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

net/dns/host_resolver_impl.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/dns/host_resolver_impl.h"
 
 #include <utility>
 
 #if defined(OS_WIN)
 #include <Winsock2.h>
@@ skipping 47 matching lines @@
 #include "url/url_canon_ip.h"
 
 #if defined(OS_WIN)
 #include "net/base/winsock_init.h"
 #endif
 
 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;
 
 // Default TTL for successful resolutions with ProcTask.
 const unsigned kCacheEntryTTLSeconds = 60;
 
 // Default TTL for unsuccessful resolutions with ProcTask.
 const unsigned kNegativeCacheEntryTTLSeconds = 0;
 
@@ skipping 402 matching lines @@
     if (total_count_ == 0)
       DCHECK_EQ(MINIMUM_PRIORITY, highest_priority_);
   }
 
  private:
   RequestPriority highest_priority_;
   size_t total_count_;
   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
 
 //-----------------------------------------------------------------------------
 
 bool ResolveLocalHostname(base::StringPiece host,
                           uint16_t port,
                           AddressList* address_list) {
   address_list->clear();
 
   bool is_local6;
@@ skipping 1329 matching lines @@
   PrioritizedDispatcher::Handle handle_;
 };
 
 //-----------------------------------------------------------------------------
 
 HostResolverImpl::ProcTaskParams::ProcTaskParams(
     HostResolverProc* resolver_proc,
     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;
   if (max_retry_attempts == HostResolver::kDefaultRetryAttempts)
     max_retry_attempts = kDefaultMaxRetryAttempts;
 }
 
 HostResolverImpl::ProcTaskParams::ProcTaskParams(const ProcTaskParams& other) =
     default;
 
@@ skipping 21 matching lines @@
 
   DCHECK_GE(dispatcher_->num_priorities(), static_cast<size_t>(NUM_PRIORITIES));
 
 #if defined(OS_WIN)
   EnsureWinsockInit();
 #endif
 #if defined(OS_POSIX) && !defined(OS_MACOSX) && !defined(OS_ANDROID)
   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);
     received_dns_config_ = dns_config.IsValid();
     // Conservatively assume local IPv6 is needed when DnsConfig is not valid.
     use_local_ipv6_ = !dns_config.IsValid() || dns_config.use_local_ipv6;
   }
 
   fallback_to_proctask_ = !ConfigureAsyncDnsNoFallbackFieldTrial();
 }
 
 HostResolverImpl::~HostResolverImpl() {
   // Prevent the dispatcher from starting new jobs.
   dispatcher_->SetLimitsToZero();
   // It's now safe for Jobs to call KillDsnTask on destruction, because
   // OnJobComplete will not start any new jobs.
   STLDeleteValues(&jobs_);
 
   NetworkChangeNotifier::RemoveIPAddressObserver(this);
+  NetworkChangeNotifier::RemoveConnectionTypeObserver(this);
   NetworkChangeNotifier::RemoveDNSObserver(this);
 }
 
 void HostResolverImpl::SetMaxQueuedJobs(size_t value) {
   DCHECK_EQ(0u, dispatcher_->num_queued_jobs());
   DCHECK_GT(value, 0u);
   max_queued_jobs_ = value;
 }
 
 int HostResolverImpl::Resolve(const RequestInfo& info,
@@ skipping 418 matching lines @@
   probe_weak_ptr_factory_.InvalidateWeakPtrs();
   if (cache_.get())
     cache_->clear();
 #if defined(OS_POSIX) && !defined(OS_MACOSX) && !defined(OS_ANDROID)
   new LoopbackProbeJob(probe_weak_ptr_factory_.GetWeakPtr());
 #endif
   AbortAllInProgressJobs();
   // |this| may be deleted inside AbortAllInProgressJobs().
 }
 
+void HostResolverImpl::OnConnectionTypeChanged(
+    NetworkChangeNotifier::ConnectionType type) {
+  proc_params_.unresponsive_delay = GetUnresponsiveDelay(type);
+}
+
 void HostResolverImpl::OnInitialDNSConfigRead() {
   UpdateDNSConfig(false);
 }
 
 void HostResolverImpl::OnDNSChanged() {
   UpdateDNSConfig(true);
 }
 
 void HostResolverImpl::UpdateDNSConfig(bool config_changed) {
   DnsConfig dns_config;
@@ skipping 88 matching lines @@
     dns_client_->SetConfig(dns_config);
     num_dns_failures_ = 0;
     if (dns_client_->GetConfig())
       UMA_HISTOGRAM_BOOLEAN("AsyncDNS.DnsClientEnabled", true);
   }
 
   AbortDnsTasks();
 }
 
 }  // namespace net