Re: [libvirt] [PATCHv3 1/2] network: added waiting for DAD to finish for bridge address.

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 On 10/08/15 22:29, Laine Stump wrote: > On 08/10/2015 01:08 PM, Maxim Perevedentsev wrote: >> This is a fix for commit >> db488c79173b240459c7754f38c3c6af9b432970 dnsmasq main process >> exits without waiting for DAD, this is dnsmasq daemon's task. So >> we periodically poll the kernel using netlink and check whether >> there are any IPv6 addresses assigned to bridge which have >> 'tentative' state. After DAD is finished, execution continues. I >> guess that is what dnsmasq was assumed to do. > Since the comments in our code imply that dnsmasq should be waiting > for DAD to complete prior to daemonizing, before pushing a fix like > this I'd like to find out from the dnsmasq folks if we are > erroneously relying on nonexistent dnsmasq behavior, or if maybe > there is a bug in some version of dnsmasq. > > Simon (or other dnsmasq people) - when dnsmasq is run with > "enable-ra", does it make sure it completes DAD prior to > daemonizing? Or does libvirt need to do this extra polling to > assure that DAD has completed? (or maybe there's some other config > parameter we need to add?) > > Dnsmasq doesn't wait for DAD to complete before returning. Internally, it know is DAD is still happening on an interface, as it needs to delay calling bind() until after it's complete. It would, therefore be relatively simple to add this behaviour, but it's not a complete solution, since new interfaces can appear _after_ dnsmasq has completed start-up. Having libvirt do its own checks whenever it creates an interface might therefore be a cleaner way of doing things, but I don't have an objection to changing dnsmasq behaviour if there's a good reason why that's not sensible.