satellite-return-link-encapsulator.cc

Go to the documentation of this file.

/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/*
 * Copyright (c) 2013 Magister Solutions Ltd.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation;
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * Author: Jani Puttonen <jani.puttonen@magister.fi>
 */
 
#include "satellite-return-link-encapsulator.h"
 
#include "satellite-encap-pdu-status-tag.h"
#include "satellite-llc.h"
#include "satellite-mac-tag.h"
#include "satellite-queue.h"
#include "satellite-rle-header.h"
#include "satellite-uplink-info-tag.h"
 
#include <ns3/log.h>
#include <ns3/mac48-address.h>
#include <ns3/simulator.h>
 
#include <algorithm>
 
NS_LOG_COMPONENT_DEFINE("SatReturnLinkEncapsulator");
 
namespace ns3
{
 
NS_OBJECT_ENSURE_REGISTERED(SatReturnLinkEncapsulator);
 
SatReturnLinkEncapsulator::SatReturnLinkEncapsulator()
    : m_txFragmentId(0),
      m_currRxFragmentId(0),
      m_currRxPacketSize(0),
      m_currRxPacketFragmentBytes(0),
      m_minTxOpportunity(0),
      MAX_FRAGMENT_ID(8),
      MAX_PPDU_PACKET_SIZE(2048),
      MAX_HL_PDU_PACKET_SIZE(4096)
{
    NS_LOG_FUNCTION(this);
    NS_ASSERT(false);
 
}
 
SatReturnLinkEncapsulator::SatReturnLinkEncapsulator(Mac48Address encapAddress,
                                                     Mac48Address decapAddress,
                                                     Mac48Address sourceE2EAddress,
                                                     Mac48Address destE2EAddress,
                                                     uint8_t flowId,
                                                     uint32_t additionalHeaderSize)
    : SatBaseEncapsulator(encapAddress,
                          decapAddress,
                          sourceE2EAddress,
                          destE2EAddress,
                          flowId,
                          additionalHeaderSize),
      m_txFragmentId(0),
      m_currRxFragmentId(0),
      m_currRxPacketSize(0),
      m_currRxPacketFragmentBytes(0),
      m_minTxOpportunity(0),
      MAX_FRAGMENT_ID(8),
      MAX_PPDU_PACKET_SIZE(2048),
      MAX_HL_PDU_PACKET_SIZE(4096)
{
    NS_LOG_FUNCTION(this);
 
    SatPPduHeader ppduHeader;
    m_minTxOpportunity = ppduHeader.GetMaxHeaderSizeInBytes();
}
 
SatReturnLinkEncapsulator::~SatReturnLinkEncapsulator()
{
    NS_LOG_FUNCTION(this);
}
 
TypeId
SatReturnLinkEncapsulator::GetTypeId(void)
{
    static TypeId tid = TypeId("ns3::SatReturnLinkEncapsulator")
                            .SetParent<SatBaseEncapsulator>()
                            .AddConstructor<SatReturnLinkEncapsulator>();
    return tid;
}
 
void
SatReturnLinkEncapsulator::DoDispose()
{
    NS_LOG_FUNCTION(this);
 
    SatBaseEncapsulator::DoDispose();
}
 
void
SatReturnLinkEncapsulator::EnquePdu(Ptr<Packet> p, Mac48Address /*dest*/)
{
    NS_LOG_FUNCTION(this << p->GetSize());
 
    // If the packet is smaller than the maximum size
    if (p->GetSize() > MAX_HL_PDU_PACKET_SIZE)
    {
        NS_FATAL_ERROR("SatReturnLinkEncapsulator received too large HL PDU!");
    }
 
    // Mark the PDU with FULL_PDU tag
    SatEncapPduStatusTag tag;
    tag.SetStatus(SatEncapPduStatusTag::FULL_PDU);
    p->AddPacketTag(tag);
 
    // Add MAC tag to identify the packet in lower layers
    SatMacTag mTag;
    mTag.SetDestAddress(m_decapAddress);
    mTag.SetSourceAddress(m_encapAddress);
    p->AddPacketTag(mTag);
 
    NS_LOG_INFO("Tx Buffer: New packet added of size: " << p->GetSize());
 
    if (!m_txQueue->Enqueue(p))
    {
        NS_LOG_INFO("Packet is dropped!");
    }
 
    NS_LOG_INFO("NumPackets = " << m_txQueue->GetNPackets());
    NS_LOG_INFO("NumBytes = " << m_txQueue->GetNBytes());
}
 
