dhcpcd: Install and configure dhcpcd

`dhcpcd` is a fully-featured network manager, without all the bloat of
`NetworkManager`.

dhcpcd.yml

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+- hosts: dhcpcd
+  roles:
+  - dhcpcd

roles/dhcpcd/defaults/main.yml

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+dhcpcd_send_hostname: true
+dhcpcd_use_clientid: false
+dhcpcd_persistent: true
+dhcpcd_rapid_commit: true
+dhcpcd_options: '{{ dhcpcd_default_options }}'
+dhcpcd_ntp_servers: true
+dhcpcd_interface_mtu: true
+dhcpcd_require_server_id: true
+dhcpcd_slaac_private: true
+dhcpcd_noipv4ll: false
+dhcpcd_noipv4: false
+dhcpcd_noipv6rs: false
+dhcpcd_interfaces: []

roles/dhcpcd/handlers/main.yml

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+- name: restart dhcpcd
+  service:
+    name=dhcpcd
+    state=restarted

roles/dhcpcd/tasks/main.yml

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+- name: ensure dhcpcd is installed
+  package:
+    name=dhcpcd
+    state=present
+
+- name: ensure dhcpcd is configured
+  template:
+    src=dhcpcd.conf.j2
+    dest=/etc/dhcpcd.conf
+    mode=0644
+  notify: restart dhcpcd
+
+- name: ensure dhcpcd starts at boot
+  service:
+    name=dhcpcd
+    enabled=yes
+- meta: flush_handlers
+- name: ensure dhcpcd is running
+  service:
+    name=dhcpcd
+    state=started

roles/dhcpcd/templates/dhcpcd.conf.j2

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+# A sample configuration for dhcpcd.
+# See dhcpcd.conf(5) for details.
+
+# Allow users of this group to interact with dhcpcd via the control socket.
+{% if dhcpcd_controlgroup is defined %}
+controlgroup {{ dhcpcd_controlgroup }}
+{% else %}
+#controlgroup wheel
+{% endif %}
+{% if dhcpcd_allow_interfaces is defined %}
+
+allowinterfaces {{ dhcpcd_allow_interfaces }}
+{% endif %}
+{% if dhcpcd_deny_interfaces is defined %}
+
+denyinterfaces {{ dhcpcd_deny_interfaces }}
+{% endif %}
+
+# Inform the DHCP server of our hostname for DDNS.
+{% if dhcpcd_send_hostname|bool %}
+hostname
+{% else %}
+#hostname
+{% endif %}
+
+# Use the hardware address of the interface for the Client ID.
+{% if dhcpcd_use_clientid|bool %}
+clientid
+{% else %}
+#clientid
+{% endif %}
+# or
+# Use the same DUID + IAID as set in DHCPv6 for DHCPv4 ClientID as per RFC4361.
+# Some non-RFC compliant DHCP servers do not reply with this set.
+# In this case, comment out duid and enable clientid above.
+{% if not dhcpcd_use_clientid|bool %}
+duid
+{% else %}
+#duid
+{% endif %}
+
+# Persist interface configuration when dhcpcd exits.
+{% if dhcpcd_persistent|bool %}
+persistent
+{% else %}
+#persistent
+{% endif %}
+
+# Rapid commit support.
+# Safe to enable by default because it requires the equivalent option set
+# on the server to actually work.
+{% if dhcpcd_rapid_commit|bool %}
+option rapid_commit
+{% else %}
+#option rapid_commit
+{% endif %}
+
+# A list of options to request from the DHCP server.
+{% for option in dhcpcd_options %}
+option {{ option }}
+{% endfor %}
+# Most distributions have NTP support.
+{% if dhcpcd_ntp_servers|bool %}
+option ntp_servers
+{% else %}
+#option ntp_servers
+{% endif %}
+# Respect the network MTU. This is applied to DHCP routes.
+{% if dhcpcd_interface_mtu|bool %}
+option interface_mtu
+{% else %}
+#option interface_mtu
+{% endif %}
+
+# A ServerID is required by RFC2131.
+{% if dhcpcd_require_server_id|bool %}
+require dhcp_server_identifier
+{% else %}
+#require dhcp_server_identifier
+{% endif %}
+
+# Generate Stable Private IPv6 Addresses instead of hardware based ones
+{% if dhcpcd_slaac_private|bool %}
+slaac private
+{% else %}
+#slaac private
+{% endif %}
+{% if dhcpcd_noipv4ll|bool %}
+
+# Disable IPv4 link-local address automatic configuration (APIPA)
+noipv4ll
+{% endif %}
+{% if dhcpcd_noipv4|bool %}
+
+# Disable IPv4 configuration entirely
+noipv4
+{% endif %}
+{% if dhcpcd_noipv6rs|bool %}
+
+# Disable IPv6 router solicitations
+noipv6rs
+{% endif %}
+{% for iface in dhcpcd_interfaces %}
+
+{% if iface.description is defined %}
+# {{ iface.description }}
+{% endif %}
+interface {{ iface.name }}
+{% for setting in iface.config %}
+    {{ setting }}
+{% endfor %}
+{% endfor %}

roles/dhcpcd/vars/main.yml

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+dhcpcd_default_options:
+- domain_name_servers, domain_name, domain_search, host_name
+- classless_static_routes