Add rib-has-route Route-Policy Condition

[niallmasterson]

There is a requirement to support "rib-has-route" route-policy condition which is supported by multiple vendors.

"rib-has-route" is a route-policy condition which checks if a route exists in the routing-table. This is commonly used for conditional route-advertisements, i.e the route-policy condition checks if a certain prefix A exists in the routing table, and if so then advertises another prefix B.

Cisco supports "rib-has-route":
https://www.cisco.com/c/en/us/td/docs/iosxr/cisco8000/routing/cumulative/command/reference/b-routing-cr-cisco8000/m-rpl-commands-1.html#wp4036312080

Arista uses dynamic prefix-lists to support this:
https://www.arista.com/en/support/toi/eos-4-21-0f/14072-bgp-conditional-route-inject-routing-protocol-mode-rib

Juniper's equivalent is called "if-route-exists":
https://www.juniper.net/documentation/us/en/software/junos/routing-policy/bgp/topics/example/conditional-prefix-installing-configuring.html

It is proposed to add the "rib-has-route" condition to:
/routing-policy/policy-definitions/policy-definition/statements/statement/conditions/

It should support "match any" for a defined prefix-set. i.e. if any prefix within the prefix-set exists in the routing-table, then the rib-has-route condition should return true.

/routing-policy/policy-definitions/policy-definition/statements/statement/conditions/rib-has-route
/routing-policy/policy-definitions/policy-definition/statements/statement/conditions/rib-has-route/config
/routing-policy/policy-definitions/policy-definition/statements/statement/conditions/rib-has-route/config/prefix-set
/routing-policy/policy-definitions/policy-definition/statements/statement/conditions/rib-has-route/config/match-set-options
/routing-policy/policy-definitions/policy-definition/statements/statement/conditions/rib-has-route/state
/routing-policy/policy-definitions/policy-definition/statements/statement/conditions/rib-has-route/state/prefix-set
/routing-policy/policy-definitions/policy-definition/statements/statement/conditions/rib-has-route/state/match-set-options

[dplore]

So to contrast with /routing-policy/policy-definitions/policy-definition/statements/statement/conditions/match-prefix-set/config/prefix-set, the rib-has-route is checking for any route present on the device (in the RIB). Whereas match-prefix-set checks for routes learned on an import policy or sent on an export policy.

Is that the intent?

[niallmasterson]

Yes, that's right. It's checking whether the route exists in the RIB, rather than checking the routes sent/received to/from a peer.

Our use-cases only needs support for checking if the prefixes are in the default unicast ipv4 or ipv6 routing-tables.
i.e. if it is an IPv4 prefix then check the default ipv4 unicast routing table, and if it is an ipv6 prefix then check the default ipv6 unicast routing table. But maybe a leaf for specifying the table/VRF could be added in the future to provide VRF support?

[dplore]

Regarding network-instance, a given routing-policy will be applied on a protocol which is instantiated in a network-instance, so I think we are covered for the base case. Examples:

/network-instances/network-instance/protocols/protocol/bgp/global/afi-safis/afi-safi/apply-policy/config/default-export-policy

/network-instances/network-instance/protocols/protocol/ospfv2/global/inter-area-propagation-policies/inter-area-propagation-policy

/network-instances/network-instance/protocols/protocol/isis/global/inter-level-propagation-policies/level1-to-level2/config/import-policy

Agreed that allowing lookup in a different network instance could be added later via an additional leaf.

such as
/routing-policy/policy-definitions/policy-definition/statements/statement/conditions/rib-has-route/config/other-network-instance

[niallmasterson]

Sounds good!

[dplore]

@niallmasterson will you create a PR for us to review?

[niallmasterson]

yes, will do