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# Copyright (C) 2012 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 . import packet_base
from . import vlan
from . import mpls
from . import ether_types as ether
from os_ken.lib import addrconv
from os_ken.lib.pack_utils import msg_pack_into
class ethernet(packet_base.PacketBase):
"""Ethernet header encoder/decoder class.
An instance has the following attributes at least.
MAC addresses are represented as a string like '08:60:6e:7f:74:e7'.
__init__ takes the corresponding args in this order.
============== ==================== =====================
Attribute Description Example
============== ==================== =====================
dst destination address 'ff:ff:ff:ff:ff:ff'
src source address '08:60:6e:7f:74:e7'
ethertype ether type 0x0800
============== ==================== =====================
"""
_PACK_STR = '!6s6sH'
_MIN_LEN = struct.calcsize(_PACK_STR)
_MIN_PAYLOAD_LEN = 46
_TYPE = {
'ascii': [
'src', 'dst'
]
}
def __init__(self, dst='ff:ff:ff:ff:ff:ff', src='00:00:00:00:00:00',
ethertype=ether.ETH_TYPE_IP):
super(ethernet, self).__init__()
self.dst = dst
self.src = src
self.ethertype = ethertype
@classmethod
def parser(cls, buf):
dst, src, ethertype = struct.unpack_from(cls._PACK_STR, buf)
return (cls(addrconv.mac.bin_to_text(dst),
addrconv.mac.bin_to_text(src), ethertype),
ethernet.get_packet_type(ethertype),
buf[ethernet._MIN_LEN:])
def serialize(self, payload, prev):
# Append padding if the payload is less than 46 bytes long
pad_len = self._MIN_PAYLOAD_LEN - len(payload)
if pad_len > 0:
payload.extend(b'\x00' * pad_len)
return struct.pack(ethernet._PACK_STR,
addrconv.mac.text_to_bin(self.dst),
addrconv.mac.text_to_bin(self.src),
self.ethertype)
@classmethod
def get_packet_type(cls, type_):
"""Override method for the ethernet IEEE802.3 Length/Type
field (self.ethertype).
If the value of Length/Type field is less than or equal to
1500 decimal(05DC hexadecimal), it means Length interpretation
and be passed to the LLC sublayer."""
if type_ <= ether.ETH_TYPE_IEEE802_3:
type_ = ether.ETH_TYPE_IEEE802_3
return cls._TYPES.get(type_)
# copy vlan _TYPES
ethernet._TYPES = vlan.vlan._TYPES
ethernet.register_packet_type(vlan.vlan, ether.ETH_TYPE_8021Q)
ethernet.register_packet_type(vlan.svlan, ether.ETH_TYPE_8021AD)
ethernet.register_packet_type(mpls.mpls, ether.ETH_TYPE_MPLS)
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