cluck/k8s-haproxy-external-lb

This repository contains scripts and Ansible playbook to configure external HTTPS load balancer for Kubernetes, using haproxy with PROXY Protocol enabled.

Repository content requires some configuration to match one's setup, but can be treated as a starting point.

Rationale

Those scripts were created for extending functionality of my k3s cluster. K3s ships with a very simple load balancer called klipper. It's effective but fails in two scenarios:

handling both IPv6 and legacy IPv4 traffic at the same time. Klipper only receives IPv4 traffic. Scripts in this repository can configure haproxy to receive IPv6 traffic and forward to legacy IPv4 receivers.
passing client IP address information to the receiving end. Due to usage of MASQUERADE in Klipper, original IP address information is lost. There's a way to mitigate the problem in general (using PROXY protocol) but Klipper is too simple to implement it.

Architecture of the solution

There's a pod running a Python script watching EndPoint resources of pods in traefik deployment. On startup and on each change of end points, the script triggers an Ansible playbook to configure HAProxy instances.

Ansible playbook collects EndPoints information, creates haproxy configuration on edge nodes and restart haproxy service.

HAProxy listens on port :443 and passes received connections to Traefik pods(s), using TCP loadbalancing and adding PROXY information to each. TLS certificates are handled by Traefik, there is NO TLS termination on haproxy.

Optionally, port :80 and unencrypted connections can be passed, too, with PROXY information. Unencrypted connections are discouraged!

Setup

Networking setup

External haproxy is configured to connect directly to EndPoints of traefik pods. Therefore host running haproxy needs to be able to access the pod network. How to achieve that depends heavily on your setup, there's no universal recipe. I suggest using Wireguard.

If you run haproxy on cluster nodes (for IPv6-to-IPv4 ingress), the pods network is already accessible and no further configuration is needed.

Ansible and container image

Create an ansible/inventory defining you edge hosts. For each hostname define haproxy_bind directive, which controls bind directive in haproxy config file. For example:

haproxy_bind=ipv6@:443 for receiving IPv6 traffic
haproxy_bind=ipv4@:443 for handling legacy IPv4 connections. Useful for configuring load balancers on hosts not being a part of the kubernetes cluster.

There's also haproxy_bind_insecure directive for handling non-encrypted traffic on port 80. It's usage is discouraged.

Create a pair of SSH keys. Put the public part in ~root/.ssh/authorized_keys file on edge nodes.

ssh-keygen -t ed25519 -C "k8s-haproxy-external-lb_agent" -f ssh_key_agent

Private part must be accessible for our pod. Create a secret using:

kubectl -n kube-system create secret generic haproxy-agent --from-file=ssh_key_agent=ssh_key_agent

Pod need to be run with enough permissions to read EndPoint resources. Example helm chart uses traefik service account, which should be already configured on k3s cluster.
Build the image:

podman build -t registry.example.com/k8s-haproxy-external-lb:version .

and push to your registry.

PROXY protocol receiver

To parse information provided by PROXY protocol, Traefik needs configuration. This is done using proxyProtocol.trustedIPs setting for entrypoints.

In k3s, you can edit helmchart traefik in namespace kube-system and add the following:

spec:
  valuesContent: |-
    additionalArguments:
      - "--entryPoints.web.proxyProtocol.trustedIPs=198.51.100.1,10.42.0.0/16"
      - "--entryPoints.websecure.proxyProtocol.trustedIPs=198.51.100.1,10.42.0.0/16"

The IP range depends on your network configuration. In example above, 10.42.0.0/16 is Kubernetes pod network (for running IPv6-to-IPv4 haproxies) and 198.51.100.1 is outgoing address for traffic tuneled from external IPv4 edge node.

Improvement ideas

Ansible inventory should probably be turned into a ConfigMap
Configurable EndPoints names, those are hardcoded now for Traefik as shipped with k3s.

cluck / k8s-haproxy-external-lb