netdev - Re: [PATCH RFC v2 net-next 02/25] net/ipv6: Refactor address dump to push inet6_fill_args to in6_dump

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Date:   Tue, 2 Oct 2018 12:54:25 +0200
From:   Jiri Benc <jbenc@...hat.com>
To:     David Ahern <dsahern@...nel.org>
Cc:     netdev@...r.kernel.org, davem@...emloft.net, christian@...uner.io,
        stephen@...workplumber.org, David Ahern <dsahern@...il.com>
Subject: Re: [PATCH RFC v2 net-next 02/25] net/ipv6: Refactor address dump
 to push inet6_fill_args to in6_dump_addrs

On Mon,  1 Oct 2018 17:28:28 -0700, David Ahern wrote:
> Pull the inet6_fill_args arg up to in6_dump_addrs and move netnsid
> into it. Since IFA_TARGET_NETNSID is a kernel side filter add the
> NLM_F_DUMP_FILTERED flag so userspace knows the request was honored.

IFA_TARGET_NETNSID is not a filter.

"Filter" returns a subset of the results. It's kind of optimization
when one is interested only in some data but not all of them. Instead
of dumping everything, going through the results and picking only the
data one is interested in, it's better to pass a filter and get only
the relevant data. But you're not really required to: you can filter in
your app.

By contrast, IFA_TARGET_NETNSID returns a completely different set of
data. It's impossible to not set it and filter the results in your app.

As the consequence, IFA_TARGET_NETNSID must not set NLM_F_DUMP_FILTERED
(if not complemented by a real filter).

I understand that you want to differentiate between data dumped without
and with IFA_TARGET_NETNSID present. But we already have that: the
IFA_TARGET_NETNSID attribute is returned back in the latter case.

Nacked-by: Jiri Benc <jbenc@...hat.com>

 Jiri