android/ui: add support for remembering the last used exit node (#305)

Updates ENG-2911

Disabling an exit node is now temporary and you can re-enable it without re-selecting it from the picker.

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

android/src/main/java/com/tailscale/ipn/ui/localapi/Client.kt

@@ -46,6 +46,7 @@ private object Endpoint {
   const val FILES = "files"
   const val FILE_PUT = "file-put"
   const val TAILFS_SERVER_ADDRESS = "tailfs/fileserver-address"
+  const val ENABLE_EXIT_NODE = "set-use-exit-node-enabled"
 }
 
 typealias StatusResponseHandler = (Result<IpnState.Status>) -> Unit
@@ -85,6 +86,11 @@ class Client(private val scope: CoroutineScope) {
     return patch(Endpoint.PREFS, body, responseHandler = responseHandler)
   }
 
+  fun setUseExitNode(use: Boolean, responseHandler: (Result<Ipn.Prefs>) -> Unit) {
+    val path = "${Endpoint.ENABLE_EXIT_NODE}?enabled=$use"
+    return post(path, responseHandler = responseHandler)
+  }
+
   fun profiles(responseHandler: (Result<List<IpnLocal.LoginProfile>>) -> Unit) {
     get(Endpoint.PROFILES, responseHandler = responseHandler)
   }

android/src/main/java/com/tailscale/ipn/ui/model/Ipn.kt

@@ -65,7 +65,22 @@ class Ipn {
       var ForceDaemon: Boolean = false,
       var HostName: String = "",
       var AutoUpdate: AutoUpdatePrefs? = AutoUpdatePrefs(true, true),
-  )
+      var InternalExitNodePrior: String? = null,
+  ) {
+
+    // For the InternalExitNodePrior and ExitNodeId, these will treats the empty string as null to
+    // simplify the downstream logic.
+
+    val selectedExitNodeID: String?
+      get() {
+        return if (InternalExitNodePrior.isNullOrEmpty()) null else InternalExitNodePrior
+      }
+
+    val activeExitNodeID: String?
+      get() {
+        return if (ExitNodeID.isNullOrEmpty()) null else ExitNodeID
+      }
+  }
 
   @Serializable
   data class MaskedPrefs(
@@ -79,6 +94,7 @@ class Ipn {
       var AdvertiseRoutesSet: Boolean? = null,
       var ForceDaemonSet: Boolean? = null,
       var HostnameSet: Boolean? = null,
+      var InternalExitNodePriorSet: Boolean? = null,
   ) {
 
     var ControlURL: String? = null
@@ -105,6 +121,12 @@ class Ipn {
         ExitNodeIDSet = true
       }
 
+    var InternalExitNodePrior: String? = null
+      set(value) {
+        field = value
+        InternalExitNodePriorSet = true
+      }
+
     var ExitNodeAllowLANAccess: Boolean? = null
       set(value) {
         field = value

android/src/main/java/com/tailscale/ipn/ui/theme/Theme.kt

@@ -333,6 +333,17 @@ val ColorScheme.onBackgroundLogoDotDisabled: Color
         Color(0x66FFFFFF)
       }
 
+val ColorScheme.exitNodeToggleButton: ButtonColors
+  @Composable
+  get() {
+    val defaults = ButtonDefaults.buttonColors()
+    return ButtonColors(
+        containerColor = Color(0xFF4B70CC), // blue-500
+        contentColor = Color(0xFFFFFFFF), // white
+        disabledContainerColor = defaults.disabledContainerColor,
+        disabledContentColor = defaults.disabledContentColor)
+  }
+
 val ColorScheme.disabled: Color
   get() = Color(0xFFAFACAB) // gray-400
 

android/src/main/java/com/tailscale/ipn/ui/view/MainView.kt

@@ -70,6 +70,7 @@ import com.tailscale.ipn.ui.model.Netmap
 import com.tailscale.ipn.ui.model.Permissions
 import com.tailscale.ipn.ui.model.Tailcfg
 import com.tailscale.ipn.ui.theme.disabled
+import com.tailscale.ipn.ui.theme.exitNodeToggleButton
 import com.tailscale.ipn.ui.theme.listItem
 import com.tailscale.ipn.ui.theme.minTextSize
 import com.tailscale.ipn.ui.theme.primaryListItem
@@ -182,13 +183,26 @@ fun MainView(
 
