/src/PcapPlusPlus/Packet++/src/Packet.cpp

Source
#define LOG_MODULE PacketLogModulePacket

#include "Packet.h"
#include "EthLayer.h"
#include "EthDot3Layer.h"
#include "SllLayer.h"
#include "Sll2Layer.h"
#include "NflogLayer.h"
#include "NullLoopbackLayer.h"
#include "IPv4Layer.h"
#include "IPv6Layer.h"
#include "CiscoHdlcLayer.h"
#include "PayloadLayer.h"
#include "PacketTrailerLayer.h"
#include "Logger.h"
#include <numeric>
#include <sstream>
#include <memory>
#ifdef _MSC_VER
# include <time.h>
# include "SystemUtils.h"
#endif

namespace pcpp
{

  Packet::Packet(size_t maxPacketLen, LinkLayerType linkType)
      : m_RawPacket(nullptr), m_FirstLayer(nullptr), m_LastLayer(nullptr), m_MaxPacketLen(maxPacketLen),
        m_FreeRawPacket(true), m_CanReallocateData(true)
  {
    timeval time;
    gettimeofday(&time, nullptr);
    uint8_t* data = new uint8_t[maxPacketLen];
    memset(data, 0, maxPacketLen);
    m_RawPacket = new RawPacket(data, 0, time, true, linkType);
  }

  Packet::Packet(uint8_t* buffer, size_t bufferSize, LinkLayerType linkType)
      : m_RawPacket(nullptr), m_FirstLayer(nullptr), m_LastLayer(nullptr), m_MaxPacketLen(bufferSize),
        m_FreeRawPacket(true), m_CanReallocateData(false)
  {
    timeval time;
    gettimeofday(&time, nullptr);
    memset(buffer, 0, bufferSize);
    m_RawPacket = new RawPacket(buffer, 0, time, false, linkType);
  }

  void Packet::setRawPacket(RawPacket* rawPacket, bool freeRawPacket, ProtocolTypeFamily parseUntil,
                            OsiModelLayer parseUntilLayer)
  {
    destructPacketData();

    m_FirstLayer = nullptr;
    m_LastLayer = nullptr;
    m_MaxPacketLen = rawPacket->getRawDataLen();
    m_FreeRawPacket = freeRawPacket;
    m_RawPacket = rawPacket;
    m_CanReallocateData = true;

    if (m_RawPacket == nullptr)
      return;

    parsePacket(PacketParseOptions{ parseUntil, parseUntilLayer });
  }

  void Packet::parsePacket(PacketParseOptions options, bool incrementalParsing)
  {
    if (m_RawPacket == nullptr)
    {
      throw std::runtime_error("Cannot parse packet: RawPacket is null");
    }

    // If we aren't doing an incremental parse, destroy all existing layers and start from scratch
    if (!incrementalParsing)
    {
      destroyAllLayers();
    }

    // Flag indicating whether we are currently parsing new layers (as opposed to traversing already parsed ones).
    bool parsingNewLayers = false;

    // If there is no first layer, create it based on the link layer type
    if (m_FirstLayer == nullptr)
    {
      parsingNewLayers = true;

      LinkLayerType linkType = m_RawPacket->getLinkLayerType();
      m_FirstLayer = createFirstLayer(linkType);

      if (m_FirstLayer == nullptr)
      {
        PCPP_LOG_ERROR("Failed to create first layer! Possibly attempting to parse a RawPacket with no data.");
        return;
      }

      // Mark the first layer as allocated in the packet
      m_FirstLayer->m_AllocationInfo.ownedByPacket = true;
    }

    Layer* parseStartLayer = m_FirstLayer;

    // Fast path:
    //   If we are doing an incremental parse and we are not searching for a specific protocol type,
    //   we can directly start from the last parsed layer.
    if (m_LastLayer != nullptr && options.parseUntilProtocol == UnknownProtocol)
    {
      // NOTE: Potential edge case, PacketTrailerLayer is considered DataLinkLayer.
      //  If the user requested a higher OSI layer, this condition would not skip the parse.
      //  The parse should still do nothing, as the trailer layer doesn't have a next layer,
      //  but it will have to go through 1 extra iteration.
      if (m_LastLayer->getOsiModelLayer() > options.parseUntilLayer)
      {
        // Already past the OSI target layer, nothing to do
        return;
      }