Ptr<Packet>
SatReturnLinkEncapsulator::NotifyTxOpportunity(uint32_t bytes,
                                               uint32_t& bytesLeft,
                                               uint32_t& nextMinTxO)
{
    NS_LOG_FUNCTION(this << bytes);
    NS_LOG_INFO("TxOpportunity for UT: " << m_encapAddress << " flowId: " << (uint32_t)m_flowId
                                         << " of " << bytes << " bytes");
 
    // Payload adapted PDU = NULL
    Ptr<Packet> packet;
 
    NS_LOG_INFO("Queue size before TxOpportunity: " << m_txQueue->GetNBytes());
 
    // No packets in buffer
    if (m_txQueue->GetNPackets() == 0)
    {
        NS_LOG_INFO("No data pending, return NULL packet");
        return packet;
    }
 
    packet = GetNewRlePdu(bytes, MAX_PPDU_PACKET_SIZE, m_additionalHeaderSize);
 
    if (packet)
    {
        // Add MAC tag to identify the packet in lower layers if not already added
        SatMacTag mTag;
        if (!packet->PeekPacketTag(mTag))
        {
            mTag.SetDestAddress(m_decapAddress);
            mTag.SetSourceAddress(m_encapAddress);
            packet->AddPacketTag(mTag);
        }
 
        // Add E2E address tag to identify the packet in lower layers
        SatAddressE2ETag addressE2ETag;
        if (!packet->PeekPacketTag(addressE2ETag))
        {
            addressE2ETag.SetE2EDestAddress(m_destE2EAddress);
            addressE2ETag.SetE2ESourceAddress(m_sourceE2EAddress);
            packet->AddPacketTag(addressE2ETag);
        }
 
        // Add flow id tag
        SatFlowIdTag flowIdTag;
        flowIdTag.SetFlowId(m_flowId);
        packet->AddPacketTag(flowIdTag);
 
        if (packet->GetSize() > bytes)
        {
            NS_FATAL_ERROR("Created packet of size: "
                           << packet->GetSize() << " is larger than the tx opportunity: " << bytes);
        }
        NS_LOG_INFO("Created packet size: " << packet->GetSize());
    }
 
    NS_LOG_INFO("Queue size after TxOpportunity: " << m_txQueue->GetNBytes());
 
    // Update bytes lefts
    bytesLeft = GetTxBufferSizeInBytes();
 
    // Update min TxO
    nextMinTxO = GetMinTxOpportunityInBytes();
 
    return packet;
}
 
Ptr<Packet>
SatReturnLinkEncapsulator::GetNewRlePdu(uint32_t txOpportunityBytes,
                                        uint32_t maxRlePduSize,
                                        uint32_t additionalHeaderSize)
{
    NS_LOG_FUNCTION(this << txOpportunityBytes << maxRlePduSize << additionalHeaderSize);
 
    // Payload adapted PDU = NULL
    Ptr<Packet> packet;
 
    // RLE (PPDU) header
    SatPPduHeader ppduHeader;
 
    // Peek the first PDU from the buffer.
    Ptr<const Packet> peekSegment = m_txQueue->Peek();
 
    SatEncapPduStatusTag tag;
    bool found = peekSegment->PeekPacketTag(tag);
    if (!found)
    {
        NS_FATAL_ERROR("EncapPduStatus tag not found from packet!");
    }
 
    // Tx opportunity bytes is not enough
    uint32_t headerSize = ppduHeader.GetHeaderSizeInBytes(tag.GetStatus()) + additionalHeaderSize;
    if (txOpportunityBytes <= headerSize)
    {
        NS_LOG_INFO("TX opportunity too small = " << txOpportunityBytes);
        return packet;
    }
 
    NS_LOG_INFO("Size of the first packet in buffer: " << peekSegment->GetSize());
    NS_LOG_INFO("Encapsulation status of the first packet in buffer: " << tag.GetStatus());
 
    // Build Data field
    uint32_t maxSegmentSize = std::min(txOpportunityBytes, maxRlePduSize) - headerSize;
 
    NS_LOG_INFO("Maximum supported segment size: " << maxSegmentSize);
 
    // Fragmentation if the HL PDU does not fit into the burst or
    // the HL packet is too large.
    if (peekSegment->GetSize() > maxSegmentSize)
    {
        NS_LOG_INFO("Buffered packet is larger than the maximum segment size!");
 
        if (tag.GetStatus() == SatEncapPduStatusTag::FULL_PDU)
        {
            // Calculate again that the packet fits into the Tx opportunity
            headerSize = ppduHeader.GetHeaderSizeInBytes(SatEncapPduStatusTag::START_PDU) +
                         additionalHeaderSize;
            if (txOpportunityBytes <= headerSize)
            {
                NS_LOG_INFO("Start PDU does not fit into the TxOpportunity anymore!");
                return packet;
            }
 
            maxSegmentSize = std::min(txOpportunityBytes, maxRlePduSize) - headerSize;
            NS_LOG_INFO("Recalculated maximum supported segment size: " << maxSegmentSize);
 
