Merge "[NS04] Introduce Network Offers and their callbacks"

framework/src/android/net/ConnectivityManager.java

@@ -3337,7 +3337,60 @@ public class ConnectivityManager {
         provider.setProviderId(NetworkProvider.ID_NONE);
     }
 
+    /**
+     * Register or update a network offer with ConnectivityService.
+     *
+     * ConnectivityService keeps track of offers made by the various providers and matches
+     * them to networking requests made by apps or the system. The provider supplies a score
+     * and the capabilities of the network it might be able to bring up ; these act as filters
+     * used by ConnectivityService to only send those requests that can be fulfilled by the
+     * provider.
+     *
+     * The provider is under no obligation to be able to bring up the network it offers at any
+     * given time. Instead, this mechanism is meant to limit requests received by providers
+     * to those they actually have a chance to fulfill, as providers don't have a way to compare
+     * the quality of the network satisfying a given request to their own offer.
+     *
+     * An offer can be updated by calling this again with the same callback object. This is
+     * similar to calling unofferNetwork and offerNetwork again, but will only update the
+     * provider with the changes caused by the changes in the offer.
+     *
+     * @param provider The provider making this offer.
+     * @param score The prospective score of the network.
+     * @param caps The prospective capabilities of the network.
+     * @param callback The callback to call when this offer is needed or unneeded.
+     * @hide
+     */
+    @RequiresPermission(anyOf = {
+            NetworkStack.PERMISSION_MAINLINE_NETWORK_STACK,
+            android.Manifest.permission.NETWORK_FACTORY})
+    public void offerNetwork(@NonNull final NetworkProvider provider,
+            @NonNull final NetworkScore score, @NonNull final NetworkCapabilities caps,
+            @NonNull final INetworkOfferCallback callback) {
+        try {
+            mService.offerNetwork(Objects.requireNonNull(provider.getMessenger(), "null messenger"),
+                    Objects.requireNonNull(score, "null score"),
+                    Objects.requireNonNull(caps, "null caps"),
+                    Objects.requireNonNull(callback, "null callback"));
+        } catch (RemoteException e) {
+            throw e.rethrowFromSystemServer();
+        }
+    }
 
+    /**
+     * Withdraw a network offer made with {@link #offerNetwork}.
+     *
+     * @param callback The callback passed at registration time. This must be the same object
+     *                 that was passed to {@link #offerNetwork}
+     * @hide
+     */
+    public void unofferNetwork(@NonNull final INetworkOfferCallback callback) {
+        try {
+            mService.unofferNetwork(Objects.requireNonNull(callback));
+        } catch (RemoteException e) {
+            throw e.rethrowFromSystemServer();
+        }
+    }
     /** @hide exposed via the NetworkProvider class. */
     @RequiresPermission(anyOf = {
             NetworkStack.PERMISSION_MAINLINE_NETWORK_STACK,

framework/src/android/net/IConnectivityManager.aidl

@@ -23,6 +23,7 @@ import android.net.IConnectivityDiagnosticsCallback;
 import android.net.INetworkAgent;
 import android.net.IOnCompleteListener;
 import android.net.INetworkActivityListener;
+import android.net.INetworkOfferCallback;
 import android.net.IQosCallback;
 import android.net.ISocketKeepaliveCallback;
 import android.net.LinkProperties;
@@ -221,4 +222,8 @@ interface IConnectivityManager
             in IOnCompleteListener listener);
 
     int getRestrictBackgroundStatusByCaller();
+
+    void offerNetwork(in Messenger messenger, in NetworkScore score,
+            in NetworkCapabilities caps, in INetworkOfferCallback callback);
+    void unofferNetwork(in INetworkOfferCallback callback);
 }

framework/src/android/net/INetworkOfferCallback.aidl

@@ -0,0 +1,62 @@
+/*
+ * Copyright (C) 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package android.net;
+
+import android.net.NetworkRequest;
+
+/**
+ * A callback registered with connectivity by network providers together with
+ * a NetworkOffer.
+ *
+ * When the offer is needed to satisfy some application or system component,
+ * connectivity will call onOfferNeeded on this callback. When this happens,
+ * the provider should try and bring up the network.
+ *
+ * When the offer is no longer needed, for example because the application has
+ * withdrawn the request or if the request is being satisfied by a network
+ * that this offer will never be able to beat, connectivity calls
+ * onOfferUnneeded. When this happens, the provider should stop trying to
+ * bring up the network, or tear it down if it has already been brought up.
+ *
+ * When NetworkProvider#offerNetwork is called, the provider can expect to
+ * immediately receive all requests that can be fulfilled by that offer and
+ * are not already satisfied by a better network. It is possible no such
+ * request is currently outstanding, because no requests have been made that
+ * can be satisfied by this offer, or because all such requests are already
+ * satisfied by a better network.
+ * onOfferNeeded can be called at any time after registration and until the
+ * offer is withdrawn with NetworkProvider#unofferNetwork is called. This
+ * typically happens when a new network request is filed by an application,
+ * or when the network satisfying a request disconnects and this offer now
+ * stands a chance to be the best network for it.
+ *
+ * @hide
+ */
+oneway interface INetworkOfferCallback {
+    /**
+     * Informs the registrant that the offer is needed to fulfill this request.
+     * @param networkRequest the request to satisfy
+     * @param providerId the ID of the provider currently satisfying
+     *          this request, or NetworkProvider.ID_NONE if none.
+     */
+    void onOfferNeeded(in NetworkRequest networkRequest, int providerId);
+
+    /**
+     * Informs the registrant that the offer is no longer needed to fulfill this request.
+     */
+    void onOfferUnneeded(in NetworkRequest networkRequest);
+}

