On 2017-01-06 13:47, Johannes Berg wrote: > On Mon, 2017-01-02 at 20:32 +0100, Linus Lüssing wrote: >> Implements an optional, per bridge port flag and feature to deliver >> multicast packets to any host on the according port via unicast >> individually. This is done by copying the packet per host and >> changing the multicast destination MAC to a unicast one accordingly. > > How does this compare and/or relate to the multicast-to-unicast feature > we were going to add to the wifi stack, particularly mac80211? Do we > perhaps not need that feature at all, if bridging will have it? > > I suppose that the feature there could apply also to locally generated > traffic when the AP interface isn't in a bridge, but I think I could > live with requiring the AP to be put into a bridge to achieve a similar > configuration? > > Additionally, on an unrelated note, this seems to apply generically to > all kinds of frames, losing information by replacing the address. > Shouldn't it have similar limitations as the wifi stack feature has > then, like only applying to ARP, IPv4, IPv6 and not general protocols? > > Also, it should probably come with the same caveat as we documented for > the wifi feature: > > Note that this may break certain expectations of the receiver, > such as the ability to drop unicast IP packets received within > multicast L2 frames, or the ability to not send ICMP destination > unreachable messages for packets received in L2 multicast (which > is required, but the receiver can't tell the difference if this > new option is enabled.) > > > I'll hold off sending my tree in until we see that we really need both > features, or decide that we want the wifi feature *instead* of the > bridge feature. 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? - Felix
