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lib/packet: DHCP packet parser/serializer
Add DHCP encoder/decoder class. Signed-off-by: TAKESHITA Noboru <takeshita.noboru@yes.nttcom.ne.jp> Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
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竹下昇
FUJITA Tomonori
parent
77effb29a6
commit
6f2716b7ff
296
ryu/lib/packet/dhcp.py
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296
ryu/lib/packet/dhcp.py
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# Copyright (C) 2013 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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"""
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DHCP packet parser/serializer
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RFC 2131
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DHCP packet 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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| op (1) | htype (1) | hlen (1) | hops (1) |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| xid (4) |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| secs (2) | flags (2) |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| ciaddr (4) |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| yiaddr (4) |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| siaddr (4) |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| giaddr (4) |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| chaddr (16) |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| sname (64) |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| file (128) |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| options (variable) |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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"""
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import binascii
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import random
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import socket
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import struct
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from . import packet_base
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DHCP_BOOT_REQUEST = 1
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DHCP_BOOT_REPLY = 2
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# DHCP message type code
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DHCP_DISCOVER = 1
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DHCP_OFFER = 2
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DHCP_REQUEST = 3
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DHCP_ACK = 5
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# DHCP options tag code
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DHCP_PAD_OPT = 0
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DHCP_SUBNET_MASK_OPT = 1
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DHCP_GATEWAY_ADDR_OPT = 3
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DHCP_DNS_SERVER_ADDR_OPT = 6
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DHCP_HOST_NAME_OPT = 12
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DHCP_REQUESTED_IP_ADDR_OPT = 50
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DHCP_IP_ADDR_LEASE_TIME_OPT = 51
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DHCP_MESSAGE_TYPE_OPT = 53
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DHCP_SERVER_IDENTIFIER_OPT = 54
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DHCP_PARAMETER_REQUEST_LIST_OPT = 55
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DHCP_RENEWAL_TIME_OPT = 58
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DHCP_REBINDING_TIME_OPT = 59
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DHCP_END_OPT = 255
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class dhcp(packet_base.PacketBase):
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"""DHCP (RFC 2131) 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 2131 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 correspondig args in this order.
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============== ====================
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Attribute Description
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============== ====================
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op Message op code / message type.\
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1 = BOOTREQUEST, 2 = BOOTREPLY
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htype Hardware address type (e.g. '1' = 10mb ethernet).
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hlen Hardware address length (e.g. '6' = 10mb ethernet).
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hops Client sets to zero, optionally used by relay agent\
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when booting via a relay agent.
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xid Transaction ID, a random number chosen by the client,\
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used by the client and serverto associate messages\
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and responses between a client and a server.
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secs Filled in by client, seconds elapsed since client\
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began address acquisition or renewal process.
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flags Flags.
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ciaddr Client IP address; only filled in if client is in\
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BOUND, RENEW or REBINDING state and can respond\
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to ARP requests.
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yiaddr 'your' (client) IP address.
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siaddr IP address of next server to use in bootstrap;\
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returned in DHCPOFFER, DHCPACK by server.
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giaddr Relay agent IP address, used in booting via a\
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relay agent.
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chaddr Client hardware address.
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sname Optional server host name, null terminated string.
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boot_file Boot file name, null terminated string; "generic"\
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name or null in DHCPDISCOVER, fully qualified\
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directory-path name in DHCPOFFER.
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options Optional parameters field\
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('DHCP message type' option must be included in\
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every DHCP message).
