[net/dns] Resolve AF_UNSPEC on dual-stacked systems. Sort addresses according to RFC3484.

Original review: http://codereview.chromium.org/10442098/

BUG=113993
TEST=./net_unittests --gtest_filter=AddressSorter*:HostResolverImplDnsTest.DnsTaskUnspec

Review URL: https://chromiumcodereview.appspot.com/10855179

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@151750 0039d316-1c4b-4281-b951-d872f2087c98

net/base/host_resolver_impl.cc

@@ -38,6 +38,7 @@
 #include "net/base/net_errors.h"
 #include "net/base/net_log.h"
 #include "net/base/net_util.h"
+#include "net/dns/address_sorter.h"
 #include "net/dns/dns_client.h"
 #include "net/dns/dns_config_service.h"
 #include "net/dns/dns_protocol.h"
@@ -609,7 +610,7 @@ class HostResolverImpl::ProcTask
   void Cancel() {
     DCHECK(origin_loop_->BelongsToCurrentThread());
 
-    if (was_canceled())
+    if (was_canceled() || was_completed())
       return;
 
     callback_.Reset();
@@ -1042,32 +1043,33 @@ class HostResolverImpl::IPv6ProbeJob
 
 // Resolves the hostname using DnsTransaction.
 // TODO(szym): This could be moved to separate source file as well.
-class HostResolverImpl::DnsTask {
+class HostResolverImpl::DnsTask : public base::SupportsWeakPtr<DnsTask> {
  public:
   typedef base::Callback<void(int net_error,
                               const AddressList& addr_list,
                               base::TimeDelta ttl)> Callback;
 
-  DnsTask(DnsTransactionFactory* factory,
+  DnsTask(DnsClient* client,
           const Key& key,
           const Callback& callback,
           const BoundNetLog& job_net_log)
-      : callback_(callback), net_log_(job_net_log) {
-    DCHECK(factory);
+      : client_(client),
+        family_(key.address_family),
+        callback_(callback),
+        net_log_(job_net_log) {
+    DCHECK(client);
     DCHECK(!callback.is_null());
 
-    // For now we treat ADDRESS_FAMILY_UNSPEC as if it was IPV4.
-    uint16 qtype = (key.address_family == ADDRESS_FAMILY_IPV6)
-                   ? dns_protocol::kTypeAAAA
-                   : dns_protocol::kTypeA;
-    // TODO(szym): Implement "happy eyeballs".
-    transaction_ = factory->CreateTransaction(
+    // If unspecified, do IPv4 first, because suffix search will be faster.
+    uint16 qtype = (family_ == ADDRESS_FAMILY_IPV6) ?
+                   dns_protocol::kTypeAAAA :
+                   dns_protocol::kTypeA;
+    transaction_ = client_->GetTransactionFactory()->CreateTransaction(
         key.hostname,
         qtype,
         base::Bind(&DnsTask::OnTransactionComplete, base::Unretained(this),
-                   base::TimeTicks::Now()),
+                   true /* first_query */, base::TimeTicks::Now()),
         net_log_);
-    DCHECK(transaction_.get());
   }
 
   int Start() {
@@ -1075,47 +1077,138 @@ class HostResolverImpl::DnsTask {
     return transaction_->Start();
   }
 
-  void OnTransactionComplete(const base::TimeTicks& start_time,
+ private:
+  void OnTransactionComplete(bool first_query,
+                             const base::TimeTicks& start_time,
                              DnsTransaction* transaction,
                              int net_error,
                              const DnsResponse* response) {
     DCHECK(transaction);
     // Run |callback_| last since the owning Job will then delete this DnsTask.
-    DnsResponse::Result result = DnsResponse::DNS_SUCCESS;
-    if (net_error == OK) {
-      CHECK(response);
-      DNS_HISTOGRAM("AsyncDNS.TransactionSuccess",
+    if (net_error != OK) {
+      DNS_HISTOGRAM("AsyncDNS.TransactionFailure",
                     base::TimeTicks::Now() - start_time);
-      AddressList addr_list;
-      base::TimeDelta ttl;
-      result = response->ParseToAddressList(&addr_list, &ttl);
-      UMA_HISTOGRAM_ENUMERATION("AsyncDNS.ParseToAddressList",
-                                result,
-                                DnsResponse::DNS_PARSE_RESULT_MAX);
-      if (result == DnsResponse::DNS_SUCCESS) {
-        net_log_.EndEvent(NetLog::TYPE_HOST_RESOLVER_IMPL_DNS_TASK,
-                          addr_list.CreateNetLogCallback());
-        callback_.Run(net_error, addr_list, ttl);
+      OnFailure(net_error, DnsResponse::DNS_PARSE_OK);
+      return;
+    }
+
+    CHECK(response);
+    DNS_HISTOGRAM("AsyncDNS.TransactionSuccess",
+                  base::TimeTicks::Now() - start_time);
+    AddressList addr_list;
+    base::TimeDelta ttl;
+    DnsResponse::Result result = response->ParseToAddressList(&addr_list, &ttl);
+    UMA_HISTOGRAM_ENUMERATION("AsyncDNS.ParseToAddressList",
+                              result,
+                              DnsResponse::DNS_PARSE_RESULT_MAX);
+    if (result != DnsResponse::DNS_PARSE_OK) {
+      // Fail even if the other query succeeds.
+      OnFailure(ERR_DNS_MALFORMED_RESPONSE, result);
+      return;
+    }
+
+    bool needs_sort = false;
+    if (first_query) {
+      DCHECK(client_->GetConfig()) <<
+          "Transaction should have been aborted when config changed!";
+      if (family_ == ADDRESS_FAMILY_IPV6) {
+        needs_sort = (addr_list.size() > 1);
+      } else if (family_ == ADDRESS_FAMILY_UNSPECIFIED) {
+        first_addr_list_ = addr_list;
+        first_ttl_ = ttl;
+        // Use fully-qualified domain name to avoid search.
+        transaction_ = client_->GetTransactionFactory()->CreateTransaction(
+            response->GetDottedName() + ".",
+            dns_protocol::kTypeAAAA,
+            base::Bind(&DnsTask::OnTransactionComplete, base::Unretained(this),
+                       false /* first_query */, base::TimeTicks::Now()),
+            net_log_);
+        net_error = transaction_->Start();
+        if (net_error != ERR_IO_PENDING)
+          OnFailure(net_error, DnsResponse::DNS_PARSE_OK);
         return;
       }
-      net_error = ERR_DNS_MALFORMED_RESPONSE;
     } else {
-      DNS_HISTOGRAM("AsyncDNS.TransactionFailure",
+      DCHECK_EQ(ADDRESS_FAMILY_UNSPECIFIED, family_);
+      bool has_ipv6_addresses = !addr_list.empty();
+      if (!first_addr_list_.empty()) {
+        ttl = std::min(ttl, first_ttl_);
+        // Place IPv4 addresses after IPv6.
+        addr_list.insert(addr_list.end(), first_addr_list_.begin(),
+                                          first_addr_list_.end());
+      }
+      needs_sort = (has_ipv6_addresses && addr_list.size() > 1);
+    }
+
+    if (addr_list.empty()) {
+      // TODO(szym): Don't fallback to ProcTask in this case.
+      OnFailure(ERR_NAME_NOT_RESOLVED, DnsResponse::DNS_PARSE_OK);
+      return;
+    }
+
+    if (needs_sort) {
+      // Sort could complete synchronously.
+      client_->GetAddressSorter()->Sort(
+          addr_list,
+          base::Bind(&DnsTask::OnSortComplete, AsWeakPtr(),
+                     base::TimeTicks::Now(),
+                     ttl));
+    } else {
+      OnSuccess(addr_list, ttl);
+    }
+  }
+
+  void OnSortComplete(base::TimeTicks start_time,
+                      base::TimeDelta ttl,
+                      bool success,
+                      const AddressList& addr_list) {
+    if (!success) {
+      DNS_HISTOGRAM("AsyncDNS.SortFailure",
                     base::TimeTicks::Now() - start_time);
+      OnFailure(ERR_DNS_SORT_ERROR, DnsResponse::DNS_PARSE_OK);
+      return;
+    }
+
+    DNS_HISTOGRAM("AsyncDNS.SortSuccess",
+                  base::TimeTicks::Now() - start_time);
+
+    // AddressSorter prunes unusable destinations.
+    if (addr_list.empty()) {
+      LOG(WARNING) << "Address list empty after RFC3484 sort";
+      OnFailure(ERR_NAME_NOT_RESOLVED, DnsResponse::DNS_PARSE_OK);
+      return;
     }
+
+    OnSuccess(addr_list, ttl);
+  }
+
+  void OnFailure(int net_error, DnsResponse::Result result) {
+    DCHECK_NE(OK, net_error);
     net_log_.EndEvent(
         NetLog::TYPE_HOST_RESOLVER_IMPL_DNS_TASK,
         base::Bind(&NetLogDnsTaskFailedCallback, net_error, result));
     callback_.Run(net_error, AddressList(), base::TimeDelta());
   }
 
