326 lines
9.5 KiB
Python
326 lines
9.5 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 abc
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import struct
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import six
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from . import packet_base
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from . import packet_utils
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from os_ken.lib import stringify
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ICMP_ECHO_REPLY = 0
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ICMP_DEST_UNREACH = 3
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ICMP_SRC_QUENCH = 4
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ICMP_REDIRECT = 5
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ICMP_ECHO_REQUEST = 8
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ICMP_TIME_EXCEEDED = 11
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ICMP_ECHO_REPLY_CODE = 0
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ICMP_HOST_UNREACH_CODE = 1
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ICMP_PORT_UNREACH_CODE = 3
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ICMP_TTL_EXPIRED_CODE = 0
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class icmp(packet_base.PacketBase):
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"""ICMP (RFC 792) header encoder/decoder class.
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An instance has the following attributes at least.
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Most of them are same to the on-wire counterparts but in host byte order.
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__init__ takes the corresponding args in this order.
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.. tabularcolumns:: |l|L|
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============== ====================
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Attribute Description
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============== ====================
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type Type
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code Code
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csum CheckSum \
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(0 means automatically-calculate when encoding)
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data Payload. \
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Either a bytearray, or \
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os_ken.lib.packet.icmp.echo or \
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os_ken.lib.packet.icmp.dest_unreach or \
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os_ken.lib.packet.icmp.TimeExceeded object \
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NOTE for icmp.echo: \
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This includes "unused" 16 bits and the following \
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"Internet Header + 64 bits of Original Data Datagram" of \
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the ICMP header. \
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NOTE for icmp.dest_unreach and icmp.TimeExceeded: \
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This includes "unused" 8 or 24 bits and the following \
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"Internet Header + leading octets of original datagram" \
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of the original packet.
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============== ====================
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"""
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_PACK_STR = '!BBH'
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_MIN_LEN = struct.calcsize(_PACK_STR)
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_ICMP_TYPES = {}
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@staticmethod
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def register_icmp_type(*args):
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def _register_icmp_type(cls):
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for type_ in args:
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icmp._ICMP_TYPES[type_] = cls
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return cls
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return _register_icmp_type
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def __init__(self, type_=ICMP_ECHO_REQUEST, code=0, csum=0, data=b''):
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super(icmp, self).__init__()
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self.type = type_
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self.code = code
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self.csum = csum
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self.data = data
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@classmethod
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def parser(cls, buf):
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(type_, code, csum) = struct.unpack_from(cls._PACK_STR, buf)
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msg = cls(type_, code, csum)
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offset = cls._MIN_LEN
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if len(buf) > offset:
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cls_ = cls._ICMP_TYPES.get(type_, None)
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if cls_:
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msg.data = cls_.parser(buf, offset)
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else:
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msg.data = buf[offset:]
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return msg, None, None
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def serialize(self, payload, prev):
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hdr = bytearray(struct.pack(icmp._PACK_STR, self.type,
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self.code, self.csum))
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if self.data:
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if self.type in icmp._ICMP_TYPES:
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assert isinstance(self.data, _ICMPv4Payload)
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hdr += self.data.serialize()
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else:
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hdr += self.data
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else:
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self.data = echo()
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hdr += self.data.serialize()
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if self.csum == 0:
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self.csum = packet_utils.checksum(hdr)
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struct.pack_into('!H', hdr, 2, self.csum)
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return hdr
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def __len__(self):
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return self._MIN_LEN + len(self.data)
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@six.add_metaclass(abc.ABCMeta)
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class _ICMPv4Payload(stringify.StringifyMixin):
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"""
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Base class for the payload of ICMPv4 packet.
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"""
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@icmp.register_icmp_type(ICMP_ECHO_REPLY, ICMP_ECHO_REQUEST)
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class echo(_ICMPv4Payload):
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"""ICMP sub encoder/decoder class for Echo and Echo Reply messages.
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This is used with os_ken.lib.packet.icmp.icmp for
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ICMP Echo and Echo Reply messages.
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An instance has the following attributes at least.
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Most of them are same to the on-wire counterparts but in host byte order.
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__init__ takes the corresponding args in this order.
