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

Source
#define LOG_MODULE PacketLogModuleDnsLayer

#include "DnsLayer.h"
#include "Logger.h"
#include <sstream>
#include "EndianPortable.h"

namespace pcpp
{

  // ~~~~~~~~
  // DnsLayer
  // ~~~~~~~~

  DnsLayer::DnsLayer(uint8_t* data, size_t dataLen, Layer* prevLayer, Packet* packet)
      : Layer(data, dataLen, prevLayer, packet)
  {
    init(0, true);
  }

  DnsLayer::DnsLayer()
  {
    initNewLayer(0);
  }

  DnsLayer::DnsLayer(const DnsLayer& other) : Layer(other)
  {
    init(other.m_OffsetAdjustment, true);
  }

  DnsLayer::DnsLayer(uint8_t* data, size_t dataLen, Layer* prevLayer, Packet* packet, size_t offsetAdjustment)
      : Layer(data, dataLen, prevLayer, packet)
  {
    init(offsetAdjustment, true);
  }

  DnsLayer::DnsLayer(size_t offsetAdjustment)
  {
    initNewLayer(offsetAdjustment);
  }

  DnsLayer& DnsLayer::operator=(const DnsLayer& other)
  {
    Layer::operator=(other);

    IDnsResource* curResource = m_ResourceList;
    while (curResource != nullptr)
    {
      IDnsResource* temp = curResource->getNextResource();
      delete curResource;
      curResource = temp;
    }

    init(other.m_OffsetAdjustment, true);

    return (*this);
  }

  DnsLayer::~DnsLayer()
  {
    IDnsResource* curResource = m_ResourceList;
    while (curResource != nullptr)
    {
      IDnsResource* nextResource = curResource->getNextResource();
      delete curResource;
      curResource = nextResource;
    }
  }

  void DnsLayer::init(size_t offsetAdjustment, bool callParseResource)
  {
    m_OffsetAdjustment = offsetAdjustment;
    m_Protocol = DNS;
    m_ResourceList = nullptr;

    m_FirstQuery = nullptr;
    m_FirstAnswer = nullptr;
    m_FirstAuthority = nullptr;
    m_FirstAdditional = nullptr;

    if (callParseResource)
      parseResources();
  }

  void DnsLayer::initNewLayer(size_t offsetAdjustment)
  {
    m_OffsetAdjustment = offsetAdjustment;
    const size_t headerLen = getBasicHeaderSize();
    allocData(headerLen);

    init(m_OffsetAdjustment, false);
  }

  size_t DnsLayer::getBasicHeaderSize()
  {
    return sizeof(dnshdr) + m_OffsetAdjustment;
  }

  dnshdr* DnsLayer::getDnsHeader() const
  {
    uint8_t* ptr = m_Data + m_OffsetAdjustment;
    return reinterpret_cast<dnshdr*>(ptr);
  }

  bool DnsLayer::extendLayer(int offsetInLayer, size_t numOfBytesToExtend, IDnsResource* resource)
  {
    if (!Layer::extendLayer(offsetInLayer, numOfBytesToExtend))
      return false;

    IDnsResource* curResource = resource->getNextResource();
    while (curResource != nullptr)
    {
      curResource->m_OffsetInLayer += numOfBytesToExtend;
      curResource = curResource->getNextResource();
    }
    return true;
  }

  bool DnsLayer::shortenLayer(int offsetInLayer, size_t numOfBytesToShorten, IDnsResource* resource)
  {
    if (!Layer::shortenLayer(offsetInLayer, numOfBytesToShorten))
      return false;

