tcp-option-ts.h

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/*
 * Copyright (c) 2011 Adrian Sai-wah Tam
 *
 * SPDX-License-Identifier: GPL-2.0-only
 *
 * Author: Adrian Sai-wah Tam <adrian.sw.tam@gmail.com>
 */
 
#ifndef TCP_OPTION_TS_H
#define TCP_OPTION_TS_H
 
#include "tcp-option.h"
 
#include "ns3/timer.h"
 
namespace ns3
{
 
/**
 * \ingroup tcp
 *
 * Defines the TCP option of kind 8 (timestamp option) as in \RFC{1323}
 */
 
class TcpOptionTS : public TcpOption
{
  public:
    TcpOptionTS();
    ~TcpOptionTS() override;
 
    /**
     * \brief Get the type ID.
     * \return the object TypeId
     */
    static TypeId GetTypeId();
    TypeId GetInstanceTypeId() const override;
 
    void Print(std::ostream& os) const override;
    void Serialize(Buffer::Iterator start) const override;
    uint32_t Deserialize(Buffer::Iterator start) override;
 
    uint8_t GetKind() const override;
    uint32_t GetSerializedSize() const override;
 
    /**
     * \brief Get the timestamp stored in the Option
     * \return the timestamp
     */
    uint32_t GetTimestamp() const;
    /**
     * \brief Get the timestamp echo stored in the Option
     * \return the timestamp echo
     */
    uint32_t GetEcho() const;
    /**
     * \brief Set the timestamp stored in the Option
     * \param ts the timestamp
     */
    void SetTimestamp(uint32_t ts);
    /**
     * \brief Set the timestamp echo stored in the Option
     * \param ts the timestamp echo
     */
    void SetEcho(uint32_t ts);
 
    /**
     * \brief Return an uint32_t value which represent "now"
     *
     * The value returned is usually used as Timestamp option for the
     * TCP header; when the value will be echoed back, calculating the RTT
     * will be an easy matter.
     *
     * The RFC does not mention any units for this value; following what
     * is implemented in OS, we use milliseconds. Any change to this must be
     * reflected to EstimateRttFromTs.
     *
     * \see EstimateRttFromTs
     * \return The Timestamp value to use
     */
    static uint32_t NowToTsValue();
 
    /**
     * \brief Estimate the Time elapsed from a TS echo value
     *
     * The echoTime should be a value returned from NowToTsValue.
     *
     * \param echoTime Echoed value from other side
     * \see NowToTsValue
     * \return The measured RTT
     */
    static Time ElapsedTimeFromTsValue(uint32_t echoTime);
 
  protected:
    uint32_t m_timestamp; //!< local timestamp
    uint32_t m_echo;      //!< echo timestamp
};
 
} // namespace ns3
 
#endif /* TCP_OPTION_TS */