netdev - Re: [PATCH net] net/sched: act_mirred: fix fragment the packet after defrag in act

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Date:   Tue, 30 Jun 2020 08:57:13 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     wenxu@...oud.cn, paulb@...lanox.com
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH net] net/sched: act_mirred: fix fragment the packet after
 defrag in act_ct



On 6/29/20 7:54 PM, wenxu@...oud.cn wrote:
> From: wenxu <wenxu@...oud.cn>
> 
> The fragment packets do defrag in act_ct module. The reassembled packet
> over the mtu in the act_mirred. This big packet should be fragmented
> to send out.
> 
> Fixes: b57dc7c13ea9 ("net/sched: Introduce action ct")
> Signed-off-by: wenxu <wenxu@...oud.cn>
> ---
> This patch is based on
> http://patchwork.ozlabs.org/project/netdev/patch/1593422178-26949-1-git-send-email-wenxu@ucloud.cn/
> 
>  include/net/sch_generic.h |   6 +-
>  net/sched/act_ct.c        |   7 ++-
>  net/sched/act_mirred.c    | 157 ++++++++++++++++++++++++++++++++++++++++++++--
>  3 files changed, 158 insertions(+), 12 deletions(-)
> 
> diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
> index c510b03..3597244 100644
> --- a/include/net/sch_generic.h
> +++ b/include/net/sch_generic.h
> @@ -384,6 +384,7 @@ struct qdisc_skb_cb {
>  	};
>  #define QDISC_CB_PRIV_LEN 20
>  	unsigned char		data[QDISC_CB_PRIV_LEN];
> +	u16			mru;
>  };
> 


Wow, this change is potentially a big problem.

Explain why act_ct/act_mirred need to pollute qdisc_skb_cb