    IDnsResource* curResource = resource->getNextResource();
    while (curResource != nullptr)
    {
      curResource->m_OffsetInLayer -= numOfBytesToShorten;
      curResource = curResource->getNextResource();
    }
    return true;
  }

  void DnsLayer::parseResources()
  {
    size_t offsetInPacket = getBasicHeaderSize();
    IDnsResource* curResource = m_ResourceList;

    uint16_t numOfQuestions = be16toh(getDnsHeader()->numberOfQuestions);
    uint16_t numOfAnswers = be16toh(getDnsHeader()->numberOfAnswers);
    uint16_t numOfAuthority = be16toh(getDnsHeader()->numberOfAuthority);
    uint16_t numOfAdditional = be16toh(getDnsHeader()->numberOfAdditional);

    uint32_t numOfOtherResources = numOfQuestions + numOfAnswers + numOfAuthority + numOfAdditional;

    if (numOfOtherResources > 300)
    {
      PCPP_LOG_ERROR(
          "DNS layer contains more than 300 resources, probably a bad packet. Skipping parsing DNS resources");
      return;
    }

    for (uint32_t i = 0; i < numOfOtherResources; i++)
    {
      DnsResourceType resType;
      if (numOfQuestions > 0)
      {
        resType = DnsQueryType;
        numOfQuestions--;
      }
      else if (numOfAnswers > 0)
      {
        resType = DnsAnswerType;
        numOfAnswers--;
      }
      else if (numOfAuthority > 0)
      {
        resType = DnsAuthorityType;
        numOfAuthority--;
      }
      else
      {
        resType = DnsAdditionalType;
        numOfAdditional--;
      }

      DnsResource* newResource = nullptr;
      DnsQuery* newQuery = nullptr;
      IDnsResource* newGenResource = nullptr;
      if (resType == DnsQueryType)
      {
        newQuery = new DnsQuery(this, offsetInPacket);
        newGenResource = newQuery;
        offsetInPacket += newQuery->getSize();
      }
      else
      {
        newResource = new DnsResource(this, offsetInPacket, resType);
        newGenResource = newResource;
        offsetInPacket += newResource->getSize();
      }

      if (offsetInPacket > m_DataLen)
      {
        // Parse packet failed, DNS resource is out of bounds. Probably a bad packet
        delete newGenResource;
        return;
      }

      // this resource is the first resource
      if (m_ResourceList == nullptr)
      {
        m_ResourceList = newGenResource;
        curResource = m_ResourceList;
      }
      else
      {
        curResource->setNextResource(newGenResource);
        curResource = curResource->getNextResource();
      }

      if (resType == DnsQueryType && m_FirstQuery == nullptr)
        m_FirstQuery = newQuery;
      else if (resType == DnsAnswerType && m_FirstAnswer == nullptr)
        m_FirstAnswer = newResource;
      else if (resType == DnsAuthorityType && m_FirstAuthority == nullptr)
        m_FirstAuthority = newResource;
      else if (resType == DnsAdditionalType && m_FirstAdditional == nullptr)
        m_FirstAdditional = newResource;
    }
  }

  IDnsResource* DnsLayer::getResourceByName(IDnsResource* startFrom, size_t resourceCount, const std::string& name,
                                            bool exactMatch) const
  {
    size_t index = 0;
    while (index < resourceCount)
    {
      if (startFrom == nullptr)
        return nullptr;

      std::string resourceName = startFrom->getName();
      if (exactMatch && resourceName == name)
        return startFrom;
      else if (!exactMatch && resourceName.find(name) != std::string::npos)
        return startFrom;

      startFrom = startFrom->getNextResource();

      index++;
    }

    return nullptr;
  }

  DnsQuery* DnsLayer::getQuery(const std::string& name, bool exactMatch) const
  {
    uint16_t numOfQueries = be16toh(getDnsHeader()->numberOfQuestions);
    IDnsResource* res = getResourceByName(m_FirstQuery, numOfQueries, name, exactMatch);
    if (res != nullptr)
      return dynamic_cast<DnsQuery*>(res);
    return nullptr;
  }

