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// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// Manages the packet entropy calculation for both sent and received packets
// for a connection.
#include <deque>
#include "net/base/linked_hash_map.h"
#include "net/quic/quic_framer.h"
#include "net/quic/quic_protocol.h"
namespace net {
namespace test {
class QuicConnectionPeer;
} // namespace test
// Records all sent packets by a connection to track the cumulative entropy of
// sent packets. It is used by the connection to validate an ack
// frame sent by the peer as a preventive measure against the optimistic ack
// attack.
class NET_EXPORT_PRIVATE QuicSentEntropyManager {
virtual ~QuicSentEntropyManager();
// Record |entropy_hash| for sent packet corresponding to |sequence_number|.
void RecordPacketEntropyHash(QuicPacketSequenceNumber sequence_number,
QuicPacketEntropyHash entropy_hash);
// Retrieves the cumulative entropy up to |sequence_number|.
// Must always be called with a monotonically increasing |sequence_number|.
QuicPacketEntropyHash GetCumulativeEntropy(
QuicPacketSequenceNumber sequence_number);
// Returns true if |entropy_hash| matches the expected sent entropy hash
// up to |largest_observed| removing sequence numbers from |missing_packets|.
// Must always be called with a monotonically increasing |largest_observed|.
bool IsValidEntropy(QuicPacketSequenceNumber largest_observed,
const SequenceNumberSet& missing_packets,
QuicPacketEntropyHash entropy_hash);
// Removes unnecessary entries before |sequence_number|.
void ClearEntropyBefore(QuicPacketSequenceNumber sequence_number);
friend class test::QuicConnectionPeer;
typedef std::deque<QuicPacketEntropyHash> SentEntropyMap;
struct CumulativeEntropy {
CumulativeEntropy() : sequence_number(0), entropy(0) {}
QuicPacketSequenceNumber sequence_number;
QuicPacketEntropyHash entropy;
// Convenience methods to get the largest and smallest packets with entropies.
QuicPacketSequenceNumber GetLargestPacketWithEntropy() const;
QuicPacketSequenceNumber GetSmallestPacketWithEntropy() const;
// Convenience method to get the entropy hash for |sequence_number|.
QuicPacketEntropyHash GetPacketEntropy(
QuicPacketSequenceNumber sequence_number) const;
// Update the cumulative entropy to |sequence_number|.
void UpdateCumulativeEntropy(QuicPacketSequenceNumber sequence_number,
CumulativeEntropy* cumulative) const;
// Maps sequence numbers to the sent entropy hash for the sequence number.
SentEntropyMap packets_entropy_;
QuicPacketSequenceNumber map_offset_;
// Cache the cumulative entropy for IsValidEntropy.
CumulativeEntropy last_valid_entropy_;
// Cache the cumulative entropy for the sequence number used by EntropyHash.
CumulativeEntropy last_cumulative_entropy_;
} // namespace net