lte-rlc-am-header.cc

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/*
 * Copyright (c) 2011 Centre Tecnologic de Telecomunicacions de Catalunya (CTTC)
 *
 * SPDX-License-Identifier: GPL-2.0-only
 *
 * Author: Manuel Requena <manuel.requena@cttc.es>
 */
 
#include "lte-rlc-am-header.h"
 
#include "ns3/log.h"
 
namespace ns3
{
 
NS_LOG_COMPONENT_DEFINE("LteRlcAmHeader");
 
NS_OBJECT_ENSURE_REGISTERED(LteRlcAmHeader);
 
LteRlcAmHeader::LteRlcAmHeader()
    : m_headerLength(0),
      m_dataControlBit(0xff),
      m_resegmentationFlag(0xff),
      m_pollingBit(0xff),
      m_framingInfo(0xff),
      m_sequenceNumber(0xfffa),
      m_segmentOffset(0xffff),
      m_lastOffset(0xffff),
      m_controlPduType(0xff),
      m_ackSn(0xffff)
{
}
 
LteRlcAmHeader::~LteRlcAmHeader()
{
    m_headerLength = 0;
    m_dataControlBit = 0xff;
    m_resegmentationFlag = 0xff;
    m_pollingBit = 0xff;
    m_framingInfo = 0xff;
    m_sequenceNumber = 0xfffb;
    m_segmentOffset = 0xffff;
    m_lastOffset = 0xffff;
    m_controlPduType = 0xff;
    m_ackSn = 0xffff;
}
 
void
LteRlcAmHeader::SetDataPdu()
{
    m_headerLength = 4;
    m_dataControlBit = DATA_PDU;
}
 
void
LteRlcAmHeader::SetControlPdu(uint8_t controlPduType)
{
    m_headerLength = 2;
    m_dataControlBit = CONTROL_PDU;
    m_controlPduType = controlPduType;
}
 
bool
LteRlcAmHeader::IsDataPdu() const
{
    return m_dataControlBit == DATA_PDU;
}
 
bool
LteRlcAmHeader::IsControlPdu() const
{
    return m_dataControlBit == CONTROL_PDU;
}
 
void
LteRlcAmHeader::SetFramingInfo(uint8_t framingInfo)
{
    m_framingInfo = framingInfo & 0x03;
}
 
void
LteRlcAmHeader::SetSequenceNumber(SequenceNumber10 sequenceNumber)
{
    m_sequenceNumber = sequenceNumber;
}
 
uint8_t
LteRlcAmHeader::GetFramingInfo() const
{
    return m_framingInfo;
}
 
SequenceNumber10
LteRlcAmHeader::GetSequenceNumber() const
{
    return m_sequenceNumber;
}
 
void
LteRlcAmHeader::PushExtensionBit(uint8_t extensionBit)
{
    m_extensionBits.push_back(extensionBit);
    if (m_extensionBits.size() > 1)
    {
        if (m_extensionBits.size() % 2)
        {
            m_headerLength += 1;
        }
        else
        {
            m_headerLength += 2;
        }
    }
}
 
void
LteRlcAmHeader::PushLengthIndicator(uint16_t lengthIndicator)
{
    m_lengthIndicators.push_back(lengthIndicator);
}
 
uint8_t
LteRlcAmHeader::PopExtensionBit()
{
    uint8_t extensionBit = m_extensionBits.front();
    m_extensionBits.pop_front();
 
    return extensionBit;
}
 
uint16_t
LteRlcAmHeader::PopLengthIndicator()
{
    uint16_t lengthIndicator = m_lengthIndicators.front();
    m_lengthIndicators.pop_front();
 
    return lengthIndicator;
}
 
void
LteRlcAmHeader::SetResegmentationFlag(uint8_t resegFlag)
{
    m_resegmentationFlag = resegFlag & 0x01;
}
 
uint8_t
LteRlcAmHeader::GetResegmentationFlag() const
{
    return m_resegmentationFlag;
}
 
void
LteRlcAmHeader::SetPollingBit(uint8_t pollingBit)
{
    m_pollingBit = pollingBit & 0x01;
}
 
uint8_t
LteRlcAmHeader::GetPollingBit() const
{
    return m_pollingBit;
}
 
void
LteRlcAmHeader::SetLastSegmentFlag(uint8_t lsf)
{
    m_lastSegmentFlag = lsf & 0x01;
}
 
uint8_t
LteRlcAmHeader::GetLastSegmentFlag() const
{
    return m_lastSegmentFlag;
}
 
void
LteRlcAmHeader::SetSegmentOffset(uint16_t segmentOffset)
{
    m_segmentOffset = segmentOffset & 0x7FFF;
}
 
