Improve partial connectivity

Improve the design and fix some nits.

Bug: 113450764
Test: 1. Build pass
      2. atest FrameworksNetTests
      3. atest NetworkStackTests
      4. Change captive_portal_https_url to https://invalid.com
      to simulate partial connectivity.
Change-Id: Ia56645841d00d2ed8406cfeacb86a4a27fd58650

diff --git a/src/com/android/server/NetworkStackService.java b/src/com/android/server/NetworkStackService.java
index 72955bb..a8bd0a1 100644
--- a/src/com/android/server/NetworkStackService.java
+++ b/src/com/android/server/NetworkStackService.java

@@ -253,9 +253,9 @@
         }
 
         @Override
-        public void notifyAcceptPartialConnectivity() {
+        public void setAcceptPartialConnectivity() {
             checkNetworkStackCallingPermission();
-            mNm.notifyAcceptPartialConnectivity();
+            mNm.setAcceptPartialConnectivity();
         }
 
         @Override

diff --git a/src/com/android/server/connectivity/NetworkMonitor.java b/src/com/android/server/connectivity/NetworkMonitor.java
index fc56da7..31fa5c5 100644
--- a/src/com/android/server/connectivity/NetworkMonitor.java
+++ b/src/com/android/server/connectivity/NetworkMonitor.java

@@ -319,7 +319,8 @@
     private final DnsStallDetector mDnsStallDetector;
     private long mLastProbeTime;
     // Set to true if data stall is suspected and reset to false after metrics are sent to statsd.
-    private boolean mCollectDataStallMetrics = false;
+    private boolean mCollectDataStallMetrics;
+    private boolean mAcceptPartialConnectivity;
 
     public NetworkMonitor(Context context, INetworkMonitorCallbacks cb, Network network,
             SharedLog validationLog) {
@@ -386,10 +387,11 @@
     }
 
     /**
-     * ConnectivityService notifies NetworkMonitor that the user accepts partial connectivity and
-     * NetworkMonitor should ignore the https probe.
+     * ConnectivityService notifies NetworkMonitor that the user already accepted partial
+     * connectivity previously, so NetworkMonitor can validate the network even if it has partial
+     * connectivity.
      */
-    public void notifyAcceptPartialConnectivity() {
+    public void setAcceptPartialConnectivity() {
         sendMessage(EVENT_ACCEPT_PARTIAL_CONNECTIVITY);
     }
 
@@ -651,9 +653,11 @@
                 case EVENT_DNS_NOTIFICATION:
                     mDnsStallDetector.accumulateConsecutiveDnsTimeoutCount(message.arg1);
                     break;
+                // Set mAcceptPartialConnectivity to true and if network start evaluating or
+                // re-evaluating and get the result of partial connectivity, ProbingState will
+                // disable HTTPS probe and transition to EvaluatingPrivateDnsState.
                 case EVENT_ACCEPT_PARTIAL_CONNECTIVITY:
-                    mUseHttps = false;
-                    transitionTo(mEvaluatingPrivateDnsState);
+                    mAcceptPartialConnectivity = true;
                     break;
                 default:
                     break;
@@ -849,6 +853,14 @@
                     // ignore any re-evaluation requests. After, restart the
                     // evaluation process via EvaluatingState#enter.
                     return (mEvaluateAttempts < IGNORE_REEVALUATE_ATTEMPTS) ? HANDLED : NOT_HANDLED;
+                // Disable HTTPS probe and transition to EvaluatingPrivateDnsState because:
+                // 1. Network is connected and finish the network validation.
+                // 2. NetworkMonitor detects network is partial connectivity and user accepts it.
+                case EVENT_ACCEPT_PARTIAL_CONNECTIVITY:
+                    mAcceptPartialConnectivity = true;
+                    mUseHttps = false;
+                    transitionTo(mEvaluatingPrivateDnsState);
+                    return HANDLED;
                 default:
                     return NOT_HANDLED;
             }
@@ -1081,7 +1093,12 @@
                         logNetworkEvent(NetworkEvent.NETWORK_PARTIAL_CONNECTIVITY);
                         notifyNetworkTested(NETWORK_TEST_RESULT_PARTIAL_CONNECTIVITY,
                                 probeResult.redirectUrl);
-                        transitionTo(mWaitingForNextProbeState);
+                        if (mAcceptPartialConnectivity) {
+                            mUseHttps = false;
+                            transitionTo(mEvaluatingPrivateDnsState);
+                        } else {
+                            transitionTo(mWaitingForNextProbeState);
+                        }
                     } else {
                         logNetworkEvent(NetworkEvent.NETWORK_VALIDATION_FAILED);
                         notifyNetworkTested(NETWORK_TEST_RESULT_INVALID, probeResult.redirectUrl);

diff --git a/tests/src/com/android/server/connectivity/NetworkMonitorTest.java b/tests/src/com/android/server/connectivity/NetworkMonitorTest.java
index d93aef2..d732c4e 100644
--- a/tests/src/com/android/server/connectivity/NetworkMonitorTest.java
+++ b/tests/src/com/android/server/connectivity/NetworkMonitorTest.java

@@ -583,7 +583,7 @@
         verify(mCallbacks, timeout(HANDLER_TIMEOUT_MS).times(1))
                 .notifyNetworkTested(NETWORK_TEST_RESULT_PARTIAL_CONNECTIVITY, null);
 
-        nm.notifyAcceptPartialConnectivity();
+        nm.setAcceptPartialConnectivity();
         verify(mCallbacks, timeout(HANDLER_TIMEOUT_MS).times(1))
                 .notifyNetworkTested(NETWORK_TEST_RESULT_VALID, null);
     }