Downgrade list of subIds in NetworkCapabilities to @SystemApi

This change downgrades API visibility for the list-of-subIds in the
NetworkCapabilities to SystemApi

Bug: 175662146
Test: atest NetworkCapabilitiesTest#testSubIds
Test: atest FrameworksNetTests
Change-Id: I372fa9eaa7585aefd1710948ca007456feedd578

framework/api/current.txt

@@ -298,7 +298,6 @@ package android.net {
     method @Nullable public android.net.NetworkSpecifier getNetworkSpecifier();
     method public int getOwnerUid();
     method public int getSignalStrength();
-    method @NonNull public java.util.Set<java.lang.Integer> getSubIds();
     method @Nullable public android.net.TransportInfo getTransportInfo();
     method public boolean hasCapability(int);
     method public boolean hasTransport(int);
@@ -408,7 +407,6 @@ package android.net {
     method public android.net.NetworkRequest.Builder removeTransportType(int);
     method @Deprecated public android.net.NetworkRequest.Builder setNetworkSpecifier(String);
     method public android.net.NetworkRequest.Builder setNetworkSpecifier(android.net.NetworkSpecifier);
-    method @NonNull public android.net.NetworkRequest.Builder setSubIds(@NonNull java.util.Set<java.lang.Integer>);
   }
 
   public class ParseException extends java.lang.RuntimeException {

framework/api/system-current.txt

@@ -274,6 +274,7 @@ package android.net {
   public final class NetworkCapabilities implements android.os.Parcelable {
     method @NonNull public int[] getAdministratorUids();
     method @Nullable public String getSsid();
+    method @NonNull public java.util.Set<java.lang.Integer> getSubIds();
     method @NonNull public int[] getTransportTypes();
     method public boolean isPrivateDnsBroken();
     method public boolean satisfiedByNetworkCapabilities(@Nullable android.net.NetworkCapabilities);
@@ -327,6 +328,7 @@ package android.net {
 
   public static class NetworkRequest.Builder {
     method @NonNull @RequiresPermission(android.Manifest.permission.NETWORK_SIGNAL_STRENGTH_WAKEUP) public android.net.NetworkRequest.Builder setSignalStrength(int);
+    method @NonNull public android.net.NetworkRequest.Builder setSubIds(@NonNull java.util.Set<java.lang.Integer>);
   }
 
   public final class NetworkScore implements android.os.Parcelable {

framework/src/android/net/NetworkCapabilities.java

@@ -2346,9 +2346,15 @@ public final class NetworkCapabilities implements Parcelable {
 
     /**
      * Gets the subscription ID set that associated to this network or request.
+     *
+     * <p>Instances of NetworkCapabilities will only have this field populated by the system if the
+     * receiver holds the NETWORK_FACTORY permission. In all other cases, it will be the empty set.
+     *
      * @return
+     * @hide
      */
     @NonNull
+    @SystemApi
     public Set<Integer> getSubIds() {
         return new ArraySet<>(mSubIds);
     }
@@ -2713,10 +2719,17 @@ public final class NetworkCapabilities implements Parcelable {
         /**
          * Set the subscription ID set.
          *
+         * <p>SubIds are populated in NetworkCapability instances from the system only for callers
+         * that hold the NETWORK_FACTORY permission. Similarly, the system will reject any
+         * NetworkRequests filed with a non-empty set of subIds unless the caller holds the
+         * NETWORK_FACTORY permission.
+         *
          * @param subIds a set that represent the subscription IDs. Empty if clean up.
          * @return this builder.
+         * @hide
          */
         @NonNull
+        @SystemApi
         public Builder setSubIds(@NonNull final Set<Integer> subIds) {
             mCaps.setSubIds(subIds);
             return this;

framework/src/android/net/NetworkRequest.java

@@ -501,9 +501,14 @@ public class NetworkRequest implements Parcelable {
          * A network will satisfy this request only if it matches one of the subIds in this set.
          * An empty set matches all networks, including those without a subId.
          *
+         * <p>Registering a NetworkRequest with a non-empty set of subIds requires the
+         * NETWORK_FACTORY permission.
+         *
          * @param subIds A {@code Set} that represents subscription IDs.
+         * @hide
          */
         @NonNull
+        @SystemApi
         public Builder setSubIds(@NonNull Set<Integer> subIds) {
             mNetworkCapabilities.setSubIds(subIds);
             return this;