Add a mechanism to disable IPv6....

net/base/host_resolver_impl.h

 // Copyright (c) 2006-2008 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.
 
 #ifndef NET_BASE_HOST_RESOLVER_IMPL_H_
 #define NET_BASE_HOST_RESOLVER_IMPL_H_
 
 #include <string>
 #include <vector>
 
 #include "net/base/host_cache.h"
 #include "net/base/host_resolver.h"
 #include "net/base/host_resolver_proc.h"
 
 namespace net {
 
 // For each hostname that is requested, HostResolver creates a
 // HostResolverImpl::Job. This job gets dispatched to a thread in the global
 // WorkerPool, where it runs SystemHostResolverProc(). If requests for that same
 // host are made while the job is already outstanding, then they are attached
 // to the existing job rather than creating a new one. This avoids doing
 // parallel resolves for the same host.
 //
 // The way these classes fit together is illustrated by:
 //
 //
 //            +----------- HostResolverImpl -------------+
 //            |                    |                     |
 //           Job                  Job                   Job
-//       (for host1)          (for host2)           (for hostX)
+//    (for host1, fam1)    (for host2, fam2)     (for hostx, famx)
 //       /    |   |            /   |   |             /   |   |
 //   Request ... Request  Request ... Request   Request ... Request
 //  (port1)     (port2)  (port3)      (port4)  (port5)      (portX)
 //
 //
 // When a HostResolverImpl::Job finishes its work in the threadpool, the
 // callbacks of each waiting request are run on the origin thread.
 //
 // Thread safety: This class is not threadsafe, and must only be called
 // from one thread!
@@ skipping 22 matching lines @@
                       RequestHandle* out_req,
                       LoadLog* load_log);
   virtual void CancelRequest(RequestHandle req);
   virtual void AddObserver(Observer* observer);
   virtual void RemoveObserver(Observer* observer);
   virtual HostCache* GetHostCache();
 
   // TODO(eroman): temp hack for http://crbug.com/15513
   virtual void Shutdown();
 
+  // Prevents returning IPv6 addresses from Resolve().
+  // The default is to allow IPv6 results.
+  virtual void DisableIPv6(bool disable_ipv6) {
+    disable_ipv6_ = disable_ipv6;
+  }
+
  private:
   class Job;
   class Request;
   typedef std::vector<Request*> RequestsList;
-  typedef base::hash_map<std::string, scoped_refptr<Job> > JobMap;
+  typedef HostCache::Key Key;
+  typedef std::map<Key, scoped_refptr<Job> > JobMap;
   typedef std::vector<Observer*> ObserversList;
 
   // Returns the HostResolverProc to use for this instance.
   HostResolverProc* effective_resolver_proc() const {
     return resolver_proc_ ?
         resolver_proc_.get() : HostResolverProc::GetDefault();
   }
 
   // Adds a job to outstanding jobs list.
   void AddOutstandingJob(Job* job);
 
-  // Returns the outstanding job for |hostname|, or NULL if there is none.
-  Job* FindOutstandingJob(const std::string& hostname);
+  // Returns the outstanding job for |key|, or NULL if there is none.
+  Job* FindOutstandingJob(const Key& key);
 
   // Removes |job| from the outstanding jobs list.
   void RemoveOutstandingJob(Job* job);
 
   // Callback for when |job| has completed with |error| and |addrlist|.
   void OnJobComplete(Job* job, int error, const AddressList& addrlist);
 
   // Called when a request has just been started.
   void OnStartRequest(LoadLog* load_log,
                       int request_id,
@@ skipping 24 matching lines @@
   ObserversList observers_;
 
   // Monotonically increasing ID number to assign to the next request.
   // Observers are the only consumers of this ID number.
   int next_request_id_;
 
   // The procedure to use for resolving host names. This will be NULL, except
   // in the case of unit-tests which inject custom host resolving behaviors.
   scoped_refptr<HostResolverProc> resolver_proc_;
 
+  // Set to true if only IPv4 address are to be returned by Resolve().
+  bool disable_ipv6_;

[Lorenzo Colitti, 2009/10/21 23:14:08]

Instead, why not make this be "int desired_address_family" It could default to
AF_UNSPEC and then you could disable IPv6 by setting it to AF_INET.

The advantage is that you can pass this value directly into getaddrinfo(), thus
simplifying the code. Also, it's more flexible, since it allows the caller to
disable IPv6, disable IPv4, or request any address family he wants.

[eroman, 2009/10/21 23:32:07]

Done.

See proposed change here: http://codereview.chromium.org/303026

(as this codereview was already committed).

+
   // TODO(eroman): temp hack for http://crbug.com/15513
   bool shutdown_;
 
   DISALLOW_COPY_AND_ASSIGN(HostResolverImpl);
 };
 
 }  // namespace net
 
 #endif  // NET_BASE_HOST_RESOLVER_IMPL_H_