IPv4.pack() - Code Metrics - Inspection of "Adding yala support" - macartur/python-openflow - Measure and Improve Code Quality continuously with Scrutinizer

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Pull Request — master (#4)

by macartur

created 2017-09-05 20:22 UTC

IPv4.pack() B

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"""Basic Network packet types.

Defines and Implements Basic Network packet types , such as Ethertnet and LLDP.
"""

from pyof.foundation.base import GenericStruct
from pyof.foundation.basic_types import (
    BinaryData, HWAddress, IPAddress, UBInt8, UBInt16)
from pyof.foundation.constants import VLAN_TPID
from pyof.foundation.exceptions import PackException, UnpackException

__all__ = ('ARP', 'Ethernet', 'GenericTLV', 'IPv4', 'VLAN', 'TLVWithSubType',
           'LLDP')


class ARP(GenericStruct):
    """ARP packet "struct".

    Contains fields for an ARP packet's header and data.
    Designed for Ethernet and IPv4 only: needs to have some attributes changed
    for other HTYPE and PTYPE implementations.
    Must be encapsulated inside an Ethernet frame.
    """

    htype = UBInt16()
    ptype = UBInt16()
    hlen = UBInt8()
    plen = UBInt8()
    oper = UBInt16()
    sha = HWAddress()
    spa = IPAddress()
    tha = HWAddress()
    tpa = IPAddress()

    def __init__(self, htype=1, ptype=0x800, hlen=6, plen=4, oper=1,
                 sha='00:00:00:00:00:00', spa='0.0.0.0',
                 tha="00:00:00:00:00:00", tpa='0.0.0.0'):
        """Create a ARP with the parameters below.

        Args:
            htype (int): Hardware protocol type. Defaults to 1 for Ethernet.
            ptype (int): Network protocol type. Defaults to 0x800 for IPv4.
            hlen (int): Length of the hardware address. Defaults to 6 for MAC
                        addresses.
            plen (int): Length of the networking protocol address. Defaults to
                        4 for IPv4 addresses.
            oper (int): Determines the operation for this ARP packet. Must be 1
                        for ARP request or 2 for ARP reply. Defaults to 1.
            sha (str): Sender hardware address. Defaults to
                       '00:00:00:00:00:00'.
            spa (str): Sender protocol address. Defaults to '0.0.0.0'.
            tha (str): Target hardware address. Defaults to
                       '00:00:00:00:00:00'.
            tpa (str): Target protocol address. Defaults to '0.0.0.0'.
        """
        super().__init__()
        self.htype = htype
        self.ptype = ptype
        self.hlen = hlen
        self.plen = plen
        self.oper = oper
        self.sha = sha
        self.spa = spa
        self.tha = tha
        self.tpa = tpa

    def is_valid(self):
        """Assure the ARP contains Ethernet and IPv4 information."""
        return self.htype == 1 and self.ptype == 0x800

    def unpack(self, buff, offset=0):
        """Unpack a binary struct into this object's attributes.

        Return the values instead of the lib's basic types.
        Check if the protocols involved are Ethernet and IPv4. Other protocols
        are currently not supported.

        Args:
            buff (bytes): Binary buffer.
            offset (int): Where to begin unpacking.

        Raises:
            :exc:`~.exceptions.UnpackException`: If unpack fails.

        """
        super().unpack(buff, offset)
        if not self.is_valid():
            raise UnpackException("Unsupported protocols in ARP packet")


class VLAN(GenericStruct):
    """802.1q VLAN header."""

    #: tpid (:class:`UBInt16`): Tag Protocol Identifier
    tpid = UBInt16(VLAN_TPID)
    #: _tci (:class:`UBInt16`): Tag Control Information - has the
    #: Priority Code Point, DEI/CFI bit and the VLAN ID
    _tci = UBInt16()

    def __init__(self, pcp=None, cfi=None, vid=None):
        """Create a VLAN with the parameters below.

        If no arguments are set for a particular instance, it is interpreted as
        abscence of VLAN information, and the pack() method will return an
        empty binary string.

        Args:
            tpid (int): Tag Protocol Identifier. Defaults to 0x8100 for 802.1q.
            pcp (int): 802.1p Priority Code Point. Defaults to 0 for Best
                       Effort Queue.
            cfi (int): Canonical Format Indicator. Defaults to 0 for Ethernet.
            vid (int): VLAN ID. If no VLAN is specified, value is 0.
        """
        super().__init__()
        self.tpid = VLAN_TPID
        self.pcp = pcp
        self.cfi = cfi
        self.vid = vid

    def pack(self, value=None):
        """Pack the struct in a binary representation.

        Merge some fields to ensure correct packing.

        If no arguments are set for a particular instance, it is interpreted as
        abscence of VLAN information, and the pack() method will return an
        empty binary string.

        Returns:
            bytes: Binary representation of this instance.

        """
        if isinstance(value, type(self)):
            return value.pack()

        if self.pcp is None and self.cfi is None and self.vid is None:
            return b''
        self.pcp = self.pcp if self.pcp is not None else 0
        self.cfi = self.cfi if self.cfi is not None else 0
        self.vid = self.vid if self.vid is not None else 0
        self._tci = self.pcp << 13 | self.cfi << 12 | self.vid
        return super().pack()

    def _validate(self):
        """Assure this is a 802.1q VLAN header instance."""
        if self.tpid.value != VLAN_TPID:
            raise UnpackException
        return

    def unpack(self, buff, offset=0):
        """Unpack a binary struct into this object's attributes.

