[NS05] Feed network offer callbacks

The design is very simply expressed :
An offer is needed for a request if and only if that offer
might beat the satisfier for that request.

The implementation of "might beat" is NetworkRanker#mightBeat.

Test: FrameworksNetTests FrameworksWifiTests NetworkStackTests
Bug: 167544279
Merged-In: I3c2563d4ae4e3715d0c6270344ba8f7ef067872f
Merged-In: I0fe911eef2483ecbac48c733d56283b81538690a
Change-Id: I0fe911eef2483ecbac48c733d56283b81538690a
  (cherry-picked from 7b6a33bd504e88ac051db9511eafe915d80e7539)
diff --git a/service/src/com/android/server/ConnectivityService.java b/service/src/com/android/server/ConnectivityService.java
index 3771bbc..f7d8aa0 100644
--- a/service/src/com/android/server/ConnectivityService.java
+++ b/service/src/com/android/server/ConnectivityService.java
@@ -3359,8 +3359,6 @@
                 nai.lastValidated = valid;
                 nai.everValidated |= valid;
                 updateCapabilities(oldScore, nai, nai.networkCapabilities);
-                // If score has changed, rebroadcast to NetworkProviders. b/17726566
-                if (oldScore != nai.getCurrentScore()) sendUpdatedScoreToFactories(nai);
                 if (valid) {
                     handleFreshlyValidatedNetwork(nai);
                     // Clear NO_INTERNET, PRIVATE_DNS_BROKEN, PARTIAL_CONNECTIVITY and
@@ -3781,9 +3779,12 @@
             if (currentNetwork != null
                     && currentNetwork.network.getNetId() == nai.network.getNetId()) {
                 // uid rules for this network will be removed in destroyNativeNetwork(nai).
+                // TODO : setting the satisfier is in fact the job of the rematch. Teach the
+                // rematch not to keep disconnected agents instead of setting it here ; this
+                // will also allow removing updating the offers below.
                 nri.setSatisfier(null, null);
-                if (request.isRequest()) {
-                    sendUpdatedScoreToFactories(request, null);
+                for (final NetworkOfferInfo noi : mNetworkOffers) {
+                    informOffer(nri, noi.offer, mNetworkRanker);
                 }
 
                 if (mDefaultRequest == nri) {
@@ -3939,16 +3940,13 @@
         }
 
         rematchAllNetworksAndRequests();
-        for (final NetworkRequestInfo nri : nris) {
-            // If the nri is satisfied, return as its score has already been sent if needed.
-            if (nri.isBeingSatisfied()) {
-                return;
-            }
 
-            // As this request was not satisfied on rematch and thus never had any scores sent to
-            // the factories, send null now for each request of type REQUEST.
-            for (final NetworkRequest req : nri.mRequests) {
-                if (req.isRequest()) sendUpdatedScoreToFactories(req, null);
+        // Requests that have not been matched to a network will not have been sent to the
+        // providers, because the old satisfier and the new satisfier are the same (null in this
+        // case). Send these requests to the providers.
+        for (final NetworkRequestInfo nri : nris) {
+            for (final NetworkOfferInfo noi : mNetworkOffers) {
+                informOffer(nri, noi.offer, mNetworkRanker);
             }
         }
     }
@@ -4156,7 +4154,15 @@
             }
         }
 
-        cancelNpiRequests(nri);
+        // For all outstanding offers, cancel any of the layers of this NRI that used to be
+        // needed for this offer.
+        for (final NetworkOfferInfo noi : mNetworkOffers) {
+            for (final NetworkRequest req : nri.mRequests) {
+                if (req.isRequest() && noi.offer.neededFor(req)) {
+                    noi.offer.onNetworkUnneeded(req);
+                }
+            }
+        }
     }
 
     private void handleRemoveNetworkRequests(@NonNull final Set<NetworkRequestInfo> nris) {
@@ -4169,20 +4175,6 @@
         }
     }
 
-    private void cancelNpiRequests(@NonNull final NetworkRequestInfo nri) {
-        for (final NetworkRequest req : nri.mRequests) {
-            cancelNpiRequest(req);
-        }
-    }
-
-    private void cancelNpiRequest(@NonNull final NetworkRequest req) {
-        if (req.isRequest()) {
-            for (final NetworkProviderInfo npi : mNetworkProviderInfos.values()) {
-                npi.cancelRequest(req);
-            }
-        }
-    }
-
     private void removeListenRequestFromNetworks(@NonNull final NetworkRequest req) {
         // listens don't have a singular affected Network. Check all networks to see
         // if this listen request applies and remove it.
@@ -4309,7 +4301,6 @@
             nai.networkAgentConfig.acceptPartialConnectivity = accept;
             nai.updateScoreForNetworkAgentConfigUpdate();
             rematchAllNetworksAndRequests();
-            sendUpdatedScoreToFactories(nai);
         }
 
         if (always) {
@@ -4377,7 +4368,6 @@
         if (!nai.avoidUnvalidated) {
             nai.avoidUnvalidated = true;
             rematchAllNetworksAndRequests();
-            sendUpdatedScoreToFactories(nai);
         }
     }
 
