100 lines
3.5 KiB
Python
100 lines
3.5 KiB
Python
#!/usr/bin/env python3
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#
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# Copyright (c) 2022, The OpenThread Authors.
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# All rights reserved.
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#
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# Redistribution and use in source and binary forms, with or without
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# modification, are permitted provided that the following conditions are met:
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# 1. Redistributions of source code must retain the above copyright
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# notice, this list of conditions and the following disclaimer.
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# 2. Redistributions in binary form must reproduce the above copyright
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# notice, this list of conditions and the following disclaimer in the
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# documentation and/or other materials provided with the distribution.
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# 3. Neither the name of the copyright holder nor the
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# names of its contributors may be used to endorse or promote products
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# derived from this software without specific prior written permission.
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#
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# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
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# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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# POSSIBILITY OF SUCH DAMAGE.
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#
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""" Module to provide codec utilities for .pcap formatters. """
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import struct
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import time
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# https://www.tcpdump.org/linktypes.html
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DLT_IEEE802_15_4_WITHFCS = 195
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PCAP_MAGIC_NUMBER = 0xA1B2C3D4
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PCAP_VERSION_MAJOR = 2
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PCAP_VERSION_MINOR = 4
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class PcapCodec(object):
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""" Utility class for .pcap formatters. """
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def __init__(self, filename, channel):
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self._dlt = DLT_IEEE802_15_4_WITHFCS
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if not filename.endswith('.pcap'):
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raise ValueError('Filename should end with .pcap')
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self._pcap_file = open(filename, 'wb')
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self._pcap_file.write(self.encode_header())
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self._channel = channel
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def encode_header(self):
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""" Return a pcap file header. """
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return struct.pack(
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'<LHHLLLL',
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PCAP_MAGIC_NUMBER,
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PCAP_VERSION_MAJOR,
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PCAP_VERSION_MINOR,
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0,
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0,
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256,
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self._dlt,
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)
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def encode_frame(self, frame, sec, usec):
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""" Return a pcap encapsulation of the given frame. """
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# Ignore the first byte storing channel.
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frame = frame[1:]
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length = len(frame)
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pcap_frame = struct.pack('<LLLL', sec, usec, length, length)
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pcap_frame += frame
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return pcap_frame
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def _get_timestamp(self):
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""" Return the internal timestamp. """
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timestamp = time.time()
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timestamp_sec = int(timestamp)
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timestamp_usec = int((timestamp - timestamp_sec) * 1000000)
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return timestamp_sec, timestamp_usec
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def append(self, frame):
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""" Append a frame. """
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# Filter channel.
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if frame[0] != self._channel:
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return
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timestamp = self._get_timestamp()
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pkt = self.encode_frame(frame, *timestamp)
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self._pcap_file.write(pkt)
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self._pcap_file.flush()
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def close(self):
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""" Close the pcap file. """
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self._pcap_file.close()
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