[ovs-dev] [PATCH 4/4] Tunnel: Snoop ingress packets and update neigh cache if needed.

Paolo Valerio pvalerio at redhat.com
Mon Nov 8 19:31:26 UTC 2021

Gaëtan Rivet <grive at u256.net> writes:

> On Tue, Nov 2, 2021, at 18:12, Paolo Valerio wrote:
>> In case of native tunnel with bfd enabled, if the MAC address of the
>> remote end's interface changes (e.g. because it got rebooted, and the
>> MAC address is allocated dinamically), the BFD session will never be
>> re-established.
> typo: dynamically


>> This happens because the local tunnel neigh entry doesn't get updated,
>> and the local end keeps sending BFD packets with the old destination
>> MAC address. This was not an issue until
>> b23ddcc57d41 ("tnl-neigh-cache: tighten arp and nd snooping.")
>> because ARP requests were snooped as well avoiding the problem.
> I am not sure about perpetuating a BFD session when the tunnel line
> protocol got down and changed dynamically. Is it a normal use-case
> for BFD then?

Not a BFD expert, but depending on the mode, it normally keeps sending
control messages through the interface it is enabled on to detect the
link state.

> But then updating the ARP/ND entries does not seem an issue in and of
> itself. Code and tests looks good to me.
> Acked-by: Gaetan Rivet <grive at u256.net>

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