Add DHCPd role with failover

* Add a role that adds the DHCP server and a failover server
* Use ansible-vault to encrypt the MAC-address mapping
* Fixes issue 7

dhcpd.yml

+- hosts: dhcpd
+  roles:
+      - dhcpd

group_vars/dhcpd.yml

+---
+primary_dhcpd: 129.13.108.101
+secondary_dhcpd: 129.13.108.126

hosts

@@ -91,6 +91,10 @@ las126.las.kit.edu
 
 # developement
 
+[dhcpd]
+las101.las.kit.edu
+las126.las.kit.edu
+
 [lab]
 # las93.las.kit.edu
 

roles/dhcpd/files/dhcpd.conf

+# dhcpd.conf
+#
+# DHCP Server Configuration file.
+# see /usr/share/doc/dhcp/dhcpd.conf.example
+# see dhcpd.conf(5) man page
+#
+
+# option definitions common to all supported networks...
+option domain-name "las.kit.edu";
+option domain-name-servers 129.13.64.5, 129.13.96.2;
+
+default-lease-time 60;
+max-lease-time 720;
+
+# Use this to enble / disable dynamic dns updates globally.
+ddns-update-style none;
+
+# If this DHCP server is the official DHCP server for the local
+# network, the authoritative directive should be uncommented.
+authoritative;
+
+# Use this to send dhcp log messages to a different log file (you also
+# have to hack syslog.conf to complete the redirection).
+log-facility local7;
+
+# A slightly different configuration for an internal subnet.
+subnet 129.13.108.0 netmask 255.255.255.0 {
+  range 129.13.108.74 129.13.108.89;
+  option routers 129.13.108.254;
+  option broadcast-address 129.13.255.255;
+  option domain-name "las.kit.edu";
+  option domain-name-servers 129.13.64.5, 129.13.96.2;
+  default-lease-time 1800;
+  max-lease-time 7200;
+  deny unknown-clients;
+}
+
+include "/etc/dhcp/host-list-las";

roles/dhcpd/handlers/main.yml

+---
+- name: enable dhcpd
+  service:
+    name: dhcpd
+    enabled: yes
+
+- name: restart dhcpd
+  service:
+    name: dhcpd
+    state: restarted
+
+- name: start dhcpd
+  service:
+    name: dhcpd
+    state: started

roles/dhcpd/tasks/main.yml

+---
+- name: dhcpd installed
+  become: true
+  dnf:
+    name: dhcp
+    state: installed
+  notify:
+    - start dhcpd
+    - enable dhcpd
+
+- name: copy mac addresses and config
+  become: true
+  copy:
+    src: "{{ item }}"
+    dest: "/etc/dhcp/{{ item }}"
+    backup: yes
+    owner: root
+    group: root
+    validate: /sbin/dhcpd -t -cf %s
+    decrypt: yes
+  notify: restart dhcpd
+  with_items:
+    - "host-list-las"
+    - dhcpd.conf
+
+- name: install dhcpd config
+  become: true
+  template:
+    src: dhcpd.j2
+    dest: /etc/dhcp/dhcpd.conf
+    backup: yes
+    validate: /sbin/dhcpd -t -cf %s
+  notify: restart dhcpd

roles/dhcpd/templates/dhcpd.j2

+# dhcpd.conf
+#
+# {{ ansible_managed }}
+#
+# DHCP Server Configuration file.
+# see /usr/share/doc/dhcp/dhcpd.conf.example
+# see dhcpd.conf(5) man page
+#
+
+# option definitions common to all supported networks...
+option domain-name "las.kit.edu";
+option domain-name-servers 129.13.64.5, 129.13.96.2;
+
+default-lease-time 60;
+max-lease-time 720;
+
+# Use this to enble / disable dynamic dns updates globally.
+ddns-update-style none;
+
+# If this DHCP server is the official DHCP server for the local
+# network, the authoritative directive should be uncommented.
+authoritative;
+
+# Use this to send dhcp log messages to a different log file (you also
+# have to hack syslog.conf to complete the redirection).
+log-facility local7;
+
+# failover https://www.madboa.com/geek/dhcp-failover/
+# https://kb.isc.org/article/AA-00502/0/A-Basic-Guide-to-Configuring-DHCP-Failover.html
+failover peer "dhcp-failover" {
+{% if primary_dhcpd == ansible_default_ipv4.address %}
+  primary;
+  address {{ primary_dhcpd }};
+{% else %}
+  secondary;
+  address {{ secondary_dhcpd }};
+{% endif %}
+  port 647;
+  peer address
+{% if primary_dhcpd == ansible_default_ipv4.address %}
+{{ secondary_dhcpd }};
+{% else %}
+{{ primary_dhcpd }};
+{% endif %}
+  peer port 647;
+  max-response-delay 30;
+  max-unacked-updates 10;
+  load balance max seconds 3;
+{% if primary_dhcpd == ansible_default_ipv4.address %}
+  mclt 1800;
+  split 128;
+{% endif %}
+}
+
+# A slightly different configuration for an internal subnet.
+subnet 129.13.108.0 netmask 255.255.255.0 {
+  option routers 129.13.108.254;
+  option broadcast-address 129.13.255.255;
+  option domain-name "las.kit.edu";
+  option domain-name-servers 129.13.64.5, 129.13.96.2;
+  pool {
+    failover peer "dhcp-failover";
+    default-lease-time 1800;
+    max-lease-time 7200;
+    range 129.13.108.70 129.13.108.89;
+    deny unknown-clients;
+  }
+}
+
+include "/etc/dhcp/host-list-las";

roles/dhcpd/vars/main.yml

+---