Allow non-VPNs to have underlying networks.

Certain network types, like the VCN, have underlying
networks for the purpose of data usage, but do not want to
propagate the underlying network capabilities.

Allow these networks to set underlying networks, but continue
not to propagate the capabilities.

Bug: 190620024
Test: new unit test
Original-Change: https://android-review.googlesource.com/1753619
Merged-In: I53d6080f48707ff3c37fbfbef534284ba77a7432
Change-Id: I53d6080f48707ff3c37fbfbef534284ba77a7432
diff --git a/service/src/com/android/server/ConnectivityService.java b/service/src/com/android/server/ConnectivityService.java
index df1cfa3..0b61247 100644
--- a/service/src/com/android/server/ConnectivityService.java
+++ b/service/src/com/android/server/ConnectivityService.java
@@ -3269,11 +3269,6 @@
                 }
                 case NetworkAgent.EVENT_UNDERLYING_NETWORKS_CHANGED: {
                     // TODO: prevent loops, e.g., if a network declares itself as underlying.
-                    if (!nai.supportsUnderlyingNetworks()) {
-                        Log.wtf(TAG, "Non-virtual networks cannot have underlying networks");
-                        break;
-                    }
-
                     final List<Network> underlying = (List<Network>) arg.second;
 
                     if (isLegacyLockdownNai(nai)
@@ -5286,12 +5281,12 @@
      *         information, e.g underlying ifaces.
      */
     private UnderlyingNetworkInfo createVpnInfo(NetworkAgentInfo nai) {
-        if (!nai.isVPN()) return null;
-
         Network[] underlyingNetworks = nai.declaredUnderlyingNetworks;
         // see VpnService.setUnderlyingNetworks()'s javadoc about how to interpret
         // the underlyingNetworks list.
-        if (underlyingNetworks == null) {
+        // TODO: stop using propagateUnderlyingCapabilities here, for example, by always
+        // initializing NetworkAgentInfo#declaredUnderlyingNetworks to an empty array.
+        if (underlyingNetworks == null && nai.propagateUnderlyingCapabilities()) {
             final NetworkAgentInfo defaultNai = getDefaultNetworkForUid(
                     nai.networkCapabilities.getOwnerUid());
             if (defaultNai != null) {
@@ -5340,7 +5335,7 @@
     private boolean hasUnderlyingNetwork(NetworkAgentInfo nai, Network network) {
         // TODO: support more than one level of underlying networks, either via a fixed-depth search
         // (e.g., 2 levels of underlying networks), or via loop detection, or....
-        if (!nai.supportsUnderlyingNetworks()) return false;
+        if (!nai.propagateUnderlyingCapabilities()) return false;
         final Network[] underlying = underlyingNetworksOrDefault(
                 nai.networkCapabilities.getOwnerUid(), nai.declaredUnderlyingNetworks);
         return CollectionUtils.contains(underlying, network);
@@ -7304,7 +7299,7 @@
             newNc.addCapability(NET_CAPABILITY_NOT_ROAMING);
         }
 
-        if (nai.supportsUnderlyingNetworks()) {
+        if (nai.propagateUnderlyingCapabilities()) {
             applyUnderlyingCapabilities(nai.declaredUnderlyingNetworks, nai.declaredCapabilities,
                     newNc);
         }
@@ -8442,7 +8437,7 @@
             networkAgent.networkCapabilities.addCapability(NET_CAPABILITY_FOREGROUND);
 
             if (!createNativeNetwork(networkAgent)) return;
-            if (networkAgent.supportsUnderlyingNetworks()) {
+            if (networkAgent.propagateUnderlyingCapabilities()) {
                 // Initialize the network's capabilities to their starting values according to the
                 // underlying networks. This ensures that the capabilities are correct before
                 // anything happens to the network.
@@ -9351,7 +9346,7 @@
 
     private boolean ownsVpnRunningOverNetwork(int uid, Network network) {
         for (NetworkAgentInfo virtual : mNetworkAgentInfos) {
-            if (virtual.supportsUnderlyingNetworks()
+            if (virtual.propagateUnderlyingCapabilities()
                     && virtual.networkCapabilities.getOwnerUid() == uid
                     && CollectionUtils.contains(virtual.declaredUnderlyingNetworks, network)) {
                 return true;
diff --git a/service/src/com/android/server/connectivity/NetworkAgentInfo.java b/service/src/com/android/server/connectivity/NetworkAgentInfo.java
index 18becd4..bbf523a 100644
--- a/service/src/com/android/server/connectivity/NetworkAgentInfo.java
+++ b/service/src/com/android/server/connectivity/NetworkAgentInfo.java
@@ -157,8 +157,8 @@
     @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
+    // Underlying networks declared by the agent.
+    // The networks in this list might be declared by a VPN using setUnderlyingNetworks and are
     // not guaranteed to be current or correct, or even to exist.
     //
     // This array is read and iterated on multiple threads with no locking so its contents must
@@ -168,7 +168,7 @@
 
     // The capabilities originally announced by the NetworkAgent, regardless of any capabilities
     // that were added or removed due to this network's underlying networks.
-    // Only set if #supportsUnderlyingNetworks is true.
+    // Only set if #propagateUnderlyingCapabilities is true.
     public @Nullable NetworkCapabilities declaredCapabilities;
 
     // Indicates if netd has been told to create this Network. From this point on the appropriate
@@ -898,8 +898,11 @@
         return networkCapabilities.hasTransport(NetworkCapabilities.TRANSPORT_VPN);
     }
 
-    /** Whether this network might have underlying networks. Currently only true for VPNs. */
-    public boolean supportsUnderlyingNetworks() {
+    /**
+     * Whether this network should propagate the capabilities from its underlying networks.
+     * Currently only true for VPNs.
+     */
+    public boolean propagateUnderlyingCapabilities() {
         return isVPN();
     }