Build dhcpd.conf based on information in LDAP, using erb templating in puppet.

dhcpd.conf.erb

# file managed by puppet
<%# Copyright (c) 2013, ZenRobotics Ltd. All rights reserved. %>
<%
require 'ipaddr'
raise Puppet::Error, 'Could not set up LDAP Connection: Missing ruby/ldap libraries' unless Puppet.features.ldap?

conn = Puppet::Util::Ldap::Connection.instance
conn.start
connection = conn.connection
base = Puppet.settings[:ldapbase]
filter = '(&(objectClass=dhcpServer)(cn=%s))' % @dhcp_server_cn
dn = nil

connection.search(base, LDAP::LDAP_SCOPE_SUBTREE, filter,
                  'dhcpServiceDN') do |server|
  dns = server.vals('dhcpServiceDN')

  if dns.nil? or dns.size != 1
    raise Puppet::Error, 'Could not find dhcpServiceDN for %s' % @dhcp_server_cn
  else
    dn = server.vals('dhcpServiceDN')[0]
  end
end

connection.search(dn, LDAP::LDAP_SCOPE_BASE, '(objectClass=dhcpService)',
                  ['dhcpStatements', 'dhcpOption']) do |service|
  statements = service.vals('dhcpStatements')
  if !statements.nil?
    statements.each do |statement|
-%>
<%= statement %>;
<%
    end # statements.each
  end # if statements

  options = service.vals('dhcpOption')
  if !options.nil?
    options.each do |option|
-%>
option <%= option %>;
<%
    end # options.each
  end # if options

  connection.search(dn, LDAP::LDAP_SCOPE_SUBTREE, '(objectClass=dhcpSubnet)',
                    ['cn', 'dhcpNetMask', 'dhcpStatements',
                      'dhcpOption']) do |subnet|
    cn = subnet.vals('cn')[0]
    cidr = subnet.vals('dhcpNetMask')[0]
    ipaddr = IPAddr.new('0.0.0.0/' + cidr).inspect
    netmask = ipaddr[ipaddr.index('/')+1..ipaddr.index('>')-1]

-%>
subnet <%= cn %> netmask <%= netmask %> {
<%
    statements = subnet.vals('dhcpStatements')
    if !statements.nil?
      statements.each do |statement|
-%>
<%= statement %>;
<%
      end # statements.each
    end # if statements

    options = subnet.vals('dhcpOption')
    if !options.nil?
      options.each do |option|
-%>
option <%= option %>;
<%
      end # options.each
    end # if options

    connection.search(subnet.dn, LDAP::LDAP_SCOPE_SUBTREE,
                      '(objectClass=dhcpHost)', ['cn', 'dhcpHWAddress',
                        'dhcpStatements', 'dhcpOption']) do |host|
      cn = host.vals('cn')[0]
-%>
host <%= cn %> {
<%
      hardware = host.vals('dhcpHWAddress')
      if !hardware.nil?
-%>
hardware <%= hardware[0] %>;
<%
      end # if hardware

      statements = host.vals('dhcpStatements')
      if !statements.nil?
        statements.each do |statement|
-%>
<%= statement %>;
<%
        end # statements.each
      end # if statements

      options = host.vals('dhcpOption')
      if !options.nil?
        options.each do |option|
-%>
option <%= option %>;
<%
        end # options.each
      end # if options
-%>
}
<%
    end # host

    connection.search(subnet.dn, LDAP::LDAP_SCOPE_SUBTREE,
                      '(objectClass=dhcpPool)', ['dhcpRange']) do |pool|
      range = pool.vals('dhcpRange')[0]
-%>
pool {
range <%= range %>;
}
<%
    end # pool
-%>
}
<%
  end # subnet
end # service
-%>