Add a mechanism to disable IPv6....

net/base/host_resolver_proc.h

 // Copyright (c) 2009 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_PROC_H_
 #define NET_BASE_HOST_RESOLVER_PROC_H_
 
 #include <string>
 
 #include "base/ref_counted.h"
+#include "net/base/address_family.h"
 
 namespace net {
 
 class AddressList;
 
 // Interface for a getaddrinfo()-like procedure. This is used by unit-tests
 // to control the underlying resolutions in HostResolverImpl. HostResolverProcs
 // can be chained together; they fallback to the next procedure in the chain
 // by calling ResolveUsingPrevious().
 //
 // Note that implementations of HostResolverProc *MUST BE THREADSAFE*, since
 // the HostResolver implementation using them can be multi-threaded.
 class HostResolverProc : public base::RefCountedThreadSafe<HostResolverProc> {
  public:
   explicit HostResolverProc(HostResolverProc* previous);
   virtual ~HostResolverProc() {}
 
-  // Resolves |host| to an address list. If successful returns OK and fills
-  // |addrlist| with a list of socket addresses. Otherwise returns a
-  // network error code.
-  virtual int Resolve(const std::string& host, AddressList* addrlist) = 0;
+  // Resolves |host| to an address list, restricting the results to addresses
+  // in |address_family|. If successful returns OK and fills |addrlist| with
+  // a list of socket addresses. Otherwise returns a network error code.
+  virtual int Resolve(const std::string& host,
+                      AddressFamily address_family,
+                      AddressList* addrlist) = 0;
 
  protected:
   // Asks the fallback procedure (if set) to do the resolve.
-  int ResolveUsingPrevious(const std::string& host, AddressList* addrlist);
+  int ResolveUsingPrevious(const std::string& host,
+                           AddressFamily address_family,
+                           AddressList* addrlist);
 
  private:
   friend class HostResolverImpl;
   friend class MockHostResolverBase;
   friend class ScopedDefaultHostResolverProc;
 
   // Sets the previous procedure in the chain.
   void set_previous_proc(HostResolverProc* proc) {
     previous_proc_ = proc;
   }
 
   // Sets the default host resolver procedure that is used by HostResolverImpl.
   // This can be used through ScopedDefaultHostResolverProc to set a catch-all
   // DNS block in unit-tests (individual tests should use MockHostResolver to
   // prevent hitting the network).
   static HostResolverProc* SetDefault(HostResolverProc* proc);
   static HostResolverProc* GetDefault();
 
  private:
   scoped_refptr<HostResolverProc> previous_proc_;
   static HostResolverProc* default_proc_;
 
   DISALLOW_COPY_AND_ASSIGN(HostResolverProc);
 };
 
 // Resolves |host| to an address list, using the system's default host resolver.
 // (i.e. this calls out to getaddrinfo()). If successful returns OK and fills
 // |addrlist| with a list of socket addresses. Otherwise returns a
 // network error code.
-int SystemHostResolverProc(const std::string& host, AddressList* addrlist);
+int SystemHostResolverProc(const std::string& host,
+                           AddressFamily address_family,
+                           AddressList* addrlist);
 
 }  // namespace net
 
 #endif  // NET_BASE_HOST_RESOLVER_PROC_H_