[OpenWrt-Devel] Regarding bridge multicast-to-unicast patch

Steven Barth cyrus at openwrt.org
Fri Sep 12 02:55:17 EDT 2014

Am 12.09.2014 um 03:48 schrieb Linus Lüssing:
>> Another idea would maybe be to translate MLDv1 / IGMPv2 reports into
>> appropriate MLDv2/IGMPv3 equivalents before sharing them on the
>> bridge to prevent the suppression.
> Hm, IGMPv2/MLDv1 to IGMPv3/MLDv2 should be relatively easy. But
> I'm currently not sure whether a router/querier will make and take
> some wrong assumptions and actions by thinking there is no
> IGMPv2/MLDv1 listener. What if there is one MLDv2 listener which
> included source specific state messages in its state change report?
> The querier would respond with a "Multicast Address and Source
> Specific Query" to learn whether there are listeners left for
> this multicast and source addresses. Would the MLDv1 listener
> interpret this query and process this message as a "Multicast Address
> Specific Query" or would it ignore it?
It doesn't really matter since sending / receiving 
address-and-source-specific queries doesn't reduce the filter timer of 
the group but only the source timers of the sources included in the query.

> What about the many MLDv1 queriers we have right now through the
> bridge code? What if someone sneaks in an MLDv1 listener somewhere
> in your bridged network over an ethernet cable? (You'd need
> report translation both on the AP and on bridges and maybe query
> translation, too)
Ah so the bridge code is actually a dumb v1-querier. Hmm that is 
problematic then I suppose. But doesn't that effectively downgrade the 
whole link to MLDv1 even if you potentially have a v2 querier at hand? 
Sounds very fishy to me.


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