Hide required underlying caps APIs

VCN underlying network capabilities should be transport-dependent in
order to allow using anything other than the INTERNET capability for
VCN types that support wifi offload. Specifically, if underlying
network capabilities are not transport-dependent, and Wifi only ever
supports the INTERNET capability, the VCN is unable to utilize wifi
offload together with requiring NET_CAPABILITY_IMS or
NET_CAPABILITY_CBS, since the IMS or CBS capability would be required
for both cellular and wifi underlying networks.

Until such time as a per-transport capability set is allowed, hide
the exposedCapability pieces, and document that all underlying networks
MUST have INTERNET capability in order to be used.

Bug: 182219992
Test: atest FrameworksVcnTests
Test: atest CtsVcnTestCases
Change-Id: I50d7f1be42e0e001f1413a3d5fe8aa4b7afec223

core/java/android/net/vcn/VcnGatewayConnectionConfig.java

@@ -52,13 +52,12 @@ import java.util.concurrent.TimeUnit;
  * Network}s.
  *
  * <p>A VCN connection based on this configuration will be brought up dynamically based on device
- * settings, and filed NetworkRequests. Underlying networks will be selected based on the services
- * required by this configuration (as represented by network capabilities), and must be part of the
- * subscription group under which this configuration is registered (see {@link
+ * settings, and filed NetworkRequests. Underlying Networks must provide INTERNET connectivity, and
+ * must be part of the subscription group under which this configuration is registered (see {@link
  * VcnManager#setVcnConfig}).
  *
- * <p>As an abstraction of a cellular network, services that can be provided by a VCN network, or
- * required for underlying networks are limited to services provided by cellular networks:
+ * <p>As an abstraction of a cellular network, services that can be provided by a VCN network are
+ * limited to services provided by cellular networks:
  *
  * <ul>
  *   <li>{@link NetworkCapabilities#NET_CAPABILITY_MMS}
@@ -214,13 +213,6 @@ public final class VcnGatewayConnectionConfig {
             checkValidCapability(cap);
         }
 
-        Preconditions.checkArgument(
-                mUnderlyingCapabilities != null && !mUnderlyingCapabilities.isEmpty(),
-                "underlyingCapabilities was null or empty");
-        for (Integer cap : getAllUnderlyingCapabilities()) {
-            checkValidCapability(cap);
-        }
-
         Objects.requireNonNull(mRetryIntervalsMs, "retryIntervalsMs was null");
         validateRetryInterval(mRetryIntervalsMs);
 
@@ -295,7 +287,9 @@ public final class VcnGatewayConnectionConfig {
      *
      * @see Builder#addRequiredUnderlyingCapability(int)
      * @see Builder#removeRequiredUnderlyingCapability(int)
+     * @hide
      */
+    // TODO(b/182219992): Remove, and add when per-transport capabilities are supported
     @NonNull
     public int[] getRequiredUnderlyingCapabilities() {
         // Sorted set guarantees ordering
@@ -470,7 +464,9 @@ public final class VcnGatewayConnectionConfig {
          * @return this {@link Builder} instance, for chaining
          * @see VcnGatewayConnectionConfig for a list of capabilities may be required of underlying
          *     networks
+         * @hide
          */
+        // TODO(b/182219992): Remove, and add when per-transport capabilities are supported
         @NonNull
         public Builder addRequiredUnderlyingCapability(
                 @VcnSupportedCapability int underlyingCapability) {
@@ -492,7 +488,9 @@ public final class VcnGatewayConnectionConfig {
          * @return this {@link Builder} instance, for chaining
          * @see VcnGatewayConnectionConfig for a list of capabilities may be required of underlying
          *     networks
+         * @hide
          */
+        // TODO(b/182219992): Remove, and add when per-transport capabilities are supported
         @NonNull
         @SuppressLint("BuilderSetStyle") // For consistency with NetCaps.Builder add/removeCap
         public Builder removeRequiredUnderlyingCapability(

core/java/android/net/vcn/VcnManager.java

@@ -448,7 +448,7 @@ public class VcnManager {
          * @param networkCapabilities an array of NetworkCapabilities.NET_CAPABILITY_* capabilities
          *     for the Gateway Connection that encountered the error, for identification purposes.
          *     These will be a sorted list with no duplicates and will match {@link
-         *     VcnGatewayConnectionConfig#getRequiredUnderlyingCapabilities()} for one of the {@link
+         *     VcnGatewayConnectionConfig#getExposedCapabilities()} for one of the {@link
          *     VcnGatewayConnectionConfig}s set in the {@link VcnConfig} for this subscription
          *     group.
          * @param errorCode the code to indicate the error that occurred