Tidy up VPN code

This commit addressed the comments in different commits, it did
- Make isVpnApp() to be a static method.
- Rename getRedactedNetworkCapabilitiesOfUnderlyingNetwork to
  getRedactedNetworkCapabilities and rename
  getRedactedLinkPropertiesOfUnderlyingNetwork to
  getRedactedLinkProperties.
- Reduce the scope of synchronized block in handleSessionLost().
- Fast return when there is an IllegalArgumentException in
  handleSessionLost().
- Remove inaccurate comment.
- Update the document of mCurrentToken.
- Define an initial token value of IKE session.
- Add "/* exeception */" annotation to handleSessionLost(null)
  calls.

Bug: 236409954
Test: atest FrameworksNetTests:VpnTest
Change-Id: I8c938f8796345dc2eee6c8eff513b0f993bc8165
(cherry picked from commit 7146e2cb02)
Merged-In: I8c938f8796345dc2eee6c8eff513b0f993bc8165

services/core/java/com/android/server/connectivity/Vpn.java

@@ -222,6 +222,11 @@ public class Vpn {
      */
     private static final int VPN_DEFAULT_SCORE = 101;
 
+    /**
+     * The initial token value of IKE session.
+     */
+    private static final int STARTING_TOKEN = -1;
+
     // TODO: create separate trackers for each unique VPN to support
     // automated reconnection
 
@@ -795,7 +800,7 @@ public class Vpn {
         }
     }
 
-    private boolean isVpnApp(String packageName) {
+    private static boolean isVpnApp(String packageName) {
         return packageName != null && !VpnConfig.LEGACY_VPN.equals(packageName);
     }
 
@@ -2593,7 +2598,7 @@ public class Vpn {
     }
 
     @Nullable
-    protected synchronized NetworkCapabilities getRedactedNetworkCapabilitiesOfUnderlyingNetwork(
+    private synchronized NetworkCapabilities getRedactedNetworkCapabilities(
             NetworkCapabilities nc) {
         if (nc == null) return null;
         return mConnectivityManager.getRedactedNetworkCapabilitiesForPackage(
@@ -2601,8 +2606,7 @@ public class Vpn {
     }
 
     @Nullable
-    protected synchronized LinkProperties getRedactedLinkPropertiesOfUnderlyingNetwork(
+    private synchronized LinkProperties getRedactedLinkProperties(LinkProperties lp) {
-            LinkProperties lp) {
         if (lp == null) return null;
         return mConnectivityManager.getRedactedLinkPropertiesForPackage(lp, mOwnerUID, mPackage);
     }
@@ -2716,11 +2720,13 @@ public class Vpn {
         private boolean mIsRunning = true;
 
         /**
-         * The token used by the primary/current/active IKE session.
+         * The token that identifies the most recently created IKE session.
          *
-         * <p>This token MUST be updated when the VPN switches to use a new IKE session.
+         * <p>This token is monotonically increasing and will never be reset in the lifetime of this
+         * Ikev2VpnRunner, but it does get reset across runs. It also MUST be accessed on the
+         * executor thread and updated when a new IKE session is created.
          */
-        private int mCurrentToken = -1;
+        private int mCurrentToken = STARTING_TOKEN;
 
         @Nullable private IpSecTunnelInterface mTunnelIface;
         @Nullable private Network mActiveNetwork;
@@ -3223,7 +3229,7 @@ public class Vpn {
                         mExecutor.schedule(
                                 () -> {
                                     if (isActiveToken(token)) {
-                                        handleSessionLost(null, network);
+                                        handleSessionLost(null /* exception */, network);
                                     } else {
                                         Log.d(
                                                 TAG,
@@ -3240,7 +3246,7 @@ public class Vpn {
                                 TimeUnit.MILLISECONDS);
             } else {
                 Log.d(TAG, "Call handleSessionLost for losing network " + network);
-                handleSessionLost(null, network);
+                handleSessionLost(null /* exception */, network);
             }
         }
 
@@ -3311,13 +3317,15 @@ public class Vpn {
             // already terminated due to other failures.
             cancelHandleNetworkLostTimeout();
 
-            synchronized (Vpn.this) {
-                // Ignore stale runner.
-                if (mVpnRunner != this) return;
-
             String category = null;
             int errorClass = -1;
             int errorCode = -1;
+            if (exception instanceof IllegalArgumentException) {
+                // Failed to build IKE/ChildSessionParams; fatal profile configuration error
+                markFailedAndDisconnect(exception);
+                return;
+            }
+
             if (exception instanceof IkeProtocolException) {
                 final IkeProtocolException ikeException = (IkeProtocolException) exception;
                 category = VpnManager.CATEGORY_EVENT_IKE_ERROR;
@@ -3335,13 +3343,8 @@ public class Vpn {
                         break;
                     // All other cases possibly recoverable.
                     default:
-                            // All the above failures are configuration errors, and are terminal
                         errorClass = VpnManager.ERROR_CLASS_RECOVERABLE;
                 }
-                } else if (exception instanceof IllegalArgumentException) {
-                    // Failed to build IKE/ChildSessionParams; fatal profile configuration error
-                    markFailedAndDisconnect(exception);
-                    return;
             } else if (exception instanceof IkeNetworkLostException) {
                 category = VpnManager.CATEGORY_EVENT_NETWORK_ERROR;
                 errorClass = VpnManager.ERROR_CLASS_RECOVERABLE;
@@ -3360,16 +3363,19 @@ public class Vpn {
                 Log.wtf(TAG, "onSessionLost: exception = " + exception);
             }
 
+            synchronized (Vpn.this) {
+                // Ignore stale runner.
+                if (mVpnRunner != this) return;
+
                 // TODO(b/230548427): Remove SDK check once VPN related stuff are
                 //  decoupled from ConnectivityServiceTest.
                 if (SdkLevel.isAtLeastT() && category != null && isVpnApp(mPackage)) {
                     sendEventToVpnManagerApp(category, errorClass, errorCode,
                             getPackage(), mSessionKey, makeVpnProfileStateLocked(),
                             mActiveNetwork,
-                            getRedactedNetworkCapabilitiesOfUnderlyingNetwork(
+                            getRedactedNetworkCapabilities(mUnderlyingNetworkCapabilities),
-                                    mUnderlyingNetworkCapabilities),
+                            getRedactedLinkProperties(mUnderlyingLinkProperties));
-                            getRedactedLinkPropertiesOfUnderlyingNetwork(
+                }
-                                    mUnderlyingLinkProperties));
             }
 
             if (errorClass == VpnManager.ERROR_CLASS_NOT_RECOVERABLE) {
@@ -3378,7 +3384,6 @@ public class Vpn {
             } else {
                 scheduleRetryNewIkeSession();
             }
-            }
 
             mUnderlyingNetworkCapabilities = null;
             mUnderlyingLinkProperties = null;