Should killed process deref a jail?

[Kyle Evans]

On Wed, May 6, 2020 at 1:49 PM Kurt Jaeger <pi at freebsd.org> wrote:
>
> Hi!
>
> > In doing some testing of qemu-user-static recently, I noticed that
> > killing the last process in a non-persist jail doesn't kill off the
> > jail:
> >
> > root at viper:/usr/src# jail -c path=/ command=yes
> > ## ^C out
> >
> > root at viper:/usr/src# jls
> >    JID  IP Address      Hostname                      Path
> >    181                                                /
> >
> > root at viper:/usr/src# ps fxJ 181
> > PID TT  STAT TIME COMMAND
> >
> > As a result, I ended up with 82 jails pointed at my armv7 sysroot and
> > much surprise when I checked out `jls`. This vaguely smells like a
> > bug, is this something that should be fixed?
>
> Depends. If the last process held some socket and the socket
> is still in the state LINGER.
>
> See
>
> https://deepix.github.io/2016/10/21/tcprst.html
>
> for more details, after the heading 'What is SO_LINGER?'
>
> You can probably see those sockets with
>

That'd make sense, but in this case it's actually reproducible with
yes(1), which doesn't open up any sockets or actually use any external
resources other than write()ing to stdout.