  DnsQuery* DnsLayer::getFirstQuery() const
  {
    return m_FirstQuery;
  }

  DnsQuery* DnsLayer::getNextQuery(DnsQuery* query) const
  {
    if (query == nullptr || query->getNextResource() == nullptr || query->getType() != DnsQueryType ||
        query->getNextResource()->getType() != DnsQueryType)
      return nullptr;

    return (DnsQuery*)(query->getNextResource());
  }

  size_t DnsLayer::getQueryCount() const
  {
    return be16toh(getDnsHeader()->numberOfQuestions);
  }

  DnsResource* DnsLayer::getAnswer(const std::string& name, bool exactMatch) const
  {
    uint16_t numOfAnswers = be16toh(getDnsHeader()->numberOfAnswers);
    IDnsResource* res = getResourceByName(m_FirstAnswer, numOfAnswers, name, exactMatch);
    if (res != nullptr)
      return dynamic_cast<DnsResource*>(res);
    return nullptr;
  }

  DnsResource* DnsLayer::getFirstAnswer() const
  {
    return m_FirstAnswer;
  }

  DnsResource* DnsLayer::getNextAnswer(DnsResource* answer) const
  {
    if (answer == nullptr || answer->getNextResource() == nullptr || answer->getType() != DnsAnswerType ||
        answer->getNextResource()->getType() != DnsAnswerType)
      return nullptr;

    return (DnsResource*)(answer->getNextResource());
  }

  size_t DnsLayer::getAnswerCount() const
  {
    return be16toh(getDnsHeader()->numberOfAnswers);
  }

  DnsResource* DnsLayer::getAuthority(const std::string& name, bool exactMatch) const
  {
    uint16_t numOfAuthorities = be16toh(getDnsHeader()->numberOfAuthority);
    IDnsResource* res = getResourceByName(m_FirstAuthority, numOfAuthorities, name, exactMatch);
    if (res != nullptr)
      return dynamic_cast<DnsResource*>(res);
    return nullptr;
  }

  DnsResource* DnsLayer::getFirstAuthority() const
  {
    return m_FirstAuthority;
  }

  DnsResource* DnsLayer::getNextAuthority(DnsResource* authority) const
  {
    if (authority == nullptr || authority->getNextResource() == nullptr ||
        authority->getType() != DnsAuthorityType || authority->getNextResource()->getType() != DnsAuthorityType)
      return nullptr;

    return (DnsResource*)(authority->getNextResource());
  }

  size_t DnsLayer::getAuthorityCount() const
  {
    return be16toh(getDnsHeader()->numberOfAuthority);
  }

  DnsResource* DnsLayer::getAdditionalRecord(const std::string& name, bool exactMatch) const
  {
    uint16_t numOfAdditionalRecords = be16toh(getDnsHeader()->numberOfAdditional);
    IDnsResource* res = getResourceByName(m_FirstAdditional, numOfAdditionalRecords, name, exactMatch);
    if (res != nullptr)
      return dynamic_cast<DnsResource*>(res);
    return nullptr;
  }

  DnsResource* DnsLayer::getFirstAdditionalRecord() const
  {
    return m_FirstAdditional;
  }

  DnsResource* DnsLayer::getNextAdditionalRecord(DnsResource* additionalRecord) const
  {
    if (additionalRecord == nullptr || additionalRecord->getNextResource() == nullptr ||
        additionalRecord->getType() != DnsAdditionalType ||
        additionalRecord->getNextResource()->getType() != DnsAdditionalType)
      return nullptr;

    return (DnsResource*)(additionalRecord->getNextResource());
  }

  size_t DnsLayer::getAdditionalRecordCount() const
  {
    return be16toh(getDnsHeader()->numberOfAdditional);
  }

  std::string DnsLayer::toString() const
  {
    std::ostringstream tidAsString;
    tidAsString << be16toh(getDnsHeader()->transactionID);

    std::ostringstream queryCount;
    queryCount << getQueryCount();

    std::ostringstream answerCount;
    answerCount << getAnswerCount();

    std::ostringstream authorityCount;
    authorityCount << getAuthorityCount();