- private:
+  void OnSuccess(const AddressList& addr_list, base::TimeDelta ttl) {
+    net_log_.EndEvent(NetLog::TYPE_HOST_RESOLVER_IMPL_DNS_TASK,
+                      addr_list.CreateNetLogCallback());
+    callback_.Run(OK, addr_list, ttl);
+  }
+
+  DnsClient* client_;
+  AddressFamily family_;
   // The listener to the results of this DnsTask.
   Callback callback_;
-
   const BoundNetLog net_log_;
 
   scoped_ptr<DnsTransaction> transaction_;
+
+  // Results from the first transaction. Used only if |family_| is unspecified.
+  AddressList first_addr_list_;
+  base::TimeDelta first_ttl_;
+
+  DISALLOW_COPY_AND_ASSIGN(DnsTask);
 };
 
 //-----------------------------------------------------------------------------
@@ -1214,7 +1307,7 @@ class HostResolverImpl::Job : public PrioritizedDispatcher::Job {
   }
 
   // Marks |req| as cancelled. If it was the last active Request, also finishes
-  // this Job marking it either as aborted or cancelled, and deletes it.
+  // this Job, marking it as cancelled, and deletes it.
   void CancelRequest(Request* req) {
     DCHECK_EQ(key_.hostname, req->info().hostname());
     DCHECK(!req->was_canceled());
@@ -1381,7 +1474,7 @@ class HostResolverImpl::Job : public PrioritizedDispatcher::Job {
   void StartDnsTask() {
     DCHECK(resolver_->HaveDnsConfig());
     dns_task_.reset(new DnsTask(
-        resolver_->dns_client_->GetTransactionFactory(),
+        resolver_->dns_client_.get(),
         key_,
         base::Bind(&Job::OnDnsTaskComplete, base::Unretained(this)),
         net_log_));
@@ -1415,6 +1508,7 @@ class HostResolverImpl::Job : public PrioritizedDispatcher::Job {
     }
 
     UmaAsyncDnsResolveStatus(RESOLVE_STATUS_DNS_SUCCESS);
+
     CompleteRequests(net_error, addr_list, ttl);
   }
 

net/base/host_resolver_impl.h

@@ -19,14 +19,17 @@
 #include "net/base/host_resolver.h"
 #include "net/base/host_resolver_proc.h"
 #include "net/base/net_export.h"
-#include "net/base/net_log.h"
 #include "net/base/network_change_notifier.h"
 #include "net/base/prioritized_dispatcher.h"
-#include "net/dns/dns_client.h"
-#include "net/dns/dns_config_service.h"
 
 namespace net {
 
+class BoundNetLog;
+class DnsClient;
+struct DnsConfig;
+class DnsConfigService;
+class NetLog;
+
 // For each hostname that is requested, HostResolver creates a
 // HostResolverImpl::Job. When this job gets dispatched it creates a ProcTask
 // which runs the given HostResolverProc on a WorkerPool thread. If requests for

net/base/host_resolver_impl_unittest.cc

@@ -1236,21 +1236,46 @@ DnsConfig CreateValidDnsConfig() {
 class HostResolverImplDnsTest : public HostResolverImplTest {
  protected:
   virtual void SetUp() OVERRIDE {
+    AddDnsRule("er", dns_protocol::kTypeA, MockDnsClientRule::FAIL_SYNC);
+    AddDnsRule("er", dns_protocol::kTypeAAAA, MockDnsClientRule::FAIL_SYNC);
+    AddDnsRule("nx", dns_protocol::kTypeA, MockDnsClientRule::FAIL_ASYNC);
+    AddDnsRule("nx", dns_protocol::kTypeAAAA, MockDnsClientRule::FAIL_ASYNC);
+    AddDnsRule("ok", dns_protocol::kTypeA, MockDnsClientRule::OK);
+    AddDnsRule("ok", dns_protocol::kTypeAAAA, MockDnsClientRule::OK);
+    AddDnsRule("4ok", dns_protocol::kTypeA, MockDnsClientRule::OK);
+    AddDnsRule("4ok", dns_protocol::kTypeAAAA, MockDnsClientRule::EMPTY);
+    AddDnsRule("6ok", dns_protocol::kTypeA, MockDnsClientRule::EMPTY);
+    AddDnsRule("6ok", dns_protocol::kTypeAAAA, MockDnsClientRule::OK);
+    AddDnsRule("4nx", dns_protocol::kTypeA, MockDnsClientRule::OK);
+    AddDnsRule("4nx", dns_protocol::kTypeAAAA, MockDnsClientRule::FAIL_ASYNC);
+    CreateResolver();
+  }
+
+  void CreateResolver() {
     config_service_ = new MockDnsConfigService();
     resolver_.reset(new HostResolverImpl(
         HostCache::CreateDefaultCache(),
         DefaultLimits(),
         DefaultParams(proc_),
         scoped_ptr<DnsConfigService>(config_service_),
-        CreateMockDnsClient(DnsConfig()),
+        CreateMockDnsClient(DnsConfig(), dns_rules_),
         NULL));
   }
 
