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