        Return the values instead of the lib's basic types.

        After unpacking, the abscence of a `tpid` value causes the assignment
        of None to the field values to indicate that there is no VLAN
        information.

        Args:
            buff (bytes): Binary buffer.
            offset (int): Where to begin unpacking.

        Raises:
            :exc:`~.exceptions.UnpackException`: If unpack fails.

        """
        super().unpack(buff, offset)
        if self.tpid.value:
            self._validate()
            self.tpid = self.tpid.value
            self.pcp = self._tci.value >> 13
            self.cfi = (self._tci.value >> 12) & 1
            self.vid = self._tci.value & 4095
        else:
            self.tpid = VLAN_TPID
            self.pcp = None
            self.cfi = None
            self.vid = None


class Ethernet(GenericStruct):
    """Ethernet "struct".

    Objects of this class represents an ethernet packet. It contains the
    'Ethernet header', composed by destination (MAC), source (MAC), type
    (EtherType)[1] and the payload of the packet, as binary data.

    This class does not consider the Ethernet 'Preamble' or the 'CRC'.

    There is also a get_hash method, that hashes the binary representation of
    the object so we can have a unique representation of the ethernet packet,
    so we can keep a track of ethernet packets being flooded over the network.

    [1] EtherTypes:
    http://www.iana.org/assignments/ieee-802-numbers/ieee-802-numbers.xhtml#ieee-802-numbers-1
    """

    destination = HWAddress()
    source = HWAddress()
    vlan = VLAN()
    ether_type = UBInt16()
    data = BinaryData()

    def __init__(self, destination=None,
                 source=None, vlan=VLAN(), ether_type=None, data=b''):
        """Create an instance and set its attributes.

        Args:
            destination (:class:`~pyof.foundation.basic_types.HWAddress`):
                The final destination MAC address.
            source (:class:`~pyof.foundation.basic_types.HWAddress`):
                The source Mac address of the packet.
            ether_type (:class:`~pyof.foundation.basic_types.UBInt16`):
                The EtherType of packet.
            data (:class:`~pyof.foundation.basic_types.BinaryData`):
                The content of the packet in binary format.
        """
        super().__init__()
        self.destination = destination
        self.source = source
        self.vlan = vlan
        self.ether_type = ether_type
        self.data = data

    def get_hash(self):
        """Calculate a hash and returns it.

        Returns:
            int: Integer value that identifies this instance.

        """
        return hash(self.pack())

    def unpack(self, buff, offset=0):
        """Unpack a binary message into this object's attributes.

        Unpack the binary value *buff* and update this object attributes based
        on the results.

        Ethernet headers may have VLAN tags. If no VLAN tag is found, a
        'wildcard VLAN tag' is inserted to assure correct unpacking.

        Args:
            buff (bytes): Binary data package to be unpacked.
            offset (int): Where to begin unpacking.

        Raises:
            UnpackException: If there is a struct unpacking error.

        """
        # Checking if the EtherType bytes are actually equal to VLAN_TPID -
        # indicating that the packet is tagged. If it is not, we insert the
        # equivalent to 'NULL VLAN data' (\x00\x00\x00\x00) to enable the
        # correct unpacking process.
        if buff[12:16] != VLAN_TPID.to_bytes(2, 'big'):
            buff = buff[0:12] + b'\x00\x00\x00\x00' + buff[12:]

        super().unpack(buff, offset)


class GenericTLV(GenericStruct):
    """TLV structure of LLDP packets.

    This is a Type, Length and Value (TLV) struct.

    The LLDP/TLV definition states that the Type field have 7 bits, while
    the length have 9 bits. The Value must be between 0-511 octets.

    Internally, on the instances of this class, the Type is a integer
    (0-127) and the Length is dynamically calculated based on the current
    type and value.
    """

    def __init__(self, tlv_type=127, value=BinaryData()):
        """Create an instance and set its attributes.

        Args:
            tlv_type (int): Type used by this class. Defaults to 127.
            value (:class:`~pyof.foundation.basic_types.BinaryData`):
                Value stored by GenericTLV.
        """
        super().__init__()
        self.tlv_type = tlv_type
        self._value = value

    @property
    def value(self):
        """Return the value stored by GenericTLV.

        Returns:
            :class:`~pyof.foundation.basic_types.BinaryData`:
                Value stored by GenericTLV.

        """
        return self._value

    @property
    def length(self):
        """Return the length of value stored by GenericTLV.

        Returns:
            int: Value length in bytes.

        """
        return len(self.value.pack())

    @property
    def header(self):
        """Header of the TLV Packet.

        The header is composed by the Type (7 bits) and Length (9 bits),
        summing up 16 bits. To achieve that, we need to do some bitshift
        operations.

        Returns:
            :class:`~pyof.foundation.basic_types.UBInt16`:
                Result after all operations.

        """
        return UBInt16(((self.tlv_type & 127) << 9) | (self.length & 511))

    def pack(self, value=None):
        """Pack the TLV in a binary representation.

        Returns:
            bytes: Binary representation of the struct object.

        Raises:
            :exc:`~.exceptions.ValidationError`: If validation fails.

