85 lines
3.0 KiB
C++
85 lines
3.0 KiB
C++
#ifndef PACKETPP_PACKET_TRAILER_LAYER
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#define PACKETPP_PACKET_TRAILER_LAYER
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/// @file
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#include "Layer.h"
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namespace pcpp
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{
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/**
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* @class PacketTrailerLayer
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* A class for representing packet tailer (a.k.a footer or padding) which refers to supplemental data placed at the end of a block of data
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* being stored or transmitted, which may contain information for the handling of the data block, or just mark its end
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* (taken from Wikipedia: https://en.wikipedia.org/wiki/Trailer_(computing) )
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*
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* There are various reasons for adding a packet trailer, one of the most famous is FCS (Frame check sequence) which refers to the extra
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* error-detecting code added to a frame. Another usage is padding which means adding data to reach a minimum required packet length.
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*
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* Although this layer inherits from the Layer class, it is not a standard layer in the sense that it can't be constructed by the user.
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* This layer may be only be constructed in the Packet class, in the process of parsing the packet and creating the layers; if at the end
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* of the parsing process there is data left that is not allocated to any layer, it's assumed to be the packet trailer and an instance of
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* this class is created. This means this layer can only exist as the last layer in a packet, if a packet trailer indeed exists.
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*
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* No layer can be added by the user after this layer (trying to do that will result with an error).
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*
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* This layer can be removed by the user or extended/shortened, as any layer.
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*
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* It also contains method to extract the trailer data
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*/
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class PacketTrailerLayer : public Layer
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{
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public:
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/** A constructor that creates the layer from an existing packet raw data
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* @param[in] data A pointer to the raw data
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* @param[in] dataLen Size of the data in bytes
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* @param[in] prevLayer A pointer to the previous layer
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* @param[in] packet A pointer to the Packet instance where layer will be stored in
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*/
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PacketTrailerLayer(uint8_t* data, size_t dataLen, Layer* prevLayer, Packet* packet) : Layer(data, dataLen, prevLayer, packet) { m_Protocol = PacketTrailer; }
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~PacketTrailerLayer() {}
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/**
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* Get a pointer to the trailer data
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* @return A pointer to the trailer data
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*/
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uint8_t* getTrailerData() const { return m_Data; }
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/**
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* @return Trailer data as hex string
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*/
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std::string getTrailerDataAsHexString() const;
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/**
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* Get the trailer data length
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* @return The trailer data length in bytes
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*/
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size_t getTrailerLen() const { return m_DataLen; }
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// implement abstract methods
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/**
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* Does nothing for this layer (PacketTrailerLayer is always last)
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*/
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void parseNextLayer() {}
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/**
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* @return trailer data length in bytes
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*/
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size_t getHeaderLen() const { return m_DataLen; }
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/**
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* Does nothing for this layer
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*/
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void computeCalculateFields() {}
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std::string toString() const;
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OsiModelLayer getOsiModelLayer() const { return OsiModelDataLinkLayer; }
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};
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}
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#endif // PACKETPP_PACKET_TRAILER_LAYER
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