Allow network providers to set the linger duration.

Test: atest CtsNetTestCases:NetworkAgentTest#testSetLingerDuration
CTS-Coverage-Bug: 184796264
Bug: 184227264
Merged-In: I3c2563d4ae4e3715d0c6270344ba8f7ef067872f
Merged-In: I7f420faa40863385114705d6971cf00887d03318
Change-Id: I7f420faa40863385114705d6971cf00887d03318
  (cherry-picked from ag/14100410)
diff --git a/service/src/com/android/server/ConnectivityService.java b/service/src/com/android/server/ConnectivityService.java
index b804a51..eb7dccc 100644
--- a/service/src/com/android/server/ConnectivityService.java
+++ b/service/src/com/android/server/ConnectivityService.java
@@ -1400,8 +1400,8 @@
                 new NetworkInfo(TYPE_NONE, 0, "", ""),
                 new LinkProperties(), new NetworkCapabilities(),
                 new NetworkScore.Builder().setLegacyInt(0).build(), mContext, null,
-                new NetworkAgentConfig(), this, null, null, 0, INVALID_UID, mQosCallbackTracker,
-                mDeps);
+                new NetworkAgentConfig(), this, null, null, 0, INVALID_UID,
+                mLingerDelayMs, mQosCallbackTracker, mDeps);
     }
 
     private static NetworkCapabilities createDefaultNetworkCapabilitiesForUid(int uid) {
@@ -3234,6 +3234,11 @@
                     } else {
                         logwtf(nai.toShortString() + " set invalid teardown delay " + msg.arg1);
                     }
+                    break;
+                }
+                case NetworkAgent.EVENT_LINGER_DURATION_CHANGED: {
+                    nai.setLingerDuration((int) arg.second);
+                    break;
                 }
             }
         }
@@ -6597,7 +6602,8 @@
         final NetworkAgentInfo nai = new NetworkAgentInfo(na,
                 new Network(mNetIdManager.reserveNetId()), new NetworkInfo(networkInfo), lp, nc,
                 currentScore, mContext, mTrackerHandler, new NetworkAgentConfig(networkAgentConfig),
-                this, mNetd, mDnsResolver, providerId, uid, mQosCallbackTracker, mDeps);
+                this, mNetd, mDnsResolver, providerId, uid, mLingerDelayMs,
+                mQosCallbackTracker, mDeps);
 
         // Make sure the LinkProperties and NetworkCapabilities reflect what the agent info says.
         processCapabilitiesFromAgent(nai, nc);
@@ -7841,7 +7847,7 @@
                     log("   accepting network in place of " + previousSatisfier.toShortString());
                 }
                 previousSatisfier.removeRequest(previousRequest.requestId);
-                previousSatisfier.lingerRequest(previousRequest.requestId, now, mLingerDelayMs);
+                previousSatisfier.lingerRequest(previousRequest.requestId, now);
             } else {
                 if (VDBG || DDBG) log("   accepting network in place of null");
             }
diff --git a/service/src/com/android/server/connectivity/NetworkAgentInfo.java b/service/src/com/android/server/connectivity/NetworkAgentInfo.java
index 851096d..18becd4 100644
--- a/service/src/com/android/server/connectivity/NetworkAgentInfo.java
+++ b/service/src/com/android/server/connectivity/NetworkAgentInfo.java
@@ -59,6 +59,7 @@
 import com.android.server.ConnectivityService;
 
 import java.io.PrintWriter;
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
 import java.util.NoSuchElementException;
@@ -281,6 +282,9 @@
      */
     public static final int ARG_AGENT_SUCCESS = 1;
 
+    // How long this network should linger for.
+    private int mLingerDurationMs;
+
     // All inactivity timers for this network, sorted by expiry time. A timer is added whenever
     // a request is moved to a network with a better score, regardless of whether the network is or
     // was lingering or not. An inactivity timer is also added when a network connects
@@ -349,7 +353,8 @@
             @NonNull NetworkScore score, Context context,
             Handler handler, NetworkAgentConfig config, ConnectivityService connService, INetd netd,
             IDnsResolver dnsResolver, int factorySerialNumber, int creatorUid,
-            QosCallbackTracker qosCallbackTracker, ConnectivityService.Dependencies deps) {
+            int lingerDurationMs, QosCallbackTracker qosCallbackTracker,
+            ConnectivityService.Dependencies deps) {
         Objects.requireNonNull(net);
         Objects.requireNonNull(info);
         Objects.requireNonNull(lp);
@@ -370,6 +375,7 @@
         mHandler = handler;
         this.factorySerialNumber = factorySerialNumber;
         this.creatorUid = creatorUid;
+        mLingerDurationMs = lingerDurationMs;
         mQosCallbackTracker = qosCallbackTracker;
     }
 