    std::ostringstream additionalCount;
    additionalCount << getAdditionalRecordCount();

    if (getDnsHeader()->queryOrResponse == 1)
    {
      return "DNS query response, ID: " + tidAsString.str() + ";" + " queries: " + queryCount.str() +
             ", answers: " + answerCount.str() + ", authorities: " + authorityCount.str() +
             ", additional record: " + additionalCount.str();
    }
    else if (getDnsHeader()->queryOrResponse == 0)
    {
      return "DNS query, ID: " + tidAsString.str() + ";" + " queries: " + queryCount.str() +
             ", answers: " + answerCount.str() + ", authorities: " + authorityCount.str() +
             ", additional record: " + additionalCount.str();
    }
    else  // not likely - a DNS with no answers and no queries
    {
      return "DNS record without queries and answers, ID: " + tidAsString.str() + ";" +
             " queries: " + queryCount.str() + ", answers: " + answerCount.str() +
             ", authorities: " + authorityCount.str() + ", additional record: " + additionalCount.str();
    }
  }

  IDnsResource* DnsLayer::getFirstResource(DnsResourceType resType) const
  {
    switch (resType)
    {
    case DnsQueryType:
    {
      return m_FirstQuery;
    }
    case DnsAnswerType:
    {
      return m_FirstAnswer;
    }
    case DnsAuthorityType:
    {
      return m_FirstAuthority;
    }
    case DnsAdditionalType:
    {
      return m_FirstAdditional;
    }
    default:
      return nullptr;
    }
  }

  void DnsLayer::setFirstResource(DnsResourceType resType, IDnsResource* resource)
  {
    switch (resType)
    {
    case DnsQueryType:
    {
      m_FirstQuery = dynamic_cast<DnsQuery*>(resource);
      break;
    }
    case DnsAnswerType:
    {
      m_FirstAnswer = dynamic_cast<DnsResource*>(resource);
      break;
    }
    case DnsAuthorityType:
    {
      m_FirstAuthority = dynamic_cast<DnsResource*>(resource);
      break;
    }
    case DnsAdditionalType:
    {
      m_FirstAdditional = dynamic_cast<DnsResource*>(resource);
      break;
    }
    default:
      return;
    }
  }

  DnsResource* DnsLayer::addResource(DnsResourceType resType, const std::string& name, DnsType dnsType,
                                     DnsClass dnsClass, uint32_t ttl, IDnsResourceData* data)
  {
    // create new query on temporary buffer
    uint8_t newResourceRawData[4096];
    memset(newResourceRawData, 0, sizeof(newResourceRawData));

    DnsResource* newResource = new DnsResource(newResourceRawData, resType);

    newResource->setDnsClass(dnsClass);

    newResource->setDnsType(dnsType);

    // cannot return false since layer shouldn't be extended or shortened in this stage
    newResource->setName(name);

    newResource->setTTL(ttl);

    if (!newResource->setData(data))
    {
      delete newResource;
      PCPP_LOG_ERROR("Couldn't set new resource data");
      return nullptr;
    }

    size_t newResourceOffsetInLayer = getBasicHeaderSize();
    IDnsResource* curResource = m_ResourceList;
    while (curResource != nullptr && curResource->getType() <= resType)
    {
      newResourceOffsetInLayer += curResource->getSize();

      if (newResourceOffsetInLayer > m_DataLen)
      {
        // This possibly means that the DNS layer has been created from a malformed packet.
        PCPP_LOG_ERROR("Couldn't add resource! DNS Layer is malformed and contains out of bounds resources.");
        delete newResource;
        return nullptr;
      }

      IDnsResource* nextResource = curResource->getNextResource();
      if (nextResource == nullptr || nextResource->getType() > resType)
        break;
      curResource = nextResource;
    }

    // set next resource for new resource. This must happen here for extendLayer to succeed
    if (curResource != nullptr)
    {
      if (curResource->getType() > newResource->getType())
        newResource->setNextResource(m_ResourceList);
      else
        newResource->setNextResource(curResource->getNextResource());
    }
    else
    {
      // curResource != nullptr
      newResource->setNextResource(m_ResourceList);
    }

