tcp-rto-test.cc

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/*
 * Copyright (c) 2015 Natale Patriciello <natale.patriciello@gmail.com>
 *
 * SPDX-License-Identifier: GPL-2.0-only
 *
 */
 
#include "tcp-error-model.h"
#include "tcp-general-test.h"
 
#include "ns3/log.h"
#include "ns3/node.h"
#include "ns3/rtt-estimator.h"
#include "ns3/simple-channel.h"
 
NS_LOG_COMPONENT_DEFINE("TcpRtoTest");
 
using namespace ns3;
 
/**
 * \ingroup internet-test
 *
 * \brief Testing the moments after an RTO expiration
 *
 * The scope of this test is to be sure that, after an RTO expiration,
 * the TCP implementation set the correct state in the ACK state machine,
 * and marks the lost segment as lost; then, after the retransmission, the
 * state is fully recovered. This is the base check, where only one segment
 * (the first) is lost and retransmitted.
 *
 */
class TcpRtoTest : public TcpGeneralTest
{
  public:
    /**
     * \brief Constructor.
     * \param congControl Congestion control type.
     * \param msg Test description.
     */
    TcpRtoTest(const TypeId& congControl, const std::string& msg);
 
  protected:
    Ptr<TcpSocketMsgBase> CreateSenderSocket(Ptr<Node> node) override;
    void AfterRTOExpired(const Ptr<const TcpSocketState> tcb, SocketWho who) override;
    void RcvAck(const Ptr<const TcpSocketState> tcb, const TcpHeader& h, SocketWho who) override;
    void ProcessedAck(const Ptr<const TcpSocketState> tcb,
                      const TcpHeader& h,
                      SocketWho who) override;
    void FinalChecks() override;
    void ConfigureProperties() override;
    void ConfigureEnvironment() override;
 
  private:
    bool m_afterRTOExpired; //!< True if RTO is expired.
    bool m_segmentReceived; //!< True if segments have been received.
};
 
TcpRtoTest::TcpRtoTest(const TypeId& congControl, const std::string& desc)
    : TcpGeneralTest(desc),
      m_afterRTOExpired(false),
      m_segmentReceived(false)
{
    m_congControlTypeId = congControl;
}
 
void
TcpRtoTest::ConfigureEnvironment()
{
    TcpGeneralTest::ConfigureEnvironment();
    SetAppPktCount(100);
}
 
void
TcpRtoTest::ConfigureProperties()
{
    TcpGeneralTest::ConfigureProperties();
    SetInitialSsThresh(SENDER, 0);
}
 
Ptr<TcpSocketMsgBase>
TcpRtoTest::CreateSenderSocket(Ptr<Node> node)
{
    // Get a really low RTO, and let them fire as soon as possible since
    // we are interested only in what happen after it expires
    Ptr<TcpSocketMsgBase> socket = TcpGeneralTest::CreateSenderSocket(node);
    socket->SetAttribute("MinRto", TimeValue(Seconds(0.5)));
 
    return socket;
}
 
void
TcpRtoTest::AfterRTOExpired(const Ptr<const TcpSocketState> tcb, SocketWho who)
{
    // In this test, the RTO fires for the first segment (and no more).
    // This function is called after the management of the RTO expiration,
    // and because of this we must check all the involved variables.
    NS_TEST_ASSERT_MSG_EQ(m_afterRTOExpired, false, "Second RTO expired");
    NS_TEST_ASSERT_MSG_EQ(tcb->m_congState.Get(),
                          TcpSocketState::CA_LOSS,
                          "Ack state machine not in LOSS state after a loss");
 
    m_afterRTOExpired = true;
}
 
void
TcpRtoTest::RcvAck(const Ptr<const TcpSocketState> tcb, const TcpHeader& h, SocketWho who)
{
    // Called after the first ack is received (the lost segment has been
    // successfully retransmitted. We must check on the sender that variables
    // are in the same state as they where after AfterRTOExpired if it is the first
    // ACK after the loss; in every other case, all must be OPEN and the counter
    // set to 0.
 
