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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 dhcp
from . import dhcp6
from . import vxlan
from . import geneve
class udp(packet_base.PacketBase):
"""UDP (RFC 768) header encoder/decoder class.
An instance has the following attributes at least.
Most of them are same to the on-wire counterparts but in host byte order.
__init__ takes the corresponding args in this order.
============== ====================
Attribute Description
============== ====================
src_port Source Port
dst_port Destination Port
total_length Length \
(0 means automatically-calculate when encoding)
csum Checksum \
(0 means automatically-calculate when encoding)
============== ====================
"""
_PACK_STR = '!HHHH'
_MIN_LEN = struct.calcsize(_PACK_STR)
def __init__(self, src_port=1, dst_port=1, total_length=0, csum=0):
super(udp, self).__init__()
self.src_port = src_port
self.dst_port = dst_port
self.total_length = total_length
self.csum = csum
@staticmethod
def get_packet_type(src_port, dst_port):
if ((src_port in [67, 68] and dst_port == 67) or
(dst_port in [67, 68] and src_port == 67)):
return dhcp.dhcp
if ((src_port in [546, 547] and dst_port == 547) or
(dst_port in [546, 547] and src_port == 547)):
return dhcp6.dhcp6
if (dst_port == vxlan.UDP_DST_PORT or
dst_port == vxlan.UDP_DST_PORT_OLD):
return vxlan.vxlan
if dst_port == geneve.UDP_DST_PORT:
return geneve.geneve
return None
@classmethod
def parser(cls, buf):
(src_port, dst_port, total_length, csum) = struct.unpack_from(
cls._PACK_STR, buf)
msg = cls(src_port, dst_port, total_length, csum)
return msg, cls.get_packet_type(src_port, dst_port), buf[msg._MIN_LEN:total_length]
def serialize(self, payload, prev):
if self.total_length == 0:
self.total_length = udp._MIN_LEN + len(payload)
h = struct.pack(udp._PACK_STR, self.src_port, self.dst_port,
self.total_length, self.csum)
if self.csum == 0:
self.csum = packet_utils.checksum_ip(
prev, self.total_length, h + payload)
h = struct.pack(udp._PACK_STR, self.src_port, self.dst_port,
self.total_length, self.csum)
return h
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