uint16_t
LteRlcAmHeader::GetSegmentOffset() const
{
    return m_segmentOffset;
}
 
uint16_t
LteRlcAmHeader::GetLastOffset() const
{
    return m_lastOffset;
}
 
void
LteRlcAmHeader::SetAckSn(SequenceNumber10 ackSn)
{
    m_ackSn = ackSn;
}
 
bool
LteRlcAmHeader::OneMoreNackWouldFitIn(uint16_t bytes)
{
    NS_LOG_FUNCTION(this << bytes);
    NS_ASSERT_MSG(m_dataControlBit == CONTROL_PDU && m_controlPduType == LteRlcAmHeader::STATUS_PDU,
                  "method allowed only for STATUS PDUs");
    if (m_nackSnList.size() % 2 == 0)
    {
        return (m_headerLength < bytes);
    }
    else
    {
        return (m_headerLength < (bytes - 1));
    }
}
 
void
LteRlcAmHeader::PushNack(int nack)
{
    NS_LOG_FUNCTION(this << nack);
    NS_ASSERT_MSG(m_dataControlBit == CONTROL_PDU && m_controlPduType == LteRlcAmHeader::STATUS_PDU,
                  "method allowed only for STATUS PDUs");
    m_nackSnList.push_back(nack);
 
    if (m_nackSnList.size() % 2 == 0)
    {
        m_headerLength++;
    }
    else
    {
        m_headerLength += 2;
    }
}
 
bool
LteRlcAmHeader::IsNackPresent(SequenceNumber10 nack)
{
    NS_LOG_FUNCTION(this);
    NS_ASSERT_MSG(m_dataControlBit == CONTROL_PDU && m_controlPduType == LteRlcAmHeader::STATUS_PDU,
                  "method allowed only for STATUS PDUs");
    for (auto nackIt = m_nackSnList.begin(); nackIt != m_nackSnList.end(); ++nackIt)
    {
        if ((*nackIt) == nack.GetValue())
        {
            return true;
        }
    }
    return false;
}
 
int
LteRlcAmHeader::PopNack()
{
    NS_LOG_FUNCTION(this);
    NS_ASSERT_MSG(m_dataControlBit == CONTROL_PDU && m_controlPduType == LteRlcAmHeader::STATUS_PDU,
                  "method allowed only for STATUS PDUs");
    if (m_nackSnList.empty())
    {
        return -1;
    }
 
    int nack = m_nackSnList.front();
    m_nackSnList.pop_front();
 
    return nack;
}
 
SequenceNumber10
LteRlcAmHeader::GetAckSn() const
{
    return m_ackSn;
}
 
TypeId
LteRlcAmHeader::GetTypeId()
{
    static TypeId tid = TypeId("ns3::LteRlcAmHeader")
                            .SetParent<Header>()
                            .SetGroupName("Lte")
                            .AddConstructor<LteRlcAmHeader>();
    return tid;
}
 
TypeId
LteRlcAmHeader::GetInstanceTypeId() const
{
    return GetTypeId();
}
 
void
LteRlcAmHeader::Print(std::ostream& os) const
{
    auto it1 = m_extensionBits.begin();
    auto it2 = m_lengthIndicators.begin();
    auto it3 = m_nackSnList.begin();
 
    os << "Len=" << m_headerLength;
    os << " D/C=" << (uint16_t)m_dataControlBit;
 
    if (m_dataControlBit == DATA_PDU)
    {
        os << " RF=" << (uint16_t)m_resegmentationFlag;
        os << " P=" << (uint16_t)m_pollingBit;
        os << " FI=" << (uint16_t)m_framingInfo;
        os << " E=" << (uint16_t)(*it1);
        os << " SN=" << m_sequenceNumber;
        os << " LSF=" << (uint16_t)(m_lastSegmentFlag);
        os << " SO=" << m_segmentOffset;
 
        it1++;
        if (it1 != m_extensionBits.end())
        {
            os << " E=";
        }
        while (it1 != m_extensionBits.end())
        {
            os << (uint16_t)(*it1);
            it1++;
        }
 
        if (it2 != m_lengthIndicators.end())
        {
            os << " LI=";
        }
        while (it2 != m_lengthIndicators.end())
        {
            os << (uint16_t)(*it2) << " ";
            it2++;
        }
    }
    else // if ( m_dataControlBit == CONTROL_PDU )
    {
        os << " ACK_SN=" << m_ackSn;
 
        while (it3 != m_nackSnList.end())
        {
            os << " NACK_SN=" << (int)(*it3);
            it3++;
        }
    }
}
 
uint32_t
LteRlcAmHeader::GetSerializedSize() const
{
    return m_headerLength;
}
 
void
LteRlcAmHeader::Serialize(Buffer::Iterator start) const
{
    Buffer::Iterator i = start;
 
