Add a mechanism to disable IPv6....

net/base/host_resolver_proc.cc

 // 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.
 
 #include "net/base/host_resolver_proc.h"
 
 #include "build/build_config.h"
 
 #if defined(OS_WIN)
 #include <ws2tcpip.h>
@@ skipping 34 matching lines @@
   default_proc_ = proc;
   return old;
 }
 
 // static
 HostResolverProc* HostResolverProc::GetDefault() {
   return default_proc_;
 }
 
 int HostResolverProc::ResolveUsingPrevious(const std::string& host,
+                                           AddressFamily address_family,
                                            AddressList* addrlist) {
   if (previous_proc_)
-    return previous_proc_->Resolve(host, addrlist);
+    return previous_proc_->Resolve(host, address_family, addrlist);
 
   // Final fallback is the system resolver.
-  return SystemHostResolverProc(host, addrlist);
+  return SystemHostResolverProc(host, address_family, addrlist);
 }
 
 #if defined(OS_LINUX)
 // On Linux changes to /etc/resolv.conf can go unnoticed thus resulting in
 // DNS queries failing either because nameservers are unknown on startup
 // or because nameserver info has changed as a result of e.g. connecting to
 // a new network. Some distributions patch glibc to stat /etc/resolv.conf
 // to try to automatically detect such changes but these patches are not
 // universal and even patched systems such as Jaunty appear to need calls
 // to res_ninit to reload the nameserver information in different threads.
@@ skipping 46 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(DnsReloadTimer);
 };
 
 // A TLS slot to the TimeTicks for the current thread.
 // static
 ThreadLocalStorage::Slot DnsReloadTimer::tls_index_(base::LINKER_INITIALIZED);
 
 #endif  // defined(OS_LINUX)
 
-int SystemHostResolverProc(const std::string& host, AddressList* addrlist) {
+int SystemHostResolverProc(const std::string& host,
+                           AddressFamily address_family,
+                           AddressList* addrlist) {
   // The result of |getaddrinfo| for empty hosts is inconsistent across systems.
   // On Windows it gives the default interface's address, whereas on Linux it
   // gives an error. We will make it fail on all platforms for consistency.
   if (host.empty())
     return ERR_NAME_NOT_RESOLVED;
 
   struct addrinfo* ai = NULL;
   struct addrinfo hints = {0};
-  hints.ai_family = AF_UNSPEC;
+
+  switch (address_family) {
+    case ADDRESS_FAMILY_IPV4_ONLY:
+      hints.ai_family = AF_INET;
+      break;
+    default:
+      hints.ai_family = AF_UNSPEC;
+  }
 
 #if defined(OS_WIN)
   // DO NOT USE AI_ADDRCONFIG ON WINDOWS.
   //
   // The following comment in <winsock2.h> is the best documentation I found
   // on AI_ADDRCONFIG for Windows:
   //   Flags used in "hints" argument to getaddrinfo()
   //       - AI_ADDRCONFIG is supported starting with Vista
   //       - default is AI_ADDRCONFIG ON whether the flag is set or not
   //         because the performance penalty in not having ADDRCONFIG in
@@ skipping 30 matching lines @@
 #endif
 
   if (err)
     return ERR_NAME_NOT_RESOLVED;
 
   addrlist->Adopt(ai);
   return OK;
 }
 
 }  // namespace net