Source code for pcapkit.reassembly.ipv4

# -*- coding: utf-8 -*-
"""IPv4 fragments reassembly

:mod:`pcapkit.reassembly.ipv4` contains
:class:`~pcapkit.reassembly.ipv4.IPv4_Reassembly`
only, which reconstructs fragmented IPv4 packets back to
origin.

Glossary
--------

ipv4.packet
    Data structure for **IPv4 datagram reassembly**
    (:meth:`~pcapkit.reassembly.reassembly.Reassembly.reassembly`)
    is as following:

    .. code:: python

       packet_dict = dict(
         bufid = tuple(
             ipv4.src,                   # source IP address
             ipv4.dst,                   # destination IP address
             ipv4.id,                    # identification
             ipv4.proto,                 # payload protocol type
         ),
         num = frame.number,             # original packet range number
         fo = ipv4.frag_offset,          # fragment offset
         ihl = ipv4.hdr_len,             # internet header length
         mf = ipv4.flags.mf,             # more fragment flag
         tl = ipv4.len,                  # total length, header includes
         header = ipv4.header,           # raw bytearray type header
         payload = ipv4.payload,         # raw bytearray type payload
       )

ipv4.datagram
    Data structure for **reassembled IPv4 datagram** (element from
    :attr:`~pcapkit.reassembly.reassembly.Reassembly.datagram` *tuple*)
    is as following:

    .. code:: python

       (tuple) datagram
        |--> (dict) data
        |     |--> 'NotImplemented' : (bool) True --> implemented
        |     |--> 'index' : (tuple) packet numbers
        |     |               |--> (int) original packet range number
        |     |--> 'packet' : (Optional[bytes]) reassembled IPv4 packet
        |--> (dict) data
        |     |--> 'NotImplemented' : (bool) False --> not implemented
        |     |--> 'index' : (tuple) packet numbers
        |     |               |--> (int) original packet range number
        |     |--> 'header' : (Optional[bytes]) IPv4 header
        |     |--> 'payload' : (Optional[tuple]) partially reassembled IPv4 payload
        |                       |--> (Optional[bytes]) IPv4 payload fragment
        |--> (dict) data ...

ipv4.buffer
    Data structure for internal buffering when performing reassembly algorithms
    (:attr:`~pcapkit.reassembly.reassembly.Reassembly._buffer`) is as following:

    .. code:: python

       (dict) buffer --> memory buffer for reassembly
        |--> (tuple) BUFID : (dict)
        |     |--> ipv4.src       |
        |     |--> ipc6.dst       |
        |     |--> ipv4.label     |
        |     |--> ipv4_frag.next |
        |                         |--> 'TDL' : (int) total data length
        |                         |--> RCVBT : (bytearray) fragment received bit table
        |                         |             |--> (bytes) b'\\x00' -> not received
        |                         |             |--> (bytes) b'\\x01' -> received
        |                         |             |--> (bytes) ...
        |                         |--> 'index' : (list) list of reassembled packets
        |                         |               |--> (int) packet range number
        |                         |--> 'header' : (bytearray) header buffer
        |                         |--> 'datagram' : (bytearray) data buffer, holes set to b'\\x00'
        |--> (tuple) BUFID ...

"""
from pcapkit.reassembly.ip import IP_Reassembly

__all__ = ['IPv4_Reassembly']


class IPv4_Reassembly(IP_Reassembly):
    """Reassembly for IPv4 payload.

    Example:
        >>> from pcapkit.reassembly import IPv4_Reassembly
        # Initialise instance:
        >>> ipv4_reassembly = IPv4_Reassembly()
        # Call reassembly:
        >>> ipv4_reassembly(packet_dict)
        # Fetch result:
        >>> result = ipv4_reassembly.datagram

    """
    ##########################################################################
    # Properties.
    ##########################################################################

    @property
    def name(self):
        """Protocol of current packet.

        :rtype: Literal['Internet Protocol version 4']
        """
        return 'Internet Protocol version 4'

    @property
    def protocol(self):
        """Protocol of current reassembly object.

        :rtype: Literal['IPv4']
        """
        return 'IPv4'