/src/PcapPlusPlus/Packet++/header/DnsResourceData.h

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#pragma once

#include "DnsResource.h"
#include "IpAddress.h"
#include <memory>
#include <string>
#include <stdint.h>

/// @file

/// @namespace pcpp
/// @brief The main namespace for the PcapPlusPlus lib
namespace pcpp
{
  // forward declarations
  class IDnsResource;

  /// @class IDnsResourceData
  /// A wrapper class for storing DNS RR (resource record) data. This is the base class which introduces several
  /// abstract methods for derived classes to implement for setting and retrieving the stored data. Each derived class
  /// will store different type of DNS RR data and implement these methods accordingly (for example: IPv4/IPv6
  /// addresses, MX data, hostnames, raw byte data etc.)
  class IDnsResourceData
  {
  protected:
    // unimplemented private copy c'tor
    IDnsResourceData(const IDnsResourceData& other);
    IDnsResourceData()
    {}

    size_t decodeName(const char* encodedName, char* result, IDnsResource* dnsResource) const;
    void encodeName(const std::string& decodedName, char* result, size_t& resultLen,
                    IDnsResource* dnsResource) const;

  public:
    /// A virtual d'tor, does nothing
    virtual ~IDnsResourceData() = default;

    /// A templated method which takes a class that derives from IDnsResourceData as the template argument and
    /// checks whether this instance is of this type
    /// @return True if this instance is of the requested type, false otherwise
    template <class IDnsResourceDataType> bool isTypeOf() const
    {
      return dynamic_cast<const IDnsResourceDataType*>(this) != nullptr;
    }

    /// A templated method which take a class that derives from IDnsResourceData as the template argument and tries
    /// to cast the current instance as that type
    /// @return A pointer to the current instance casted as the requested type or nullptr if this instance isn't of
    /// this type
    template <class IDnsResourceDataType> IDnsResourceDataType* castAs()
    {
      return dynamic_cast<IDnsResourceDataType*>(this);
    }

    /// @return A string that represents the current DNS RR data
    virtual std::string toString() const = 0;

    /// Convert the DNS RR data into a byte array
    /// @param[out] arr A pointer to a pre-allocated byte array where the result will be written to
    /// @param[out] arrLength A reference to a 2-byte number where the result array length will be written to
    /// @param[in] dnsResource A pointer to a DNS resource object where this DNS RR data will be stored
    /// @return True if the DNS RR data was successfully converted into a byte array and written to the given array
    /// or false if stored DNS RR data is invalid or if it could not be written to the given array
    virtual bool toByteArr(uint8_t* arr, size_t& arrLength, IDnsResource* dnsResource) const = 0;
  };

  /// @class DnsResourceDataPtr
  /// A smart pointer class that holds pointers of type IDnsResourceData. This object is used in DnsResource#getData()
  class DnsResourceDataPtr : public std::unique_ptr<IDnsResourceData>
  {
  public:
    /// A c'tor to this class
    /// @param[in] ptr A pointer to IDnsResourceData
    explicit DnsResourceDataPtr(IDnsResourceData* ptr) : std::unique_ptr<IDnsResourceData>(ptr)
    {}

    /// A templated method which takes a class that derives from IDnsResourceData as the template argument and
    /// checks whether the pointer stored in this object is of this type
    /// @return True if the stored pointer is of the requested type, false otherwise
    template <class IDnsResourceDataType> bool isTypeOf() const
    {
      return get()->isTypeOf<IDnsResourceDataType>();
    }

    /// A templated method which take a class that derives from IDnsResourceData as the template argument and tries
    /// to cast the pointer stored in this object as that type
    /// @return A pointer to the stored pointer casted as the requested type or nullptr if it isn't of this type
    template <class IDnsResourceDataType> IDnsResourceDataType* castAs()
    {
      return get()->castAs<IDnsResourceDataType>();
    }
  };

