Linux Ethernet Bridging - Jan 2017 - [Bridge] [PATCH net-next] bridge: multicast to unicast

On Mon, 2017-01-09 at 12:44 +0100, M. Braun wrote:
> Am 09.01.2017 um 09:08 schrieb Johannes Berg:
> > Does it make sense to implement the two in separate layers though?
> > 
> > Clearly, this part needs to be implemented in the bridge layer due
> > to
> > the snooping knowledge, but the code is very similar to what
> > mac80211
> > has now.
> 
> Does the bridge always know about all stations connected?
> 
> That is bridge fdb entries (need to) expire so the bridge might
> "forget" a still-connected station not sending but only consuming
> broadcast traffic.
> 
> E.g. there is a television broadcast station here that receives a
> video stream (via wifi, udp packets) and then airs it (dvb-t) but (on
> its own) would not send any data packet on wifi (static ip, etc.).
Ok, that I don't know. Somehow if you address a unicast packet there
the bridge has to make a decision - so it really should know? Would it
query the port somehow to see if the device is behind it, if getting a
packet for a station it forgot about?
> An other reason to implement this in mac80211 initially was that
> mac80211 could encapsulate broacast/multicast ethernet packtes in
> unicast A-MSDU packets in a way, so that the receiver would still see
> process ethernet packets (after conversion) but have unicast wifi
> frames. This cannot be done in bridge easily but one might want to
> add this later to mac80211.
Yes, DMG would have to be done in mac80211, but that's a lot clearer
case too since it requires negotiation functionality etc.

johannes

Am 09.01.2017 13:15, schrieb Johannes Berg:
>> That is bridge fdb entries (need to) expire so the bridge might
>> "forget" a still-connected station not sending but only
consuming
>> broadcast traffic.
> 
> Ok, that I don't know. Somehow if you address a unicast packet there
> the bridge has to make a decision - so it really should know?
If the bridge has not learned the unicast destination mac address on any 
port, it will flood the packet on all ports except the port it received 
the packet on.

Regards,
M. Braun