Merge branch 'dhcpv6-server-rewrite' into current

* dhcpv6-server-rewrite:
  T811: dhcpv6_server.py: add missing validators when comitting config changes
  dhcp_server.py: cleanup
  bcast_relay.py: remove obsolete import statement
  vyos: package: bugfix in validate.py for is_subnet_connected()
  T778: dhcpv6-server: XML and Python rewrite

5 files changed, 804 insertions, 35 deletions

diff --git a/interface-definitions/dhcpv6-server.xml b/interface-definitions/dhcpv6-server.xml
new file mode 100644
index 000000000..e63eb2242
--- /dev/null
+++ b/interface-definitions/dhcpv6-server.xml
@@ -0,0 +1,316 @@
+<?xml version="1.0"?>
+<!-- DHCPv6 server configuration -->
+<interfaceDefinition>
+  <node name="service">
+    <children>
+      <node name="dhcpv6-server" owner="${vyos_conf_scripts_dir}/dhcpv6_server.py">
+        <properties>
+          <help>DHCP for IPv6 (DHCPv6) server</help>
+          <priority>900</priority>
+        </properties>
+        <children>
+          <leafNode name="disable">
+            <properties>
+              <help>Option to disable DHCPv6 server</help>
+              <valueless/>
+            </properties>
+          </leafNode>
+          <leafNode name="preference">
+            <properties>
+              <help>Preference of this DHCPv6 server compared with others</help>
+              <valueHelp>
+                <format>0-255</format>
+                <description>DHCPv6 server preference (0-255)</description>
+              </valueHelp>
+              <constraint>
+                <validator name="numeric" argument="--range 0-255"/>
+              </constraint>
+              <constraintErrorMessage>Preference must be between 0 and 255</constraintErrorMessage>
+            </properties>
+          </leafNode>
+          <tagNode name="shared-network-name">
+            <properties>
+              <help>DHCPv6 shared network name [REQUIRED]</help>
+              <constraint>
+                <regex>^[-_a-zA-Z0-9.]+$</regex>
+              </constraint>
+              <constraintErrorMessage>Invalid DHCPv6 pool name</constraintErrorMessage>
+            </properties>
+            <children>
+              <leafNode name="disable">
+                <properties>
+                  <help>Option to disable DHCPv6 configuration for shared-network</help>
+                  <valueless/>
+                </properties>
+              </leafNode>
+              <tagNode name="subnet">
+                <properties>
+                  <help>IPv6 DHCP subnet for this shared network [REQUIRED]</help>
+                  <valueHelp>
+                    <format>ipv6net</format>
+                    <description>IPv6 address and prefix length</description>
+                  </valueHelp>
+                  <constraint>
+                    <validator name="ipv6-prefix"/>
+                  </constraint>
+                </properties>
+                <children>
+                  <node name="address-range">
+                    <properties>
+                      <help>Parameters setting ranges for assigning IPv6 addresses</help>
+                    </properties>
+                    <children>
+                      <tagNode name="prefix">
+                        <properties>
+                          <help>IPv6 prefix defining range of addresses to assign</help>
+                          <valueHelp>
+                            <format>ipv6net</format>
+                            <description>IPv6 address and prefix length</description>
+                          </valueHelp>
+                          <constraint>
+                            <validator name="ipv6-prefix"/>
+                          </constraint>
+                        </properties>
+                        <children>
+                          <leafNode name="temporary">
+                            <properties>
+                              <help>Address range will be used for temporary addresses</help>
+                              <valueless/>
+                            </properties>
+                          </leafNode>
+                        </children>
+                      </tagNode>
+                      <tagNode name="start">
+                        <properties>
+                          <help>First in range of consecutive IPv6 addresses to assign</help>
+                          <valueHelp>
+                            <format>ipv6</format>
+                            <description>IPv6 address</description>
+                          </valueHelp>
+                          <constraint>
+                            <validator name="ipv6-address"/>
+                          </constraint>
+                        </properties>
+                        <children>
+                          <leafNode name="stop">
+                            <properties>
+                              <help>Last in range of consecutive IPv6 addresses</help>
+                              <valueHelp>
+                                <format>ipv6</format>
+                                <description>IPv6 address</description>
+                              </valueHelp>
+                              <constraint>
+                                <validator name="ipv6-address"/>
+                              </constraint>
+                            </properties>
+                          </leafNode>
+                        </children>
+                      </tagNode>
+                    </children>
+                  </node>
+                  <leafNode name="domain-search">
+                    <properties>
+                      <help>Domain name for client to search</help>
+                      <constraint>
+                        <regex>^[-_a-zA-Z0-9.]+$</regex>
+                      </constraint>
+                      <constraintErrorMessage>Invalid domain name syntax</constraintErrorMessage>
+                      <multi/>
+                    </properties>
+                  </leafNode>
+                  <node name="lease-time">
+                    <properties>
+                      <help>Parameters relating to the lease time</help>
+                    </properties>
+                    <children>
+                      <leafNode name="default">
+                        <properties>
+                          <help>Default time (in seconds) that will be assigned to a lease</help>
+                        </properties>
+                      </leafNode>
+                      <leafNode name="maximum">
+                        <properties>
+                          <help>Maximum time (in seconds) that will be assigned to a lease</help>
+                        </properties>
+                      </leafNode>
+                      <leafNode name="minimum">
+                        <properties>
+                          <help>Minimum time (in seconds) that will be assigned to a lease</help>
+                        </properties>
+                      </leafNode>
+                    </children>
+                  </node>
+                  <leafNode name="name-server">
+                    <properties>
+                      <help>IPv6 address of a Recursive DNS Server</help>
+                      <valueHelp>
+                        <format>ipv6</format>
+                        <description>IPv6 address of DNS name server</description>
+                      </valueHelp>
+                      <constraint>
+                        <validator name="ipv6-address"/>
+                      </constraint>
+                      <multi/>
+                    </properties>
+                  </leafNode>
+                  <leafNode name="nis-domain">
+                    <properties>
