I have a patch ready for ovn to send REPLIES additionally to the requests so, if we believe it makes sense, I can send it to the dev list.
On Thu, Nov 16, 2017 at 4:18 PM, Ihar Hrachyshka <[email protected]> wrote: > In neutron reference implementation, initially we were sending ARP > REPLYs only that didn't work with existing kernels in specific > scenarios. We added ARP REQUESTs (while continuing sending REPLYs). I > think it makes sense to send both types because some nodes may e.g. > know about REPLYs and not REQUESTs. If linux kernel had the mistake of > ignoring gratuitous REQUESTs till very recently, there may be other, > more niche networking stacks also exposing inconsistent behavior. > > Ihar > > On Thu, Nov 16, 2017 at 6:22 AM, Miguel Angel Ajo Pelayo > <[email protected]> wrote: > > Sorry, it's the other way around. > > > > REQUEST is what neutron reference solution started using (ANSWER was the > > previous type of ARP packet which was leading to issues with the buggy > > kernels). > > > > Since ovn-controller emits gratuitous ARPs as broadcast ARP requests, > that > > should > > work. > > > > @Ihar, if you can confirm that our understanding is correct, that'd be > > great, I also > > see that your upstream kernel patch is really modifying the behaviour to > > also > > catch ANSWER packets with sha == tha, which should be equivalent as per > RFC. > > > > On Wed, Nov 15, 2017 at 8:10 PM, Miguel Angel Ajo Pelayo > > <[email protected]> wrote: > >> > >> See inline email, I wasn't subscribed to ovs-discuss, sorry :) > >> > >> > >> On Nov 15, 2017 2:32 PM, "Miguel Angel Ajo Pelayo" <[email protected] > > > >> wrote: > >> > >> > >> We're finding that sometimes reused floating IP addresses > >> won't be reachable, for some reason. And I remembered that, > >> we found the same issue once for the reference > >> solution once, it was fixed here: [1] > >> > >> Basically because the linux kernel, under some conditions will > >> ignore the gARP requests, and reset a timeout value that would > >> keep ignoring those requests. But if it received a REPLY > >> packet instead, it worked. > >> > >> I believe that we may want to do the same in ovn controller. > >> > >> [1] > >> https://github.com/openstack/neutron/commit/ > 82831b9d8d4bd61f90610df9eca8c7f6e447f8d8 > >> > >> > > >
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