netdev - Re: [PATCH net-next] tc: fix tc actions in case of shared skb

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Message-ID: <55A52ED3.8090003@plumgrid.com>
Date:	Tue, 14 Jul 2015 08:46:27 -0700
From:	Alexei Starovoitov <ast@...mgrid.com>
To:	Daniel Borkmann <daniel@...earbox.net>
CC:	David Miller <davem@...emloft.net>, jhs@...atatu.com,
	jiri@...nulli.us, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] tc: fix tc actions in case of shared skb

On 7/14/15 3:29 AM, Daniel Borkmann wrote:
> One other thing that comes to mind, not sure if it's worth it though,
> would be to split the skb->tc_verd's TC_NCLS itself into TC_NCLS/TC_NACT,
> so that you can go into the classifier, but skip the action part.
>
> Since in tcf_action_exec(), we already test for that, you might be able
> to add this with no extra cost. pktgen would then need to tag its skb
> with TC_NACT, so that you'll always return with TC_ACT_OK. And if you
> really would want to test tc actions, then w/o pktgen bursting ...

imo it's even uglier. Majority of the actions are fine with shared skb,
so blank disable is no good at all.
The cost of 'unlikely(is_pktgen_shared_skb' is tiny, but fine,
we dug up the dirt enough.
I'm taking option 3 (do nothing) at this point.

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