4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Vasily Khoruzhick <vasil...@arista.com>

[ Upstream commit f0e0d04413fcce9bc76388839099aee93cd0d33b ]

Update 'confirmed' timestamp when ARP packet is received. It shouldn't
affect locktime logic and anyway entry can be confirmed by any higher-layer
protocol. Thus it makes sense to confirm it when ARP packet is received.

Fixes: 77d7123342dc ("neighbour: update neigh timestamps iff update is 
effective")
Signed-off-by: Vasily Khoruzhick <vasil...@arista.com>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 net/core/neighbour.c |   13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -1179,6 +1179,12 @@ int neigh_update(struct neighbour *neigh
                lladdr = neigh->ha;
        }
 
+       /* Update confirmed timestamp for neighbour entry after we
+        * received ARP packet even if it doesn't change IP to MAC binding.
+        */
+       if (new & NUD_CONNECTED)
+               neigh->confirmed = jiffies;
+
        /* If entry was valid and address is not changed,
           do not change entry state, if new one is STALE.
         */
@@ -1200,15 +1206,12 @@ int neigh_update(struct neighbour *neigh
                }
        }
 
-       /* Update timestamps only once we know we will make a change to the
+       /* Update timestamp only once we know we will make a change to the
         * neighbour entry. Otherwise we risk to move the locktime window with
         * noop updates and ignore relevant ARP updates.
         */
-       if (new != old || lladdr != neigh->ha) {
-               if (new & NUD_CONNECTED)
-                       neigh->confirmed = jiffies;
+       if (new != old || lladdr != neigh->ha)
                neigh->updated = jiffies;
-       }
 
        if (new != old) {
                neigh_del_timer(neigh);


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