Move configuration of servers completely to ansible

With this change we no longer use user-data scripts on the provided
machines. That makes it way easier for me to handle all the
configuration, since I only have to run ansible. Furthermore this the
burdon to think what may went wrong, since ansible is easier to debug
than some arbitrary scripts which run at provisioning-time on the
machines.

With this change I should also think about restructuring the code a bit
as well. Since it's actually easier to provide the initial
software-stack for the cluster via ansible than via terraform, at least
as far as I can tell right now.

k3s/roles/agent-setup/defaults/main.yml

@@ -0,0 +1,3 @@
+dns_servers: 8.8.8.8 8.8.4.4
+network_config_path: /etc/systemd/network
+

k3s/roles/agent-setup/handlers/main.yml

@@ -0,0 +1,4 @@
+- name: Restart resolved
+  service:
+    name: systemd-resolved
+    state: restarted

k3s/roles/agent-setup/tasks/main.yml

@@ -0,0 +1,29 @@
+- name: Set default network route
+  shell: "ip route add default via {{ private_nat }}"
+  ignore_errors: "yes"
+  when: ansible_facts['default_ipv4']['alias'] is not defined
+
+- name: Regather facts
+  setup:
+  when: ansible_facts['default_ipv4']['alias'] is not defined
+
+- name: Gather fact target_nic
+  set_fact:
+    target_nic: "{{ ansible_facts['default_ipv4']['alias'] }}"
+
+- name: Ensure path to configure default route
+  file:
+    path: "{{ network_config_path }}"
+    state: directory
+
+- name: Configure default route
+  template:
+    src: nic.network.j2
+    dest: "{{ network_config_path }}/10-{{target_nic}}.network"
+
+- name: Configure DNS servers
+  lineinfile:
+    path: /etc/systemd/resolved.conf
+    regexp: '^#?\s*DNS\s*=.*'
+    line: "DNS={{ dns_servers }}"
+  notify: "Restart resolved"

k3s/roles/agent-setup/templates/nic.network.j2

@@ -0,0 +1,5 @@
+[Match]
+Name={{ target_nic }}
+[Network]
+DHCP=yes
+Gateway={{ private_nat }}

k3s/roles/server-setup/defaults/main.yml

@@ -0,0 +1,2 @@
+ip_masquerade_path: /etc/networkd-dispatcher/routable.d
+ip_masquerade_script: 10-eth0-post-up

k3s/roles/server-setup/handlers/main.yml

@@ -0,0 +1,7 @@
+- name: Restart sshd
+  service:
+    name: ssh
+    state: restarted
+
+- name: Start ip-masquerade
+  script: "{{ ip_masquerade_path }}/{{ ip_masquerade_script }}"

k3s/roles/server-setup/tasks/main.yml

@@ -0,0 +1,50 @@
+- name: Set facts for target SSH-connection
+  set_fact:
+    target_ansible_port: "{{ ansible_port }}"
+
+- name: Check if SSH-connection is already adjusted
+  ping:
+  ignore_errors: "yes"
+  ignore_unreachable: "yes"
+  register: target_ssh
+
+- name: Set ansible_port to 22 when SSH-connection is not adjusted
+  set_fact:
+    ansible_port: "22"
+  when: target_ssh.unreachable is defined and
+        target_ssh.unreachable == True
+
+- name: Check if initial SSH-connection is active
+  ping:
+  when: target_ssh.unreachable is defined and
+        target_ssh.unreachable == True
+
+- name: Set SSH-port to 1022
+  lineinfile:
+    path: /etc/ssh/sshd_config
+    regexp: '^#?\s*Port\s+[0-9]+$'
+    line: Port 1022
+  notify: "Restart sshd"
+  when: target_ssh.unreachable is defined and
+        target_ssh.unreachable == True
+
+- name: Reset ansible_port to configured value
+  set_fact:
+    ansible_port: "{{ target_ansible_port }}"
+  when: target_ssh.unreachable is defined and
+        target_ssh.unreachable == True
+
+- name: Run deferred setup to gather facts
+  setup:
+
+- name: Ensure routable.d path to masquerade ips
+  file:
+    path: "{{ ip_masquerade_path }}"
+    state: directory
+
+- name: Configure NAT to masquerade ips
+  template:
+    src: ip-masquerade.sh.j2
+    dest: "{{ ip_masquerade_path }}/{{ ip_masquerade_script }}"
+    mode: u=rwx,g=rx,o=rx
+  notify: "Start ip-masquerade"

k3s/roles/server-setup/templates/ip-masquerade.sh.j2

@@ -0,0 +1,4 @@
+#!/bin/bash
+echo 1 > /proc/sys/net/ipv4/ip_forward
+iptables -t nat -A POSTROUTING -s {{network_cidr}} -o eth0 -j MASQUERADE
+