Re: [PATCH v3] conf: Accept duplicate and conflicting options, the last one wins

[Paul Holzinger <pholzing@redhat.com>]

On 20/06/2024 19:19, 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>

Tested-by: Paul Holzinger <pholzing@redhat.com>

> ---
> v3:
>    - override --gateway and --dns-forward with the last given option
>      for a given address family, too
assuming you mean --address here as --gateway already worked
>
> 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  | 146 ++++++++++++++++----------------------------------------
>   passt.1 |  17 +++++++
>   2 files changed, 59 insertions(+), 104 deletions(-)
>
-- 
Paul Holzinger