netdev - Re: [PATCH net v2] net/sched: act

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Message-ID: <20230424104408.63ba1159@hermes.local>
Date:   Mon, 24 Apr 2023 10:44:08 -0700
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     Leon Romanovsky <leon@...nel.org>
Cc:     Victor Nogueira <victor@...atatu.com>, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        netdev@...r.kernel.org, jhs@...atatu.com, xiyou.wangcong@...il.com,
        jiri@...nulli.us, kernel@...atatu.com
Subject: Re: [PATCH net v2] net/sched: act_mirred: Add carrier check

On Mon, 24 Apr 2023 20:36:02 +0300
Leon Romanovsky <leon@...nel.org> wrote:

> > 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.
> > 

Then fix the driver. It shouldn't hang.
Other drivers just drop packets if link is down.