    auto it1 = m_extensionBits.begin();
    auto it2 = m_lengthIndicators.begin();
    auto it3 = m_nackSnList.begin();
 
    if (m_dataControlBit == DATA_PDU)
    {
        i.WriteU8(((DATA_PDU << 7) & 0x80) | ((m_resegmentationFlag << 6) & 0x40) |
                  ((m_pollingBit << 5) & 0x20) | ((m_framingInfo << 3) & 0x18) |
                  (((*it1) << 2) & 0x04) | ((m_sequenceNumber.GetValue() >> 8) & 0x0003));
        i.WriteU8(m_sequenceNumber.GetValue() & 0x00FF);
        i.WriteU8(((m_lastSegmentFlag << 7) & 0x80) | ((m_segmentOffset >> 8) & 0x007F));
        i.WriteU8(m_segmentOffset & 0x00FF);
        it1++;
 
        while (it1 != m_extensionBits.end() && it2 != m_lengthIndicators.end())
        {
            uint16_t oddLi;
            uint16_t evenLi;
            uint8_t oddE;
            uint8_t evenE;
 
            oddE = *it1;
            oddLi = *it2;
 
            it1++;
            it2++;
 
            if (it1 != m_extensionBits.end() && it2 != m_lengthIndicators.end())
            {
                evenE = *it1;
                evenLi = *it2;
 
                i.WriteU8(((oddE << 7) & 0x80) | ((oddLi >> 4) & 0x007F));
                i.WriteU8(((oddLi << 4) & 0x00F0) | ((evenE << 3) & 0x08) |
                          ((evenLi >> 8) & 0x0007));
                i.WriteU8(evenLi & 0x00FF);
 
                it1++;
                it2++;
            }
            else
            {
                i.WriteU8(((oddE << 7) & 0x80) | ((oddLi >> 4) & 0x007F));
                i.WriteU8((oddLi << 4) & 0x00F0); // Padding is implicit
            }
        }
    }
    else // if ( m_dataControlBit == CONTROL_PDU )
    {
        i.WriteU8(((CONTROL_PDU << 7) & 0x80) | ((m_controlPduType << 4) & 0x70) |
                  ((m_ackSn.GetValue() >> 6) & 0x0F));
        // note: second part of ackSn will be written later
 
        // serialize the NACKs
        if (it3 == m_nackSnList.end())
        {
            NS_LOG_LOGIC(this << " no NACKs");
            // If there are no NACKs then this line adds the rest of the ACK
            // along with 0x00, indicating an E1 value of 0 or no NACKs follow.
            i.WriteU8((m_ackSn.GetValue() << 2) & 0xFC);
        }
        else
        {
            int oddNack = *it3;
            int evenNack = -1;
            // Else write out a series of E1 = 1 and NACK values. Note since we
            // are not supporting SO start/end the value of E2 will always be 0.
 
            // First write out the ACK along with the very first NACK
            // And the remaining NACK with 0x02 or 10 in binary to set
            // E1 to 1, then Or in the first bit of the NACK
            i.WriteU8(((m_ackSn.GetValue() << 2) & 0xFC) | (0x02) | ((*it3 >> 9) & 0x01));
 
            while (it3 != m_nackSnList.end())
            {
                // The variable oddNack has the current NACK value to write, also
                // either the setup to enter this loop or the previous loop would
                // have written the highest order bit to the previous octet.
                // Write the next set of bits (2 - 9) into the next octet
                i.WriteU8((oddNack >> 1) & 0xFF);
 
                // Next check to see if there is going to be another NACK after
                // this
                it3++;
                if (it3 != m_nackSnList.end())
                {
                    // Yes there will be another NACK after this, so E1 will be 1
                    evenNack = *it3;
                    i.WriteU8(((oddNack << 7) & 0x80) | (0x40) // E1 = 1 E2 = 0, more NACKs
                              | ((evenNack >> 5) & 0x1F));
 
                    // The final octet of this loop will have the rest of the
                    // NACK and another E1, E2. Check to see if there will be
                    // one more NACK after this.
                    it3++;
                    if (it3 != m_nackSnList.end())
                    {
                        // Yes there is at least one more NACK. Finish writing
                        // this octet and the next iteration will do the rest.
                        oddNack = *it3;
                        i.WriteU8(((evenNack << 3) & 0xF8) | (0x04) | ((oddNack >> 9) & 0x01));
                    }
                    else
                    {
                        // No, there are no more NACKs
                        i.WriteU8((evenNack << 3) & 0xF8);
                    }
                }
                else
                {
                    // No, this is the last NACK so E1 will be 0
                    i.WriteU8((oddNack << 7) & 0x80);
                }
            }
        }
    }
}
 