      parseStartLayer = m_LastLayer;
    }

    // As the stop conditions are inclusive, the parse must go one layer further and then roll back if needed
    bool rollbackLastLayer = false;
    bool foundTargetProtocol = false;
    for (auto* curLayer = parseStartLayer; curLayer != nullptr; curLayer = curLayer->getNextLayer())
    {
      // If we are parsing new layers, update the last layer pointer
      // Otherwise we are just traversing already parsed layers
      if (parsingNewLayers)
      {
        // Mark the current layer as allocated in the packet, as it was just created
        curLayer->m_AllocationInfo.ownedByPacket = true;
        m_LastLayer = curLayer;
      }

      // If the current layer is of a higher OSI layer than the target, stop parsing
      if (curLayer->getOsiModelLayer() > options.parseUntilLayer)
      {
        // If we are traversing already parsed layers, we don't want to roll back as they must be kept as is.
        rollbackLastLayer = parsingNewLayers;
        break;
      }

      // If we are searching for a specific layer protocol, record when we find at least one target.
      const bool matchesTarget = curLayer->isMemberOfProtocolFamily(options.parseUntilProtocol);
      if (options.parseUntilProtocol != UnknownProtocol && matchesTarget)
      {
        foundTargetProtocol = true;
      }

      // If we have found the target protocol already, we are parsing until we find a different protocol
      if (foundTargetProtocol && !matchesTarget)
      {
        // If we are traversing already parsed layers, we don't want to roll back as they must be kept as is.
        rollbackLastLayer = parsingNewLayers;
        break;
      }

      // If the current layer doesn't have a next layer yet, parse it.
      // This is important for the case of a re-parse where some layers may already have been parsed
      if (!curLayer->hasNextLayer())
      {
        parsingNewLayers = true;  // We are now parsing new layers.

        // Parse the next layer. This will update the next layer pointer of the current layer.
        curLayer->parseNextLayer();
      }
    }

    // Roll back one layer, if parsing with search condition as the conditions are inclusive.
    // Don't delete the first layer. If already past the target layer, treat the same as if the layer was found.
    if (rollbackLastLayer && m_LastLayer != m_FirstLayer)
    {
      m_LastLayer = m_LastLayer->getPrevLayer();
      delete m_LastLayer->m_NextLayer;
      m_LastLayer->m_NextLayer = nullptr;
    }

    // If there is data left in the raw packet that doesn't belong to any layer, create a PacketTrailerLayer
    if (m_LastLayer != nullptr && options.parseUntilProtocol == UnknownProtocol &&
        options.parseUntilLayer == OsiModelLayerUnknown)
    {
      // find if there is data left in the raw packet that doesn't belong to any layer. In that case it's probably
      // a packet trailer. create a PacketTrailerLayer layer and add it at the end of the packet
      int trailerLen = (int)((m_RawPacket->getRawData() + m_RawPacket->getRawDataLen()) -
                             (m_LastLayer->getData() + m_LastLayer->getDataLen()));
      if (trailerLen > 0)
      {
        PacketTrailerLayer* trailerLayer =
            new PacketTrailerLayer(static_cast<uint8_t*>(m_LastLayer->getData() + m_LastLayer->getDataLen()),
                                   trailerLen, m_LastLayer, this);

        trailerLayer->m_AllocationInfo.ownedByPacket = true;
        m_LastLayer->setNextLayer(trailerLayer);
        m_LastLayer = trailerLayer;
      }
    }
  }

  Packet::Packet(RawPacket* rawPacket, bool freeRawPacket, ProtocolType parseUntil, OsiModelLayer parseUntilLayer)
  {
    m_FreeRawPacket = false;
    m_RawPacket = nullptr;
    m_FirstLayer = nullptr;
    setRawPacket(rawPacket, freeRawPacket, parseUntil, parseUntilLayer);
  }

  Packet::Packet(RawPacket* rawPacket, ProtocolType parseUntil)
  {
    m_FreeRawPacket = false;
    m_RawPacket = nullptr;
    m_FirstLayer = nullptr;
    auto parseUntilFamily = static_cast<ProtocolTypeFamily>(parseUntil);
    setRawPacket(rawPacket, false, parseUntilFamily, OsiModelLayerUnknown);
  }

