289 lines
11 KiB
Python
289 lines
11 KiB
Python
# Copyright (C) 2016 Bouygues Telecom.
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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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"""
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DHCPv6 packet parser/serializer
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[RFC 3315] DHCPv6 packet format:
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The following diagram illustrates the format of DHCP messages sent
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between clients and servers::
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0 1 2 3
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0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| msg_type | transaction_id |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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. options .
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. (variable) .
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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There are two relay agent messages, which share the following format::
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0 1 2 3
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0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| msg_type | hop_count | |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
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| link_address |
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| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
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| peer_address |
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| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
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. .
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. options (variable number and length) .... .
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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"""
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import random
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import struct
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from . import packet_base
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from os_ken.lib import addrconv
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from os_ken.lib import stringify
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# DHCPv6 message types
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DHCPV6_SOLICIT = 1
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DHCPV6_ADVERTISE = 2
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DHCPV6_REQUEST = 3
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DHCPV6_CONFIRM = 4
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DHCPV6_RENEW = 5
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DHCPV6_REBIND = 6
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DHCPV6_REPLY = 7
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DHCPV6_RELEASE = 8
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DHCPV6_DECLINE = 9
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DHCPV6_RECONFIGURE = 10
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DHCPV6_INFORMATION_REQUEST = 11
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DHCPV6_RELAY_FORW = 12
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DHCPV6_RELAY_REPL = 13
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# DHCPv6 option-codes
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DHCPV6_OPTION_CLIENTID = 1
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DHCPV6_OPTION_SERVERID = 2
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DHCPV6_OPTION_IA_NA = 3
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DHCPV6_OPTION_IA_TA = 4
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DHCPV6_OPTION_IAADDR = 5
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DHCPV6_OPTION_ORO = 6
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DHCPV6_OPTION_PREFERENCE = 7
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DHCPV6_OPTION_ELAPSED_TIME = 8
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DHCPV6_OPTION_RELAY_MSG = 9
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DHCPV6_OPTION_AUTH = 11
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DHCPV6_OPTION_UNICAST = 12
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DHCPV6_OPTION_STATUS_CODE = 13
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DHCPV6_OPTION_RAPID_COMMIT = 14
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DHCPV6_OPTION_USER_CLASS = 15
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DHCPV6_OPTION_VENDOR_CLASS = 16
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DHCPV6_OPTION_VENDOR_OPTS = 17
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DHCPV6_OPTION_INTERFACE_ID = 18
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DHCPV6_OPTION_RECONF_MSG = 19
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DHCPV6_OPTION_RECONF_ACCEPT = 20
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class dhcp6(packet_base.PacketBase):
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"""DHCPv6 (RFC 3315) header encoder/decoder class.
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The serialized packet would looks like the ones described
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in the following sections.
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* RFC 3315 DHCP packet format
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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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============== ====================
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Attribute Description
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============== ====================
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msg_type Identifies the DHCP message type
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transaction_id For unrelayed messages only: the transaction ID for\
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this message exchange.
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hop_count For relayed messages only: number of relay agents that\
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have relayed this message.
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link_address For relayed messages only: a global or site-local address\
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that will be used by the server to identify the link on\
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which the client is located.
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peer_address For relayed messages only: the address of the client or\
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relay agent from which the message to be relayed was\
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received.
