On Monday, September 14, 2020 9:53:46 PM CEST Linus Lüssing wrote:
Scenario:
- Multicast frame send from mesh to a BLA backbone (multiple nodes with their bat0 bridged together, with BLA enabled)
Issue:
- BLA backbone nodes receive the frame multiple times on bat0, once from mesh->bat0 and once from each backbone_gw from LAN
For unicast, a node will send only to the best backbone gateway according to the TQ. However for multicast we currently cannot determine if multiple destination nodes share the same backbone if they don't share the same backbone with us. So we need to keep sending the unicasts to all backbone gateways and let the backbone gateways decide which one will forward the frame. We can use the CLAIM mechanism to make this decision.
One catch: The batman-adv gateway feature for DHCP packets potentially sends multicast packets in the same batman-adv unicast header as the multicast optimizations code. And we are not allowed to drop those even if we did not claim the source address of the sender, as for such packets there is only this one multicast-in-unicast packet.
How can we distinguish the two cases?
The gateway feature uses a batman-adv unicast 4 address header. While the multicast-to-unicasts feature uses a simple, 3 address batman-adv unicast header. So let's use this to distinguish.
Fixes: e32470167379 ("batman-adv: check incoming packet type for bla") Signed-off-by: Linus Lüssing linus.luessing@c0d3.blue
Acked-by: Simon Wunderlich sw@simonwunderlich.de