android/ui: add support for remembering the last used exit node

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

@@ -238,6 +238,17 @@ val ColorScheme.secondaryButton: ButtonColors
         disabledContentColor = defaults.disabledContentColor)
   }
 
+val ColorScheme.button: 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

@@ -66,6 +66,7 @@ import com.tailscale.ipn.ui.model.IpnLocal
 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.button
 import com.tailscale.ipn.ui.theme.disabled
 import com.tailscale.ipn.ui.theme.listItem
 import com.tailscale.ipn.ui.theme.minTextSize
@@ -168,13 +169,26 @@ fun MainView(navigation: MainViewNavigation, viewModel: MainViewModel = viewMode
 
 @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 } }
+  // There's nothing to render if we haven't loaded the prefs yet
-  val location = peer?.Hostinfo?.Location
+  val prefs = maybePrefs.value ?: return
-  val name = peer?.ComputedName
+
-  val active = peer != null
+  // 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(
@@ -185,7 +199,7 @@ 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(),
               overlineContent = {
                 Text(
@@ -207,17 +221,24 @@ 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,
+                      colors =
-                      onClick = { viewModel.disableExitNode() }) {
+                          if (prefs.activeExitNodeID.isNullOrEmpty())
-                        Text(stringResource(R.string.stop))
+                              MaterialTheme.colorScheme.button
+                          else MaterialTheme.colorScheme.secondaryButton,
+                      onClick = { viewModel.toggleExitNode() }) {
+                        Text(
+                            if (prefs.activeExitNodeID.isNullOrEmpty())
+                                stringResource(id = R.string.enable)
+                            else stringResource(id = R.string.disable))
                       }
                 }
               })

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/MainViewModel.kt

@@ -3,10 +3,10 @@
 
 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
@@ -60,17 +60,30 @@ 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() {
+  fun toggleExitNode() {
+    val prefs = prefs.value ?: return
+
     LoadingIndicator.start()
-    val prefsOut = Ipn.MaskedPrefs()
+    if (prefs.activeExitNodeID != null) {
-    prefsOut.ExitNodeID = null
+      // We have an active exit node so we should keep it, but disable it
-    Client(viewModelScope).editPrefs(prefsOut) { LoadingIndicator.stop() }
+      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 an no prior exit node to enable")
+    }
   }
 }
 

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

@@ -129,7 +129,6 @@
     <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>
@@ -227,5 +226,7 @@
     <string name="welcome1">Tailscale is a mesh VPN for securely connecting your devices.</string>
     <string name="welcome2">All connections are device-to-device, so we never see your data. We collect and use your email address and name, as well as your device name, OS version, and IP address in order to help you to connect your devices and manage your settings. We log when you are connected to your network.</string>
         <string name="scan_to_connect_to_your_tailnet">Scan this QR code to log in to your tailnet</string>
+    <string name="disable">Disable</string>
+    <string name="enable">Enable</string>
 
 </resources>

go.mod

@@ -13,7 +13,7 @@ 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 v1.63.0-pre.0.20240404175649-853e3e29a0a6
+	tailscale.com v1.63.0-pre.0.20240409210520-8fa302661425
 )
 
 require (
@@ -102,3 +102,5 @@ require (
 	gvisor.dev/gvisor v0.0.0-20240306221502-ee1e1f6070e3 // indirect
 	nhooyr.io/websocket v1.8.10 // indirect
 )
+
+replace tailscale.com => tailscale.com v1.63.0-pre.0.20240411152250-b28c268c3ef5

go.sum

@@ -670,5 +670,5 @@ sigs.k8s.io/yaml v1.1.0/go.mod h1:UJmg0vDUVViEyp3mgSv9WPwZCDxu4rQW1olrI1uml+o=
 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=
 sourcegraph.com/sourcegraph/appdash v0.0.0-20190731080439-ebfcffb1b5c0/go.mod h1:hI742Nqp5OhwiqlzhgfbWU4mW4yO10fP+LoT9WOswdU=
-tailscale.com v1.63.0-pre.0.20240404175649-853e3e29a0a6 h1:olrk8pALH8inlmr4+euszd6cDI1dHhkRiFffxQ+fvpU=
+tailscale.com v1.63.0-pre.0.20240411152250-b28c268c3ef5 h1:hLoVSTmyJI7Ra+R4Pdvz6sdoa4ZQvRFMyxydHMqoidw=
-tailscale.com v1.63.0-pre.0.20240404175649-853e3e29a0a6/go.mod h1:6kGByHNxnFfK1i4gVpdtvpdS1HicHohWXnsfwmXy64I=
+tailscale.com v1.63.0-pre.0.20240411152250-b28c268c3ef5/go.mod h1:6kGByHNxnFfK1i4gVpdtvpdS1HicHohWXnsfwmXy64I=

go.toolchain.rev

@@ -1 +1 @@
-f86d7c8ef64a0f8a2516fc23652eee28abc8d8e0
+48d71857bf5352daaa10b61dd3e9b1c0dd51e27a