pcapngWriter

PCAPNG file writer of protocol packets

expand all in page

    Description

    The pcapngWriter object writes generated and recovered protocol packets to a packet capture next generation (PCAPNG) file (.pcapng).

    Creation

    Syntax

    pcapngObj = pcapngWriter
    pcapngObj = pcapngWriter(PropertyName=Value)

    Description

    pcapngObj = pcapngWriter creates a default PCAPNG file writer object.

    pcapngObj = pcapngWriter(PropertyName=Value) sets properties using one or more name-value pair arguments. Enclose each property name in quotes. For example, 'ByteOrder','big-endian' specifies the byte order as big-endian.

    example

    Properties

    expand all

    Note

    The pcapngWriter object does not overwrite the existing PCAP or PCAPNG file. Each time when you create this object, specify a unique PCAP or PCAPNG file name.

    This property is read-only after object creation.

    Name of the PCAPNG file, specified as a character row vector or a string scalar.

    Data Types: char | string

    This property is read-only after object creation.

    Byte order, specified as 'little-endian' or 'big-endian'.

    Data Types: char | string

    This property is read-only after object creation.

    Comment for the PCAPNG file, specified as a character vector or a string scalar.

    Data Types: char | string

    Since R2026a

    Name of the first-in first-out (FIFO) pipe file (also known as a named pipe), specified as a character row vector or string scalar. This value is an absolute or relative path to a pipe that you create outside MATLAB.

    Dependencies

    To enable this property, do not specify FileName.

    Data Types: char | string

    Object Functions

    expand all

    writeWrite protocol packet data to PCAP or PCAPNG file
    writeCustomBlockWrite custom block to PCAPNG file
    writeInterfaceDescriptionBlockWrite interface description block to PCAPNG file

    Examples

    collapse all

    This example uses:

    Open Live Script

    Create a PCAPNG file writer object, specifying the name of the PCAPNG file.

    pcapngObj = pcapngWriter('FileName','sample');

    Write the interface block for 5G New Radio (NR). 5G NR packets do not have a valid link type. As per Tcpdump, if a valid link type is not present, specify the link type of SLL packet.

    interface = '5GNR';                                       % Interface name
linkType = 113;                                           % Link type of SLL packet
timestamp = 300;                                          % Timestamp
interfaceID = writeInterfaceDescriptionBlock(pcapngObj,linkType,interface);

    5G NR packets are not directly supported by Wireshark. To enable Wireshark to parse 5G NR packets, add encapsulation and metadata to the 5G NR packet.

    payload = [59; 205];                                      % MAC subPDU (contains truncated buffer status report (BSR) control element)
radioType = 1;                                            % Frequency division duplexing
linkDir   = 0;                                            % Uplink packet
rntiType = 3;                                             % Cell-RNTI
startString = [109; 97; 99; 45; 110; 114];                % Tag to indicate start of NR MAC signature
payloadTag = 1;                                           % Payload tag for NR MAC packets
signature = [startString; radioType; linkDir; rntiType];
macNRInfoPacket = [signature; payloadTag; payload];

    Construct a user datagram protocol (UDP) header.

    udpPacketLength = 8 + length(macNRInfoPacket);            % Length of header (8 bytes) and payload
udpHeader = [163; 76;                                     % Source port number
    39; 15;                                               % Destination port number
    fix(udpPacketLength/256); mod(udpPacketLength,256);   % Total length of UDP packet
    0; 0];                                                % Checksum

    Construct an IPv4 header.

    ipPacketLength = 20 + udpPacketLength;                    % Length of header (20 bytes) and payload
ipHeader = [69;                                           % Version of IP protocol and priority or traffic class
    0;                                                    % Type of service
    fix(ipPacketLength/256);mod(ipPacketLength,256);      % Total length of the IPv4 packet
    0; 1;                                                 % Identification
    0; 0;                                                 % Flags and fragmentation offset
    64;                                                   % Time to live in seconds
    17;                                                   % Protocol number
    0; 0;                                                 % Header checksum
    127; 0; 0; 1;                                         % Source IP address
    127; 0; 0; 1];                                        % Destination IP address

    Construct an SLL header.

    sllHeader = [0; 0;                                        % Packet type
    3; 4;                                                 % Address resolution protocol hardware (ARPHRD) type
    0; 0;                                                 % Link layer address length
    0; 0; 0; 0; 0; 0; 0; 0;                               % Link layer address
    8; 0];                                                % Protocol type

