Hi, Marek.
After network restart, wlan interfaces under bat0 are still deactivated. But it's not big problem. "/etc/init.d/batman-adv restart" makes them activated.
By removing interfaces entirely, i.e. network restart, batman purges the settings it had regarding these interfaces.
Ah, OK.
Note that OpenWRT allows to specify the MTU in the configuration files (/etc/config/network), so that you don't need to manually configure it each time you invoke "network restart".
Oh, thank you for your advice. I'll try it.
Thanks,
Kazuki Shimada