    if (m_afterRTOExpired && who == SENDER)
    {
        NS_TEST_ASSERT_MSG_EQ(tcb->m_congState.Get(),
                              TcpSocketState::CA_LOSS,
                              "Ack state machine not in LOSS state after a loss");
    }
    else
    {
        NS_TEST_ASSERT_MSG_EQ(tcb->m_congState.Get(),
                              TcpSocketState::CA_OPEN,
                              "Ack state machine not in OPEN state after recovering "
                              "from loss");
    }
}
 
void
TcpRtoTest::ProcessedAck(const Ptr<const TcpSocketState> tcb, const TcpHeader& h, SocketWho who)
{
    // Called after the ACK processing. Every time we should be in OPEN state,
    // without any packet lost or marked as retransmitted, in both the sockets
 
    NS_TEST_ASSERT_MSG_EQ(tcb->m_congState.Get(),
                          TcpSocketState::CA_OPEN,
                          "Ack state machine not in OPEN state after recovering "
                          "from loss");
 
    if (who == SENDER)
    {
        m_afterRTOExpired = false;
        m_segmentReceived = true;
    }
}
 
void
TcpRtoTest::FinalChecks()
{
    // At least one time we should process an ACK; otherwise, the segment
    // has not been retransmitted, and this is bad
 
    NS_TEST_ASSERT_MSG_EQ(m_segmentReceived, true, "Retransmission has not been done");
}
 
/**
 * \ingroup internet-test
 *
 * \brief Testing the ssthresh behavior after the RTO expires
 *
 * The scope of this test is to be sure that, after an RTO expiration,
 * the TCP implementation sets the correct ssthresh value
 *
 */
class TcpSsThreshRtoTest : public TcpGeneralTest
{
  public:
    /**
     * \brief Constructor.
     * \param congControl congestion control type
     * \param seqToDrop sequence number to drop
     * \param minRto minimum RTO
     * \param msg test description
     */
    TcpSsThreshRtoTest(const TypeId& congControl,
                       uint32_t seqToDrop,
                       Time minRto,
                       const std::string& msg);
 
  protected:
    Ptr<TcpSocketMsgBase> CreateSenderSocket(Ptr<Node> node) override;
    Ptr<ErrorModel> CreateReceiverErrorModel() override;
    void BytesInFlightTrace(uint32_t oldValue, uint32_t newValue) override;
    void SsThreshTrace(uint32_t oldValue, uint32_t newValue) override;
    void BeforeRTOExpired(const Ptr<const TcpSocketState> tcb, SocketWho who) override;
    void AfterRTOExpired(const Ptr<const TcpSocketState> tcb, SocketWho who) override;
 
    void ConfigureEnvironment() override;
 
    /**
     * \brief Called when a packet has been dropped.
     * \param ipH IPv4 header.
     * \param tcpH TCP header.
     * \param p The packet.
     */
    void PktDropped(const Ipv4Header& ipH, const TcpHeader& tcpH, Ptr<const Packet> p);
 
  private:
    uint32_t m_bytesInFlight; //!< Store the number of bytes in flight
    uint32_t
        m_bytesInFlightBeforeRto; //!< Store the number of bytes in flight before the RTO expiration
    uint32_t m_ssThreshSocket;    //!< the ssThresh as computed by the socket
    uint32_t m_seqToDrop;         //!< the sequence number to drop
    Time m_minRtoTime;            //!< the minimum RTO time
};
 