+  // Adds a rule to |dns_rules_|. Must be followed by |CreateResolver| to apply.
+  void AddDnsRule(const std::string& prefix,
+                  uint16 qtype,
+                  MockDnsClientRule::Result result) {
+    MockDnsClientRule rule = { prefix, qtype, result };
+    dns_rules_.push_back(rule);
+  }
+
   void ChangeDnsConfig(const DnsConfig& config) {
     config_service_->ChangeConfig(config);
     config_service_->ChangeHosts(config.hosts);
   }
 
+  MockDnsClientRuleList dns_rules_;
   // Owned by |resolver_|.
   MockDnsConfigService* config_service_;
 };
@@ -1298,11 +1323,38 @@ TEST_F(HostResolverImplDnsTest, DnsTask) {
   EXPECT_TRUE(requests_[5]->HasOneAddress("192.168.1.102", 80));
 }
 
+TEST_F(HostResolverImplDnsTest, DnsTaskUnspec) {
+  ChangeDnsConfig(CreateValidDnsConfig());
+
+  proc_->AddRuleForAllFamilies("4nx", "192.168.1.101");
+  // All other hostnames will fail in proc_.
+
+  EXPECT_EQ(ERR_IO_PENDING, CreateRequest("ok", 80)->Resolve());
+  EXPECT_EQ(ERR_IO_PENDING, CreateRequest("4ok", 80)->Resolve());
+  EXPECT_EQ(ERR_IO_PENDING, CreateRequest("6ok", 80)->Resolve());
+  EXPECT_EQ(ERR_IO_PENDING, CreateRequest("4nx", 80)->Resolve());
+
+  proc_->SignalMultiple(requests_.size());
+
+  for (size_t i = 0; i < requests_.size(); ++i)
+    EXPECT_EQ(OK, requests_[i]->WaitForResult()) << i;
+
+  EXPECT_EQ(2u, requests_[0]->NumberOfAddresses());
+  EXPECT_TRUE(requests_[0]->HasAddress("127.0.0.1", 80));
+  EXPECT_TRUE(requests_[0]->HasAddress("::1", 80));
+  EXPECT_EQ(1u, requests_[1]->NumberOfAddresses());
+  EXPECT_TRUE(requests_[1]->HasAddress("127.0.0.1", 80));
+  EXPECT_EQ(1u, requests_[2]->NumberOfAddresses());
+  EXPECT_TRUE(requests_[2]->HasAddress("::1", 80));
+  EXPECT_EQ(1u, requests_[3]->NumberOfAddresses());
+  EXPECT_TRUE(requests_[3]->HasAddress("192.168.1.101", 80));
+}
+
 TEST_F(HostResolverImplDnsTest, ServeFromHosts) {
   // Initially, use empty HOSTS file.
   ChangeDnsConfig(CreateValidDnsConfig());
 
-  proc_->AddRuleForAllFamilies("", "0.0.0.0");  // Default to failures.
+  proc_->AddRuleForAllFamilies("", "");  // Default to failures.
   proc_->SignalMultiple(1u);  // For the first request which misses.
 
   Request* req0 = CreateRequest("er_ipv4", 80);
@@ -1353,7 +1405,7 @@ TEST_F(HostResolverImplDnsTest, ServeFromHosts) {
 TEST_F(HostResolverImplDnsTest, BypassDnsTask) {
   ChangeDnsConfig(CreateValidDnsConfig());
 
-  proc_->AddRuleForAllFamilies("", "0.0.0.0");  // Default to failures.
+  proc_->AddRuleForAllFamilies("", "");  // Default to failures.
 
   EXPECT_EQ(ERR_IO_PENDING, CreateRequest("ok.local", 80)->Resolve());
   EXPECT_EQ(ERR_IO_PENDING, CreateRequest("ok.local.", 80)->Resolve());

net/base/net_error_list.h

@@ -658,3 +658,6 @@ NET_ERROR(DNS_CACHE_MISS, -804)
 
 // Suffix search list rules prevent resolution of the given host name.
 NET_ERROR(DNS_SEARCH_EMPTY, -805)
+
+// Failed to sort addresses according to RFC3484.
+NET_ERROR(DNS_SORT_ERROR, -806)

net/base/net_util.cc

@@ -2216,6 +2216,12 @@ bool ParseIPLiteralToNumber(const std::string& ip_literal,
   return family == url_canon::CanonHostInfo::IPV4;
 }
 
+namespace {
+
+const unsigned char kIPv4MappedPrefix[] =
+    { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0xFF, 0xFF };
+}
+
 IPAddressNumber ConvertIPv4NumberToIPv6Number(
     const IPAddressNumber& ipv4_number) {
   DCHECK(ipv4_number.size() == 4);
@@ -2224,13 +2230,27 @@ IPAddressNumber ConvertIPv4NumberToIPv6Number(
   // <80 bits of zeros>  + <16 bits of ones> + <32-bit IPv4 address>.
   IPAddressNumber ipv6_number;
   ipv6_number.reserve(16);
-  ipv6_number.insert(ipv6_number.end(), 10, 0);
-  ipv6_number.push_back(0xFF);
-  ipv6_number.push_back(0xFF);
+  ipv6_number.insert(ipv6_number.end(),
+                     kIPv4MappedPrefix,
+                     kIPv4MappedPrefix + arraysize(kIPv4MappedPrefix));
   ipv6_number.insert(ipv6_number.end(), ipv4_number.begin(), ipv4_number.end());
   return ipv6_number;
 }
 
+bool IsIPv4Mapped(const IPAddressNumber& address) {
+  if (address.size() != kIPv6AddressSize)
+    return false;
+  return std::equal(address.begin(),
+                    address.begin() + arraysize(kIPv4MappedPrefix),
+                    kIPv4MappedPrefix);
+}
+
+IPAddressNumber ConvertIPv4MappedToIPv4(const IPAddressNumber& address) {
+  DCHECK(IsIPv4Mapped(address));
+  return IPAddressNumber(address.begin() + arraysize(kIPv4MappedPrefix),
+                         address.end());
+}
+
 bool ParseCIDRBlock(const std::string& cidr_literal,
                     IPAddressNumber* ip_number,
                     size_t* prefix_length_in_bits) {

net/base/net_util.h

@@ -424,6 +424,14 @@ NET_EXPORT_PRIVATE bool ParseIPLiteralToNumber(const std::string& ip_literal,
 NET_EXPORT_PRIVATE IPAddressNumber ConvertIPv4NumberToIPv6Number(
     const IPAddressNumber& ipv4_number);
 
