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

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Date:   Mon,  9 Aug 2021 15:04:55 +0800
From:   Hangbin Liu <liuhangbin@...il.com>
To:     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>,
        Hangbin Liu <liuhangbin@...il.com>, Roi Dayan <roid@...dia.com>
Subject: [PATCH net] net: sched: act_mirred: Reset ct info when mirror/redirect skb

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.

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;
-- 
2.31.1