Re: [PATCH] neighbour: Disregard DEAD dst in neigh_update

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.