Re: passt & mbuto

[David Gibson <david@gibson.dropbear.id.au>]

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On Tue, Jun 14, 2022 at 03:33:13AM +0200, Stefano Brivio wrote:
> On Fri, 10 Jun 2022 13:50:44 +1000
> David Gibson <david(a)gibson.dropbear.id.au> wrote:
> 
> > Hi again,
> > 
> > I realized I wasn't quite right when I said that qrap problems where
> > what was currently stopping me running the passt (not pasta) tests.  I
> > did hit qrap issues somewhere, but the current stumbling block is that
> > mbuto looks for udhcpc to put into the guest image, which I can't
> > easily put onto my host system.
> > 
> > Now, in the short term, once my patch to remove usage of udhcpc from
> > the passt/pasta tests is applied, we could just remove udhcpc from the
> > mbuto profile as well.  However, that raises a wider scope issue:
> > 
> > The passt testing profile for mbuto appliances is in the mbuto tree,
> > not the passt tree.  That doesn't realy make sense, since it means any
> > change to what we need for the passt tests requires a synchronized
> > change with mbuto.  Particularly for a pretty young and project like
> > passt, that's not really tenable.  Plus, slurping an external tool
> > from some random URL in the tests is just kinda ugly.
> 
> Hmm, yes, in my ideal world mbuto would be already widely distributed
> and we could drop the git clone. On the other hand, that's still one
> long-term goal of mine, so:
> 
> > I'm not immediately sure how best to to address this:
> > 
> >  * We could make mbuto take the profiles as some sort of external
> >    file, so they can be provided by the user, rather than built into
> >    the mbuto repository.
> 
> ...I would prefer this option. Even though if you look at mbuto's git

Yeah, I think it looks the best option to me as well, though not
necessarily the quickest to implement.

> history, the last change to the passt profile was in September last
> year, so quantitatively speaking this might be more of a theoretical
> problem.

Hmm.. I strongly suspect that's more a reflection that with just one
person working on it, passt hasn't been moving that fast.  With
another person (and maybe more in future) working on it, I think this
will become a bigger problem.  It's also pretty clearly unsustainable
once we start having proper passt releases: it's no good for a frozen
released version to just pray that the latest mbuto downloaded is
still good for it.

> Actually, mbuto already allows overriding every part of a profile with
> environmental variables (this would be PROGS), but the resulting
> command line wouldn't be that nice, especially for demos.

Right, I saw that.  Maybe we can polish that up a bit and move the
passt profile from the mbuto tree to the passt tree?

> I could implement an option there which sources a shell script file
> with assignments, instead. Would that make sense?

Yeah, I think that should do the job.

> >  * We could just fork a copy of mbuto into the passt tree, making
> >    local modifications for the profile, and only manually updating it
> >    to match upstream mbuto changes.
> 
> Oh, you mean "vendoring"... :) this looks rather messy to me.

Oh, it's definitely messy, but it nonetheless has some advantages.
I'm also much more confortable vendoring something the size of mbuto
than vendoring whole libraries and frameworks the way Go does by
convention.  Even then, I'd definitely be considering that a stop-gap
workaround.

> >  * We could use an entirely different and more established tool for
> >    building our testing guest images in passt (e.g. supermin,
> >    buildroot or just picking a standard distro guest image)
> 
> supermin needs packages though: it only supports Debian and Fedora at
> the moment, and we would also have an issue with neper's tcp_{,c}rr and
> udp_rr.

Yeah, I did notice that.  It also means we might still need host
distro specific logic to get the right package names, which is pretty
horrid.

> Buildroot would be somewhat slow in demos, same for a "standard" distro
> image (which we would need to update and tweak before starting it, too).

Right, I haven't worked with buildroot much so I'm not really familiar
with it.

Hmm... one more option... could we use dracut for this?  IIRC it
already has a plugin mechanism we could potentially use to do our
specific bits.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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