#ifndef PACKETPP_GRE_LAYER

#define PACKETPP_GRE_LAYER

#include "Layer.h"

/// @file

/**

 * \namespace pcpp

 * \brief The main namespace for the PcapPlusPlus lib

 */

namespace pcpp

{

  /**

   * @struct gre_basic_header

   * Represents GRE basic protocol header (common for GREv0 and GREv1)

   */

#pragma pack(push, 1)

  struct gre_basic_header

  {

#if (BYTE_ORDER == LITTLE_ENDIAN)

    /** Number of additional encapsulations which are permitted. 0 is the default value */

    uint8_t recursionControl:3,

    /** Strict source routing bit (GRE v0 only) */

        strictSourceRouteBit:1,

    /** Set if sequence number exists */

        sequenceNumBit:1,

    /** Set if key exists */

        keyBit:1,

    /** Set if routing exists (GRE v0 only) */

        routingBit:1,

    /** Set if checksum exists (GRE v0 only) */

        checksumBit:1;

#else

    /** Set if checksum exists (GRE v0 only) */

    uint8_t checksumBit:1,

    /** Set if routing exists (GRE v0 only) */

        routingBit:1,

    /** Set if key exists */

        keyBit:1,

    /** Set if sequence number exists */

        sequenceNumBit:1,

    /** Strict source routing bit (GRE v0 only) */

        strictSourceRouteBit:1,

    /** Number of additional encapsulations which are permitted. 0 is the default value */

        recursionControl:3;

#endif

#if (BYTE_ORDER == LITTLE_ENDIAN)

    /** GRE version - can be 0 or 1 */

    uint8_t version:3,

    /** Reserved */

        flags:4,

    /** Set if acknowledgment number is set (GRE v1 only) */

        ackSequenceNumBit:1;

#else

    /** Set if acknowledgment number is set (GRE v1 only) */

    uint8_t ackSequenceNumBit:1,

    /** Reserved */

        flags:4,

    /** GRE version - can be 0 or 1 */

        version:3;

#endif

    /** Protocol type of the next layer */

    uint16_t protocol;

  };

#pragma pack(pop)

  /**

   * @struct gre1_header

   * Represents GREv1 protocol header

   */

#pragma pack(push, 1)

  struct gre1_header : gre_basic_header

  {

    /** Size of the payload not including the GRE header */

    uint16_t payloadLength;

    /** Contains the Peer's Call ID for the session to which this packet belongs */

    uint16_t callID;

  };

#pragma pack(pop)

  /**

   * @struct ppp_pptp_header

   * Represents PPP layer that comes after GREv1 as part of PPTP protocol

   */

#pragma pack(push, 1)

  struct ppp_pptp_header

  {

    /** Broadcast address */

    uint8_t address;

    /** Control byte */

    uint8_t control;

    /** Protocol type of the next layer (see PPP_* macros at PPPoELayer.h) */

    uint16_t protocol;

  };

#pragma pack(pop)

  /**

   * @class GreLayer

   * Abstract base class for GRE layers (GREv0Layer and GREv1Layer). Cannot be instantiated and contains common logic for derived classes

   */

  class GreLayer : public Layer

  {

  public:

    virtual ~GreLayer() {}

    /**

     * A static method that determines the GRE version of GRE layer raw data by looking at the gre_basic_header#version

     * field

     * @param[in] greData GRE layer raw data

     * @param[in] greDataLen Size of raw data

     * @return ::GREv0 or ::GREv1 values if raw data is GREv0 or GREv1 (accordingly) or ::UnknownProtocol otherwise

     */

    static ProtocolType getGREVersion(uint8_t* greData, size_t greDataLen);

    /**

     * Get sequence number value if field exists in layer

     * @param[out] seqNumber The returned sequence number value if exists in layer. Else remain unchanged

     * @return True if sequence number field exists in layer. In this case seqNumber will be filled with the value.

     * Or false if sequence number field doesn't exist in layer

     */

    bool getSequenceNumber(uint32_t& seqNumber) const;

    /**

     * Set sequence number value. If field already exists (gre_basic_header#sequenceNumBit is set) then only the new

     * value is set. If field doesn't exist it will be added to the layer, gre_basic_header#sequenceNumBit will be set

     * and the new value will be set

     * @param[in] seqNumber The sequence number value to set

     * @return True if managed to set the value successfully, or false otherwise (if couldn't extend the layer)

     */

    bool setSequenceNumber(uint32_t seqNumber);

    /**

     * Unset sequence number and remove it from the layer

     * @return True if managed to unset successfully or false (and error log) if sequence number wasn't set in the first

     * place or if didn't manage to remove it from the layer

     */

    bool unsetSequenceNumber();

    // implement abstract methods

    /**

     * Currently identifies the following next layers:

     *   IPv4Layer, IPv6Layer, VlanLayer, MplsLayer, PPP_PPTPLayer, EthLayer, EthDot3Layer

     * Otherwise sets PayloadLayer

     */

    void parseNextLayer();

    /**

     * @return Size of GRE header (may change if optional fields are added or removed)

     */

    size_t getHeaderLen() const;

