Draft: Add source-build Dockerfile for FRR container images

[jbemmel]

Enable netlab clab build frr to compile FRR from GitHub sources on debian:trixie-slim, matching the layout and startup of the official image.

This allows us to test the latest features and bug fixes, like that EVPN IPv6 issue

I tried enabling the wait-for-dataplane logic such that the MPLS label setting gets applied before Zebra starts, but the workflow for FRR is different; initial uses vtysh which requires FRR to be running.

"Solved" in the Dockerfile for now, pending possible refactoring.

devices/frr/Dockerfile.j2 might be a better location for this?

[ipspace]

What's wrong with https://blog.ipspace.net/2026/04/frr-pr-testing/

[jbemmel]

What's wrong with https://blog.ipspace.net/2026/04/frr-pr-testing/

Well, it takes 5 minutes versus 2 for my build script, and I was anticipating putting in other things like Wireguard. But you're right that there are other ways to achieve the same - hence 'Draft'

[ipspace]

Well, it takes 5 minutes versus 2 for my build scriptđ

I would still prefer the "official" build process, plus you can start the build from any commit in their repo.

and I was anticipating putting in other things like Wireguard.

For that, create your own Dockerfile, start with the official FRR container and add stuff. I don't think that needs to be integrated into netlab.

But you're right that there are other ways to achieve the same - hence 'Draft'

👍