  /// @class StringDnsResourceData
  /// A class that represents DNS RR string data, mainly used in DNS RRs that store hostnames (like CNAME, DNAME, NS,
  /// etc.)
  class StringDnsResourceData : public IDnsResourceData
  {
  private:
    std::string m_Data;

  public:
    /// A c'tor for this class
    /// @param[in] data The string data to store in this object. If this string represents a hostname it's possible
    /// to include a pointer to another string in the DNS layer (as explained here:
    /// http://www.zytrax.com/books/dns/ch15/#name). These pointers are often used to reduce the DNS packet size and
    /// avoid unnecessary duplications. The way to include pointers in a hostname string is to use the following
    /// format: 'some.domain.#{offset}' where '#{offset}' is the offset from the start of the DNS layer. For
    /// example: if the string 'yahoo.com' already appears in offset 12 in the packet and you want to set the DNS RR
    /// data as 'my.subdomain.yahoo.com' you may use the following string: 'my.subdomain.#12'. This will result in
    /// writing 'my.subdomain' and a pointer to offset 12
    explicit StringDnsResourceData(const std::string& data) : m_Data(data)
    {}

    StringDnsResourceData(const uint8_t* dataPtr, size_t dataLen, IDnsResource* dnsResource);

    ~StringDnsResourceData() override = default;

    /// Equality operator overload for this class that compares the strings stored in each object
    /// @param[in] other The object to compare with
    /// @return True if the string data is the same in both objects, false otherwise
    bool operator==(const StringDnsResourceData& other) const
    {
      return m_Data == other.m_Data;
    }

    // implement abstract methods

    std::string toString() const override
    {
      return m_Data;
    }
    bool toByteArr(uint8_t* arr, size_t& arrLength, IDnsResource* dnsResource) const override;
  };

  /// @class IPv4DnsResourceData
  /// A class that represents DNS RR IPv4 data, mainly used in DNS RRs of type ::DNS_TYPE_A
  class IPv4DnsResourceData : public IDnsResourceData
  {
  private:
    IPv4Address m_Data;

  public:
    /// A c'tor for this class
    /// @param[in] dataPtr A byte array of size 4 that contains an IPv4 address (each byte represents 1 octet)
    /// @param[in] dataLen The byte array size, expected to be 4
    IPv4DnsResourceData(const uint8_t* dataPtr, size_t dataLen);

    /// A c'tor for this class
    /// @param[in] addr The IPv4 address to store in this object
    explicit IPv4DnsResourceData(const IPv4Address& addr) : m_Data(addr)
    {}

    /// A c'tor for this class
    /// @param[in] addrAsString A string representation of an IPv4 address to store in this object
    explicit IPv4DnsResourceData(const std::string& addrAsString) : m_Data(addrAsString)
    {}

    /// Equality operator overload for this class that compares the IPv4 addresses stored in each object
    /// @param[in] other The object to compare with
    /// @return True if IPv4 addresses are the same in both objects, false otherwise
    bool operator==(const IPv4DnsResourceData& other) const
    {
      return m_Data == other.m_Data;
    }

    /// @return The IPv4 address stored in this object
    IPv4Address getIpAddress() const
    {
      return m_Data;
    }

    // implement abstract methods

    std::string toString() const override
    {
      return m_Data.toString();
    }
    bool toByteArr(uint8_t* arr, size_t& arrLength, IDnsResource* dnsResource) const override;
  };

  /// @class IPv6DnsResourceData
  /// A class that represents DNS RR IPv6 data, mainly used in DNS RRs of type ::DNS_TYPE_AAAA
  class IPv6DnsResourceData : public IDnsResourceData
  {
  private:
    IPv6Address m_Data;

  public:
    /// A c'tor for this class
    /// @param[in] dataPtr A byte array of size 16 that contains an IPv6 address (each byte represents 1 octet)
    /// @param[in] dataLen The byte array size, expected to be 16
    IPv6DnsResourceData(const uint8_t* dataPtr, size_t dataLen);

    /// A c'tor for this class
    /// @param[in] addr The IPv6 address to store in this object
    explicit IPv6DnsResourceData(const IPv6Address& addr) : m_Data(addr)
    {}

    /// A c'tor for this class
    /// @param[in] addrAsString A string representation of an IPv6 address to store in this object
    explicit IPv6DnsResourceData(const std::string& addrAsString) : m_Data(addrAsString)
    {}

    /// Equality operator overload for this class that compares the IPv6 addresses stored in each object
    /// @param[in] other The object to compare with
    /// @return True if IPv6 addresses are the same in both objects, false otherwise
    bool operator==(const IPv6DnsResourceData& other) const
    {
      return m_Data == other.m_Data;
    }

    /// @return The IPv6 address stored in this object
    IPv6Address getIpAddress() const
    {
      return m_Data;
    }

    // implement abstract methods

    std::string toString() const override
    {
      return m_Data.toString();
    }
    bool toByteArr(uint8_t* arr, size_t& arrLength, IDnsResource* dnsResource) const override;
  };

