From: Florian Westphal <fw@strlen.de>
To: Phil Sutter <phil@nwl.cc>,
Pablo Neira Ayuso <pablo@netfilter.org>,
netfilter-devel@vger.kernel.org, fw@strlen.de
Subject: Re: [PATCH iptables 4/4] nft: keep old cache around until batch is refreshed in case of ERESTART
Date: Mon, 20 May 2019 14:06:20 +0200 [thread overview]
Message-ID: <20190520120620.nxxl65syr2b7eal7@breakpoint.cc> (raw)
In-Reply-To: <20190520120018.GA31548@orbyte.nwl.cc>
Phil Sutter <phil@nwl.cc> wrote:
> On Sun, May 19, 2019 at 06:45:08PM +0200, Phil Sutter wrote:
> [...]
> > The only way to make the above work is by keeping the original cache
> > copy around until mnl_batch_talk has finally succeeded or failed with
> > something else than ERESTART.
>
> How about a completely different approach:
>
> If memory serves right (and from reading the related Red Hat ticket),
> the actual problem we're trying to solve is that iptables-nft-restore
> creates NFT_MSG_DELTABLE only if that table exists already at the point
> of parsing but another client might create it in the mean time before
> committing.
>
> My idea for solving this was to unconditionally create NFT_MSG_NEWTABLE
> followed by NFT_MSG_DELTABLE - in case the table exists, the first one
> is a noop; in case the table doesn't exist, the second one won't provoke
> an error message from kernel space.
Does that work even work?
new table x
del table x
add rule to x // table was deleted?
Or are you talking about a new/del/new sequence?
If it works, ok/fine, but it seems ugly.
> Since NFT_MSG_DELTABLE removes the table recursively, we don't need to
> care about any content added by the other client.
Yes, we can't do this in the --noflush case though.
> Or is this about a generic solution for all commands not just
> iptables-nft-restore (without --noflush)?
Its for ipt-nft-restore, including --noflush.
It would be good though to also speed up 'iptables-nft -A' later on
by eliding cache completely.
next prev parent reply other threads:[~2019-05-20 12:06 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-19 11:51 [PATCH iptables 1/4] nft: add struct nft_cache Pablo Neira Ayuso
2019-05-19 11:51 ` [PATCH iptables 2/4] nft: statify nft_rebuild_cache() Pablo Neira Ayuso
2019-05-19 11:51 ` [PATCH iptables 3/4] nft: add flush_cache() Pablo Neira Ayuso
2019-05-19 11:51 ` [PATCH iptables 4/4] nft: keep old cache around until batch is refreshed in case of ERESTART Pablo Neira Ayuso
2019-05-19 16:45 ` Phil Sutter
2019-05-20 12:00 ` Phil Sutter
2019-05-20 12:06 ` Florian Westphal [this message]
2019-05-20 12:48 ` Phil Sutter
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