+                      <help>NIS domain name for client to use</help>
+                      <constraint>
+                        <regex>^[-_a-zA-Z0-9.]+$</regex>
+                      </constraint>
+                      <constraintErrorMessage>Invalid NIS domain name syntax</constraintErrorMessage>
+                    </properties>
+                  </leafNode>
+                  <leafNode name="nis-server">
+                    <properties>
+                      <help>IPv6 address of a NIS Server</help>
+                      <valueHelp>
+                        <format>ipv6</format>
+                        <description>IPv6 address of NIS server</description>
+                      </valueHelp>
+                      <constraint>
+                        <validator name="ipv6-address"/>
+                      </constraint>
+                      <multi/>
+                    </properties>
+                  </leafNode>
+                  <leafNode name="nisplus-domain">
+                    <properties>
+                      <help>NIS+ domain name for client to use</help>
+                      <constraint>
+                        <regex>^[-_a-zA-Z0-9.]+$</regex>
+                      </constraint>
+                      <constraintErrorMessage>Invalid NIS+ domain name syntax</constraintErrorMessage>
+                    </properties>
+                  </leafNode>
+                  <leafNode name="nisplus-server">
+                    <properties>
+                      <help>IPv6 address of a NIS+ Server</help>
+                      <valueHelp>
+                        <format>ipv6</format>
+                        <description>IPv6 address of NIS+ server</description>
+                      </valueHelp>
+                      <constraint>
+                        <validator name="ipv6-address"/>
+                      </constraint>
+                      <multi/>
+                    </properties>
+                  </leafNode>
+                  <node name="prefix-delegation">
+                    <properties>
+                      <help>Parameters relating to IPv6 prefix delegation</help>
+                    </properties>
+                    <children>
+                      <tagNode name="start">
+                        <properties>
+                          <help>First in range of IPv6 addresses to be used in prefix delegation</help>
+                          <valueHelp>
+                            <format>ipv6</format>
+                            <description>IPv6 address used in prefix delegation</description>
+                          </valueHelp>
+                          <constraint>
+                            <validator name="ipv6-address"/>
+                          </constraint>
+                        </properties>
+                        <children>
+                          <leafNode name="prefix-length">
+                            <properties>
+                              <help>Length in bits of prefixes to be delegated</help>
+                              <valueHelp>
+                                <format>0-255</format>
+                                <description>DHCPv6 server preference (0-255)</description>
+                              </valueHelp>
+                              <constraint>
+                                <validator name="numeric" argument="--range 0-255"/>
+                              </constraint>
+                              <constraintErrorMessage>Preference must be between 0 and 255</constraintErrorMessage>
+                            </properties>
+                          </leafNode>
+                          <leafNode name="stop">
+                            <properties>
+                              <help>Last in range of IPv6 addresses to be used in prefix delegation</help>
+                              <valueHelp>
+                                <format>ipv6</format>
+                                <description>IPv6 address used in prefix delegation</description>
+                              </valueHelp>
+                              <constraint>
+                                <validator name="ipv6-address"/>
+                              </constraint>
+                            </properties>
+                          </leafNode>
+                        </children>
+                      </tagNode>
+                    </children>
+                  </node>
+                  <leafNode name="sip-server-address">
+                    <properties>
+                      <help>IPv6 address of SIP server</help>
+                      <valueHelp>
+                        <format>ipv6</format>
+                        <description>IPv6 address of SIP server</description>
+                      </valueHelp>
+                      <constraint>
+                        <validator name="ipv6-address"/>
+                      </constraint>
+                      <multi/>
+                    </properties>
+                  </leafNode>
+                  <leafNode name="sip-server-name">
+                    <properties>
+                      <help>SIP server name</help>
+                      <constraint>
+                        <regex>^[-_a-zA-Z0-9.]+$</regex>
+                      </constraint>
+                      <constraintErrorMessage>Invalid SIP server name syntax</constraintErrorMessage>
+                      <multi/>
+                    </properties>
+                  </leafNode>
+                  <leafNode name="sntp-server">
+                    <properties>
+                      <help>IPv6 address of an SNTP Server for client to use</help>
+                      <constraint>
+                        <validator name="ipv6-address"/>
+                      </constraint>
+                      <multi/>
+                    </properties>
+                  </leafNode>
+                  <tagNode name="static-mapping">
+                    <properties>
+                      <help>Name of static mapping</help>
+                    </properties>
+                    <children>
+                      <leafNode name="disable">
+                        <properties>
+                          <help>Option to disable static-mapping</help>
+                          <valueless/>
+                        </properties>
+                      </leafNode>
+                      <leafNode name="identifier">
+                        <properties>
+                          <help>Client identifier for this static mapping</help>
+                        </properties>
+                      </leafNode>
+                      <leafNode name="ipv6-address">
+                        <properties>
+                          <help>Client IPv5 address for this static mapping</help>
+                          <valueHelp>
+                            <format>ipv6</format>
+                            <description>IPv6 address for this tatic mapping</description>
+                          </valueHelp>
+                          <constraint>
+                            <validator name="ipv6-address"/>
+                          </constraint>
+                        </properties>
+                      </leafNode>
+                    </children>
+                  </tagNode>
+                </children>
+              </tagNode>
+            </children>
+          </tagNode>
+        </children>
+      </node>
+    </children>
+  </node>
+</interfaceDefinition>
diff --git a/python/vyos/validate.py b/python/vyos/validate.py
index b681edc5e..1b77f196a 100644
--- a/python/vyos/validate.py
+++ b/python/vyos/validate.py
@@ -68,7 +68,8 @@ def is_subnet_connected(subnet, primary=False):
     system.
 
