netdev - Re: [PATCH 2/2 nf-next] netfilter:nft_meta: add NFT_META

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Date:   Thu, 27 Jun 2019 21:16:51 +0200
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     wenxu <wenxu@...oud.cn>
Cc:     fw@...len.de, netfilter-devel@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH 2/2 nf-next] netfilter:nft_meta: add NFT_META_VLAN support

On Thu, Jun 27, 2019 at 09:37:53PM +0800, wenxu wrote:
> 
> 在 2019/6/27 20:35, Pablo Neira Ayuso 写道:
> > On Thu, Jun 27, 2019 at 10:09:17AM +0800, wenxu@...oud.cn wrote:
> >> From: wenxu <wenxu@...oud.cn>
> >>
> >> This patch provide a meta vlan to set the vlan tag of the packet.
> >>
> >> for q-in-q vlan id 20:
> >> meta vlan set 0x88a8:20
> > Actually, I think this is not very useful for stacked vlan since this
> > just sets/mangles the existing meta vlan data.
> >
> > We'll need infrastructure that uses skb_vlan_push() and _pop().
> >
> > Patch looks good anyway, such infrastructure to push/pop can be added
> > later on.
> >
> > Thanks.
> 
> yes, It's just ste/mangle the meta vlan data. I just wonder if we set for stacked vlan.
> vlan meta 0x88a8:20. The packet should contain a 0x8100 vlan tag, we just push the
> inner vlan and the the vlan meta with the outer 0x88a8:20. Or the packet don't contain
> only vlan tag, we add a inner 0x8100:20 tag and outer 0x88a8:20 tag?

You got me thinking here.

I wonder if we can just make this fit into nft_payload.

Or just add a new nft_vlan extension for this specifically, to push,
to mangle and to pop vlan headers. This would be a simple solution for
this.

I need to explore this by the weekend, will get back to you beginning
next week.

Feedback is welcome in any case :-), thanks.