uint32_t
LteRlcAmHeader::Deserialize(Buffer::Iterator start)
{
    Buffer::Iterator i = start;
    uint8_t byte_1;
    uint8_t byte_2;
    uint8_t byte_3;
    uint8_t byte_4;
    uint8_t extensionBit;
 
    byte_1 = i.ReadU8();
    m_headerLength = 1;
    m_dataControlBit = (byte_1 & 0x80) >> 7;
 
    if (m_dataControlBit == DATA_PDU)
    {
        byte_2 = i.ReadU8();
        byte_3 = i.ReadU8();
        byte_4 = i.ReadU8();
        m_headerLength += 3;
 
        m_resegmentationFlag = (byte_1 & 0x40) >> 6;
        m_pollingBit = (byte_1 & 0x20) >> 5;
        m_framingInfo = (byte_1 & 0x18) >> 3;
        m_sequenceNumber = ((byte_1 & 0x03) << 8) | byte_2;
 
        m_lastSegmentFlag = (byte_3 & 0x80) >> 7;
        m_segmentOffset = (byte_3 & 0x7F) | byte_4;
 
        extensionBit = (byte_1 & 0x04) >> 2;
        m_extensionBits.push_back(extensionBit);
 
        if (extensionBit == DATA_FIELD_FOLLOWS)
        {
            return GetSerializedSize();
        }
 
        uint16_t oddLi;
        uint16_t evenLi;
        uint8_t oddE;
        uint8_t evenE;
        bool moreLiFields = (extensionBit == E_LI_FIELDS_FOLLOWS);
 
        while (moreLiFields)
        {
            byte_1 = i.ReadU8();
            byte_2 = i.ReadU8();
 
            oddE = (byte_1 & 0x80) >> 7;
            oddLi = ((byte_1 & 0x7F) << 4) | ((byte_2 & 0xF0) >> 4);
            moreLiFields = (oddE == E_LI_FIELDS_FOLLOWS);
 
            m_extensionBits.push_back(oddE);
            m_lengthIndicators.push_back(oddLi);
            m_headerLength += 2;
 
            if (moreLiFields)
            {
                byte_3 = i.ReadU8();
 
                evenE = (byte_2 & 0x08) >> 3;
                evenLi = ((byte_2 & 0x07) << 8) | (byte_3 & 0xFF);
                moreLiFields = (evenE == E_LI_FIELDS_FOLLOWS);
 
                m_extensionBits.push_back(evenE);
                m_lengthIndicators.push_back(evenLi);
 
                m_headerLength += 1;
            }
        }
 
        if (m_resegmentationFlag == SEGMENT)
        {
            m_lastOffset = m_segmentOffset + start.GetSize() - m_headerLength;
        }
    }
    else // if ( m_dataControlBit == CONTROL_PDU )
    {
        byte_2 = i.ReadU8();
 
        m_controlPduType = (byte_1 & 0x70) >> 4;
        m_ackSn = ((byte_1 & 0x0F) << 6) | ((byte_2 & 0xFC) >> 2);
 
        int moreNacks = (byte_2 & 0x02) >> 1;
        // Get the first NACK outside the loop as it is not preceded by an E2
        // field but all following NACKs will.
        if (moreNacks == 1)
        {
            byte_3 = i.ReadU8();
            byte_4 = i.ReadU8();
            m_headerLength = 4;
 
            m_nackSnList.push_back(((byte_2 & 0x01) << 9) | (byte_3 << 1) | ((byte_4 & 0x80) >> 7));
 
            // Loop until all NACKs are found
            moreNacks = ((byte_4 & 0x40) >> 6);
            uint8_t byte = byte_4;
            uint8_t nextByte;
            uint8_t finalByte;
            while (moreNacks == 1)
            {
                // Ignore E2, read next NACK
                nextByte = i.ReadU8();
                m_nackSnList.push_back(((byte & 0x1F) << 5) | ((nextByte & 0xF8) >> 3));
 
                // Check for another NACK, after this any following NACKs will
                // be aligned properly for the next iteration of this loop.
                moreNacks = (nextByte & 0x04) >> 2;
                byte = nextByte;
                if (moreNacks == 1)
                {
                    nextByte = i.ReadU8();
                    finalByte = i.ReadU8();
 
                    m_nackSnList.push_back(((byte & 0x01) << 9) | (nextByte << 1) |
                                           ((finalByte & 0x80) >> 7));
 
                    moreNacks = ((finalByte & 0x40) >> 6);
                    byte = finalByte;
                    m_headerLength += 3;
                }
                else
                {
                    m_headerLength++;
                }
            }
        }
        else
        {
            m_headerLength++;
        }
    }
 
    return GetSerializedSize();
}
 
}; // namespace ns3