     primary check if the subnet is reachable via the primary IP address of this
-    interface. E.g. ISC DHCP can only listen on primary addresses.
+    interface, or in other words has a broadcast address configured. ISC DHCP
+    for instance will complain if it should listen on non broadcast interfaces.
 
     Return True/False
     """
@@ -81,7 +82,7 @@ def is_subnet_connected(subnet, primary=False):
     for interface in netifaces.interfaces():
         # check if the requested address type is configured at all
         if addr_type not in netifaces.ifaddresses(interface).keys():
-            return False
+            continue
 
         # An interface can have multiple addresses, but some software components
         # only support the primary address :(
diff --git a/src/conf_mode/bcast_relay.py b/src/conf_mode/bcast_relay.py
index 8cc948610..d1257d4a5 100755
--- a/src/conf_mode/bcast_relay.py
+++ b/src/conf_mode/bcast_relay.py
@@ -19,7 +19,6 @@
 import sys
 import os
 import fnmatch
-import subprocess
 import jinja2
 
 from vyos.config import Config
diff --git a/src/conf_mode/dhcp_server.py b/src/conf_mode/dhcp_server.py
index 1458ed1d0..a26e4626a 100755
--- a/src/conf_mode/dhcp_server.py
+++ b/src/conf_mode/dhcp_server.py
@@ -38,8 +38,8 @@ config_tmpl = """
 
 # For options please consult the following website:
 # https://www.isc.org/wp-content/uploads/2017/08/dhcp43options.html
-
-log-facility local7;
+#
+# log-facility local7;
 
 {% if hostfile_update %}
 on commit {
@@ -112,12 +112,12 @@ failover peer "{{ subnet.failover_name }}" {
 {% for network in shared_network %}
 {%- if not network.disabled -%}
 shared-network {{ network.name }} {
-    {% if network.authoritative %}authoritative;{% endif %}
+    {{ "authoritative;" if network.authoritative }}
     {%- if network.network_parameters %}
     # The following {{ network.network_parameters | length }} line(s) were added as shared-network-parameters in the CLI and have not been validated
     {%- for param in network.network_parameters %}
     {{ param }}
-    {%- endfor -%}
+    {%- endfor %}
     {%- endif %}
     {%- for subnet in network.subnet %}
     subnet {{ subnet.address }} netmask {{ subnet.netmask }} {
@@ -195,9 +195,15 @@ shared-network {{ network.name }} {
         }
         {%- endif %}
         {%- endfor %}
-        {%- for range in subnet.range %}
-        range {{ range.start }} {{ range.stop }};
-        {%- endfor %}
+        pool {
+            {%- if subnet.failover_name %}
+            failover peer "{{ subnet.failover_name }}";
+            deny dynamic bootp clients;
+            {%- endif %}
+            {%- for range in subnet.range %}
+            range {{ range.start }} {{ range.stop }};
+            {%- endfor %}
+        }
     }
     {%- endfor %}
     on commit { set shared-networkname = "{{ network.name }}"; }
@@ -606,17 +612,17 @@ def verify(dhcp):
         raise ConfigError('No DHCP shared networks configured.\n' \
                           'At least one DHCP shared network must be configured.')
 
