tools/generate_udp_pcap.py

   1 #!/usr/bin/env python3
   2 '''
   3 Convert a CBOR diagnostic notation file into a UDP payload
   4 for the encoded cbor.
   5 This allows straightforward test and debugging of simple pcap files.
   6
   7 Copyright 2021-2024 Brian Sipos <brian.sipos@gmail.com>
   8
   9 SPDX-License-Identifier: LGPL-2.1-or-later
  10 '''
  11
  12 from argparse import ArgumentParser
  13 from io import BytesIO
  14 import scapy
  15 from scapy.layers.l2 import Ether
  16 from scapy.layers.inet import IP, UDP
  17 from scapy.packet import Raw
  18 from scapy.utils import wrpcap
  19 from scapy.volatile import RandNum
  20 from subprocess import check_output
  21 import sys
  22
  23
  24 def main():
  25     parser = ArgumentParser()
  26     parser.add_argument('--infile', default='-',
  27                         help='The diagnostic text input file, or "-" for stdin')
  28     parser.add_argument('--sport', type=int,
  29                         help='The source port (default is random)')
  30     parser.add_argument('--dport', type=int,
  31                         help='The destination port (default is random)')
  32     parser.add_argument('--outfile', default='-',
  33                         help='The PCAP output file, or "-" for stdout')
  34     parser.add_argument('--intype', default='cbordiag',
  35                         choices=['cbordiag', 'raw'],
  36                         help='The input data type.')
  37     args = parser.parse_args()
  38
  39     # First get the CBOR data itself
  40     infile_name = args.infile.strip()
  41     if infile_name != '-':
  42         infile = open(infile_name, 'rb')
  43     else:
  44         infile = sys.stdin.buffer
  45
  46     if args.intype == 'raw':
  47         cbordata = infile.read()
  48     elif args.intype == 'cbordiag':
  49         cbordata = check_output('diag2cbor.rb', stdin=infile)
  50
  51     # Write the request directly into pcap
  52     outfile_name = args.outfile.strip()
  53     if outfile_name != '-':
  54         outfile = open(outfile_name, 'wb')
  55     else:
  56         outfile = sys.stdout.buffer
  57
  58     sport = args.sport or RandNum(49152, 65535)
  59     dport = args.dport or RandNum(49152, 65535)
  60
  61     pkt = Ether()/IP()/UDP(sport=sport, dport=dport)/Raw(cbordata)
  62     wrpcap(outfile, pkt)
  63
  64 if __name__ == '__main__':
  65     sys.exit(main())