From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jamal Hadi Salim <jhs@mojatatu.com>
Subject: Re: [PATCH net-next] tc: fix tc actions in case of shared skb
Date: Mon, 13 Jul 2015 09:13:58 -0400
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Cc: Daniel Borkmann <daniel@iogearbox.net>,
	Jiri Pirko <jiri@resnulli.us>, netdev@vger.kernel.org
To: Alexei Starovoitov <ast@plumgrid.com>,
	"David S. Miller" <davem@davemloft.net>
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On 07/10/15 20:10, Alexei Starovoitov wrote:
> TC actions need to check for very unlikely event skb->users != 1,
> otherwise subsequent pskb_may_pull/pskb_expand_head will crash.
> When skb_shared() just drop the packet, since in the middle of actions
> it's too late to call skb_share_check(), since classifiers/actions assume
> the same skb pointer.
>

Alexei,
To add to what Dave said - are the rules specified here:
Documentation/networking/tc-actions-env-rules.txt
insufficient?

cheers,
jamal