+    # Inspect shared-network/subnet
+    failover_names = []
+    listen_ok = False
+    subnets = []
+
     # A shared-network requires a subnet definition
     for network in dhcp['shared_network']:
         if len(network['subnet']) == 0:
             raise ConfigError('No DHCP lease subnets configured for {0}. At least one\n' \
                               'lease subnet must be configured for each shared network.'.format(network['name']))
 
-    # Inspect our subnet configuration
-    failover_names = []
-    listen_ok = False
-    subnets = []
-    for network in dhcp['shared_network']:
         for subnet in network['subnet']:
             # Subnet static route declaration requires destination and router
             if subnet['static_subnet'] or subnet['static_router']:
@@ -650,34 +656,34 @@ def verify(dhcp):
                 stop = range['stop']
                 # DHCP stop IP required after start IP
                 if start and not stop:
-                    raise ConfigError('Stop IP address in DHCP range for start {0} is not defined!'.format(start))
+                    raise ConfigError('DHCP range stop address for start {0} is not defined!'.format(start))
 
                 # Start address must be inside network
                 if not ipaddress.ip_address(start) in ipaddress.ip_network(subnet['network']):
-                    raise ConfigError('Start IP address {0} of DHCP range is not in subnet {1}\n' \
+                    raise ConfigError('DHCP range start address {0} is not in subnet {1}\n' \
                                       'specified for shared network {2}!'.format(start, subnet['network'], network['name']))
 
                 # Stop address must be inside network
                 if not ipaddress.ip_address(stop) in ipaddress.ip_network(subnet['network']):
-                    raise ConfigError('Stop IP address {0} of DHCP range is not in subnet {1}\n' \
+                    raise ConfigError('DHCP range stop address {0} is not in subnet {1}\n' \
                                       'specified for shared network {2}!'.format(stop, subnet['network'], network['name']))
 
                 # Stop address must be greater or equal to start address
                 if not ipaddress.ip_address(stop) >= ipaddress.ip_address(start):
-                    raise ConfigError('Stop IP address {0} of DHCP range should be greater or equal\n' \
-                                      'to the start IP address {1} of this range!'.format(stop, start))
+                    raise ConfigError('DHCP range stop address {0} must be greater or equal\n' \
+                                      'to the range start address {1}!'.format(stop, start))
 
                 # Range start address must be unique
                 if start in range_start:
                     raise ConfigError('Conflicting DHCP lease range:\n' \
-                                      'Pool start IP address {0} defined multipe times!'.format(range['start']))
+                                      'Pool start address {0} defined multipe times!'.format(start))
                 else:
                     range_start.append(start)
 
                 # Range stop address must be unique
                 if stop in range_stop:
                     raise ConfigError('Conflicting DHCP lease range:\n' \
-                                      'Pool stop IP address {0} defined multipe times!'.format(range['stop']))
+                                      'Pool stop address {0} defined multipe times!'.format(stop))
                 else:
                     range_stop.append(stop)
 
@@ -705,18 +711,18 @@ def verify(dhcp):
             for mapping in subnet['static_mapping']:
                 # Static IP address must be configured
                 if not mapping['ip_address']:
-                    raise ConfigError('No static lease IP address specified for static mapping {0}\n' \
-                                      'under shared network name {1}!'.format(mapping['name'], network['name']))
+                    raise ConfigError('DHCP static lease IP address not specified for static mapping\n' \
+                                      '{0} under shared network name {1}!'.format(mapping['name'], network['name']))
 
                 # Static IP address must be in bound
                 if not ipaddress.ip_address(mapping['ip_address']) in ipaddress.ip_network(subnet['network']):
-                    raise ConfigError('Static DHCP lease IP address {0} under static mapping {1}\n' \
-                                      'in shared network {2} is outside DHCP lease network {3}!' \
+                    raise ConfigError('DHCP static lease IP address {0} for static mapping {1}\n' \
+                                      'in shared network {2} is outside DHCP lease subnet {3}!' \
                                       .format(mapping['ip_address'], mapping['name'], network['name'], subnet['network']))
 
