netdev - Re: [PATCH net-next v15 4/7] sch_cake: Add NAT awareness to packet classifier

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Date:   Wed, 23 May 2018 17:20:08 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     toke@...e.dk
Cc:     netdev@...r.kernel.org, cake@...ts.bufferbloat.net,
        netfilter-devel@...r.kernel.org
Subject: Re: [PATCH net-next v15 4/7] sch_cake: Add NAT awareness to packet
 classifier

From: Toke Høiland-Jørgensen <toke@...e.dk>
Date: Wed, 23 May 2018 23:05:16 +0200

> Ah, right, that could work. Is there any particular field in sk_buff
> we should stomp on for this purpose, or would you prefer a new one?
> Looking through it, the only obvious one that comes to mind is, well,
> skb->_nfct :)
> 
> If we wanted to avoid bloating sk_buff, we could add a union with that,
> fill it in the flow dissector, and just let conntrack overwrite it if
> active; then detect which is which in Cake, and read the data we need
> from _nfct if conntrack is active, and from what the flow dissector
> stored otherwise.
> 
> Is that too many hoops to jump through to avoid adding an extra field?

Space is precious in sk_buff, so yes avoid adding new members at all
costs.

How much info do you need exactly?