We need to initialize the fallback device to have a correct mtu
set on this device. Otherwise the mtu is set to null and the device
is unusable.
Fixes: fd58156e456d ("IPIP: Use ip-tunneling code.")
Cc: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
         */
        if (!IS_ERR(itn->fb_tunnel_dev)) {
                itn->fb_tunnel_dev->features |= NETIF_F_NETNS_LOCAL;
+               itn->fb_tunnel_dev->mtu = ip_tunnel_bind_dev(itn->fb_tunnel_dev);
                ip_tunnel_add(itn, netdev_priv(itn->fb_tunnel_dev));
        }
        rtnl_unlock();