[Libguestfs] SELinux relabeling: do it by default

[Richard W.M. Jones]

On Tue, May 24, 2022 at 03:59:24PM +0200, Laszlo Ersek wrote:
> On 05/24/22 12:04, Richard W.M. Jones wrote:
> > So I didn't realise that these commits break --selinux-relabel, eg:
> >
> > $ rpm -q guestfs-tools
> > guestfs-tools-1.49.1-1.fc37.x86_64
> > $ virt-builder fedora-36 --selinux-relabel
> > virt-builder: unrecognized option '--selinux-relabel'
> > Try ‘virt-builder --help’ or consult virt-builder(1) for more
> > information.
> >
> > This is kind of bad since it breaks existing scripts.
> 
> I carefully highlighted it in the cover letter:
> 
> https://listman.redhat.com/archives/libguestfs/2022-May/028826.html

I didn't carefully read it enough :-(

> > I've intentionally avoided introducing "--no-selinux-relabel" *in
> > addition* to "--selinux-relabel". While some utilities support a
> > similar dual form (such as virt-builder's "--network" and
> > "--no-network"), with one being the default, those options are special
> > in that they are *not shared* between different utilities, and they
> > are not generated by the generator in libguestfs. The key difference
> > is that the *non-shared* options use Getopt.Set and Getopt.Clear on
> > the *same* boolean reference cell, whereas the generator introduces a
> > *separate* boolean reference cell for each option it generates (and
> > then it uses *either* Getopt.Clear *or* Getopt.Set when the option is
> > passed on the command line, dependent on the default value of the
> > reference cell). This means that "--no-selinux-relabel" and
> > "--selinux-relabel", if they both existed, would work on different
> > booleans, and that would be the source of a lot of fun (priority?
> > command line order? documentation? etc etc). So, nope to that.
> 
> On 05/24/22 12:04, Richard W.M. Jones wrote:
> > We just had a bug report about this from someone who is testing CentOS
> > Stream 9.1 (where I backported the patches already).
> >
> > This option should continue to exist, but do nothing.
> 
> The problems I outlined above remain.
> 
> What happens if someone passes both options?
> 
> Are we supposed to continue documenting "--selinux-relabel"?

AIUI this option should remain in the code, but do nothing.  If it can
never do anything[0] then we are allowed to drop it from
documentation.

[0] = I'm assuming here that even for a non-SELinux guest this option
would do nothing.  It wouldn't do some doomed attempt to relabel it.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
libguestfs lets you edit virtual machines.  Supports shell scripting,
bindings from many languages.  http://libguestfs.org