        """
        if value is None:
            output = self.header.pack()
            output += self.value.pack()
            return output

        elif isinstance(value, type(self)):
            return value.pack()
        else:
            msg = "{} is not an instance of {}".format(value,
                                                       type(self).__name__)
            raise PackException(msg)

    def unpack(self, buff, offset=0):
        """Unpack a binary message into this object's attributes.

        Unpack the binary value *buff* and update this object attributes based
        on the results.

        Args:
            buff (bytes): Binary data package to be unpacked.
            offset (int): Where to begin unpacking.

        Raises:
            Exception: If there is a struct unpacking error.

        """
        header = UBInt16()
        header.unpack(buff[offset:offset+2])
        self.tlv_type = header.value >> 9
        length = header.value & 511
        begin, end = offset + 2, offset + 2 + length
        self._value = BinaryData(buff[begin:end])

    def get_size(self, value=None):
        """Return struct size.

        Returns:
            int: Returns the struct size based on inner attributes.

        """
        if isinstance(value, type(self)):
            return value.get_size()

        return 2 + self.length


class IPv4(GenericStruct):
    """IPv4 packet "struct".

    Contains all fields of an IP version 4 packet header, plus the upper layer
    content as binary data.
    Some of the fields were merged together because of their size being
    inferior to 8 bits. They are represented as a single class attribute, but
    pack/unpack methods will take into account the values in individual
    instance attributes.
    """

    #: _version_ihl (:class:`UBInt8`): IP protocol version + Internet Header
    #: Length (words)
    _version_ihl = UBInt8()
    #: _dscp_ecn (:class:`UBInt8`): Differentiated Services Code Point
    #: (ToS - Type of Service) + Explicit Congestion Notification
    _dscp_ecn = UBInt8()
    #: length (:class:`UBInt16`): IP packet length (bytes)
    length = UBInt16()
    #: identification (:class:`UBInt16`): Packet ID - common to all fragments
    identification = UBInt16()
    #: _flags_offset (:class:`UBInt16`): Fragmentation flags + fragmentation
    #: offset
    _flags_offset = UBInt16()
    #: ttl (:class:`UBInt8`): Packet time-to-live
    ttl = UBInt8()
    #: protocol (:class:`UBInt8`): Upper layer protocol number
    protocol = UBInt8()
    #: checksum (:class:`UBInt16`): Header checksum
    checksum = UBInt16()
    #: source (:class:`IPAddress`): Source IPv4 address
    source = IPAddress()
    #: destination (:class:`IPAddress`): Destination IPv4 address
    destination = IPAddress()
    #: options (:class:`BinaryData`): IP Options - up to 320 bits, always
    #: padded to 32 bits
    options = BinaryData()
    #: data (:class:`BinaryData`): Packet data
    data = BinaryData()

    def __init__(self, version=4, ihl=5, dscp=0, ecn=0, length=0,
                 identification=0, flags=0, offset=0, ttl=255, protocol=0,
                 checksum=0, source="0.0.0.0", destination="0.0.0.0",
                 options=b'', data=b''):
        """Instanciate a IPv4 with the parameters below.

        Args:
            version (int): IP protocol version. Defaults to 4.
            ihl (int): Internet Header Length. Default is 5.
            dscp (int): Differentiated Service Code Point. Defaults to 0.
            ecn (int): Explicit Congestion Notification. Defaults to 0.
            length (int): IP packet length in bytes. Defaults to 0.
            identification (int): Packet Id. Defaults to 0.
            flags (int): IPv4 Flags. Defults 0.
            offset (int): IPv4 offset. Defaults to 0.
            ttl (int): Packet time-to-live. Defaults to 255
            protocol (int): Upper layer protocol number. Defaults to 0.
            checksum (int): Header checksum. Defaults to 0.
            source (str): Source IPv4 address. Defaults to "0.0.0.0"
            destination (str): Destination IPv4 address. Defaults to "0.0.0.0"
            options (bytes): IP options. Defaults to empty bytes.
            data (bytes): Packet data. Defaults to empty bytes.
        """
        super().__init__()
        self.version = version
        self.ihl = ihl
        self.dscp = dscp
        self.ecn = ecn
        self.length = length
        self.identification = identification
        self.flags = flags
        self.offset = offset
        self.ttl = ttl
        self.protocol = protocol
        self.checksum = checksum
        self.source = source
        self.destination = destination
        self.options = options
        self.data = data

    def _update_checksum(self):
        """Update the packet checksum to enable integrity check."""
        source_list = [int(octet) for octet in self.source.split(".")]
        destination_list = [int(octet) for octet in
                            self.destination.split(".")]
        source_upper = (source_list[0] << 8) + source_list[1]
        source_lower = (source_list[2] << 8) + source_list[3]
        destination_upper = (destination_list[0] << 8) + destination_list[1]
        destination_lower = (destination_list[2] << 8) + destination_list[3]

        block_sum = ((self._version_ihl << 8 | self._dscp_ecn) + self.length +
                     self.identification + self._flags_offset +
                     (self.ttl << 8 | self.protocol) + source_upper +
                     source_lower + destination_upper + destination_lower)

        while block_sum > 65535:
            carry = block_sum >> 16
            block_sum = (block_sum & 65535) + carry

        self.checksum = ~block_sum & 65535

    def pack(self, value=None):
        """Pack the struct in a binary representation.

        Merge some fields to ensure correct packing.

        Returns:
            bytes: Binary representation of this instance.

