netdev - [PATCH net] net/sched: act_mirred: Add carrier check

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Message-Id: <20230424162936.537171-1-victor@mojatatu.com>
Date:   Mon, 24 Apr 2023 16:29:36 +0000
From:   Victor Nogueira <victor@...atatu.com>
To:     davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com
Cc:     netdev@...r.kernel.org, jhs@...atatu.com, xiyou.wangcong@...il.com,
        jiri@...nulli.us, kernel@...atatu.com,
        Victor Nogueira <victor@...atatu.com>
Subject: [PATCH net] 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.

Acked-by: Jamal Hadi Salim <jhs@...atatu.com>
Signed-off-by: Victor Nogueira <victor@...atatu.com>
---
 net/sched/act_mirred.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sched/act_mirred.c b/net/sched/act_mirred.c
index ec43764e92e7..0a711c184c29 100644
--- a/net/sched/act_mirred.c
+++ b/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;
-- 
2.25.1