TcpSsThreshRtoTest::TcpSsThreshRtoTest(const TypeId& congControl,
                                       uint32_t seqToDrop,
                                       Time minRto,
                                       const std::string& desc)
    : TcpGeneralTest(desc),
      m_seqToDrop(seqToDrop),
      m_minRtoTime(minRto)
{
    m_congControlTypeId = congControl;
}
 
void
TcpSsThreshRtoTest::ConfigureEnvironment()
{
    TcpGeneralTest::ConfigureEnvironment();
    SetAppPktCount(100);
    SetAppPktInterval(MicroSeconds(100));
    SetPropagationDelay(MilliSeconds(1));
}
 
Ptr<TcpSocketMsgBase>
TcpSsThreshRtoTest::CreateSenderSocket(Ptr<Node> node)
{
    Ptr<TcpSocketMsgBase> socket = TcpGeneralTest::CreateSenderSocket(node);
    socket->SetAttribute("MinRto", TimeValue(m_minRtoTime));
    NS_LOG_DEBUG("TcpSsThreshRtoTest create sender socket");
 
    return socket;
}
 
Ptr<ErrorModel>
TcpSsThreshRtoTest::CreateReceiverErrorModel()
{
    NS_LOG_DEBUG("TcpSsThreshRtoTest create errorModel");
 
    Ptr<TcpSeqErrorModel> errorModel = CreateObject<TcpSeqErrorModel>();
 
    for (uint32_t i = 0; i < 3; ++i)
    {
        errorModel->AddSeqToKill(SequenceNumber32(m_seqToDrop));
    }
 
    errorModel->SetDropCallback(MakeCallback(&TcpSsThreshRtoTest::PktDropped, this));
 
    return errorModel;
}
 
void
TcpSsThreshRtoTest::PktDropped(const Ipv4Header& ipH, const TcpHeader& tcpH, Ptr<const Packet> p)
{
    NS_LOG_DEBUG("DROPPED! " << tcpH);
}
 
void
TcpSsThreshRtoTest::BytesInFlightTrace(uint32_t oldValue, uint32_t newValue)
{
    NS_LOG_DEBUG("Socket BytesInFlight=" << newValue);
    m_bytesInFlight = newValue;
}
 
void
TcpSsThreshRtoTest::SsThreshTrace(uint32_t oldValue, uint32_t newValue)
{
    NS_LOG_DEBUG("Socket ssThresh=" << newValue);
    m_ssThreshSocket = newValue;
}
 
void
TcpSsThreshRtoTest::BeforeRTOExpired(const Ptr<const TcpSocketState> tcb, SocketWho who)
{
    NS_LOG_DEBUG("Before RTO for connection " << who);
 
    // Get the bytesInFlight value before the expiration of the RTO
 
    if (who == SENDER)
    {
        m_bytesInFlightBeforeRto = m_bytesInFlight;
        NS_LOG_DEBUG("BytesInFlight before RTO Expired " << m_bytesInFlight);
    }
}
 
void
TcpSsThreshRtoTest::AfterRTOExpired(const Ptr<const TcpSocketState> tcb, SocketWho who)
{
    NS_LOG_DEBUG("After RTO for " << who);
    Ptr<TcpSocketMsgBase> senderSocket = GetSenderSocket();
 
    // compute the ssThresh according to RFC 5681, using the
    uint32_t ssThresh = std::max(m_bytesInFlightBeforeRto / 2, 2 * tcb->m_segmentSize);
 
    NS_LOG_DEBUG("ssThresh " << ssThresh << " m_ssThreshSocket " << m_ssThreshSocket);
 
    NS_TEST_ASSERT_MSG_EQ(ssThresh, m_ssThreshSocket, "Slow Start Threshold is incorrect");
}
 
