Prevent VCN service from being registered twice

This patch is for migrating VCN registration from platform to
Tethering module. Becuase the system image has switched to use
mainline prebuilts, the mainline change cannot merged together
with the platform change. The plan is to update the mainline
prebuilt first and then merge the platform change. Thus there
will be a short window where ConnectivityServiceInitializerB
will be called twice to register VCN. This patch allows
ConnectivityServiceInitializerB to prevent the duplicate
registration.

This patch allows Tethering module to know whether VCN is moved
to mainline at runtime. If VCN is in mainline, Tethering
module (instead of SystemServer) will register the VCN service.

Bug: 385203616
Test: atest CtsVcnTestCases && FrameworksVcnTests
Test: verified registration on Android B and Android V
Flag: EXEMPT; no functional code change
Change-Id: If551167f4bafc39a592d8b325be3ceecf16f0b6e

2 files changed, 23 insertions, 2 deletions

diff --git a/packages/Vcn/service-b/Android.bp b/packages/Vcn/service-b/Android.bp
index 97574e6e35e3..aad534c3289c 100644
--- a/packages/Vcn/service-b/Android.bp
+++ b/packages/Vcn/service-b/Android.bp
@@ -29,7 +29,10 @@ filegroup {
             "vcn-location-flag/platform/com/android/server/vcn/VcnLocation.java",
         ],
     }),
-    visibility: ["//frameworks/base/services/core"],
+    visibility: [
+        "//frameworks/base/services/core",
+        "//packages/modules/Connectivity/service-t",
+    ],
 }
 
 // TODO: b/374174952 This library is only used in "service-connectivity-b-platform"
diff --git a/packages/Vcn/service-b/src/com/android/server/ConnectivityServiceInitializerB.java b/packages/Vcn/service-b/src/com/android/server/ConnectivityServiceInitializerB.java
index 81c7edf4adf1..b3f7eb5590c1 100644
--- a/packages/Vcn/service-b/src/com/android/server/ConnectivityServiceInitializerB.java
+++ b/packages/Vcn/service-b/src/com/android/server/ConnectivityServiceInitializerB.java
@@ -38,9 +38,27 @@ public final class ConnectivityServiceInitializerB extends SystemService {
     private static final String TAG = ConnectivityServiceInitializerB.class.getSimpleName();
     private final VcnManagementService mVcnManagementService;
 
+    // STOPSHIP: b/385203616 This static flag is for handling a temporary case when the mainline
+    // module prebuilt has updated to register the VCN but the platform change to remove
+    // registration is not merged. After mainline prebuilt is updated, we should merge the platform
+    // ASAP and remove this static check. This check is safe because both mainline and platform
+    // registration are triggered from the same method on the same thread.
+    private static boolean sIsRegistered = false;
+
     public ConnectivityServiceInitializerB(Context context) {
         super(context);
-        mVcnManagementService = VcnManagementService.create(context);
+
+        if (!sIsRegistered) {
+            mVcnManagementService = VcnManagementService.create(context);
+            sIsRegistered = true;
+        } else {
+            mVcnManagementService = null;
+            Log.e(
+                    TAG,
+                    "Ignore this registration since VCN is already registered. It will happen when"
+                        + " the mainline module prebuilt has updated to register the VCN but the"
+                        + " platform change to remove registration is not merged.");
+        }
     }
 
     @Override