1 files changed, 152 insertions, 1 deletions
diff --git a/framework/src/android/net/NetworkProvider.java b/framework/src/android/net/NetworkProvider.java
index 14cb51c85d..8f93047cf8 100644
--- a/framework/src/android/net/NetworkProvider.java
+++ b/framework/src/android/net/NetworkProvider.java
@@ -28,6 +28,11 @@ import android.os.Message;
 import android.os.Messenger;
 import android.util.Log;
 
+import com.android.internal.annotations.GuardedBy;
+
+import java.util.ArrayList;
+import java.util.concurrent.Executor;
+
 /**
  * Base class for network providers such as telephony or Wi-Fi. NetworkProviders connect the device
  * to networks and makes them available to the core network stack by creating
@@ -78,7 +83,9 @@ public class NetworkProvider {
      */
     @SystemApi
     public NetworkProvider(@NonNull Context context, @NonNull Looper looper, @NonNull String name) {
-        Handler handler = new Handler(looper) {
+        // TODO (b/174636568) : this class should be able to cache an instance of
+        // ConnectivityManager so it doesn't have to fetch it again every time.
+        final Handler handler = new Handler(looper) {
             @Override
             public void handleMessage(Message m) {
                 switch (m.what) {
@@ -159,4 +166,148 @@ public class NetworkProvider {
     public void declareNetworkRequestUnfulfillable(@NonNull NetworkRequest request) {
         ConnectivityManager.from(mContext).declareNetworkRequestUnfulfillable(request);
     }
+
+    /** @hide */
+    // TODO : make @SystemApi when the impl is complete
+    public interface NetworkOfferCallback {
+        /** Called by the system when this offer is needed to satisfy some networking request. */
+        void onOfferNeeded(@NonNull NetworkRequest request, int providerId);
+        /** Called by the system when this offer is no longer needed. */
+        void onOfferUnneeded(@NonNull NetworkRequest request);
+    }
+
+    private class NetworkOfferCallbackProxy extends INetworkOfferCallback.Stub {
+        @NonNull public final NetworkOfferCallback callback;
+        @NonNull private final Executor mExecutor;
+
+        NetworkOfferCallbackProxy(@NonNull final NetworkOfferCallback callback,
+                @NonNull final Executor executor) {
+            this.callback = callback;
+            this.mExecutor = executor;
+        }
+
+        @Override
+        public void onOfferNeeded(final @NonNull NetworkRequest request,
+                final int providerId) {
+            mExecutor.execute(() -> callback.onOfferNeeded(request, providerId));
+        }
+
+        @Override
+        public void onOfferUnneeded(final @NonNull NetworkRequest request) {
+            mExecutor.execute(() -> callback.onOfferUnneeded(request));
+        }
+    }
+
+    @GuardedBy("mProxies")
+    @NonNull private final ArrayList<NetworkOfferCallbackProxy> mProxies = new ArrayList<>();
+
+    // Returns the proxy associated with this callback, or null if none.
+    @Nullable
+    private NetworkOfferCallbackProxy findProxyForCallback(@NonNull final NetworkOfferCallback cb) {
+        synchronized (mProxies) {
+            for (final NetworkOfferCallbackProxy p : mProxies) {
+                if (p.callback == cb) return p;
+            }
+        }
+        return null;
+    }
+
+    /**
+     * Register or update an offer for network with the passed caps and score.
+     *
+     * A NetworkProvider's job is to provide networks. This function is how a provider tells the
+     * connectivity stack what kind of network it may provide. The score and caps arguments act
+     * as filters that the connectivity stack uses to tell when the offer is necessary. When an
+     * offer might be advantageous over existing networks, the provider will receive a call to
+     * the associated callback's {@link NetworkOfferCallback#onOfferNeeded} method. The provider
+     * should then try to bring up this network. When an offer is no longer needed, the stack
+     * will inform the provider by calling {@link NetworkOfferCallback#onOfferUnneeded}. The
+     * provider should stop trying to bring up such a network, or disconnect it if it already has
+     * one.
+     *
+     * The stack determines what offers are needed according to what networks are currently
+     * available to the system, and what networking requests are made by applications. If an
+     * offer looks like it could be a better choice than any existing network for any particular
+     * request, that's when the stack decides the offer is needed. If the current networking
+     * requests are all satisfied by networks that this offer can't possibly be a better match
+     * for, that's when the offer is unneeded. An offer starts off as unneeded ; the provider
+     * should not try to bring up the network until {@link NetworkOfferCallback#onOfferNeeded}
+     * is called.
