If you are bridging 2+ wireless networks together, it can get tricky for the ARP mappings to take place efficiently throughout the network as you move around from AP to AP. I wrote a small shell script that runs on each router which reports in its WiFi-AP associations & DHCP entries that are part of the overall /20 network. This client mapping data is sent around to each router to determine who has the proper client and where/how to find them. I noticed that the relayd bridging app was putting in ARP entries that were becoming stale/incorrect over time as you moved around so I modified it’s source code to outsource this work to a file that has an updated master set of static interface entries based on each DHCP/WIFI association for each router on the network.
(I lost access to my fossjon github account due to 2-factor auth being lost)
(the steps to compile this on a armv7l router itself are in the README I added)
For example, a shell script running on the router (with all the relevant network information) can determine and write out a small mapping file that this modified framework can use to keep a cleaner and better ARP tableset (/tmp/arp.txt):
wlan1 00:2b:3d:5a:4a:9e 192.168.18.103
The added capability in relayd will then ensure that for any of the bridged interfaces listed, the only ARP entry that will exist is for the one specified in the file and that it will be set to permanent status instead (deletion of incorrect entries added in).
I am running this as a test on my parents home network to see how long it lasts for, modifying C is tricky for me! 🙂