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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 inspect
import struct
import base64
from . import packet_base
from . import ethernet
from os_ken import utils
from os_ken.lib.stringify import StringifyMixin
# Packet class dictionary
mod = inspect.getmembers(utils.import_module("os_ken.lib.packet"),
lambda cls: (inspect.ismodule(cls)))
cls_list = []
for _, m in mod:
cl = inspect.getmembers(m,
lambda cls: (
inspect.isclass(cls) and
issubclass(cls, packet_base.PacketBase)))
cls_list.extend(list(cl))
PKT_CLS_DICT = dict(cls_list)
class Packet(StringifyMixin):
"""A packet decoder/encoder class.
An instance is used to either decode or encode a single packet.
*data* is a bytearray to describe a raw datagram to decode.
When decoding, a Packet object is iteratable.
Iterated values are protocol (ethernet, ipv4, ...) headers and the payload.
Protocol headers are instances of subclass of packet_base.PacketBase.
The payload is a bytearray. They are iterated in on-wire order.
*data* should be omitted when encoding a packet.
"""
# Ignore data field when outputting json representation.
_base_attributes = ['data']
def __init__(self, data=None, protocols=None, parse_cls=ethernet.ethernet):
super(Packet, self).__init__()
self.data = data
if protocols is None:
self.protocols = []
else:
self.protocols = protocols
if self.data:
self._parser(parse_cls)
def _parser(self, cls):
rest_data = self.data
while cls:
# Ignores an empty buffer
if not bytes(rest_data).strip(b'\x00'):
break
try:
proto, cls, rest_data = cls.parser(rest_data)
except struct.error:
break
if proto:
self.protocols.append(proto)
# If rest_data is all padding, we ignore rest_data
if rest_data and bytes(rest_data).strip(b'\x00'):
self.protocols.append(rest_data)
def serialize(self):
"""Encode a packet and store the resulted bytearray in self.data.
This method is legal only when encoding a packet.
"""
self.data = bytearray()
r = self.protocols[::-1]
for i, p in enumerate(r):
if isinstance(p, packet_base.PacketBase):
if i == len(r) - 1:
prev = None
else:
prev = r[i + 1]
data = p.serialize(self.data, prev)
else:
data = bytes(p)
self.data = bytearray(data + self.data)
@classmethod
def from_jsondict(cls, dict_, decode_string=base64.b64decode,
**additional_args):
protocols = []
for proto in dict_['protocols']:
for key, value in proto.items():
if key in PKT_CLS_DICT:
pkt_cls = PKT_CLS_DICT[key]
protocols.append(pkt_cls.from_jsondict(value))
else:
raise ValueError('unknown protocol name %s' % key)
return cls(protocols=protocols)
def add_protocol(self, proto):
"""Register a protocol *proto* for this packet.
This method is legal only when encoding a packet.
When encoding a packet, register a protocol (ethernet, ipv4, ...)
header to add to this packet.
Protocol headers should be registered in on-wire order before calling
self.serialize.
"""
self.protocols.append(proto)
def get_protocols(self, protocol):
"""Returns a list of protocols that matches to the specified protocol.
"""
if isinstance(protocol, packet_base.PacketBase):
protocol = protocol.__class__
assert issubclass(protocol, packet_base.PacketBase)
return [p for p in self.protocols if isinstance(p, protocol)]
def get_protocol(self, protocol):
"""Returns the firstly found protocol that matches to the
specified protocol.
"""
result = self.get_protocols(protocol)
if len(result) > 0:
return result[0]
return None
def __div__(self, trailer):
self.add_protocol(trailer)
return self
def __truediv__(self, trailer):
return self.__div__(trailer)
def __iter__(self):
return iter(self.protocols)
def __getitem__(self, idx):
return self.protocols[idx]
def __setitem__(self, idx, item):
self.protocols[idx] = item
def __delitem__(self, idx):
del self.protocols[idx]
def __len__(self):
return len(self.protocols)
def __contains__(self, protocol):
if (inspect.isclass(protocol) and
issubclass(protocol, packet_base.PacketBase)):
return protocol in [p.__class__ for p in self.protocols]
return protocol in self.protocols
def __str__(self):
return ', '.join(repr(protocol) for protocol in self.protocols)
__repr__ = __str__ # note: str(list) uses __repr__ for elements
# XXX: Hack for preventing recursive import
def _PacketBase__div__(self, trailer):
pkt = Packet()
pkt.add_protocol(self)
pkt.add_protocol(trailer)
return pkt
packet_base.PacketBase.__div__ = _PacketBase__div__
packet_base.PacketBase.__truediv__ = _PacketBase__div__
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