.pcap / .pcapdump file format: C++98/STL parsing library

PCAP (named after libpcap / winpcap) is a popular format for saving network traffic grabbed by network sniffers. It is typically produced by tools like tcpdump or Wireshark.

File extension

["pcap", "pcapdump"]

KS implementation details

License: CC0-1.0
Minimal Kaitai Struct required: 0.8

References

This page hosts a formal specification of .pcap / .pcapdump file format 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++98/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.["pcap", "pcapdump"]", 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:
    pcap_t data(&ks);
    

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

data.hdr() // => get hdr

C++98/STL source code to parse .pcap / .pcapdump file format

pcap.h

#ifndef PCAP_H_
#define PCAP_H_

// 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 "ethernet_frame.h"
#include "packet_ppi.h"
#include <vector>

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

/**
 * PCAP (named after libpcap / winpcap) is a popular format for saving
 * network traffic grabbed by network sniffers. It is typically
 * produced by tools like [tcpdump](https://www.tcpdump.org/) or
 * [Wireshark](https://www.wireshark.org/).
 * \sa http://wiki.wireshark.org/Development/LibpcapFileFormat Source
 */

class pcap_t : public kaitai::kstruct {

public:
    class header_t;
    class packet_t;

    enum linktype_t {
        LINKTYPE_NULL_LINKTYPE = 0,
        LINKTYPE_ETHERNET = 1,
        LINKTYPE_AX25 = 3,
        LINKTYPE_IEEE802_5 = 6,
        LINKTYPE_ARCNET_BSD = 7,
        LINKTYPE_SLIP = 8,
        LINKTYPE_PPP = 9,
        LINKTYPE_FDDI = 10,
        LINKTYPE_PPP_HDLC = 50,
        LINKTYPE_PPP_ETHER = 51,
        LINKTYPE_ATM_RFC1483 = 100,
        LINKTYPE_RAW = 101,
        LINKTYPE_C_HDLC = 104,
        LINKTYPE_IEEE802_11 = 105,
        LINKTYPE_FRELAY = 107,
        LINKTYPE_LOOP = 108,
        LINKTYPE_LINUX_SLL = 113,
        LINKTYPE_LTALK = 114,
        LINKTYPE_PFLOG = 117,
        LINKTYPE_IEEE802_11_PRISM = 119,
        LINKTYPE_IP_OVER_FC = 122,
        LINKTYPE_SUNATM = 123,
        LINKTYPE_IEEE802_11_RADIOTAP = 127,
        LINKTYPE_ARCNET_LINUX = 129,
        LINKTYPE_APPLE_IP_OVER_IEEE1394 = 138,
        LINKTYPE_MTP2_WITH_PHDR = 139,
        LINKTYPE_MTP2 = 140,
        LINKTYPE_MTP3 = 141,
        LINKTYPE_SCCP = 142,
        LINKTYPE_DOCSIS = 143,
        LINKTYPE_LINUX_IRDA = 144,
        LINKTYPE_USER0 = 147,
        LINKTYPE_USER1 = 148,
        LINKTYPE_USER2 = 149,
        LINKTYPE_USER3 = 150,
        LINKTYPE_USER4 = 151,
        LINKTYPE_USER5 = 152,
        LINKTYPE_USER6 = 153,
        LINKTYPE_USER7 = 154,
        LINKTYPE_USER8 = 155,
        LINKTYPE_USER9 = 156,
        LINKTYPE_USER10 = 157,
        LINKTYPE_USER11 = 158,
        LINKTYPE_USER12 = 159,
        LINKTYPE_USER13 = 160,
        LINKTYPE_USER14 = 161,
        LINKTYPE_USER15 = 162,
        LINKTYPE_IEEE802_11_AVS = 163,
        LINKTYPE_BACNET_MS_TP = 165,
        LINKTYPE_PPP_PPPD = 166,
        LINKTYPE_GPRS_LLC = 169,
        LINKTYPE_GPF_T = 170,
        LINKTYPE_GPF_F = 171,
        LINKTYPE_LINUX_LAPD = 177,
        LINKTYPE_BLUETOOTH_HCI_H4 = 187,
        LINKTYPE_USB_LINUX = 189,
        LINKTYPE_PPI = 192,
        LINKTYPE_IEEE802_15_4 = 195,
        LINKTYPE_SITA = 196,
        LINKTYPE_ERF = 197,
        LINKTYPE_BLUETOOTH_HCI_H4_WITH_PHDR = 201,
        LINKTYPE_AX25_KISS = 202,
        LINKTYPE_LAPD = 203,
        LINKTYPE_PPP_WITH_DIR = 204,
        LINKTYPE_C_HDLC_WITH_DIR = 205,
        LINKTYPE_FRELAY_WITH_DIR = 206,
        LINKTYPE_IPMB_LINUX = 209,
        LINKTYPE_IEEE802_15_4_NONASK_PHY = 215,
        LINKTYPE_USB_LINUX_MMAPPED = 220,
        LINKTYPE_FC_2 = 224,
        LINKTYPE_FC_2_WITH_FRAME_DELIMS = 225,
        LINKTYPE_IPNET = 226,
        LINKTYPE_CAN_SOCKETCAN = 227,
        LINKTYPE_IPV4 = 228,
        LINKTYPE_IPV6 = 229,
        LINKTYPE_IEEE802_15_4_NOFCS = 230,
        LINKTYPE_DBUS = 231,
        LINKTYPE_DVB_CI = 235,
        LINKTYPE_MUX27010 = 236,
        LINKTYPE_STANAG_5066_D_PDU = 237,
        LINKTYPE_NFLOG = 239,
        LINKTYPE_NETANALYZER = 240,
        LINKTYPE_NETANALYZER_TRANSPARENT = 241,
        LINKTYPE_IPOIB = 242,
        LINKTYPE_MPEG_2_TS = 243,
        LINKTYPE_NG40 = 244,
        LINKTYPE_NFC_LLCP = 245,
        LINKTYPE_INFINIBAND = 247,
        LINKTYPE_SCTP = 248,
        LINKTYPE_USBPCAP = 249,
        LINKTYPE_RTAC_SERIAL = 250,
        LINKTYPE_BLUETOOTH_LE_LL = 251,
        LINKTYPE_NETLINK = 253,
        LINKTYPE_BLUETOOTH_LINUX_MONITOR = 254,
        LINKTYPE_BLUETOOTH_BREDR_BB = 255,
        LINKTYPE_BLUETOOTH_LE_LL_WITH_PHDR = 256,
        LINKTYPE_PROFIBUS_DL = 257,
        LINKTYPE_PKTAP = 258,
        LINKTYPE_EPON = 259,
        LINKTYPE_IPMI_HPM_2 = 260,
        LINKTYPE_ZWAVE_R1_R2 = 261,
        LINKTYPE_ZWAVE_R3 = 262,
        LINKTYPE_WATTSTOPPER_DLM = 263,
        LINKTYPE_ISO_14443 = 264
    };

