Move infra-setup and k3s-setup into dedicated directories

This changes makes it easier to differentiate and understand the
different parts of the kubernetes setup. On one hand we have the bare
infrastructure (servers, network, etc), on the other hand we have the
software (k3s in this case).

In the future we'll have a few more parts, like the minimal
configuration of the kubernetes cluster, e.g. with a cert-manager. This
is easier to manage with helm or terraform than with ansible. Therefore
it makes even more sense to split the responsibilities into dedicated
directories.

infra/modules/hetzner/kubernetes/agent-init.yaml.tftpl

@@ -0,0 +1,17 @@
+#cloud-config
+packages:
+- curl
+users:
+- name: cluster
+  shell: /bin/bash
+runcmd:
+# configure correct routing via NAT
+- ip route add default via ${network_gateway}
+- NIC=$(ifconfig | grep -q enp7s0 && echo enp7s0 || echo ens10)
+- echo "[Match]" > /etc/systemd/network/10-$NIC.network
+- echo "Name=$NIC" >> /etc/systemd/network/10-$NIC.network
+- echo "[Network]" >> /etc/systemd/network/10-$NIC.network
+- echo "DHCP=yes" >> /etc/systemd/network/10-$NIC.network
+- echo "Gateway=${network_gateway}" >> /etc/systemd/network/10-$NIC.network
+- sed -e "s/#DNS=/DNS=${dns_servers}/" -i /etc/systemd/resolved.conf
+- systemctl restart systemd-resolved

infra/modules/hetzner/kubernetes/main.tf

@@ -0,0 +1,133 @@
+locals {
+  network           = "10.0.0.0/16"
+  subnet_eu_central = "10.0.0.0/24"
+  servers = {
+    for idx, config in var.servers : "${var.name}-server-${idx + 1}" => merge(
+      config,
+      {
+        ip       = cidrhost(local.subnet_eu_central, idx + 2)
+        first_ip = idx == 0 ? "" : cidrhost(local.subnet_eu_central, 2)
+      }
+    )
+  }
+  agents = merge([
+    for idx, config in var.agents : {
+      for n in range(0, config.count) : "${var.name}-agent-${idx + 1}-${n + 1}" => merge(
+        config,
+        { ip = cidrhost(local.subnet_eu_central, 255 - (idx * 20) - n - 1) }
+      )
+    }
+  ]...)
+  all_ips           = ["0.0.0.0/0", "::/0"]
+  ping_firewall     = var.ping_enabled ? { "ping" : [{ protocol = "icmp", port = null }] } : {}
+  k8s_firewall      = { "kubernetes" : [{ port = "6443", source_ips = concat([local.network], var.kubernetes_exposed_ips) }] }
+  ssh_firewall      = length(var.ssh_exposed_ips) > 0 ? { "ssh" : [{ port = 1022, source_ips = var.ssh_exposed_ips }] } : {}
+  service_firewalls = { for service, ports in var.public_tcp_services : service => [for port in ports : { port = port }] }
+  firewalls = merge(
+    local.ping_firewall,
+    local.k8s_firewall,
+    local.ssh_firewall,
+    local.service_firewalls
+  )
+}
+
+resource "hcloud_network" "this" {
+  name     = var.name
+  ip_range = local.network
+}
+
+resource "hcloud_network_subnet" "this" {
+  type         = "cloud"
+  network_id   = hcloud_network.this.id
+  network_zone = "eu-central"
+  ip_range     = local.subnet_eu_central
+}
+
+resource "hcloud_network_route" "this" {
+  network_id  = hcloud_network.this.id
+  destination = "0.0.0.0/0"
+  gateway     = cidrhost(local.subnet_eu_central, 2)
+}
+
+resource "random_string" "k3s_token" {
+  length  = 100
+  special = false
+}
+
+resource "hcloud_firewall" "this" {
+  for_each = local.firewalls
+
+  name = each.key
+  dynamic "rule" {
+    for_each = each.value
+    content {
+      direction  = lookup(rule.value, "direction", "in")
+      protocol   = lookup(rule.value, "protocol", "tcp")
+      source_ips = lookup(rule.value, "source_ips", local.all_ips)
+      port       = lookup(rule.value, "port")
+    }
+  }
+}
+resource "hcloud_server" "server" {
+  depends_on  = [hcloud_network_subnet.this]
+  for_each    = local.servers
+
+  lifecycle {
+    ignore_changes = [ user_data ]
+  }
+
+  name        = each.key
+  image       = "ubuntu-24.04"
+  server_type = each.value.type
+  location    = each.value.location
+  ssh_keys    = var.ssh_keys
+  public_net {
+    ipv4 = each.value.ipv4_id
+    ipv6 = each.value.ipv6_id
+  }
+  network {
+    network_id = hcloud_network.this.id
+    ip         = each.value.ip
+  }
+  user_data = templatefile(
+    "${path.module}/server-init.yaml.tftpl",
+    {
+      network_ip_range = local.network
+      k3s_token        = random_string.k3s_token.result
+      first_ip         = each.value.first_ip
+    }
+  )
+  firewall_ids = [for firewall in hcloud_firewall.this : firewall.id]
+}
+
+resource "hcloud_server" "agent" {
+  depends_on = [hcloud_server.server]
+  for_each   = local.agents
+
+  lifecycle {
+    ignore_changes = [ user_data ]
+  }
+
+  name        = each.key
+  image       = "ubuntu-24.04"
+  server_type = each.value.type
+  location    = each.value.location
+  ssh_keys    = var.ssh_keys
+  public_net {
+    ipv4_enabled = false
+    ipv6_enabled = false
+  }
+  network {
+    network_id = hcloud_network.this.id
+    ip         = each.value.ip
+  }
+  user_data = templatefile(
+    "${path.module}/agent-init.yaml.tftpl",
+    {
+      server_ip       = cidrhost(local.subnet_eu_central, 2)
+      network_gateway = cidrhost(local.subnet_eu_central, 1)
+      dns_servers     = "8.8.8.8 8.8.4.4"
+      k3s_token       = random_string.k3s_token.result
+    }
+  )
+}

