Don't probe for IPv6 connectivity when resolving IPv6 literals.

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"
 
 #if defined(OS_WIN)
 #include <Winsock2.h>
 #elif defined(OS_POSIX)
 #include <netdb.h>
@@ skipping 2136 matching lines @@
   }
 }
 
 HostResolverImpl::Key HostResolverImpl::GetEffectiveKeyForRequest(
     const RequestInfo& info, const BoundNetLog& net_log) const {
   HostResolverFlags effective_flags =
       info.host_resolver_flags() | additional_resolver_flags_;
   AddressFamily effective_address_family = info.address_family();
 
   if (info.address_family() == ADDRESS_FAMILY_UNSPECIFIED) {
-    unsigned char ip_number[4];
-    url::Component host_comp(0, info.hostname().size());
-    int num_components;
+    IPAddressNumber ip_number;
     if (probe_ipv6_support_ && !use_local_ipv6_ &&
-        // Don't bother IPv6 probing when resolving IPv4 literals.
-        url::IPv4AddressToNumber(info.hostname().c_str(), host_comp, ip_number,
-                                 &num_components) != url::CanonHostInfo::IPV4) {
+        // When resolving IPv4 literals, there's no need to probe for IPv6.
+        // When resolving IPv6 literals, there's no benefit to artificially
+        // limiting our resolution based on a probe.  We've already
+        // checked that this query is UNSPECIFIED (see info.address_family()
+        // check above) and that default_address_family_ is UNSPECIFIED
+        // (prove_ipv6_support_ is false if default_address_family_ is
+        // set) so the code requesting the resolution should be amenable to
+        // receiving a IPv6 resolution.
+        !ParseIPLiteralToNumber(info.hostname(), &ip_number)) {

[mmenke, 2015/04/13 16:43:51]

Wonder if it'd be cleaner just to move ParseIPLiteralToNumber out of
ResolverHelper, and have the two resolve functions call it directly, before this
method.

[pauljensen, 2015/04/15 01:29:29]

Done.

       // Google DNS address.
       const uint8 kIPv6Address[] =
           { 0x20, 0x01, 0x48, 0x60, 0x48, 0x60, 0x00, 0x00,
             0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x88, 0x88 };
       IPAddressNumber address(kIPv6Address,
                               kIPv6Address + arraysize(kIPv6Address));
       BoundNetLog probe_net_log = BoundNetLog::Make(
           net_log.net_log(), NetLog::SOURCE_IPV6_REACHABILITY_CHECK);
       probe_net_log.BeginEvent(NetLog::TYPE_IPV6_REACHABILITY_CHECK,
                                net_log.source().ToEventParametersCallback());
@@ skipping 187 matching lines @@
     dns_client_->SetConfig(dns_config);
     num_dns_failures_ = 0;
     if (dns_client_->GetConfig())
       UMA_HISTOGRAM_BOOLEAN("AsyncDNS.DnsClientEnabled", true);
   }
 
   AbortDnsTasks();
 }
 
 }  // namespace net