Re: [PATCH RFC 00/24] IPVS: Add first IPv6 support to IPVS

To: "Simon Horman" <horms@xxxxxxxxxxxx>
Subject: Re: [PATCH RFC 00/24] IPVS: Add first IPv6 support to IPVS
Cc: "Sven Wegener" <sven.wegener@xxxxxxxxxxx>, "Graeme Fowler" <graeme@xxxxxxxxxxx>, netdev@xxxxxxxxxxxxxxx, lvs-devel@xxxxxxxxxxxxxxx, kaber@xxxxxxxxx, vbusam@xxxxxxxxxx
From: "Julius Volz" <juliusv@xxxxxxxxxx>
Date: Wed, 27 Aug 2008 17:24:53 +0200
On Wed, Aug 27, 2008 at 8:09 AM, Simon Horman <horms@xxxxxxxxxxxx> wrote:
> On Fri, Aug 22, 2008 at 02:14:11PM +0200, Julius Volz wrote:
>> On Fri, Aug 22, 2008 at 1:23 PM, Sven Wegener <sven.wegener@xxxxxxxxxxx> 
>> wrote:
>> >> He :) Imagine an old kernel on the backup receiving new messages and
>> >> not understanding them. How could we at least handle that situation
>> >> gracefully (without totally confusing the older kernel)? We'd need to
>> >> do it in a way that old features are still communicated in the same
>> >> way. E.g., v4-only connection syncs still use the same message format,
>> >> but once you use v6 entries, an unused flag or the 'reserved' field in
>> >> ip_vs_sync_conn is used. A v6 message would still confuse an older
>> >> kernel then, but a user would already notice that ipvsadm can't
>> >> configure the v6 services on the older kernel, so that's not too bad.
>> >
>> > If that's a problem, we can easily change the communication port and even
>> > completely redesign the protocol this way, without having old kernels
>> > getting confused about the data they get. We might lose the ability to
>> > sync between different versions, but in the end this is just the
>> > connection synchronziation and both systems should be running the same
>> > version. We could also keep the old communication port for some time, if
>> > that's really needed.
>> Yes, starting from scratch on another port sounds like a good idea.
>> Losing sync ability totally isn't as bad as confusing an older kernel
>> with new messages, so I hope it's not necessary to keep the old
>> baggage around?
> That does sound like a nice idea. I think that is important that we don't
> confuse older kernels. I guess the only time that ineroperability would be
> important is when upgrading kernels, where you might want to take the
> master ldirector down to upgrade it, then the standby.

Good, that makes two votes for not keeping the old protocol in parallel? ;)

>> Is there enough motivation for doing this though before having a
>> cleaned-up minimal v6 version without the sync daemon? This is where
>> I'm currently a bit stuck with... any help is appreciated :)
> IPv6 without sync is fine by me. Its certainly much better than no IPv6.
> Lets tackle sync a bit later.

Ok, going for cleaning up and reworking more of the current IPv6 code then...

Julius Volz
Corporate Operations - SysOps

Google Switzerland GmbH

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