Re: [PATCH net-next] bridge: multicast to unicast
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.). 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. Michael
Re: [PATCH net-next] bridge: multicast to unicast
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.). 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. Michael
Re: [PATCH net-next] bridge: multicast to unicast
Am 06.01.2017 um 14:54 schrieb Johannes Berg: > >> The bridge layer can use IGMP snooping to ensure that the multicast >> stream is only transmitted to clients that are actually a member of >> the group. Can the mac80211 feature do the same? > > No, it'll convert the packet for all clients that are behind that > netdev. But that's an argument for dropping the mac80211 feature, which > hasn't been merged upstream yet, no? But there is multicast/broadcast traffic like e.g. ARP and some IP multicast groups that are not covered by IGMP snooping. The mac80211 patch converts this to unicast as well, which the bridge cannot do. That way, these features both complement and overlap each other. Regards, Michael
Re: [PATCH net-next] bridge: multicast to unicast
Am 06.01.2017 um 14:54 schrieb Johannes Berg: > >> The bridge layer can use IGMP snooping to ensure that the multicast >> stream is only transmitted to clients that are actually a member of >> the group. Can the mac80211 feature do the same? > > No, it'll convert the packet for all clients that are behind that > netdev. But that's an argument for dropping the mac80211 feature, which > hasn't been merged upstream yet, no? But there is multicast/broadcast traffic like e.g. ARP and some IP multicast groups that are not covered by IGMP snooping. The mac80211 patch converts this to unicast as well, which the bridge cannot do. That way, these features both complement and overlap each other. Regards, Michael
