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Date:   Fri, 8 May 2020 11:13:17 +1000
From:   Duncan Roe <duncan_roe@optusnet.com.au>
To:     Netfilter Development <netfilter-devel@vger.kernel.org>
Subject: Re: [PATCH libnetfilter_queue 0/3] pktbuff API updates
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Hi Pablo,

On Tue, May 05, 2020 at 02:30:34PM +0200, Pablo Neira Ayuso wrote: [...]
> > And we tell users to dimension buf to NFQ_BUFFER_SIZE. We don't even need to
> > expose pktb_head_size().

On second thoughts, maybe document in a Note the actual formula for how big the
buffer needs to be. And keep pktb_head_size().
>
> NFQ_BUFFER_SIZE tells what is the maximum netlink message size coming
> from the kernel. That netlink message contains metadata and the actual
> payload data.

I meant NFQ_BUFFER_SIZE (or some better name) to be a new macro expanding to
'0xffff + (MNL_SOCKET_BUFFER_SIZE/2)' as you suggested in
https://www.spinics.net/lists/netfilter-devel/msg66938.html. Is that only just
large enough for largest possible packet? Or is there room for struct pkt_buff
as well?

Cheers ... Duncan.