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 { CumulativeEntropyCumulativeEntropy57 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_ 90