+// Returns true iff |address| is an IPv4-mapped IPv6 address.
+NET_EXPORT_PRIVATE bool IsIPv4Mapped(const IPAddressNumber& address);
+
+// Converts an IPv4-mapped IPv6 address to IPv4 address. Should only be called
+// on IPv4-mapped IPv6 addresses.
+NET_EXPORT_PRIVATE IPAddressNumber ConvertIPv4MappedToIPv4(
+    const IPAddressNumber& address);
+
 // Parses an IP block specifier from CIDR notation to an
 // (IP address, prefix length) pair. Returns true on success and fills
 // |*ip_number| with the numeric value of the IP address and sets

net/base/net_util_unittest.cc

@@ -3049,6 +3049,29 @@ TEST(NetUtilTest, ConvertIPv4NumberToIPv6Number) {
             DumpIPNumber(ipv6_number));
 }
 
+TEST(NetUtilTest, IsIPv4Mapped) {
+  IPAddressNumber ipv4_number;
+  EXPECT_TRUE(ParseIPLiteralToNumber("192.168.0.1", &ipv4_number));
+  EXPECT_FALSE(IsIPv4Mapped(ipv4_number));
+
+  IPAddressNumber ipv6_number;
+  EXPECT_TRUE(ParseIPLiteralToNumber("::1", &ipv4_number));
+  EXPECT_FALSE(IsIPv4Mapped(ipv6_number));
+
+  IPAddressNumber ipv4mapped_number;
+  EXPECT_TRUE(ParseIPLiteralToNumber("::ffff:0101:1", &ipv4mapped_number));
+  EXPECT_TRUE(IsIPv4Mapped(ipv4mapped_number));
+}
+
+TEST(NetUtilTest, ConvertIPv4MappedToIPv4) {
+  IPAddressNumber ipv4mapped_number;
+  EXPECT_TRUE(ParseIPLiteralToNumber("::ffff:0101:1", &ipv4mapped_number));
+  IPAddressNumber expected;
+  EXPECT_TRUE(ParseIPLiteralToNumber("1.1.0.1", &expected));
+  IPAddressNumber result = ConvertIPv4MappedToIPv4(ipv4mapped_number);
+  EXPECT_EQ(expected, result);
+}
+
 // Test parsing invalid CIDR notation literals.
 TEST(NetUtilTest, ParseCIDRBlock_Invalid) {
   const char* bad_literals[] = {

net/dns/address_sorter.h

+// 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.
+
+#ifndef NET_DNS_ADDRESS_SORTER_H_
+#define NET_DNS_ADDRESS_SORTER_H_
+
+#include "base/basictypes.h"
+#include "base/callback.h"
+#include "base/memory/scoped_ptr.h"
+#include "net/base/net_export.h"
+
+namespace net {
+
+class AddressList;
+
+// Sorts AddressList according to RFC3484, by likelihood of successful
+// connection. Depending on the platform, the sort could be performed
+// asynchronously by the OS, or synchronously by local implementation.
+// AddressSorter does not necessarily preserve port numbers on the sorted list.
+class NET_EXPORT AddressSorter {
+ public:
+  typedef base::Callback<void(bool success,
+                              const AddressList& list)> CallbackType;
+
+  virtual ~AddressSorter() {}
+
+  // Sorts |list|, which must include at least one IPv6 address.
+  // Calls |callback| upon completion. Could complete synchronously. Could
+  // complete after this AddressSorter is destroyed.
+  virtual void Sort(const AddressList& list,
+                    const CallbackType& callback) const = 0;
+
+  // Creates platform-dependent AddressSorter.
+  static scoped_ptr<AddressSorter> CreateAddressSorter();
+
+ protected:
+  AddressSorter() {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(AddressSorter);
+};
+
+}  // namespace net
+
+#endif  // NET_DNS_ADDRESS_SORTER_H_

net/dns/address_sorter_posix.h

+// 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.
+
+#ifndef NET_DNS_ADDRESS_SORTER_POSIX_H_
+#define NET_DNS_ADDRESS_SORTER_POSIX_H_
+
+#include <map>
+#include <vector>
+
+#include "base/threading/non_thread_safe.h"
+#include "net/base/address_list.h"
+#include "net/base/net_errors.h"
+#include "net/base/net_export.h"
+#include "net/base/net_util.h"
+#include "net/base/network_change_notifier.h"
+#include "net/dns/address_sorter.h"
+
+namespace net {
+
+class ClientSocketFactory;
+
+// This implementation uses explicit policy to perform the sorting. It is not
+// thread-safe and always completes synchronously.
+class NET_EXPORT_PRIVATE AddressSorterPosix
+    : public AddressSorter,
+      public base::NonThreadSafe,
+      public NetworkChangeNotifier::IPAddressObserver {
+ public:
+  // Generic policy entry.
+  struct PolicyEntry {
+    // IPv4 addresses must be mapped to IPv6.
+    unsigned char prefix[kIPv6AddressSize];
+    unsigned prefix_length;
+    unsigned value;
+  };
+
+  typedef std::vector<PolicyEntry> PolicyTable;
+
+  enum AddressScope {
+    SCOPE_UNDEFINED = 0,
+    SCOPE_NODELOCAL = 1,
+    SCOPE_LINKLOCAL = 2,
+    SCOPE_SITELOCAL = 5,
+    SCOPE_ORGLOCAL = 8,
+    SCOPE_GLOBAL = 14,
+  };
+
+  struct SourceAddressInfo {
+    // Values read from policy tables.
+    AddressScope scope;
+    unsigned label;
+
+    // Values from the OS, matter only if more than one source address is used.
+    unsigned prefix_length;
+    bool deprecated;  // vs. preferred RFC4862
+    bool home;        // vs. care-of RFC6275
+    bool native;
+  };
+
+  typedef std::map<IPAddressNumber, SourceAddressInfo> SourceAddressMap;
+
+  explicit AddressSorterPosix(ClientSocketFactory* socket_factory);
+  virtual ~AddressSorterPosix();
+
+  // AddressSorter:
+  virtual void Sort(const AddressList& list,
+                    const CallbackType& callback) const OVERRIDE;
+
+ private:
+  friend class AddressSorterPosixTest;
+
+  // NetworkChangeNotifier::IPAddressObserver:
+  virtual void OnIPAddressChanged() OVERRIDE;
+
+  // Fills |info| with values for |address| from policy tables.
+  void FillPolicy(const IPAddressNumber& address,
+                  SourceAddressInfo* info) const;
+
+  // Mutable to allow using default values for source addresses which were not
+  // found in most recent OnIPAddressChanged.
+  mutable SourceAddressMap source_map_;
+
+  ClientSocketFactory* socket_factory_;
+  PolicyTable precedence_table_;
+  PolicyTable label_table_;
+  PolicyTable ipv4_scope_table_;
+
+  DISALLOW_COPY_AND_ASSIGN(AddressSorterPosix);
+};
+
+}  // namespace net
+
+#endif  // NET_DNS_ADDRESS_SORTER_POSIX_H_