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);
+    }
 }

services/core/java/com/android/server/ConnectivityService.java

@@ -15,7 +15,6 @@
  */
 
 package com.android.server;
-
 import static android.Manifest.permission.RECEIVE_DATA_ACTIVITY_CHANGE;
 import static android.content.pm.PackageManager.FEATURE_BLUETOOTH;
 import static android.content.pm.PackageManager.FEATURE_WATCH;
@@ -125,6 +124,7 @@ import android.net.INetworkActivityListener;
 import android.net.INetworkAgent;
 import android.net.INetworkMonitor;
 import android.net.INetworkMonitorCallbacks;
+import android.net.INetworkOfferCallback;
 import android.net.IOnCompleteListener;
 import android.net.IQosCallback;
 import android.net.ISocketKeepaliveCallback;
@@ -234,6 +234,7 @@ import com.android.net.module.util.PermissionUtils;
 import com.android.server.connectivity.AutodestructReference;
 import com.android.server.connectivity.DnsManager;
 import com.android.server.connectivity.DnsManager.PrivateDnsValidationUpdate;
+import com.android.server.connectivity.FullScore;
 import com.android.server.connectivity.KeepaliveTracker;
 import com.android.server.connectivity.LingerMonitor;
 import com.android.server.connectivity.MockableSystemProperties;
@@ -241,6 +242,7 @@ import com.android.server.connectivity.NetworkAgentInfo;
 import com.android.server.connectivity.NetworkDiagnostics;
 import com.android.server.connectivity.NetworkNotificationManager;
 import com.android.server.connectivity.NetworkNotificationManager.NotificationType;
+import com.android.server.connectivity.NetworkOffer;
 import com.android.server.connectivity.NetworkRanker;
 import com.android.server.connectivity.PermissionMonitor;
 import com.android.server.connectivity.ProfileNetworkPreferences;
@@ -603,6 +605,18 @@ public class ConnectivityService extends IConnectivityManager.Stub
      */
     private static final int EVENT_UID_BLOCKED_REASON_CHANGED = 51;
 
+    /**
+     * Event to register a new network offer
+     * obj = NetworkOffer
+     */
+    private static final int EVENT_REGISTER_NETWORK_OFFER = 52;
+
+    /**
+     * Event to unregister an existing network offer
+     * obj = INetworkOfferCallback
+     */
+    private static final int EVENT_UNREGISTER_NETWORK_OFFER = 53;
+
     /**
      * Argument for {@link #EVENT_PROVISIONING_NOTIFICATION} to indicate that the notification
      * should be shown.
@@ -4684,6 +4698,18 @@ public class ConnectivityService extends IConnectivityManager.Stub
                     handleUnregisterNetworkProvider((Messenger) msg.obj);
                     break;
                 }
+                case EVENT_REGISTER_NETWORK_OFFER: {
+                    handleRegisterNetworkOffer((NetworkOffer) msg.obj);
+                    break;
+                }
+                case EVENT_UNREGISTER_NETWORK_OFFER: {
+                    final NetworkOfferInfo offer =
+                            findNetworkOfferInfoByCallback((INetworkOfferCallback) msg.obj);
+                    if (null != offer) {
+                        handleUnregisterNetworkOffer(offer);
+                    }
+                    break;
+                }
                 case EVENT_REGISTER_NETWORK_AGENT: {
                     final Pair<NetworkAgentInfo, INetworkMonitor> arg =
                             (Pair<NetworkAgentInfo, INetworkMonitor>) msg.obj;
@@ -6214,12 +6240,37 @@ public class ConnectivityService extends IConnectivityManager.Stub
         mHandler.sendMessage(mHandler.obtainMessage(EVENT_UNREGISTER_NETWORK_PROVIDER, messenger));
     }
 