    // extend layer to make room for the new resource
    if (!extendLayer(newResourceOffsetInLayer, newResource->getSize(), newResource))
    {
      PCPP_LOG_ERROR("Couldn't extend DNS layer, addResource failed");
      delete newResource;
      return nullptr;
    }

    // connect the new resource to layer
    newResource->setDnsLayer(this, newResourceOffsetInLayer);

    // connect the new resource to the layer's resource list
    if (curResource != nullptr)
    {
      curResource->setNextResource(newResource);
      // this means the new resource is the first of it's type
      if (curResource->getType() < newResource->getType())
      {
        setFirstResource(resType, newResource);
      }
      // this means the new resource should be the first resource in the packet
      else if (curResource->getType() > newResource->getType())
      {
        m_ResourceList = newResource;

        setFirstResource(resType, newResource);
      }
    }
    else  // curResource != nullptr, meaning this is the first resource in layer
    {
      m_ResourceList = newResource;

      setFirstResource(resType, newResource);
    }

    return newResource;
  }

  DnsQuery* DnsLayer::addQuery(const std::string& name, DnsType dnsType, DnsClass dnsClass)
  {
    // create new query on temporary buffer
    uint8_t newQueryRawData[256];
    DnsQuery* newQuery = new DnsQuery(newQueryRawData);

    newQuery->setDnsClass(dnsClass);
    newQuery->setDnsType(dnsType);

    // cannot return false since layer shouldn't be extended or shortened in this stage
    newQuery->setName(name);

    // find the offset in the layer to insert the new query
    size_t newQueryOffsetInLayer = getBasicHeaderSize();
    DnsQuery* curQuery = getFirstQuery();
    while (curQuery != nullptr)
    {
      newQueryOffsetInLayer += curQuery->getSize();
      DnsQuery* nextQuery = getNextQuery(curQuery);
      if (nextQuery == nullptr)
        break;
      curQuery = nextQuery;
    }

    // set next resource for new query. This must happen here for extendLayer to succeed
    if (curQuery != nullptr)
      newQuery->setNextResource(curQuery->getNextResource());
    else
      newQuery->setNextResource(m_ResourceList);

    // extend layer to make room for the new query
    if (!extendLayer(newQueryOffsetInLayer, newQuery->getSize(), newQuery))
    {
      PCPP_LOG_ERROR("Couldn't extend DNS layer, addQuery failed");
      delete newQuery;
      return nullptr;
    }

    // connect the new query to layer
    newQuery->setDnsLayer(this, newQueryOffsetInLayer);

    // connect the new query to the layer's resource list
    if (curQuery != nullptr)
      curQuery->setNextResource(newQuery);
    else  // curQuery == nullptr, meaning this is the first query
    {
      m_ResourceList = newQuery;
      m_FirstQuery = newQuery;
    }

    // increase number of queries
    getDnsHeader()->numberOfQuestions = htobe16(getQueryCount() + 1);

    return newQuery;
  }

  DnsQuery* DnsLayer::addQuery(DnsQuery* const copyQuery)
  {
    if (copyQuery == nullptr)
      return nullptr;

    return addQuery(copyQuery->getName(), copyQuery->getDnsType(), copyQuery->getDnsClass());
  }

  bool DnsLayer::removeQuery(const std::string& queryNameToRemove, bool exactMatch)
  {
    DnsQuery* queryToRemove = getQuery(queryNameToRemove, exactMatch);
    if (queryToRemove == nullptr)
    {
      PCPP_LOG_DEBUG("Query not found");
      return false;
    }

    return removeQuery(queryToRemove);
  }

  bool DnsLayer::removeQuery(DnsQuery* queryToRemove)
  {
    bool res = removeResource(queryToRemove);
    if (res)
    {
      // decrease number of query records
      getDnsHeader()->numberOfQuestions = htobe16(getQueryCount() - 1);
    }

