path: root/dhcp-model.lua

-- acf model for /etc/dhcp/*
-- Copyright(c) 2007 A. Brodmann - Licensed under terms of GPL2
module (..., package.seeall)

--- get additional libraries
require("validator")

local subnet = {}
local cfgdir = "/etc/dhcp/"

--- the tokenizer functions - must be dislocated into a library later
tokenizer = {}

tokenizer.new = function( str, delim )
   local token = {}
   token.value = str;
   token.delim = delim;
   token.pos   = 1
   return token
end
               
tokenizer.pos = function( value, substr, pos )
   local retval = pos
   local done = false
   while not done and retval <= #value do
      if string.sub( value, retval, retval ) == substr then
         done = true
      else
         retval = retval + 1
      end
   end
                                                            
   return retval
end
                                                                  
tokenizer.next = function( token )
   if token.pos > #token.value then
      return token, nil
   end
                                                                           
   local strpos = tokenizer.pos( token.value, token.delim, token.pos )
   retval = string.sub(token.value, token.pos, strpos-1)
   if retval == token.delim then
      retval = ""
      token.pos = token.pos + 1
   else
      token.pos = strpos + 1
   end
                                                                                                               
   return token, retval
end
---

dep_check = function ()

	icode = 0
	retval = {}

	lpos = require "posix"
	ptr, msg, code = lpos.access("/etc/dhcp")
	if ptr == nil then
		table.insert(retval, "/etc/dhcp")
		icode = icode + 1
	end
	
	ptr, msg, code = lpos.access("/usr/sbin/dhcpd")
	if ptr == nil then
		table.insert(retval, "/usr/sbin/dhcpd")
		icode = icode + 1
	end
	
	ptr, msg, code = lpos.access("/etc/init.d/dhcpd")
	if ptr == nil then
		table.insert(retval, "/etc/init.d/dhcpd")
		icode = icode + 1
	end

	if icode == 0 then
		retval = nil
	end	
	
	return retval
end

config_generate = function()

	msg = ""
	tmpfilename = os.tmpname()
	
	-- create tmp config file
	local tmpfile = io.open( tmpfilename, "w+" )
	
	-- get, validate and write global settings to tmp config file
	settings = read_settings()
	s_msg, s_fields = validate_settings( settings )
	if #s_msg > 0 then
		tmpfile:close()
		os.remove( tmpfilename )
		msg = "Configuration Generation Failed!\n\n" ..
		      "Reason: Error in Global Settings\n"
		return msg
	end
	
	tmpfile:write( "authoritative;\n" )
	tmpfile:write( "ddns-update-style none;\n\n" )
	tmpfile:write( "option local-wpad-server code 252 = text;\n\n" )
	if #settings.domainname.value > 0 then
		tmpfile:write( "option domain-name \"" .. settings.domainname.value .. "\";\n" )
	end
	tmpfile:write( "default-lease-time " .. settings.defleasetime.value .. ";\n" )
	tmpfile:write( "max-lease-time " .. settings.maxleasetime.value .. ";\n\n" )
	
	-- get, validate and write subnet configurations to tmp config file
	subnets = get_subnets()
	local numnetworks = 0
	for k,v in ipairs(subnets) do
	        numnetworks = numnetworks + 1
		net = subnet_read( v )
		sn_msg, sn_fields = validate_network( net )
		if #sn_msg > 0 then
			tmpfile:close()
			os.remove( tmpfilename )
			msg = "Configuration Generation Failed!\n\n" ..
			      "Reason: Error in Subnet '" .. v .. "'\n"
			return msg
		end