  Packet::Packet(RawPacket* rawPacket, ProtocolTypeFamily parseUntilFamily)
  {
    m_FreeRawPacket = false;
    m_RawPacket = nullptr;
    m_FirstLayer = nullptr;
    setRawPacket(rawPacket, false, parseUntilFamily, OsiModelLayerUnknown);
  }

  Packet::Packet(RawPacket* rawPacket, OsiModelLayer parseUntilLayer)
  {
    m_FreeRawPacket = false;
    m_RawPacket = nullptr;
    m_FirstLayer = nullptr;
    setRawPacket(rawPacket, false, UnknownProtocol, parseUntilLayer);
  }

  void Packet::destructPacketData()
  {
    destroyAllLayers();

    if (m_RawPacket != nullptr && m_FreeRawPacket)
    {
      delete m_RawPacket;
    }
  }

  void Packet::destroyAllLayers()
  {
    Layer* curLayer = m_FirstLayer;
    while (curLayer != nullptr)
    {
      Layer* nextLayer = curLayer->getNextLayer();
      if (curLayer->m_AllocationInfo.ownedByPacket)
      {
        delete curLayer;
      }

      curLayer = nextLayer;
    }

    m_FirstLayer = nullptr;
    m_LastLayer = nullptr;
  }

  Packet& Packet::operator=(const Packet& other)
  {
    destructPacketData();

    copyDataFrom(other);

    return *this;
  }

  void Packet::copyDataFrom(const Packet& other)
  {
    m_RawPacket = new RawPacket(*(other.m_RawPacket));
    m_FreeRawPacket = true;
    m_MaxPacketLen = other.m_MaxPacketLen;
    m_FirstLayer = createFirstLayer(m_RawPacket->getLinkLayerType());
    m_LastLayer = m_FirstLayer;
    m_CanReallocateData = true;
    Layer* curLayer = m_FirstLayer;
    while (curLayer != nullptr)
    {
      curLayer->parseNextLayer();
      curLayer->m_AllocationInfo.ownedByPacket = true;
      curLayer = curLayer->getNextLayer();
      if (curLayer != nullptr)
        m_LastLayer = curLayer;
    }
  }

  void Packet::reallocateRawData(size_t newSize)
  {
    PCPP_LOG_DEBUG("Allocating packet to new size: " << newSize);

    // allocate a new array with size newSize
    m_MaxPacketLen = newSize;

    // set the new array to RawPacket
    if (!m_RawPacket->reallocateData(m_MaxPacketLen))
    {
      PCPP_LOG_ERROR("Couldn't reallocate data of raw packet to " << m_MaxPacketLen << " bytes");
      return;
    }

    // set all data pointers in layers to the new array address
    const uint8_t* dataPtr = m_RawPacket->getRawData();

    for (Layer* curLayer = m_FirstLayer; curLayer != nullptr; curLayer = curLayer->getNextLayer())
    {
      PCPP_LOG_DEBUG("Setting new data pointer to layer '" << typeid(curLayer).name() << "'");
      curLayer->m_Data = const_cast<uint8_t*>(dataPtr);
      dataPtr += curLayer->getHeaderLen();
    }
  }

  bool Packet::insertLayer(Layer* prevLayer, Layer* newLayer, bool ownInPacket)
  {
    if (newLayer == nullptr)
    {
      PCPP_LOG_ERROR("Layer to add is nullptr");
      return false;
    }

    if (newLayer->isAllocatedToPacket())
    {
      PCPP_LOG_ERROR("Layer is already allocated to another packet. Cannot use layer in more than one packet");
      return false;
    }

    if (prevLayer != nullptr && prevLayer->getProtocol() == PacketTrailer)
    {
      PCPP_LOG_ERROR("Cannot insert layer after packet trailer");
      return false;
    }

    size_t newLayerHeaderLen = newLayer->getHeaderLen();
    if (m_RawPacket->getRawDataLen() + newLayerHeaderLen > m_MaxPacketLen)
    {
      if (!m_CanReallocateData)
      {
        PCPP_LOG_ERROR("With the new layer the packet will exceed the size of the pre-allocated buffer: "
                       << m_MaxPacketLen << " bytes");
        return false;
      }
      // reallocate to maximum value of: twice the max size of the packet or max size + new required length
      if (m_RawPacket->getRawDataLen() + newLayerHeaderLen > m_MaxPacketLen * 2)
        reallocateRawData(m_RawPacket->getRawDataLen() + newLayerHeaderLen + m_MaxPacketLen);
      else
        reallocateRawData(m_MaxPacketLen * 2);
    }

