Add configuration support for OSPF auto-cost reference bandwidth

[jovatn]

Description

Infix currently do not support configuration of the OSPF auto-cost reference bandwidth.
Instead it used the FRR default, which is 100 Gbit/s (although there is a mismatch in the FRR doc saying 100 Mbit/s)

The auto-cost reference bandwidth has to be consistent throughout the OSPF domain, thus it should be configurable in Infix to ensure interoperability with OSPF routers from other vendors.

Task should include:

• enable support for the auto-cost node in ietf-ospf@2022-10-19.yang.
  • at least the 'reference-bandwidth' leaf should be supported
  • (please comment) the 'enabled' leaf can be supported if there is a corresponding setting in FRR; otherwise always 'true'.
• (suggestion) default should match Infix current value to avoid mismatch between new and already deployed Infix units
• it should be possible to read out the current reference
• there should be a test, e.g., to see how a 1Gbit/s link gets different link cost depending on the reference bandwidth. Ref 100 Gbit/s (100000 Mbit/s) should give cost 100, Ref 10 Gbit/s should give cost 10, Ref 1Gbit/s or lower should give cost 1.

Should there be a migration script when upgrading? That is, should be explicitly add configuration with value 100000 (Mbit/s) when upgrading?

Additional Information

@troglobit has made relevant comments in Frr issue #2480

FRR setting for OSPF reference bandwidth

General Information

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Please use this issue for discussions related to the feature.