[ovirt-devel] Re: Suspend resume and DHCP

> On 4 Apr 2019, at 09:45, Yedidyah Bar David <didi(a)redhat.com&gt; wrote: > >> On Thu, Apr 4, 2019 at 9:02 AM Dan Kenigsberg <danken(a)redhat.com&gt; wrote: >> >>> On Wed, Apr 3, 2019 at 5:55 PM Dominik Holler <dholler(a)redhat.com&gt; wrote: >>> >>> Hello, >>> would you help me to understand if the dhcp client in an oVirt guest >>> should refresh his dhcp configuration after the guest is resumed? >>> If this is the case, how this should be triggered? >>> >>> The reason why I ask is, that if a VM suspends on a first host, and >>> resumes on a second one, libvirt's nwfilter losses the IP address of >>> the guest, which means that the guest is not reachable until he >>> refreshes dhcp config, if the clean-traffic filter with >>> CTRL_IP_LEARNING=dhcp is used. >> >> Do you know if libvirt's nwfilter transfers the IP address during live >> migration? I'd suspect that you'd have the same problem there. AFAIK we don’t have that problem >> I believe that libvirt should handle this in BOTH cases (live >> migration and suspend/resume). It should store the learned IP in the >> suspended data and revive it on the target host. What about potential conflicts?

> > Not my expertise, but regardless of the below :-), I agree with you. > >> Calling in +Laine Stump for his opinion. >> >> Regardless of this, I think that a guest should request a dhcp renewal >> upon resume. After all, it may have been suspended for few years. > > I think most, if not all, dhcp clients, would renew, once they > realized that time passed by (which is a non-trivial, but different, > issue), We resync time on resume. Libvirt was supposed to do that but we were not able to convince them, so it’s in vdsm now > if their lease expired. I think Dominik's question was > about the case that the lease was _not_ expired. > >> This can be done if we add a "resumed" notification to the guest >> agent, and have libvvirt/Vdsm trigger after resume. We have guest side hooks. Only in ovirt-ga

> > That's also just fine for me. I very briefly looked at all relevant > agents (ovirt, spice, qemu) and didn't find 'dhcp' in any of them. > So I agree it makes sense to file an RFE on one of them for this. qemu-ga most definitely. We do not have ovirt-ga in el8 and we do not plan to add any new features to it. Thanks, michal > However, we can't always rely on this - the agent might not be > available, etc. > >> >>> This scenario might happen in OST basic-suite-master and >>> basic-suite-4.3 in verify_suspend_resume_vm0. >> >> I suspect that we can work around this bug in OST by requesting Engine >> to resume vm0 on the same host it was suspended from > > And also, for this very specific use case, to simply have much > shorter leases. It seems like we currently use dnsmasq's default, > which is one hour. I guess setting it to even 2 minutes won't do > much damage, but of course this needs testing. > > Best regards, > -- > Didi > _______________________________________________ > Devel mailing list -- devel(a)ovirt.org > To unsubscribe send an email to devel-leave(a)ovirt.org > Privacy Statement: https://www.ovirt.org/site/privacy-policy/ > oVirt Code of Conduct: https://www.ovirt.org/community/about/community-guidelines/ > List Archives: https://lists.ovirt.org/archives/list/devel@ovirt.org/message/J5EV5YCMV67...