Ethernet frame (layer 2, IEEE 802.3): C++11/STL parsing library

Ethernet frame is a OSI data link layer (layer 2) protocol data unit for Ethernet networks. In practice, many other networks and/or in-file dumps adopted the same format for encapsulation purposes.

KS implementation details

License: CC0-1.0
Minimal Kaitai Struct required: 0.8

References

This page hosts a formal specification of Ethernet frame (layer 2, IEEE 802.3) using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.

Usage

Runtime library

All parsing code for C++11/STL generated by Kaitai Struct depends on the C++/STL runtime library. You have to install it before you can parse data.

For C++, the easiest way is to clone the runtime library sources and build them along with your project.

Code

Using Kaitai Struct in C++/STL usually consists of 3 steps.

  1. We need to create an STL input stream (std::istream). One can open local file for that, or use existing std::string or char* buffer.
    #include <fstream>
    
    std::ifstream is("path/to/local/file.ethernet_frame", std::ifstream::binary);
    
    #include <sstream>
    
    std::istringstream is(str);
    
    #include <sstream>
    
    const char buf[] = { ... };
    std::string str(buf, sizeof buf);
    std::istringstream is(str);
    
  2. We need to wrap our input stream into Kaitai stream:
    #include "kaitai/kaitaistream.h"
    
    kaitai::kstream ks(&is);
    
  3. And finally, we can invoke the parsing:
    ethernet_frame_t data(&ks);
    

After that, one can get various attributes from the structure by invoking getter methods like:

data.dst_mac() // => Destination MAC address
data.ether_type() // => Ether type can be specied in several places in the frame. If
first location bears special marker (0x8100), then it is not the
real ether frame yet, an additional payload (`tci`) is expected
and real ether type is upcoming next.

C++11/STL source code to parse Ethernet frame (layer 2, IEEE 802.3)

ethernet_frame.h

#pragma once

// This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild

#include "kaitai/kaitaistruct.h"
#include <stdint.h>
#include <memory>
#include "ipv4_packet.h"
#include "ipv6_packet.h"

#if KAITAI_STRUCT_VERSION < 9000L
#error "Incompatible Kaitai Struct C++/STL API: version 0.9 or later is required"
#endif
class ipv4_packet_t;
class ipv6_packet_t;

/**
 * Ethernet frame is a OSI data link layer (layer 2) protocol data unit
 * for Ethernet networks. In practice, many other networks and/or
 * in-file dumps adopted the same format for encapsulation purposes.
 * \sa https://ieeexplore.ieee.org/document/7428776 Source
 */

class ethernet_frame_t : public kaitai::kstruct {

public:
    class tag_control_info_t;

    enum ether_type_enum_t {
        ETHER_TYPE_ENUM_IPV4 = 2048,
        ETHER_TYPE_ENUM_X_75_INTERNET = 2049,
        ETHER_TYPE_ENUM_NBS_INTERNET = 2050,
        ETHER_TYPE_ENUM_ECMA_INTERNET = 2051,
        ETHER_TYPE_ENUM_CHAOSNET = 2052,
        ETHER_TYPE_ENUM_X_25_LEVEL_3 = 2053,
        ETHER_TYPE_ENUM_ARP = 2054,
        ETHER_TYPE_ENUM_IEEE_802_1Q_TPID = 33024,
        ETHER_TYPE_ENUM_IPV6 = 34525
    };

    ethernet_frame_t(kaitai::kstream* p__io, kaitai::kstruct* p__parent = nullptr, ethernet_frame_t* p__root = nullptr);

private:
    void _read();
    void _clean_up();

public:
    ~ethernet_frame_t();

    /**
     * Tag Control Information (TCI) is an extension of IEEE 802.1Q to
     * support VLANs on normal IEEE 802.3 Ethernet network.
     */

    class tag_control_info_t : public kaitai::kstruct {

    public:

        tag_control_info_t(kaitai::kstream* p__io, ethernet_frame_t* p__parent = nullptr, ethernet_frame_t* p__root = nullptr);

    private:
        void _read();
        void _clean_up();

    public:
        ~tag_control_info_t();

    private:
        uint64_t m_priority;
        bool m_drop_eligible;
        uint64_t m_vlan_id;
        ethernet_frame_t* m__root;
        ethernet_frame_t* m__parent;

    public:

        /**
         * Priority Code Point (PCP) is used to specify priority for
         * different kinds of traffic.
         */
        uint64_t priority() const { return m_priority; }

        /**
         * Drop Eligible Indicator (DEI) specifies if frame is eligible
         * to dropping while congestion is detected for certain classes
         * of traffic.
         */
        bool drop_eligible() const { return m_drop_eligible; }

        /**
         * VLAN Identifier (VID) specifies which VLAN this frame
         * belongs to.
         */
        uint64_t vlan_id() const { return m_vlan_id; }
        ethernet_frame_t* _root() const { return m__root; }
        ethernet_frame_t* _parent() const { return m__parent; }
    };

private:
    bool f_ether_type;
    ether_type_enum_t m_ether_type;

public:

