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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 #include "net/quic/quic_sent_entropy_manager.h" | |
6 | |
7 #include "base/logging.h" | |
8 #include "net/base/linked_hash_map.h" | |
9 | |
10 using std::make_pair; | |
11 using std::max; | |
12 using std::min; | |
13 | |
14 namespace net { | |
15 | |
16 QuicSentEntropyManager::QuicSentEntropyManager() : map_offset_(1) {} | |
17 | |
18 QuicSentEntropyManager::~QuicSentEntropyManager() {} | |
19 | |
20 QuicPacketEntropyHash QuicSentEntropyManager::GetPacketEntropy( | |
21 QuicPacketSequenceNumber sequence_number) const { | |
22 return packets_entropy_[sequence_number - map_offset_]; | |
23 } | |
24 | |
25 QuicPacketSequenceNumber | |
26 QuicSentEntropyManager::GetLargestPacketWithEntropy() const { | |
27 return map_offset_ + packets_entropy_.size() - 1; | |
28 } | |
29 | |
30 QuicPacketSequenceNumber | |
31 QuicSentEntropyManager::GetSmallestPacketWithEntropy() const { | |
32 return map_offset_; | |
33 } | |
34 | |
35 void QuicSentEntropyManager::UpdateCumulativeEntropy( | |
36 QuicPacketSequenceNumber sequence_number, | |
37 CumulativeEntropy* cumulative) const { | |
38 while (cumulative->sequence_number < sequence_number) { | |
39 ++cumulative->sequence_number; | |
40 cumulative->entropy ^= GetPacketEntropy(cumulative->sequence_number); | |
41 } | |
42 } | |
43 | |
44 void QuicSentEntropyManager::RecordPacketEntropyHash( | |
45 QuicPacketSequenceNumber sequence_number, | |
46 QuicPacketEntropyHash entropy_hash) { | |
47 if (!packets_entropy_.empty()) { | |
48 // Ensure packets always are recorded in order. | |
49 // Every packet's entropy is recorded, even if it's not sent, so there | |
50 // are not sequence number gaps. | |
51 DCHECK_EQ(GetLargestPacketWithEntropy() + 1, sequence_number); | |
52 } | |
53 packets_entropy_.push_back(entropy_hash); | |
54 DVLOG(2) << "Recorded sequence number " << sequence_number | |
55 << " with entropy hash: " << static_cast<int>(entropy_hash); | |
56 } | |
57 | |
58 QuicPacketEntropyHash QuicSentEntropyManager::GetCumulativeEntropy( | |
59 QuicPacketSequenceNumber sequence_number) { | |
60 DCHECK_LE(last_cumulative_entropy_.sequence_number, sequence_number); | |
61 DCHECK_GE(GetLargestPacketWithEntropy(), sequence_number); | |
62 // First the entropy for largest_observed sequence number should be updated. | |
63 UpdateCumulativeEntropy(sequence_number, &last_cumulative_entropy_); | |
64 return last_cumulative_entropy_.entropy; | |
65 } | |
66 | |
67 bool QuicSentEntropyManager::IsValidEntropy( | |
68 QuicPacketSequenceNumber largest_observed, | |
69 const SequenceNumberSet& missing_packets, | |
70 QuicPacketEntropyHash entropy_hash) { | |
71 DCHECK_GE(largest_observed, last_valid_entropy_.sequence_number); | |
72 // Ensure the largest and smallest sequence numbers are in range. | |
73 if (largest_observed > GetLargestPacketWithEntropy()) { | |
74 return false; | |
75 } | |
76 if (!missing_packets.empty() && | |
77 *missing_packets.begin() < GetSmallestPacketWithEntropy()) { | |
78 return false; | |
79 } | |
80 // First the entropy for largest_observed sequence number should be updated. | |
81 UpdateCumulativeEntropy(largest_observed, &last_valid_entropy_); | |
82 | |
83 // Now XOR out all the missing entropies. | |
84 QuicPacketEntropyHash expected_entropy_hash = last_valid_entropy_.entropy; | |
85 for (SequenceNumberSet::const_iterator it = missing_packets.begin(); | |
86 it != missing_packets.end(); ++it) { | |
87 expected_entropy_hash ^= GetPacketEntropy(*it); | |
88 } | |
89 DLOG_IF(WARNING, entropy_hash != expected_entropy_hash) | |
90 << "Invalid entropy hash: " << static_cast<int>(entropy_hash) | |
91 << " expected entropy hash: " << static_cast<int>(expected_entropy_hash); | |
92 return entropy_hash == expected_entropy_hash; | |
93 } | |
94 | |
95 void QuicSentEntropyManager::ClearEntropyBefore( | |
96 QuicPacketSequenceNumber sequence_number) { | |
97 // Don't discard entropy before updating the cumulative entropy used to | |
98 // calculate EntropyHash and IsValidEntropy. | |
99 if (last_cumulative_entropy_.sequence_number < sequence_number) { | |
100 UpdateCumulativeEntropy(sequence_number, &last_cumulative_entropy_); | |
101 } | |
102 if (last_valid_entropy_.sequence_number < sequence_number) { | |
103 UpdateCumulativeEntropy(sequence_number, &last_valid_entropy_); | |
104 } | |
105 while (map_offset_ < sequence_number) { | |
106 packets_entropy_.pop_front(); | |
107 ++map_offset_; | |
108 } | |
109 DVLOG(2) << "Cleared entropy before: " << sequence_number; | |
110 } | |
111 | |
112 } // namespace net | |
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