DNS: Per-network-type and Finch-variable timeouts

net/dns/host_resolver_impl.cc

Index: net/dns/host_resolver_impl.cc
diff --git a/net/dns/host_resolver_impl.cc b/net/dns/host_resolver_impl.cc
index bc1617c227e73598daa63a71372020f459e9d0c1..e35e45b6df37325fc61974af0abacd4fc787a570 100644
--- a/net/dns/host_resolver_impl.cc
+++ b/net/dns/host_resolver_impl.cc
@@ -65,6 +65,10 @@ namespace net {
 
 namespace {
 
+// Default delay between calls to the system resolver for the same hostname.
+// (Can be overridden by field trial.)
+const int64_t kDnsDefaultUnresponsiveDelayMs = 6000;
+
 // Limit the size of hostnames that will be resolved to combat issues in
 // some platform's resolvers.
 const size_t kMaxHostLength = 4096;
@@ -487,6 +491,13 @@ class PriorityTracker {
   size_t counts_[NUM_PRIORITIES];
 };
 
+base::TimeDelta GetUnresponsiveDelay(

[Randy Smith (Not in Mondays), 2016/03/16 20:11:07]

Same comment as before (up to you, but simple enough function called from one
place that I think the code's more readable if it's hoisted).  

[Deprecated (see juliatuttle), 2016/03/17 16:29:46]

Done.

+    NetworkChangeNotifier::ConnectionType type) {
+  return GetTimeDeltaForConnectionTypeFromFieldTrialOrDefault(
+      "DnsUnresponsiveDelayMsByConnectionType",
+      base::TimeDelta::FromMilliseconds(kDnsDefaultUnresponsiveDelayMs), type);
+}
+
 }  // namespace
 
 //-----------------------------------------------------------------------------
@@ -1836,7 +1847,8 @@ HostResolverImpl::ProcTaskParams::ProcTaskParams(
     size_t max_retry_attempts)
     : resolver_proc(resolver_proc),
       max_retry_attempts(max_retry_attempts),
-      unresponsive_delay(base::TimeDelta::FromMilliseconds(6000)),
+      unresponsive_delay(
+          base::TimeDelta::FromMilliseconds(kDnsDefaultUnresponsiveDelayMs)),
       retry_factor(2) {
   // Maximum of 4 retry attempts for host resolution.
   static const size_t kDefaultMaxRetryAttempts = 4u;
@@ -1878,12 +1890,15 @@ HostResolverImpl::HostResolverImpl(const Options& options, NetLog* net_log)
   new LoopbackProbeJob(weak_ptr_factory_.GetWeakPtr());
 #endif
   NetworkChangeNotifier::AddIPAddressObserver(this);
+  NetworkChangeNotifier::AddConnectionTypeObserver(this);
   NetworkChangeNotifier::AddDNSObserver(this);
 #if defined(OS_POSIX) && !defined(OS_MACOSX) && !defined(OS_OPENBSD) && \
     !defined(OS_ANDROID)
   EnsureDnsReloaderInit();
 #endif
 
+  OnConnectionTypeChanged(NetworkChangeNotifier::GetConnectionType());
+
   {
     DnsConfig dns_config;
     NetworkChangeNotifier::GetDnsConfig(&dns_config);
@@ -1903,6 +1918,7 @@ HostResolverImpl::~HostResolverImpl() {
   STLDeleteValues(&jobs_);
 
   NetworkChangeNotifier::RemoveIPAddressObserver(this);
+  NetworkChangeNotifier::RemoveConnectionTypeObserver(this);
   NetworkChangeNotifier::RemoveDNSObserver(this);
 }
 
@@ -2341,6 +2357,11 @@ void HostResolverImpl::OnIPAddressChanged() {
   // |this| may be deleted inside AbortAllInProgressJobs().
 }
 
+void HostResolverImpl::OnConnectionTypeChanged(
+    NetworkChangeNotifier::ConnectionType type) {
+  proc_params_.unresponsive_delay = GetUnresponsiveDelay(type);
+}
+
 void HostResolverImpl::OnInitialDNSConfigRead() {
   UpdateDNSConfig(false);
 }