infra/modules/hetzner/kubernetes/outputs.tf

@@ -0,0 +1,11 @@
+output "server_ips_v4" {
+  value = [for key, value in hcloud_server.server : value.ipv4_address]
+}
+
+output "server_ips_v6" {
+  value = [for key, value in hcloud_server.server : value.ipv6_address]
+}
+
+output "agent_ips_v4" {
+  value = flatten([for key, value in hcloud_server.agent : value.network.*.ip])
+}

infra/modules/hetzner/kubernetes/server-init.yaml.tftpl

@@ -0,0 +1,13 @@
+#cloud-config
+packages:
+- curl
+users:
+- name: cluster
+  shell: /bin/bash
+runcmd:
+# configure NAT
+- echo '#!/bin/bash' > /etc/networkd-dispatcher/routable.d/10-eth0-post-up
+- echo 'echo 1 > /proc/sys/net/ipv4/ip_forward' >> /etc/networkd-dispatcher/routable.d/10-eth0-post-up
+- echo 'iptables -t nat -A POSTROUTING -s ${network_ip_range} -o eth0 -j MASQUERADE' >> /etc/networkd-dispatcher/routable.d/10-eth0-post-up
+- chmod +x /etc/networkd-dispatcher/routable.d/10-eth0-post-up
+- /etc/networkd-dispatcher/routable.d/10-eth0-post-up

infra/modules/hetzner/kubernetes/variables.tf

@@ -0,0 +1,44 @@
+variable "name" {
+  type = string
+}
+
+variable "ssh_keys" {
+  type = list(string)
+}
+
+variable "servers" {
+  type = list(object({
+    ipv4_id  = number
+    ipv6_id  = number
+    type     = string
+    location = string
+  }))
+}
+
+variable "agents" {
+  type = list(object({
+    count    = optional(number, 1)
+    type     = string
+    location = string
+  }))
+}
+
+variable "ping_enabled" {
+  type = bool
+  default = true
+}
+
+variable "public_tcp_services" {
+  type = map(list(string))
+  default = {}
+}
+
+variable "kubernetes_exposed_ips" {
+  type = list(string)
+  default = []
+}
+
+variable "ssh_exposed_ips" {
+  type = list(string)
+  default = []
+}

infra/modules/hetzner/kubernetes/versions.tf

@@ -0,0 +1,14 @@
+terraform {
+  required_providers {
+    hcloud = {
+      source = "hetznercloud/hcloud"
+      version = "1.50.0"
+    }
+    random = {
+      source = "hashicorp/random"
+      version = "3.7.1"
+    }
+  }
+}
+
+