[ovs-discuss] Thoughts on gratuitous ARP

Miguel Angel Ajo Pelayo majopela at redhat.com
Thu Nov 16 14:22:35 UTC 2017


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 <
majopela at redhat.com> wrote:

> See inline email, I wasn't subscribed to ovs-discuss, sorry :)
>
>
> On Nov 15, 2017 2:32 PM, "Miguel Angel Ajo Pelayo" <majopela at redhat.com>
> 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/82831b9d8d4b
> d61f90610df9eca8c7f6e447f8d8
>
>
>
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