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.. tabularcolumns:: |l|L|
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============== ====================
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Attribute Description
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============== ====================
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id Identifier
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seq Sequence Number
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data Internet Header + 64 bits of Original Data Datagram
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============== ====================
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"""
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_PACK_STR = '!HH'
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_MIN_LEN = struct.calcsize(_PACK_STR)
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def __init__(self, id_=0, seq=0, data=None):
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super(echo, self).__init__()
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self.id = id_
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self.seq = seq
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self.data = data
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@classmethod
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def parser(cls, buf, offset):
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(id_, seq) = struct.unpack_from(cls._PACK_STR, buf, offset)
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msg = cls(id_, seq)
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offset += cls._MIN_LEN
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if len(buf) > offset:
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msg.data = buf[offset:]
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return msg
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def serialize(self):
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hdr = bytearray(struct.pack(echo._PACK_STR, self.id,
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self.seq))
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if self.data is not None:
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hdr += self.data
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return hdr
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def __len__(self):
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length = self._MIN_LEN
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if self.data is not None:
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length += len(self.data)
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return length
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@icmp.register_icmp_type(ICMP_DEST_UNREACH)
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class dest_unreach(_ICMPv4Payload):
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"""ICMP sub encoder/decoder class for Destination Unreachable Message.
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This is used with os_ken.lib.packet.icmp.icmp for
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ICMP Destination Unreachable Message.
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An instance has the following attributes at least.
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Most of them are same to the on-wire counterparts but in host byte order.
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__init__ takes the corresponding args in this order.
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[RFC1191] reserves bits for the "Next-Hop MTU" field.
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[RFC4884] introduced 8-bit data length attribute.
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.. tabularcolumns:: |l|p{35em}|
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============== =====================================================
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Attribute Description
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============== =====================================================
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data_len data length
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mtu Next-Hop MTU
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NOTE: This field is required when icmp code is 4
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code 4 = fragmentation needed and DF set
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data Internet Header + leading octets of original datagram
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============== =====================================================
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"""
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_PACK_STR = '!xBH'
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_MIN_LEN = struct.calcsize(_PACK_STR)
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def __init__(self, data_len=0, mtu=0, data=None):
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super(dest_unreach, self).__init__()
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if ((data_len >= 0) and (data_len <= 255)):
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self.data_len = data_len
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else:
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raise ValueError('Specified data length (%d) is invalid.' % data_len)
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self.mtu = mtu
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self.data = data
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@classmethod
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def parser(cls, buf, offset):
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(data_len, mtu) = struct.unpack_from(cls._PACK_STR,
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buf, offset)
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msg = cls(data_len, mtu)
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offset += cls._MIN_LEN
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if len(buf) > offset:
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msg.data = buf[offset:]
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return msg
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def serialize(self):
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hdr = bytearray(struct.pack(dest_unreach._PACK_STR,
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self.data_len, self.mtu))
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if self.data is not None:
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hdr += self.data
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return hdr
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def __len__(self):
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length = self._MIN_LEN
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if self.data is not None:
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length += len(self.data)
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return length
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@icmp.register_icmp_type(ICMP_TIME_EXCEEDED)
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class TimeExceeded(_ICMPv4Payload):
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"""ICMP sub encoder/decoder class for Time Exceeded Message.
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This is used with os_ken.lib.packet.icmp.icmp for
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ICMP Time Exceeded Message.
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An instance has the following attributes at least.
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Most of them are same to the on-wire counterparts but in host byte order.
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__init__ takes the corresponding args in this order.
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[RFC4884] introduced 8-bit data length attribute.
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.. tabularcolumns:: |l|L|
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============== ====================
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Attribute Description
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============== ====================
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data_len data length
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data Internet Header + leading octets of original datagram
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============== ====================
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"""
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_PACK_STR = '!xBxx'
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_MIN_LEN = struct.calcsize(_PACK_STR)
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def __init__(self, data_len=0, data=None):
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if (data_len >= 0) and (data_len <= 255):
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self.data_len = data_len
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else:
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raise ValueError('Specified data length (%d) is invalid.' % data_len)
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self.data = data
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@classmethod
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def parser(cls, buf, offset):
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(data_len, ) = struct.unpack_from(cls._PACK_STR, buf, offset)
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msg = cls(data_len)
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offset += cls._MIN_LEN
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if len(buf) > offset:
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msg.data = buf[offset:]
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return msg
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def serialize(self):
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hdr = bytearray(struct.pack(TimeExceeded._PACK_STR, self.data_len))
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if self.data is not None:
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hdr += self.data
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return hdr
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def __len__(self):
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length = self._MIN_LEN
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if self.data is not None:
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length += len(self.data)
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return length
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icmp.set_classes(icmp._ICMP_TYPES)
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