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Date:   Tue, 05 Jan 2021 16:05:21 -0800 (PST)
Message-Id: <20210105.160521.1279064249478522010.davem@davemloft.net>
To:     zhutong@amazon.com
Cc:     sashal@kernel.org, edumazet@google.com, vvs@virtuozzo.com,
        netdev@vger.kernel.org, stable@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] neighbour: Disregard DEAD dst in neigh_update
From:   David Miller <davem@davemloft.net>
In-Reply-To: <20201230225415.GA490@ucf43ac461c9a53.ant.amazon.com>
References: <20201230225415.GA490@ucf43ac461c9a53.ant.amazon.com>
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From: Tong Zhu <zhutong@amazon.com>
Date: Wed, 30 Dec 2020 17:54:23 -0500

> In 4.x kernel a dst in DST_OBSOLETE_DEAD state is associated
> with loopback net_device and leads to loopback neighbour. It
> leads to an ethernet header with all zero addresses.
> 
> A very troubling case is working with mac80211 and ath9k.
> A packet with all zero source MAC address to mac80211 will
> eventually fail ieee80211_find_sta_by_ifaddr in ath9k (xmit.c).
> As result, ath9k flushes tx queue (ath_tx_complete_aggr) without
> updating baw (block ack window), damages baw logic and disables
> transmission.
> 
> Signed-off-by: Tong Zhu <zhutong@amazon.com>

Please repost with an appropriate Fixes: tag.

Thanks.