                 # Static mapping requires MAC address
                 if not mapping['mac_address']:
-                     raise ConfigError('No static lease MAC address specified for static mapping\n' \
+                     raise ConfigError('DHCP static lease MAC address not specified for static mapping\n' \
                                        '{0} under shared network name {1}!'.format(mapping['name'], network['name']))
 
             # There must be one subnet connected to a listen interface.
@@ -725,28 +731,24 @@ def verify(dhcp):
                 if vyos.validate.is_subnet_connected(subnet['network'], primary=True):
                     listen_ok = True
 
-            #
             # Subnets must be non overlapping
-            #
             if subnet['network'] in subnets:
-                raise ConfigError('Subnets must be unique! Subnet {0} defined multiple times!'.format(subnet))
+                raise ConfigError('DHCP subnets must be unique! Subnet {0} defined multiple times!'.format(subnet))
             else:
                 subnets.append(subnet['network'])
 
-            #
             # Check for overlapping subnets
-            #
             net = ipaddress.ip_network(subnet['network'])
             for n in subnets:
                 net2 = ipaddress.ip_network(n)
-                if (net.compare_networks(net2) != 0):
+                if (net != net2):
                     if net.overlaps(net2):
-                        raise ConfigError('Conflicting subnet ranges: {0} overlaps with {1}'.format(net, net2))
+                        raise ConfigError('DHCP conflicting subnet ranges: {0} overlaps {1}'.format(net, net2))
 
     if not listen_ok:
         raise ConfigError('None of the DHCP lease subnets are inside any configured subnet on\n' \
                           'broadcast interfaces. At least one lease subnet must be set such that\n' \
-                          'DHCP server listens on a one broadcast interface')
+                          'DHCP server listens on a one broadcast interface!')
 