    // insert layer data to raw packet
    int indexToInsertData = 0;
    if (prevLayer != nullptr)
      indexToInsertData = prevLayer->m_Data + prevLayer->getHeaderLen() - m_RawPacket->getRawData();
    m_RawPacket->insertData(indexToInsertData, newLayer->m_Data, newLayerHeaderLen);

    // delete previous layer data
    delete[] newLayer->m_Data;

    // add layer to layers linked list
    if (prevLayer != nullptr)
    {
      newLayer->setNextLayer(prevLayer->getNextLayer());
      newLayer->setPrevLayer(prevLayer);
      prevLayer->setNextLayer(newLayer);
    }
    else  // prevLayer == nullptr
    {
      newLayer->setNextLayer(m_FirstLayer);
      if (m_FirstLayer != nullptr)
        m_FirstLayer->setPrevLayer(newLayer);
      m_FirstLayer = newLayer;
    }

    if (newLayer->getNextLayer() == nullptr)
      m_LastLayer = newLayer;
    else
      newLayer->getNextLayer()->setPrevLayer(newLayer);

    // Attach the layer to this packet. If ownInPacket is true, transfer ownership of the layer to the packet.
    newLayer->m_AllocationInfo.attachPacket(this, ownInPacket);

    // re-calculate all layers data ptr and data length

    // first, get ptr and data length of the raw packet
    const uint8_t* dataPtr = m_RawPacket->getRawData();
    size_t dataLen = static_cast<size_t>(m_RawPacket->getRawDataLen());

    // if a packet trailer exists, get its length
    size_t packetTrailerLen = 0;
    if (m_LastLayer != nullptr && m_LastLayer->getProtocol() == PacketTrailer)
      packetTrailerLen = m_LastLayer->getDataLen();

    // go over all layers from the first layer to the last layer and set the data ptr and data length for each one
    for (Layer* curLayer = m_FirstLayer; curLayer != nullptr; curLayer = curLayer->getNextLayer())
    {
      // set data ptr to layer
      curLayer->m_Data = const_cast<uint8_t*>(dataPtr);

      // there is an assumption here that the packet trailer, if exists, corresponds to the L2 (data link) layers.
      // so if there is a packet trailer and this layer is L2 (data link), set its data length to contain the
      // whole data, including the packet trailer. If this layer is L3-7, exclude the packet trailer from its data
      // length
      if (curLayer->getOsiModelLayer() == OsiModelDataLinkLayer)
        curLayer->m_DataLen = dataLen;
      else
        curLayer->m_DataLen = dataLen - packetTrailerLen;

      // advance data ptr and data length
      dataPtr += curLayer->getHeaderLen();
      dataLen -= curLayer->getHeaderLen();
    }

    return true;
  }

  bool Packet::removeLayer(ProtocolType layerType, int index)
  {
    Layer* layerToRemove = getLayerOfType(layerType, index);

    if (layerToRemove != nullptr)
    {
      return removeLayer(layerToRemove, true);
    }
    else
    {
      PCPP_LOG_ERROR("Layer of the requested type was not found in packet");
      return false;
    }
  }

  bool Packet::removeFirstLayer()
  {
    Layer* firstLayer = getFirstLayer();
    if (firstLayer == nullptr)
    {
      PCPP_LOG_ERROR("Packet has no layers");
      return false;
    }

    return removeLayer(firstLayer, true);
  }

  bool Packet::removeLastLayer()
  {
    Layer* lastLayer = getLastLayer();
    if (lastLayer == nullptr)
    {
      PCPP_LOG_ERROR("Packet has no layers");
      return false;
    }

    return removeLayer(lastLayer, true);
  }

  bool Packet::removeAllLayersAfter(Layer* layer)
  {
    Layer* curLayer = layer->getNextLayer();
    while (curLayer != nullptr)
    {
      Layer* tempLayer = curLayer->getNextLayer();
      if (!removeLayer(curLayer, true))
        return false;
      curLayer = tempLayer;
    }

    return true;
  }

  Layer* Packet::detachLayer(ProtocolType layerType, int index)
  {
    Layer* layerToDetach = getLayerOfType(layerType, index);

    if (layerToDetach != nullptr)
    {
      if (removeLayer(layerToDetach, false))
        return layerToDetach;
      else
        return nullptr;
    }
    else
    {
      PCPP_LOG_ERROR("Layer of the requested type was not found in packet");
      return nullptr;
    }
  }

  bool Packet::removeLayer(Layer* layer, bool tryToDelete)
  {
    if (layer == nullptr)
    {
      PCPP_LOG_ERROR("Layer is nullptr");
      return false;
    }

