Revert 39998 - Revert 39996 Refine IPv6 probe to require that the client has...

net/base/host_resolver_impl.cc

Index: net/base/host_resolver_impl.cc
===================================================================
--- net/base/host_resolver_impl.cc	(revision 40097)
+++ net/base/host_resolver_impl.cc	(working copy)
@@ -20,6 +20,7 @@
 #include "net/base/host_resolver_proc.h"
 #include "net/base/load_log.h"
 #include "net/base/net_errors.h"
+#include "net/base/net_util.h"
 #include "net/base/network_change_notifier.h"
 
 #if defined(OS_WIN)
@@ -575,7 +576,8 @@
       resolver_proc_(resolver_proc),
       default_address_family_(ADDRESS_FAMILY_UNSPECIFIED),
       shutdown_(false),
-      network_change_notifier_(network_change_notifier) {
+      network_change_notifier_(network_change_notifier),
+      ipv6_probe_monitoring_(false) {
   DCHECK_GT(max_jobs, 0u);
 
   // It is cumbersome to expose all of the constraints in the constructor,
@@ -736,6 +738,17 @@
   observers_.erase(it);
 }
 
+void HostResolverImpl::SetDefaultAddressFamily(AddressFamily address_family) {
+  ipv6_probe_monitoring_ = false;
+  default_address_family_ = address_family;
+}
+
+void HostResolverImpl::ProbeIPv6Support() {
+  DCHECK(!ipv6_probe_monitoring_);
+  ipv6_probe_monitoring_ = true;
+  OnIPAddressChanged();  // Give initial setup call.
+}
+
 void HostResolverImpl::Shutdown() {
   shutdown_ = true;
 
@@ -977,6 +990,14 @@
 void HostResolverImpl::OnIPAddressChanged() {
   if (cache_.get())
     cache_->clear();
+  if (ipv6_probe_monitoring_) {
+    bool support = IPv6Supported();
+    default_address_family_ = support ? ADDRESS_FAMILY_UNSPECIFIED
+                                      : ADDRESS_FAMILY_IPV4;
+    LOG(INFO) << "IPv6Probe forced AddressFamily setting to "
+              << (support ? "ADDRESS_FAMILY_UNSPECIFIED"
+                          : "ADDRESS_FAMILY_IPV4");
+  }
 }
 
 // static