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 --- net/core/neighbour.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/core/neighbour.c b/net/core/neighbour.c index 6e890f51b7d8..e471c32e448f 100644 --- a/net/core/neighbour.c +++ b/net/core/neighbour.c @@ -1271,7 +1271,7 @@ int neigh_update(struct neighbour *neigh, const u8 *lladdr, u8 new, * we can reinject the packet there. */ n2 = NULL; - if (dst) { + if (dst && dst->obsolete != DST_OBSOLETE_DEAD) { n2 = dst_neigh_lookup_skb(dst, skb); if (n2) n1 = n2;