Re: [vserver] assigning less than /64 to individual guests

On Tue, May 17, 2011 at 01:10:40PM -0400, Michael Richardson wrote:
> 
> >>>>> "Eugen" == Eugen Leitl <[email protected]> writes:
>     Eugen> Just sent that to the vserver list, but figured this is at
>     Eugen> least as relevant.
> 
>     Eugen> So am I in the clear to parcel out a /64 in /80s, as long as
>     Eugen> all the /80 are all on the same LAN or VLAN? No autoconfig
>     Eugen> breakage ensues? Is 48 bits really enough for anybody?
> 
> If you are saying that you will allocate /80s to each vserver, but
> actually they will not be layer-2 isolated from each other, this is just
> an administrative partition, then I think it's a good idea.

The Linux vserver patch is a very lightweight virtualization. It doesn't 
share the network stack, shares the physical NIC MAC and only recently
were the vserver guests given 127.0.0.1 that is distinct from the
host's localhost -- as far as I known ::1 hasn't been given that
treatment yet.
 
> You can't use autoconfig for the parts that are in the /80s.
> You can arrange for your /80s to never overlap the autoconfigured stuff.
> OUI-64s, when generated from OUI-48s (i.e. mac addresses) always have
> ff:fe as the middle 16 bits. 

How much autoconfig do I need? Each physical host will be given a private
/64 (out of the /56 I have total), just the guests will be given an /80, 
allocated from a different /64.
 
> In addition, bit 6 in the OUI-64 (which is bit 1 in little bit-endian,
> the bit after the "broadcast" bit) will be set if the OUI-64 is believed
> to be globally unique.  Note that if you have IPv6 Privacy Extensions
> on, then autoconfig will not necessarily set bit 6.  
> I would have to lookup to determine in fact privacy extensions will set 
> the middle 16 bits in any predictable fashion.

I'm not really familiar with IPv6 advanced uses, at the moment I'm
treating it just like a bigger version of IPv4, at least as far as
guests are concerned. I don't really know what users would want to
run on their own /80s
 
> Permitting autoconfig to work seems like a nice thing to retain.

If the guests can all use the host's (different) /64, will that work?

-- 
Eugen* Leitl <a href="http://leitl.org">leitl</a> http://leitl.org
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