     return None
 
diff --git a/src/conf_mode/dhcpv6_server.py b/src/conf_mode/dhcpv6_server.py
new file mode 100755
index 000000000..bb3e6e90d
--- /dev/null
+++ b/src/conf_mode/dhcpv6_server.py
@@ -0,0 +1,451 @@
+#!/usr/bin/env python3
+#
+# Copyright (C) 2018 VyOS maintainers and contributors
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 or later as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+#
+
+import sys
+import os
+import ipaddress
+
+import jinja2
+
+import vyos.validate
+
+from vyos.config import Config
+from vyos import ConfigError
+
+config_file = r'/etc/dhcp/dhcpd6.conf'
+lease_file = r'/config/dhcpd6.leases'
+daemon_config_file = r'/etc/default/isc-dhcpv6-server'
+
+# Please be careful if you edit the template.
+config_tmpl = """
+### Autogenerated by dhcpv6_server.py ###
+
+# For options please consult the following website:
+# https://www.isc.org/wp-content/uploads/2017/08/dhcp43options.html
+
+log-facility local7;
+{%- if preference %}
+option dhcp6.preference {{ preference }};
+{%- endif %}
+
+# Shared network configration(s)
+{% for network in shared_network %}
+{%- if not network.disabled -%}
+shared-network {{ network.name }} {
+    {%- for subnet in network.subnet %}
+    subnet6 {{ subnet.network }} {
+        {%- for range in subnet.range6_prefix %}
+        range6 {{ range.prefix }}{{ " temporary" if range.temporary }};
+        {%- endfor %}
+        {%- for range in subnet.range6 %}
+        range6 {{ range.start }} {{ range.stop }};
+        {%- endfor %}
+        {%- if subnet.domain_search %}
+        option dhcp6.domain-search {{ subnet.domain_search | join(', ') }};
+        {%- endif %}
+        {%- if subnet.lease_def %}
+        default-lease-time {{ subnet.lease_def }};
+        {%- endif %}
+        {%- if subnet.lease_max %}
+        max-lease-time {{ subnet.lease_max }};
+        {%- endif %}
+        {%- if subnet.lease_min %}
+        min-lease-time {{ subnet.lease_min }};
+        {%- endif %}
+        {%- if subnet.dns_server %}
+        option dhcp6.name-servers {{ subnet.dns_server | join(', ') }};
+        {%- endif %}
+        {%- if subnet.nis_domain %}
+        option dhcp6.nis-domain-name "{{ subnet.nis_domain }}";
+        {%- endif %}
+        {%- if subnet.nis_server %}
+        option dhcp6.nis-servers {{ subnet.nis_server | join(', ') }};
+        {%- endif %}
+        {%- if subnet.nisp_domain %}
+        option dhcp6.nisp-domain-name "{{ subnet.nisp_domain }}";
+        {%- endif %}
+        {%- if subnet.nisp_server %}
+        option dhcp6.nisp-servers {{ subnet.nisp_server | join(', ') }};
+        {%- endif %}
+        {%- if subnet.sip_address %}
+        option dhcp6.sip-servers-addresses {{ subnet.sip_address | join(', ') }};
+        {%- endif %}
+        {%- if subnet.sip_hostname %}
+        option dhcp6.sip-servers-names {{ subnet.sip_hostname | join(', ') }};
+        {%- endif %}
+        {%- if subnet.sntp_server %}
+        option dhcp6.sntp-servers {{ subnet.sntp_server | join(', ') }};
+        {%- endif %}
+        {%- for host in subnet.static_mapping %}
+        {% if not host.disabled -%}
+        host {{ network.name }}_{{ host.name }} {
+            host-identifier option dhcp6.client-id "{{ host.client_identifier }}";
+            fixed-address6 {{ host.ipv6_address }};
+        }
+        {%- endif %}
+        {%- endfor %}
+    }
+    {%- endfor %}
+}
+{%- endif %}
+{% endfor %}
+
+"""
+
+daemon_tmpl = """
+### Autogenerated by dhcp_server.py ###
+
+# sourced by /etc/init.d/isc-dhcpv6-server
+
+DHCPD_CONF=/etc/dhcp/dhcpd6.conf
+DHCPD_PID=/var/run/dhcpd6.pid
+OPTIONS="-6 -lf {{ lease_file }}"
+INTERFACES=""
+"""
+
+default_config_data = {
+    'lease_file': lease_file,
+    'preference': '',
+    'disabled': False,
+    'shared_network': []
+}
+
+def get_config():
+    dhcpv6 = default_config_data
+    conf = Config()
+    if not conf.exists('service dhcpv6-server'):
+        return None
+    else:
+        conf.set_level('service dhcpv6-server')
+
+    # Check for global disable of DHCPv6 service
+    if conf.exists('disable'):
+        dhcpv6['disabled'] = True
+        return dhcpv6
+
+    # Preference of this DHCPv6 server compared with others
+    if conf.exists('preference'):
+        dhcpv6['preference'] = conf.return_value('preference')
+
+    # check for multiple, shared networks served with DHCPv6 addresses
+    if conf.exists('shared-network-name'):
+        for network in conf.list_nodes('shared-network-name'):
+            conf.set_level('service dhcpv6-server shared-network-name {0}'.format(network))
+            config = {
+                'name': network,
+                'disabled': False,
+                'subnet': []
+            }
+
+            # If disabled, the shared-network configuration becomes inactive
+            if conf.exists('disable'):
+                config['disabled'] = True
+
+            # check for multiple subnet configurations in a shared network
+            if conf.exists('subnet'):
+                for net in conf.list_nodes('subnet'):
+                    conf.set_level('service dhcpv6-server shared-network-name {0} subnet {1}'.format(network, net))
+                    subnet = {
+                        'network': net,
+                        'range6_prefix': [],
+                        'range6': [],
+                        'default_router': '',
+                        'dns_server': [],
+                        'domain_name': '',
+                        'domain_search': [],
+                        'lease_def': '',
+                        'lease_min': '',
+                        'lease_max': '',
+                        'nis_domain': '',
+                        'nis_server': [],
+                        'nisp_domain': '',
+                        'nisp_server': [],
+                        'sip_address': [],
+                        'sip_hostname': [],
+                        'sntp_server': [],
+                        'static_mapping': []
+                    }
+
+                    # For any subnet on which addresses will be assigned dynamically, there must be at
+                    # least one address range statement. The range statement gives the lowest and highest
+                    # IP addresses in a range. All IP addresses in the range should be in the subnet in
+                    # which the range statement is declared.
+                    if conf.exists('address-range prefix'):
