From 1654b1d11c3f4195d6f691bd1b6eb5aa672ffc94 Mon Sep 17 00:00:00 2001
From: Hugo Benichi <hugobenichi@google.com>
Date: Tue, 24 May 2016 11:50:31 +0900
Subject: [PATCH] Fix default network transition event recording

When disconnecting from a default network X and falling back on another
connected network Y as the new default, ConnectivityService was
attempting to record this event as a X -> Y "atomic" transition.

In practice the default network connectivity is actually lost and
recovering default network takes some non-zero time.

This patch changes the event recording to always record disconnection as
X -> 0 events. At the same time, if there is a fallback network that is
elected as the new default ConnectivityService will also record a 0 -> Y
event.

This patch also improves pretty-printing of DefaultNetworkEvent.

Extract from $ adb shell dumpsys connectivity_metrics_logger --events
17:51:00.086: DefaultNetworkEvent(0 -> 100:CELLULAR)
17:51:25.232: DefaultNetworkEvent(100:IPv4 -> 101:WIFI) # wifi goes on
17:51:44.064: DefaultNetworkEvent(101:DUAL -> 0)        # wifi goes off
17:51:44.187: DefaultNetworkEvent(0 -> 100:CELLULAR)

Bug: 28204408
Change-Id: I63252633235bf6ba833b9ac431a80dda75a93e67
---
 .../net/metrics/DefaultNetworkEvent.java      | 24 +++++++++++++++++--
 .../android/server/ConnectivityService.java   | 16 +++++++------
 2 files changed, 31 insertions(+), 9 deletions(-)

diff --git a/core/java/android/net/metrics/DefaultNetworkEvent.java b/core/java/android/net/metrics/DefaultNetworkEvent.java
index 6138b83fe5b8b..f8b59925cb910 100644
--- a/core/java/android/net/metrics/DefaultNetworkEvent.java
+++ b/core/java/android/net/metrics/DefaultNetworkEvent.java
@@ -68,8 +68,28 @@ public final class DefaultNetworkEvent extends IpConnectivityEvent implements Pa
 
     @Override
     public String toString() {
-      return String.format("DefaultNetworkEvent(%d -> %d, %s, IPv4: %b, IPv6: %b)", prevNetId,
-              netId, NetworkCapabilities.transportNamesOf(transportTypes), prevIPv4, prevIPv6);
+      String prevNetwork = String.valueOf(prevNetId);
+      String newNetwork = String.valueOf(netId);
+      if (prevNetId != 0) {
+          prevNetwork += ":" + ipSupport();
+      }
+      if (netId != 0) {
+          newNetwork += ":" + NetworkCapabilities.transportNamesOf(transportTypes);
+      }
+      return String.format("DefaultNetworkEvent(%s -> %s)", prevNetwork, newNetwork);
+    }
+
+    private String ipSupport() {
+        if (prevIPv4 && prevIPv6) {
+            return "DUAL";
+        }
+        if (prevIPv6) {
+            return "IPv6";
+        }
+        if (prevIPv4) {
+            return "IPv4";
+        }
+        return "NONE";
     }
 
     public static final Parcelable.Creator<DefaultNetworkEvent> CREATOR
diff --git a/services/core/java/com/android/server/ConnectivityService.java b/services/core/java/com/android/server/ConnectivityService.java
index c096fa5f39467..c30e54005e8d3 100644
--- a/services/core/java/com/android/server/ConnectivityService.java
+++ b/services/core/java/com/android/server/ConnectivityService.java
@@ -2245,6 +2245,11 @@ public class ConnectivityService extends IConnectivityManager.Stub
             final boolean wasDefault = isDefaultNetwork(nai);
             if (wasDefault) {
                 mDefaultInetConditionPublished = 0;
+                // Log default network disconnection before required book-keeping.
+                // Let rematchAllNetworksAndRequests() below record a new default network event
+                // if there is a fallback. Taken together, the two form a X -> 0, 0 -> Y sequence
+                // whose timestamps tell how long it takes to recover a default network.
+                logDefaultNetworkEvent(null, nai);
             }
             notifyIfacesChangedForNetworkStats();
             // TODO - we shouldn't send CALLBACK_LOST to requests that can be satisfied
@@ -2278,10 +2283,6 @@ public class ConnectivityService extends IConnectivityManager.Stub
             }
             mLegacyTypeTracker.remove(nai, wasDefault);
             rematchAllNetworksAndRequests(null, 0);
-            if (wasDefault && getDefaultNetwork() == null) {
-                // Log that we lost the default network and there is no replacement.
-                logDefaultNetworkEvent(null, nai);
-            }
             if (nai.created) {
                 // Tell netd to clean up the configuration for this network
                 // (routing rules, DNS, etc).
@@ -4583,7 +4584,7 @@ public class ConnectivityService extends IConnectivityManager.Stub
         teardownUnneededNetwork(oldNetwork);
     }
 
-    private void makeDefault(NetworkAgentInfo newNetwork, NetworkAgentInfo prevNetwork) {
+    private void makeDefault(NetworkAgentInfo newNetwork) {
         if (DBG) log("Switching to new default network: " + newNetwork);
         setupDataActivityTracking(newNetwork);
         try {
@@ -4595,7 +4596,6 @@ public class ConnectivityService extends IConnectivityManager.Stub
         handleApplyDefaultProxy(newNetwork.linkProperties.getHttpProxy());
         updateTcpBufferSizes(newNetwork);
         setDefaultDnsSystemProperties(newNetwork.linkProperties.getDnsServers());
-        logDefaultNetworkEvent(newNetwork, prevNetwork);
     }
 
     // Handles a network appearing or improving its score.
@@ -4746,7 +4746,9 @@ public class ConnectivityService extends IConnectivityManager.Stub
         }
         if (isNewDefault) {
             // Notify system services that this network is up.
-            makeDefault(newNetwork, oldDefaultNetwork);
+            makeDefault(newNetwork);
+            // Log 0 -> X and Y -> X default network transitions, where X is the new default.
+            logDefaultNetworkEvent(newNetwork, oldDefaultNetwork);
             synchronized (ConnectivityService.this) {
                 // have a new default network, release the transition wakelock in
                 // a second if it's held.  The second pause is to allow apps