81 lines
2.8 KiB
Python
81 lines
2.8 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 dhcp
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from . import vxlan
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class udp(packet_base.PacketBase):
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"""UDP (RFC 768) header encoder/decoder class.
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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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src_port Source Port
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dst_port Destination Port
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total_length Length \
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(0 means automatically-calculate when encoding)
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csum Checksum \
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(0 means automatically-calculate when encoding)
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============== ====================
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"""
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_PACK_STR = '!HHHH'
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_MIN_LEN = struct.calcsize(_PACK_STR)
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def __init__(self, src_port=1, dst_port=1, total_length=0, csum=0):
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super(udp, self).__init__()
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self.src_port = src_port
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self.dst_port = dst_port
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self.total_length = total_length
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self.csum = csum
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@staticmethod
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def get_packet_type(src_port, dst_port):
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if ((src_port == 68 and dst_port == 67) or
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(src_port == 67 and dst_port == 68)):
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return dhcp.dhcp
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if (dst_port == vxlan.UDP_DST_PORT or
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dst_port == vxlan.UDP_DST_PORT_OLD):
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return vxlan.vxlan
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return None
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@classmethod
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def parser(cls, buf):
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(src_port, dst_port, total_length, csum) = struct.unpack_from(
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cls._PACK_STR, buf)
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msg = cls(src_port, dst_port, total_length, csum)
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return msg, cls.get_packet_type(src_port, dst_port), buf[msg._MIN_LEN:total_length]
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def serialize(self, payload, prev):
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if self.total_length == 0:
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self.total_length = udp._MIN_LEN + len(payload)
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h = struct.pack(udp._PACK_STR, self.src_port, self.dst_port,
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self.total_length, self.csum)
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if self.csum == 0:
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self.csum = packet_utils.checksum_ip(
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prev, self.total_length, h + payload)
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h = struct.pack(udp._PACK_STR, self.src_port, self.dst_port,
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self.total_length, self.csum)
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return h
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