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: 8009e9f7ac4f ("set bat0 MTU according to the MTUs of the hard 
interfaces")
Signed-off-by: Sven Eckelmann <[email protected]>
---
 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 41c1ad33..ae5762af 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

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