Hacked MAAS ether_wake.template to allow to power on / off over WOL in the case the cluster controller has multiple interfaces

ether_wake.template

# -*- mode: shell-script -*-
#
# Control node power through WOL, via `wakeonlan` or `etherwake`.
#

mac_address={{mac_address}}
power_change={{power_change}}
ip_address={{node_ip_address}}

#if [ -n "${ip_address}" ]
#then
#    iface="$( ip route show to match "{{ip_address}}" | sed -n '/^default/! s/^.* dev \([^ ]*\).*$/\1/p' )"
#    local_broadcast="$( ip addr show dev "${iface}" | sed -n '/^[[:space:]]*inet/ s/^.* brd \([^ ]*\) .*$/\1/p' )"
#fi

echo "${power_change} ${ip_address} ${mac_address}" >> /tmp/power 
if [ "${power_change}" != 'on' ]
then
    #echo "There is no way to power down a node through etherwake." >&2
    #exit 1
    if [ -n "${ip_address}" ]
    then
        #ssh -vv -i /etc/maas/stack-access-key -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no ubuntu@${ip_address} -C "echo 'sleep 2 && sudo /sbin/poweroff -f' | at now" >> /tmp/power 2>&1
        ssh -i /etc/maas/stack-access-key -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no ubuntu@${ip_address} -C "echo 'sleep 2 && sudo /sbin/poweroff -f' | at now"
    else
       echo "Unable to power down a node using etherwake without ip address." >&2
       exit 1
    fi
elif [ -x /usr/bin/wakeonlan ]
then
    /usr/bin/wakeonlan -i "192.168.0.255" $mac_address
    #if [ -n "${local_broadcast}" ]
    #then
    #    /usr/bin/wakeonlan -i "${local_broadcast}" $mac_address
    #else
    #    /usr/bin/wakeonlan $mac_address
    #fi
elif [ -x /usr/sbin/etherwake ]
then
    if [ -n "${iface}" ]
    then
        /usr/sbin/etherwake -i "${iface}" $mac_address
    else
        /usr/sbin/etherwake $mac_address
    fi
else
    echo "No wakeonlan or etherwake program found." >&2
fi

exit 0

What version of MAAS is this for? I'm running the recent PPA version of MAAS, and I get an oops ip_address not defined. But just looking around, couldn't we use arp to assign an IP address if we fail to get node_ip_address, as a fail safe? I'm new to MAAS, and this would be just great to get working and fault tolerant, as half my nodes are desktops ;) Nice script hacking!

I think it is just ip_address={{ip_address}}