[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);
 }
 
+// Returns true if |addresses| contains only IPv4 loopback addresses.
+bool IsAllIPv4Loopback(const AddressList& addresses) {
+  for (unsigned i = 0; i < addresses.size(); ++i) {
+    const IPAddressNumber& address = addresses[i].address();
+    switch (addresses[i].GetFamily()) {
+      case ADDRESS_FAMILY_IPV4:
+        if (address[0] != 127)
+          return false;
+        break;
+      case ADDRESS_FAMILY_IPV6:
+        return false;
+      default:
+        NOTREACHED();
+        return false;
+    }
+  }
+  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) &&
+      IsAllIPv4Loopback(*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