    return res;
  }

  DnsResource* DnsLayer::addAnswer(const std::string& name, DnsType dnsType, DnsClass dnsClass, uint32_t ttl,
                                   IDnsResourceData* data)
  {
    DnsResource* res = addResource(DnsAnswerType, name, dnsType, dnsClass, ttl, data);
    if (res != nullptr)
    {
      // increase number of answer records
      getDnsHeader()->numberOfAnswers = htobe16(getAnswerCount() + 1);
    }

    return res;
  }

  DnsResource* DnsLayer::addAnswer(DnsResource* const copyAnswer)
  {
    if (copyAnswer == nullptr)
      return nullptr;

    return addAnswer(copyAnswer->getName(), copyAnswer->getDnsType(), copyAnswer->getDnsClass(),
                     copyAnswer->getTTL(), copyAnswer->getData().get());
  }

  bool DnsLayer::removeAnswer(const std::string& answerNameToRemove, bool exactMatch)
  {
    DnsResource* answerToRemove = getAnswer(answerNameToRemove, exactMatch);
    if (answerToRemove == nullptr)
    {
      PCPP_LOG_DEBUG("Answer record not found");
      return false;
    }

    return removeAnswer(answerToRemove);
  }

  bool DnsLayer::removeAnswer(DnsResource* answerToRemove)
  {
    bool res = removeResource(answerToRemove);
    if (res)
    {
      // decrease number of answer records
      getDnsHeader()->numberOfAnswers = htobe16(getAnswerCount() - 1);
    }

    return res;
  }

  DnsResource* DnsLayer::addAuthority(const std::string& name, DnsType dnsType, DnsClass dnsClass, uint32_t ttl,
                                      IDnsResourceData* data)
  {
    DnsResource* res = addResource(DnsAuthorityType, name, dnsType, dnsClass, ttl, data);
    if (res != nullptr)
    {
      // increase number of authority records
      getDnsHeader()->numberOfAuthority = htobe16(getAuthorityCount() + 1);
    }

    return res;
  }

  DnsResource* DnsLayer::addAuthority(DnsResource* const copyAuthority)
  {
    if (copyAuthority == nullptr)
      return nullptr;

    return addAuthority(copyAuthority->getName(), copyAuthority->getDnsType(), copyAuthority->getDnsClass(),
                        copyAuthority->getTTL(), copyAuthority->getData().get());
  }

  bool DnsLayer::removeAuthority(const std::string& authorityNameToRemove, bool exactMatch)
  {
    DnsResource* authorityToRemove = getAuthority(authorityNameToRemove, exactMatch);
    if (authorityToRemove == nullptr)
    {
      PCPP_LOG_DEBUG("Authority not found");
      return false;
    }

    return removeAuthority(authorityToRemove);
  }

  bool DnsLayer::removeAuthority(DnsResource* authorityToRemove)
  {
    bool res = removeResource(authorityToRemove);
    if (res)
    {
      // decrease number of authority records
      getDnsHeader()->numberOfAuthority = htobe16(getAuthorityCount() - 1);
    }

    return res;
  }

  DnsResource* DnsLayer::addAdditionalRecord(const std::string& name, DnsType dnsType, DnsClass dnsClass,
                                             uint32_t ttl, IDnsResourceData* data)
  {
    DnsResource* res = addResource(DnsAdditionalType, name, dnsType, dnsClass, ttl, data);
    if (res != nullptr)
    {
      // increase number of authority records
      getDnsHeader()->numberOfAdditional = htobe16(getAdditionalRecordCount() + 1);
    }

    return res;
  }

  DnsResource* DnsLayer::addAdditionalRecord(const std::string& name, DnsType dnsType, uint16_t customData1,
                                             uint32_t customData2, IDnsResourceData* data)
  {
    DnsResource* res = addAdditionalRecord(name, dnsType, DNS_CLASS_ANY, customData2, data);
    if (res != nullptr)
    {
      res->setCustomDnsClass(customData1);
    }

