netdev - Re: [PATCH net 1/2] ipv4: igmp: use alarmtimer to prevent delayed reports

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Date:   Thu, 14 Jun 2018 18:44:15 +0530
From:   Tejaswi Tanikella <tejaswit@...eaurora.org>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     netdev@...r.kernel.org, f.fainelli@...il.com, davem@...emloft.net
Subject: Re: [PATCH net 1/2] ipv4: igmp: use alarmtimer to prevent delayed
 reports

On Wed, Jun 13, 2018 at 04:44:37PM +0200, Andrew Lunn wrote:
> While it has been asleep, it has also been dropping any multicast
> traffic in the stream. So it does not really matter it has left the
> group. You were not receiving the packets anyway.
> 
> Thing about this from another angle. I have an NTP client running on
> my laptop, using multicast address 224.0.1.1. I suspend my laptop and
> walk away for two hours. When i come back, i find that 20 seconds
> after i suspended it, it resumed and send an group response
> message. And an hour later, since it was still running, the battery
> went flat.
> 
> It seems to me, the change you are proposing cannot be the default
> behaviour.
> 
> I actually think you need to be looking at some sort of WoL feature.
> You need the multicast stream data packets to wake you, and you also
> need to wake up the IGMP query message. And you need to wake up to
> send the group membership. Does your hardware have this sort of WoL
> support? You can then explicitly enable this WoL for your application.
> 
> 	Andrew

Thanks Andrew.
You are right, this should not be the default behaviour.

-Tejaswi