        """
        # Set the correct IHL based on options size
        if self.options:
            self.ihl += int(len(self.options) / 4)

        # Set the correct packet length based on header length and data
        self.length = int(self.ihl * 4 + len(self.data))

        self._version_ihl = self.version << 4 | self.ihl
        self._dscp_ecn = self.dscp << 2 | self.ecn
        self._flags_offset = self.flags << 13 | self.offset

        # Set the checksum field before packing
        self._update_checksum()

        return super().pack()

    def unpack(self, buff, offset=0):
        """Unpack a binary struct into this object's attributes.

        Return the values instead of the lib's basic types.

        Args:
            buff (bytes): Binary buffer.
            offset (int): Where to begin unpacking.

        Raises:
            :exc:`~.exceptions.UnpackException`: If unpack fails.

        """
        super().unpack(buff, offset)

        self.version = self._version_ihl.value >> 4
        self.ihl = self._version_ihl.value & 15
        self.dscp = self._dscp_ecn.value >> 2
        self.ecn = self._dscp_ecn.value & 3
        self.length = self.length.value
        self.identification = self.identification.value
        self.flags = self._flags_offset.value >> 13
        self.offset = self._flags_offset.value & 8191
        self.ttl = self.ttl.value
        self.protocol = self.protocol.value
        self.checksum = self.checksum.value
        self.source = self.source.value
        self.destination = self.destination.value

        if self.ihl > 5:
            options_size = (self.ihl - 5) * 4
            self.data = self.options.value[options_size:]
            self.options = self.options.value[:options_size]
        else:
            self.data = self.options.value
            self.options = b''


class TLVWithSubType(GenericTLV):
    """Modify the :class:`GenericTLV` to a Organization Specific TLV structure.

    Beyond the standard TLV (type, length, value), we can also have a more
    specific structure, with the :attr:`value` field being splitted into a
    :attr:`sub_type` field and a new :attr:`sub_value` field.
    """

    def __init__(self, tlv_type=1, sub_type=7, sub_value=BinaryData()):
        """Create an instance and set its attributes.

        Args:
            tlv_type (int): Type used by this class. Defaults to 1.
            sub_type (int): Sub type value used by this class. Defaults to 7.
            sub_value (:class:`~pyof.foundation.basic_types.BinaryData`):
                Data stored by TLVWithSubType. Defaults to empty BinaryData.
        """
        super().__init__(tlv_type)
        self.sub_type = sub_type
        self.sub_value = sub_value

    @property
    def value(self):
        """Return sub type and sub value as binary data.

        Returns:
            :class:`~pyof.foundation.basic_types.BinaryData`:
                BinaryData calculated.

        """
        binary = UBInt8(self.sub_type).pack() + self.sub_value.pack()
        return BinaryData(binary)

    def unpack(self, buff, offset=0):
        """Unpack a binary message into this object's attributes.

        Unpack the binary value *buff* and update this object attributes based
        on the results.

        Args:
            buff (bytes): Binary data package to be unpacked.
            offset (int): Where to begin unpacking.

        Raises:
            Exception: If there is a struct unpacking error.

        """
        header = UBInt16()
        header.unpack(buff[offset:offset+2])
        self.tlv_type = header.value >> 9
        length = header.value & 511
        begin, end = offset + 2, offset + 2 + length
        sub_type = UBInt8()
        sub_type.unpack(buff[begin:begin+1])
        self.sub_type = sub_type.value
        self.sub_value = BinaryData(buff[begin+1:end])


class LLDP(GenericStruct):
    """LLDP class.

    Build a LLDP packet with TLVSubtype and Generic Subtypes.

    It contains a chassis_id TLV, a port_id TLV, a TTL (Time to live) and
    another TLV to represent the end of the LLDP Packet.
    """

    #: chassis_id (:class:`~TLVWithSubType`) with tlv_type = 1 and sub_type = 7
    chassis_id = TLVWithSubType(tlv_type=1, sub_type=7)
    #: port_id (:class:`TLVWithSubType`) with tlv = 2 and sub_type = 7
    port_id = TLVWithSubType(tlv_type=2, sub_type=7)
    #: TTL (:class:`GenericTLV`) time is given in seconds, between 0 and 65535,
    #: with tlv_type = 3
    ttl = GenericTLV(tlv_type=3, value=UBInt16(120))
    # We are not using list of tlvs for now
    # tlvs = ListOfTLVs()
    #: end (:class:`GenericTLV`) with tlv_type = 0
    end = GenericTLV(tlv_type=0)