    // verify layer is allocated to a packet
    if (!layer->isAllocatedToPacket())
    {
      PCPP_LOG_ERROR("Layer isn't allocated to any packet");
      return false;
    }

    // verify layer is allocated to *this* packet
    Layer* curLayer = layer;
    while (curLayer->m_PrevLayer != nullptr)
      curLayer = curLayer->m_PrevLayer;
    if (curLayer != m_FirstLayer)
    {
      PCPP_LOG_ERROR("Layer isn't allocated to this packet");
      return false;
    }

    // before removing the layer's data, copy it so it can be later assigned as the removed layer's data
    size_t headerLen = layer->getHeaderLen();
    size_t layerOldDataSize = headerLen;
    auto layerOldData = std::make_unique<uint8_t[]>(layerOldDataSize);
    memcpy(layerOldData.get(), layer->m_Data, layerOldDataSize);

    // remove data from raw packet
    size_t numOfBytesToRemove = headerLen;
    int indexOfDataToRemove = layer->m_Data - m_RawPacket->getRawData();
    if (!m_RawPacket->removeData(indexOfDataToRemove, numOfBytesToRemove))
    {
      PCPP_LOG_ERROR("Couldn't remove data from packet");
      return false;
    }

    // remove layer from layers linked list
    if (layer->m_PrevLayer != nullptr)
      layer->m_PrevLayer->setNextLayer(layer->m_NextLayer);
    if (layer->m_NextLayer != nullptr)
      layer->m_NextLayer->setPrevLayer(layer->m_PrevLayer);

    // take care of head and tail ptrs
    if (m_FirstLayer == layer)
      m_FirstLayer = layer->m_NextLayer;
    if (m_LastLayer == layer)
      m_LastLayer = layer->m_PrevLayer;
    layer->setNextLayer(nullptr);
    layer->setPrevLayer(nullptr);

    // get packet trailer len if exists
    size_t packetTrailerLen = 0;
    if (m_LastLayer != nullptr && m_LastLayer->getProtocol() == PacketTrailer)
      packetTrailerLen = m_LastLayer->getDataLen();

    // re-calculate all layers data ptr and data length

    // first, get ptr and data length of the raw packet
    const uint8_t* dataPtr = m_RawPacket->getRawData();
    size_t dataLen = static_cast<size_t>(m_RawPacket->getRawDataLen());

    curLayer = m_FirstLayer;

    // go over all layers from the first layer to the last layer and set the data ptr and data length for each one
    while (curLayer != nullptr)
    {
      // set data ptr to layer
      curLayer->m_Data = const_cast<uint8_t*>(dataPtr);

      // there is an assumption here that the packet trailer, if exists, corresponds to the L2 (data link) layers.
      // so if there is a packet trailer and this layer is L2 (data link), set its data length to contain the
      // whole data, including the packet trailer. If this layer is L3-7, exclude the packet trailer from its data
      // length
      if (curLayer->getOsiModelLayer() == OsiModelDataLinkLayer)
        curLayer->m_DataLen = dataLen;
      else
        curLayer->m_DataLen = dataLen - packetTrailerLen;

      // advance data ptr and data length
      dataPtr += curLayer->getHeaderLen();
      dataLen -= curLayer->getHeaderLen();

