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Date:   Tue, 10 Sep 2019 00:12:18 +0200
From:   Florian Westphal <fw@strlen.de>
To:     Eric Garver <eric@garver.life>, Florian Westphal <fw@strlen.de>,
        netfilter-devel@vger.kernel.org,
        Pablo Neira Ayuso <pablo@netfilter.org>
Subject: Re: [PATCH nftables 3/3] src: mnl: retry when we hit -ENOBUFS
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Eric Garver <eric@garver.life> wrote:
> > +			if (errno == ENOBUFS && enobuf_restarts++ < 3) {
> > +				scale *= 2;
> > +				goto restart;
> > +			}
> 
> If this restart is triggered it causes rules to be duplicated. We send
> the same batch again.

Right :-(

> I'm hitting this on x86_64. Maybe we need find a better way to estimate
> the rcvbuffer in the case of --echo. By the time we see ENOBUFS we're
> already in a bad way - events have already be lost.

Thats correct.  Pablo, I don't see a way for dynamic probing, as Eric
explains the error occurs after the fact so we cannot recover.

I will send a best-effort fix in a bit.