Update EVPN prefix routes properly instead of withdraw/install #18158
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Previously bgpd needed to send a withdraw followed by an install to update an EVPN prefix route. With refcount tracking in zebra this is no longer needed Signed-off-by: Christopher Dziomba <[email protected]>
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There is one caveat after looking at this again - EVPN MH uses the same functions but slightly different, doing reference counting already in bgpd. |
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With bgpd no longer sending withdraws for EVPN prefix routes zebra needs to track the path/ref count of prefixes for an EVPN nexthop. When a route is updated the count is first increased with the new paths and then decreased with the paths of the existing/"same" route entry. However the same evpn route methods are used for EVPN MH as well, where bgpd already tracks the references. It is expected that an ADD operation for the respective A-D routes is handled as an upsert, a DEL operation should really remove the respective A-D reference on a next-hop. For this the old behaviour (no path/ref counting in zebra) is preserved. Signed-off-by: Christopher Dziomba <[email protected]>
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The behaviour for EVPN MH / A-D routes should now be the same again. I've also squashed the zebra commits into one now and fixed the code style issues hinted by CI. |
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Why is zebra responsible for the refcounting? This seems like a bgp problem not a zebra problem. As a note -> the typical pattern in zebra is to just do what it is told. This breaks that pattern. |
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As far as I understood zebra is already "refcounting" today, it tracks the prefixes for a given EVPN VTEP / nexthop. zebra is being told to add / update or withdraw a route, not an evpn nexthop, therefore it has to take care of managing the references for it. |
Today bgpd sends down withdraw and install to zebra when a EVPN prefix route is updated. There was no mechanism in zebra to track such changes and references to prefixes on EVPN nexthops.
The commits implement the respective tracking in zebra and stops sending withdraws for updates from bgpd.