      // move to next layer
      curLayer = curLayer->getNextLayer();
    }

    // if layer was allocated by this packet and tryToDelete flag is set, delete it
    if (tryToDelete && layer->m_AllocationInfo.ownedByPacket)
    {
      delete layer;
    }
    // if layer was not allocated by this packet or the tryToDelete is not set, detach it from the packet so it can
    // be reused
    else
    {
      layer->m_AllocationInfo.detach();
      layer->m_Data = layerOldData.release();
      layer->m_DataLen = layerOldDataSize;
    }

    return true;
  }

  Layer* Packet::getLayerOfType(ProtocolType layerType, int index) const
  {
    int curIndex = 0;
    for (Layer* curLayer = getFirstLayer(); curLayer != nullptr; curLayer = curLayer->getNextLayer())
    {
      if (curLayer->getProtocol() != layerType)
        continue;

      if (curIndex == index)
        return curLayer;

      curIndex++;
    }

    return nullptr;
  }

  bool Packet::isPacketOfType(ProtocolType protocolType) const
  {
    for (Layer* curLayer = getFirstLayer(); curLayer != nullptr; curLayer = curLayer->getNextLayer())
    {
      if (curLayer->getProtocol() == protocolType)
      {
        return true;
      }
    }

    return false;
  }

  bool Packet::isPacketOfType(ProtocolTypeFamily protocolTypeFamily) const
  {
    Layer* curLayer = getFirstLayer();
    while (curLayer != nullptr)
    {
      if (curLayer->isMemberOfProtocolFamily(protocolTypeFamily))
      {
        return true;
      }
      curLayer = curLayer->getNextLayer();
    }

    return false;
  }

  bool Packet::extendLayer(Layer* layer, int offsetInLayer, size_t numOfBytesToExtend)
  {
    if (layer == nullptr)
    {
      PCPP_LOG_ERROR("Layer is nullptr");
      return false;
    }

    // verify layer is allocated to this packet
    if (!(layer->getAttachedPacket() == this))
    {
      PCPP_LOG_ERROR("Layer isn't allocated to this packet");
      return false;
    }

    if (m_RawPacket->getRawDataLen() + numOfBytesToExtend > m_MaxPacketLen)
    {
      if (!m_CanReallocateData)
      {
        PCPP_LOG_ERROR(
            "With the layer extended size the packet will exceed the size of the pre-allocated buffer: "
            << m_MaxPacketLen << " bytes");
        return false;
      }
      // reallocate to maximum value of: twice the max size of the packet or max size + new required length
      if (m_RawPacket->getRawDataLen() + numOfBytesToExtend > m_MaxPacketLen * 2)
        reallocateRawData(m_RawPacket->getRawDataLen() + numOfBytesToExtend + m_MaxPacketLen);
      else
        reallocateRawData(m_MaxPacketLen * 2);
    }

    // insert layer data to raw packet
    int indexToInsertData = layer->m_Data + offsetInLayer - m_RawPacket->getRawData();
    // passing nullptr to insertData will move the data by numOfBytesToExtend
    // no new data has to be created for this insertion which saves at least little time
    // this move operation occurs on already allocated memory, which is backed by the reallocation if's provided
    // above if offsetInLayer == layer->getHeaderLen() insertData will not move any data but only increase the
    // packet size by numOfBytesToExtend
    m_RawPacket->insertData(indexToInsertData, nullptr, numOfBytesToExtend);

    // re-calculate all layers data ptr and data length
    const uint8_t* dataPtr = m_RawPacket->getRawData();

    // go over all layers from the first layer to the last layer and set the data ptr and data length for each layer
    bool passedExtendedLayer = false;
    for (Layer* curLayer = m_FirstLayer; curLayer != nullptr; curLayer = curLayer->getNextLayer())
    {
      if (dataPtr > m_RawPacket->getRawData() + m_RawPacket->getRawDataLen())
      {
        PCPP_LOG_ERROR("Layer data pointer exceeds packet's boundary");
        return false;
      }

      // set the data ptr
      curLayer->m_Data = const_cast<uint8_t*>(dataPtr);

      // set a flag if arrived to the layer being extended
      if (curLayer->getPrevLayer() == layer)
        passedExtendedLayer = true;

      // change the data length only for layers who come before the extended layer. For layers who come after,
      // data length isn't changed
      if (!passedExtendedLayer)
        curLayer->m_DataLen += numOfBytesToExtend;

      // assuming header length of the layer that requested to be extended hasn't been enlarged yet
      size_t headerLen = curLayer->getHeaderLen() + (curLayer == layer ? numOfBytesToExtend : 0);
      dataPtr += headerLen;
    }

    return true;
  }

  bool Packet::shortenLayer(Layer* layer, int offsetInLayer, size_t numOfBytesToShorten)
  {
    if (layer == nullptr)
    {
      PCPP_LOG_ERROR("Layer is nullptr");
      return false;
    }