+    @Override
+    public void offerNetwork(@NonNull final Messenger providerMessenger,
+            @NonNull final NetworkScore score, @NonNull final NetworkCapabilities caps,
+            @NonNull final INetworkOfferCallback callback) {
+        final NetworkOffer offer = new NetworkOffer(
+                FullScore.makeProspectiveScore(score, caps), caps, callback, providerMessenger);
+        mHandler.sendMessage(mHandler.obtainMessage(EVENT_REGISTER_NETWORK_OFFER, offer));
+    }
+
+    @Override
+    public void unofferNetwork(@NonNull final INetworkOfferCallback callback) {
+        mHandler.sendMessage(mHandler.obtainMessage(EVENT_UNREGISTER_NETWORK_OFFER, callback));
+    }
+
     private void handleUnregisterNetworkProvider(Messenger messenger) {
         NetworkProviderInfo npi = mNetworkProviderInfos.remove(messenger);
         if (npi == null) {
             loge("Failed to find Messenger in unregisterNetworkProvider");
             return;
         }
+        // Unregister all the offers from this provider
+        final ArrayList<NetworkOfferInfo> toRemove = new ArrayList<>();
+        for (final NetworkOfferInfo noi : mNetworkOffers) {
+            if (noi.offer.provider == messenger) {
+                // Can't call handleUnregisterNetworkOffer here because iteration is in progress
+                toRemove.add(noi);
+            }
+        }
+        for (NetworkOfferInfo noi : toRemove) {
+            handleUnregisterNetworkOffer(noi);
+        }
         if (DBG) log("unregisterNetworkProvider for " + npi.name);
     }
 
@@ -6258,6 +6309,10 @@ public class ConnectivityService extends IConnectivityManager.Stub
     // (on the handler thread).
     private volatile List<UidRange> mVpnBlockedUidRanges = new ArrayList<>();
 
+    // Must only be accessed on the handler thread
+    @NonNull
+    private final ArrayList<NetworkOfferInfo> mNetworkOffers = new ArrayList<>();
+
     @GuardedBy("mBlockedAppUids")
     private final HashSet<Integer> mBlockedAppUids = new HashSet<>();
 
@@ -6582,6 +6637,65 @@ public class ConnectivityService extends IConnectivityManager.Stub
         updateUids(nai, null, nai.networkCapabilities);
     }
 
+    private class NetworkOfferInfo implements IBinder.DeathRecipient {
+        @NonNull public final NetworkOffer offer;
+
+        NetworkOfferInfo(@NonNull final NetworkOffer offer) {
+            this.offer = offer;
+        }
+
+        @Override
+        public void binderDied() {
+            mHandler.post(() -> handleUnregisterNetworkOffer(this));
+        }
+    }
+
+    /**
+     * Register or update a network offer.
+     * @param newOffer The new offer. If the callback member is the same as an existing
+     *                 offer, it is an update of that offer.
+     */
+    private void handleRegisterNetworkOffer(@NonNull final NetworkOffer newOffer) {
+        ensureRunningOnConnectivityServiceThread();
+        if (null == mNetworkProviderInfos.get(newOffer.provider)) {
+            // This may actually happen if a provider updates its score or registers and then
+            // immediately unregisters. The offer would still be in the handler queue, but the
+            // provider would have been removed.
+            if (DBG) log("Received offer from an unregistered provider");
+            return;
+        }
+
+        final NetworkOfferInfo existingOffer = findNetworkOfferInfoByCallback(newOffer.callback);
+        if (null != existingOffer) {
+            handleUnregisterNetworkOffer(existingOffer);
+            newOffer.migrateFrom(existingOffer.offer);
+        }
+        final NetworkOfferInfo noi = new NetworkOfferInfo(newOffer);
+        try {
+            noi.offer.provider.getBinder().linkToDeath(noi, 0 /* flags */);
+        } catch (RemoteException e) {
+            noi.binderDied();
+            return;
+        }
+        mNetworkOffers.add(noi);
+        // TODO : send requests to the provider.
+    }
+
+    private void handleUnregisterNetworkOffer(@NonNull final NetworkOfferInfo noi) {
+        ensureRunningOnConnectivityServiceThread();
+        mNetworkOffers.remove(noi);
+        noi.offer.provider.getBinder().unlinkToDeath(noi, 0 /* flags */);
+    }
+
+    @Nullable private NetworkOfferInfo findNetworkOfferInfoByCallback(
+            @NonNull final INetworkOfferCallback callback) {
+        ensureRunningOnConnectivityServiceThread();
+        for (final NetworkOfferInfo noi : mNetworkOffers) {
+            if (noi.offer.callback.equals(callback)) return noi;
+        }
+        return null;
+    }
+
     /**
      * Called when receiving LinkProperties directly from a NetworkAgent.
      * Stores into |nai| any data coming from the agent that might also be written to the network's

services/core/java/com/android/server/connectivity/FullScore.java

@@ -16,6 +16,7 @@
 
 package com.android.server.connectivity;
 