@@ -4482,14 +4472,9 @@
         return avoidBadWifi();
     }
 
-
+    // TODO : this function is now useless.
     private void rematchForAvoidBadWifiUpdate() {
         rematchAllNetworksAndRequests();
-        for (NetworkAgentInfo nai: mNetworkAgentInfos) {
-            if (nai.networkCapabilities.hasTransport(NetworkCapabilities.TRANSPORT_WIFI)) {
-                sendUpdatedScoreToFactories(nai);
-            }
-        }
     }
 
     // TODO: Evaluate whether this is of interest to other consumers of
@@ -5514,24 +5499,6 @@
             }
         }
 
-        void sendMessageToNetworkProvider(int what, int arg1, int arg2, Object obj) {
-            try {
-                messenger.send(Message.obtain(null /* handler */, what, arg1, arg2, obj));
-            } catch (RemoteException e) {
-                // Remote process died. Ignore; the death recipient will remove this
-                // NetworkProviderInfo from mNetworkProviderInfos.
-            }
-        }
-
-        void requestNetwork(NetworkRequest request, int score, int servingProviderId) {
-            sendMessageToNetworkProvider(NetworkProvider.CMD_REQUEST_NETWORK, score,
-                            servingProviderId, request);
-        }
-
-        void cancelRequest(NetworkRequest request) {
-            sendMessageToNetworkProvider(NetworkProvider.CMD_CANCEL_REQUEST, 0, 0, request);
-        }
-
         void connect(Context context, Handler handler) {
             try {
                 messenger.getBinder().linkToDeath(mDeathRecipient, 0);
@@ -6240,7 +6207,6 @@
         if (DBG) log("Got NetworkProvider Messenger for " + npi.name);
         mNetworkProviderInfos.put(npi.messenger, npi);
         npi.connect(mContext, mTrackerHandler);
-        sendAllRequestsToProvider(npi);
     }
 
     @Override
@@ -6263,6 +6229,9 @@
     public void offerNetwork(final int providerId,
             @NonNull final NetworkScore score, @NonNull final NetworkCapabilities caps,
             @NonNull final INetworkOfferCallback callback) {
+        Objects.requireNonNull(score);
+        Objects.requireNonNull(caps);
+        Objects.requireNonNull(callback);
         final NetworkOffer offer = new NetworkOffer(
                 FullScore.makeProspectiveScore(score, caps), caps, callback, providerId);
         mHandler.sendMessage(mHandler.obtainMessage(EVENT_REGISTER_NETWORK_OFFER, offer));
@@ -6287,7 +6256,7 @@
                 toRemove.add(noi);
             }
         }
-        for (NetworkOfferInfo noi : toRemove) {
+        for (final NetworkOfferInfo noi : toRemove) {
             handleUnregisterNetworkOffer(noi);
         }
         if (DBG) log("unregisterNetworkProvider for " + npi.name);
@@ -6707,7 +6676,7 @@
             return;
         }
         mNetworkOffers.add(noi);
-        // TODO : send requests to the provider.
+        issueNetworkNeeds(noi);
     }
 
     private void handleUnregisterNetworkOffer(@NonNull final NetworkOfferInfo noi) {
@@ -7482,100 +7451,6 @@
         updateLinkProperties(nai, newLp, new LinkProperties(nai.linkProperties));
     }
 