net/dns/address_sorter_unittest.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/address_sorter.h"
+
+#if defined(OS_WIN)
+#include <winsock2.h>
+#endif
+
+#include "base/bind.h"
+#include "base/logging.h"
+#include "net/base/address_list.h"
+#include "net/base/net_util.h"
+#include "net/base/test_completion_callback.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+#if defined(OS_WIN)
+#include "net/base/winsock_init.h"
+#endif
+
+namespace net {
+namespace {
+
+IPEndPoint MakeEndPoint(const std::string& str) {
+  IPAddressNumber addr;
+  CHECK(ParseIPLiteralToNumber(str, &addr));
+  return IPEndPoint(addr, 0);
+}
+
+void OnSortComplete(AddressList* result_buf,
+                    const CompletionCallback& callback,
+                    bool success,
+                    const AddressList& result) {
+  if (success)
+    *result_buf = result;
+  callback.Run(success ? OK : ERR_FAILED);
+}
+
+TEST(AddressSorterTest, Sort) {
+  int expected_result = OK;
+#if defined(OS_WIN)
+  EnsureWinsockInit();
+  SOCKET sock = socket(AF_INET6, SOCK_DGRAM, IPPROTO_UDP);
+  if (sock == INVALID_SOCKET) {
+    expected_result = ERR_FAILED;
+  } else {
+    closesocket(sock);
+  }
+#endif
+  scoped_ptr<AddressSorter> sorter(AddressSorter::CreateAddressSorter());
+  AddressList list;
+  list.push_back(MakeEndPoint("10.0.0.1"));
+  list.push_back(MakeEndPoint("8.8.8.8"));
+  list.push_back(MakeEndPoint("::1"));
+  list.push_back(MakeEndPoint("2001:4860:4860::8888"));
+
+  AddressList result;
+  TestCompletionCallback callback;
+  sorter->Sort(list, base::Bind(&OnSortComplete, &result,
+                                callback.callback()));
+  EXPECT_EQ(expected_result, callback.WaitForResult());
+}
+
+}  // namespace
+}  // namespace net

net/dns/address_sorter_win.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/address_sorter.h"
+
+#include <winsock2.h>
+
+#include <algorithm>
+
+#include "base/bind.h"
+#include "base/location.h"
+#include "base/logging.h"
+#include "base/threading/worker_pool.h"
+#include "base/win/windows_version.h"
+#include "net/base/address_list.h"
+#include "net/base/ip_endpoint.h"
+#include "net/base/winsock_init.h"
+
+namespace net {
+
+namespace {
+
+class AddressSorterWin : public AddressSorter {
+ public:
+  AddressSorterWin() {
+    EnsureWinsockInit();
+  }
+
+  virtual ~AddressSorterWin() {}
+
+  // AddressSorter:
+  virtual void Sort(const AddressList& list,
+                    const CallbackType& callback) const OVERRIDE {
+    DCHECK(!list.empty());
+    scoped_refptr<Job> job = new Job(list, callback);
+  }
+
+ private:
+  // Executes the SIO_ADDRESS_LIST_SORT ioctl on the WorkerPool, and
+  // performs the necessary conversions to/from AddressList.
+  class Job : public base::RefCountedThreadSafe<Job> {
+   public:
+    Job(const AddressList& list, const CallbackType& callback)
+        : callback_(callback),
+          buffer_size_(sizeof(SOCKET_ADDRESS_LIST) +
+                       list.size() * (sizeof(SOCKET_ADDRESS) +
+                                      sizeof(SOCKADDR_STORAGE))),
+          input_buffer_(reinterpret_cast<SOCKET_ADDRESS_LIST*>(
+              malloc(buffer_size_))),
+          output_buffer_(reinterpret_cast<SOCKET_ADDRESS_LIST*>(
+              malloc(buffer_size_))),
+          success_(false) {
+      input_buffer_->iAddressCount = list.size();
+      SOCKADDR_STORAGE* storage = reinterpret_cast<SOCKADDR_STORAGE*>(
+          input_buffer_->Address + input_buffer_->iAddressCount);
+
+      for (size_t i = 0; i < list.size(); ++i) {
+        IPEndPoint ipe = list[i];
+        // Addresses must be sockaddr_in6.
+        if (ipe.GetFamily() == AF_INET) {
+          ipe = IPEndPoint(ConvertIPv4NumberToIPv6Number(ipe.address()),
+                           ipe.port());
+        }
+
+        struct sockaddr* addr = reinterpret_cast<struct sockaddr*>(storage + i);
+        socklen_t addr_len = sizeof(SOCKADDR_STORAGE);
+        bool result = ipe.ToSockAddr(addr, &addr_len);
+        DCHECK(result);
+        input_buffer_->Address[i].lpSockaddr = addr;
+        input_buffer_->Address[i].iSockaddrLength = addr_len;
+      }
+
+      if (!base::WorkerPool::PostTaskAndReply(
+          FROM_HERE,
+          base::Bind(&Job::Run, this),
+          base::Bind(&Job::OnComplete, this),
+          false /* task is slow */)) {
+        LOG(ERROR) << "WorkerPool::PostTaskAndReply failed";
+        OnComplete();
+      }
+    }
+
+   private:
+    friend class base::RefCountedThreadSafe<Job>;
+    ~Job() {}
+
+    // Executed on the WorkerPool.
+    void Run() {
+      SOCKET sock = socket(AF_INET6, SOCK_DGRAM, IPPROTO_UDP);
+      if (sock == INVALID_SOCKET)
+        return;
+      DWORD result_size = 0;
+      int result = WSAIoctl(sock, SIO_ADDRESS_LIST_SORT, input_buffer_.get(),
+                            buffer_size_, output_buffer_.get(), buffer_size_,
+                            &result_size, NULL, NULL);
+      if (result == SOCKET_ERROR) {
+        LOG(ERROR) << "SIO_ADDRESS_LIST_SORT failed " << WSAGetLastError();
+      } else {
+        success_ = true;
+      }
+      closesocket(sock);
+    }
+
+    // Executed on the calling thread.
+    void OnComplete() {
+      AddressList list;
+      if (success_) {
+        list.reserve(output_buffer_->iAddressCount);
+        for (int i = 0; i < output_buffer_->iAddressCount; ++i) {
+          IPEndPoint ipe;
+          ipe.FromSockAddr(output_buffer_->Address[i].lpSockaddr,
+                           output_buffer_->Address[i].iSockaddrLength);
+          // Unmap V4MAPPED IPv6 addresses so that Happy Eyeballs works.
+          if (IsIPv4Mapped(ipe.address())) {
+            ipe = IPEndPoint(ConvertIPv4MappedToIPv4(ipe.address()),
+                                                     ipe.port());
+          }
+          list.push_back(ipe);
+        }
+      }
+      callback_.Run(success_, list);
+    }
+
+    const CallbackType callback_;
+    const size_t buffer_size_;
+    scoped_ptr_malloc<SOCKET_ADDRESS_LIST> input_buffer_;
+    scoped_ptr_malloc<SOCKET_ADDRESS_LIST> output_buffer_;
+    bool success_;
+
+    DISALLOW_COPY_AND_ASSIGN(Job);
+  };
+
+  DISALLOW_COPY_AND_ASSIGN(AddressSorterWin);
+};
+
+// Merges |list_ipv4| and |list_ipv6| before passing it to |callback|, but
+// only if |success| is true.
+void MergeResults(const AddressSorter::CallbackType& callback,
+                  const AddressList& list_ipv4,
+                  bool success,
+                  const AddressList& list_ipv6) {
+  if (!success) {
+    callback.Run(false, AddressList());
+    return;
+  }
+  AddressList list;
+  list.insert(list.end(), list_ipv6.begin(), list_ipv6.end());
+  list.insert(list.end(), list_ipv4.begin(), list_ipv4.end());
+  callback.Run(true, list);
+}
+
+// Wrapper for AddressSorterWin which does not sort IPv4 or IPv4-mapped
+// addresses but always puts them at the end of the list. Needed because the
+// SIO_ADDRESS_LIST_SORT does not support IPv4 addresses on Windows XP.
+class AddressSorterWinXP : public AddressSorter {
+ public:
+  AddressSorterWinXP() {}
+  virtual ~AddressSorterWinXP() {}
+
+  // AddressSorter:
+  virtual void Sort(const AddressList& list,
+                    const CallbackType& callback) const OVERRIDE {
+    AddressList list_ipv4;
+    AddressList list_ipv6;
+    for (size_t i = 0; i < list.size(); ++i) {
+      const IPEndPoint& ipe = list[i];
+      if (ipe.GetFamily() == AF_INET) {
+        list_ipv4.push_back(ipe);
+      } else {
+        list_ipv6.push_back(ipe);
+      }
+    }
+    if (!list_ipv6.empty()) {
+      sorter_.Sort(list_ipv6, base::Bind(&MergeResults, callback, list_ipv4));
+    } else {
+      NOTREACHED() << "Should not be called with IPv4-only addresses.";
+      callback.Run(true, list);
+    }
+  }
+
+ private:
+  AddressSorterWin sorter_;
+
+  DISALLOW_COPY_AND_ASSIGN(AddressSorterWinXP);
+};
+
+}  // namespace
+
+// static
+scoped_ptr<AddressSorter> AddressSorter::CreateAddressSorter() {
+  if (base::win::GetVersion() < base::win::VERSION_VISTA)
+    return scoped_ptr<AddressSorter>(new AddressSorterWinXP());
+  return scoped_ptr<AddressSorter>(new AddressSorterWin());
+}
+
+}  // namespace net
+

