tools/testing/selftests/net/packetdrill/set_sysctls.py

   1 #!/usr/bin/env python3
   2 # SPDX-License-Identifier: GPL-2.0
   3
   4 """Sets sysctl values and writes a file that restores them.
   5
   6 The arguments are of the form "<proc-file>=<val>" separated by spaces.
   7 The program first reads the current value of the proc-file and creates
   8 a shell script named "/tmp/sysctl_restore_${PACKETDRILL_PID}.sh" which
   9 restores the values when executed. It then sets the new values.
  10
  11 PACKETDRILL_PID is set by packetdrill to the pid of itself, so a .pkt
  12 file could restore sysctls by running `/tmp/sysctl_restore_${PPID}.sh`
  13 at the end.
  14 """
  15
  16 import os
  17 import subprocess
  18 import sys
  19
  20 filename = '/tmp/sysctl_restore_%s.sh' % os.environ['PACKETDRILL_PID']
  21
  22 # Open file for restoring sysctl values
  23 restore_file = open(filename, 'w')
  24 print('#!/bin/bash', file=restore_file)
  25
  26 for a in sys.argv[1:]:
  27   sysctl = a.split('=')
  28   # sysctl[0] contains the proc-file name, sysctl[1] the new value
  29
  30   # read current value and add restore command to file
  31   cur_val = subprocess.check_output(['cat', sysctl[0]], universal_newlines=True)
  32   print('echo "%s" > %s' % (cur_val.strip(), sysctl[0]), file=restore_file)
  33
  34   # set new value
  35   cmd = 'echo "%s" > %s' % (sysctl[1], sysctl[0])
  36   os.system(cmd)
  37
  38 os.system('chmod u+x %s' % filename)