tcp-fast-retr-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/simple-channel.h"
#include "ns3/tcp-westwood-plus.h"
 
using namespace ns3;
 
NS_LOG_COMPONENT_DEFINE("TcpFastRetrTest");
 
/**
 * \ingroup internet-test
 *
 * \brief Test the fast retransmission
 *
 * Checking what is happening is not so easy, so there are a lot of variables
 * which helps to keep track on what is happening.
 * The idea is following sequence and ack numbers which are exchanged,
 * testing if they are the same as the implementation transmits.
 */
class TcpFastRetrTest : public TcpGeneralTest
{
  public:
    /**
     * \brief Constructor
     * \param congControl Type of congestion control.
     * \param seqToKill Sequence number of the packet to drop.
     * \param msg Test message.
     */
    TcpFastRetrTest(TypeId congControl, uint32_t seqToKill, const std::string& msg);
 
    Ptr<ErrorModel> CreateSenderErrorModel() override;
    Ptr<ErrorModel> CreateReceiverErrorModel() override;
 
    Ptr<TcpSocketMsgBase> CreateSenderSocket(Ptr<Node> node) override;
 
  protected:
    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 CongStateTrace(const TcpSocketState::TcpCongState_t oldValue,
                        const TcpSocketState::TcpCongState_t newValue) override;
 
    void Tx(const Ptr<const Packet> p, const TcpHeader& h, SocketWho who) override;
    void Rx(const Ptr<const Packet> p, const TcpHeader& h, SocketWho who) override;
 
    void AfterRTOExpired(const Ptr<const TcpSocketState> tcb, SocketWho who) override;
 
    /**
     * \brief Check if the packet being dropped is the right one.
     * \param ipH IPv4 header.
     * \param tcpH TCP header.
     * \param p The packet.
     */
    void PktDropped(const Ipv4Header& ipH, const TcpHeader& tcpH, Ptr<const Packet> p);
    void FinalChecks() override;
 
    void ConfigureProperties() override;
    void ConfigureEnvironment() override;
 
    bool m_pktDropped;         //!< The packet has been dropped.
    bool m_pktWasDropped;      //!< The packet was dropped (according to the receiver).
    uint32_t m_seqToKill;      //!< Sequence number to drop.
    uint32_t m_dupAckReceived; //!< DipACk received.
 
    SequenceNumber32 m_previousAck;   //!< Previous ACK received.
    SequenceNumber32 m_sndNextExpSeq; //!< Sender next expected sequence number.
    SequenceNumber32 m_rcvNextExpAck; //!< Receiver next expected sequence number.
 
    uint32_t m_countRetr; //!< Retry counter.
 
    uint32_t m_bytesRcvButNotAcked; //!< Number of bytes received but not acked.
 
    Ptr<TcpSeqErrorModel> m_errorModel; //!< Error model.
};
 
TcpFastRetrTest::TcpFastRetrTest(TypeId typeId, uint32_t seqToKill, const std::string& msg)
    : TcpGeneralTest(msg),
      m_pktDropped(false),
      m_pktWasDropped(false),
      m_seqToKill(seqToKill),
      m_dupAckReceived(0),
      m_sndNextExpSeq(0),
      m_rcvNextExpAck(1),
      m_countRetr(0),
      m_bytesRcvButNotAcked(0)
{
    m_congControlTypeId = typeId;
}
 
void
TcpFastRetrTest::ConfigureProperties()
{
    TcpGeneralTest::ConfigureProperties();
    SetInitialSsThresh(SENDER, 0);
}
 
void
TcpFastRetrTest::ConfigureEnvironment()
{
    TcpGeneralTest::ConfigureEnvironment();
    SetAppPktCount(100);
}
 
Ptr<ErrorModel>
TcpFastRetrTest::CreateSenderErrorModel()
{
    return nullptr;
}
 