    return res;
  }

  DnsResource* DnsLayer::addAdditionalRecord(DnsResource* const copyAdditionalRecord)
  {
    if (copyAdditionalRecord == nullptr)
      return nullptr;

    return addAdditionalRecord(copyAdditionalRecord->getName(), copyAdditionalRecord->getDnsType(),
                               copyAdditionalRecord->getCustomDnsClass(), copyAdditionalRecord->getTTL(),
                               copyAdditionalRecord->getData().get());
  }

  bool DnsLayer::removeAdditionalRecord(const std::string& additionalRecordNameToRemove, bool exactMatch)
  {
    DnsResource* additionalRecordToRemove = getAdditionalRecord(additionalRecordNameToRemove, exactMatch);
    if (additionalRecordToRemove == nullptr)
    {
      PCPP_LOG_DEBUG("Additional record not found");
      return false;
    }

    return removeAdditionalRecord(additionalRecordToRemove);
  }

  bool DnsLayer::removeAdditionalRecord(DnsResource* additionalRecordToRemove)
  {
    bool res = removeResource(additionalRecordToRemove);
    if (res)
    {
      // decrease number of additional records
      getDnsHeader()->numberOfAdditional = htobe16(getAdditionalRecordCount() - 1);
    }

    return res;
  }

  bool DnsLayer::removeResource(IDnsResource* resourceToRemove)
  {
    if (resourceToRemove == nullptr)
    {
      PCPP_LOG_DEBUG("resourceToRemove cannot be nullptr");
      return false;
    }

    // find the resource preceding resourceToRemove
    IDnsResource* prevResource = m_ResourceList;

    if (m_ResourceList != resourceToRemove)
    {
      while (prevResource != nullptr)
      {
        IDnsResource* temp = prevResource->getNextResource();
        if (temp == resourceToRemove)
          break;

        prevResource = temp;
      }
    }

    if (prevResource == nullptr)
    {
      PCPP_LOG_DEBUG("Resource not found");
      return false;
    }

    // shorten the layer and fix offset in layer for all next DNS resources in the packet
    if (!shortenLayer(resourceToRemove->m_OffsetInLayer, resourceToRemove->getSize(), resourceToRemove))
    {
      PCPP_LOG_ERROR("Couldn't shorten the DNS layer, resource cannot be removed");
      return false;
    }

    // remove resourceToRemove from the resources linked list
    if (m_ResourceList != resourceToRemove)
    {
      prevResource->setNextResource(resourceToRemove->getNextResource());
    }
    else
    {
      m_ResourceList = resourceToRemove->getNextResource();
    }

    // check whether resourceToRemove was the first of its type
    if (getFirstResource(resourceToRemove->getType()) == resourceToRemove)
    {
      IDnsResource* nextResource = resourceToRemove->getNextResource();
      if (nextResource != nullptr && nextResource->getType() == resourceToRemove->getType())
        setFirstResource(resourceToRemove->getType(), nextResource);
      else
        setFirstResource(resourceToRemove->getType(), nullptr);
    }

    // free resourceToRemove memory
    delete resourceToRemove;

    return true;
  }

  // ~~~~~~~~~~~~~~~
  // DnsOverTcpLayer
  // ~~~~~~~~~~~~~~~

  uint16_t DnsOverTcpLayer::getTcpMessageLength()
  {
    return be16toh(*(uint16_t*)m_Data);
  }

  void DnsOverTcpLayer::setTcpMessageLength(uint16_t value)
  {
    ((uint16_t*)m_Data)[0] = htobe16(value);
  }

  void DnsOverTcpLayer::computeCalculateFields()
  {
    setTcpMessageLength(m_DataLen - sizeof(uint16_t));
  }

}  // namespace pcpp

Coverage Report

Created: 2026-09-03 08:09