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# Copyright (C) 2012 Nippon Telegraph and Telephone Corporation.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
# implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import struct
from . import packet_base
from . import packet_utils
from . import icmp
from . import igmp
from . import udp
from . import tcp
from . import sctp
from . import ospf
from . import gre
from . import in_proto as inet
from os_ken.lib import addrconv
IPV4_ADDRESS_PACK_STR = '!I'
IPV4_ADDRESS_LEN = struct.calcsize(IPV4_ADDRESS_PACK_STR)
IPV4_PSEUDO_HEADER_PACK_STR = '!4s4s2xHH'
class ipv4(packet_base.PacketBase):
"""IPv4 (RFC 791) header encoder/decoder class.
NOTE: When decoding, this implementation tries to decode the upper
layer protocol even for a fragmented datagram. It isn't likely
what a user would want.
An instance has the following attributes at least.
Most of them are same to the on-wire counterparts but in host byte order.
IPv4 addresses are represented as a string like '192.0.2.1'.
__init__ takes the corresponding args in this order.
============== ======================================== ==================
Attribute Description Example
============== ======================================== ==================
version Version
header_length IHL
tos Type of Service
total_length Total Length
(0 means automatically-calculate
when encoding)
identification Identification
flags Flags
offset Fragment Offset
ttl Time to Live
proto Protocol
csum Header Checksum
(Ignored and automatically-calculated
when encoding)
src Source Address '192.0.2.1'
dst Destination Address '192.0.2.2'
option A bytearray which contains the entire
Options, or None for no Options
============== ======================================== ==================
"""
_PACK_STR = '!BBHHHBBH4s4s'
_MIN_LEN = struct.calcsize(_PACK_STR)
_TYPE = {
'ascii': [
'src', 'dst'
]
}
def __init__(self, version=4, header_length=5, tos=0,
total_length=0, identification=0, flags=0,
offset=0, ttl=255, proto=0, csum=0,
src='10.0.0.1',
dst='10.0.0.2',
option=None):
super(ipv4, self).__init__()
self.version = version
self.header_length = header_length
self.tos = tos
self.total_length = total_length
self.identification = identification
self.flags = flags
self.offset = offset
self.ttl = ttl
self.proto = proto
self.csum = csum
self.src = src
self.dst = dst
self.option = option
def __len__(self):
return self.header_length * 4
@classmethod
def parser(cls, buf):
(version, tos, total_length, identification, flags, ttl, proto, csum,
src, dst) = struct.unpack_from(cls._PACK_STR, buf)
header_length = version & 0xf
version = version >> 4
offset = flags & ((1 << 13) - 1)
flags = flags >> 13
length = header_length * 4
if length > ipv4._MIN_LEN:
option = buf[ipv4._MIN_LEN:length]
else:
option = None
msg = cls(version, header_length, tos, total_length, identification,
flags, offset, ttl, proto, csum,
addrconv.ipv4.bin_to_text(src),
addrconv.ipv4.bin_to_text(dst), option)
return msg, ipv4.get_packet_type(proto), buf[length:total_length]
def serialize(self, payload, prev):
length = len(self)
hdr = bytearray(length)
version = self.version << 4 | self.header_length
flags = self.flags << 13 | self.offset
if self.total_length == 0:
self.total_length = self.header_length * 4 + len(payload)
struct.pack_into(ipv4._PACK_STR, hdr, 0, version, self.tos,
self.total_length, self.identification, flags,
self.ttl, self.proto, 0,
addrconv.ipv4.text_to_bin(self.src),
addrconv.ipv4.text_to_bin(self.dst))
if self.option:
assert (length - ipv4._MIN_LEN) >= len(self.option)
hdr[ipv4._MIN_LEN:ipv4._MIN_LEN + len(self.option)] = self.option
self.csum = packet_utils.checksum(hdr)
struct.pack_into('!H', hdr, 10, self.csum)
return hdr
ipv4.register_packet_type(icmp.icmp, inet.IPPROTO_ICMP)
ipv4.register_packet_type(igmp.igmp, inet.IPPROTO_IGMP)
ipv4.register_packet_type(tcp.tcp, inet.IPPROTO_TCP)
ipv4.register_packet_type(udp.udp, inet.IPPROTO_UDP)
ipv4.register_packet_type(sctp.sctp, inet.IPPROTO_SCTP)
ipv4.register_packet_type(ospf.ospf, inet.IPPROTO_OSPF)
ipv4.register_packet_type(gre.gre, inet.IPPROTO_GRE)
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