1			"""Basic Network packet types.
2
3			Defines and Implements Basic Network packet types , such as Ethertnet and LLDP.
4			"""
5
6			from pyof.foundation.base import GenericStruct
7			from pyof.foundation.basic_types import (
8			BinaryData, HWAddress, IPAddress, UBInt8, UBInt16)
9			from pyof.foundation.constants import VLAN_TPID
10			from pyof.foundation.exceptions import PackException, UnpackException
11
12			__all__ = ('ARP', 'Ethernet', 'GenericTLV', 'IPv4', 'VLAN', 'TLVWithSubType',
13			'LLDP')
14
15
16			class ARP(GenericStruct):
17			"""ARP packet "struct".
18
19			Contains fields for an ARP packet's header and data.
20			Designed for Ethernet and IPv4 only: needs to have some attributes changed
21			for other HTYPE and PTYPE implementations.
22			Must be encapsulated inside an Ethernet frame.
23			"""
24
25			htype = UBInt16()
26			ptype = UBInt16()
27			hlen = UBInt8()
28			plen = UBInt8()
29			oper = UBInt16()
30			sha = HWAddress()
31			spa = IPAddress()
32			tha = HWAddress()
33			tpa = IPAddress()
34
35			def __init__(self, htype=1, ptype=0x800, hlen=6, plen=4, oper=1,
36			sha='00:00:00:00:00:00', spa='0.0.0.0',
37			tha="00:00:00:00:00:00", tpa='0.0.0.0'):
38			"""Create a ARP with the parameters below.
39
40			Args:
41			htype (int): Hardware protocol type. Defaults to 1 for Ethernet.
42			ptype (int): Network protocol type. Defaults to 0x800 for IPv4.
43			hlen (int): Length of the hardware address. Defaults to 6 for MAC
44			addresses.
45			plen (int): Length of the networking protocol address. Defaults to
46			4 for IPv4 addresses.
47			oper (int): Determines the operation for this ARP packet. Must be 1
48			for ARP request or 2 for ARP reply. Defaults to 1.
49			sha (str): Sender hardware address. Defaults to
50			'00:00:00:00:00:00'.
51			spa (str): Sender protocol address. Defaults to '0.0.0.0'.
52			tha (str): Target hardware address. Defaults to
53			'00:00:00:00:00:00'.
54			tpa (str): Target protocol address. Defaults to '0.0.0.0'.
55			"""
56			super().__init__()
57			self.htype = htype
58			self.ptype = ptype
59			self.hlen = hlen
60			self.plen = plen
61			self.oper = oper
62			self.sha = sha
63			self.spa = spa
64			self.tha = tha
65			self.tpa = tpa
66
67			def is_valid(self):
68			"""Assure the ARP contains Ethernet and IPv4 information."""
69			return self.htype == 1 and self.ptype == 0x800
70
71			def unpack(self, buff, offset=0):
72			"""Unpack a binary struct into this object's attributes.
73
74			Return the values instead of the lib's basic types.
75			Check if the protocols involved are Ethernet and IPv4. Other protocols
76			are currently not supported.
77
78			Args:
79			buff (bytes): Binary buffer.
80			offset (int): Where to begin unpacking.
81
82			Raises:
83			:exc:`~.exceptions.UnpackException`: If unpack fails.
84
85			"""
86			super().unpack(buff, offset)
87			if not self.is_valid():
88			raise UnpackException("Unsupported protocols in ARP packet")
89
90
91			class VLAN(GenericStruct):
92			"""802.1q VLAN header."""
93
94			#: tpid (:class:`UBInt16`): Tag Protocol Identifier
95			tpid = UBInt16(VLAN_TPID)
96			#: _tci (:class:`UBInt16`): Tag Control Information - has the
97			#: Priority Code Point, DEI/CFI bit and the VLAN ID
98			_tci = UBInt16()
99
100			def __init__(self, pcp=None, cfi=None, vid=None):
101			"""Create a VLAN with the parameters below.
102
103			If no arguments are set for a particular instance, it is interpreted as
104			abscence of VLAN information, and the pack() method will return an
105			empty binary string.
106
107			Args:
108			tpid (int): Tag Protocol Identifier. Defaults to 0x8100 for 802.1q.
109			pcp (int): 802.1p Priority Code Point. Defaults to 0 for Best
110			Effort Queue.
111			cfi (int): Canonical Format Indicator. Defaults to 0 for Ethernet.
112			vid (int): VLAN ID. If no VLAN is specified, value is 0.
113			"""
114			super().__init__()
115			self.tpid = VLAN_TPID
116			self.pcp = pcp
117			self.cfi = cfi
118			self.vid = vid
119
120			def pack(self, value=None):
121			"""Pack the struct in a binary representation.
122
123			Merge some fields to ensure correct packing.
124
125			If no arguments are set for a particular instance, it is interpreted as
126			abscence of VLAN information, and the pack() method will return an
127			empty binary string.
128
129			Returns:
130			bytes: Binary representation of this instance.
131
132			"""
133			if isinstance(value, type(self)):
134			return value.pack()
135
136			if self.pcp is None and self.cfi is None and self.vid is None:
137			return b''
138			self.pcp = self.pcp if self.pcp is not None else 0
139			self.cfi = self.cfi if self.cfi is not None else 0
140			self.vid = self.vid if self.vid is not None else 0
141			self._tci = self.pcp << 13 \| self.cfi << 12 \| self.vid
142			return super().pack()
143
144			def _validate(self):
145			"""Assure this is a 802.1q VLAN header instance."""
146			if self.tpid.value != VLAN_TPID:
147			raise UnpackException
148			return
149
150			def unpack(self, buff, offset=0):
151			"""Unpack a binary struct into this object's attributes.
152
153			Return the values instead of the lib's basic types.
154
155			After unpacking, the abscence of a `tpid` value causes the assignment
156			of None to the field values to indicate that there is no VLAN