-    private void sendUpdatedScoreToFactories(NetworkAgentInfo nai) {
-        for (int i = 0; i < nai.numNetworkRequests(); i++) {
-            NetworkRequest nr = nai.requestAt(i);
-            // Don't send listening or track default request to factories. b/17393458
-            if (!nr.isRequest()) continue;
-            sendUpdatedScoreToFactories(nr, nai);
-        }
-    }
-
-    private void sendUpdatedScoreToFactories(
-            @NonNull final NetworkReassignment.RequestReassignment event) {
-        // If a request of type REQUEST is now being satisfied by a new network.
-        if (null != event.mNewNetworkRequest && event.mNewNetworkRequest.isRequest()) {
-            sendUpdatedScoreToFactories(event.mNewNetworkRequest, event.mNewNetwork);
-        }
-
-        // If a previously satisfied request of type REQUEST is no longer being satisfied.
-        if (null != event.mOldNetworkRequest && event.mOldNetworkRequest.isRequest()
-                && event.mOldNetworkRequest != event.mNewNetworkRequest) {
-            sendUpdatedScoreToFactories(event.mOldNetworkRequest, null);
-        }
-
-        cancelMultilayerLowerPriorityNpiRequests(event.mNetworkRequestInfo);
-    }
-
-    /**
-     *  Cancel with all NPIs the given NRI's multilayer requests that are a lower priority than
-     *  its currently satisfied active request.
-     * @param nri the NRI to cancel lower priority requests for.
-     */
-    private void cancelMultilayerLowerPriorityNpiRequests(
-            @NonNull final NetworkRequestInfo nri) {
-        if (!nri.isMultilayerRequest() || null == nri.mActiveRequest) {
-            return;
-        }
-
-        final int indexOfNewRequest = nri.mRequests.indexOf(nri.mActiveRequest);
-        for (int i = indexOfNewRequest + 1; i < nri.mRequests.size(); i++) {
-            cancelNpiRequest(nri.mRequests.get(i));
-        }
-    }
-
-    private void sendUpdatedScoreToFactories(@NonNull NetworkRequest networkRequest,
-            @Nullable NetworkAgentInfo nai) {
-        final int score;
-        final int serial;
-        if (nai != null) {
-            score = nai.getCurrentScore();
-            serial = nai.factorySerialNumber;
-        } else {
-            score = 0;
-            serial = 0;
-        }
-        if (VDBG || DDBG){
-            log("sending new Min Network Score(" + score + "): " + networkRequest.toString());
-        }
-        for (NetworkProviderInfo npi : mNetworkProviderInfos.values()) {
-            npi.requestNetwork(networkRequest, score, serial);
-        }
-    }
-
-    /** Sends all current NetworkRequests to the specified factory. */
-    private void sendAllRequestsToProvider(@NonNull final NetworkProviderInfo npi) {
-        ensureRunningOnConnectivityServiceThread();
-        for (final NetworkRequestInfo nri : getNrisFromGlobalRequests()) {
-            for (final NetworkRequest req : nri.mRequests) {
-                if (!req.isRequest() && nri.getActiveRequest() == req) {
-                    break;
-                }
-                if (!req.isRequest()) {
-                    continue;
-                }
-                // Only set the nai for the request it is satisfying.
-                final NetworkAgentInfo nai =
-                        nri.getActiveRequest() == req ? nri.getSatisfier() : null;
-                final int score;
-                final int serial;
-                if (null != nai) {
-                    score = nai.getCurrentScore();
-                    serial = nai.factorySerialNumber;
-                } else {
-                    score = 0;
-                    serial = NetworkProvider.ID_NONE;
-                }
-                npi.requestNetwork(req, score, serial);
-                // For multilayer requests, don't send lower priority requests if a higher priority
-                // request is already satisfied.
-                if (null != nai) {
-                    break;
-                }
-            }
-        }
-    }
-
     private void sendPendingIntentForRequest(NetworkRequestInfo nri, NetworkAgentInfo networkAgent,
             int notificationType) {
         if (notificationType == ConnectivityManager.CALLBACK_AVAILABLE && !nri.mPendingIntentSent) {
@@ -8067,6 +7942,7 @@
             log(changes.toString()); // Shorter form, only one line of log
         }
         applyNetworkReassignment(changes, now);
+        issueNetworkNeeds();
     }
 
     private void applyNetworkReassignment(@NonNull final NetworkReassignment changes,
@@ -8098,12 +7974,6 @@
         // before LegacyTypeTracker sends legacy broadcasts
         for (final NetworkReassignment.RequestReassignment event :
                 changes.getRequestReassignments()) {
-            // Tell NetworkProviders about the new score, so they can stop
-            // trying to connect if they know they cannot match it.
-            // TODO - this could get expensive if there are a lot of outstanding requests for this
-            // network. Think of a way to reduce this. Push netid->request mapping to each factory?
-            sendUpdatedScoreToFactories(event);
-
             if (null != event.mNewNetwork) {
                 notifyNetworkAvailable(event.mNewNetwork, event.mNetworkRequestInfo);
             } else {
@@ -8240,6 +8110,107 @@
         }
     }
 