            // In case we have to fragment a FULL PDU, we need to increase
            // the fragment id.
            IncreaseFragmentId();
        }
        // END_PDU
        else
        {
            // Calculate again that the packet fits into the Tx opportunity
            headerSize = ppduHeader.GetHeaderSizeInBytes(SatEncapPduStatusTag::CONTINUATION_PDU) +
                         additionalHeaderSize;
            if (txOpportunityBytes <= headerSize)
            {
                NS_LOG_INFO("Continuation PDU does not fit into the TxOpportunity anymore!");
                return packet;
            }
 
            maxSegmentSize = std::min(txOpportunityBytes, maxRlePduSize) - headerSize;
            NS_LOG_INFO("Recalculated maximum supported segment size: " << maxSegmentSize);
        }
 
        // Now we can take the packe away from the queue
        Ptr<Packet> firstSegment = m_txQueue->Dequeue();
 
        // Create a new fragment
        Ptr<Packet> newSegment = firstSegment->CreateFragment(0, maxSegmentSize);
 
        // Status tag of the new and remaining segments
        // Note: This is the only place where a PDU is segmented and
        // therefore its status can change
        SatEncapPduStatusTag oldTag, newTag;
        firstSegment->RemovePacketTag(oldTag);
        newSegment->RemovePacketTag(newTag);
 
        // Create new PPDU header
        ppduHeader.SetPPduLength(newSegment->GetSize());
        ppduHeader.SetFragmentId(m_txFragmentId);
 
        if (oldTag.GetStatus() == SatEncapPduStatusTag::FULL_PDU)
        {
            ppduHeader.SetStartIndicator();
            ppduHeader.SetTotalLength(firstSegment->GetSize());
 
            newTag.SetStatus(SatEncapPduStatusTag::START_PDU);
            oldTag.SetStatus(SatEncapPduStatusTag::END_PDU);
        }
        else if (oldTag.GetStatus() == SatEncapPduStatusTag::END_PDU)
        {
            // oldTag still is left with the END_PPDU tag
            newTag.SetStatus(SatEncapPduStatusTag::CONTINUATION_PDU);
        }
 
        // Give back the remaining segment to the transmission buffer
        firstSegment->RemoveAtStart(maxSegmentSize);
 
        // If bytes left after fragmentation
        if (firstSegment->GetSize() > 0)
        {
            NS_LOG_INFO("Returning the remaining " << firstSegment->GetSize()
                                                   << " bytes to buffer");
            firstSegment->AddPacketTag(oldTag);
            m_txQueue->PushFront(firstSegment);
        }
        else
        {
            NS_FATAL_ERROR("The full segment was taken even though we are in the fragmentation "
                           "part of the code!");
        }
 
        // Put status tag once it has been adjusted
        newSegment->AddPacketTag(newTag);
 
        // Add PPDU header
        newSegment->AddHeader(ppduHeader);
 
        // PPDU
        packet = newSegment;
 
        NS_LOG_INFO("Created a fragment of size: " << packet->GetSize());
    }
    // Packing functionality, for either a FULL_PPDU or END_PPDU
    else
    {
        NS_LOG_INFO("Packing functionality TxO: " << txOpportunityBytes
                                                  << " packet size: " << peekSegment->GetSize());
 
        if (tag.GetStatus() == SatEncapPduStatusTag::FULL_PDU)
        {
            ppduHeader.SetStartIndicator();
        }
        else
        {
            ppduHeader.SetFragmentId(m_txFragmentId);
        }
 
        // Take the packe away from the queue
        Ptr<Packet> firstSegment = m_txQueue->Dequeue();
 
        ppduHeader.SetEndIndicator();
        ppduHeader.SetPPduLength(firstSegment->GetSize());
 
        // Add PPDU header
        firstSegment->AddHeader(ppduHeader);
 
        // PPDU
        packet = firstSegment;
 
        NS_LOG_INFO("Packed a packet of size: " << packet->GetSize());
    }
 
    return packet;
}
 
void
SatReturnLinkEncapsulator::ReceivePdu(Ptr<Packet> p)
{
    NS_LOG_FUNCTION(this << p->GetSize());
 
