a6dce73e33
get_protocols returns the list of protocols. This is useful for a packet including the same protocol multiple times (e.g. tunneling such GRE). However, it's a rare use case. Instead of 'get_protocols(hoge)[0]', let's do 'get_protocol(hoge)' simply. Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
157 lines
4.7 KiB
Python
157 lines
4.7 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 inspect
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import struct
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from . import packet_base
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from . import ethernet
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class Packet(object):
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"""A packet decoder/encoder class.
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An instance is used to either decode or encode a single packet.
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*data* is a bytearray to describe a raw datagram to decode.
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When decoding, a Packet object is iteratable.
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Iterated values are protocol (ethernet, ipv4, ...) headers and the payload.
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Protocol headers are instances of subclass of packet_base.PacketBase.
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The payload is a bytearray. They are iterated in on-wire order.
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*data* should be omitted when encoding a packet.
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"""
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def __init__(self, data=None, protocols=None, parse_cls=ethernet.ethernet):
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super(Packet, self).__init__()
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self.data = data
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if protocols is None:
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self.protocols = []
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else:
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self.protocols = protocols
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self.protocol_idx = 0
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if self.data:
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self._parser(parse_cls)
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def _parser(self, cls):
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rest_data = self.data
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while cls:
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try:
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proto, cls, rest_data = cls.parser(rest_data)
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except struct.error:
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break
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if proto:
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self.protocols.append(proto)
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if rest_data:
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self.protocols.append(rest_data)
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def serialize(self):
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"""Encode a packet and store the resulted bytearray in self.data.
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This method is legal only when encoding a packet.
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"""
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self.data = bytearray()
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r = self.protocols[::-1]
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for i, p in enumerate(r):
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if isinstance(p, packet_base.PacketBase):
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if i == len(r) - 1:
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prev = None
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else:
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prev = r[i + 1]
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data = p.serialize(self.data, prev)
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else:
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data = str(p)
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self.data = data + self.data
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def add_protocol(self, proto):
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"""Register a protocol *proto* for this packet.
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This method is legal only when encoding a packet.
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When encoding a packet, register a protocol (ethernet, ipv4, ...)
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header to add to this packet.
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Protocol headers should be registered in on-wire order before calling
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self.serialize.
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"""
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self.protocols.append(proto)
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def get_protocols(self, protocol):
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"""Returns a list of protocols that matches to the specified protocol.
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"""
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if isinstance(protocol, packet_base.PacketBase):
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protocol = protocol.__class__
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assert issubclass(protocol, packet_base.PacketBase)
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return [p for p in self.protocols if isinstance(p, protocol)]
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def get_protocol(self, protocol):
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"""Returns the firstly found protocol that matches to the
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specified protocol.
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"""
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result = self.get_protocols(protocol)
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if len(result) > 0:
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return result[0]
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return None
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def next(self):
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try:
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p = self.protocols[self.protocol_idx]
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except:
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self.protocol_idx = 0
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raise StopIteration
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self.protocol_idx += 1
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return p
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def __div__(self, trailer):
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self.add_protocol(trailer)
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return self
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def __iter__(self):
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return self
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def __getitem__(self, idx):
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return self.protocols[idx]
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def __setitem__(self, idx, item):
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self.protocols[idx] = item
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def __delitem__(self, idx):
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del self.protocols[idx]
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def __len__(self):
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return len(self.protocols)
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def __contains__(self, protocol):
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if (inspect.isclass(protocol) and
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issubclass(protocol, packet_base.PacketBase)):
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return protocol in [p.__class__ for p in self.protocols]
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return protocol in self.protocols
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def __str__(self):
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return ', '.join(repr(protocol) for protocol in self.protocols)
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__repr__ = __str__ # note: str(list) uses __repr__ for elements
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# XXX: Hack for preventing recursive import
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def _PacketBase__div__(self, trailer):
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pkt = Packet()
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pkt.add_protocol(self)
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pkt.add_protocol(trailer)
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return pkt
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packet_base.PacketBase.__div__ = _PacketBase__div__
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