Ptr<ErrorModel>
TcpFastRetrTest::CreateReceiverErrorModel()
{
    m_errorModel = CreateObject<TcpSeqErrorModel>();
    m_errorModel->AddSeqToKill(SequenceNumber32(m_seqToKill));
    m_errorModel->SetDropCallback(MakeCallback(&TcpFastRetrTest::PktDropped, this));
 
    return m_errorModel;
}
 
Ptr<TcpSocketMsgBase>
TcpFastRetrTest::CreateSenderSocket(Ptr<Node> node)
{
    Ptr<TcpSocketMsgBase> socket = TcpGeneralTest::CreateSenderSocket(node);
    socket->SetAttribute("MinRto", TimeValue(Seconds(10.0)));
 
    return socket;
}
 
void
TcpFastRetrTest::Rx(const Ptr<const Packet> p, const TcpHeader& h, SocketWho who)
{
    if (who == SENDER)
    {
        // Nothing to check
        NS_LOG_INFO("\tSENDER Rx " << h);
    }
    else if (who == RECEIVER)
    {
        NS_LOG_INFO("\tRECEIVER Rx " << h);
 
        // Receiver has received the missing segment
        if (h.GetSequenceNumber().GetValue() == m_seqToKill)
        {
            m_pktDropped = false;
            if (m_bytesRcvButNotAcked > 0)
            {
                m_rcvNextExpAck += m_bytesRcvButNotAcked + GetSegSize(SENDER);
                m_bytesRcvButNotAcked = 0;
            }
        }
 
        // Count all the received bytes not acked
        if (m_pktDropped)
        {
            m_bytesRcvButNotAcked += GetSegSize(SENDER);
        }
    }
}
 
void
TcpFastRetrTest::Tx(const Ptr<const Packet> p, const TcpHeader& h, SocketWho who)
{
    if (who == SENDER)
    {
        NS_LOG_INFO("\tSENDER Tx " << h << " size=" << p->GetSize());
 
        if (h.GetSequenceNumber().GetValue() == m_seqToKill && m_pktDropped)
        {
            // Spotted the retransmission!
            m_countRetr++;
            NS_TEST_ASSERT_MSG_EQ(m_countRetr, 1, "Segment retransmitted too many times");
        }
        else
        {
            // No delayed ACK involved here.
            while (h.GetSequenceNumber() < m_sndNextExpSeq)
            {
                m_sndNextExpSeq -= GetSegSize(SENDER);
            }
 
            if (h.GetSequenceNumber().GetValue() != 50002)
            {
                NS_TEST_ASSERT_MSG_EQ(m_sndNextExpSeq,
                                      h.GetSequenceNumber(),
                                      "Sequence number expected differs");
            }
        }
 
        // SYN or Pure ACK in three-way handshake, then we expect data
        if ((m_sndNextExpSeq.GetValue() == 0) ||
            (m_sndNextExpSeq.GetValue() == 1 && p->GetSize() == 32))
        {
            m_sndNextExpSeq = SequenceNumber32(1);
        }
        else
        {
            // Data segments
            m_sndNextExpSeq += GetSegSize(SENDER);
        }
    }
    else if (who == RECEIVER)
    {
        NS_LOG_INFO("\tRECEIVER Tx, " << h << " size=" << p->GetSize());
 
        if (h.GetFlags() == (TcpHeader::SYN | TcpHeader::ACK))
        {
            NS_TEST_ASSERT_MSG_EQ(h.GetSequenceNumber().GetValue(),
                                  0,
                                  "SYN pkt has not 0 as initial sequence number."
                                  "Probably, random sqn number has been implemented."
                                  "Check this test");
        }
        else
        {
            NS_TEST_ASSERT_MSG_EQ(h.GetSequenceNumber().GetValue(),
                                  1,
                                  "ACK pkt has not 1 as sequence number."
                                  "Probably, random sqn number has been implemented."
                                  "Check this test");
        }
 
