net/sched: act_mirred: Add carrier check

There are cases where the device is adminstratively UP, but operationally
down. For example, we have a physical device (Nvidia ConnectX-6 Dx, 25Gbps)
who's cable was pulled out, here is its ip link output:

5: ens2f1: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN mode DEFAULT group default qlen 1000
    link/ether b8:ce:f6:4b:68:35 brd ff:ff:ff:ff:ff:ff
    altname enp179s0f1np1

As you can see, it's administratively UP but operationally down.
In this case, sending a packet to this port caused a nasty kernel hang (so
nasty that we were unable to capture it). Aborting a transmit based on
operational status (in addition to administrative status) fixes the issue.

Fixes: 1da177e ("Linux-2.6.12-rc2")
Acked-by: Jamal Hadi Salim <[email protected]>
Signed-off-by: Victor Nogueira <[email protected]>
v1->v2: Add fixes tag
v2->v3: Remove blank line between tags + add change log, suggested by Leon
Signed-off-by: David S. Miller <[email protected]>

Author: vbnogueira

net/sched/act_mirred.c

@@ -264,7 +264,7 @@ TC_INDIRECT_SCOPE int tcf_mirred_act(struct sk_buff *skb,
 		goto out;
 	}
 
-	if (unlikely(!(dev->flags & IFF_UP))) {
+	if (unlikely(!(dev->flags & IFF_UP)) || !netif_carrier_ok(dev)) {
 		net_notice_ratelimited("tc mirred to Houston: device %s is down\n",
 				       dev->name);
 		goto out;