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============== ====================
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"""
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_HLEN_UNPACK_STR = '!BBB'
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_HLEN_UNPACK_LEN = struct.calcsize(_HLEN_UNPACK_STR)
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_DHCP_UNPACK_STR = '!BIHHIIII%ds%ds64s128s'
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_DHCP_PACK_STR = '!BBBBIHHIIII16s64s128s'
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_DHCP_CHADDR_LEN = 16
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_HARDWARE_TYPE_ETHERNET = 1
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def __init__(self, op, chaddr, options, htype=_HARDWARE_TYPE_ETHERNET,
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hlen=0, hops=0, xid=None, secs=0, flags=0, ciaddr=0, yiaddr=0,
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siaddr=0, giaddr=0, sname='', boot_file=''):
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super(dhcp, self).__init__()
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self.op = op
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self.htype = htype
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if hlen == 0:
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self.hlen = len(chaddr)
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else:
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self.hlen = hlen
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self.hops = hops
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if xid is None:
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self.xid = random.randint(0, 0xffffffff)
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else:
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self.xid = xid
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self.secs = secs
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self.flags = flags
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self.ciaddr = ciaddr
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self.yiaddr = yiaddr
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self.siaddr = siaddr
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self.giaddr = giaddr
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self.chaddr = chaddr
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self.sname = sname
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self.boot_file = boot_file
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self.options = options
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@classmethod
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def parser(cls, buf):
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(op, htype, hlen) = struct.unpack_from(cls._HLEN_UNPACK_STR, buf)
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buf = buf[cls._HLEN_UNPACK_LEN:]
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unpack_str = cls._DHCP_UNPACK_STR % (hlen,
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(cls._DHCP_CHADDR_LEN - hlen))
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min_len = struct.calcsize(unpack_str)
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(hops, xid, secs, flags, ciaddr, yiaddr, siaddr, giaddr, chaddr,
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dummy, sname, boot_file
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) = struct.unpack_from(unpack_str, buf)
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if len(buf) > min_len:
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parse_opt = options.parser(buf[min_len:])
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return cls(op, chaddr, parse_opt, htype, hlen, hops, xid, secs, flags,
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ciaddr, yiaddr, siaddr, giaddr, sname, boot_file)
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def serialize(self, payload, prev):
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seri_opt = self.options.serialize()
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pack_str = '%s%ds' % (self._DHCP_PACK_STR,
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self.options.options_len)
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return struct.pack(pack_str, self.op, self.htype, self.hlen,
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self.hops, self.xid, self.secs, self.flags,
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self.ciaddr, self.yiaddr, self.siaddr, self.giaddr,
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self.chaddr, self.sname, self.boot_file, seri_opt)
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class options(object):
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"""DHCP (RFC 2132) options encoder/decoder class.
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This is used with ryu.lib.packet.dhcp.dhcp.
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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 correspondig args in this order.
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============== ====================
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Attribute Description
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============== ====================
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option_list 'end option' and 'pad option' are added automatically\
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after the option class is stored in array.
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options_len Option's byte length.\
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('magic cookie', 'end option' and 'pad option'\
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length including.)
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magic_cookie The first four octets contain the decimal values\
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99, 130, 83 and 99.
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============== ====================
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"""
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_MAGIC_COOKIE_UNPACK_STR = '!I'
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# same magic cookie as is defined in RFC 1497
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_MAGIC_COOKIE = socket.inet_aton("99.130.83.99")
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_OPT_TAG_LEN_BYTE = 2
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def __init__(self, option_list=None, options_len=0,
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magic_cookie=_MAGIC_COOKIE):
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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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self.magic_cookie = magic_cookie
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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 = struct.calcsize(cls._MAGIC_COOKIE_UNPACK_STR)
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magic_cookie = struct.unpack_from(cls._MAGIC_COOKIE_UNPACK_STR, buf)[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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if opt is None:
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break
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opt_parse_list.append(opt)
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offset += opt.length + cls._OPT_TAG_LEN_BYTE
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return cls(opt_parse_list, len(buf), magic_cookie)
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def serialize(self):
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seri_opt = self.magic_cookie
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for opt in self.option_list:
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seri_opt += opt.serialize()
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seri_opt += binascii.a2b_hex('%x' % DHCP_END_OPT)
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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(object):
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"""DHCP (RFC 2132) options encoder/decoder class.
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This is used with ryu.lib.packet.dhcp.dhcp.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 correspondig args in this order.
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============== ====================
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Attribute Description
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============== ====================
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tag Option type.\
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(except for the 'magic cookie', 'pad option'\
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and 'end option'.)
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value Option's value.\
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(set the value that has been converted to hexadecimal.)
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length Option's value length.\
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(calculated automatically from the length of value.)
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============== ====================
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"""
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_UNPACK_STR = '!B'
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_MIN_LEN = struct.calcsize(_UNPACK_STR)
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def __init__(self, tag, value, length=0):
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super(option, self).__init__()
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self.tag = tag
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self.value = value
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self.length = length
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@classmethod
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def parser(cls, buf):
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tag = struct.unpack_from(cls._UNPACK_STR, buf)[0]
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if tag == DHCP_END_OPT or tag == DHCP_PAD_OPT:
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return None
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buf = buf[cls._MIN_LEN:]
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length = struct.unpack_from(cls._UNPACK_STR, buf)[0]
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buf = buf[cls._MIN_LEN:]
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value_unpack_str = '%ds' % length
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value = struct.unpack_from(value_unpack_str, buf)[0]
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return cls(tag, value, length)
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def serialize(self):
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if self.length == 0:
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self.length = len(self.value)
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options_pack_str = '!BB%ds' % self.length
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return struct.pack(options_pack_str, self.tag, self.length, self.value)
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