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)
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