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/*
* Copyright (c) 2015, Yawning Angel <yawning at torproject dot org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* * Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
package main
import (
"fmt"
"os"
"runtime"
"syscall"
"time"
)
var parentMonitorOSInit func() error
func initParentMonitor() error {
// Until #15435 is implemented, there is no reliable way to see if
// the parent has died that is portable/platform independent/reliable.
//
// Do the next best thing and use various kludges and hacks:
// * Linux - Platform specific code that should always work.
// * Other U*IX - Somewhat generic code, that works unless the parent
// dies before the monitor is initialized.
// * Windows - Log an error, can't be bothered to figure out how
// to handle this there.
if parentMonitorOSInit != nil {
return parentMonitorOSInit()
} else if runtime.GOOS != "windows" {
ppid := os.Getppid()
go parentMonitorPpidChange(ppid)
return nil
}
return fmt.Errorf("unsupported on: %s", runtime.GOOS)
}
func parentMonitorPpidChange(ppid int) {
// Under most if not all U*IX systems, the parent PID will change
// to that of init once the parent dies. There are several notable
// exceptions (Slowlaris/Android), but the parent PID changes
// under those platforms as well.
//
// Naturally we lose if the parent has died by the when the
// Getppid() call was issued in our parent, but, this is better
// than nothing.
const ppidPollInterval = 1 * time.Second
for ppid == os.Getppid() {
time.Sleep(ppidPollInterval)
}
// If possible SIGTERM ourself so that the normal shutdown code
// gets invoked. If any of that fails, exit anyway, we are a
// defunt process.
noticef("Parent pid changed: %d (was %d)", os.Getppid(), ppid)
if p, err := os.FindProcess(os.Getpid()); err == nil {
if err := p.Signal(syscall.SIGTERM); err == nil {
return
}
warnf("Failed to SIGTERM ourself: %v", err)
} else {
warnf("Failed to find our own process: %v", err)
}
os.Exit(-1)
}
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