    /**
     * Ether type can be specied in several places in the frame. If
     * first location bears special marker (0x8100), then it is not the
     * real ether frame yet, an additional payload (`tci`) is expected
     * and real ether type is upcoming next.
     */
    ether_type_enum_t ether_type();

private:
    std::string m_dst_mac;
    std::string m_src_mac;
    ether_type_enum_t m_ether_type_1;
    std::unique_ptr<tag_control_info_t> m_tci;
    bool n_tci;

public:
    bool _is_null_tci() { tci(); return n_tci; };

private:
    ether_type_enum_t m_ether_type_2;
    bool n_ether_type_2;

public:
    bool _is_null_ether_type_2() { ether_type_2(); return n_ether_type_2; };

private:
    std::unique_ptr<kaitai::kstruct> m_body;
    bool n_body;

public:
    bool _is_null_body() { body(); return n_body; };

private:
    ethernet_frame_t* m__root;
    kaitai::kstruct* m__parent;
    std::string m__raw_body;
    std::unique_ptr<kaitai::kstream> m__io__raw_body;

public:

    /**
     * Destination MAC address
     */
    std::string dst_mac() const { return m_dst_mac; }

    /**
     * Source MAC address
     */
    std::string src_mac() const { return m_src_mac; }

    /**
     * Either ether type or TPID if it is a IEEE 802.1Q frame
     */
    ether_type_enum_t ether_type_1() const { return m_ether_type_1; }
    tag_control_info_t* tci() const { return m_tci.get(); }
    ether_type_enum_t ether_type_2() const { return m_ether_type_2; }
    kaitai::kstruct* body() const { return m_body.get(); }
    ethernet_frame_t* _root() const { return m__root; }
    kaitai::kstruct* _parent() const { return m__parent; }
    std::string _raw_body() const { return m__raw_body; }
    kaitai::kstream* _io__raw_body() const { return m__io__raw_body.get(); }
};

ethernet_frame.cpp

// This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild

#include "ethernet_frame.h"

ethernet_frame_t::ethernet_frame_t(kaitai::kstream* p__io, kaitai::kstruct* p__parent, ethernet_frame_t* p__root) : kaitai::kstruct(p__io) {
    m__parent = p__parent;
    m__root = this;
    m_tci = nullptr;
    m__io__raw_body = nullptr;
    f_ether_type = false;
    _read();
}

void ethernet_frame_t::_read() {
    m_dst_mac = m__io->read_bytes(6);
    m_src_mac = m__io->read_bytes(6);
    m_ether_type_1 = static_cast<ethernet_frame_t::ether_type_enum_t>(m__io->read_u2be());
    n_tci = true;
    if (ether_type_1() == ethernet_frame_t::ETHER_TYPE_ENUM_IEEE_802_1Q_TPID) {
        n_tci = false;
        m_tci = std::unique_ptr<tag_control_info_t>(new tag_control_info_t(m__io, this, m__root));
    }
    n_ether_type_2 = true;
    if (ether_type_1() == ethernet_frame_t::ETHER_TYPE_ENUM_IEEE_802_1Q_TPID) {
        n_ether_type_2 = false;
        m_ether_type_2 = static_cast<ethernet_frame_t::ether_type_enum_t>(m__io->read_u2be());
    }
    n_body = true;
    switch (ether_type()) {
    case ethernet_frame_t::ETHER_TYPE_ENUM_IPV4: {
        n_body = false;
        m__raw_body = m__io->read_bytes_full();
        m__io__raw_body = std::unique_ptr<kaitai::kstream>(new kaitai::kstream(m__raw_body));
        m_body = std::unique_ptr<ipv4_packet_t>(new ipv4_packet_t(m__io__raw_body.get()));
        break;
    }
    case ethernet_frame_t::ETHER_TYPE_ENUM_IPV6: {
        n_body = false;
        m__raw_body = m__io->read_bytes_full();
        m__io__raw_body = std::unique_ptr<kaitai::kstream>(new kaitai::kstream(m__raw_body));
        m_body = std::unique_ptr<ipv6_packet_t>(new ipv6_packet_t(m__io__raw_body.get()));
        break;
    }
    default: {
        m__raw_body = m__io->read_bytes_full();
        break;
    }
    }
}

ethernet_frame_t::~ethernet_frame_t() {
    _clean_up();
}

void ethernet_frame_t::_clean_up() {
    if (!n_tci) {
    }
    if (!n_ether_type_2) {
    }
    if (!n_body) {
    }
}

ethernet_frame_t::tag_control_info_t::tag_control_info_t(kaitai::kstream* p__io, ethernet_frame_t* p__parent, ethernet_frame_t* p__root) : kaitai::kstruct(p__io) {
    m__parent = p__parent;
    m__root = p__root;
    _read();
}

void ethernet_frame_t::tag_control_info_t::_read() {
    m_priority = m__io->read_bits_int_be(3);
    m_drop_eligible = m__io->read_bits_int_be(1);
    m_vlan_id = m__io->read_bits_int_be(12);
}

ethernet_frame_t::tag_control_info_t::~tag_control_info_t() {
    _clean_up();
}

void ethernet_frame_t::tag_control_info_t::_clean_up() {
}

ethernet_frame_t::ether_type_enum_t ethernet_frame_t::ether_type() {
    if (f_ether_type)
        return m_ether_type;
    m_ether_type = ((ether_type_1() == ethernet_frame_t::ETHER_TYPE_ENUM_IEEE_802_1Q_TPID) ? (ether_type_2()) : (ether_type_1()));
    f_ether_type = true;
    return m_ether_type;
}