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