net/quic/quic_sent_entropy_manager.h

   1 // Copyright 2013 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_SENT_ENTROPY_MANAGER_H_
   9 #define NET_QUIC_QUIC_SENT_ENTROPY_MANAGER_H_
  10
  11 #include <deque>
  12
  13 #include "net/base/linked_hash_map.h"
  14 #include "net/quic/quic_framer.h"
  15 #include "net/quic/quic_protocol.h"
  16
  17 namespace net {
  18
  19 namespace test {
  20 class QuicConnectionPeer;
  21 }  // namespace test
  22
  23 // Records all sent packets by a connection to track the cumulative entropy of
  24 // sent packets.  It is used by the connection to validate an ack
  25 // frame sent by the peer as a preventive measure against the optimistic ack
  26 // attack.
  27 class NET_EXPORT_PRIVATE QuicSentEntropyManager {
  28  public:
  29   QuicSentEntropyManager();
  30   virtual ~QuicSentEntropyManager();
  31
  32   // Record |entropy_hash| for sent packet corresponding to |sequence_number|.
  33   void RecordPacketEntropyHash(QuicPacketSequenceNumber sequence_number,
  34                                QuicPacketEntropyHash entropy_hash);
  35
  36   // Retrieves the cumulative entropy up to |sequence_number|.
  37   // Must always be called with a monotonically increasing |sequence_number|.
  38   QuicPacketEntropyHash GetCumulativeEntropy(
  39       QuicPacketSequenceNumber sequence_number);
  40
  41   // Returns true if |entropy_hash| matches the expected sent entropy hash
  42   // up to |largest_observed| removing sequence numbers from |missing_packets|.
  43   // Must always be called with a monotonically increasing |largest_observed|.
  44   bool IsValidEntropy(QuicPacketSequenceNumber largest_observed,
  45                       const SequenceNumberSet& missing_packets,
  46                       QuicPacketEntropyHash entropy_hash);
  47
  48   // Removes unnecessary entries before |sequence_number|.
  49   void ClearEntropyBefore(QuicPacketSequenceNumber sequence_number);
  50
  51  private:
  52   friend class test::QuicConnectionPeer;
  53
  54   typedef std::deque<QuicPacketEntropyHash> SentEntropyMap;
  55
  56   struct CumulativeEntropy {
  57     CumulativeEntropy() : sequence_number(0), entropy(0) {}
  58
  59     QuicPacketSequenceNumber sequence_number;
  60     QuicPacketEntropyHash entropy;
  61   };
  62
  63   // Convenience methods to get the largest and smallest packets with entropies.
  64   QuicPacketSequenceNumber GetLargestPacketWithEntropy() const;
  65   QuicPacketSequenceNumber GetSmallestPacketWithEntropy() const;
  66   // Convenience method to get the entropy hash for |sequence_number|.
  67   QuicPacketEntropyHash GetPacketEntropy(
  68       QuicPacketSequenceNumber sequence_number) const;
  69
  70   // Update the cumulative entropy to |sequence_number|.
  71   void UpdateCumulativeEntropy(QuicPacketSequenceNumber sequence_number,
  72                                CumulativeEntropy* cumulative) const;
  73
  74   // Maps sequence numbers to the sent entropy hash for the sequence number.
  75   SentEntropyMap packets_entropy_;
  76   QuicPacketSequenceNumber map_offset_;
  77
  78   // Cache the cumulative entropy for IsValidEntropy.
  79   CumulativeEntropy last_valid_entropy_;
  80
  81   // Cache the cumulative entropy for the sequence number used by EntropyHash.
  82   CumulativeEntropy last_cumulative_entropy_;
  83
  84   DISALLOW_COPY_AND_ASSIGN(QuicSentEntropyManager);
  85 };
  86
  87 }  // namespace net
  88
  89 #endif  // NET_QUIC_QUIC_SENT_ENTROPY_MANAGER_H_