From: Sven Eckelmann <sven@narfation.org>

If an interface changes the MTU, it is expected that an NETDEV_PRECHANGEMTU
and NETDEV_CHANGEMTU notification events is triggered. This worked fine for
.ndo_change_mtu based changes because core networking code took care of it.
But for auto-adjustments after hard-interfaces changes, these events were
simply missing.

Due to this problem, non-batman-adv components weren't aware of MTU changes
and thus couldn't perform their own tasks correctly.

Fixes: c6c8fea29769 ("net: Add batman-adv meshing protocol")
Cc: stable@vger.kernel.org
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
---
 net/batman-adv/hard-interface.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/batman-adv/hard-interface.c b/net/batman-adv/hard-interface.c
index 41c1ad33d009..ae5762af0146 100644
--- a/net/batman-adv/hard-interface.c
+++ b/net/batman-adv/hard-interface.c

@@ -630,7 +630,7 @@ int batadv_hardif_min_mtu(struct net_device *soft_iface)
  */
 void batadv_update_min_mtu(struct net_device *soft_iface)
 {
-	soft_iface->mtu = batadv_hardif_min_mtu(soft_iface);
+	dev_set_mtu(soft_iface, batadv_hardif_min_mtu(soft_iface));
 
 	/* Check if the local translate table should be cleaned up to match a
 	 * new (and smaller) MTU.

-- 
2.39.2