On Thu, Sep 15, 2016 at 08:58:50PM +0200, John Crispin wrote: > Hi, > > While adding MDB support to the qca8k dsa driver I found that ipv4 mcast > groups don't always get propagated to the dsa driver. In my setup there > are 2 clients connected to the switch, both running a mdns client. The > .port_mdb_add() callback is properly called for 33:33:00:00:00:FB but > 01:00:5E:00:00:FB never got propagated to the dsa driver. > > The reason is that the call to ipv4_is_local_multicast() here [1] will > return true and the notifier is never called. Is this intentional or is > there something missing in the code ?
I believe this is based on RFC 4541: "Packets with a destination IP (DIP) address in the 224.0.0.X range which are not IGMP must be forwarded on all ports." https://tools.ietf.org/html/rfc4541 But, we are missing the offloading of router ports, which is needed for the device to correctly flood unregistered multicast packets. That's also according to the mentioned RFC: "If a switch receives an unregistered packet, it must forward that packet on all ports to which an IGMP router is attached." Implemented at br_flood_multicast() However, the marking is done per-port and not per-{port, VID}. We need that in case vlan filtering is enabled. I think Nik is working on that, but he can correct me if I'm wrong :). The switchdev bits can be added soon after. > > John > > [1] > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/net/bridge/br_multicast.c?id=refs/tags/v4.8-rc6#n737
