[PATCH v3] neighbour: confirm neigh entries when ARP packet is received

[Vasily Khoruzhick <vasilykh@arista.com>]

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: 77d7123342 ("neighbour: update neigh timestamps iff update is effective")
Signed-off-by: Vasily Khoruzhick <vasilykh@arista.com>
---
v2: - update comment to match new code.
v3: - fix wording in commit message, make 'Fixes' tag one line, remove extra new line
      between 'Fixes' and 'Signed-off-by'.

 net/core/neighbour.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index aa19d86937af..91592fceeaad 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -1180,6 +1180,12 @@ int neigh_update(struct neighbour *neigh, const u8 *lladdr, u8 new,
 		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.
 	 */
@@ -1201,15 +1207,12 @@ int neigh_update(struct neighbour *neigh, const u8 *lladdr, u8 new,
 		}
 	}
 
-	/* 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);
-- 
2.18.0