We need a controller which will parse bgp flowspec data and generate nftables rules.
Examples mentioned in FRR https://github.com/FRRouting/frr/blob/master/doc/user/flowspec.rst work with `iptables` and `ipset`, neither of them not used in VyOS 1.4
As an alternative way we have 2 options:
1. Try to parse FRR data with "custom LUA scripts" http://docs.frrouting.org/projects/dev-guide/en/latest/scripting.html
2. Use [[ https://github.com/Exa-Networks/exabgp | ExaBGP ]] as a controller which will generate `nft rules` for VyOS.
ExaBGP seems preferable as it uses a lot of python code.
I think it is a good idea that Controller should communicate with VyOS via API