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  1. OpenShift Bugs
  2. OCPBUGS-63003

Align and document incompatibility of dual stack BGP sessions

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    • CORENET Sprint 278
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      OVN-Kubernetes RouteAdvertisements feature does not support dual stack BGP sessions:

      			// If MultiProtocol is enabled (default) then a BGP session carries
      			// prefixes of both IPv4 and IPv6 families. Our problem is that with
      			// an IPv4 session, FRR can incorrectly pick the masquerade IPv6
      			// address (instead of the real address) as next hop for IPv6
      			// prefixes and that won't work. Note that with a dedicated IPv6
      			// session that can't happen since FRR will use the same address
      			// that was used to stablish the session. Let's enforce the use of
      			// DisableMP for now.
      			if !neighbor.DisableMP {
      				return nil, fmt.Errorf("%w: DisableMP==false not supported, seen on FRRConfiguration %s/%s neighbor %s",
      					errConfig,
      					source.Namespace,
      					source.Name,
      					neighbor.Address,
      				)
      			}
      

      However it has been acknowledged by FRR-k8s project that defaulting to dualstack BGP sessions through DisableMP=false was mistake and DisableMP has been deprecated and replaced with dualStackAddressFamily that defaults to false and thus dualstack BGP sessions are disabled by default.

      Through this bug we should:
      For OCP 4.20+:

      • Replace the check for DisableMP=false in favor of checking for dualStackAddressFamily=true
      • Explicitly document the incompatibility of using RouteAdvertisements together with FRRConfiguration or BGPPeers that set dualStackAddressFamily=true
        For OCP 4.19:
      • Explicitly document the incompatibility of using RouteAdvertisements together with FRRConfiguration or BGPPeers that set DisableMP=false or omit setting DisableMP , or what is equivalent, that do not set DisableMP=true

              ocp-docs-bot OCP DocsBot
              jcaamano@redhat.com Jaime CaamaƱo Ruiz
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              Peng Liu
              Anurag Saxena Anurag Saxena
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                Created:
                Updated: