net/dns/dns_session.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef NET_DNS_DNS_SESSION_H_
   6 #define NET_DNS_DNS_SESSION_H_
   7
   8 #include <vector>
   9
  10 #include "base/memory/ref_counted.h"
  11 #include "base/memory/scoped_ptr.h"
  12 #include "base/time.h"
  13 #include "net/base/net_export.h"
  14 #include "net/base/rand_callback.h"
  15 #include "net/dns/dns_config_service.h"
  16 #include "net/dns/dns_socket_pool.h"
  17
  18 namespace net {
  19
  20 class ClientSocketFactory;
  21 class DatagramClientSocket;
  22 class NetLog;
  23 class StreamSocket;
  24
  25 // Session parameters and state shared between DNS transactions.
  26 // Ref-counted so that DnsClient::Request can keep working in absence of
  27 // DnsClient. A DnsSession must be recreated when DnsConfig changes.
  28 class NET_EXPORT_PRIVATE DnsSession
  29     : NON_EXPORTED_BASE(public base::RefCounted<DnsSession>) {
  30  public:
  31   typedef base::Callback<int()> RandCallback;
  32
  33   class NET_EXPORT_PRIVATE SocketLease {
  34    public:
  35     SocketLease(scoped_refptr<DnsSession> session,
  36                 unsigned server_index,
  37                 scoped_ptr<DatagramClientSocket> socket);
  38     ~SocketLease();
  39
  40     unsigned server_index() const { return server_index_; }
  41
  42     DatagramClientSocket* socket() { return socket_.get(); }
  43
  44    private:
  45     scoped_refptr<DnsSession> session_;
  46     unsigned server_index_;
  47     scoped_ptr<DatagramClientSocket> socket_;
  48
  49     DISALLOW_COPY_AND_ASSIGN(SocketLease);
  50   };
  51
  52   DnsSession(const DnsConfig& config,
  53              scoped_ptr<DnsSocketPool> socket_pool,
  54              const RandIntCallback& rand_int_callback,
  55              NetLog* net_log);
  56
  57   const DnsConfig& config() const { return config_; }
  58   NetLog* net_log() const { return net_log_; }
  59
  60   // Return the next random query ID.
  61   int NextQueryId() const;
  62
  63   // Return the index of the first configured server to use on first attempt.
  64   int NextFirstServerIndex();
  65
  66   // Return the timeout for the next query.
  67   base::TimeDelta NextTimeout(int attempt);
  68
  69   // Allocate a socket, already connected to the server address.
  70   // When the SocketLease is destroyed, the socket will be freed.
  71   scoped_ptr<SocketLease> AllocateSocket(unsigned server_index,
  72                                          const NetLog::Source& source);
  73
  74   // Creates a StreamSocket from the factory for a transaction over TCP. These
  75   // sockets are not pooled.
  76   scoped_ptr<StreamSocket> CreateTCPSocket(unsigned server_index,
  77                                            const NetLog::Source& source);
  78
  79  private:
  80   friend class base::RefCounted<DnsSession>;
  81   ~DnsSession();
  82
  83   // Release a socket.
  84   void FreeSocket(unsigned server_index,
  85                   scoped_ptr<DatagramClientSocket> socket);
  86
  87   const DnsConfig config_;
  88   scoped_ptr<DnsSocketPool> socket_pool_;
  89   RandCallback rand_callback_;
  90   NetLog* net_log_;
  91
  92   // Current index into |config_.nameservers| to begin resolution with.
  93   int server_index_;
  94
  95   // TODO(szym): Add current RTT estimate.
  96   // TODO(szym): Add TCP connection pool to support DNS over TCP.
  97
  98   DISALLOW_COPY_AND_ASSIGN(DnsSession);
  99 };
 100
 101 }  // namespace net
 102
 103 #endif  // NET_DNS_DNS_SESSION_H_