    pcap_t(kaitai::kstream* p__io, kaitai::kstruct* p__parent = 0, pcap_t* p__root = 0);

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

public:
    ~pcap_t();

    /**
     * \sa https://wiki.wireshark.org/Development/LibpcapFileFormat#Global_Header Source
     */

    class header_t : public kaitai::kstruct {

    public:

        header_t(kaitai::kstream* p__io, pcap_t* p__parent = 0, pcap_t* p__root = 0);

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

    public:
        ~header_t();

    private:
        std::string m_magic_number;
        uint16_t m_version_major;
        uint16_t m_version_minor;
        int32_t m_thiszone;
        uint32_t m_sigfigs;
        uint32_t m_snaplen;
        linktype_t m_network;
        pcap_t* m__root;
        pcap_t* m__parent;

    public:
        std::string magic_number() const { return m_magic_number; }
        uint16_t version_major() const { return m_version_major; }
        uint16_t version_minor() const { return m_version_minor; }

        /**
         * Correction time in seconds between UTC and the local
         * timezone of the following packet header timestamps.
         */
        int32_t thiszone() const { return m_thiszone; }

        /**
         * In theory, the accuracy of time stamps in the capture; in
         * practice, all tools set it to 0.
         */
        uint32_t sigfigs() const { return m_sigfigs; }

        /**
         * The "snapshot length" for the capture (typically 65535 or
         * even more, but might be limited by the user), see: incl_len
         * vs. orig_len.
         */
        uint32_t snaplen() const { return m_snaplen; }

        /**
         * Link-layer header type, specifying the type of headers at
         * the beginning of the packet.
         */
        linktype_t network() const { return m_network; }
        pcap_t* _root() const { return m__root; }
        pcap_t* _parent() const { return m__parent; }
    };

    /**
     * \sa https://wiki.wireshark.org/Development/LibpcapFileFormat#Record_.28Packet.29_Header Source
     */

    class packet_t : public kaitai::kstruct {

    public:

        packet_t(kaitai::kstream* p__io, pcap_t* p__parent = 0, pcap_t* p__root = 0);

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

    public:
        ~packet_t();

    private:
        uint32_t m_ts_sec;
        uint32_t m_ts_usec;
        uint32_t m_incl_len;
        uint32_t m_orig_len;
        kaitai::kstruct* m_body;
        bool n_body;

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

    private:
        pcap_t* m__root;
        pcap_t* m__parent;
        std::string m__raw_body;
        kaitai::kstream* m__io__raw_body;

    public:
        uint32_t ts_sec() const { return m_ts_sec; }
        uint32_t ts_usec() const { return m_ts_usec; }

