SSH session does not get terminated with cpp reboot command but with CLI command reboot

Question

I have a small cpp application which will reboot the system. This works very well so far.

sync(); //need for data safety
reboot(RB_AUTOBOOT);

Unless you are connected via SSH and run this program on the connected device. Then the SSH connection hangs.

If you are connected via SSH and use the CLI commands

sudo reboot

or

sudo shutdown -r now

The SSH connection will be terminated with the following message

Connection to xxx.xxx.xxx.xxx closed by remote host.
Connection to xxx.xxx.xxx.xxx closed.

How do I get the same behaviour with the cpp reboot method?

I read https://man7.org/linux/man-pages/man2/reboot.2.html and search the internet, but didn't found something about this topic.

Answer 1

The sudo reboot command will notify init that you want a reboot, init will kill all user-space processes and then do the actual kernel reboot.

The reboot syscall does the equivalent of sudo reboot -f (immediate reboot).

You could try to kill everything yourself and then invoke the syscall.

Or you could ask init, which by convention lives at PID=1. Reboot is signalled by sending it a SIGINT.

So:

#include <sys/types.h>
#include <signal.h>

int main() {
    kill(1, SIGINT);
}

should do it.