[BUG] Openssh not closing connections on service stop

[BUG] Openssh not closing connections on service stop

[Diego]

Hi all,

I'd like to share with you what I consider a bug.

I've generally noticed in my Linux experience that I get automatically 
disconnected from an ssh session if the ssh host gets shutdown or rebooted 
with the message:
Connection to x.y.w.z closed by remote host.
Connection to x.y.w.z closed.

This doesn't seem to happen on my OSes built on core-image-minimal with 
openssh support.

Moreover I noticed that if I stop the ssh service:
# /etc/init.d/sshd stop
my ssh connections don't get dropped, I can continue using ssh session like 
nothing happened. I can even see the connection process still up and running:
# ps | grep ssh
 1790 root      4568 S    /usr/sbin/sshd
 1848 root      4852 S    sshd: root@pts/0
 1886 root      2896 S    grep ssh
# /etc/init.d/sshd stop
Stopping OpenBSD Secure Shell server: sshdstopped /usr/sbin/sshd (pid 1790)
.
# ps | grep ssh
 1848 root      4852 S    sshd: root@pts/0
 1894 root      2892 S    grep ssh

Isn't service termination supposed to stop all related connections at the same 
time? Can anybody else reproduce (or not) this issue?

Bests,
Diego

Re: [BUG] Openssh not closing connections on service stop

[Saul Wold]

On 11/27/2014 09:06 AM, Diego wrote:
> Hi all,
>
> I'd like to share with you what I consider a bug.
>
> I've generally noticed in my Linux experience that I get automatically
> disconnected from an ssh session if the ssh host gets shutdown or rebooted
> with the message:
> Connection to x.y.w.z closed by remote host.
> Connection to x.y.w.z closed.
>
Well this is because the machine is actually shut down or halted, 
therefore all processes get killed regardless, this is not necessarily a 
function of stopping the daemon

> This doesn't seem to happen on my OSes built on core-image-minimal with
> openssh support.
>
> Moreover I noticed that if I stop the ssh service:
> # /etc/init.d/sshd stop
> my ssh connections don't get dropped, I can continue using ssh session like
> nothing happened. I can even see the connection process still up and running:
> # ps | grep ssh
>   1790 root      4568 S    /usr/sbin/sshd
>   1848 root      4852 S    sshd: root@pts/0
>   1886 root      2896 S    grep ssh
> # /etc/init.d/sshd stop
> Stopping OpenBSD Secure Shell server: sshdstopped /usr/sbin/sshd (pid 1790)
> .
> # ps | grep ssh
>   1848 root      4852 S    sshd: root@pts/0
>   1894 root      2892 S    grep ssh
>
> Isn't service termination supposed to stop all related connections at the same
> time? Can anybody else reproduce (or not) this issue?
>
It may actually be designed to work this way, since the daemon spawns a 
process for each login the daemon can be restarted on a headless or 
server type machine and not loose the connection, based on googling, I 
could not find this outright on the Openssh.com site.

It appears that the dropbear sshd also has the behavior.

So I would not call this a bug.

Sau!

> Bests,
> Diego
>

Re: [BUG] Openssh not closing connections on service stop

[Diego]

In data martedì 2 dicembre 2014 16:13:09, Saul Wold ha scritto:
> <snip>
>
> > Isn't service termination supposed to stop all related connections at the
> > same time? Can anybody else reproduce (or not) this issue?
> 
> It may actually be designed to work this way, since the daemon spawns a
> process for each login the daemon can be restarted on a headless or
> server type machine and not loose the connection, based on googling, I
> could not find this outright on the Openssh.com site.
> 
> It appears that the dropbear sshd also has the behavior.
> 
> So I would not call this a bug.
> 
> Sau!
> 

Hi Saul,

I had a bit of a discussion with bluelightning and peteru in #oe. We came to 
the conclusion that having ssh connections still up after service stop is 
considered to be the correct behaviour.

On the other hand, not closing ssh connections on shutdown is generally 
considered a bug by distros, although it is considered a minor one. This 
generally requires connections being killed before network is brought down, 
which might be complicated with sysvinit. These are the links from other 
distros:
https://bugzilla.redhat.com/show_bug.cgi?id=626477
https://bugs.gentoo.org/show_bug.cgi?id=259183
https://bugs.archlinux.org/task/31250

Long story short: it would be nice to gracefully close ssh connections on 
shutdown before terminating network connections, but it's a minor issue, and 
probably not worth the effort of fixing.

Bests,
Diego