Hi there,
I am seeing odd kernel crashes when using batman-adv over VXLAN. This is in a Freifunk environment on our VPN gateway side where clients connect using L2TPv3 tunnels and the gateways are interconnected using VXLAN.
The setup is as follows on both ends:
- Both machines are Hetzner Cloud VMs (CX11) - OS: Fedora 36 (Pre-release) / Kernel 5.17.2-300.fc36.x86_64 - batctl 2022.0 [batman-adv: 2022.0] (using mainline module provided by - the distro's kernel-modules-extras package) - VXLAN on UDP going out through the WAN connection to the other machines - VXLAN FDB using unicast with static flooding (00:00:00:00:00:00 MAC entries with dst configured) - VXLAN connectivity is confirmed to be working between all connected gateways using IP and ICMP - batctl if add <vxlan-interface> - There is also another bridge attached to the batman-adv interface that bundles all the L2TPv3 tunnels. It has bridge port isolation enabled to prevent the nodes from believing that they are connected to each other on the same L2 network.
The mesh is a fairly busy mesh with ~150 nodes and 250-350 client devices at any given time. We currently use 4 gateways (instances with batman-adv in gateway mode).
So far I have been able to figure out the follwing: - The issue usually happens within 1-2 minutes of a certain(?) client connecting to the machine using a L2TPv3 tunnel - The issue does not manifest itself when using GRETAP interfaces between the gateway machines in matching pairs on either side of the link and those GRETAP interfaces being added to the batman-adv interface - The number of gateways interconnected using VXLAN does not matter. N-1 machines will crash with this issue and the crashes are rolling in nature, disabling all gateways but one within the N*1-2 minute timeframe. - I remember fighting this issue way back in the past (I think it was around 2017), so this issue has been there for a while in our setup.
I have attached a kdump dmesg log that has the panic message. A vmcore file is available for kernel-5.17.2-300.fc36.x86_64, which I can provide if needed. It is 77MB.
Thanks, Felix