| #!/usr/bin/env python3 | |
| # SPDX-License-Identifier: GPL-2.0 | |
| """Sets sysctl values and writes a file that restores them. | |
| The arguments are of the form "<proc-file>=<val>" separated by spaces. | |
| The program first reads the current value of the proc-file and creates | |
| a shell script named "/tmp/sysctl_restore_${PACKETDRILL_PID}.sh" which | |
| restores the values when executed. It then sets the new values. | |
| PACKETDRILL_PID is set by packetdrill to the pid of itself, so a .pkt | |
| file could restore sysctls by running `/tmp/sysctl_restore_${PPID}.sh` | |
| at the end. | |
| """ | |
| import os | |
| import subprocess | |
| import sys | |
| filename = '/tmp/sysctl_restore_%s.sh' % os.environ['PACKETDRILL_PID'] | |
| # Open file for restoring sysctl values | |
| restore_file = open(filename, 'w') | |
| print('#!/bin/bash', file=restore_file) | |
| for a in sys.argv[1:]: | |
| sysctl = a.split('=') | |
| # sysctl[0] contains the proc-file name, sysctl[1] the new value | |
| # read current value and add restore command to file | |
| cur_val = subprocess.check_output(['cat', sysctl[0]], universal_newlines=True) | |
| print('echo "%s" > %s' % (cur_val.strip(), sysctl[0]), file=restore_file) | |
| # set new value | |
| cmd = 'echo "%s" > %s' % (sysctl[1], sysctl[0]) | |
| os.system(cmd) | |
| os.system('chmod u+x %s' % filename) |