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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.
#ifndef NET_QUIC_QUIC_SENT_ENTROPY_MANAGER_H_
#define NET_QUIC_QUIC_SENT_ENTROPY_MANAGER_H_
#include <deque>
#include "base/macros.h"
#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 {
public:
QuicSentEntropyManager();
virtual ~QuicSentEntropyManager();
// Record |entropy_hash| for sent packet corresponding to |packet_number|.
void RecordPacketEntropyHash(QuicPacketNumber packet_number,
QuicPacketEntropyHash entropy_hash);
// Retrieves the cumulative entropy up to |packet_number|.
// Must always be called with a monotonically increasing |packet_number|.
QuicPacketEntropyHash GetCumulativeEntropy(QuicPacketNumber packet_number);
// Returns true if |entropy_hash| matches the expected sent entropy hash
// up to |largest_observed| removing packet numbers from |missing_packets|.
// Must always be called with a monotonically increasing |largest_observed|.
bool IsValidEntropy(QuicPacketNumber largest_observed,
const PacketNumberQueue& missing_packets,
QuicPacketEntropyHash entropy_hash);
// Removes unnecessary entries before |packet_number|.
void ClearEntropyBefore(QuicPacketNumber packet_number);
private:
friend class test::QuicConnectionPeer;
typedef std::deque<QuicPacketEntropyHash> SentEntropyMap;
struct CumulativeEntropy {
CumulativeEntropy() : packet_number(0), entropy(0) {}
QuicPacketNumber packet_number;
QuicPacketEntropyHash entropy;
};
// Convenience methods to get the largest and smallest packets with entropies.
QuicPacketNumber GetLargestPacketWithEntropy() const;
QuicPacketNumber GetSmallestPacketWithEntropy() const;
// Convenience method to get the entropy hash for |packet_number|.
QuicPacketEntropyHash GetPacketEntropy(QuicPacketNumber packet_number) const;
// Update the cumulative entropy to |packet_number|.
void UpdateCumulativeEntropy(QuicPacketNumber packet_number,
CumulativeEntropy* cumulative) const;
// Maps packet numbers to the sent entropy hash for the packet number.
SentEntropyMap packets_entropy_;
QuicPacketNumber map_offset_;
// Cache the cumulative entropy for IsValidEntropy.
CumulativeEntropy last_valid_entropy_;
// Cache the cumulative entropy for the packet number used by EntropyHash.
CumulativeEntropy last_cumulative_entropy_;
DISALLOW_COPY_AND_ASSIGN(QuicSentEntropyManager);
};
} // namespace net
#endif // NET_QUIC_QUIC_SENT_ENTROPY_MANAGER_H_
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