On Tue, Feb 23, 2021 at 07:37:53PM +0200, Vladimir Oltean wrote: > Hi, > > I have udhcpcd in my system and this is configured to bring interfaces > up as soon as they are created. > > I create a bridge as follows: > > ip link add br0 type bridge > > As soon as I create the bridge and udhcpcd brings it up, I have some > other crap (avahi) that starts sending some random IPv6 packets to > advertise some local services, and from there, the br0 bridge joins the > following IPv6 groups: > > 33:33:ff:6d:c1:9c vid 0 > 33:33:00:00:00:6a vid 0 > 33:33:00:00:00:fb vid 0 > > br_dev_xmit > -> br_multicast_rcv > -> br_ip6_multicast_add_group > -> __br_multicast_add_group > -> br_multicast_host_join > -> br_mdb_notify > > This is all fine, but inside br_mdb_notify we have br_mdb_switchdev_host > hooked up, and switchdev will attempt to offload the host joined groups > to an empty list of ports. Of course nobody offloads them. > > Then when we add a port to br0: > > ip link set swp0 master br0 > > the bridge doesn't replay the host-joined MDB entries from br_add_if -> > new_nbp -> br_multicast_add_port (should it?), and eventually the host > joined addresses expire, and a switchdev notification for deleting it is > emitted, but surprise, the original addition was already completely missed. > > What to do?
For route offload you get a dump of all the existing routes when you register your notifier. It's a bit different with bridge because you don't care about existing bridges when you just initialize your driver. We had a similar issue with VXLAN because its FDB can be populated and only then attached to a bridge that you offload. Check vxlan_fdb_replay(). Probably need to introduce something similar for FDB/MDB entries.