        // Accounted for delayed ACK, but not received.
        while (h.GetAckNumber() < m_rcvNextExpAck)
        {
            m_rcvNextExpAck -= GetSegSize(SENDER);
        }
 
        if (m_rcvNextExpAck.GetValue() >= 50001)
        {
            m_rcvNextExpAck = 50002;
        }
 
        NS_TEST_ASSERT_MSG_EQ(h.GetAckNumber(), m_rcvNextExpAck, "ACKing something not considered");
 
        if (m_pktDropped)
        {
            m_rcvNextExpAck = SequenceNumber32(m_seqToKill);
        }
        else
        {
            switch (m_rcvNextExpAck.GetValue())
            {
            case 0:
                m_rcvNextExpAck = SequenceNumber32(1);
                break;
            case 1:
                m_rcvNextExpAck += GetSegSize(SENDER);
                break;
            case 50002:
                break;
            default:
                m_rcvNextExpAck += GetSegSize(SENDER) * GetDelAckCount(SENDER);
            }
        }
    }
}
 
void
TcpFastRetrTest::RcvAck(const Ptr<const TcpSocketState> tcb, const TcpHeader& h, SocketWho who)
{
    NS_LOG_FUNCTION(this << tcb << h << who);
 
    if (who == SENDER)
    {
        if (h.GetAckNumber().GetValue() < m_seqToKill)
        {
            NS_TEST_ASSERT_MSG_EQ(tcb->m_congState.Get(),
                                  TcpSocketState::CA_OPEN,
                                  "Not in OPEN state to respond to a loss");
            NS_TEST_ASSERT_MSG_EQ(GetDupAckCount(SENDER),
                                  0,
                                  "Dupack different than 0 but no loss detected");
        }
        else if (h.GetAckNumber().GetValue() == m_seqToKill)
        {
            NS_TEST_ASSERT_MSG_EQ(GetDupAckCount(SENDER), m_dupAckReceived, "Dupack count differs");
 
            if (GetDupAckCount(SENDER) == 0 && GetDupAckCount(SENDER) < GetReTxThreshold(SENDER))
            {
                NS_TEST_ASSERT_MSG_EQ(tcb->m_congState.Get(),
                                      TcpSocketState::CA_OPEN,
                                      "Not in OPEN state for processing dupack");
            }
            else if (GetDupAckCount(SENDER) > 0 &&
                     GetDupAckCount(SENDER) < GetReTxThreshold(SENDER))
            {
                NS_TEST_ASSERT_MSG_EQ(tcb->m_congState.Get(),
                                      TcpSocketState::CA_DISORDER,
                                      "Not in DISORDER state after receiving dupacks");
            }
            else if (GetDupAckCount(SENDER) >= GetReTxThreshold(SENDER))
            {
                NS_TEST_ASSERT_MSG_EQ(tcb->m_congState.Get(),
                                      TcpSocketState::CA_RECOVERY,
                                      "Not in RECOVERY state after reaching retxthresh");
            }
        }
    }
    else if (who == RECEIVER)
    {
        NS_TEST_ASSERT_MSG_EQ(tcb->m_congState.Get(),
                              TcpSocketState::CA_OPEN,
                              "Receiver not in OPEN state");
    }
}
 
void
TcpFastRetrTest::ProcessedAck(const Ptr<const TcpSocketState> tcb,
                              const TcpHeader& h,
                              SocketWho who)
{
    NS_LOG_FUNCTION(this << tcb << h << who);
 
    if (who == SENDER)
    {
        if (m_previousAck == h.GetAckNumber() && h.GetAckNumber().GetValue() < 50002)
        {
            m_dupAckReceived++;
 