net/dns/dns_client.cc

@@ -7,6 +7,7 @@
 #include "base/bind.h"
 #include "base/rand_util.h"
 #include "net/base/net_log.h"
+#include "net/dns/address_sorter.h"
 #include "net/dns/dns_config_service.h"
 #include "net/dns/dns_session.h"
 #include "net/dns/dns_transaction.h"
@@ -18,7 +19,9 @@ namespace {
 
 class DnsClientImpl : public DnsClient {
  public:
-  explicit DnsClientImpl(NetLog* net_log) : net_log_(net_log) {}
+  explicit DnsClientImpl(NetLog* net_log)
+      : address_sorter_(AddressSorter::CreateAddressSorter()),
+        net_log_(net_log) {}
 
   virtual void SetConfig(const DnsConfig& config) OVERRIDE {
     factory_.reset();
@@ -40,9 +43,14 @@ class DnsClientImpl : public DnsClient {
     return session_.get() ? factory_.get() : NULL;
   }
 
+  virtual AddressSorter* GetAddressSorter() OVERRIDE {
+    return address_sorter_.get();
+  }
+
  private:
   scoped_refptr<DnsSession> session_;
   scoped_ptr<DnsTransactionFactory> factory_;
+  scoped_ptr<AddressSorter> address_sorter_;
 
   NetLog* net_log_;
 };

net/dns/dns_client.h

@@ -10,12 +10,14 @@
 
 namespace net {
 
+class AddressSorter;
 struct DnsConfig;
 class DnsTransactionFactory;
 class NetLog;
 
-// Convenience wrapper allows easy injection of DnsTransaction into
-// HostResolverImpl.
+// Convenience wrapper which allows easy injection of DnsTransaction into
+// HostResolverImpl. Pointers returned by the Get* methods are only guaranteed
+// to remain valid until next time SetConfig is called.
 class NET_EXPORT DnsClient {
  public:
   virtual ~DnsClient() {}
@@ -29,6 +31,9 @@ class NET_EXPORT DnsClient {
   // Returns NULL if the current config is not valid.
   virtual DnsTransactionFactory* GetTransactionFactory() = 0;
 
+  // Returns NULL if the current config is not valid.
+  virtual AddressSorter* GetAddressSorter() = 0;
+
   // Creates default client.
   static scoped_ptr<DnsClient> CreateClient(NetLog* net_log);
 };

net/dns/dns_response.cc

@@ -280,15 +280,13 @@ DnsResponse::Result DnsResponse::ParseToAddressList(
   }
 
   // TODO(szym): Extract TTL for NODATA results. http://crbug.com/115051
-  if (ip_addresses.empty())
-    return DNS_NO_ADDRESSES;
 
   // getcanonname in eglibc returns the first owner name of an A or AAAA RR.
   // If the response passed all the checks so far, then |expected_name| is it.
   *addr_list = AddressList::CreateFromIPAddressList(ip_addresses,
                                                     expected_name);
   *ttl = base::TimeDelta::FromSeconds(std::min(cname_ttl_sec, addr_ttl_sec));
-  return DNS_SUCCESS;
+  return DNS_PARSE_OK;
 }
 
 }  // namespace net

net/dns/dns_response.h

@@ -81,7 +81,7 @@ class NET_EXPORT_PRIVATE DnsResponse {
  public:
   // Possible results from ParseToAddressList.
   enum Result {
-    DNS_SUCCESS = 0,
+    DNS_PARSE_OK = 0,
     DNS_MALFORMED_RESPONSE,    // DnsRecordParser failed before the end of
                                // packet.
     DNS_MALFORMED_CNAME,       // Could not parse CNAME out of RRDATA.
@@ -90,7 +90,7 @@ class NET_EXPORT_PRIVATE DnsResponse {
     DNS_SIZE_MISMATCH,         // Got an address but size does not match.
     DNS_CNAME_AFTER_ADDRESS,   // Found CNAME after an address record.
     DNS_ADDRESS_TTL_MISMATCH,  // TTL of all address records are not identical.
-    DNS_NO_ADDRESSES,          // No address records found.
+    DNS_NO_ADDRESSES,          // OBSOLETE. No longer used.
     // Only add new values here.
     DNS_PARSE_RESULT_MAX,      // Bounding value for histograms.
   };

