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 6The arguments are of the form "<proc-file>=<val>" separated by spaces. 7The program first reads the current value of the proc-file and creates 8a shell script named "/tmp/sysctl_restore_${PACKETDRILL_PID}.sh" which 9restores the values when executed. It then sets the new values. 10 11PACKETDRILL_PID is set by packetdrill to the pid of itself, so a .pkt 12file could restore sysctls by running `/tmp/sysctl_restore_${PPID}.sh` 13at the end. 14""" 15 16import os 17import subprocess 18import sys 19 20filename = '/tmp/sysctl_restore_%s.sh' % os.environ['PACKETDRILL_PID'] 21 22# Open file for restoring sysctl values 23restore_file = open(filename, 'w') 24print('#!/bin/bash', file=restore_file) 25 26for 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 38os.system('chmod u+x %s' % filename) 39