On Mon, 16 Nov 2020 23:18:15 +0100 Pablo Neira Ayuso wrote: > On Sat, Nov 14, 2020 at 09:03:47AM -0800, Jakub Kicinski wrote: > > On Sat, 14 Nov 2020 15:00:03 +0100 Tobias Waldekranz wrote: > > > On Sat, Nov 14, 2020 at 12:59, Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx> wrote: > > > > If any of the flowtable device goes down / removed, the entries are > > > > removed from the flowtable. This means packets of existing flows are > > > > pushed up back to classic bridge / forwarding path to re-evaluate the > > > > fast path. > > > > > > > > For each new flow, the fast path that is selected freshly, so they use > > > > the up-to-date FDB to select a new bridge port. > > > > > > > > Existing flows still follow the old path. The same happens with FIB > > > > currently. > > > > > > > > It should be possible to explore purging entries in the flowtable that > > > > are stale due to changes in the topology (either in FDB or FIB). > > > > > > > > What scenario do you have specifically in mind? Something like VM > > > > migrates from one bridge port to another? > > > > Indeed, 2 VMs A and B, talking to each other, A is _outside_ the > > system (reachable via eth0), B is inside (veth1). When A moves inside > > and gets its veth. Neither B's veth1 not eth0 will change state, so > > cache wouldn't get flushed, right? > > The flow tuple includes the input interface as part of the hash key, > so packets will not match the existing entries in the flowtable after > the topology update. To be clear - the input interface for B -> A traffic remains B. So if B was talking to A before A moved it will keep hitting the cached entry. Are you saying A -> B traffic won't match so it will update the cache, since conntrack flows are bi-directional? > The stale flow entries are removed after 30 seconds > if no matching packets are seen. New flow entries will be created for > the new topology, a few packets have to go through the classic > forwarding path so the new flow entries that represent the flow in the > new topology are created.
