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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 abc
from os_ken.lib import stringify
class PacketBase(stringify.StringifyMixin, metaclass=abc.ABCMeta):
"""A base class for a protocol (ethernet, ipv4, ...) header."""
_TYPES = {}
@classmethod
def get_packet_type(cls, type_):
"""Per-protocol dict-like get method.
Provided for convenience of protocol implementers.
Internal use only."""
return cls._TYPES.get(type_)
@classmethod
def register_packet_type(cls, cls_, type_):
"""Per-protocol dict-like set method.
Provided for convenience of protocol implementers.
Internal use only."""
cls._TYPES[type_] = cls_
def __init__(self):
super(PacketBase, self).__init__()
def __len__(self):
return self._MIN_LEN
@property
def protocol_name(self):
return self.__class__.__name__
@classmethod
@abc.abstractmethod
def parser(cls, buf):
"""Decode a protocol header.
This method is used only when decoding a packet.
Decode a protocol header at offset 0 in bytearray *buf*.
Returns the following three objects.
* An object to describe the decoded header.
* A packet_base.PacketBase subclass appropriate for the rest of
the packet. None when the rest of the packet should be considered
as raw payload.
* The rest of packet.
"""
pass
def serialize(self, payload, prev):
"""Encode a protocol header.
This method is used only when encoding a packet.
Encode a protocol header.
Returns a bytearray which contains the header.
*payload* is the rest of the packet which will immediately follow
this header.
*prev* is a packet_base.PacketBase subclass for the outer protocol
header. *prev* is None if the current header is the outer-most.
For example, *prev* is ipv4 or ipv6 for tcp.serialize.
"""
pass
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