Re: [PATCH nf-next 3/3] netfilter: nft_log: fix snaplen does not truncate packets

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Wed, Jul 20, 2016 at 07:00:13AM +0800, Liping Zhang wrote:
> At 2016-07-20 02:16:00, "Pablo Neira Ayuso" <pablo@netfilter.org> wrote:
> >On Mon, Jul 18, 2016 at 08:44:17PM +0800, Liping Zhang wrote:
> >> From: Liping Zhang <liping.zhang@spreadtrum.com>
> >> 
> >> There's a similar problem in xt_NFLOG, and was fixed by commit 7643507fe8b5
> >> ("netfilter: xt_NFLOG: nflog-range does not truncate packets"). Only set
> >> copy_len here does not work, so we should enable NF_LOG_F_COPY_LEN also.
> >
> >Applied, thanks.
> >
> >Will you send me a patch for nftables userspace to enable this flag?
> >
> >It would be good to update the translation to make sure --nflog-size
> >map to snaplen and ignore --nflog-range.
> 
> I find that nftables already support this feature, the following command mean to truncate packets
> to 100 bytes before logging to the userspace:
>   #nft add rule filter input log group 0 snaplen 100
> 
> Before my patch, it does not work.
> And after apply my patch, it works as expected.

If I git grep NF_LOG_F_COPY_LEN from the nftables.git tree, I don't
see any reference to this flag being set.

Then, nft_log kernel has been actually working fine since the
beginning. It would be good anyway if we set this flag on from
userspace to leave things in consistent state.