Avoid initial NetworkChangeNotifier OnDNSChanged() signal on Android

When the DnsConfigServicePosix finishes its initial reading of the
system DNS config, it normally triggers a NetworkChangeNotifier (NCN)
OnDNSChanged() signal.  This can cause in-flight network requests to
abort with ERR_NETWORK_CHANGED.  Avoid aborting requests by:
1. Adding a new NCN signal, OnInitialDNSConfigRead which indicates
   the initial DNS config reading completed but does not represent
   a change in DNS config.
2. Modify HostResolverImpl to not abort requests upon this new
   signal (like it does for the OnDNSChanged signal).
3. Add logic to NetworkChangeNotifierAndroid to emit this new
   signal when safe to do so.  Network requests begin being issued
   immediately after the NCN (and hence DnsConfigService) is
   initialized, so we need to be sure no network change signals
   are missed between NCN initialization completing and the
   OnInitialDNSConfigRead signal.  This is tricky because the
   NCN (and hence DnsConfigService) is initialized on threads
   where file I/O is not allowed.  Were file I/O allowed we could
   simply slurp up the DNS config and hosts file.  Instead we
   start listening for network changes (which is our trigger signal
   for DNS changes on Android) on the initialization thread and
   record the current time to later compare against the hosts
   file's last-modified time to check for changes to the file.
   Actual loading of the DNS config and hosts file is done on
   another thread that allows file I/O.

BUG=470897

Review URL: https://codereview.chromium.org/1047103002

Cr-Commit-Position: refs/heads/master@{#325560}

1 files changed, 51 insertions, 13 deletions

diff --git a/net/android/network_change_notifier_android_unittest.cc b/net/android/network_change_notifier_android_unittest.cc
index 83dd70e..30ee4f0 100644
--- a/net/android/network_change_notifier_android_unittest.cc
+++ b/net/android/network_change_notifier_android_unittest.cc
@@ -12,6 +12,8 @@
 #include "net/android/network_change_notifier_android.h"
 #include "net/android/network_change_notifier_delegate_android.h"
 #include "net/base/network_change_notifier.h"
+#include "net/dns/dns_config_service.h"
+#include "net/dns/dns_protocol.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace net {
@@ -60,6 +62,30 @@ class NetworkChangeNotifierObserver
   int notifications_count_;
 };
 
+class DNSChangeObserver : public NetworkChangeNotifier::DNSObserver {
+ public:
+  DNSChangeObserver()
+      : change_notifications_count_(0), initial_notifications_count_(0) {}
+
+  // NetworkChangeNotifier::DNSObserver:
+  void OnDNSChanged() override { change_notifications_count_++; }
+
+  void OnInitialDNSConfigRead() override {
+    initial_notifications_count_++;
+    base::MessageLoop::current()->Quit();
+  }
+
+  int change_notifications_count() const { return change_notifications_count_; }
+
+  int initial_notifications_count() const {
+    return initial_notifications_count_;
+  }
+
+ private:
+  int change_notifications_count_;
+  int initial_notifications_count_;
+};
+
 }  // namespace
 
 class BaseNetworkChangeNotifierAndroidTest : public testing::Test {
@@ -175,7 +201,12 @@ TEST_F(NetworkChangeNotifierDelegateAndroidTest, DelegateObserverNotified) {
 class NetworkChangeNotifierAndroidTest
     : public BaseNetworkChangeNotifierAndroidTest {
  protected:
-  NetworkChangeNotifierAndroidTest() : notifier_(&delegate_) {
+  void SetUp() override {
+    IPAddressNumber dns_number;
+    ASSERT_TRUE(ParseIPLiteralToNumber("8.8.8.8", &dns_number));
+    dns_config_.nameservers.push_back(
+        IPEndPoint(dns_number, dns_protocol::kDefaultPort));
+    notifier_.reset(new NetworkChangeNotifierAndroid(&delegate_, &dns_config_));
     NetworkChangeNotifier::AddConnectionTypeObserver(
         &connection_type_observer_);
     NetworkChangeNotifier::AddConnectionTypeObserver(
@@ -185,7 +216,8 @@ class NetworkChangeNotifierAndroidTest
   NetworkChangeNotifierObserver connection_type_observer_;
   NetworkChangeNotifierObserver other_connection_type_observer_;
   NetworkChangeNotifier::DisableForTest disable_for_test_;
-  NetworkChangeNotifierAndroid notifier_;
+  DnsConfig dns_config_;
+  scoped_ptr<NetworkChangeNotifierAndroid> notifier_;
 };
 
 // When a NetworkChangeNotifierAndroid is observing a
@@ -194,13 +226,10 @@ class NetworkChangeNotifierAndroidTest
 // NetworkChangeNotifierAndroid should reflect that state.
 TEST_F(NetworkChangeNotifierAndroidTest,
        NotificationsSentToNetworkChangeNotifierAndroid) {
-  RunTest(
-      base::Bind(
-          &NetworkChangeNotifierObserver::notifications_count,
-          base::Unretained(&connection_type_observer_)),
-      base::Bind(
-          &NetworkChangeNotifierAndroid::GetCurrentConnectionType,
-          base::Unretained(&notifier_)));
+  RunTest(base::Bind(&NetworkChangeNotifierObserver::notifications_count,
+                     base::Unretained(&connection_type_observer_)),
+          base::Bind(&NetworkChangeNotifierAndroid::GetCurrentConnectionType,
+                     base::Unretained(notifier_.get())));
 }
 
 // When a NetworkChangeNotifierAndroid's connection state changes, it should
@@ -220,13 +249,13 @@ TEST_F(NetworkChangeNotifierAndroidTest,
 TEST_F(NetworkChangeNotifierAndroidTest, MaxBandwidth) {
   SetOnline();
   EXPECT_EQ(NetworkChangeNotifier::CONNECTION_UNKNOWN,
-            notifier_.GetConnectionType());
+            notifier_->GetConnectionType());
   EXPECT_EQ(std::numeric_limits<double>::infinity(),
-            notifier_.GetMaxBandwidth());
+            notifier_->GetMaxBandwidth());
   SetOffline();
   EXPECT_EQ(NetworkChangeNotifier::CONNECTION_NONE,
-            notifier_.GetConnectionType());
-  EXPECT_EQ(0.0, notifier_.GetMaxBandwidth());
+            notifier_->GetConnectionType());
+  EXPECT_EQ(0.0, notifier_->GetMaxBandwidth());
 }
 
 TEST_F(NetworkChangeNotifierDelegateAndroidTest,
@@ -240,4 +269,13 @@ TEST_F(NetworkChangeNotifierDelegateAndroidTest,
   EXPECT_EQ(2, delegate_observer_.bandwidth_notifications_count());
 }
 
+TEST_F(NetworkChangeNotifierAndroidTest, InitialSignal) {
+  DNSChangeObserver dns_change_observer;
+  NetworkChangeNotifier::AddDNSObserver(&dns_change_observer);
+  base::MessageLoop::current()->Run();
+  EXPECT_EQ(1, dns_change_observer.initial_notifications_count());
+  EXPECT_EQ(0, dns_change_observer.change_notifications_count());
+  NetworkChangeNotifier::RemoveDNSObserver(&dns_change_observer);
+}
+
 }  // namespace net