IpnViewModel: reset vpn state before login/reauth (#366)

Fixes ENG-3479

Clear routes when switching profiles and reauthenticating. This fixes an issue where previously set routes/DNS configs caused actions to fail.

Signed-off-by: kari-ts <kari@tailscale.com>

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

@@ -100,9 +100,19 @@ open class IpnViewModel : ViewModel() {
       }
     }
 
+    // Need to stop running before logging in to clear routes:
+    // https://linear.app/tailscale/issue/ENG-3441/routesdns-is-not-cleared-when-switching-profiles-or-reauthenticating
+    val stopThenLogin = {
+      Client(viewModelScope).editPrefs(Ipn.MaskedPrefs().apply { WantRunning = false }) { result ->
+        result
+            .onSuccess { loginAction() }
+            .onFailure { Log.e(TAG, "Error setting wantRunning to false: ${it.message}") }
+      }
+    }
+
     val startAction = {
       Client(viewModelScope).start(Ipn.Options(AuthKey = authKey)) { start ->
-        start.onFailure { completionHandler(Result.failure(it)) }.onSuccess { loginAction() }
+        start.onFailure { completionHandler(Result.failure(it)) }.onSuccess { stopThenLogin() }
       }
     }
 
@@ -164,11 +174,18 @@ open class IpnViewModel : ViewModel() {
   }
 
   fun switchProfile(profile: IpnLocal.LoginProfile, completionHandler: (Result<String>) -> Unit) {
+    val switchProfile = {
       Client(viewModelScope).switchProfile(profile) {
         startVPN()
         completionHandler(it)
       }
     }
+    Client(viewModelScope).editPrefs(Ipn.MaskedPrefs().apply { WantRunning = false }) { result ->
+      result
+          .onSuccess { switchProfile() }
+          .onFailure { Log.e(TAG, "Error setting wantRunning to false: ${it.message}") }
+    }
+  }
 
   fun addProfile(completionHandler: (Result<String>) -> Unit) {
     Client(viewModelScope).addProfile {