+                        for prefix in conf.list_nodes('address-range prefix'):
+                            range = {
+                                'prefix': prefix,
+                                'temporary': False
+                            }
+
+                            # Address range will be used for temporary addresses
+                            if conf.exists('address-range prefix {0} temporary'.format(range['prefix'])):
+                                range['temporary'] = True
+
+                            # Append to subnet temporary range6 list
+                            subnet['range6_prefix'].append(range)
+
+                    if conf.exists('address-range start'):
+                        for range in conf.list_nodes('address-range start'):
+                            range = {
+                                'start': range,
+                                'stop': conf.return_value('address-range start {0} stop'.format(range))
+                            }
+
+                            # Append to subnet range6 list
+                            subnet['range6'].append(range)
+
+                    # The domain-search option specifies a 'search list' of Domain Names to be used
+                    # by the client to locate not-fully-qualified domain names.
+                    if conf.exists('domain-search'):
+                        for domain in conf.return_values('domain-search'):
+                            subnet['domain_search'].append('"' + domain + '"')
+
+                    # IPv6 address valid lifetime
+                    #  (at the end the address is no longer usable by the client)
+                    #  (set to 30 days, the usual IPv6 default)
+                    if conf.exists('lease-time default'):
+                        subnet['lease_def'] = conf.return_value('lease-time default')
+
+                    # Time should be the maximum length in seconds that will be assigned to a lease.
+                    # The only exception to this is that Dynamic BOOTP lease lengths, which are not
+                    # specified by the client, are not limited by this maximum.
+                    if conf.exists('lease-time maximum'):
+                        subnet['lease_max'] = conf.return_value('lease-time maximum')
+
+                    # Time should be the minimum length in seconds that will be assigned to a lease
+                    if conf.exists('lease-time minimum'):
+                        subnet['lease_min'] = conf.return_value('lease-time minimum')
+
+                    # Specifies a list of Domain Name System name servers available to the client.
+                    # Servers should be listed in order of preference.
+                    if conf.exists('name-server'):
+                        subnet['dns_server'] = conf.return_values('name-server')
+
+                    # Ancient NIS (Network Information Service) domain name
+                    if conf.exists('nis-domain'):
+                        subnet['nis_domain'] = conf.return_value('nis-domain')
+
+                    # Ancient NIS (Network Information Service) servers
+                    if conf.exists('nis-server'):
+                        subnet['nis_server'] = conf.return_values('nis-server')
+
+                    # Ancient NIS+ (Network Information Service) domain name
+                    if conf.exists('nisplus-domain'):
+                        subnet['nisp_domain'] = conf.return_value('nisplus-domain')
+
+                    # Ancient NIS+ (Network Information Service) servers
+                    if conf.exists('nisplus-server'):
+                        subnet['nisp_server'] = conf.return_values('nisplus-server')
+
+                    # Prefix Delegation (RFC 3633)
+                    if conf.exists('prefix-delegation'):
+                        print('TODO: This option is actually not implemented right now!')
+
+                    # Local SIP server that is to be used for all outbound SIP requests - IPv6 address
+                    if conf.exists('sip-server-address'):
+                        subnet['sip_address'] = conf.return_values('sip-server-address')
+
+                    # Local SIP server that is to be used for all outbound SIP requests - hostname
+                    if conf.exists('sip-server-name'):
+                        for hostname in conf.return_values('sip-server-name'):
+                            subnet['sip_hostname'].append('"' + hostname + '"')
+
+                    # List of local SNTP servers available for the client to synchronize their clocks
+                    if conf.exists('sntp-server'):
+                        subnet['sntp_server'] = conf.return_values('sntp-server')
+
+                    #
+                    # Static DHCP v6 leases
+                    #
+                    if conf.exists('static-mapping'):
+                        for mapping in conf.list_nodes('static-mapping'):
+                            conf.set_level('service dhcpv6-server shared-network-name {0} subnet {1} static-mapping {2}'.format(network, net, mapping))
+                            mapping = {
+                               'name': mapping,
+                               'disabled': False,
+                               'ipv6_address': '',
+                               'client_identifier': '',
+                            }
+
+                            # This static lease is disabled
+                            if conf.exists('disable'):
+                                mapping['disabled'] = True
+
+                            # IPv6 address used for this DHCP client
+                            if conf.exists('ipv6-address'):
+                                mapping['ipv6_address'] = conf.return_value('ipv6-address')
+
+                            # This option specifies the client’s DUID identifier. DUIDs are similar but different from DHCPv4 client identifiers
+                            if conf.exists('identifier'):
+                                mapping['client_identifier'] = conf.return_value('identifier')
+
+                            # append static mapping configuration tu subnet list
+                            subnet['static_mapping'].append(mapping)
+
+                    # append subnet configuration to shared network subnet list
+                    config['subnet'].append(subnet)
+
+
+            # append shared network configuration to config dictionary
