net/quic/quic_packet_entropy_manager.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 // Manages the packet entropy calculation for both sent and received packets
   6 // for a connection.
   7
   8 #ifndef NET_QUIC_QUIC_PACKET_ENTROPY_MANAGER_H_
   9 #define NET_QUIC_QUIC_PACKET_ENTROPY_MANAGER_H_
  10
  11 #include "net/base/linked_hash_map.h"
  12 #include "net/quic/quic_framer.h"
  13 #include "net/quic/quic_protocol.h"
  14
  15 namespace net {
  16
  17 // Records all sent and received packets by a connection to track the cumulative
  18 // entropy of both sent and received packets separately. It is used by the
  19 // connection to validate an ack frame sent by the peer as a preventive measure
  20 // against the optimistic ack attack. Also, called by the framer when it
  21 // truncates an ack frame to get the correct entropy value for the ack frame
  22 // being serialized.
  23 class NET_EXPORT_PRIVATE QuicPacketEntropyManager :
  24     public QuicReceivedEntropyHashCalculatorInterface {
  25  public:
  26   QuicPacketEntropyManager();
  27   virtual ~QuicPacketEntropyManager();
  28
  29   // Record the received entropy hash against |sequence_number|.
  30   void RecordReceivedPacketEntropyHash(QuicPacketSequenceNumber sequence_number,
  31                                        QuicPacketEntropyHash entropy_hash);
  32
  33   // Record |entropy_hash| for sent packet corresponding to |sequence_number|.
  34   void RecordSentPacketEntropyHash(QuicPacketSequenceNumber sequence_number,
  35                                    QuicPacketEntropyHash entropy_hash);
  36
  37   // QuicReceivedEntropyHashCalculatorInterface
  38   // Called by QuicFramer, when the outgoing ack gets truncated, to recalculate
  39   // the received entropy hash for the truncated ack frame.
  40   virtual QuicPacketEntropyHash ReceivedEntropyHash(
  41       QuicPacketSequenceNumber sequence_number) const OVERRIDE;
  42
  43   QuicPacketEntropyHash SentEntropyHash(
  44       QuicPacketSequenceNumber sequence_number) const;
  45
  46   // Recalculate the received entropy hash since we had some missing packets
  47   // which the sender won't retransmit again and has sent us the |entropy_hash|
  48   // for packets up to, but not including, |sequence_number|.
  49   void RecalculateReceivedEntropyHash(
  50       QuicPacketSequenceNumber sequence_number,
  51       QuicPacketEntropyHash entropy_hash);
  52
  53   // Returns true if |entropy_hash| matches the expected sent entropy hash
  54   // up to |sequence_number| removing sequence numbers from |missing_packets|.
  55   bool IsValidEntropy(QuicPacketSequenceNumber sequence_number,
  56                       const SequenceNumberSet& missing_packets,
  57                       QuicPacketEntropyHash entropy_hash) const;
  58
  59   // Removes not required entries from |sent_packets_entropy_| before
  60   // |sequence_number|.
  61   void ClearSentEntropyBefore(QuicPacketSequenceNumber sequence_number);
  62
  63   // Removes not required entries from |received_packets_entropy_| before
  64   // |sequence_number|.
  65   void ClearReceivedEntropyBefore(QuicPacketSequenceNumber sequence_number);
  66
  67   QuicPacketEntropyHash sent_packets_entropy_hash() const {
  68     return sent_packets_entropy_hash_;
  69   }
  70
  71   QuicPacketEntropyHash received_packets_entropy_hash() const {
  72     return received_packets_entropy_hash_;
  73   }
  74
  75  private:
  76   typedef linked_hash_map<QuicPacketSequenceNumber,
  77                           std::pair<QuicPacketEntropyHash,
  78                                QuicPacketEntropyHash> > SentEntropyMap;
  79   typedef std::map<QuicPacketSequenceNumber,
  80                    QuicPacketEntropyHash> ReceivedEntropyMap;
  81
  82   // TODO(satyamshekhar): Can be optimized using an interval set like data
  83   // structure.
  84   // Set of received sequence numbers that had the received entropy flag set.
  85   ReceivedEntropyMap received_packets_entropy_;
  86
  87   // Linked hash map from sequence numbers to the sent entropy hash up to the
  88   // sequence number in the key.
  89   SentEntropyMap sent_packets_entropy_;
  90
  91   // Cumulative hash of entropy of all sent packets.
  92   QuicPacketEntropyHash sent_packets_entropy_hash_;
  93
  94   // Cumulative hash of entropy of all received packets.
  95   QuicPacketEntropyHash received_packets_entropy_hash_;
  96
  97   QuicPacketSequenceNumber largest_received_sequence_number_;
  98 };
  99
 100 }  // namespace net
 101
 102 #endif  // NET_QUIC_QUIC_PACKET_ENTROPY_MANAGER_H_