		tmpfile:write( "# " .. net.name.value .. "\n" )		
		tmpfile:write( "subnet " .. net.subnet.value .. " netmask " .. net.netmask.value .. " {\n" )
		if #net.defleasetime.value > 0 then
			tmpfile:write( "  default-lease-time " .. net.defleasetime.value .. ";\n" )
		end
		if #net.maxleasetime.value > 0 then
			tmpfile:write( "  max-lease-time " .. net.maxleasetime.value .. ";\n" )
		end
		tmpfile:write( "  option routers " .. net.gateway.value .. ";\n" )
		dnssrvrs = ""
		if #net.dnssrv1.value > 0 then
			dnssrvrs = net.dnssrv1.value
		end
		if #net.dnssrv2.value > 0 then
			if #dnssrvrs > 0 then
				dnssrvrs = dnssrvrs .. ", " .. net.dnssrv2.value
			else
				dnssrvrs = net.dnssrv2.value
			end
		end
		if #dnssrvrs > 0 then
			tmpfile:write( "  option domain-name-servers " .. dnssrvrs .. ";\n" )
		end
		if #net.domainname.value > 0 then
			tmpfile:write( "  option domain-name \"" .. net.domainname.value .. "\";\n" )
		end
		if #net.wpad.value > 0 then
			tmpfile:write( "  option local-wpad-server \"" .. net.wpad.value .. "\\n\";\n" )
		end
		spec2_msg = generate_pool( tmpfile, tmpfilename, net )
		if #spec2_msg > 0 then
			tmpfile:close()
			os.remove( tmpfilename )
			msg = "Configuration Generation Failed!\n\n" .. spec2_msg
			return msg
		end
		spec2_msg = generate_hosts( tmpfile, tmpfilename, net )
		if #spec2_msg > 0 then
			tmpfile:close()
			os.remove( tmpfilename )
			msg = "Configuration Generation Failed!\n\n" .. spec2_msg
			return msg
		end
		--- generate advanced part / drop in
		advancedfile = io.open( cfgdir .. net.name.value .. ".advanced", "r" )
		if advancedfile ~= nil then
			advanceddata = advancedfile:read( "*a" )
			advancedfile:close()
			if advanceddata == nil then
				advancedfile:close()
				msg = "Configuration Generation Failed!\n\n" ..
				      "Reason: failed to read advanced file for '" .. net.name.value .. "'"
				return msg
			end
			tmpfile:write( advanceddata .. "\n" )
		end
		---
	
		tmpfile:write( "}\n\n" )
	end
	
	if numnetworks <= 0 then
		tmpfile:close()
		os.remove( tmpfilename )
		msg = "Configuration Generation Failed!\n\n" ..
		      "Reason: No Subnets defined!\n"
		return msg
	end
	
	tmpfile:close()
	os.rename( tmpfilename, "/etc/dhcp/dhcpd.conf" )
	
	return "Configuration Generation Successful!\n"
end

generate_pool = function( tmpfile, tmpfilename, net )
	if not validator.is_ipv4( net.leaserangestart.value ) or
	   not validator.is_ipv4( net.leaserangeend.value ) then
	   if net.unknownclients.value == "permit" then
	   	msg = "Reason: permitted unknown clients but failed to define lease range!\n"
	   	return msg
	   end
	   
	   return ""
	end

	--- pool header 
	tmpfile:write( "  pool {\n" )
	if net.unknownclients.value == "permit" then
		tmpfile:write( "    permit known clients;\n" )
		tmpfile:write( "    permit unknown clients;\n" )
	else
		tmpfile:write( "    permit known clients;\n" )
		tmpfile:write( "    deny unknown clients;\n" )
	end
	tmpfile:write( "    range " .. net.leaserangestart.value .. " " .. net.leaserangeend.value .. ";\n" )
	tmpfile:write( "  }\n" )
	
	return ""
end

generate_hosts = function( tmpfile, tmpfilename, net )
	--- generate static hosts
	statichostsfile = io.open( cfgdir .. net.name.value .. ".static", "r" )
	if statichostsfile ~= nil then
		statichosts = statichostsfile:read( "*a" )
		if statichosts == nil then
			statichostsfile:close()
			msg = "Configuration Generation Failed!\n\n" ..
			      "Reason: failed to read static hosts file for '" .. net.name.value .. "'"
			return msg
		end
		msg = validate_statichosts( statichosts )
		if #msg > 0 then
			statichostsfile:close()
			msg = "Configuration Generation Failed!\n\n" ..
			      "Reason: " .. msg
			return msg
		end
	
