Re: [pim] [Mcast-wifi] Issues with MLD and Android powersaving / sleep mode...

Mark Smith <> Tue, 24 March 2020 21:40 UTC

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From: Mark Smith <>
Date: Wed, 25 Mar 2020 08:40:09 +1100
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To: Linus Lüssing <>
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Subject: Re: [pim] [Mcast-wifi] Issues with MLD and Android powersaving / sleep mode...
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On Wed, 25 Mar 2020 at 07:54, Linus Lüssing <> wrote:
> Hi,
> With Freifunk [0] we lately came across an annoying issue with Android
> devices... which I'm not really sure how to solve yet...
> It seems that (some?) Android devices do not respond to MLD
> queries when in sleep mode:

If the device is asleep, effectively offline, why should it respond to
MLD queries?

When I'm asleep I have to wake up or be woken up before I respond to
queries too.

Times by a billion devices, responding to MLD queries while the device
is asleep and not in use is going to be wasting a lot of electricity.

> Which causes severe IPv6 connectivity/usability issues
> when trying to use MLD snooping capabilities.
> As soon as you turn on the screen of the Android device or
> connect a charger MLD Reports arrive just fine.

>From the above github link, it sounds like the real fault is that when
Android wakes up it isn't immediately issuing MLD joins for its
existing IPv6 addresses. I'll have to think about which IPv6 RFC
advice to do that is probably in, however I think it should be - every
time an interface comes up with existing IPv6 addresses, it should be
sending MLD Reports to join the Solicited Node Multicast groups for
its addresses.


> My test results
> were, as noted in the Android ticket:
> Results with phone on battery:
> * 0/8 MLD Reports received
> * 3/8 Neighbor Advertisements received
> * 8/8 Echo Replies received
> Results with phone on charger:
> * 8/8 MLD Reports received
> * 8/8 Neighbor Advertisements received
> * 8/8 Echo Replies received
> Fixing this on the Android devices would need several years to
> propagate, as noted by an Android dev.
> Has anyone on this list experienced similar issues, too? And is
> there maybe even someone who came up with a workaround that they
> implemented on the router/switch side?
> If not and if we can't come up with a solution it looks pretty
> gloomy for (non-flooding) multicast in wifi networks to me for
> the next years...
> Regards, Linus
> [0]:
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> Mcast-wifi mailing list