    OsiModelLayer getOsiModelLayer() const { return OsiModelNetworkLayer; }

  protected:

    GreLayer(uint8_t* data, size_t dataLen, Layer* prevLayer, Packet* packet) : Layer(data, dataLen, prevLayer, packet) { }

    GreLayer() {}

    enum GreField

    {

      GreChecksumOrRouting = 0,

      GreKey = 1,

      GreSeq = 2,

      GreAck = 3

    };

    uint8_t* getFieldValue(GreField field, bool returnOffsetEvenIfFieldMissing) const;

    void computeCalculateFieldsInner();

  };

  /**

   * @class GREv0Layer

   * Represents a GRE version 0 protocol. Limitation: currently this layer doesn't support GRE routing information parsing

   * and editing. So if a GREv0 packet includes routing information it won't be parse correctly. I didn't add it because

   * of lack of time, but if you need it please tell me and I'll add it

   */

  class GREv0Layer : public GreLayer

  {

  public:

     /** A constructor that creates the layer from an existing packet raw data

     * @param[in] data A pointer to the raw data

     * @param[in] dataLen Size of the data in bytes

     * @param[in] prevLayer A pointer to the previous layer

     * @param[in] packet A pointer to the Packet instance where layer will be stored in

     */

    GREv0Layer(uint8_t* data, size_t dataLen, Layer* prevLayer, Packet* packet) : GreLayer(data, dataLen, prevLayer, packet) { m_Protocol = GREv0; }

    /**

     * A constructor that creates a new GREv0 header and allocates the data

     */

    GREv0Layer();

    virtual ~GREv0Layer() {}

    /**

     * Get a pointer to the basic GRE header containing only non-optional fields. Notice this points directly to the data,

     * so every change will change the actual packet data. Also please notice that changing the set bits

     * (gre_basic_header#strictSourceRouteBit, gre_basic_header#sequenceNumBit, gre_basic_header#keyBit, gre_basic_header#routingBit,

     * gre_basic_header#checksumBit, gre_basic_header#ackSequenceNumBit) without using the proper set or unset methods (such

     * as setChecksum(), unsetChecksum(), etc.) may result to wrong calculation of header length and really weird bugs.

     * Please avoid doing so

     * @return A pointer to the gre_basic_header

     */

    gre_basic_header* getGreHeader() const { return (gre_basic_header*)m_Data; }

    /**

     * Get checksum value if field exists in layer

     * @param[out] checksum The returned checksum value if exists in layer. Else remain unchanged

     * @return True if checksum field exists in layer. In this case checksum parameter will be filled with the value.

     * Or false if checksum field doesn't exist in layer

     */

    bool getChecksum(uint16_t& checksum);

    /**

     * Set checksum value. If checksum or offset fields already exist (gre_basic_header#checksumBit or gre_basic_header#routingBit are set)

     * then only the new value is set. If both fields don't exist a new 4-byte value will be added to the layer,

     * gre_basic_header#checksumBit will be set (gre_basic_header#routingBit will remain unset), the new checksum value

     * will be set and offset value will be set to 0. The reason both fields are added is that GREv0 protocol states

     * both of them or none of them should exist on packet (even if only one of the bits are set)

     * @param[in] checksum The checksum value to set

     * @return True if managed to set the value/s successfully, or false otherwise (if couldn't extend the layer)

     */

    bool setChecksum(uint16_t checksum);

    /**

     * Unset checksum and possibly remove it from the layer. It will be removed from the layer only if gre_basic_header#routingBit

     * is not set as well. Otherwise checksum field will remain on packet with value of 0

     * @return True if managed to unset successfully or false (and error log) if checksum wasn't set in the first

     * place or if didn't manage to remove it from the layer

     */

    bool unsetChecksum();

    /**

     * Get offset value if field exists in layer. Notice there is no setOffset() method as GRE routing information isn't

     * supported yet (see comment on class description)

     * @param[out] offset The returned offset value if exists in layer. Else remain unchanged

     * @return True if offset field exists in layer. In this case offset parameter will be filled with the value.

     * Or false if offset field doesn't exist in layer

     */

    bool getOffset(uint16_t& offset) const;

    /**

     * Get key value if field exists in layer

     * @param[out] key The returned key value if exists in layer. Else remain unchanged

     * @return True if key field exists in layer. In this case key parameter will be filled with the value.

     * Or false if key field doesn't exist in layer

     */

    bool getKey(uint32_t& key) const;

    /**

     * Set key value. If field already exists (gre_basic_header#keyBit is set) then only the new value is set.

