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authorTong Zhu <zhutong@amazon.com>2021-03-19 14:33:37 -0400
committerDavid S. Miller <davem@davemloft.net>2021-03-31 14:10:46 -0700
commitd47ec7a0a7271dda08932d6208e4ab65ab0c987c (patch)
tree77f87ea9b8f9e7ab159cbebb9633f9e22816a90d /net
parent61431a5907fc36d0738e9a547c7e1556349a03e9 (diff)
neighbour: Disregard DEAD dst in neigh_update
After a short network outage, the dst_entry is timed out and put in DST_OBSOLETE_DEAD. We are in this code because arp reply comes from this neighbour after network recovers. There is a potential race condition that dst_entry is still in DST_OBSOLETE_DEAD. With that, another neighbour lookup causes more harm than good. In best case all packets in arp_queue are lost. This is counterproductive to the original goal of finding a better path for those packets. I observed a worst case with 4.x kernel where a dst_entry in DST_OBSOLETE_DEAD state is associated with loopback net_device. It leads to an ethernet header with all zero addresses. A packet with all zero source MAC address is quite deadly with mac80211, ath9k and 802.11 block ack. It fails ieee80211_find_sta_by_ifaddr in ath9k (xmit.c). Ath9k flushes tx queue (ath_tx_complete_aggr). BAW (block ack window) is not updated. BAW logic is damaged and ath9k transmission is disabled. Signed-off-by: Tong Zhu <zhutong@amazon.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/core/neighbour.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index e2982b3970b8..8379719d1dce 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -1379,7 +1379,7 @@ static int __neigh_update(struct neighbour *neigh, const u8 *lladdr,
* 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;