net/dns/dns_response_unittest.cc

@@ -299,7 +299,7 @@ TEST(DnsResponseTest, ParseToAddressList) {
     DnsResponse response(t.response_data, t.response_size, t.query_size);
     AddressList addr_list;
     base::TimeDelta ttl;
-    EXPECT_EQ(DnsResponse::DNS_SUCCESS,
+    EXPECT_EQ(DnsResponse::DNS_PARSE_OK,
               response.ParseToAddressList(&addr_list, &ttl));
     std::vector<const char*> expected_addresses(
         t.expected_addresses,
@@ -429,8 +429,9 @@ TEST(DnsResponseTest, ParseToAddressListFail) {
       DnsResponse::DNS_CNAME_AFTER_ADDRESS },
     { kResponseTTLMismatch, arraysize(kResponseTTLMismatch),
       DnsResponse::DNS_ADDRESS_TTL_MISMATCH },
+    // Not actually a failure, just an empty result.
     { kResponseNoAddresses, arraysize(kResponseNoAddresses),
-      DnsResponse::DNS_NO_ADDRESSES },
+      DnsResponse::DNS_PARSE_OK },
   };
 
   const size_t kQuerySize = 12 + 7;

net/dns/dns_test_util.cc

@@ -14,6 +14,7 @@
 #include "net/base/dns_util.h"
 #include "net/base/io_buffer.h"
 #include "net/base/net_errors.h"
+#include "net/dns/address_sorter.h"
 #include "net/dns/dns_client.h"
 #include "net/dns/dns_config_service.h"
 #include "net/dns/dns_protocol.h"
@@ -25,19 +26,29 @@
 namespace net {
 namespace {
 
-// A DnsTransaction which responds with loopback to all queries starting with
-// "ok", fails synchronously on all queries starting with "er", and NXDOMAIN to
-// all others.
+// A DnsTransaction which uses MockDnsClientRuleList to determine the response.
 class MockTransaction : public DnsTransaction,
                         public base::SupportsWeakPtr<MockTransaction> {
  public:
-  MockTransaction(const std::string& hostname,
+  MockTransaction(const MockDnsClientRuleList& rules,
+                  const std::string& hostname,
                   uint16 qtype,
                   const DnsTransactionFactory::CallbackType& callback)
-      : hostname_(hostname),
+      : result_(MockDnsClientRule::FAIL_SYNC),
+        hostname_(hostname),
         qtype_(qtype),
         callback_(callback),
         started_(false) {
+    // Find the relevant rule which matches |qtype| and prefix of |hostname|.
+    for (size_t i = 0; i < rules.size(); ++i) {
+      const std::string& prefix = rules[i].prefix;
+      if ((rules[i].qtype == qtype) &&
+          (hostname.size() >= prefix.size()) &&
+          (hostname.compare(0, prefix.size(), prefix) == 0)) {
+        result_ = rules[i].result;
+        break;
+      }
+    }
   }
 
   virtual const std::string& GetHostname() const OVERRIDE {
@@ -51,7 +62,7 @@ class MockTransaction : public DnsTransaction,
   virtual int Start() OVERRIDE {
     EXPECT_FALSE(started_);
     started_ = true;
-    if (hostname_.substr(0, 2) == "er")
+    if (MockDnsClientRule::FAIL_SYNC == result_)
       return ERR_NAME_NOT_RESOLVED;
     // Using WeakPtr to cleanly cancel when transaction is destroyed.
     MessageLoop::current()->PostTask(
@@ -62,54 +73,66 @@ class MockTransaction : public DnsTransaction,
 
  private:
   void Finish() {
-    if (hostname_.substr(0, 2) == "ok") {
-      std::string qname;
-      DNSDomainFromDot(hostname_, &qname);
-      DnsQuery query(0, qname, qtype_);
-
-      DnsResponse response;
-      char* buffer = response.io_buffer()->data();
-      int nbytes = query.io_buffer()->size();
-      memcpy(buffer, query.io_buffer()->data(), nbytes);
-
-      const uint16 kPointerToQueryName =
-          static_cast<uint16>(0xc000 | sizeof(net::dns_protocol::Header));
-
-      const uint32 kTTL = 86400;  // One day.
-
-      // Size of RDATA which is a IPv4 or IPv6 address.
-      size_t rdata_size = qtype_ == net::dns_protocol::kTypeA ?
-                          net::kIPv4AddressSize : net::kIPv6AddressSize;
-
-      // 12 is the sum of sizes of the compressed name reference, TYPE,
-      // CLASS, TTL and RDLENGTH.
-      size_t answer_size = 12 + rdata_size;
-
-      // Write answer with loopback IP address.
-      reinterpret_cast<dns_protocol::Header*>(buffer)->ancount =
-          base::HostToNet16(1);
-      BigEndianWriter writer(buffer + nbytes, answer_size);
-      writer.WriteU16(kPointerToQueryName);
-      writer.WriteU16(qtype_);
-      writer.WriteU16(net::dns_protocol::kClassIN);
-      writer.WriteU32(kTTL);
-      writer.WriteU16(rdata_size);
-      if (qtype_ == net::dns_protocol::kTypeA) {
-        char kIPv4Loopback[] = { 0x7f, 0, 0, 1 };
-        writer.WriteBytes(kIPv4Loopback, sizeof(kIPv4Loopback));
-      } else {
-        char kIPv6Loopback[] = { 0, 0, 0, 0, 0, 0, 0, 0,
-                                 0, 0, 0, 0, 0, 0, 0, 1 };
-        writer.WriteBytes(kIPv6Loopback, sizeof(kIPv6Loopback));
-      }
-
-      EXPECT_TRUE(response.InitParse(nbytes + answer_size, query));
-      callback_.Run(this, OK, &response);
-    } else {
-      callback_.Run(this, ERR_NAME_NOT_RESOLVED, NULL);
+    switch (result_) {
+      case MockDnsClientRule::EMPTY:
+      case MockDnsClientRule::OK: {
+        std::string qname;
+        DNSDomainFromDot(hostname_, &qname);
+        DnsQuery query(0, qname, qtype_);
+
+        DnsResponse response;
+        char* buffer = response.io_buffer()->data();
+        int nbytes = query.io_buffer()->size();
+        memcpy(buffer, query.io_buffer()->data(), nbytes);
+        dns_protocol::Header* header =
+            reinterpret_cast<dns_protocol::Header*>(buffer);
+        header->flags |= dns_protocol::kFlagResponse;
+
+        if (MockDnsClientRule::OK == result_) {
+          const uint16 kPointerToQueryName =
+              static_cast<uint16>(0xc000 | sizeof(*header));
+
+          const uint32 kTTL = 86400;  // One day.
+
+          // Size of RDATA which is a IPv4 or IPv6 address.
+          size_t rdata_size = qtype_ == net::dns_protocol::kTypeA ?
+                              net::kIPv4AddressSize : net::kIPv6AddressSize;
+
+          // 12 is the sum of sizes of the compressed name reference, TYPE,
+          // CLASS, TTL and RDLENGTH.
+          size_t answer_size = 12 + rdata_size;
+
+          // Write answer with loopback IP address.
+          header->ancount = base::HostToNet16(1);
+          BigEndianWriter writer(buffer + nbytes, answer_size);
+          writer.WriteU16(kPointerToQueryName);
+          writer.WriteU16(qtype_);
+          writer.WriteU16(net::dns_protocol::kClassIN);
+          writer.WriteU32(kTTL);
+          writer.WriteU16(rdata_size);
+          if (qtype_ == net::dns_protocol::kTypeA) {
+            char kIPv4Loopback[] = { 0x7f, 0, 0, 1 };
+            writer.WriteBytes(kIPv4Loopback, sizeof(kIPv4Loopback));
+          } else {
+            char kIPv6Loopback[] = { 0, 0, 0, 0, 0, 0, 0, 0,
+                                     0, 0, 0, 0, 0, 0, 0, 1 };
+            writer.WriteBytes(kIPv6Loopback, sizeof(kIPv6Loopback));
+          }
+          nbytes += answer_size;
+        }
+        EXPECT_TRUE(response.InitParse(nbytes, query));
+        callback_.Run(this, OK, &response);
+      } break;
+      case MockDnsClientRule::FAIL_ASYNC:
+        callback_.Run(this, ERR_NAME_NOT_RESOLVED, NULL);
+        break;
+      default:
+        NOTREACHED();
+        break;
     }
   }
 
