How to give stable MAC address to batman-adv device?

Hi,

I'm trying to use batman-adv to fix wifi signal problems with a few Raspberry Pis.  So far it's more-or-less working.  I'm using dnsmasq on the main gateway node to serve IP addresses over DHCP.

One problem I have is that the bat0 device has a different MAC address each time it starts.  My Raspbery Pis reboot each day on a cron job and each time they get a new MAC.  This causes dnsmasq to give them a new IP address.  This causes problems talking to other nodes with outdated DNS caches, as well as being irritating when I try to use ssh and it thinks the nodes are "impersonating" each other.

Is there a way to force batman-adv to use a stable MAC address?

Thanks, Matthew Exon