netdev - Re: [PATCH net] net: sched: act_mirred: Reset ct info when mirror/redirect skb

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Date:   Mon, 9 Aug 2021 11:35:38 +0300
From:   Roi Dayan <roid@...dia.com>
To:     Hangbin Liu <liuhangbin@...il.com>, <netdev@...r.kernel.org>
CC:     Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Marcelo Ricardo Leitner <mleitner@...hat.com>,
        Alaa Hleihel <ahleihel@...hat.com>,
        Davide Caratti <dcaratti@...hat.com>,
        Aaron Conole <aconole@...hat.com>
Subject: Re: [PATCH net] net: sched: act_mirred: Reset ct info when
 mirror/redirect skb



On 2021-08-09 10:04 AM, Hangbin Liu wrote:
> When mirror/redirect a skb to a different port, the ct info should be reset
> for reclassification. Or the pkts will match unexpected rules. For example,
> with following topology and commands:
> 
>      -----------
>                |
>         veth0 -+-------
>                |
>         veth1 -+-------
>                |
>     ------------
> 
>   tc qdisc add dev veth0 clsact
>   # The same with "action mirred egress mirror dev veth1" or "action mirred ingress redirect dev veth1"
>   tc filter add dev veth0 egress chain 1 protocol ip flower ct_state +trk action mirred ingress mirror dev veth1
>   tc filter add dev veth0 egress chain 0 protocol ip flower ct_state -inv action ct commit action goto chain 1
>   tc qdisc add dev veth1 clsact
>   tc filter add dev veth1 ingress chain 0 protocol ip flower ct_state +trk action drop
> 
>   ping <remove ip via veth0> &
>   tc -s filter show dev veth1 ingress
> 
> With command 'tc -s filter show', we can find the pkts were dropped on
> veth1.
> 

We can add a fixes line on the commit added ct support
Fixes: b57dc7c13ea9 ("net/sched: Introduce action ct")

> Signed-off-by: Roi Dayan <roid@...dia.com>
> Signed-off-by: Hangbin Liu <liuhangbin@...il.com>
> ---
>   net/sched/act_mirred.c | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/net/sched/act_mirred.c b/net/sched/act_mirred.c
> index 7153c67f641e..2ef4cd2c848b 100644
> --- a/net/sched/act_mirred.c
> +++ b/net/sched/act_mirred.c
> @@ -273,6 +273,9 @@ static int tcf_mirred_act(struct sk_buff *skb, const struct tc_action *a,
>   			goto out;
>   	}
>   
> +	/* All mirred/redirected skbs should clear previous ct info */
> +	nf_reset_ct(skb2);
> +
>   	want_ingress = tcf_mirred_act_wants_ingress(m_eaction);
>   
>   	expects_nh = want_ingress || !m_mac_header_xmit;
>