netdev - Re: [PATCH net 2/5] netfilter: nf_tables: add position handle in event notification

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Message-ID: <20210929191953.00378ec4@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Wed, 29 Sep 2021 19:19:53 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Pablo Neira Ayuso <pablo@...filter.org>
Cc:     netfilter-devel@...r.kernel.org, davem@...emloft.net,
        netdev@...r.kernel.org
Subject: Re: [PATCH net 2/5] netfilter: nf_tables: add position handle in
 event notification

On Thu, 30 Sep 2021 01:04:57 +0200 Pablo Neira Ayuso wrote:
> Add position handle to allow to identify the rule location from netlink
> events. Otherwise, userspace cannot incrementally update a userspace
> cache through monitoring events.
> 
> Skip handle dump if the rule has been either inserted (at the beginning
> of the ruleset) or appended (at the end of the ruleset), the
> NLM_F_APPEND netlink flag is sufficient in these two cases.
> 
> Handle NLM_F_REPLACE as NLM_F_APPEND since the rule replacement
> expansion appends it after the specified rule handle.
> 
> Fixes: 96518518cc41 ("netfilter: add nftables")
> Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>

Let me defer to Dave on this one. Krzysztof K recently provided us with
this quote:

"One thing that does bother [Linus] is developers who send him fixes in the
-rc2 or -rc3 time frame for things that never worked in the first place.
If something never worked, then the fact that it doesn't work now is not
a regression, so the fixes should just wait for the next merge window.
Those fixes are, after all, essentially development work."

	https://lwn.net/Articles/705245/

Maybe the thinking has evolved since, but this patch strikes me as odd.
We forgot to put an attribute in netlink 8 years ago, and suddenly it's
urgent to fill it in?  Something does not connect for me, certainly the
commit message should have explained things better...