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# Copyright (C) 2016 Nippon Telegraph and Telephone Corporation.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
# implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import struct
from os_ken.lib.pack_utils import msg_pack_into
from . import packet_base
from . import packet_utils
from . import ether_types
GRE_CHECKSUM_FLG = 1 << 7
GRE_KEY_FLG = 1 << 5
GRE_SEQUENCE_NUM_FLG = 1 << 4
class gre(packet_base.PacketBase):
"""GRE (RFC2784,RFC2890) header encoder/decoder class.
An instance has the following attributes at least.
Most of them are same to the on-wire counterparts but in host byte order.
__init__ takes the corresponding args in this order.
============== ========================================================
Attribute Description
============== ========================================================
version Version.
protocol Protocol Type field.
The Protocol Type is defined as "ETHER TYPES".
checksum Checksum field(optional).
When you set a value other than None,
this field will be automatically calculated.
key Key field(optional)
This field is intended to be used for identifying
an individual traffic flow within a tunnel.
vsid Virtual Subnet ID field(optional)
This field is a 24-bit value that is used
to identify the NVGRE-based Virtual Layer 2 Network.
flow_id FlowID field(optional)
This field is an 8-bit value that is used to provide
per-flow entropy for flows in the same VSID.
seq_number Sequence Number field(optional)
============== ========================================================
"""
_PACK_STR = "!BBH"
_CHECKSUM_PACK_STR = "!H2x"
_KEY_PACK_STR = "!I"
_SEQNUM_PACK_STR = "!I"
_MIN_LEN = struct.calcsize(_PACK_STR)
_CHECKSUM_LEN = struct.calcsize(_CHECKSUM_PACK_STR)
_KEY_LEN = struct.calcsize(_KEY_PACK_STR)
_SEQNUM_PACK_LEN = struct.calcsize(_SEQNUM_PACK_STR)
# GRE header
# 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
# +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
# |C| |K|S| Reserved0 | Ver | Protocol Type |
# +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
# | Checksum (optional) | Reserved1 (Optional) |
# +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
# | Key (optional) |
# +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
# | Sequence Number (Optional) |
# +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
def __init__(self, version=0, protocol=ether_types.ETH_TYPE_IP,
checksum=None, key=None, vsid=None, flow_id=None,
seq_number=None):
super(gre, self).__init__()
self.version = version
self.protocol = protocol
self.checksum = checksum
self.seq_number = seq_number
if key is not None:
self._key = key
self._vsid = self._key >> 8
self._flow_id = self._key & 0xff
elif (vsid is not None) and (flow_id is not None):
self._key = vsid << 8 | flow_id
self._vsid = vsid
self._flow_id = flow_id
else:
self._key = None
self._vsid = None
self._flow_id = None
@property
def key(self):
return self._key
@key.setter
def key(self, key):
if key is not None:
self._key = key
self._vsid = self._key >> 8
self._flow_id = self._key & 0xff
else:
self._key = None
self._vsid = None
self._flow_id = None
@property
def vsid(self):
return self._vsid
@vsid.setter
def vsid(self, vsid):
self._key = vsid << 8 | (self._key & 0xff)
self._vsid = vsid
@property
def flow_id(self):
return self._flow_id
@flow_id.setter
def flow_id(self, flow_id):
self._key = (self._key & 0xffffff00) | flow_id
self._flow_id = flow_id
@classmethod
def parser(cls, buf):
present, version, protocol = struct.unpack_from(cls._PACK_STR, buf)
gre_offset = gre._MIN_LEN
checksum = None
key = None
seq_number = None
if present & GRE_CHECKSUM_FLG:
checksum, = struct.unpack_from(cls._CHECKSUM_PACK_STR,
buf, gre_offset)
gre_offset += cls._CHECKSUM_LEN
if present & GRE_KEY_FLG:
key, = struct.unpack_from(cls._KEY_PACK_STR, buf, gre_offset)
gre_offset += cls._KEY_LEN
if present & GRE_SEQUENCE_NUM_FLG:
seq_number, = struct.unpack_from(cls._SEQNUM_PACK_STR,
buf, gre_offset)
gre_offset += cls._SEQNUM_PACK_LEN
msg = cls(version=version, protocol=protocol, checksum=checksum,
key=key, seq_number=seq_number)
from . import ethernet
gre._TYPES = ethernet.ethernet._TYPES
gre.register_packet_type(ethernet.ethernet,
ether_types.ETH_TYPE_TEB)
return msg, gre.get_packet_type(protocol), buf[gre_offset:]
def serialize(self, payload=None, prev=None):
present = 0
hdr = bytearray()
optional = bytearray()
if self.checksum is not None:
present |= GRE_CHECKSUM_FLG
# For purposes of computing the checksum,
# the value of the checksum field is zero.
# Also, because Reserved1 is always 0x00 of 2 bytes,
# Set in conjunction with checksum.
optional += b'\x00' * self._CHECKSUM_LEN
if self._key is not None:
present |= GRE_KEY_FLG
optional += struct.pack(self._KEY_PACK_STR, self._key)
if self.seq_number is not None:
present |= GRE_SEQUENCE_NUM_FLG
optional += struct.pack(self._SEQNUM_PACK_STR, self.seq_number)
msg_pack_into(self._PACK_STR, hdr, 0, present, self.version,
self.protocol)
hdr += optional
if self.checksum:
self.checksum = packet_utils.checksum(hdr)
struct.pack_into(self._CHECKSUM_PACK_STR, hdr, self._MIN_LEN,
self.checksum)
return hdr
def nvgre(version=0, vsid=0, flow_id=0):
"""
Generate instance of GRE class with information for NVGRE (RFC7637).
:param version: Version.
:param vsid: Virtual Subnet ID.
:param flow_id: FlowID.
:return: Instance of GRE class with information for NVGRE.
"""
# NVGRE header
# 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
# +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
# |0| |1|0| Reserved0 | Ver | Protocol Type 0x6558 |
# +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
# | Virtual Subnet ID (VSID) | FlowID |
# +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
return gre(version=version, protocol=ether_types.ETH_TYPE_TEB,
vsid=vsid, flow_id=flow_id)
|
