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

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Date:   Tue, 12 Jun 2018 18:28:18 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Tejaswi Tanikella <tejaswit@...eaurora.org>
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 Mon, Jun 11, 2018 at 05:21:05PM +0530, Tejaswi Tanikella wrote:
> On receiving a IGMPv2/v3 query, based on max_delay set in the header a
> timer is started to send out a response after a random time within
> max_delay. If the system then moves into suspend state, Report is
> delayed until system wakes up.
> 
> Use a alarmtimer instead of using a timer. Alarmtimer will wake the
> system up from suspend to send out the IGMP report.

Hi Tejaswi

I think i must be missing something here. If we are suspended, we are
not receiving multicast frames. If we are not receiving frames, why do
we need to reply to the query?

Once we resume, i expect we will reply to the next query. You could
optimise restarting the flow by immediately sending a membership
report, same as when the setsockopt is used to join the group.

	Andrew