153 lines
5.4 KiB
Python
153 lines
5.4 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 struct
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from . import packet_base
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from . import packet_utils
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from . import icmp
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from . import igmp
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from . import udp
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from . import tcp
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from . import sctp
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from . import ospf
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from . import gre
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from . import in_proto as inet
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from os_ken.lib import addrconv
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IPV4_ADDRESS_PACK_STR = '!I'
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IPV4_ADDRESS_LEN = struct.calcsize(IPV4_ADDRESS_PACK_STR)
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IPV4_PSEUDO_HEADER_PACK_STR = '!4s4s2xHH'
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class ipv4(packet_base.PacketBase):
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"""IPv4 (RFC 791) header encoder/decoder class.
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NOTE: When decoding, this implementation tries to decode the upper
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layer protocol even for a fragmented datagram. It isn't likely
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what a user would want.
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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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IPv4 addresses are represented as a string like '192.0.2.1'.
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__init__ takes the corresponding args in this order.
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============== ======================================== ==================
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Attribute Description Example
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============== ======================================== ==================
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version Version
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header_length IHL
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tos Type of Service
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total_length Total Length
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(0 means automatically-calculate
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when encoding)
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identification Identification
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flags Flags
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offset Fragment Offset
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ttl Time to Live
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proto Protocol
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csum Header Checksum
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(Ignored and automatically-calculated
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when encoding)
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src Source Address '192.0.2.1'
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dst Destination Address '192.0.2.2'
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option A bytearray which contains the entire
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Options, or None for no Options
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============== ======================================== ==================
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"""
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_PACK_STR = '!BBHHHBBH4s4s'
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_MIN_LEN = struct.calcsize(_PACK_STR)
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_TYPE = {
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'ascii': [
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'src', 'dst'
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]
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}
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def __init__(self, version=4, header_length=5, tos=0,
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total_length=0, identification=0, flags=0,
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offset=0, ttl=255, proto=0, csum=0,
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src='10.0.0.1',
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dst='10.0.0.2',
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option=None):
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super(ipv4, self).__init__()
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self.version = version
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self.header_length = header_length
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self.tos = tos
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self.total_length = total_length
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self.identification = identification
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self.flags = flags
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self.offset = offset
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self.ttl = ttl
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self.proto = proto
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self.csum = csum
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self.src = src
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self.dst = dst
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self.option = option
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def __len__(self):
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return self.header_length * 4
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@classmethod
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def parser(cls, buf):
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(version, tos, total_length, identification, flags, ttl, proto, csum,
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src, dst) = struct.unpack_from(cls._PACK_STR, buf)
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header_length = version & 0xf
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version = version >> 4
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offset = flags & ((1 << 13) - 1)
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flags = flags >> 13
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length = header_length * 4
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if length > ipv4._MIN_LEN:
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option = buf[ipv4._MIN_LEN:length]
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else:
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option = None
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msg = cls(version, header_length, tos, total_length, identification,
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flags, offset, ttl, proto, csum,
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addrconv.ipv4.bin_to_text(src),
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addrconv.ipv4.bin_to_text(dst), option)
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return msg, ipv4.get_packet_type(proto), buf[length:total_length]
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def serialize(self, payload, prev):
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length = len(self)
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hdr = bytearray(length)
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version = self.version << 4 | self.header_length
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flags = self.flags << 13 | self.offset
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if self.total_length == 0:
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self.total_length = self.header_length * 4 + len(payload)
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struct.pack_into(ipv4._PACK_STR, hdr, 0, version, self.tos,
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self.total_length, self.identification, flags,
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self.ttl, self.proto, 0,
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addrconv.ipv4.text_to_bin(self.src),
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addrconv.ipv4.text_to_bin(self.dst))
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if self.option:
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assert (length - ipv4._MIN_LEN) >= len(self.option)
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hdr[ipv4._MIN_LEN:ipv4._MIN_LEN + len(self.option)] = self.option
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self.csum = packet_utils.checksum(hdr)
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struct.pack_into('!H', hdr, 10, self.csum)
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return hdr
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ipv4.register_packet_type(icmp.icmp, inet.IPPROTO_ICMP)
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ipv4.register_packet_type(igmp.igmp, inet.IPPROTO_IGMP)
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ipv4.register_packet_type(tcp.tcp, inet.IPPROTO_TCP)
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ipv4.register_packet_type(udp.udp, inet.IPPROTO_UDP)
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ipv4.register_packet_type(sctp.sctp, inet.IPPROTO_SCTP)
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ipv4.register_packet_type(ospf.ospf, inet.IPPROTO_OSPF)
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ipv4.register_packet_type(gre.gre, inet.IPPROTO_GRE)
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