How to prevent DHCP traffic from being forwarded on 802.11s mesh?

Installing and Using OpenWrt Network and Wireless Configuration
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I have an 802.11s mesh consisting of six Netgear WNDR* routers. It works perfectly most of the time. Sometimes (once a month or so, though I don't think the frequency is relevant) two (random) mesh devices start stepping over each other for a DHCP lease. My hypothesis:

  • Meshpoint A requests DHCP address but the DHCPDISCOVER message passes through meshpoint B before reaching the main DHCP server on main router R.
  • Router R assigns some address to meshpoint B's MAC (whether it's configured statically or not doesn't matter).
  • Things break all over the place

This obviously depends on whether the client is cetting CHADDR correctly and if dnsmasq is honoring it appropriately. Still, is there a way to simply skip DHCP traffic from being forwarded over 802.11s? If not, I'll dig deeper and try to capture the DHCP packets.