netdev - Re: [PATCH net-next 2/3] ipv6: mld: do not overwrite uri when receiving an mldv2 query

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Date:	Thu, 25 Sep 2014 12:02:17 -0400
From:	David L Stevens <david.stevens@...cle.com>
To:	Daniel Borkmann <dborkman@...hat.com>, davem@...emloft.net
CC:	hannes@...essinduktion.org, netdev@...r.kernel.org
Subject: Re: [PATCH net-next 2/3] ipv6: mld: do not overwrite uri when receiving
 an mldv2 query

While I can see the case you're making, I think the intent of MRC is
violated by arbitrary URI.

> 5.1.3.  Maximum Response Code
> 
>    The Maximum Response Code field specifies the maximum time allowed
>    before sending a responding Report. 
>...
>    Small values of Maximum Response Delay allow MLDv2 routers to tune
>    the "leave latency" (the time between the moment the last node on a
>    link ceases to listen to a specific multicast address and the moment
>    the routing protocol is notified that there are no more listeners for
>    that address).  Larger values, especially in the exponential range,
>    allow the tuning of the burstiness of MLD traffic on a link.

If URI is larger than MRD, then a lost unsolicited report, or series,
specifically will *not* propagate changes throughout the network in less
than MRD*QRV, as intended.

It was an intentional design choice, not required or prohibited by RFC.

I'm not sure what problem you think it's causing, but if they are not
equal, I think at least the URI should be enforced to <= MRD. The querier,
IMO, should set these network-wide relevant parameters, not the individual
hosts.

Is there actually some bad effect from this?

						+-DLS

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