Mark several NetworkAgentInfo members @NonNull and address TODO.

1. network cannot be null because it's final and the only caller
   of the constructor passes in a fresh copy.
2. linkProperties cannot be null because:
   - The only caller of the constructor passes in a fresh copy.
   - The only assignment to nai.linkProperties is in
     updateLinkProperties, and that dereferences newLp a few
     lines before assigning it.
3. networkCapabilities cannot be null because:
   - The only caller of the constructor passes in a fresh copy.
   - There are no direct assignments to nai.networkCapabilities.
   - All 4 assignments happen via getAndSetNetworkCapabilities:
     - registerNetworkAgentInternal, updateCapabilities and
       applyBackgroundChangeForRematch all pass in the return
       value of mixInCapabilities, which is always non-null.
     - updateNetworkInfo re-assigns the capabilities that were
       already set in the object.
4. networkAgentConfig cannot be null because it's final and
   the only caller of the NetworkAgentInfo constructor passes
   in a fresh copy.

Address a TODO in ConnectivityService to remove a check for the
nai's capabilities being null.

Also fix a style nit pointed out by the linter.

Test: atest FrameworksNetTests
Change-Id: I2e265f1c60a73d6da0222dd6711bc53c32db06ec

2 files changed, 18 insertions, 23 deletions

diff --git a/services/core/java/com/android/server/ConnectivityService.java b/services/core/java/com/android/server/ConnectivityService.java
index 1b7912e704a1..55774c4da1d0 100644
--- a/services/core/java/com/android/server/ConnectivityService.java
+++ b/services/core/java/com/android/server/ConnectivityService.java
@@ -6590,7 +6590,7 @@ public class ConnectivityService extends IConnectivityManager.Stub
         }
 
         // Don't modify caller's NetworkCapabilities.
-        NetworkCapabilities newNc = new NetworkCapabilities(nc);
+        final NetworkCapabilities newNc = new NetworkCapabilities(nc);
         if (nai.lastValidated) {
             newNc.addCapability(NET_CAPABILITY_VALIDATED);
         } else {
@@ -6678,26 +6678,21 @@ public class ConnectivityService extends IConnectivityManager.Stub
             notifyNetworkCallbacks(nai, ConnectivityManager.CALLBACK_CAP_CHANGED);
         }
 
-        // TODO : static analysis indicates that prevNc can't be null here (getAndSetNetworkCaps
-        // never returns null), so mark the relevant members and functions in nai as @NonNull and
-        // remove this test
-        if (prevNc != null) {
-            final boolean oldMetered = prevNc.isMetered();
-            final boolean newMetered = newNc.isMetered();
-            final boolean meteredChanged = oldMetered != newMetered;
+        final boolean oldMetered = prevNc.isMetered();
+        final boolean newMetered = newNc.isMetered();
+        final boolean meteredChanged = oldMetered != newMetered;
 
-            if (meteredChanged) {
-                maybeNotifyNetworkBlocked(nai, oldMetered, newMetered, mRestrictBackground,
-                        mRestrictBackground, mVpnBlockedUidRanges, mVpnBlockedUidRanges);
-            }
+        if (meteredChanged) {
+            maybeNotifyNetworkBlocked(nai, oldMetered, newMetered, mRestrictBackground,
+                    mRestrictBackground, mVpnBlockedUidRanges, mVpnBlockedUidRanges);
+        }
 
-            final boolean roamingChanged = prevNc.hasCapability(NET_CAPABILITY_NOT_ROAMING) !=
-                    newNc.hasCapability(NET_CAPABILITY_NOT_ROAMING);
+        final boolean roamingChanged = prevNc.hasCapability(NET_CAPABILITY_NOT_ROAMING)
+                != newNc.hasCapability(NET_CAPABILITY_NOT_ROAMING);
 
-            // Report changes that are interesting for network statistics tracking.
-            if (meteredChanged || roamingChanged) {
-                notifyIfacesChangedForNetworkStats();
-            }
+        // Report changes that are interesting for network statistics tracking.
+        if (meteredChanged || roamingChanged) {
+            notifyIfacesChangedForNetworkStats();
         }
 
         // This network might have been underlying another network. Propagate its capabilities.
diff --git a/services/core/java/com/android/server/connectivity/NetworkAgentInfo.java b/services/core/java/com/android/server/connectivity/NetworkAgentInfo.java
index b0a73f105725..8215e8879d86 100644
--- a/services/core/java/com/android/server/connectivity/NetworkAgentInfo.java
+++ b/services/core/java/com/android/server/connectivity/NetworkAgentInfo.java
@@ -136,12 +136,12 @@ public class NetworkAgentInfo implements Comparable<NetworkAgentInfo> {
     // This Network object should always be used if possible, so as to encourage reuse of the
     // enclosed socket factory and connection pool.  Avoid creating other Network objects.
     // This Network object is always valid.
-    public final Network network;
-    public LinkProperties linkProperties;
+    @NonNull public final Network network;
+    @NonNull public LinkProperties linkProperties;
     // This should only be modified by ConnectivityService, via setNetworkCapabilities().
     // TODO: make this private with a getter.
-    public NetworkCapabilities networkCapabilities;
-    public final NetworkAgentConfig networkAgentConfig;
+    @NonNull public NetworkCapabilities networkCapabilities;
+    @NonNull public final NetworkAgentConfig networkAgentConfig;
 
     // Underlying networks declared by the agent. Only set if supportsUnderlyingNetworks is true.
     // The networks in this list might be declared by a VPN app using setUnderlyingNetworks and are
@@ -603,7 +603,7 @@ public class NetworkAgentInfo implements Comparable<NetworkAgentInfo> {
      *
      * @return the old capabilities of this network.
      */
-    public synchronized NetworkCapabilities getAndSetNetworkCapabilities(
+    @NonNull public synchronized NetworkCapabilities getAndSetNetworkCapabilities(
             @NonNull final NetworkCapabilities nc) {
         final NetworkCapabilities oldNc = networkCapabilities;
         networkCapabilities = nc;