OpenWRT workaround for inability to set MTU for WLAN interfaces

01-maxwlanmtu

#!/bin/sh

# Ensure that WLAN interface MTU is set to the maximum
# permitted value to prevent issues when attached to a
# bridge with jumbo MTU.
#
# Do not attempt to use standard UCI configuration
# in /etc/config/network and set the MTU with a config
# of type interface. It does not work consistently
# and in the best case works for the first WLAN
# interface in each respective radio that starts up
# only.
#
# NOTE: if you set the MTU via Luci it will work immediately
# after config is set, but after that it will not work.
# Do not let this deceive you, make sure to test that
# it works properly after WiFi restart and system reboot
# before getting rid of this hotplug script.
#
# To quickly install this do:
#   wget -O /etc/hotplug.d/net/01-maxwlanmtu https://gist.github.com/rany2/3b0a4c225977813a8847a89358e2f4de/raw/01-maxwlanmtu
#   echo /etc/hotplug.d/net/01-maxwlanmtu >> /etc/sysupgrade.conf

if [ "$DEVTYPE" = wlan ] && [ "$ACTION" = add ]
then
	ip link set $INTERFACE mtu 2304
fi

wget -O /etc/hotplug.d/net/01-maxwlanmtu https://gist.github.com/rany2/3b0a4c225977813a8847a89358e2f4de/raw/01-maxwlanmtu
echo /etc/hotplug.d/net/01-maxwlanmtu >> /etc/sysupgrade.conf