157			information.
158
159			Args:
160			buff (bytes): Binary buffer.
161			offset (int): Where to begin unpacking.
162
163			Raises:
164			:exc:`~.exceptions.UnpackException`: If unpack fails.
165
166			"""
167			super().unpack(buff, offset)
168			if self.tpid.value:
169			self._validate()
170			self.tpid = self.tpid.value
171			self.pcp = self._tci.value >> 13
172			self.cfi = (self._tci.value >> 12) & 1
173			self.vid = self._tci.value & 4095
174			else:
175			self.tpid = VLAN_TPID
176			self.pcp = None
177			self.cfi = None
178			self.vid = None
179
180
181			class Ethernet(GenericStruct):
182			"""Ethernet "struct".
183
184			Objects of this class represents an ethernet packet. It contains the
185			'Ethernet header', composed by destination (MAC), source (MAC), type
186			(EtherType)[1] and the payload of the packet, as binary data.
187
188			This class does not consider the Ethernet 'Preamble' or the 'CRC'.
189
190			There is also a get_hash method, that hashes the binary representation of
191			the object so we can have a unique representation of the ethernet packet,
192			so we can keep a track of ethernet packets being flooded over the network.
193
194			[1] EtherTypes:
195			http://www.iana.org/assignments/ieee-802-numbers/ieee-802-numbers.xhtml#ieee-802-numbers-1
196			"""
197
198			destination = HWAddress()
199			source = HWAddress()
200			vlan = VLAN()
201			ether_type = UBInt16()
202			data = BinaryData()
203
204			def __init__(self, destination=None,
205			source=None, vlan=VLAN(), ether_type=None, data=b''):
206			"""Create an instance and set its attributes.
207
208			Args:
209			destination (:class:`~pyof.foundation.basic_types.HWAddress`):
210			The final destination MAC address.
211			source (:class:`~pyof.foundation.basic_types.HWAddress`):
212			The source Mac address of the packet.
213			ether_type (:class:`~pyof.foundation.basic_types.UBInt16`):
214			The EtherType of packet.
215			data (:class:`~pyof.foundation.basic_types.BinaryData`):
216			The content of the packet in binary format.
217			"""
218			super().__init__()
219			self.destination = destination
220			self.source = source
221			self.vlan = vlan
222			self.ether_type = ether_type
223			self.data = data
224
225			def get_hash(self):
226			"""Calculate a hash and returns it.
227
228			Returns:
229			int: Integer value that identifies this instance.
230
231			"""
232			return hash(self.pack())
233
234			def unpack(self, buff, offset=0):
235			"""Unpack a binary message into this object's attributes.
236
237			Unpack the binary value buff and update this object attributes based
238			on the results.
239
240			Ethernet headers may have VLAN tags. If no VLAN tag is found, a
241			'wildcard VLAN tag' is inserted to assure correct unpacking.
242
243			Args:
244			buff (bytes): Binary data package to be unpacked.
245			offset (int): Where to begin unpacking.
246
247			Raises:
248			UnpackException: If there is a struct unpacking error.
249
250			"""
251			# Checking if the EtherType bytes are actually equal to VLAN_TPID -
252			# indicating that the packet is tagged. If it is not, we insert the
253			# equivalent to 'NULL VLAN data' (\x00\x00\x00\x00) to enable the
254			# correct unpacking process.
255			if buff[12:16] != VLAN_TPID.to_bytes(2, 'big'):
256			buff = buff[0:12] + b'\x00\x00\x00\x00' + buff[12:]
257
258			super().unpack(buff, offset)
259
260
261			class GenericTLV(GenericStruct):
262			"""TLV structure of LLDP packets.
263
264			This is a Type, Length and Value (TLV) struct.
265
266			The LLDP/TLV definition states that the Type field have 7 bits, while
267			the length have 9 bits. The Value must be between 0-511 octets.
268
269			Internally, on the instances of this class, the Type is a integer
270			(0-127) and the Length is dynamically calculated based on the current
271			type and value.
272			"""
273
274			def __init__(self, tlv_type=127, value=BinaryData()):
275			"""Create an instance and set its attributes.
276
277			Args:
278			tlv_type (int): Type used by this class. Defaults to 127.
279			value (:class:`~pyof.foundation.basic_types.BinaryData`):
280			Value stored by GenericTLV.
281			"""
282			super().__init__()
283			self.tlv_type = tlv_type
284			self._value = value
285
286			@property
287			def value(self):
288			"""Return the value stored by GenericTLV.
289
290			Returns:
291			:class:`~pyof.foundation.basic_types.BinaryData`:
292			Value stored by GenericTLV.
293
294			"""
295			return self._value
296
297			@property
298			def length(self):
299			"""Return the length of value stored by GenericTLV.
300
301			Returns:
302			int: Value length in bytes.
303
304			"""
305			return len(self.value.pack())
306
307			@property
308			def header(self):
309			"""Header of the TLV Packet.
310
311			The header is composed by the Type (7 bits) and Length (9 bits),
312			summing up 16 bits. To achieve that, we need to do some bitshift
313			operations.
314
315			Returns:
316			:class:`~pyof.foundation.basic_types.UBInt16`:
317			Result after all operations.
318
319			"""
320			return UBInt16(((self.tlv_type & 127) << 9) \| (self.length & 511))
321
322			def pack(self, value=None):
323			"""Pack the TLV in a binary representation.
324
325			Returns:
326			bytes: Binary representation of the struct object.
