[net/dns] Add test DualFamilyLocalhost and fix it when DnsClient enabled.

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 232 matching lines @@
 }
 
 //-----------------------------------------------------------------------------
 
 AddressList EnsurePortOnAddressList(const AddressList& list, uint16 port) {
   if (list.empty() || list.front().port() == port)
     return list;
   return AddressList::CopyWithPort(list, port);
 }
 
+bool IsAllLocalhostOfOneFamily(const AddressList& list) {

[mmenke, 2013/04/17 15:42:32]

Think this function is worth a short description.

[mmenke, 2013/04/17 15:42:32]

This function name seems to be inaccurate.  We check if they're localhost of any
family, rather than all of the same family.  The other function with this name
makes sure they were all in the same family.

[mmenke, 2013/04/17 15:42:32]

optional nit:  Suggest using "addresses" rather than "list" to match the calling
function.

[szym, 2013/04/17 17:09:16]

Done.

[szym, 2013/04/17 17:09:16]

Done. Also changed "localhost" to "loopback" which is more accurate.

[szym, 2013/04/17 17:09:16]

Done.

+  const uint8 kIPv6Loopback[] = { 0, 0, 0, 0, 0, 0, 0, 0,
+                                  0, 0, 0, 0, 0, 0, 0, 1 };
+  for (unsigned i = 0; i < list.size(); ++i) {
+    const IPAddressNumber& address = list[i].address();
+    switch (list[i].GetFamily()) {

[mmenke, 2013/04/17 15:42:32]

nit:  address.GetFamily()

[szym, 2013/04/17 17:09:16]

GetFamily is a function of IPEndPoint. IPAddressNumber is just a std::vector.

+      case ADDRESS_FAMILY_IPV4:
+        if (address[0] != 127) return false;

[mmenke, 2013/04/17 15:42:32]

nit:  Line break before "return".

[szym, 2013/04/17 17:09:16]

Done.

+        break;
+      case ADDRESS_FAMILY_IPV6:

[mmenke, 2013/04/17 15:42:32]

Do we even need to check for IPv6?  I'm not particularly opposed to it, but
since we don't currently detect the IPv6-only support...

[szym, 2013/04/17 17:09:16]

We don't, and this code path will not be exercised (only called if
DEFAULT_FAMILY_SET_DUE_TO_NO_IPV6).

Could change it to IsAllIPv4Loopback.

[mmenke, 2013/04/17 17:35:00]

I think we should go ahead and do that.  If we need more functionality in the
future, can add it.

+        if (!std::equal(address.begin(), address.end(), kIPv6Loopback))
+          return false;
+        break;
+      default:
+        NOTREACHED();
+    }
+  }
+  return true;
+}
+
 // Creates NetLog parameters when the resolve failed.
 base::Value* NetLogProcTaskFailedCallback(uint32 attempt_number,
                                           int net_error,
                                           int os_error,
                                           NetLog::LogLevel /* log_level */) {
   DictionaryValue* dict = new DictionaryValue();
   if (attempt_number)
     dict->SetInteger("attempt_number", attempt_number);
 
   dict->SetInteger("net_error", net_error);
@@ skipping 1680 matching lines @@
   }
   return true;
 }
 
 bool HostResolverImpl::ServeFromHosts(const Key& key,
                                       const RequestInfo& info,
                                       AddressList* addresses) {
   DCHECK(addresses);
   if (!HaveDnsConfig())
     return false;
-
   addresses->clear();
 
   // HOSTS lookups are case-insensitive.
   std::string hostname = StringToLowerASCII(key.hostname);
 
   const DnsHosts& hosts = dns_client_->GetConfig()->hosts;
 
   // If |address_family| is ADDRESS_FAMILY_UNSPECIFIED other implementations
   // (glibc and c-ares) return the first matching line. We have more
   // flexibility, but lose implicit ordering.
   // We prefer IPv6 because "happy eyeballs" will fall back to IPv4 if
   // necessary.
   if (key.address_family == ADDRESS_FAMILY_IPV6 ||
       key.address_family == ADDRESS_FAMILY_UNSPECIFIED) {
     DnsHosts::const_iterator it = hosts.find(
         DnsHostsKey(hostname, ADDRESS_FAMILY_IPV6));
     if (it != hosts.end())
       addresses->push_back(IPEndPoint(it->second, info.port()));
   }
 
   if (key.address_family == ADDRESS_FAMILY_IPV4 ||
       key.address_family == ADDRESS_FAMILY_UNSPECIFIED) {
     DnsHosts::const_iterator it = hosts.find(
         DnsHostsKey(hostname, ADDRESS_FAMILY_IPV4));
     if (it != hosts.end())
       addresses->push_back(IPEndPoint(it->second, info.port()));
   }
 
+  // If got only loopback addresses and the family was restricted, resolve
+  // again, without restrictions. See SystemHostResolverCall for rationale.
+  if ((key.host_resolver_flags &
+          HOST_RESOLVER_DEFAULT_FAMILY_SET_DUE_TO_NO_IPV6) &&
+      IsAllLocalhostOfOneFamily(*addresses)) {
+    Key new_key(key);
+    new_key.address_family = ADDRESS_FAMILY_UNSPECIFIED;
+    new_key.host_resolver_flags &=
+        ~HOST_RESOLVER_DEFAULT_FAMILY_SET_DUE_TO_NO_IPV6;
+    return ServeFromHosts(new_key, info, addresses);
+  }
   return !addresses->empty();
 }
 
 void HostResolverImpl::CacheResult(const Key& key,
                                    const HostCache::Entry& entry,
                                    base::TimeDelta ttl) {
   if (cache_.get())
     cache_->Set(key, entry, base::TimeTicks::Now(), ttl);
 }
 
@@ skipping 119 matching lines @@
 #if defined(OS_POSIX) && !defined(OS_MACOSX)
   new LoopbackProbeJob(probe_weak_ptr_factory_.GetWeakPtr());
 #endif
   AbortAllInProgressJobs();
   // |this| may be deleted inside AbortAllInProgressJobs().
 }
 
 void HostResolverImpl::OnDNSChanged() {
   DnsConfig dns_config;
   NetworkChangeNotifier::GetDnsConfig(&dns_config);
+
   if (net_log_) {
     net_log_->AddGlobalEntry(
         NetLog::TYPE_DNS_CONFIG_CHANGED,
         base::Bind(&NetLogDnsConfigCallback, &dns_config));
   }
 
   // TODO(szym): Remove once http://crbug.com/137914 is resolved.
   received_dns_config_ = dns_config.IsValid();
 
   num_dns_failures_ = 0;
@@ skipping 67 matching lines @@
   }
   DnsConfig dns_config;
   NetworkChangeNotifier::GetDnsConfig(&dns_config);
   dns_client_->SetConfig(dns_config);
   num_dns_failures_ = 0;
   if (dns_config.IsValid())
     UMA_HISTOGRAM_BOOLEAN("AsyncDNS.DnsClientEnabled", true);
 }
 
 }  // namespace net