/**
 * \ingroup internet-test
 *
 * \brief Testing the timing of RTO
 *
 * Checking if RTO is doubled ONLY after a retransmission.
 */
class TcpTimeRtoTest : public TcpGeneralTest
{
  public:
    /**
     * \brief Constructor.
     * \param congControl Congestion control type.
     * \param msg Test description.
     */
    TcpTimeRtoTest(const TypeId& congControl, const std::string& msg);
 
  protected:
    Ptr<TcpSocketMsgBase> CreateSenderSocket(Ptr<Node> node) override;
    Ptr<ErrorModel> CreateReceiverErrorModel() override;
    void ErrorClose(SocketWho who) override;
    void AfterRTOExpired(const Ptr<const TcpSocketState> tcb, SocketWho who) override;
    void Tx(const Ptr<const Packet> p, const TcpHeader& h, SocketWho who) override;
    void FinalChecks() override;
 
    void ConfigureEnvironment() override;
 
    /**
     * \brief Called when a packet has been dropped.
     * \param ipH IPv4 header.
     * \param tcpH TCP header.
     * \param p The packet.
     */
    void PktDropped(const Ipv4Header& ipH, const TcpHeader& tcpH, Ptr<const Packet> p);
 
  private:
    uint32_t m_senderSentSegments; //!< Number of segments sent.
    Time m_previousRTO;            //!< Previous RTO.
    bool m_closed;                 //!< True if the connection is closed.
};
 
TcpTimeRtoTest::TcpTimeRtoTest(const TypeId& congControl, const std::string& desc)
    : TcpGeneralTest(desc),
      m_senderSentSegments(0),
      m_closed(false)
{
    m_congControlTypeId = congControl;
}
 
void
TcpTimeRtoTest::ConfigureEnvironment()
{
    TcpGeneralTest::ConfigureEnvironment();
    SetAppPktCount(100);
}
 
Ptr<TcpSocketMsgBase>
TcpTimeRtoTest::CreateSenderSocket(Ptr<Node> node)
{
    Ptr<TcpSocketMsgBase> s = TcpGeneralTest::CreateSenderSocket(node);
    s->SetAttribute("DataRetries", UintegerValue(6));
 
    return s;
}
 
Ptr<ErrorModel>
TcpTimeRtoTest::CreateReceiverErrorModel()
{
    Ptr<TcpSeqErrorModel> errorModel = CreateObject<TcpSeqErrorModel>();
 
    // Drop packet for 7 times. At the 7th, the connection should be dropped.
    for (uint32_t i = 0; i < 7; ++i)
    {
        errorModel->AddSeqToKill(SequenceNumber32(1));
    }
 
    errorModel->SetDropCallback(MakeCallback(&TcpTimeRtoTest::PktDropped, this));
 
    return errorModel;
}
 
void
TcpTimeRtoTest::Tx(const Ptr<const Packet> p, const TcpHeader& h, SocketWho who)
{
    NS_LOG_FUNCTION(this << p << h << who);
 
    if (who == SENDER)
    {
        ++m_senderSentSegments;
        NS_LOG_INFO("Measured RTO:" << GetRto(SENDER).GetSeconds());
 
        if (h.GetFlags() & TcpHeader::SYN)
        {
            NS_TEST_ASSERT_MSG_EQ(m_senderSentSegments,
                                  1,
                                  "Number of segments sent is different than 1");
 
            Time s_rto = GetRto(SENDER);
            NS_TEST_ASSERT_MSG_EQ(s_rto,
                                  GetConnTimeout(SENDER),
                                  "SYN packet sent without respecting "
                                  "ConnTimeout attribute");
        }
        else
        {
            NS_LOG_INFO("TX: " << h << m_senderSentSegments);
 
            NS_TEST_ASSERT_MSG_EQ(h.GetSequenceNumber().GetValue(),
                                  1,
                                  "First packet was not correctly sent");
 
            // Remember, from RFC:
            // m_rto = Max (m_rtt->GetEstimate () +
            //              Max (m_clockGranularity, m_rtt->GetVariation ()*4), m_minRto);
 
            if (m_senderSentSegments == 2)
            { // ACK of SYN-ACK, rto set for the first time, since now we have
                // an estimation of RTT
 