 @Composable
 fun ExitNodeStatus(navAction: () -> Unit, viewModel: MainViewModel) {
-  val prefs = viewModel.prefs.collectAsState()
+  val maybePrefs = viewModel.prefs.collectAsState()
   val netmap = viewModel.netmap.collectAsState()
-  val exitNodeId = prefs.value?.ExitNodeID
-  val peer = exitNodeId?.let { id -> netmap.value?.Peers?.find { it.StableID == id } }
-  val location = peer?.Hostinfo?.Location
-  val name = peer?.ComputedName
-  val active = peer != null
+
+  // There's nothing to render if we haven't loaded the prefs yet
+  val prefs = maybePrefs.value ?: return
+
+  // The activeExitNode is the source of truth.  The selectedExitNode is only relevant if we
+  // don't have an active node.
+  val chosenExitNodeId = prefs.activeExitNodeID ?: prefs.selectedExitNodeID
+
+  val exitNodePeer = chosenExitNodeId?.let { id -> netmap.value?.Peers?.find { it.StableID == id } }
+  val location = exitNodePeer?.Hostinfo?.Location
+  val name = exitNodePeer?.ComputedName
+
+  // We're connected to an exit node if we found an active peer for the *active* exit node
+  val activeAndRunning = (exitNodePeer != null) && !prefs.activeExitNodeID.isNullOrEmpty()
+
+  // (jonathan) TODO: We will block the "enable/disable" button for an exit node for which we cannot
+  // find a peer  on purpose and render the "No Exit Node" state, however, that should
+  // eventually show up in the UI as an error case so the user knows to pick an available node.
 
   Box(modifier = Modifier.background(color = MaterialTheme.colorScheme.surfaceContainer)) {
     Box(
@@ -199,7 +213,7 @@ fun ExitNodeStatus(navAction: () -> Unit, viewModel: MainViewModel) {
           ListItem(
               modifier = Modifier.clickable { navAction() },
               colors =
-                  if (active) MaterialTheme.colorScheme.primaryListItem
+                  if (activeAndRunning) MaterialTheme.colorScheme.primaryListItem
                   else ListItemDefaults.colors(containerColor = MaterialTheme.colorScheme.surface),
               overlineContent = {
                 Text(
@@ -221,17 +235,24 @@ fun ExitNodeStatus(navAction: () -> Unit, viewModel: MainViewModel) {
                       imageVector = Icons.Outlined.ArrowDropDown,
                       contentDescription = null,
                       tint =
-                          if (active) MaterialTheme.colorScheme.onPrimary.copy(alpha = 0.7f)
+                          if (activeAndRunning)
+                              MaterialTheme.colorScheme.onPrimary.copy(alpha = 0.7f)
                           else MaterialTheme.colorScheme.onSurfaceVariant,
                   )
                 }
               },
               trailingContent = {
-                if (peer != null) {
+                if (exitNodePeer != null) {
                   Button(
-                      colors = MaterialTheme.colorScheme.secondaryButton,
-                      onClick = { viewModel.disableExitNode() }) {
-                        Text(stringResource(R.string.stop))
+                      colors =
+                          if (prefs.activeExitNodeID.isNullOrEmpty())
+                              MaterialTheme.colorScheme.exitNodeToggleButton
+                          else MaterialTheme.colorScheme.secondaryButton,
+                      onClick = { viewModel.toggleExitNode() }) {
+                        Text(
+                            if (prefs.activeExitNodeID.isNullOrEmpty())
+                                stringResource(id = R.string.enable)
+                            else stringResource(id = R.string.disable))
                       }
                 }
               })
@@ -470,7 +491,8 @@ fun PeerList(
 fun ExpiryNotificationIfNecessary(netmap: Netmap.NetworkMap?, action: () -> Unit = {}) {
   // Key expiry warning shown only if the key is expiring within 24 hours (or has already expired)
   val networkMap = netmap ?: return
-  if (!TimeUtil.isWithin24Hours(networkMap.SelfNode.KeyExpiry) || networkMap.SelfNode.keyDoesNotExpire) {
+  if (!TimeUtil.isWithin24Hours(networkMap.SelfNode.KeyExpiry) ||
+      networkMap.SelfNode.keyDoesNotExpire) {
     return
   }
 