		--- loop through all hosts
		done = false
		hosttoken = tokenizer.new( statichosts, "\n" )
		while not done do
			hosttoken, nexthost = tokenizer.next( hosttoken )
			if nexthost ~= nil then
				if string.sub( nexthost, 1, 1) ~= "#" then
					spectoken = tokenizer.new( nexthost, ";" )
					spectoken, hostname  = tokenizer.next( spectoken )
					spectoken, ip  = tokenizer.next( spectoken )
					spectoken, mac  = tokenizer.next( spectoken )
					spectoken, comment  = tokenizer.next( spectoken )
					tmpfile:write("  host " .. hostname .. " {\n")
					tmpfile:write("    hardware ethernet " .. mac .. ";\n")
					tmpfile:write("    fixed-address " .. ip .. ";\n")
					tmpfile:write("  }\n")
				end
			else
				done = true
			end
		end
		statichostsfile:close()
	end
	---

        if net.unknownclients.value == "permit" then
        	return ""
        end
	--- generate dynamic hosts
	dynamichostsfile = io.open( cfgdir .. net.name.value .. ".dynamic", "r" )
	if dynamichostsfile ~= nil then
		dynamichosts = dynamichostsfile:read( "*a" )
		if dynamichosts == nil then
			dynamichostsfile:close()
			msg = "Configuration Generation Failed!\n\n" ..
			      "Reason: failed to read dynamic hosts file for '" .. net.name.value .. "'"
			return msg
		end
		msg = validate_dynamichosts( dynamichosts )
	
		--- loop through all hosts
		done = false
		hosttoken = tokenizer.new( dynamichosts, "\n" )
		while not done do
			hosttoken, nexthost = tokenizer.next( hosttoken )
			if nexthost ~= nil then
				if string.sub( nexthost, 1, 1) ~= "#" then
					spectoken = tokenizer.new( nexthost, ";" )
					spectoken, hostname  = tokenizer.next( spectoken )
					spectoken, mac  = tokenizer.next( spectoken )
					spectoken, comment  = tokenizer.next( spectoken )
					tmpfile:write("  host " .. hostname .. " {\n")
					tmpfile:write("    hardware ethernet " .. mac .. ";\n")
					tmpfile:write("  }\n")
				end
			else
				done = true
			end
		end
		dynamichostsfile:close()
	end
	---
	
	return ""
end

subnet_delete = function( name )

	local msg = ""

	local filename = cfgdir .. name
	os.remove( filename .. ".subnet" )
	os.remove( filename .. ".static" )
	os.remove( filename .. ".dynamic" )

	return msg
end

subnet_read = function( name )
	local filename = cfgdir .. name .. ".subnet"
	local net = create_new_net( name, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil )

	for line in io.lines(filename) do
		if (string.sub(line, 1, 15) == "def-lease-time:") then
			net.defleasetime.value = string.sub(line, 17)
		elseif (string.sub(line, 1, 15) == "max-lease-time:") then
			net.maxleasetime.value = string.sub(line, 17)
		elseif (string.sub(line, 1, 8) == "gateway:") then
			net.gateway.value = string.sub(line, 10)
		elseif (string.sub(line, 1, 12) == "domain-name:") then
			net.domainname.value = string.sub(line, 14)
		elseif (string.sub(line, 1, 10) == "dns-srv-1:") then
			net.dnssrv1.value = string.sub(line, 12)
		elseif (string.sub(line, 1, 10) == "dns-srv-2:") then
			net.dnssrv2.value = string.sub(line, 12)
		elseif (string.sub(line, 1, 7) == "subnet:") then
			net.subnet.value = string.sub(line, 9)
		elseif (string.sub(line, 1, 8) == "netmask:") then
			net.netmask.value = string.sub(line, 10)
		elseif (string.sub(line, 1, 18) == "lease-range-start:") then
			net.leaserangestart.value = string.sub(line, 20)
		elseif (string.sub(line, 1, 16) == "lease-range-end:") then
			net.leaserangeend.value = string.sub(line, 18)
		elseif (string.sub(line, 1, 5) == "wpad:") then
			net.wpad.value = string.sub(line, 7)
		elseif (string.sub(line, 1, 16) == "unknown-clients:") then
			net.unknownclients.value = string.sub(line, 18)
		end
	end
	if net.unknownclients.value ~= "permit" then
		net.unknownclients.value = "deny"
	end
	