+  MockDnsClientRule::Result result_;
   const std::string hostname_;
   const uint16 qtype_;
   DnsTransactionFactory::CallbackType callback_;
@@ -120,7 +143,8 @@ class MockTransaction : public DnsTransaction,
 // A DnsTransactionFactory which creates MockTransaction.
 class MockTransactionFactory : public DnsTransactionFactory {
  public:
-  MockTransactionFactory() {}
+  explicit MockTransactionFactory(const MockDnsClientRuleList& rules)
+      : rules_(rules) {}
   virtual ~MockTransactionFactory() {}
 
   virtual scoped_ptr<DnsTransaction> CreateTransaction(
@@ -129,14 +153,29 @@ class MockTransactionFactory : public DnsTransactionFactory {
       const DnsTransactionFactory::CallbackType& callback,
       const BoundNetLog&) OVERRIDE {
     return scoped_ptr<DnsTransaction>(
-        new MockTransaction(hostname, qtype, callback));
+        new MockTransaction(rules_, hostname, qtype, callback));
+  }
+
+ private:
+  MockDnsClientRuleList rules_;
+};
+
+class MockAddressSorter : public AddressSorter {
+ public:
+  virtual ~MockAddressSorter() {}
+  virtual void Sort(const AddressList& list,
+                    const CallbackType& callback) const OVERRIDE {
+    // Do nothing.
+    callback.Run(true, list);
   }
 };
 
 // MockDnsClient provides MockTransactionFactory.
 class MockDnsClient : public DnsClient {
  public:
-  explicit MockDnsClient(const DnsConfig& config) : config_(config) {}
+  MockDnsClient(const DnsConfig& config,
+                const MockDnsClientRuleList& rules)
+      : config_(config), factory_(rules) {}
   virtual ~MockDnsClient() {}
 
   virtual void SetConfig(const DnsConfig& config) OVERRIDE {
@@ -151,16 +190,22 @@ class MockDnsClient : public DnsClient {
     return config_.IsValid() ? &factory_ : NULL;
   }
 
+  virtual AddressSorter* GetAddressSorter() OVERRIDE {
+    return &address_sorter_;
+  }
+
  private:
   DnsConfig config_;
   MockTransactionFactory factory_;
+  MockAddressSorter address_sorter_;
 };
 
 }  // namespace
 
 // static
-scoped_ptr<DnsClient> CreateMockDnsClient(const DnsConfig& config) {
-  return scoped_ptr<DnsClient>(new MockDnsClient(config));
+scoped_ptr<DnsClient> CreateMockDnsClient(const DnsConfig& config,
+                                          const MockDnsClientRuleList& rules) {
+  return scoped_ptr<DnsClient>(new MockDnsClient(config, rules));
 }
 
 MockDnsConfigService::~MockDnsConfigService() {

net/dns/dns_test_util.h

@@ -5,6 +5,9 @@
 #ifndef NET_DNS_DNS_TEST_UTIL_H_
 #define NET_DNS_DNS_TEST_UTIL_H_
 
+#include <string>
+#include <vector>
+
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "net/dns/dns_config_service.h"
@@ -166,8 +169,25 @@ static const int kT3TTL = 0x00000015;
 static const unsigned kT3RecordCount = arraysize(kT3IpAddresses) + 2;
 
 class DnsClient;
+
+struct MockDnsClientRule {
+  enum Result {
+    FAIL_SYNC,   // Fail synchronously with ERR_NAME_NOT_RESOLVED.
+    FAIL_ASYNC,  // Fail asynchronously with ERR_NAME_NOT_RESOLVED.
+    EMPTY,       // Return an empty response.
+    OK,          // Return a response with loopback address.
+  };
+
+  std::string prefix;
+  uint16 qtype;
+  Result result;
+};
+
+typedef std::vector<MockDnsClientRule> MockDnsClientRuleList;
+
 // Creates mock DnsClient for testing HostResolverImpl.
-scoped_ptr<DnsClient> CreateMockDnsClient(const DnsConfig& config);
+scoped_ptr<DnsClient> CreateMockDnsClient(const DnsConfig& config,
+                                          const MockDnsClientRuleList& rules);
 
 class MockDnsConfigService : public DnsConfigService {
  public:

net/net.gyp

@@ -364,6 +364,10 @@
         'disk_cache/stress_support.h',
         'disk_cache/trace.cc',
         'disk_cache/trace.h',
+        'dns/address_sorter.h',
+        'dns/address_sorter_posix.cc',
+        'dns/address_sorter_posix.h',
+        'dns/address_sorter_win.cc',
         'dns/dns_client.cc',
         'dns/dns_client.h',
         'dns/dns_config_service.cc',
@@ -1195,6 +1199,8 @@
         'disk_cache/entry_unittest.cc',
         'disk_cache/mapped_file_unittest.cc',
         'disk_cache/storage_block_unittest.cc',
+        'dns/address_sorter_posix_unittest.cc',
+        'dns/address_sorter_unittest.cc',
         'dns/dns_config_service_posix_unittest.cc',
         'dns/dns_config_service_unittest.cc',
         'dns/dns_config_service_win_unittest.cc',

net/tools/dns_fuzz_stub/dns_fuzz_stub.cc

@@ -149,7 +149,7 @@ void RunTestCase(uint16 id, std::string& qname, uint16 qtype,
   base::TimeDelta ttl;
   net::DnsResponse::Result result = response.ParseToAddressList(
       &address_list, &ttl);
-  if (result != net::DnsResponse::DNS_SUCCESS) {
+  if (result != net::DnsResponse::DNS_PARSE_OK) {
     LOG(INFO) << "ParseToAddressList failed: " << result;
     return;
   }