@@ -685,6 +691,12 @@
             mHandler.obtainMessage(NetworkAgent.EVENT_TEARDOWN_DELAY_CHANGED,
                     teardownDelayMs, 0, new Pair<>(NetworkAgentInfo.this, null)).sendToTarget();
         }
+
+        @Override
+        public void sendLingerDuration(final int durationMs) {
+            mHandler.obtainMessage(NetworkAgent.EVENT_LINGER_DURATION_CHANGED,
+                    new Pair<>(NetworkAgentInfo.this, durationMs)).sendToTarget();
+        }
     }
 
     /**
@@ -974,13 +986,14 @@
 
     /**
      * Sets the specified requestId to linger on this network for the specified time. Called by
-     * ConnectivityService when the request is moved to another network with a higher score, or
+     * ConnectivityService when any request is moved to another network with a higher score, or
      * when a network is newly created.
      *
      * @param requestId The requestId of the request that no longer need to be served by this
      *                  network. Or {@link NetworkRequest.REQUEST_ID_NONE} if this is the
-     *                  {@code LingerTimer} for a newly created network.
+     *                  {@code InactivityTimer} for a newly created network.
      */
+    // TODO: Consider creating a dedicated function for nascent network, e.g. start/stopNascent.
     public void lingerRequest(int requestId, long now, long duration) {
         if (mInactivityTimerForRequest.get(requestId) != null) {
             // Cannot happen. Once a request is lingering on a particular network, we cannot
@@ -996,6 +1009,19 @@
     }
 
     /**
+     * Sets the specified requestId to linger on this network for the timeout set when
+     * initializing or modified by {@link #setLingerDuration(int)}. Called by
+     * ConnectivityService when any request is moved to another network with a higher score.
+     *
+     * @param requestId The requestId of the request that no longer need to be served by this
+     *                  network.
+     * @param now current system timestamp obtained by {@code SystemClock.elapsedRealtime}.
+     */
+    public void lingerRequest(int requestId, long now) {
+        lingerRequest(requestId, now, mLingerDurationMs);
+    }
+
+    /**
      * Cancel lingering. Called by ConnectivityService when a request is added to this network.
      * Returns true if the given requestId was lingering on this network, false otherwise.
      */
@@ -1032,6 +1058,7 @@
         }
 
         if (newExpiry > 0) {
+            // If the newExpiry timestamp is in the past, the wakeup message will fire immediately.
             mInactivityMessage = new WakeupMessage(
                     mContext, mHandler,
                     "NETWORK_LINGER_COMPLETE." + network.getNetId() /* cmdName */,
@@ -1061,8 +1088,33 @@
     }
 
     /**
-     * Return whether the network is just connected and about to be torn down because of not
-     * satisfying any request.
+     * Set the linger duration for this NAI.
+     * @param durationMs The new linger duration, in milliseconds.
+     */
+    public void setLingerDuration(final int durationMs) {
+        final long diff = durationMs - mLingerDurationMs;
+        final ArrayList<InactivityTimer> newTimers = new ArrayList<>();
+        for (final InactivityTimer timer : mInactivityTimers) {
+            if (timer.requestId == NetworkRequest.REQUEST_ID_NONE) {
+                // Don't touch nascent timer, re-add as is.
+                newTimers.add(timer);
+            } else {
+                newTimers.add(new InactivityTimer(timer.requestId, timer.expiryMs + diff));
+            }
+        }
+        mInactivityTimers.clear();
+        mInactivityTimers.addAll(newTimers);
+        updateInactivityTimer();
+        mLingerDurationMs = durationMs;
+    }
+
+    /**
+     * Return whether the network satisfies no request, but is still being kept up
+     * because it has just connected less than
+     * {@code ConnectivityService#DEFAULT_NASCENT_DELAY_MS}ms ago and is thus still considered
+     * nascent. Note that nascent mechanism uses inactivity timer which isn't
+     * associated with a request. Thus, use {@link NetworkRequest#REQUEST_ID_NONE} to identify it.
+     *
      */
     public boolean isNascent() {
         return mInactive && mInactivityTimers.size() == 1