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

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;
+
+// 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;
+
+// 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:
+  explicit AddressSorterPosix(ClientSocketFactory* socket_factory);
+  virtual ~AddressSorterPosix();
+
+  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_