Utility to resolve an hostname using Chromium's code in net/dns

net/base/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/base/host_resolver_impl.h"
 
 #if defined(OS_WIN)
 #include <Winsock2.h>
 #elif defined(OS_POSIX)
 #include <netdb.h>
@@ skipping 416 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];
 };
 
+}  // anonymous namespace
+
 //-----------------------------------------------------------------------------
 
 HostResolver* CreateHostResolver(size_t max_concurrent_resolves,
                                  size_t max_retry_attempts,
                                  HostCache* cache,
                                  scoped_ptr<DnsConfigService> config_service,
                                  NetLog* net_log) {
   if (max_concurrent_resolves == HostResolver::kDefaultParallelism)
     max_concurrent_resolves = kDefaultMaxProcTasks;
 
   // TODO(szym): Add experiments with reserved slots for higher priority
   // requests.
 
   PrioritizedDispatcher::Limits limits(NUM_PRIORITIES, max_concurrent_resolves);
 
   HostResolverImpl* resolver = new HostResolverImpl(
       cache,
       limits,
       HostResolverImpl::ProcTaskParams(NULL, max_retry_attempts),
       config_service.Pass(),
       net_log);
 
   return resolver;
 }
 
-}  // anonymous namespace
-
-//-----------------------------------------------------------------------------
-
 HostResolver* CreateSystemHostResolver(size_t max_concurrent_resolves,
                                        size_t max_retry_attempts,
                                        NetLog* net_log) {
   return CreateHostResolver(max_concurrent_resolves,
                             max_retry_attempts,
                             HostCache::CreateDefaultCache(),
                             scoped_ptr<DnsConfigService>(NULL),
                             net_log);
 }
 
@@ skipping 587 matching lines @@
     uint16 qtype = (key.address_family == ADDRESS_FAMILY_IPV6)
                    ? dns_protocol::kTypeAAAA
                    : dns_protocol::kTypeA;
     // TODO(szym): Implement "happy eyeballs".
     transaction_ = factory->CreateTransaction(
         key.hostname,
         qtype,
         base::Bind(&DnsTask::OnTransactionComplete, base::Unretained(this),
                    base::TimeTicks::Now()),
         net_log_);
+

[szym, 2012/05/14 18:48:32]

No need for this empty line.

[Daniele, 2012/05/17 23:04:34]

Done.

     DCHECK(transaction_.get());
   }
 
   int Start() {
     net_log_.BeginEvent(NetLog::TYPE_HOST_RESOLVER_IMPL_DNS_TASK, NULL);
     return transaction_->Start();
   }
 
   void OnTransactionComplete(const base::TimeTicks& start_time,
                              DnsTransaction* transaction,
@@ skipping 467 matching lines @@
 #endif
   NetworkChangeNotifier::AddIPAddressObserver(this);
 #if defined(OS_POSIX) && !defined(OS_MACOSX) && !defined(OS_OPENBSD)
 #if !defined(OS_ANDROID)
   EnsureDnsReloaderInit();
 #endif
   NetworkChangeNotifier::AddDNSObserver(this);
 #endif
 
   if (dns_config_service_.get()) {
-    dns_config_service_->Watch(
-        base::Bind(&HostResolverImpl::OnDnsConfigChanged,
-                   base::Unretained(this)));
     dns_client_ = DnsClient::CreateClient(net_log_);
+    dns_config_service_->Watch(base::Bind(&HostResolverImpl::OnDnsConfigChanged,

[szym, 2012/05/14 18:48:32]

Why did you change the order? I'm okay with the new order, but I'm wondering
about the reasoning here.

[Daniele, 2012/05/17 23:04:34]

I changed it because of the way I was calling the callback from
DnsConfigServiceMock inside the Watch method. I needed dns_client_ to be created
before calling the callback.
Now I changed the code as you suggested and there is no need for this.

On 2012/05/14 18:48:32, szym wrote:

+                                           base::Unretained(this)));
   }
 }
 
 HostResolverImpl::~HostResolverImpl() {
   DiscardIPv6ProbeJob();
 
   // This will also cancel all outstanding requests.
   STLDeleteValues(&jobs_);
 
   NetworkChangeNotifier::RemoveIPAddressObserver(this);
@@ skipping 401 matching lines @@
 
   if (self && dns_config.IsValid())
     TryServingAllJobsFromHosts();
 }
 
 bool HostResolverImpl::HaveDnsConfig() const {
   return (dns_client_.get() != NULL) && (dns_client_->GetConfig() != NULL);
 }
 
 }  // namespace net