+            dhcpv6['shared_network'].append(config)
+
+    return dhcpv6
+
+def verify(dhcpv6):
+    if dhcpv6 is None:
+        return None
+
+    if dhcpv6['disabled']:
+        return None
+
+    # If DHCP is enabled we need one share-network
+    if len(dhcpv6['shared_network']) == 0:
+        raise ConfigError('No DHCPv6 shared networks configured.\n' \
+                          'At least one DHCPv6 shared network must be configured.')
+
+    # Inspect shared-network/subnet
+    subnets = []
+    listen_ok = False
+
+    for network in dhcpv6['shared_network']:
+        # A shared-network requires a subnet definition
+        if len(network['subnet']) == 0:
+            raise ConfigError('No DHCPv6 lease subnets configured for {0}. At least one\n' \
+                              'lease subnet must be configured for each shared network.'.format(network['name']))
+
+        range6_start = []
+        range6_stop = []
+        for subnet in network['subnet']:
+            # Ususal range declaration with a start and stop address
+            for range6 in subnet['range6']:
+                # shorten names
+                start = range6['start']
+                stop = range6['stop']
+
+                # DHCPv6 stop address is required
+                if start and not stop:
+                    raise ConfigError('DHCPv6 range stop address for start {0} is not defined!'.format(start))
+
+                # Start address must be inside network
+                if not ipaddress.ip_address(start) in ipaddress.ip_network(subnet['network']):
+                    raise ConfigError('DHCPv6 range start address {0} is not in subnet {1}\n' \
+                                      'specified for shared network {2}!'.format(start, subnet['network'], network['name']))
+
+                # Stop address must be inside network
+                if not ipaddress.ip_address(stop) in ipaddress.ip_network(subnet['network']):
+                     raise ConfigError('DHCPv6 range stop address {0} is not in subnet {1}\n' \
+                                       'specified for shared network {2}!'.format(stop, subnet['network'], network['name']))
+
+                # Stop address must be greater or equal to start address
+                if not ipaddress.ip_address(stop) >= ipaddress.ip_address(start):
+                    raise ConfigError('DHCPv6 range stop address {0} must be greater or equal\n' \
+                                      'to the range start address {1}!'.format(stop, start))
+
+                # DHCPv6 range start address must be unique - two ranges can't
+                # start with the same address - makes no sense
+                if start in range6_start:
+                    raise ConfigError('Conflicting DHCPv6 lease range:\n' \
+                                      'Pool start address {0} defined multipe times!'.format(start))
+                else:
+                    range6_start.append(start)
+
+                # DHCPv6 range stop address must be unique - two ranges can't
+                # end with the same address - makes no sense
+                if stop in range6_stop:
+                    raise ConfigError('Conflicting DHCPv6 lease range:\n' \
+                                      'Pool stop address {0} defined multipe times!'.format(stop))
+                else:
+                    range6_stop.append(stop)
+
+            # We also have prefixes that require checking
+            for prefix in subnet['range6_prefix']:
+                # If configured prefix does not match our subnet, we have to check that it's inside
+                if ipaddress.ip_network(prefix['prefix']) != ipaddress.ip_network(subnet['network']):
+                    # Configured prefixes must be inside our network
+                    if not ipaddress.ip_network(prefix['prefix']) in ipaddress.ip_network(subnet['network']):
+                        raise ConfigError('DHCPv6 prefix {0} is not in subnet {1}\n' \
+                                          'specified for shared network {2}!'.format(prefix['prefix'], subnet['network'], network['name']))
+
+        # DHCPv6 requires at least one configured address range or one static mapping
+        if not network['disabled']:
+            if vyos.validate.is_subnet_connected(subnet['network']):
+                listen_ok = True
+
+        # DHCPv6 subnet must not overlap. ISC DHCP also complains about overlapping
+        # subnets: "Warning: subnet 2001:db8::/32 overlaps subnet 2001:db8:1::/32"
+        net = ipaddress.ip_network(subnet['network'])
+        for n in subnets:
+            net2 = ipaddress.ip_network(n)
+            if (net != net2):
+                if net.overlaps(net2):
+                    raise ConfigError('DHCPv6 conflicting subnet ranges: {0} overlaps {1}'.format(net, net2))
+
+    if not listen_ok:
+        raise ConfigError('None of the DHCPv6 subnets are connected to a subnet6 on\n' \
+                          'this machine. At least one subnet6 must be connected such that\n' \
+                          'DHCPv6 listens on an interface!')
+
+
+    return None
+
+def generate(dhcpv6):
+    if dhcpv6 is None:
+        return None
+
+    if dhcpv6['disabled']:
+        print('Warning: DHCPv6 server will be deactivated because it is disabled')
+        return None
+
+    tmpl = jinja2.Template(config_tmpl)
+    config_text = tmpl.render(dhcpv6)
+    with open(config_file, 'w') as f:
+        f.write(config_text)
+
+    tmpl = jinja2.Template(daemon_tmpl)
+    config_text = tmpl.render(dhcpv6)
+    with open(daemon_config_file, 'w') as f:
+        f.write(config_text)
+
+    return None
+
+def apply(dhcpv6):
+    if (dhcpv6 is None) or dhcpv6['disabled']:
+        # DHCP server is removed in the commit
+        os.system('sudo systemctl stop isc-dhcpv6-server.service')
+        if os.path.exists(config_file):
+            os.unlink(config_file)
+        if os.path.exists(daemon_config_file):
+            os.unlink(daemon_config_file)
+    else:
+        # If our file holding DHCPv6 leases does yet not exist - create it
+        if not os.path.exists(lease_file):
+            os.mknod(lease_file)
+
+        os.system('sudo systemctl restart isc-dhcpv6-server.service')
+
+    return None
+
+if __name__ == '__main__':
+    try:
+        c = get_config()
+        verify(c)
+        generate(c)
+        apply(c)
+    except ConfigError as e:
+        print(e)
+        sys.exit(1)