327
328			Raises:
329			:exc:`~.exceptions.ValidationError`: If validation fails.
330
331			"""
332			if value is None:
333			output = self.header.pack()
334			output += self.value.pack()
335			return output
336
337			elif isinstance(value, type(self)):
338			return value.pack()
339			else:
340			msg = "{} is not an instance of {}".format(value,
341			type(self).__name__)
342			raise PackException(msg)
343
344			def unpack(self, buff, offset=0):
345			"""Unpack a binary message into this object's attributes.
346
347			Unpack the binary value buff and update this object attributes based
348			on the results.
349
350			Args:
351			buff (bytes): Binary data package to be unpacked.
352			offset (int): Where to begin unpacking.
353
354			Raises:
355			Exception: If there is a struct unpacking error.
356
357			"""
358			header = UBInt16()
359			header.unpack(buff[offset:offset+2])
360			self.tlv_type = header.value >> 9
361			length = header.value & 511
362			begin, end = offset + 2, offset + 2 + length
363			self._value = BinaryData(buff[begin:end])
364
365			def get_size(self, value=None):
366			"""Return struct size.
367
368			Returns:
369			int: Returns the struct size based on inner attributes.
370
371			"""
372			if isinstance(value, type(self)):
373			return value.get_size()
374
375			return 2 + self.length
376
377
378			class IPv4(GenericStruct):
379			"""IPv4 packet "struct".
380
381			Contains all fields of an IP version 4 packet header, plus the upper layer
382			content as binary data.
383			Some of the fields were merged together because of their size being
384			inferior to 8 bits. They are represented as a single class attribute, but
385			pack/unpack methods will take into account the values in individual
386			instance attributes.
387			"""
388
389			#: _version_ihl (:class:`UBInt8`): IP protocol version + Internet Header
390			#: Length (words)
391			_version_ihl = UBInt8()
392			#: _dscp_ecn (:class:`UBInt8`): Differentiated Services Code Point
393			#: (ToS - Type of Service) + Explicit Congestion Notification
394			_dscp_ecn = UBInt8()
395			#: length (:class:`UBInt16`): IP packet length (bytes)
396			length = UBInt16()
397			#: identification (:class:`UBInt16`): Packet ID - common to all fragments
398			identification = UBInt16()
399			#: _flags_offset (:class:`UBInt16`): Fragmentation flags + fragmentation
400			#: offset
401			_flags_offset = UBInt16()
402			#: ttl (:class:`UBInt8`): Packet time-to-live
403			ttl = UBInt8()
404			#: protocol (:class:`UBInt8`): Upper layer protocol number
405			protocol = UBInt8()
406			#: checksum (:class:`UBInt16`): Header checksum
407			checksum = UBInt16()
408			#: source (:class:`IPAddress`): Source IPv4 address
409			source = IPAddress()
410			#: destination (:class:`IPAddress`): Destination IPv4 address
411			destination = IPAddress()
412			#: options (:class:`BinaryData`): IP Options - up to 320 bits, always
413			#: padded to 32 bits
414			options = BinaryData()
415			#: data (:class:`BinaryData`): Packet data
416			data = BinaryData()
417
418			def __init__(self, version=4, ihl=5, dscp=0, ecn=0, length=0,
419			identification=0, flags=0, offset=0, ttl=255, protocol=0,
420			checksum=0, source="0.0.0.0", destination="0.0.0.0",
421			options=b'', data=b''):
422			"""Instanciate a IPv4 with the parameters below.
423
424			Args:
425			version (int): IP protocol version. Defaults to 4.
426			ihl (int): Internet Header Length. Default is 5.
427			dscp (int): Differentiated Service Code Point. Defaults to 0.
428			ecn (int): Explicit Congestion Notification. Defaults to 0.
429			length (int): IP packet length in bytes. Defaults to 0.
430			identification (int): Packet Id. Defaults to 0.
431			flags (int): IPv4 Flags. Defults 0.
432			offset (int): IPv4 offset. Defaults to 0.
433			ttl (int): Packet time-to-live. Defaults to 255
434			protocol (int): Upper layer protocol number. Defaults to 0.
435			checksum (int): Header checksum. Defaults to 0.
436			source (str): Source IPv4 address. Defaults to "0.0.0.0"
437			destination (str): Destination IPv4 address. Defaults to "0.0.0.0"
438			options (bytes): IP options. Defaults to empty bytes.
439			data (bytes): Packet data. Defaults to empty bytes.
440			"""
441			super().__init__()
442			self.version = version
443			self.ihl = ihl
444			self.dscp = dscp
445			self.ecn = ecn
446			self.length = length
447			self.identification = identification
448			self.flags = flags
449			self.offset = offset
450			self.ttl = ttl
451			self.protocol = protocol
452			self.checksum = checksum
453			self.source = source
454			self.destination = destination
455			self.options = options
456			self.data = data
457
458			def _update_checksum(self):
459			"""Update the packet checksum to enable integrity check."""
460			source_list = [int(octet) for octet in self.source.split(".")]
461			destination_list = [int(octet) for octet in
462			self.destination.split(".")]
463			source_upper = (source_list[0] << 8) + source_list[1]
464			source_lower = (source_list[2] << 8) + source_list[3]
465			destination_upper = (destination_list[0] << 8) + destination_list[1]
466			destination_lower = (destination_list[2] << 8) + destination_list[3]
467
468			block_sum = ((self._version_ihl << 8 \| self._dscp_ecn) + self.length +