@@ -518,8 +540,6 @@ fun MainViewPreview() {
   MainView(
       {},
       MainViewNavigation(
-          onNavigateToSettings = {},
-          onNavigateToPeerDetails = {},
-          onNavigateToExitNodes = {}),
+          onNavigateToSettings = {}, onNavigateToPeerDetails = {}, onNavigateToExitNodes = {}),
       vm)
 }

android/src/main/java/com/tailscale/ipn/ui/viewModel/ExitNodePickerViewModel.kt

@@ -63,7 +63,7 @@ class ExitNodePickerViewModel(private val nav: ExitNodePickerNav) : IpnViewModel
           .stateIn(viewModelScope)
           .collect { (netmap, prefs) ->
             isRunningExitNode.set(prefs?.let { AdvertisedRoutesHelper.exitNodeOnFromPrefs(it) })
-            val exitNodeId = prefs?.ExitNodeID
+            val exitNodeId = prefs?.activeExitNodeID ?: prefs?.selectedExitNodeID
             netmap?.Peers?.let { peers ->
               val allNodes =
                   peers
@@ -137,8 +137,9 @@ class ExitNodePickerViewModel(private val nav: ExitNodePickerNav) : IpnViewModel
     LoadingIndicator.start()
     val prefsOut = Ipn.MaskedPrefs()
     prefsOut.ExitNodeID = node.id
+
     Client(viewModelScope).editPrefs(prefsOut) {
-      nav.onNavigateBackHome()
+      nav.onNavigateBackToExitNodes()
       LoadingIndicator.stop()
     }
   }

android/src/main/java/com/tailscale/ipn/ui/viewModel/IpnViewModel.kt

@@ -14,6 +14,8 @@ import com.tailscale.ipn.ui.model.Ipn
 import com.tailscale.ipn.ui.model.IpnLocal
 import com.tailscale.ipn.ui.model.UserID
 import com.tailscale.ipn.ui.notifier.Notifier
+import com.tailscale.ipn.ui.notifier.Notifier.prefs
+import com.tailscale.ipn.ui.util.LoadingIndicator
 import com.tailscale.ipn.ui.util.set
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.StateFlow
@@ -183,4 +185,22 @@ open class IpnViewModel : ViewModel() {
       completionHandler(it)
     }
   }
+
+  // Exit Node Manipulation
+
+  fun toggleExitNode() {
+    val prefs = prefs.value ?: return
+
+    LoadingIndicator.start()
+    if (prefs.activeExitNodeID != null) {
+      // We have an active exit node so we should keep it, but disable it
+      Client(viewModelScope).setUseExitNode(false) { LoadingIndicator.stop() }
+    } else if (prefs.selectedExitNodeID != null) {
+      // We have a prior exit node to enable
+      Client(viewModelScope).setUseExitNode(true) { LoadingIndicator.stop() }
+    } else {
+      // This should not be possible.  In this state the button is hidden
+      Log.e(TAG, "No exit node to disable and no prior exit node to enable")
+    }
+  }
 }

android/src/main/java/com/tailscale/ipn/ui/viewModel/MainViewModel.kt

@@ -3,13 +3,11 @@
 
 package com.tailscale.ipn.ui.viewModel
 
+import android.util.Log
 import androidx.lifecycle.viewModelScope
 import com.tailscale.ipn.R
-import com.tailscale.ipn.ui.localapi.Client
-import com.tailscale.ipn.ui.model.Ipn
 import com.tailscale.ipn.ui.model.Ipn.State
 import com.tailscale.ipn.ui.notifier.Notifier
-import com.tailscale.ipn.ui.util.LoadingIndicator
 import com.tailscale.ipn.ui.util.PeerCategorizer
 import com.tailscale.ipn.ui.util.PeerSet
 import com.tailscale.ipn.ui.util.set
@@ -60,18 +58,15 @@ class MainViewModel : IpnViewModel() {
     viewModelScope.launch {
       searchTerm.collect { term -> peers.set(peerCategorizer.groupedAndFilteredPeers(term)) }
     }
+
+    viewModelScope.launch {
+      Notifier.prefs.collect { prefs -> Log.d(TAG, "Main VM - prefs = ${prefs}") }
+    }
   }
 
   fun searchPeers(searchTerm: String) {
     this.searchTerm.set(searchTerm)
   }
-
-  fun disableExitNode() {
-    LoadingIndicator.start()
-    val prefsOut = Ipn.MaskedPrefs()
-    prefsOut.ExitNodeID = null
-    Client(viewModelScope).editPrefs(prefsOut) { LoadingIndicator.stop() }
-  }
 }
 
 private fun State?.userStringRes(): Int {

android/src/main/res/values/strings.xml

@@ -64,6 +64,8 @@
     <string name="machine_auth_explainer">This device must be approved by an administrator before it can connect to the tailnet.</string>
     <string name="open_admin_console">Open admin console</string>
     <string name="needs_machine_auth">Authorization required</string>
+    <string name="disable">Disable</string>
+    <string name="enable">Enable</string>
 