                Ptr<RttEstimator> rttEstimator = GetRttEstimator(SENDER);
                Time clockGranularity = GetClockGranularity(SENDER);
                m_previousRTO = rttEstimator->GetEstimate();
 
                if (clockGranularity > rttEstimator->GetVariation() * 4)
                {
                    m_previousRTO += clockGranularity;
                }
                else
                {
                    m_previousRTO += rttEstimator->GetVariation() * 4;
                }
 
                m_previousRTO = Max(m_previousRTO, GetMinRto(SENDER));
 
                NS_TEST_ASSERT_MSG_EQ_TOL(GetRto(SENDER),
                                          m_previousRTO,
                                          Seconds(0.01),
                                          "RTO value differs from calculation");
            }
            else if (m_senderSentSegments == 3)
            { // First data packet. RTO should be the same as before
 
                NS_TEST_ASSERT_MSG_EQ_TOL(GetRto(SENDER),
                                          m_previousRTO,
                                          Seconds(0.01),
                                          "RTO value has changed unexpectedly");
            }
        }
    }
    else if (who == RECEIVER)
    {
    }
}
 
void
TcpTimeRtoTest::ErrorClose(SocketWho who)
{
    m_closed = true;
}
 
void
TcpTimeRtoTest::AfterRTOExpired(const Ptr<const TcpSocketState> tcb, SocketWho who)
{
    NS_TEST_ASSERT_MSG_EQ(who, SENDER, "RTO in Receiver. That's unexpected");
 
    Time actualRto = GetRto(SENDER);
 
    if (actualRto < Seconds(60))
    {
        NS_TEST_ASSERT_MSG_EQ_TOL(actualRto,
                                  m_previousRTO + m_previousRTO,
                                  Seconds(0.01),
                                  "RTO has not doubled after an expiration");
        m_previousRTO += m_previousRTO;
    }
    else
    {
        NS_TEST_ASSERT_MSG_EQ(actualRto, Seconds(60), "RTO goes beyond 60 second limit");
    }
}
 
void
TcpTimeRtoTest::PktDropped(const Ipv4Header& ipH, const TcpHeader& tcpH, Ptr<const Packet> p)
{
    NS_LOG_INFO("DROPPED! " << tcpH);
}
 
void
TcpTimeRtoTest::FinalChecks()
{
    NS_TEST_ASSERT_MSG_EQ(m_closed,
                          true,
                          "Socket has not been closed after retrying data retransmissions");
}
 
/**
 * \ingroup internet-test
 *
 * \brief TCP RTO TestSuite
 */
class TcpRtoTestSuite : public TestSuite
{
  public:
    TcpRtoTestSuite()
        : TestSuite("tcp-rto-test", Type::UNIT)
    {
        std::list<TypeId> types = {
            TcpNewReno::GetTypeId(),
        };
 
        for (const auto& t : types)
        {
            AddTestCase(new TcpRtoTest(t, t.GetName() + " RTO retransmit testing"),
                        TestCase::Duration::QUICK);
 
            constexpr uint32_t seqToDrop = 25001;
 
            // With RTO of 0.5 seconds, BytesInFlight winds down to zero before RTO
            AddTestCase(new TcpSsThreshRtoTest(t,
                                               seqToDrop,
                                               Seconds(0.5),
                                               t.GetName() + " RTO ssthresh testing, set to 2*MSL"),
                        TestCase::Duration::QUICK);
 
            // With RTO of 0.005 seconds, FlightSize/2 > 2*SMSS
            AddTestCase(new TcpSsThreshRtoTest(
                            t,
                            seqToDrop,
                            Seconds(0.005),
                            t.GetName() + " RTO ssthresh testing, set to half of BytesInFlight"),
                        TestCase::Duration::QUICK);
 
            AddTestCase(new TcpTimeRtoTest(t, t.GetName() + " RTO timing testing"),
                        TestCase::Duration::QUICK);
        }
    }
};
 
static TcpRtoTestSuite g_TcpRtoTestSuite; //!< Static variable for test initialization