DHCP starvation because of GrapheneOS?

pizzapim

Today I encountered a weird problem with my network connection. I am not 100% sure the cause is GrapheneOS, but I am documenting this in case more people have the problem.

I woke up and my phone was continuously connecting to my WiFi AP and getting disconnected. So, I restarted it and it seemed to work again. However, after that another device could not get a DHCP lease anymore. I looked at the DHCP leases and they had all been given out at half past 2 in the night, when nobody was awake. What's more, they were requested by devices with seemingly random MAC addresses because their OUI did not correspond to any registered ones. At this point I could think of two causes: a problem with MAC address randomization of some device, or a prankster. I think the former is more plausible.

To my knowing, the only devices on my network that do MAC address randomization are some iOS devices and my Pixel 4a with GrapheneOS. I don't think it's likely iOS is at fault, or I would see this online more often but correct me if I'm wrong. So I concluded GrapheneOS might be at fault. Then I realized: maybe the behaviour in the morning of continuously reconnecting caused the DHCP starvation in the first place. Perhaps each time GrapheneOS would connect with the AP, it would do this with a random MAC address, request an IP and then disappear again.

For now, I released some DHCP leases manually and everything works again. Any comments are appreciated.

unwat

pizzapim

By default GrapheneOS connects to APs using a different MAC address each time, which could result in your phone taking up too many IP addresses. You can set it to one random MAC address specifically for your AP.

Settings > Network & internet > Internet > Saved networks > *your network* > Privacy > change to Use per-network randomized MAC.

No clue why your phone is connecting so many times, but this should fix the issue if it's your GOS phone.

aerosola

unwat Had an issue like that on my Pixel 7 with GOS some weeks ago now. After changing the MAC randomizer for my home network - I didn't have the issue anymore. The feature is primarly for unknown networks anyways - so I haven't changed the default mode. Only when a network doesn't like it.

pizzapim

unwat Thanks for the tip. If it happens again, I will probably investigate a bit more and afterwards change that setting.
memberberryfarms I don't think the size of the DHCP pool is a problem. We have this access point for years without any problems and we haven't introduced any new devices lately.
Shendai I don't think any neighbor of mine is knowledgeable in that area, but I thought about it. It stopped when I rebooted the access point so I don't think that's it.
aerosola Good to see I am not the only one. Agreed, you can just turn off the feature but it shouldn't really happen in the first place.

Leza89

unwat You can set it to one random MAC address specifically for your AP.

That's not directly but it solves my issue with my FTP-server running on Graphene. Thank you very much!

memberberryfarms

How many devices do you have on your network, how big is your DHCP pool and how long is your lease time? I'm wondering if the AP is hanging on to old leases for too long or not setting inactive leases to a backup state where they could be given out to new devices if an inactive lease is not in use but also not expired.

Shendai

Not to be paranoid needlessly, but depending on your network and your neighbors, this almost seems like a deauth wifi attack to get your devices to disconnect/reconnect in order to capture the packets of the 4-way handshake used in WPA/WPA2 type connections. They can then use tools like hashcat to try to decrypt your wifi password. Won't work if your wifi password is long, customized, and uses various special characters, but simple generic passwords are easily crackable.

If it continues every day/night at the same time, something else is likely going on as it shouldn't take repeated efforts to get the handshake.