Re: [PATCH v2] conf: Accept duplicate and conflicting options, the last one wins

[Stefano Brivio <sbrivio@redhat.com>]

On Thu, 20 Jun 2024 11:06:48 +0200
Paul Holzinger <pholzing@redhat.com> wrote:

> On 19/06/2024 17:40, Stefano Brivio wrote:
> > In multiple occasions, especially when passt(1) and pasta(1) are used
> > in integrations such as the one with Podman, the ability to override
> > earlier options on the command line with later one would have been
> > convenient.
> >
> > Recently, to debug a number of issues happening with Podman, I would
> > have liked to ask users to share a debug log by passing --debug as
> > additional option, but pasta refuses --quiet (always passed by Podman)
> > and --debug at the same time.
> >
> > On top of this, Podman lets users specify other pasta options in its
> > containers.conf(5) file, as well as on the command line.
> >
> > The options from the configuration files are appended together with
> > the ones from the command line, which makes it impossible for users to
> > override options from the configuration file, if duplicated options
> > are refused, unless Podman takes care of sorting them, which is
> > clearly not sustainable.
> >
> > For --debug and --trace, somebody took care of this on Podman side at:
> >    https://github.com/containers/common/pull/2052
> >
> > but this doesn't fix the issue with other options, and we'll have
> > anyway older versions of Podman around, too.
> >
> > I think there's some value in telling users about duplicated or
> > conflicting options, because that might reveal issues in integrations
> > or accidental misconfigurations, but by now I'm fairly convinced that
> > the downsides outweigh this.
> >
> > Drop checks about duplicate options and mutually exclusive ones. In
> > some cases, we need to also undo a couple of initialisations caused
> > by earlier options, but this looks like a simplification, overall.
> >
> > Notable exception: --stderr still conflicts with --log-file, because
> > users might have the expectation that they don't actually conflict.
> > But they do conflict in the existing implementation, so it's safer
> > to make sure that the users notice that.
> >
> > Suggested-by: Paul Holzinger <pholzing@redhat.com>
> > Suggested-by: David Gibson <david@gibson.dropbear.id.au>
> > Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
> > ---
> > v2:
> >    - report --log-file and --stderr as conflicting, but accept
> >      multiple options if they don't conflict
> >    - for --log-file and --pcap, make it clear in the man page that
> >      the general principle still applies: only the last one (of each)
> >      takes effect
> >    - add some more context about Podman and how the list of pasta
> >      options is built there, in the commit message
> >
> >   conf.c  | 134 ++++++++++++++++----------------------------------------
> >   passt.1 |  17 +++++++
> >   2 files changed, 55 insertions(+), 96 deletions(-)  
> 
> I have done some tests and while you changed --gateway to only take the 
> last one --address was not changed:
> 
> ./pasta --config-net -a 10.0.0.1 -a 10.0.0.2 ip a
> 
> Invalid address: 10.0.0.2
> 
> The error is clearly nonsensical as the address is valid. So either it 
> should match the gateway behavior or the error must clearly state that 
> multiple addresses are not accepted if this is what you want.

Gosh, thanks, nice catch, v3 coming (in a while).

-- 
Stefano