netdev - Premature timeout for MLDv1 Host compatibility mode?

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Message-ID: <CAOLNa-dCpLG4XCarzbSb=ptu-KGVX_Fghv4Z_CDQ8HBF_n-rGQ@mail.gmail.com>
Date:	Thu, 26 Jul 2012 16:57:43 +0200
From:	Dragos Ilie <dragos.ilie@...il.com>
To:	netdev@...r.kernel.org
Subject: Premature timeout for MLDv1 Host compatibility mode?

Hi!

I suspect that the MLDv1 Host compatibility mode is ended prematurely.
In net/ipv6/mcast.c the "Older Version Querier Present" timeout is
computed as

max_delay = (ntohs(mld->mld_maxdelay)*HZ)/1000;
switchback = (idev->mc_qrv + 1) * max_delay;
idev->mc_v1_seen = jiffies + switchback;

RFC 3810 says that the timeout should be computed as
Robustness_Variable * Query_Interval + Query_Response_Interval. This
suggests that the line where switchback is computed should be changed
to something like

switchback = (idev->mc_qrv * 125 * HZ)  + max_delay;

where 125 is the default Query_Interval in seconds

I would appreciate it if somebody can confirm if my suspicion is correct.

Regards,
Dragos
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