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      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 "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 packets by a connection to track the cumulative entropy of
     18 // sent packets.  It is used by the connection to validate an ack
     19 // frame sent by the peer as a preventive measure against the optimistic ack
     20 // attack.
     21 class NET_EXPORT_PRIVATE QuicSentEntropyManager {
     22  public:
     23   QuicSentEntropyManager();
     24   virtual ~QuicSentEntropyManager();
     25 
     26   // Record |entropy_hash| for sent packet corresponding to |sequence_number|.
     27   void RecordPacketEntropyHash(QuicPacketSequenceNumber sequence_number,
     28                                QuicPacketEntropyHash entropy_hash);
     29 
     30   QuicPacketEntropyHash EntropyHash(
     31       QuicPacketSequenceNumber sequence_number) const;
     32 
     33   // Returns true if |entropy_hash| matches the expected sent entropy hash
     34   // up to |sequence_number| removing sequence numbers from |missing_packets|.
     35   bool IsValidEntropy(QuicPacketSequenceNumber sequence_number,
     36                       const SequenceNumberSet& missing_packets,
     37                       QuicPacketEntropyHash entropy_hash) const;
     38 
     39   // Removes not required entries from |packets_entropy_| before
     40   // |sequence_number|.
     41   void ClearEntropyBefore(QuicPacketSequenceNumber sequence_number);
     42 
     43  private:
     44   typedef linked_hash_map<QuicPacketSequenceNumber,
     45                           std::pair<QuicPacketEntropyHash,
     46                                QuicPacketEntropyHash> > SentEntropyMap;
     47 
     48   // Linked hash map from sequence numbers to the sent entropy hash up to the
     49   // sequence number in the key.
     50   SentEntropyMap packets_entropy_;
     51 
     52   // Cumulative hash of entropy of all sent packets.
     53   QuicPacketEntropyHash packets_entropy_hash_;
     54 };
     55 
     56 }  // namespace net
     57 
     58 #endif  // NET_QUIC_QUIC_SENT_ENTROPY_MANAGER_H_
     59