+     *
+     * Note that the offers are non-binding to the providers, in particular because providers
+     * often don't know if they will be able to bring up such a network at any given time. For
+     * example, no wireless network may be in range when the offer is needed. This is fine and
+     * expected ; the provider should simply continue to try to bring up the network and do so
+     * if/when it becomes possible. In the mean time, the stack will continue to satisfy requests
+     * with the best network currently available, or if none, keep the apps informed that no
+     * network can currently satisfy this request. When/if the provider can bring up the network,
+     * the connectivity stack will match it against requests, and inform interested apps of the
+     * availability of this network. This may, in turn, render the offer of some other provider
+     * unneeded if all requests it used to satisfy are now better served by this network.
+     *
+     * A network can become unneeded for a reason like the above : whether the provider managed
+     * to bring up the offered network after it became needed or not, some other provider may
+     * bring up a better network than this one, making this offer unneeded. A network may also
+     * become unneeded if the application making the request withdrew it (for example, after it
+     * is done transferring data, or if the user canceled an operation).
+     *
+     * The capabilities and score act as filters as to what requests the provider will see.
+     * They are not promises, but for best performance, the providers should strive to put
+     * as much known information as possible in the offer. For capabilities in particular, it
+     * should put all NetworkAgent-managed capabilities a network may have, even if it doesn't
+     * have them at first. This applies to INTERNET, for example ; if a provider thinks the
+     * network it can bring up for this offer may offer Internet access it should include the
+     * INTERNET bit. It's fine if the brought up network ends up not actually having INTERNET.
+     *
+     * TODO : in the future, to avoid possible infinite loops, there should be constraints on
+     * what can be put in capabilities of networks brought up for an offer. If a provider might
+     * bring up a network with or without INTERNET, then it should file two offers : this will
+     * let it know precisely what networks are needed, so it can avoid bringing up networks that
+     * won't actually satisfy requests and remove the risk for bring-up-bring-down loops.
+     *
+     * @hide
+     */
+    // TODO : make @SystemApi when the impl is complete
+    @RequiresPermission(android.Manifest.permission.NETWORK_FACTORY)
+    public void offerNetwork(@NonNull final NetworkScore score,
+            @NonNull final NetworkCapabilities caps, @NonNull final Executor executor,
+            @NonNull final NetworkOfferCallback callback) {
+        NetworkOfferCallbackProxy proxy = null;
+        synchronized (mProxies) {
+            for (final NetworkOfferCallbackProxy existingProxy : mProxies) {
+                if (existingProxy.callback == callback) {
+                    proxy = existingProxy;
+                    break;
+                }
+            }
+            if (null == proxy) {
+                proxy = new NetworkOfferCallbackProxy(callback, executor);
+                mProxies.add(proxy);
+            }
+        }
+        mContext.getSystemService(ConnectivityManager.class).offerNetwork(this, score, caps, proxy);
+    }
+
+    /**
+     * Withdraw a network offer previously made to the networking stack.
+     *
+     * If a provider can no longer provide a network they offered, it should call this method.
+     * An example of usage could be if the hardware necessary to bring up the network was turned
+     * off in UI by the user. Note that because offers are never binding, the provider might
+     * alternatively decide not to withdraw this offer and simply refuse to bring up the network
+     * even when it's needed. However, withdrawing the request is slightly more resource-efficient
+     * because the networking stack won't have to compare this offer to exiting networks to see
+     * if it could beat any of them, and may be advantageous to the provider's implementation that
+     * can rely on no longer receiving callbacks for a network that they can't bring up anyways.
+     *
+     * @hide
+     */
+    // TODO : make @SystemApi when the impl is complete
+    @RequiresPermission(android.Manifest.permission.NETWORK_FACTORY)
+    public void unofferNetwork(final @NonNull NetworkOfferCallback callback) {
+        final NetworkOfferCallbackProxy proxy = findProxyForCallback(callback);
+        if (null == proxy) return;
+        mProxies.remove(proxy);
+        mContext.getSystemService(ConnectivityManager.class).unofferNetwork(proxy);
+    }
 }