Batman-adv bat0 mtu

Installing and Using OpenWrt Network and Wireless Configuration
#1

I'm using batman-adv on a multilink (eth/wifi) network, and I cannot set MTU to 1532 on all interfaces.
One way to avoid fragmentation is to set bat0 MTU to 1468.
I tried setting mtu in /etc/config/network, but I can't seem to find the right place to set it.

using

config interface 'bat0'
    option proto 'none'
    option ifname 'bat0'
    option mtu '1468'

is not solving the problem.

#2

Which version of batman-adv? Config was changed early this year to a hard interface structure.

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#3 
$ batctl  -v
batctl openwrt-2018.1-1 [batman-adv: openwrt-2018.1-8]

cat /etc/openwrt_release 
DISTRIB_ID='OpenWrt'
DISTRIB_RELEASE='18.06.4'
DISTRIB_REVISION='r7808-ef686b7292'
DISTRIB_TARGET='ar71xx/generic'
DISTRIB_ARCH='mips_24kc'
DISTRIB_DESCRIPTION='OpenWrt 18.06.4 r7808-ef686b7292'
DISTRIB_TAINTS=''
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#4

That is the older version and the last revision of the wiki page describing that configuration is https://openwrt.org/docs/guide-user/network/wifi/mesh/batman?rev=1555021785

Unfortunately, "default" naming of interfaces can be confusing, as there can be "reuse" of the same name and that the physical interface and the batman-adv portal interface were challenging to unwind from each other.

From that linked page (as my memory of the older config style is very dusty), it shows

config interface 'nwi_mesh0'
        option ifname 'mesh0'
        option proto 'batadv'
        option mesh 'bat0'
#       option routing_algo 'BATMAN_V'
        option mtu '2304'
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#5

I believe the configuration stanza you're referring to is setting MTU for mesh0 inteface, which is the physical interface.
What I wanted was to lower MTU for virtual interface bat0 to 1468 so that it would fit in a 1500 byte ethernet packet

#6

That could well be -- it took me several days to wrap my head around the older config scheme!

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