469			self.identification + self._flags_offset +
470			(self.ttl << 8 \| self.protocol) + source_upper +
471			source_lower + destination_upper + destination_lower)
472
473			while block_sum > 65535:
474			carry = block_sum >> 16
475			block_sum = (block_sum & 65535) + carry
476
477			self.checksum = ~block_sum & 65535
478
479			def pack(self, value=None):
480			"""Pack the struct in a binary representation.
481
482			Merge some fields to ensure correct packing.
483
484			Returns:
485			bytes: Binary representation of this instance.
486
487			"""
488			# Set the correct IHL based on options size
489			if self.options:
490			self.ihl += int(len(self.options) / 4)
491
492			# Set the correct packet length based on header length and data
493			self.length = int(self.ihl * 4 + len(self.data))
494
495			self._version_ihl = self.version << 4 \| self.ihl
496			self._dscp_ecn = self.dscp << 2 \| self.ecn
497			self._flags_offset = self.flags << 13 \| self.offset
498
499			# Set the checksum field before packing
500			self._update_checksum()
501
502			return super().pack()
503
504			def unpack(self, buff, offset=0):
505			"""Unpack a binary struct into this object's attributes.
506
507			Return the values instead of the lib's basic types.
508
509			Args:
510			buff (bytes): Binary buffer.
511			offset (int): Where to begin unpacking.
512
513			Raises:
514			:exc:`~.exceptions.UnpackException`: If unpack fails.
515
516			"""
517			super().unpack(buff, offset)
518
519			self.version = self._version_ihl.value >> 4
520			self.ihl = self._version_ihl.value & 15
521			self.dscp = self._dscp_ecn.value >> 2
522			self.ecn = self._dscp_ecn.value & 3
523			self.length = self.length.value
524			self.identification = self.identification.value
525			self.flags = self._flags_offset.value >> 13
526			self.offset = self._flags_offset.value & 8191
527			self.ttl = self.ttl.value
528			self.protocol = self.protocol.value
529			self.checksum = self.checksum.value
530			self.source = self.source.value
531			self.destination = self.destination.value
532
533			if self.ihl > 5:
534			options_size = (self.ihl - 5) * 4
535			self.data = self.options.value[options_size:]
536			self.options = self.options.value[:options_size]
537			else:
538			self.data = self.options.value
539			self.options = b''
540
541
542			class TLVWithSubType(GenericTLV):
543			"""Modify the :class:`GenericTLV` to a Organization Specific TLV structure.
544
545			Beyond the standard TLV (type, length, value), we can also have a more
546			specific structure, with the :attr:`value` field being splitted into a
547			:attr:`sub_type` field and a new :attr:`sub_value` field.
548			"""
549
550			def __init__(self, tlv_type=1, sub_type=7, sub_value=BinaryData()):
551			"""Create an instance and set its attributes.
552
553			Args:
554			tlv_type (int): Type used by this class. Defaults to 1.
555			sub_type (int): Sub type value used by this class. Defaults to 7.
556			sub_value (:class:`~pyof.foundation.basic_types.BinaryData`):
557			Data stored by TLVWithSubType. Defaults to empty BinaryData.
558			"""
559			super().__init__(tlv_type)
560			self.sub_type = sub_type
561			self.sub_value = sub_value
562
563			@property
564			def value(self):
565			"""Return sub type and sub value as binary data.
566
567			Returns:
568			:class:`~pyof.foundation.basic_types.BinaryData`:
569			BinaryData calculated.
570
571			"""
572			binary = UBInt8(self.sub_type).pack() + self.sub_value.pack()
573			return BinaryData(binary)
574
575			def unpack(self, buff, offset=0):
576			"""Unpack a binary message into this object's attributes.
577
578			Unpack the binary value buff and update this object attributes based
579			on the results.
580
581			Args:
582			buff (bytes): Binary data package to be unpacked.
583			offset (int): Where to begin unpacking.
584
585			Raises:
586			Exception: If there is a struct unpacking error.
587
588			"""
589			header = UBInt16()
590			header.unpack(buff[offset:offset+2])
591			self.tlv_type = header.value >> 9
592			length = header.value & 511
593			begin, end = offset + 2, offset + 2 + length
594			sub_type = UBInt8()
595			sub_type.unpack(buff[begin:begin+1])
596			self.sub_type = sub_type.value
597			self.sub_value = BinaryData(buff[begin+1:end])
598
599
600			class LLDP(GenericStruct):
601			"""LLDP class.
602
603			Build a LLDP packet with TLVSubtype and Generic Subtypes.
604
605			It contains a chassis_id TLV, a port_id TLV, a TTL (Time to live) and
606			another TLV to represent the end of the LLDP Packet.
607			"""
608
609			#: chassis_id (:class:`~TLVWithSubType`) with tlv_type = 1 and sub_type = 7
610			chassis_id = TLVWithSubType(tlv_type=1, sub_type=7)
611			#: port_id (:class:`TLVWithSubType`) with tlv = 2 and sub_type = 7
612			port_id = TLVWithSubType(tlv_type=2, sub_type=7)
613			#: TTL (:class:`GenericTLV`) time is given in seconds, between 0 and 65535,
614			#: with tlv_type = 3
615			ttl = GenericTLV(tlv_type=3, value=UBInt16(120))
616			# We are not using list of tlvs for now
617			# tlvs = ListOfTLVs()
618			#: end (:class:`GenericTLV`) with tlv_type = 0
619			end = GenericTLV(tlv_type=0)
620

macartur / python-openflow

Pull Request — master (#4)

IPv4.pack() B

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