| Message ID | 20210319183327.GA25778@ucf43ac461c9a53.ant.amazon.com |
|---|---|
| State | New |
| Headers | show |
| Series | neighbour: Disregard DEAD dst in neigh_update | expand |
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;
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> --- net/core/neighbour.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)