    // verify layer is allocated to this packet
    if (!(layer->getAttachedPacket() == this))
    {
      PCPP_LOG_ERROR("Layer isn't allocated to this packet");
      return false;
    }

    // remove data from raw packet
    int indexOfDataToRemove = layer->m_Data + offsetInLayer - m_RawPacket->getRawData();
    if (!m_RawPacket->removeData(indexOfDataToRemove, numOfBytesToShorten))
    {
      PCPP_LOG_ERROR("Couldn't remove data from packet");
      return false;
    }

    // re-calculate all layers data ptr and data length
    const uint8_t* dataPtr = m_RawPacket->getRawData();

    // go over all layers from the first layer to the last layer and set the data ptr and data length for each layer
    Layer* curLayer = m_FirstLayer;
    bool passedExtendedLayer = false;
    while (curLayer != nullptr)
    {
      if (dataPtr > m_RawPacket->getRawData() + m_RawPacket->getRawDataLen())
      {
        PCPP_LOG_ERROR("Layer data pointer exceeds packet's boundary");
        return false;
      }

      // set the data ptr
      curLayer->m_Data = const_cast<uint8_t*>(dataPtr);

      // set a flag if arrived to the layer being shortened
      if (curLayer->getPrevLayer() == layer)
        passedExtendedLayer = true;

      size_t headerLen = curLayer->getHeaderLen();

      // change the data length only for layers who come before the shortened layer. For layers who come after,
      // data length isn't changed
      if (!passedExtendedLayer)
        curLayer->m_DataLen -= numOfBytesToShorten;

      // assuming header length of the layer that requested to be extended hasn't been enlarged yet
      headerLen -= (curLayer == layer ? numOfBytesToShorten : 0);
      dataPtr += headerLen;
      curLayer = curLayer->getNextLayer();
    }

    return true;
  }

  void Packet::computeCalculateFields()
  {
    // calculated fields should be calculated from top layer to bottom layer
    for (Layer* curLayer = m_LastLayer; curLayer != nullptr; curLayer = curLayer->getPrevLayer())
    {
      curLayer->computeCalculateFields();
    }
  }

  std::string Packet::printPacketInfo(bool timeAsLocalTime) const
  {
    std::ostringstream dataLenStream;
    dataLenStream << m_RawPacket->getRawDataLen();

    // convert raw packet timestamp to printable format
    timespec timestamp = m_RawPacket->getPacketTimeStamp();
    time_t nowtime = timestamp.tv_sec;
    struct tm* nowtm = nullptr;
#if __cplusplus > 199711L && !defined(_WIN32)
    // localtime_r and gmtime_r are thread-safe versions of localtime and gmtime,
    // but they're defined only in newer compilers (>= C++0x).
    // on Windows localtime and gmtime are already thread-safe so there is not need
    // to use localtime_r and gmtime_r
    struct tm nowtm_r;
    if (timeAsLocalTime)
      nowtm = localtime_r(&nowtime, &nowtm_r);
    else
      nowtm = gmtime_r(&nowtime, &nowtm_r);

    if (nowtm != nullptr)
      nowtm = &nowtm_r;
#else
    // on Window compilers localtime and gmtime are already thread safe.
    // in old compilers (< C++0x) gmtime_r and localtime_r were not defined so we have to fall back to localtime and
    // gmtime
    if (timeAsLocalTime)
      nowtm = localtime(&nowtime);
    else
      nowtm = gmtime(&nowtime);
#endif

    char buf[128];
    if (nowtm != nullptr)
    {
      char tmbuf[64];
      strftime(tmbuf, sizeof(tmbuf), "%Y-%m-%d %H:%M:%S", nowtm);
      snprintf(buf, sizeof(buf), "%s.%09lu", tmbuf, (unsigned long)timestamp.tv_nsec);
    }
    else
      snprintf(buf, sizeof(buf), "0000-00-00 00:00:00.000000000");

    return "Packet length: " + dataLenStream.str() + " [Bytes], Arrival time: " + std::string(buf);
  }