	net.statichosts.value = subnet_get_spechosts( name, "static" )
	net.dynamichosts.value = subnet_get_spechosts( name, "dynamic" )
	net.advanced.value = subnet_get_spechosts( name, "advanced" )
	
	return net
end

subnet_get_spechosts = function( name, suffix )
        local retval = ""
	local filename = cfgdir .. name .. "." .. suffix
	if file_exists( filename ) then
		local file = io.open( filename, "r" )
		if file ~= nil then
			msg = file:read( "*a" )
			if msg ~= nil then
				retval = msg
			end
			file:close()
		end
	end
	
	return retval
end

subnet_update_statichosts = function( name, statichosts )
	local msg = "";
	local filename = cfgdir .. name .. ".static"
	
	file, errmsg = io.open( filename, "wb+" )
	if file == nil then
		msg = "Error: Failed to open " .. filename .. "(" .. errmsg .. ")!"
	else 
		file:write( statichosts )
		file:close()
	end
	
	return msg
end

subnet_update_dynamichosts = function( name, dynamichosts )
	local msg = "";
	local filename = cfgdir .. name .. ".dynamic"
	
	file, errmsg = io.open( filename, "wb+" )
	if file == nil then
		msg = "Error: Failed to open " .. filename .. "(" .. errmsg .. ")!"
	else 
		file:write( dynamichosts )
		file:close()
	end
	
	return msg
end

subnet_update_advanced = function( name, advanced )
	local msg = "";
	local filename = cfgdir .. name .. ".advanced"
	
	file, errmsg = io.open( filename, "wb+" )
	if file == nil then
		msg = "Error: Failed to open " .. filename .. "(" .. errmsg .. ")!"
	else
		file:write( advanced )
		file:close()
	end
	
	return msg
end

read_settings = function()
	local filename = cfgdir .. "globalsettings.conf"
	local settings = create_new_settings( nil, nil, nil )
	if file_exists( filename ) then
		for line in io.lines(filename) do
			if (string.sub(line, 1, 15) == "def-lease-time:") then
				settings.defleasetime.value = string.sub(line, 17)
			elseif (string.sub(line, 1, 15) == "max-lease-time:") then
				settings.maxleasetime.value = string.sub(line, 17)
			elseif (string.sub(line, 1, 12) == "domain-name:") then
				settings.domainname.value = string.sub(line, 14)
			end
		end
	end
	
	return settings
end

subnet_write = function( net )
	msg, fields = validate_network( net )
	if #msg > 0 then
		return cfe({ msg = msg, fields = fields }), net
	end
	local filename = cfgdir .. net.name.value .. ".subnet"
	local file = io.open( filename, "w+" )
	file:write( "def-lease-time: " .. net.defleasetime.value .. "\n" )
	file:write( "max-lease-time: " .. net.maxleasetime.value .. "\n" )
	file:write( "gateway: " .. net.gateway.value .. "\n" )
	file:write( "domain-name: " .. net.domainname.value .. "\n" )
	file:write( "dns-srv-1: " .. net.dnssrv1.value .. "\n" )
	file:write( "dns-srv-2: " .. net.dnssrv2.value .. "\n" )
	file:write( "subnet: " .. net.subnet.value .. "\n" )
	file:write( "netmask: " .. net.netmask.value .. "\n" )
	file:write( "lease-range-start: " .. net.leaserangestart.value .. "\n" )
	file:write( "lease-range-end: " .. net.leaserangeend.value .. "\n" )
	file:write( "wpad: " .. net.wpad.value .. "\n" )
	file:write( "unknown-clients: " .. net.unknownclients.value .. "\n" )
	file:close()
	
