Package: pcapng3
Tool for reading/writing PCAPNG network packet capture filesAlan Thompson, Brocadeathomps@brocade.comPlease see the IETF documentPCAP Next Generation
(pcapng) Capture File FormatPlease also see the projecthome page on GitLabandat PyPI - the Python Package IndexQuick StartPCAPNG files must begin with a Section Header Block:import pcapng.block
import pcapng.linktype
import pcapng.option

pcap_fp = open( 'data.pcapng', 'wb' );

shb_opts = [ pcapng.option.ShbHardware( "Dell" ),
             pcapng.option.ShbOs( "Ubuntu" ),
             pcapng.option.ShbUserAppl( "IntelliJ Idea" ) ]
shb_obj = pcapng.block.SectionHeaderBlock( shb_opts )
shb_packed_bytes = shb_obj.pack()
pcap_fp.write( shb_packed_bytes )  # must be 1st blockwhere the options list may be omitted for this or any other block type. After the SHB, one or more
Interface Description Blocks may be included:idb_opts = [ pcapng.option.IdbName( interface_name ),
             pcapng.option.IdbDescription( "primary interface on host" ),
             pcapng.option.IdbSpeed( 12345 ) ]
idb_obj = pcapng.block.InterfaceDescBlock( linktype.LINKTYPE_ETHERNET, idb_opts )  # optional block
pcap_fp.write( idb_obj.pack() )After the SHB and any optional IDBs, one may include packet information as either Simple Packet
Blocks or Enhanced Packet Blocks:pkt_bytes = get_next_packet( socket_fd )
dbg_print( pkt_bytes )
pcap_fp.write( pcapng.block.SimplePacketBlock( pkt_bytes ).pack() )

pkt_bytes = get_next_packet( socket_fd )
dbg_print( pkt_bytes )

epb_opts = [ pcapng.option.EpbFlags(       [13,14,15,16] ),
             pcapng.option.EpbHash(        'just about any hash spec can go here' ),
             pcapng.option.EpbDropCount(   13 ) ]
pcap_fp.write( pcapng.block.EnhancedPacketBlock( 0, pkt_bytes, len(pkt_bytes), epb_opts ).pack() )Blocks may also be serialized & deserialized in bulk, as seen in the unit tests:def test_blocks_lst():
    blk_lst = [
        # SHB must be 1st block
        pcapng.block.SectionHeaderBlock( [ pcapng.option.ShbHardware( "Dell" ),
                                           pcapng.option.ShbOs( "Ubuntu" ),
                                           pcapng.option.ShbUserAppl( "IntelliJ Idea" ) ] ),
        pcapng.block.InterfaceDescBlock( linktype.LINKTYPE_ETHERNET,
                                        [ pcapng.option.IdbName( "Carrier Pigeon" ),
                                          pcapng.option.IdbDescription( "Something profound here..." ),
                                          pcapng.option.IdbIpv4Addr(     [192, 168, 13, 7], [255, 255, 255, 0] ),
                                          pcapng.option.IdbOs( 'Ubuntu Xenial 16.04.1 LTS' ) ] ),
        pcapng.block.SimplePacketBlock('abc'),
        pcapng.block.EnhancedPacketBlock( 0, "<<<Stand-in for actual packet data>>>"  ),
        pcapng.block.CustomBlockCopyable( pen.BROCADE_PEN, 'User-defined custom data' ),
    ]
    packed_bytes = pcapng.block.pack_all( blk_lst )

    if False:
        pcap_fp = open( 'block_list.pcapng', 'wb' )
        pcap_fp.write( packed_bytes )
        pcap_fp.close()

    util.assert_block32_length( packed_bytes )
    blk_lst_unpacked = pcapng.block.unpack_all( packed_bytes )
    assert blk_lst == blk_lst_unpackedInstallationInstall from the Python Package Index (PyPI):sudo pip install pcapngAPI DocumentationPoint your browser to the included HTML documentation:firefox doc/pcapng/index.html         # or similar (system dependent)Sample ProgramsPlease see the sample programs:isis_agent_pcapng.py    # real-time packet capture from your machine into a PCAPNG file
isis_demo_mrt.py        # same as above but save in Custom Block MRT format
pcapng_timing.py        # capure 1M sample packetsThe program isis_agent_pcapng.py creates an output filedata.pcapng, which isviewable in
Wireshark.The programisis_demo_mrt.pycreates two output filesisis.mrt&isis.pcapng. The first of
thes is in raw MRT format and is not viewable by Wireshark.  For the second file, each raw MRT block
is wrapped in a PCAPNG Custom Block.  The file may be loaded successfully in Wireshark; however,
since Wireshark doesn’t understand the custom format, it produces a blank display.The third programpcapng_timing.pywrites 1 million dummy packets to a PCAPNG file. A flag selects
either Simple Packet Block or Enhanced Packet Block output format.  Execution on a representative
computer yields execution times of ~6 seconds and ~16 seconds for SPB and EPB formats, respectively.Generating DocumentationDocumentation uses thepdoctool.  Note that pdoc generates documentation from the installedpcapngpackage, not directly from thesource code.  To use:sudo pip install pdoc       # install pdoc if not present
./generate-docs.bash        # generate docsEndian ConventionThe PCAPNG specificationmandates that data be saved in the
native endian format of the capturing machine. This avoids the possible need for byte-swapping
during data capture, which may aid in efficiency. However, a reader of a PCAPNG file is obligated to
examine the special BYTE_ORDER_MAGIC field of the Section Header Block in order to determine the
endian convention used in generating the file.  Additionaly, since several PCAPNG files may be
concatenated together to form a larger, valid PCAPNG file, the reader must re-evaluate the endian
convention for each subsequent Section Header Block encountered.Currently, this library does not implement endian-sensitive decoding logic, using native endian
encoding for both writing and reading. The library thus assumes that both the capturing maching and
the reading machine share the same endian conventions.  The library may be extended in the future to
implement the endian-sensitive logic for reading PCAPNG written on foreign hosts.