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options Options carried in this message
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============== ====================
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"""
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_MIN_LEN = 8
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_DHCPV6_UNPACK_STR = '!I'
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_DHCPV6_RELAY_UNPACK_STR = '!H16s16s'
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_DHCPV6_UNPACK_STR_LEN = struct.calcsize(_DHCPV6_UNPACK_STR)
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_DHCPV6_RELAY_UNPACK_STR_LEN = struct.calcsize(_DHCPV6_RELAY_UNPACK_STR)
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_DHCPV6_PACK_STR = '!I'
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_DHCPV6_RELAY_PACK_STR = '!H16s16s'
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def __init__(self, msg_type, options, transaction_id=None, hop_count=0,
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link_address='::', peer_address='::'):
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super(dhcp6, self).__init__()
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self.msg_type = msg_type
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self.options = options
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if transaction_id is None:
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self.transaction_id = random.randint(0, 0xffffff)
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else:
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self.transaction_id = transaction_id
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self.hop_count = hop_count
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self.link_address = link_address
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self.peer_address = peer_address
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@classmethod
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def parser(cls, buf):
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(msg_type, ) = struct.unpack_from('!B', buf)
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buf = b'\x00' + buf[1:] # unpack xid as a 4-byte integer
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if msg_type == DHCPV6_RELAY_FORW or msg_type == DHCPV6_RELAY_REPL:
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(hop_count, link_address, peer_address) \
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= struct.unpack_from(cls._DHCPV6_RELAY_UNPACK_STR, buf)
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length = struct.calcsize(cls._DHCPV6_RELAY_UNPACK_STR)
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else:
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(transaction_id, ) \
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= struct.unpack_from(cls._DHCPV6_UNPACK_STR, buf)
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length = struct.calcsize(cls._DHCPV6_UNPACK_STR)
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if len(buf) > length:
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parse_opt = options.parser(buf[length:])
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length += parse_opt.options_len
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if msg_type == DHCPV6_RELAY_FORW or msg_type == DHCPV6_RELAY_REPL:
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return (cls(msg_type, parse_opt, 0, hop_count,
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addrconv.ipv6.bin_to_text(link_address),
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addrconv.ipv6.bin_to_text(peer_address)),
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None, buf[length:])
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else:
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return (cls(msg_type, parse_opt, transaction_id),
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None, buf[length:])
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else:
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return None, None, buf
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def serialize(self, payload=None, prev=None):
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seri_opt = self.options.serialize()
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if (self.msg_type == DHCPV6_RELAY_FORW or
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self.msg_type == DHCPV6_RELAY_REPL):
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pack_str = '%s%ds' % (self._DHCPV6_RELAY_PACK_STR,
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self.options.options_len)
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buf = struct.pack(pack_str, self.hop_count,
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addrconv.ipv6.text_to_bin(self.link_address),
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addrconv.ipv6.text_to_bin(self.peer_address),
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seri_opt)
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else:
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pack_str = '%s%ds' % (self._DHCPV6_PACK_STR,
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self.options.options_len)
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buf = struct.pack(pack_str, self.transaction_id, seri_opt)
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return struct.pack('!B', self.msg_type) + buf[1:]
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class options(stringify.StringifyMixin):
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"""DHCP (RFC 3315) options encoder/decoder class.
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This is used with os_ken.lib.packet.dhcp6.dhcp6.
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"""
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def __init__(self, option_list=None, options_len=0):
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super(options, self).__init__()
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if option_list is None:
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self.option_list = []
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else:
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self.option_list = option_list
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self.options_len = options_len
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@classmethod
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def parser(cls, buf):
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opt_parse_list = []
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offset = 0
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while len(buf) > offset:
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opt_buf = buf[offset:]
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opt = option.parser(opt_buf)
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opt_parse_list.append(opt)
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offset += opt.length + 4
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return cls(opt_parse_list, len(buf))
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def serialize(self):
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seri_opt = bytes()
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for opt in self.option_list:
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seri_opt += opt.serialize()
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if self.options_len == 0:
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self.options_len = len(seri_opt)
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return seri_opt
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class option(stringify.StringifyMixin):
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"""DHCP (RFC 3315) options encoder/decoder class.
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This is used with os_ken.lib.packet.dhcp6.dhcp6.options.
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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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The format of DHCP options is::
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0 1 2 3
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0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| option-code | option-len |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| option-data |
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| (option-len octets) |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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============== ====================
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Attribute Description
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============== ====================
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option-code An unsigned integer identifying the specific option\
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type carried in this option.
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option-len An unsigned integer giving the length of the\
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option-data field in this option in octets.
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option-data The data for the option; the format of this data\
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depends on the definition of the option.
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============== ====================
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"""
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_UNPACK_STR = '!H'
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_UNPACK_STR_LEN = struct.calcsize(_UNPACK_STR)
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_PACK_STR = '!HH%ds'
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def __init__(self, code, data, length=0):
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super(option, self).__init__()
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self.code = code
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self.data = data
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self.length = length
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@classmethod
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def parser(cls, buf):
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code = struct.unpack_from(cls._UNPACK_STR, buf)[0]
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buf = buf[cls._UNPACK_STR_LEN:]
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length = struct.unpack_from(cls._UNPACK_STR, buf)[0]
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buf = buf[cls._UNPACK_STR_LEN:]
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value_unpack_str = '%ds' % length
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data = struct.unpack_from(value_unpack_str, buf)[0]
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return cls(code, data, length)
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def serialize(self):
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if self.length == 0:
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self.length = len(self.data)
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options_pack_str = self._PACK_STR % self.length
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return struct.pack(options_pack_str, self.code, self.length, self.data)
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