Re: [Xen-devel] OSSTEST -- nested test case development, RFC: ts-guest-destroy doesn't call guest_await_dhcp_tcp() if guest has fixed IP

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Ian Campbell writes ("Re: OSSTEST -- nested test case development, RFC: 
ts-guest-destroy doesn't call guest_await_dhcp_tcp() if guest has fixed IP"):
> However by reconfiguring things to be static the L1 host will no longer be
> generating DHCP RENEW requests when the lease times out, so the DHCP server
> is at liberty to release the lease when it times out or, worse, reuse the
> IP address for something else.

Indeed.  This is wrong.

> So I think we do actually need to start supporting a dynamic mode for at
> least L1 hosts (and that may well easily extend to L0 hosts too). Although
> it is not 100% accurate I think we can assume that DHCP renewal will always
> work, i.e. once a host is given a particular IP address so long as it keeps
> renewing the lease it will keep the same address.

It isn't clear to me that we need to make this assumption, in the
general case.  We probably need to assume that the DHCP-assigned IP
addresses don't change unexpectedly during the execution of a
particular ts-* script (where `unexpectedly' means `other than as an
obvious consequence of actions such as rebooting).

> So I think we can still discover the DHCP address assigned to the L1 guest,
> and propagate it into $r{"${l1ident}_ip"} when we convert it to an L1 host,
> but we then also need to modify the Xen installation runs to use dhcp mode
> for such cases and not switch to static as we do for an L0 host.

This would be the right approach, but ...

> I'm not quite sure how this should be recorded in the runvars. I think we
> may want to wait for Ian to return from vacation next week.

... having looked at it like this, I think recording the L1 IP
addresss in the runvars is wrong.  It should be looked up each time
(by something called by selecthost).

> The alternative would be that selecthost needs to query the DHCP leases
> file for these kinds of hosts, that would have the benefit of handling
> potential lease expiry over a reboot.

Exactly.

Ian.

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