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.

Fixes: b57dc7c13ea9 ("net/sched: Introduce action ct")
Signed-off-by: Roi Dayan <[e-mail]>
Signed-off-by: Hangbin Liu <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/sched/act_mirred.c

···
 			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;