            NS_TEST_ASSERT_MSG_GT_OR_EQ(m_dupAckReceived,
                                        GetDupAckCount(SENDER),
                                        "Count of dupAck differs");
 
            if (GetDupAckCount(SENDER) < GetReTxThreshold(SENDER))
            {
                NS_TEST_ASSERT_MSG_EQ(tcb->m_congState.Get(),
                                      TcpSocketState::CA_DISORDER,
                                      "DupAck less than ReTxThreshold but not "
                                      "in DISORDER state");
            }
            else
            {
                NS_TEST_ASSERT_MSG_GT_OR_EQ(tcb->m_congState.Get(),
                                            TcpSocketState::CA_RECOVERY,
                                            "DupAck greater than ReTxThreshold but not "
                                            "in RECOVERY or LOSS state");
                m_pktWasDropped = true;
            }
        }
        else if (m_previousAck < h.GetAckNumber())
        {
            m_dupAckReceived = 0;
        }
 
        m_previousAck = h.GetAckNumber();
    }
    else if (who == RECEIVER)
    {
        NS_TEST_ASSERT_MSG_EQ(tcb->m_congState.Get(),
                              TcpSocketState::CA_OPEN,
                              "Different state than OPEN in the receiver");
    }
}
 
void
TcpFastRetrTest::AfterRTOExpired(const Ptr<const TcpSocketState> tcb, SocketWho who)
{
    NS_TEST_ASSERT_MSG_EQ(true, false, "RTO isn't expected here");
}
 
void
TcpFastRetrTest::CongStateTrace(const TcpSocketState::TcpCongState_t oldValue,
                                const TcpSocketState::TcpCongState_t newValue)
{
    NS_LOG_FUNCTION(this << oldValue << newValue);
 
    if (oldValue == TcpSocketState::CA_OPEN && newValue == TcpSocketState::CA_DISORDER)
    {
    }
    else if (oldValue == TcpSocketState::CA_OPEN && newValue == TcpSocketState::CA_RECOVERY &&
             GetReTxThreshold(SENDER) > 1)
    {
        NS_TEST_ASSERT_MSG_EQ(true, false, "Invalid OPEN to RECOVERY state change");
    }
    else if (oldValue == TcpSocketState::CA_DISORDER && newValue == TcpSocketState::CA_RECOVERY)
    {
        NS_TEST_ASSERT_MSG_EQ(GetReTxThreshold(SENDER),
                              GetDupAckCount(SENDER),
                              "DISORDER to RECOVERY state change but not reached "
                              "the ReTxThreshold");
    }
}
 
void
TcpFastRetrTest::PktDropped(const Ipv4Header& ipH, const TcpHeader& tcpH, Ptr<const Packet> p)
{
    NS_LOG_FUNCTION(this << ipH << tcpH);
 
    m_pktDropped = true;
    m_rcvNextExpAck = tcpH.GetSequenceNumber();
 
    NS_TEST_ASSERT_MSG_EQ(tcpH.GetSequenceNumber(),
                          SequenceNumber32(m_seqToKill),
                          "Packet dropped but sequence number differs");
}
 
void
TcpFastRetrTest::FinalChecks()
{
    NS_TEST_ASSERT_MSG_EQ(m_pktWasDropped, true, "Packet was not dropped at all");
    NS_TEST_ASSERT_MSG_EQ(m_countRetr, 1, "Segment was not retransmitted at all");
    NS_TEST_ASSERT_MSG_EQ(m_rcvNextExpAck.GetValue(), 50002, "Not all data have been transmitted");
}
 
/**
 * \ingroup internet-test
 *
 * \brief Testsuite for the fast retransmission
 */
class TcpFastRetrTestSuite : public TestSuite
{
  public:
    TcpFastRetrTestSuite()
        : TestSuite("tcp-fast-retr-test", Type::UNIT)
    {
        std::list<TypeId> types;
        types.insert(types.begin(), TcpWestwoodPlus::GetTypeId());
        types.insert(types.begin(), TcpNewReno::GetTypeId());
 
        for (auto it = types.begin(); it != types.end(); ++it)
        {
            AddTestCase(new TcpFastRetrTest((*it), 5001, "Fast Retransmit testing"),
                        TestCase::Duration::QUICK);
        }
    }
};
 
static TcpFastRetrTestSuite g_TcpFastRetrTestSuite; //!< Static variable for test initialization