Early introduction of vyconfd

Goal

Currently, the in-memory representation of active/session config is held by the daemon vyos-configd. This has proven quite useful, but is backwards. The front end script daemon should do little more than dispatch config mode scripts; we want a backend for in-memory store and logic. It may however be possible to introduce Vyconf now as the proper in-memory store, and establish communication Vyconf \Longleftrightarrow vyos-configd

This has additional benefits

1. Progressively implement long-term VyOS design goals

2. Redirect more functionality from Vyatta backend

3. Bring Vyconfd online sooner rather than later, to establish communication protocol and allow development

Approach

• Currently, vyshim passively redirects any command definitions of vyos-1x, leaving legacy ones untouched

• Redirect vyshim communication to vyconfd instead of vyos-configd (rename to vyos-scriptd) and set up communication vyconfd \Longleftrightarrow vyos-scriptd, establishing one long-term VyOS design goal

Reasons to investigate Cap'n Proto as communication protocol

It suggests consideration based on the following:

• Serialization and RPC
• Written by the author of Protobuf v2
• Opensource, but heavily used (and development supported) by Cloudflare
• C++/Python/OCaml
  • Reference implementation in C++
  • Maintained Cython wrapper
  • OCaml implementation by Thomas Leonard
• Many (claimed) improvements over Protobuf, mostly related to memory use; need to verify