    // Remove encap PDU status tag
    SatEncapPduStatusTag statusTag;
    p->RemovePacketTag(statusTag);
 
    // Remove flow id tag
    SatFlowIdTag flowIdTag;
    p->RemovePacketTag(flowIdTag);
 
    // Sanity check
    SatMacTag mTag;
    bool mSuccess = p->RemovePacketTag(mTag);
    if (!mSuccess)
    {
        NS_FATAL_ERROR("MAC tag not found in the packet!");
    }
    else if (mTag.GetDestAddress() != m_decapAddress)
    {
        NS_FATAL_ERROR("Packet was not intended for this receiver!");
    }
 
    // Do decapsulation and defragmentation
    ProcessPdu(p);
}
 
void
SatReturnLinkEncapsulator::ProcessPdu(Ptr<Packet> p)
{
    NS_LOG_FUNCTION(this << p->GetSize());
 
    // Remove PPDU header
    SatPPduHeader ppduHeader;
    p->RemoveHeader(ppduHeader);
 
    // FULL_PPDU
    if (ppduHeader.GetStartIndicator() == true && ppduHeader.GetEndIndicator() == true)
    {
        NS_LOG_INFO("FULL PPDU received");
 
        Reset();
 
        m_rxCallback(p, m_encapAddress, m_decapAddress);
    }
 
    // START_PPDU
    else if (ppduHeader.GetStartIndicator() == true && ppduHeader.GetEndIndicator() == false)
    {
        NS_LOG_INFO("START PPDU received");
 
        Reset();
 
        m_currRxFragmentId = ppduHeader.GetFragmentId();
        m_currRxPacketSize = ppduHeader.GetTotalLength();
        m_currRxPacketFragmentBytes = ppduHeader.GetPPduLength();
        m_currRxPacketFragment = p;
    }
 
    // CONTINUATION_PPDU
    else if (ppduHeader.GetStartIndicator() == false && ppduHeader.GetEndIndicator() == false)
    {
        NS_LOG_INFO("CONTINUATION PPDU received");
 
        // Previous fragment found
        if (m_currRxPacketFragment && ppduHeader.GetFragmentId() == m_currRxFragmentId)
        {
            m_currRxPacketFragmentBytes += ppduHeader.GetPPduLength();
            m_currRxPacketFragment->AddAtEnd(p);
        }
        else
        {
            Reset();
            NS_LOG_INFO(
                "CONTINUATION PPDU received while the START of the PPDU may have been lost");
        }
    }
 
    // END_PPDU
    else if (ppduHeader.GetStartIndicator() == false && ppduHeader.GetEndIndicator() == true)
    {
        NS_LOG_INFO("END PPDU received");
 
        // Previous fragment found
        if (m_currRxPacketFragment && ppduHeader.GetFragmentId() == m_currRxFragmentId)
        {
            m_currRxPacketFragmentBytes += ppduHeader.GetPPduLength();
 
            // The packet size is wrong!
            if (m_currRxPacketFragmentBytes != m_currRxPacketSize)
            {
                NS_LOG_INFO("END PDU received, but the packet size of the HL PDU is wrong. Drop "
                            "the HL packet!");
            }
            // Receive the HL packet here
            else
            {
                m_currRxPacketFragment->AddAtEnd(p);
                m_rxCallback(m_currRxPacketFragment, m_encapAddress, m_decapAddress);
            }
        }
        else
        {
            NS_LOG_INFO("END PPDU received while the START of the PPDU may have been lost");
        }
 
        // Reset anyway
        Reset();
    }
}
 
void
SatReturnLinkEncapsulator::ReceiveAck(Ptr<SatArqAckMessage> ack)
{
    NS_LOG_FUNCTION(this);
    NS_ASSERT(false);
 
}
 
void
SatReturnLinkEncapsulator::IncreaseFragmentId()
{
    NS_LOG_FUNCTION(this);
 
    ++m_txFragmentId;
    if (m_txFragmentId >= MAX_FRAGMENT_ID)
    {
        m_txFragmentId = 0;
    }
}
 
void
SatReturnLinkEncapsulator::Reset()
{
    NS_LOG_FUNCTION(this);
 
    m_currRxFragmentId = 0;
    m_currRxPacketSize = 0;
    m_currRxPacketFragment = 0;
    m_currRxPacketFragmentBytes = 0;
}
 
uint32_t
SatReturnLinkEncapsulator::GetMinTxOpportunityInBytes() const
{
    NS_LOG_FUNCTION(this);
 
    return m_minTxOpportunity;
}
 
} // namespace ns3