Fix a ConcurrentModificationException crash.

This is a pinpoint fix against the bug listed below. While a client
is synchronously reading the LinkProperties of a network, the
ConnectivityServiceThread is updating its properties. Make sure
that update is done atomically.

This is a stopgap countermeasure against a problem that is
pervasive with usage of LinkProperties, but fixing the problem
itself will happen later.

Bug: 80077223
Test: runtest frameworks-net
Change-Id: I9302f8fb5303cb39aa82691d4f6d7f38707a41fa

services/core/java/com/android/server/ConnectivityService.java

@@ -4674,7 +4674,7 @@ public class ConnectivityService extends IConnectivityManager.Stub
     }
 
     private void updateLinkProperties(NetworkAgentInfo networkAgent, LinkProperties oldLp) {
-        LinkProperties newLp = networkAgent.linkProperties;
+        LinkProperties newLp = new LinkProperties(networkAgent.linkProperties);
         int netId = networkAgent.network.netId;
 
         // The NetworkAgentInfo does not know whether clatd is running on its network or not. Before
@@ -4708,6 +4708,9 @@ public class ConnectivityService extends IConnectivityManager.Stub
         }
         // TODO - move this check to cover the whole function
         if (!Objects.equals(newLp, oldLp)) {
+            synchronized (networkAgent) {
+                networkAgent.linkProperties = newLp;
+            }
             notifyIfacesChangedForNetworkStats();
             notifyNetworkCallbacks(networkAgent, ConnectivityManager.CALLBACK_IP_CHANGED);
         }