android/taildrop: support direct mode for incoming taildrop (#251)

Updates tailscale/corp#18202

Implements direct mode support for incoming taildrop files.  None of the localAPI endpoints are implemented here but this will get taildrop files to the right places.

Signed-off-by: Jonathan Nobels <jonathan@tailscale.com>

android/src/main/java/com/tailscale/ipn/App.kt

@@ -109,7 +109,14 @@ class App : Application(), libtailscale.AppContext {
   override fun onCreate() {
     super.onCreate()
     val dataDir = this.filesDir.absolutePath
-    app = Libtailscale.start(dataDir, this)
+
+    // Set this to enable direct mode for taildrop whereby downloads will be saved directly
+    // to the given folder.  We will preferentially use <shared>/Downloads and fallback to
+    // an app local directory "Taildrop" if we cannot create that.  This mode does not support
+    // user notifications for incoming files.
+    val directFileDir = this.prepareDownloadsFolder()
+
+    app = Libtailscale.start(dataDir, directFileDir.absolutePath, this)
     Request.setApp(app)
     Notifier.setApp(app)
     connectivityManager = this.getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
@@ -464,4 +471,27 @@ class App : Application(), libtailscale.AppContext {
       }
     }
   }
+
+  fun prepareDownloadsFolder(): File {
+    var downloads = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS)
+
+    try {
+      if (!downloads.exists()) {
+        downloads.mkdirs()
+      }
+    } catch (e: Exception) {
+      Log.e(TAG, "Failed to create downloads folder: $e")
+      downloads = File(this.filesDir, "Taildrop")
+      try {
+        if (!downloads.exists()) {
+          downloads.mkdirs()
+        }
+      } catch (e: Exception) {
+        Log.e(TAG, "Failed to create Taildrop folder: $e")
+        downloads = File("")
+      }
+    }
+
+    return downloads
+  }
 }

libtailscale/backend.go

@@ -35,6 +35,10 @@ import (
 
 type App struct {
 	dataDir string
+
+	// enables direct file mode for the taildrop manager
+	directFileRoot string
+
 	// appCtx is a global reference to the com.tailscale.ipn.App instance.
 	appCtx AppContext
 
@@ -46,7 +50,7 @@ type App struct {
 	ready           sync.WaitGroup
 }
 
-func start(dataDir string, appCtx AppContext) Application {
+func start(dataDir, directFileRoot string, appCtx AppContext) Application {
 	defer func() {
 		if p := recover(); p != nil {
 			log.Printf("panic in Start %s: %s", p, debug.Stack())
@@ -70,7 +74,7 @@ func start(dataDir string, appCtx AppContext) Application {
 		os.Setenv("HOME", dataDir)
 	}
 
-	return newApp(dataDir, appCtx)
+	return newApp(dataDir, directFileRoot, appCtx)
 }
 
 type backend struct {
@@ -113,7 +117,7 @@ func (a *App) runBackend(ctx context.Context) error {
 	}
 	configs := make(chan configPair)
 	configErrs := make(chan error)
-	b, err := newBackend(a.dataDir, a.appCtx, a.store, func(rcfg *router.Config, dcfg *dns.OSConfig) error {
+	b, err := newBackend(a.dataDir, a.directFileRoot, a.appCtx, a.store, func(rcfg *router.Config, dcfg *dns.OSConfig) error {
 		if rcfg == nil {
 			return nil
 		}
@@ -228,7 +232,7 @@ func (a *App) runBackend(ctx context.Context) error {
 	}
 }
 
-func newBackend(dataDir string, appCtx AppContext, store *stateStore,
+func newBackend(dataDir, directFileRoot string, appCtx AppContext, store *stateStore,
 	settings settingsFunc) (*backend, error) {
 
 	sys := new(tsd.System)
@@ -299,6 +303,8 @@ func newBackend(dataDir string, appCtx AppContext, store *stateStore,
 		engine.Close()
 		return nil, fmt.Errorf("runBackend: NewLocalBackend: %v", err)
 	}
+	lb.SetDirectFileRoot(directFileRoot)
+
 	if err := ns.Start(lb); err != nil {
 		return nil, fmt.Errorf("startNetstack: %w", err)
 	}

libtailscale/callbacks.go

@@ -26,50 +26,10 @@ var (
 	// onGoogleToken receives google ID tokens.
 	onGoogleToken = make(chan string)
 
-	// onWriteStorageGranted is notified when we are granted WRITE_STORAGE_PERMISSION.
-	onWriteStorageGranted = make(chan struct{}, 1)
-
 	// onDNSConfigChanged is notified when the network changes and the DNS config needs to be updated.
 	onDNSConfigChanged = make(chan struct{}, 1)
 )
 
-func OnShareIntent(nfiles int32, types []int32, mimes []string, items []string, names []string, sizes []int) {
-	// TODO(oxtoacart): actually implement this
-	// const (
-	// 	typeNone   = 0
-	// 	typeInline = 1
-	// 	typeURI    = 2
-	// )
-	// jenv := (*jni.Env)(unsafe.Pointer(env))
-	// var files []File
-	// for i := 0; i < int(nfiles); i++ {
-	// 	f := File{
-	// 		Type:     FileType(types[i]),
-	// 		MIMEType: mimes[i],
-	// 		Name:     names[i],
-	// 	}
-	// 	if f.Name == "" {
-	// 		f.Name = "file.bin"
-	// 	}
-	// 	switch f.Type {
-	// 	case FileTypeText:
-	// 		f.Text = items[i]
-	// 		f.Size = int64(len(f.Text))
-	// 	case FileTypeURI:
-	// 		f.URI = items[i]
-	// 		f.Size = sizes[i]
-	// 	default:
-	// 		panic("unknown file type")
-	// 	}
-	// 	files = append(files, f)
-	// }
-	// select {
-	// case <-onFileShare:
-	// default:
-	// }
-	// onFileShare <- files
-}
-
 func OnDnsConfigChanged() {
 	select {
 	case onDNSConfigChanged <- struct{}{}:
@@ -77,14 +37,6 @@ func OnDnsConfigChanged() {
 	}
 }
 
-//export Java_com_tailscale_ipn_App_onWriteStorageGranted
-func OnWriteStorageGranted() {
-	select {
-	case onWriteStorageGranted <- struct{}{}:
-	default:
-	}
-}
-
 func notifyVPNPrepared() {
 	select {
 	case onVPNPrepared <- struct{}{}:

libtailscale/interfaces.go

@@ -7,8 +7,8 @@ import _ "golang.org/x/mobile/bind"
 
 // Start starts the application, storing state in the given dataDir and using
 // the given appCtx.
-func Start(dataDir string, appCtx AppContext) Application {
-	return start(dataDir, appCtx)
+func Start(dataDir, directFileRoot string, appCtx AppContext) Application {
+	return start(dataDir, directFileRoot, appCtx)
 }
 
 // AppContext provides a context within which the Application is running. This

libtailscale/tailscale.go

@@ -30,10 +30,11 @@ const (
 	customLoginServerPrefKey = "customloginserver"
 )
 
-func newApp(dataDir string, appCtx AppContext) Application {
+func newApp(dataDir, directFileRoot string, appCtx AppContext) Application {
 	a := &App{
-		dataDir: dataDir,
-		appCtx:  appCtx,
+		directFileRoot: directFileRoot,
+		dataDir:        dataDir,
+		appCtx:         appCtx,
 	}
 	a.ready.Add(1)