maas-devel team mailing list archive

[Gavin Panella <gavin.panella@xxxxxxxxxxxxx>]

On 2 May 2014 14:42, Andres Rodriguez <andres.rodriguez@xxxxxxxxxxxxx> wrote:
>
>
>
> On Thu, May 1, 2014 at 5:05 PM, Gavin Panella <gavin.panella@xxxxxxxxxxxxx>
> wrote:
>>
>> With reference to bug 1314267 [1] and bug 1274499 [2], we have a problem
>> where ISC DHCPD, when running low on unused addresses, hands out IPs
>> that are marked as reserved for a different host, or addresses that
>> appear to already be in use.
>>
>> We've discussed allocating a smaller window of a cluster's overall
>> network range to dynamic allocation, but this is somewhat complex, and
>> can be swamped by, for example, LXC containers using DHCP to obtain IP
>> addresses for their bridged interfaces.
>>
>> However, each cluster is meant to be on its own layer-2 subnet, so every
>> cluster could reasonably hand out link local addresses [3] from a (very
>> large) dynamic pool (and every cluster could use the same range, because
>> they're link-local and won't overlap). With some changes to MAAS [4]
>> this would be sufficient for enlistment and commissioning.
>>
>> Then, when a machine is allocated to a user, an address can be chosen
>> from the cluster's configured network, and assigned statically to the
>> node by MAAS. This could be configured during node installation, or
>> added as a static host entry to the DHCP server (as now, except outside
>> of the dynamic pool), or both.
>
>
> Why not making the static the addresses that have already been assigned
> during enlistment/commissioning ? It seems to me that when the commissioning
> process happens, the node already know what's its IP address. Why not making
> an static mapping at that stage?

That's what happens now. However, it seems that dhcpd treats static
assignments within a dynamic range as advisory only, and will give
them out when it runs low of free addresses.

>>
>>
>> LXC containers would come up and obtain link-local addresses, which is
>> not going to be terribly useful. MAAS would have to provide an API by
>> which a node could obtain additional IP addresses. Juju, for example,
>> would be forced to obtain new IP addresses from MAAS when creating new
>> containers. [5]
>>
>> What do you think?
>>
>>
>> [1] MAAS dhcpd will re-issue leases for nodes
>> <https://bugs.launchpad.net/maas/+bug/1314267>
>>
>> [2] (dhcp lease rollover causes loss of access to managment IP
>> <https://bugs.launchpad.net/ubuntu/+source/maas/+bug/1274499>
>>
>> [3] http://en.wikipedia.org/wiki/Link-local_address
>>
>> [4] Nodes are given a URL that points back to the region from which to
>> obtain their preseed, and they report commissioning results direct to
>> the region too. These would have to change to either be proxied via or
>> handled by the cluster.
>>
>> [5] This API could be extended so that a user could obtain IP addresses
>> for use as VIPs by multiple nodes. These wouldn't be deallocated as long
>> as one or more of those nodes is still allocated.
>>
>> --
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>
>
>
>
> --
> Andres Rodriguez
> Engineering Manager, HWE Team
> Canonical USA, Inc.