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

On Mon, Jan 09, 2017 at 09:05:49AM +0100, Johannes Berg
wrote:
> On Sat, 2017-01-07 at 16:15 +0100, Linus L?ssing wrote:
> 
> > Actually, I do not quite understand that remark in the mac80211
> > multicast-to-unicast patch. IP should not care about the ethernet
> > header?
> 
> But it does, for example RFC 1122 states:
> 
> ?????????When a host sends a datagram to a link-layer broadcast address,
> ?????????the IP destination address MUST be a legal IP broadcast or IP
> ?????????multicast address.
> 
>  ????????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.

Any other examples?

> > ?????????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 :)

johannes