anchor.diff:      (assertMinimum "DNSLifetimeSec" 0)
     ];
   
  +  checkIpv6Prefix = checkUnitConfig "IPv6Prefix" [
  +    (assertOnlyFields [
  +      "AddressAutoconfiguration"  "OnLink"  "Prefix"
  +      "PreferredLifetimeSec" "ValidLifetimeSec"
  +    ])
  +    (assertValueOneOf "AddressAutoconfiguration" boolValues)
  +    (assertValueOneOf "OnLink" boolValues)
  +    (assertMinimum "PreferredLifetimeSec" 0)
  +    (assertMinimum "ValidLifetimeSec" 0)
  +  ];
  +
  +
     checkDhcpServer = checkUnitConfig "DHCPServer" [
       (assertOnlyFields [
         "PoolOffset" "PoolSize" "DefaultLeaseTimeSec" "MaxLeaseTimeSec"
  
positive.code:             ${attrsToSection def.ipv6PrefixDelegationConfig}
  
            ''}
            ${optionalString (def.dhcpServerConfig != { }) ''
              [DHCPServer]
              ${attrsToSection def.dhcpServerConfig}
  
negative.code:       description = ''
          Each attribute in this set specifies an option in the
          <literal>[IPv6PrefixDelegation]</literal> section of the unit.  See
          <citerefentry><refentrytitle>systemd.network</refentrytitle>
          <manvolnum>5</manvolnum></citerefentry> for details.
        '';
      };
  
      ipv6Prefixes = mkOption {
        default = [];
        example = { AddressAutoconfiguration = true; OnLink = true; };
        type = with types; listOf (submodule ipv6PrefixOptions);
        description = ''
          A list of ipv6Prefix sections to be added to the unit.  See
          <citerefentry><refentrytitle>systemd.network</refentrytitle>
          <manvolnum>5</manvolnum></citerefentry> for details.
        '';
  