On Mon, Jan 09, 2017 at 10:42:46PM +0100, Johannes Berg wrote: > On Mon, 2017-01-09 at 22:33 +0100, Linus Lüssing wrote: > > On Mon, Jan 09, 2017 at 01:44:03PM +0100, Johannes Berg wrote: > > > > > > > > A host SHOULD silently discard a datagram that is > > > > > received via > > > > > a link-layer broadcast (see Section 2.4) but does not > > > > > specify > > > > > an IP multicast or broadcast destination address. > > > > > > > > This example is the other way round. It specifies how the IP > > > > destination should look like in case of link-layer broadcast. Not > > > > how the link-layer destination should look like in case of a > > > > multicast/broadcast IP destination. > > > > > > You stopped reading too early - snipped the context part for you :) > > > > Sorry for writing to you directly, but I still have some > > difficulties. In pseudo-code that line says: > > > > ----- > > if ll_dst(pkt) == bcast AND ip_dst(pkt) != mcast/bcast: > > -> drop(pkt) > > ----- > > > > But after multicast-to-unicast conversion, we have: > > > > ----- > > ll_dst(pkt) == ucast AND ip_dst(pkt) == mcast > > ----- > > > > So none of the two requirements for dropping are matched? > > > > Exactly. My point is that this is breaking the expectation that hosts > are actually able to drop such packets. [readding CCs I removed earlier] Ah! Thanks. I was worried about creating packetloss :D. Hm, for this other other way round, I think it does not apply for the bridge multicast-to-unicast patch if I'm not misreading the bridge code: For a packet with a link-layer multicast address but a unicast IP destination, the bridge MDB lookup will fail. (http://lxr.free-electrons.com/source/net/bridge/br_multicast.c?v=4.8#L178 returns NULL) Case A): No multicast router on port: -> bridge, br_multicast_flood(), will drop the packet already (no matter if multicast-to-unicast is enabled or not) Case B): Multicast router present on port: -> The new patch does not apply multicast-to-unicast but just floods packet unaltered ("else { port = rport; addr = NULL; }" branch) Regards, Linus
