tree e0f06b0072608a1a55800a50e5dab17526fdc9d5
parent f87d8ad9233f115db92c6c087d58403b0009ed36
author JianJhen Chen <kchen@synology.com> 1546745293 +0800
committer David S. Miller <davem@davemloft.net> 1546880942 -0500

net: bridge: fix a bug on using a neighbour cache entry without checking its state

When handling DNAT'ed packets on a bridge device, the neighbour cache entry
from lookup was used without checking its state. It means that a cache entry
in the NUD_STALE state will be used directly instead of entering the NUD_DELAY
state to confirm the reachability of the neighbor.

This problem becomes worse after commit 2724680bceee ("neigh: Keep neighbour
cache entries if number of them is small enough."), since all neighbour cache
entries in the NUD_STALE state will be kept in the neighbour table as long as
the number of cache entries does not exceed the value specified in gc_thresh1.

This commit validates the state of a neighbour cache entry before using
the entry.

Signed-off-by: JianJhen Chen <kchen@synology.com>
Reviewed-by: JinLin Chen <jlchen@synology.com>
Signed-off-by: David S. Miller <davem@davemloft.net>