83 lines
2.9 KiB
Python
83 lines
2.9 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright (C) 2016 Fabio Falcinelli, Maximilian Hils
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#
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# This program is free software: you can redistribute it and/or modify
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# it under the terms of the GNU Lesser General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU Lesser General Public License for more details.
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#
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# You should have received a copy of the GNU Lesser General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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import struct
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from pydivert.packet.header import Header, PayloadMixin, PortMixin
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from pydivert.util import indexbyte as i, flag_property, raw_property
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class TCPHeader(Header, PayloadMixin, PortMixin):
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ns = flag_property("ns", 12, 0b00000001)
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cwr = flag_property("cwr", 13, 0b10000000)
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ece = flag_property("ece", 13, 0b01000000)
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urg = flag_property("syn", 13, 0b00100000)
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ack = flag_property("ack", 13, 0b00010000)
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psh = flag_property("psh", 13, 0b00001000)
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rst = flag_property("rst", 13, 0b00000100)
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syn = flag_property("syn", 13, 0b00000010)
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fin = flag_property("fin", 13, 0b00000001)
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@property
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def header_len(self):
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"""
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The TCP header length.
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"""
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return self.data_offset * 4
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seq_num = raw_property('!I', 4, docs='The sequence number field.')
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ack_num = raw_property('!I', 8, docs='The acknowledgement number field.')
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window_size = raw_property('!H', 14, docs='The size of the receive window in bytes.')
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cksum = raw_property('!H', 16, docs='The TCP header checksum field.')
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urg_ptr = raw_property('!H', 18, docs='The Urgent Pointer field.')
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@property
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def data_offset(self):
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"""
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The size of TCP header in 32bit words.
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"""
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return i(self.raw[12]) >> 4
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@data_offset.setter
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def data_offset(self, val):
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if val < 5 or val > 15:
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raise ValueError("TCP data offset must be greater or equal than 5 and less than 15.")
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struct.pack_into('!B', self.raw, 12, (val << 4) | (self.reserved << 1) | self.ns)
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@property
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def reserved(self):
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"""
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The reserved field.
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"""
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return (i(self.raw[12]) >> 1) & 0x07
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@reserved.setter
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def reserved(self, val):
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struct.pack_into('!B', self.raw, 12, (self.data_offset << 4) | (val << 1) | self.ns)
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@property
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def control_bits(self):
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"""
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The Control Bits field.
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"""
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return struct.unpack_from('!H', self.raw, 12)[0] & 0x01FF
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@control_bits.setter
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def control_bits(self, val):
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struct.pack_into('!H', self.raw, 12, (self.data_offset << 12) | (self.reserved << 9) | (val & 0x01FF))
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