        /**
         * Number of bytes of packet data actually captured and saved in the file.
         */
        uint32_t incl_len() const { return m_incl_len; }

        /**
         * Length of the packet as it appeared on the network when it was captured.
         */
        uint32_t orig_len() const { return m_orig_len; }

        /**
         * \sa https://wiki.wireshark.org/Development/LibpcapFileFormat#Packet_Data Source
         */
        kaitai::kstruct* body() const { return m_body; }
        pcap_t* _root() const { return m__root; }
        pcap_t* _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; }
    };

private:
    header_t* m_hdr;
    std::vector<packet_t*>* m_packets;
    pcap_t* m__root;
    kaitai::kstruct* m__parent;

public:
    header_t* hdr() const { return m_hdr; }
    std::vector<packet_t*>* packets() const { return m_packets; }
    pcap_t* _root() const { return m__root; }
    kaitai::kstruct* _parent() const { return m__parent; }
};

#endif  // PCAP_H_

pcap.cpp

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

#include "pcap.h"
#include "kaitai/exceptions.h"

pcap_t::pcap_t(kaitai::kstream* p__io, kaitai::kstruct* p__parent, pcap_t* p__root) : kaitai::kstruct(p__io) {
    m__parent = p__parent;
    m__root = this;
    m_hdr = 0;
    m_packets = 0;

    try {
        _read();
    } catch(...) {
        _clean_up();
        throw;
    }
}

void pcap_t::_read() {
    m_hdr = new header_t(m__io, this, m__root);
    m_packets = new std::vector<packet_t*>();
    {
        int i = 0;
        while (!m__io->is_eof()) {
            m_packets->push_back(new packet_t(m__io, this, m__root));
            i++;
        }
    }
}

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

void pcap_t::_clean_up() {
    if (m_hdr) {
        delete m_hdr; m_hdr = 0;
    }
    if (m_packets) {
        for (std::vector<packet_t*>::iterator it = m_packets->begin(); it != m_packets->end(); ++it) {
            delete *it;
        }
        delete m_packets; m_packets = 0;
    }
}

pcap_t::header_t::header_t(kaitai::kstream* p__io, pcap_t* p__parent, pcap_t* p__root) : kaitai::kstruct(p__io) {
    m__parent = p__parent;
    m__root = p__root;

    try {
        _read();
    } catch(...) {
        _clean_up();
        throw;
    }
}

void pcap_t::header_t::_read() {
    m_magic_number = m__io->read_bytes(4);
    if (!(magic_number() == std::string("\xD4\xC3\xB2\xA1", 4))) {
        throw kaitai::validation_not_equal_error<std::string>(std::string("\xD4\xC3\xB2\xA1", 4), magic_number(), _io(), std::string("/types/header/seq/0"));
    }
    m_version_major = m__io->read_u2le();
    m_version_minor = m__io->read_u2le();
    m_thiszone = m__io->read_s4le();
    m_sigfigs = m__io->read_u4le();
    m_snaplen = m__io->read_u4le();
    m_network = static_cast<pcap_t::linktype_t>(m__io->read_u4le());
}

pcap_t::header_t::~header_t() {
    _clean_up();
}

void pcap_t::header_t::_clean_up() {
}

pcap_t::packet_t::packet_t(kaitai::kstream* p__io, pcap_t* p__parent, pcap_t* p__root) : kaitai::kstruct(p__io) {
    m__parent = p__parent;
    m__root = p__root;
    m__io__raw_body = 0;

    try {
        _read();
    } catch(...) {
        _clean_up();
        throw;
    }
}

void pcap_t::packet_t::_read() {
    m_ts_sec = m__io->read_u4le();
    m_ts_usec = m__io->read_u4le();
    m_incl_len = m__io->read_u4le();
    m_orig_len = m__io->read_u4le();
    n_body = true;
    switch (_root()->hdr()->network()) {
    case pcap_t::LINKTYPE_PPI: {
        n_body = false;
        m__raw_body = m__io->read_bytes(incl_len());
        m__io__raw_body = new kaitai::kstream(m__raw_body);
        m_body = new packet_ppi_t(m__io__raw_body);
        break;
    }
    case pcap_t::LINKTYPE_ETHERNET: {
        n_body = false;
        m__raw_body = m__io->read_bytes(incl_len());
        m__io__raw_body = new kaitai::kstream(m__raw_body);
        m_body = new ethernet_frame_t(m__io__raw_body);
        break;
    }
    default: {
        m__raw_body = m__io->read_bytes(incl_len());
        break;
    }
    }
}

pcap_t::packet_t::~packet_t() {
    _clean_up();
}

void pcap_t::packet_t::_clean_up() {
    if (!n_body) {
        if (m__io__raw_body) {
            delete m__io__raw_body; m__io__raw_body = 0;
        }
        if (m_body) {
            delete m_body; m_body = 0;
        }
    }
}