  Layer* Packet::createFirstLayer(LinkLayerType linkType)
  {
    size_t rawDataLen = (size_t)m_RawPacket->getRawDataLen();
    if (rawDataLen == 0)
      return nullptr;

    const uint8_t* rawData = m_RawPacket->getRawData();

    switch (linkType)
    {
    case LinkLayerType::LINKTYPE_ETHERNET:
    {
      if (EthLayer::isDataValid(rawData, rawDataLen))
      {
        return new EthLayer(const_cast<uint8_t*>(rawData), rawDataLen, this);
      }
      if (EthDot3Layer::isDataValid(rawData, rawDataLen))
      {
        return new EthDot3Layer(const_cast<uint8_t*>(rawData), rawDataLen, this);
      }
      break;
    }
    case LinkLayerType::LINKTYPE_LINUX_SLL:
    {
      return new SllLayer(const_cast<uint8_t*>(rawData), rawDataLen, this);
    }
    case LinkLayerType::LINKTYPE_LINUX_SLL2:
    {
      if (Sll2Layer::isDataValid(rawData, rawDataLen))
      {
        return new Sll2Layer(const_cast<uint8_t*>(rawData), rawDataLen, this);
      }
      break;
    }
    case LinkLayerType::LINKTYPE_NULL:
    {
      if (NullLoopbackLayer::isDataValid(rawData, rawDataLen))
      {
        return new NullLoopbackLayer(const_cast<uint8_t*>(rawData), rawDataLen, this);
      }
      break;
    }
    case LinkLayerType::LINKTYPE_RAW:
    case LinkLayerType::LINKTYPE_DLT_RAW1:
    case LinkLayerType::LINKTYPE_DLT_RAW2:
    {
      uint8_t ipVer = rawData[0] & 0xf0;
      if (ipVer == 0x40 && IPv4Layer::isDataValid(rawData, rawDataLen))
      {
        return new IPv4Layer(const_cast<uint8_t*>(rawData), rawDataLen, nullptr, this);
      }
      if (ipVer == 0x60 && IPv6Layer::isDataValid(rawData, rawDataLen))
      {
        return new IPv6Layer(const_cast<uint8_t*>(rawData), rawDataLen, nullptr, this);
      }
      break;
    }
    case LinkLayerType::LINKTYPE_IPV4:
    {
      if (IPv4Layer::isDataValid(rawData, rawDataLen))
      {
        return new IPv4Layer(const_cast<uint8_t*>(rawData), rawDataLen, nullptr, this);
      }
      break;
    }
    case LinkLayerType::LINKTYPE_IPV6:
    {
      if (IPv6Layer::isDataValid(rawData, rawDataLen))
      {
        return new IPv6Layer(const_cast<uint8_t*>(rawData), rawDataLen, nullptr, this);
      }
      break;
    }
    case LinkLayerType::LINKTYPE_NFLOG:
    {
      if (NflogLayer::isDataValid(rawData, rawDataLen))
      {
        return new NflogLayer(const_cast<uint8_t*>(rawData), rawDataLen, this);
      }
      break;
    }
    case LinkLayerType::LINKTYPE_C_HDLC:
    {
      if (CiscoHdlcLayer::isDataValid(rawData, rawDataLen))
      {
        return new CiscoHdlcLayer(const_cast<uint8_t*>(rawData), rawDataLen, this);
      }
      break;
    }
    default:
      // For all other link types, we don't have a specific layer. Just break and create a PayloadLayer
      break;
    }

    // unknown link type
    return new PayloadLayer(const_cast<uint8_t*>(rawData), rawDataLen, nullptr, this);
  }

  std::string Packet::toString(bool timeAsLocalTime) const
  {
    std::vector<std::string> stringList;
    toStringList(stringList, timeAsLocalTime);
    return std::accumulate(stringList.begin(), stringList.end(), std::string(),
                           [](std::string a, const std::string& b) { return std::move(a) + b + '\n'; });
  }

  void Packet::toStringList(std::vector<std::string>& result, bool timeAsLocalTime) const
  {
    result.clear();
    result.push_back(printPacketInfo(timeAsLocalTime));

    for (Layer* curLayer = m_FirstLayer; curLayer != nullptr; curLayer = curLayer->getNextLayer())
    {
      result.push_back(curLayer->toString());
    }
  }

}  // namespace pcpp

Coverage Report

Created: 2026-02-14 06:19