  /// @class MxDnsResourceData
  /// A class that represents DNS RR mail exchange (MX) data, used in DNS RRs of type ::DNS_TYPE_MX
  class MxDnsResourceData : public IDnsResourceData
  {
  public:
    /// A struct that represents mail exchange (MX) data
    struct MxData
    {
      /// Preference value
      uint16_t preference;
      /// Mail exchange hostname
      std::string mailExchange;
    };

    /// A c'tor for this class
    /// @param[in] dataPtr A byte array that contains the raw MX data (as written in the DNS packet)
    /// @param[in] dataLen The byte array size
    /// @param[in] dnsResource A pointer to a DNS resource object where this DNS RR data will be stored
    MxDnsResourceData(uint8_t* dataPtr, size_t dataLen, IDnsResource* dnsResource);

    /// A c'tor for this class
    /// @param[in] preference The MX preference value to store in this object
    /// @param[in] mailExchange The MX hostname value to store in this object. It's possible to include a pointer to
    /// another string in the DNS layer (as explained here: http://www.zytrax.com/books/dns/ch15/#name). These
    /// pointers are often used to reduce the DNS packet size and avoid unnecessary duplications. The way to include
    /// pointers in the hostname string is to use the following format: 'some.domain.#{offset}' where '#{offset}' is
    /// the offset from the start of the DNS layer. For example: if the string 'yahoo.com' already appears in offset
    /// 12 in the packet and you want to set the DNS RR data as 'my.subdomain.yahoo.com' you may use the following
    /// string: 'my.subdomain.#12'. This will result in writing 'my.subdomain' and a pointer to offset 12
    MxDnsResourceData(const uint16_t& preference, const std::string& mailExchange);

    ~MxDnsResourceData() override = default;

    /// Equality operator overload for this class that compares the MX data stored in each object
    /// @param[in] other The object to compare with
    /// @return True if MX data is the same in both objects, meaning both preference and MX hostname are the same,
    /// false otherwise
    bool operator==(const MxDnsResourceData& other) const;

    /// @return The MX data stored in this object
    MxData getMxData() const
    {
      return m_Data;
    }

    /// Set the MX data stored in this object
    /// @param[in] preference The MX preference value to store in this object
    /// @param[in] mailExchange The MX hostname value to store in this object
    void setMxData(uint16_t preference, std::string mailExchange);

    // implement abstract methods

    /// A string representation of the MX data stored in this object. The string format is as follows:
    /// 'pref: {preference_value}; mx: {mail_exchange_hostname_value}'
    std::string toString() const override;

    bool toByteArr(uint8_t* arr, size_t& arrLength, IDnsResource* dnsResource) const override;

  private:
    MxData m_Data;
  };

  /// @class GenericDnsResourceData
  /// A class that represents generic DNS RR data which cannot be represented in any of the other classes. It stores
  /// the DNS RR data as byte array
  class GenericDnsResourceData : public IDnsResourceData
  {
  private:
    uint8_t* m_Data;
    size_t m_DataLen;

  public:
    /// A c'tor for this class
    /// @param[in] dataPtr A byte array that contains the raw data (as it written in the DNS packet). The data will
    /// be copied from this byte array to the object
    /// @param[in] dataLen The byte array size
    GenericDnsResourceData(const uint8_t* dataPtr, size_t dataLen);

    /// A c'tor for this class
    /// @param[in] dataAsHexString A hex string that represents the DNS RR data
    explicit GenericDnsResourceData(const std::string& dataAsHexString);

    /// A copy c'tor for this class
    /// @param[in] other The instance to copy from
    GenericDnsResourceData(const GenericDnsResourceData& other);

    ~GenericDnsResourceData() override
    {
      if (m_Data != nullptr)
        delete[] m_Data;
    }

    GenericDnsResourceData& operator=(const GenericDnsResourceData& other);

    /// Equality operator overload for this class that compares the raw data stored in each object
    /// @param[in] other The object to compare with
    /// @return True if data is the same in both objects, meaning byte streams are equal, false otherwise
    bool operator==(const GenericDnsResourceData& other) const;

    // implement abstract methods

    std::string toString() const override;
    bool toByteArr(uint8_t* arr, size_t& arrLength, IDnsResource* dnsResource) const override;
  };

}  // namespace pcpp

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Created: 2025-07-11 07:47