+import static android.net.NetworkCapabilities.NET_CAPABILITY_INTERNET;
 import static android.net.NetworkCapabilities.NET_CAPABILITY_VALIDATED;
 import static android.net.NetworkCapabilities.TRANSPORT_VPN;
 
@@ -115,6 +116,33 @@ public class FullScore {
                 config.acceptUnvalidated);
     }
 
+    /**
+     * Given a score supplied by the NetworkAgent, produce a prospective score for an offer.
+     *
+     * NetworkOffers have score filters that are compared to the scores of actual networks
+     * to see if they could possibly beat the current satisfier. Some things the agent can't
+     * know in advance ; a good example is the validation bit – some networks will validate,
+     * others won't. For comparison purposes, assume the best, so all possibly beneficial
+     * networks will be brought up.
+     *
+     * @param score the score supplied by the agent for this offer
+     * @param caps the capabilities supplied by the agent for this offer
+     * @return a FullScore appropriate for comparing to actual network's scores.
+     */
+    public static FullScore makeProspectiveScore(@NonNull final NetworkScore score,
+            @NonNull final NetworkCapabilities caps) {
+        // If the network offers Internet access, it may validate.
+        final boolean mayValidate = caps.hasCapability(NET_CAPABILITY_INTERNET);
+        // VPN transports are known in advance.
+        final boolean vpn = caps.hasTransport(TRANSPORT_VPN);
+        // The network hasn't been chosen by the user (yet, at least).
+        final boolean everUserSelected = false;
+        // Don't assume the user will accept unvalidated connectivity.
+        final boolean acceptUnvalidated = false;
+        return withPolicies(score.getLegacyInt(), mayValidate, vpn, everUserSelected,
+                acceptUnvalidated);
+    }
+
     /**
      * Return a new score given updated caps and config.
      *

services/core/java/com/android/server/connectivity/NetworkOffer.java

@@ -0,0 +1,94 @@
+/*
+ * Copyright (C) 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.server.connectivity;
+
+import android.annotation.NonNull;
+import android.annotation.Nullable;
+import android.net.INetworkOfferCallback;
+import android.net.NetworkCapabilities;
+import android.net.NetworkRequest;
+import android.os.Messenger;
+
+import java.util.Objects;
+
+
+/**
+ * Represents an offer made by a NetworkProvider to create a network if a need arises.
+ *
+ * This class contains the prospective score and capabilities of the network. The provider
+ * is not obligated to caps able to create a network satisfying this, nor to build a network
+ * with the exact score and/or capabilities passed ; after all, not all providers know in
+ * advance what a network will look like after it's connected. Instead, this is meant as a
+ * filter to limit requests sent to the provider by connectivity to those that this offer stands
+ * a chance to fulfill.
+ *
+ * @see NetworkProvider#offerNetwork.
+ *
+ * @hide
+ */
+public class NetworkOffer {
+    @NonNull public final FullScore score;
+    @NonNull public final NetworkCapabilities caps;
+    @NonNull public final INetworkOfferCallback callback;
+    @NonNull public final Messenger provider;
+
+    private static NetworkCapabilities emptyCaps() {
+        final NetworkCapabilities nc = new NetworkCapabilities();
+        return nc;
+    }
+
+    // Ideally the caps argument would be non-null, but null has historically meant no filter
+    // and telephony passes null. Keep backward compatibility.
+    public NetworkOffer(@NonNull final FullScore score,
+            @Nullable final NetworkCapabilities caps,
+            @NonNull final INetworkOfferCallback callback,
+            @NonNull final Messenger provider) {
+        this.score = Objects.requireNonNull(score);
+        this.caps = null != caps ? caps : emptyCaps();
+        this.callback = Objects.requireNonNull(callback);
+        this.provider = Objects.requireNonNull(provider);
+    }
+
+    /**
+     * Migrate from, and take over, a previous offer.
+     *
+     * When an updated offer is sent from a provider, call this method on the new offer, passing
+     * the old one, to take over the state.
+     *
+     * @param previousOffer
+     */
+    public void migrateFrom(@NonNull final NetworkOffer previousOffer) {
+        if (!callback.equals(previousOffer.callback)) {
+            throw new IllegalArgumentException("Can only migrate from a previous version of"
+                    + " the same offer");
+        }
+    }
+
+    /**
+     * Returns whether an offer can satisfy a NetworkRequest, according to its capabilities.
+     * @param request The request to test against.
+     * @return Whether this offer can satisfy the request.
+     */
+    public final boolean canSatisfy(@NonNull final NetworkRequest request) {
+        return request.networkCapabilities.satisfiedByNetworkCapabilities(caps);
+    }
+
+    @Override
+    public String toString() {
+        return "NetworkOffer [ Score " + score + " ]";
+    }
+}