    Construct an 5G NR packet by adding encapsulation and metadata.

    packet = [sllHeader; ipHeader; udpHeader; macNRInfoPacket];

    Write the 5G NR packet to the PCAPNG file.

    packetComment = 'This is NR MAC packet';                  % Packet comment
write(pcapngObj,packet,timestamp,interfaceID,'PacketComment',packetComment);

    This example uses:

    Open Live Script

    Create a PCAPNG file writer object, specifying the name of the PCAPNG file. 

    pcapngObj = pcapngWriter('FileName','writeWLANpacket');

    Write the interface block for WLAN.

    interfaceName = 'WLAN';
wlanLinkType = 105;
interfaceId = writeInterfaceDescriptionBlock(pcapngObj,wlanLinkType, ...
    interfaceName);

    Specify a WLAN packet.

    mpdu = 'B4000000FFFFFFFFFFFF00123456789BA79A5B28';

    Specify the packet comment. Write the WLAN packet to the PCAPNG file, specifying the packet comment.

    timestamp = 0; % Number of microseconds
packetComment = 'This is the first packet';
write(pcapngObj,mpdu,timestamp,interfaceId,'PacketComment', ...
    packetComment);

    This example uses:

    Open Live Script

    Create a PCAPNG file writer object, specifying the name of the PCAPNG file. 

    pcapngObj = pcapngWriter('FileName','writeWLANBLEpackets');

    Write the interface block for WLAN.

    interfaceName = 'WLAN';
wlanLinkType = 105;
interfaceId = writeInterfaceDescriptionBlock(pcapngObj,wlanLinkType, ...
    interfaceName);

    Specify a WLAN packet.

    mpdu = 'B4000000FFFFFFFFFFFF00123456789BA79A5B28';

    Specify the packet comment. Write the WLAN packet to the PCAPNG file, specifying the packet comment.

    timestamp = 0; % Number of microseconds
packetComment = 'This is a WLAN packet';
write(pcapngObj,mpdu,timestamp,interfaceId,'PacketComment', ...
    packetComment);

    Write the interface block for Bluetooth low energy (BLE).

    interfaceName = 'BLE';
bleLinkType = 251;
interfaceId = writeInterfaceDescriptionBlock(pcapngObj,bleLinkType, ...
    interfaceName);

    Specify a BLE packet.

    llpacket = '42BC13E206120E00050014010A001F0040001700170000007D47C0';

    Specify the packet comment. Write the BLE packet to the PCAPNG file, specifying the packet comment.

    timestamp = 0; % Number of microseconds
packetComment = 'This is a BLE packet';
write(pcapngObj,llpacket,timestamp,interfaceId,'PacketComment', ...
    packetComment);

    This example uses:

    Open Live Script

    Create a PCAPNG file writer object, specifying the name of the PCAPNG file. Specify the Bluetooth LE link type.

    pcapngObj = pcapngWriter('FileName','BLELLCapture');

    Write an interface description block for Bluetooth LE.

    interfaceName = 'Bluetooth LE interface';
bleLinkType = 251;
interfaceId = writeInterfaceDescriptionBlock(pcapngObj,bleLinkType, ...
    interfaceName);

    Specify a Bluetooth LE LL packet.

    llpacket = '42BC13E206120E00050014010A001F0040001700170000007D47C0';

    Write the Bluetooth LE LL packet to the PCAPNG format file.

    timestamp = 0;                                 % Packet arrival time in POSIX® microseconds elapsed since 1/1/1970
packetComment = 'This is a Bluetooth LE packet';
write(pcapngObj,llpacket,timestamp,interfaceId,'PacketComment', ...
    packetComment);

    References

    [1] Tuexen, M. “PCAP Next Generation (Pcapng) Capture File Format.” 2020. https://www.ietf.org/.

    [2] Group, The Tcpdump. “Tcpdump/Libpcap Public Repository.” Accessed May 20, 2020. https://www.tcpdump.org.

    [3] “Development/LibpcapFileFormat - The Wireshark Wiki.” Accessed May 20, 2020. https://www.wireshark.org.

    Extended Capabilities

    expand all

    C/C++ Code Generation
    Generate C and C++ code using MATLAB® Coder™.

    GPU Code Generation
    Generate CUDA® code for NVIDIA® GPUs using GPU Coder™.

    Version History

    Introduced in R2020b

    expand all

    See Also

    Objects