linux-kernel - [PATCH 5.4 23/62] net: sched: act_mirred: Reset ct info when mirror/redirect skb

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Date:   Mon, 16 Aug 2021 15:01:55 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Roi Dayan <roid@...dia.com>,
        Hangbin Liu <liuhangbin@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 23/62] net: sched: act_mirred: Reset ct info when mirror/redirect skb

From: Hangbin Liu <liuhangbin@...il.com>

[ Upstream commit d09c548dbf3b31cb07bba562e0f452edfa01efe3 ]

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.

Fixes: b57dc7c13ea9 ("net/sched: Introduce action ct")
Signed-off-by: Roi Dayan <roid@...dia.com>
Signed-off-by: Hangbin Liu <liuhangbin@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 8327ef9793ef..e3ff884a48c5 100644
--- a/net/sched/act_mirred.c
+++ b/net/sched/act_mirred.c
@@ -261,6 +261,9 @@ 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;
-- 
2.30.2