     <!-- Strings for peer details -->
     <string name="os">OS</string>
@@ -140,7 +142,6 @@
     <string name="run_exit_node_explainer_running">Other devices in your tailnet can now route their internet traffic through this Android device. Make sure to approve this exit node in the admin console in order for other devices to see it.</string>
     <string name="enabled">Enabled</string>
     <string name="disabled">Disabled</string>
-    <string name="stop">Stop</string>
 
     <!-- Strings for the tailnet lock screen -->
     <string name="tailnet_lock">Tailnet lock</string>

go.mod

@@ -7,7 +7,7 @@ require (
 	golang.org/x/mobile v0.0.0-20240319015410-c58ccf4b0c87
 	golang.org/x/sys v0.18.0
 	inet.af/netaddr v0.0.0-20220617031823-097006376321
-	tailscale.com v1.65.0-pre.0.20240417162431-449be38e0381
+	tailscale.com v1.65.0-pre.0.20240418182715-02c6af2a69a8
 )
 
 require (
@@ -84,7 +84,7 @@ require (
 	golang.org/x/crypto v0.21.0 // indirect
 	golang.org/x/exp v0.0.0-20240119083558-1b970713d09a // indirect
 	golang.org/x/mod v0.16.0 // indirect
-	golang.org/x/net v0.22.0 // indirect
+	golang.org/x/net v0.23.0 // indirect
 	golang.org/x/sync v0.6.0 // indirect
 	golang.org/x/term v0.18.0 // indirect
 	golang.org/x/text v0.14.0 // indirect

go.sum

@@ -201,8 +201,8 @@ golang.org/x/mod v0.16.0/go.mod h1:hTbmBsO62+eylJbnUtE2MGJUyE7QWk4xUqPFrRgJ+7c=
 golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
 golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
 golang.org/x/net v0.0.0-20201021035429-f5854403a974/go.mod h1:sp8m0HH+o8qH0wwXwYZr8TS3Oi6o0r6Gce1SSxlDquU=
-golang.org/x/net v0.22.0 h1:9sGLhx7iRIHEiX0oAJ3MRZMUCElJgy7Br1nO+AMN3Tc=
-golang.org/x/net v0.22.0/go.mod h1:JKghWKKOSdJwpW2GEx0Ja7fmaKnMsbu+MWVZTokSYmg=
+golang.org/x/net v0.23.0 h1:7EYJ93RZ9vYSZAIb2x3lnuvqO5zneoD6IvWjuhfxjTs=
+golang.org/x/net v0.23.0/go.mod h1:JKghWKKOSdJwpW2GEx0Ja7fmaKnMsbu+MWVZTokSYmg=
 golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20201020160332-67f06af15bc9/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20210220032951-036812b2e83c/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
@@ -258,5 +258,5 @@ nhooyr.io/websocket v1.8.10 h1:mv4p+MnGrLDcPlBoWsvPP7XCzTYMXP9F9eIGoKbgx7Q=
 nhooyr.io/websocket v1.8.10/go.mod h1:rN9OFWIUwuxg4fR5tELlYC04bXYowCP9GX47ivo2l+c=
 software.sslmate.com/src/go-pkcs12 v0.4.0 h1:H2g08FrTvSFKUj+D309j1DPfk5APnIdAQAB8aEykJ5k=
 software.sslmate.com/src/go-pkcs12 v0.4.0/go.mod h1:Qiz0EyvDRJjjxGyUQa2cCNZn/wMyzrRJ/qcDXOQazLI=
-tailscale.com v1.65.0-pre.0.20240417162431-449be38e0381 h1:Wiz4SeARcNVLO7rmZy0mPj0RJHcSdHIQ8itrPkgNKyo=
-tailscale.com v1.65.0-pre.0.20240417162431-449be38e0381/go.mod h1:PVwaayzADTOctljVKj+M50OtQ0dOGYBLi2fdbOxo6vw=
+tailscale.com v1.65.0-pre.0.20240418182715-02c6af2a69a8 h1:8aRe1ZYCD2st8Yu+4l2p6RJsKxVyrh3b+EL1+OmqCHA=
+tailscale.com v1.65.0-pre.0.20240418182715-02c6af2a69a8/go.mod h1:Vzqw2fmVnsh7oT1iCqM1ZQlwQru9RjPJmH+srY0Af14=