+    private void issueNetworkNeeds() {
+        ensureRunningOnConnectivityServiceThread();
+        for (final NetworkOfferInfo noi : mNetworkOffers) {
+            issueNetworkNeeds(noi);
+        }
+    }
+
+    private void issueNetworkNeeds(@NonNull final NetworkOfferInfo noi) {
+        ensureRunningOnConnectivityServiceThread();
+        for (final NetworkRequestInfo nri : mNetworkRequests.values()) {
+            informOffer(nri, noi.offer, mNetworkRanker);
+        }
+    }
+
+    /**
+     * Inform a NetworkOffer about any new situation of a request.
+     *
+     * This function handles updates to offers. A number of events may happen that require
+     * updating the registrant for this offer about the situation :
+     * • The offer itself was updated. This may lead the offer to no longer being able
+     *     to satisfy a request or beat a satisfier (and therefore be no longer needed),
+     *     or conversely being strengthened enough to beat the satisfier (and therefore
+     *     start being needed)
+     * • The network satisfying a request changed (including cases where the request
+     *     starts or stops being satisfied). The new network may be a stronger or weaker
+     *     match than the old one, possibly affecting whether the offer is needed.
+     * • The network satisfying a request updated their score. This may lead the offer
+     *     to no longer be able to beat it if the current satisfier got better, or
+     *     conversely start being a good choice if the current satisfier got weaker.
+     *
+     * @param nri The request
+     * @param offer The offer. This may be an updated offer.
+     */
+    private static void informOffer(@NonNull NetworkRequestInfo nri,
+            @NonNull final NetworkOffer offer, @NonNull final NetworkRanker networkRanker) {
+        final NetworkRequest activeRequest = nri.isBeingSatisfied() ? nri.getActiveRequest() : null;
+        final NetworkAgentInfo satisfier = null != activeRequest ? nri.getSatisfier() : null;
+        final FullScore satisfierScore = null != satisfier ? satisfier.getScore() : null;
+
+        // Multi-layer requests have a currently active request, the one being satisfied.
+        // Since the system will try to bring up a better network than is currently satisfying
+        // the request, NetworkProviders need to be told the offers matching the requests *above*
+        // the currently satisfied one are needed, that the ones *below* the satisfied one are
+        // not needed, and the offer is needed for the active request iff the offer can beat
+        // the satisfier.
+        // For non-multilayer requests, the logic above gracefully degenerates to only the
+        // last case.
+        // To achieve this, the loop below will proceed in three steps. In a first phase, inform
+        // providers that the offer is needed for this request, until the active request is found.
+        // In a second phase, deal with the currently active request. In a third phase, inform
+        // the providers that offer is unneeded for the remaining requests.
+
+        // First phase : inform providers of all requests above the active request.
+        int i;
+        for (i = 0; nri.mRequests.size() > i; ++i) {
+            final NetworkRequest request = nri.mRequests.get(i);
+            if (activeRequest == request) break; // Found the active request : go to phase 2
+            if (!request.isRequest()) continue; // Listens/track defaults are never sent to offers
+            // Since this request is higher-priority than the one currently satisfied, if the
+            // offer can satisfy it, the provider should try and bring up the network for sure ;
+            // no need to even ask the ranker – an offer that can satisfy is always better than
+            // no network. Hence tell the provider so unless it already knew.
+            if (request.canBeSatisfiedBy(offer.caps) && !offer.neededFor(request)) {
+                offer.onNetworkNeeded(request);
+            }
+        }
+
+        // Second phase : deal with the active request (if any)
+        if (null != activeRequest && activeRequest.isRequest()) {
+            final boolean oldNeeded = offer.neededFor(activeRequest);
+            // An offer is needed if it is currently served by this provider or if this offer
+            // can beat the current satisfier.
+            final boolean currentlyServing = satisfier != null
+                    && satisfier.factorySerialNumber == offer.providerId;
+            final boolean newNeeded = (currentlyServing
+                    || (activeRequest.canBeSatisfiedBy(offer.caps)
+                            && networkRanker.mightBeat(activeRequest, satisfierScore, offer)));
+            if (newNeeded != oldNeeded) {
+                if (newNeeded) {
+                    offer.onNetworkNeeded(activeRequest);
+                } else {
+                    // The offer used to be able to beat the satisfier. Now it can't.
+                    offer.onNetworkUnneeded(activeRequest);
+                }
+            }
+        }
+
+        // Third phase : inform the providers that the offer isn't needed for any request
+        // below the active one.
+        for (++i /* skip the active request */; nri.mRequests.size() > i; ++i) {
+            final NetworkRequest request = nri.mRequests.get(i);
+            if (!request.isRequest()) continue; // Listens/track defaults are never sent to offers
+            // Since this request is lower-priority than the one currently satisfied, if the
+            // offer can satisfy it, the provider should not try and bring up the network.
+            // Hence tell the provider so unless it already knew.
+            if (offer.neededFor(request)) {
+                offer.onNetworkUnneeded(request);
+            }
+        }
+    }
+
     private void addNetworkToLegacyTypeTracker(@NonNull final NetworkAgentInfo nai) {
         for (int i = 0; i < nai.numNetworkRequests(); i++) {
             NetworkRequest nr = nai.requestAt(i);
@@ -8405,7 +8376,6 @@
         if (VDBG || DDBG) log("updateNetworkScore for " + nai.toShortString() + " to " + score);
         nai.setScore(score);
         rematchAllNetworksAndRequests();
-        sendUpdatedScoreToFactories(nai);
     }
 
     // Notify only this one new request of the current state. Transfer all the