+	for {
+		des, err := f.ReadDir(10)
+		for _, de := range des {
+			if strings.HasSuffix(de.Name(), partialSuffix) {
+				continue
+			}
+			if de.Type().IsRegular() {
+				return true
+			}
+		}
+		if err == io.EOF {
+			s.knownEmpty.Set(true)
+		}
+		if err != nil {
+			break
+		}
+	}
+	return false
 }
 
 func (s *peerAPIServer) listen(ip netaddr.IP, ifState *interfaces.State) (ln net.Listener, err error) {
@@ -221,7 +265,7 @@ func (h *peerAPIHandler) put(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	name := path.Base(r.URL.Path)
-	if name == "." || name == "/" {
+	if name == "." || name == "/" || strings.HasSuffix(name, partialSuffix) {
 		http.Error(w, "bad filename", http.StatusForbidden)
 		return
 	}
@@ -258,4 +302,6 @@ func (h *peerAPIHandler) put(w http.ResponseWriter, r *http.Request) {
 	// TODO: some real response
 	success = true
 	io.WriteString(w, "{}\n")
+	h.ps.knownEmpty.Set(false)
+	h.ps.b.send(ipn.Notify{}) // it will set FilesWaiting
 }