     * If field doesn't exist it will be added to the layer, gre_basic_header#keyBit will be set

     * and the new value will be set

     * @param[in] key The key value to set

     * @return True if managed to set the value successfully, or false otherwise (if couldn't extend the layer)

     */

    bool setKey(uint32_t key);

    /**

     * Unset key and remove it from the layer

     * @return True if managed to unset successfully or false (and error log) if key wasn't set in the first

     * place or if didn't manage to remove it from the layer

     */

    bool unsetKey();

    // implement abstract methods

    /**

     * Calculate the following fields:

     * - gre_basic_header#protocol

     * - GRE checksum field (if exists in packet)

     */

    void computeCalculateFields();

    std::string toString() const;

  };

  /**

   * @class GREv1Layer

   * Represents a GRE version 1 protocol

   */

  class GREv1Layer : public GreLayer

  {

  public:

     /** A constructor that creates the layer from an existing packet raw data

     * @param[in] data A pointer to the raw data

     * @param[in] dataLen Size of the data in bytes

     * @param[in] prevLayer A pointer to the previous layer

     * @param[in] packet A pointer to the Packet instance where layer will be stored in

     */

    GREv1Layer(uint8_t* data, size_t dataLen, Layer* prevLayer, Packet* packet) : GreLayer(data, dataLen, prevLayer, packet) { m_Protocol = GREv1; }

    /**

     * A constructor that creates a new GREv1 header and allocates the data

     * @param[in] callID The call ID to set

     */

    explicit GREv1Layer(uint16_t callID);

    virtual ~GREv1Layer() {}

    /**

     * Get a pointer to the basic GREv1 header containing all non-optional fields. Notice this points directly to the data, so every change will change the actual

     * packet data. Also please notice that changing the set bits (gre_basic_header#strictSourceRouteBit, gre_basic_header#sequenceNumBit, gre_basic_header#keyBit,

     * gre_basic_header#routingBit, gre_basic_header#checksumBit, gre_basic_header#ackSequenceNumBit) without using the proper set or unset methods

     * (such as setAcknowledgmentNum(), unsetSequenceNumber(), etc.) may result to wrong calculation of header length or illegal GREv1 packet and

     * to some really weird bugs. Please avoid doing so

     * @return A pointer to the gre1_header

     */

    gre1_header* getGreHeader() const { return (gre1_header*)m_Data; }

    /**

     * Get acknowledgment (ack) number value if field exists in layer

     * @param[out] ackNum The returned ack number value if exists in layer. Else remain unchanged

     * @return True if ack number field exists in layer. In this case ackNum will be filled with the value.

     * Or false if ack number field doesn't exist in layer

     */

    bool getAcknowledgmentNum(uint32_t& ackNum) const;

    /**

     * Set acknowledgment (ack) number value. If field already exists (gre_basic_header#ackSequenceNumBit is set)

     * then only the new value is set. If field doesn't exist it will be added to the layer,

     * gre_basic_header#ackSequenceNumBit will be set and the new value will be set

     * @param[in] ackNum The ack number value to set

     * @return True if managed to set the value successfully, or false otherwise (if couldn't extend the layer)

     */

    bool setAcknowledgmentNum(uint32_t ackNum);

    /**

     * Unset acknowledgment (ack) number and remove it from the layer

     * @return True if managed to unset successfully or false (and error log) if ack number wasn't set in the first

     * place or if didn't manage to remove it from the layer

     */

    bool unsetAcknowledgmentNum();

    // implement abstract methods

    /**

     * Calculate the following fields:

     * - gre1_header#payloadLength

     * - gre_basic_header#protocol

     */

    void computeCalculateFields();

    std::string toString() const;

  };

  /**

   * @class PPP_PPTPLayer

   * Represent a PPP (point-to-point) protocol header that comes after GREv1 header, as part of PPTP - Point-to-Point Tunneling Protocol

   */

  class PPP_PPTPLayer : public Layer

  {

  public:

    /**

     * A constructor that creates the layer from an existing packet raw data

     * @param[in] data A pointer to the raw data (will be casted to @ref ppp_pptp_header)

     * @param[in] dataLen Size of the data in bytes

     * @param[in] prevLayer A pointer to the previous layer

     * @param[in] packet A pointer to the Packet instance where layer will be stored in

     */

    PPP_PPTPLayer(uint8_t* data, size_t dataLen, Layer* prevLayer, Packet* packet) : Layer(data, dataLen, prevLayer, packet) { m_Protocol = PPP_PPTP; }

    /**

     * A constructor that allocates a new PPP-PPTP header

     * @param[in] address Address field

     * @param[in] control Control field

     */

    PPP_PPTPLayer(uint8_t address, uint8_t control);

    ~PPP_PPTPLayer() {}

    /**

     * Get a pointer to the PPP-PPTP header. Notice this points directly to the data, so every change will change the actual packet data

     * @return A pointer to the @ref ppp_pptp_header

     */

    ppp_pptp_header* getPPP_PPTPHeader() const { return (ppp_pptp_header*)m_Data; }

    // implement abstract methods

    /**

     * Currently identifies the following next layers: IPv4Layer, IPv6Layer. Otherwise sets PayloadLayer

     */

    void parseNextLayer();

    /**

     * @return The size of @ref ppp_pptp_header

     */

    size_t getHeaderLen() const { return sizeof(ppp_pptp_header); }

    /**

     * Calculate the following fields:

     * - ppp_pptp_header#protocol

     */

    void computeCalculateFields();

    std::string toString() const { return "PPP for PPTP Layer"; }

    OsiModelLayer getOsiModelLayer() const { return OsiModelSesionLayer; }

  };

} // namespace pcpp

#endif /* PACKETPP_GRE_LAYER */