	spec_msg = validate_statichosts( net.statichosts.value )
	if #spec_msg == 0 then
		spec_msg = subnet_update_statichosts( net.name.value, net.statichosts.value )
		if #spec_msg > 0 then
			msg = spec_msg
			table.insert( fields, "statichosts" )
		end
	else
		msg = spec_msg
		table.insert( fields, "statichosts" )
	end

        if net.unknownclients.value == "deny" then
		spec_msg = validate_dynamichosts( net.dynamichosts.value )
		if #spec_msg == 0 then
			spec_msg = subnet_update_dynamichosts( net.name.value, net.dynamichosts.value )
			if #spec_msg > 0 then
				msg = spec_msg
				table.insert( fields, "dynamichosts" )
			end
		else
			msg = spec_msg
			table.insert( fields, "dynamichosts" )
		end
	end
	
	spec_msg = subnet_update_advanced( net.name.value, net.advanced.value )
	if #spec_msg > 0 then
		msg = spec_msg
		table.insert( fields, "advanced" )
	end
	
	return cfe({ msg = msg, fields = {}}), net
end

validate_statichosts = function( statichosts )
	local line = 1
	local msg = ""
	local done = false
	hosttoken = tokenizer.new( statichosts, "\n")
	while not done do
		hosttoken, nexthost = tokenizer.next( hosttoken )
		if nexthost ~= nil then
			if string.sub(nexthost, 1, 1) ~= "#" then
				fieldtoken = tokenizer.new( nexthost, ";")
				fieldtoken, hostname = tokenizer.next( fieldtoken )
				fieldtoken, ip = tokenizer.next( fieldtoken )
				fieldtoken, mac = tokenizer.next( fieldtoken )
				fieldtoken, comment = tokenizer.next( fieldtoken )
				if hostname == nil then
					msg = msg .. "Static Hosts: hostname missing on line " .. line .. "!\n"
				else 
					if not is_valid_hostname( hostname ) then
						msg = msg .. "Static Hosts: Invalid hostname on line " .. line .. "!\n"
					end
				end
				if ip == nil then
					msg = msg .. "Static Hosts: ip missing on line " .. line .. "!\n"
				else 
					if not validator.is_ipv4( ip ) then
						msg = msg .. "Static Hosts: Invalid ip on line " .. line .. "!\n"
					end
				end
				if mac == nil then
					msg = msg .. "Static Hosts: mac missing on line " .. line .. "!\n"
				else 
					if not validator.is_mac( mac ) then
						msg = msg .. "Static Hosts: Invalid mac on line " .. line .. "!\n"
					end
				end
			end
			line = line + 1
		else
			done = true
		end
	end

	return msg
end

validate_dynamichosts = function( dynamichosts )
	local line = 1
	local msg = ""
	local done = false
	hosttoken = tokenizer.new( dynamichosts, "\n")
	while not done do
		hosttoken, nexthost = tokenizer.next( hosttoken )
		if nexthost ~= nil then
			if string.sub(nexthost, 1, 1) ~= "#" then
				fieldtoken = tokenizer.new( nexthost, ";")
				fieldtoken, hostname = tokenizer.next( fieldtoken )
				fieldtoken, mac = tokenizer.next( fieldtoken )
				fieldtoken, comment = tokenizer.next( fieldtoken )
				if hostname == nil then
					msg = msg .. "Static Hosts: hostname missing on line " .. line .. "!\n"
				else 
					if not is_valid_hostname( hostname ) then
						msg = msg .. "Static Hosts: Invalid hostname on line " .. line .. "!\n"
					end
				end
				if mac == nil then
					msg = msg .. "Static Hosts: mac missing on line " .. line .. "!\n"
				else 
					if not validator.is_mac( mac ) then
						msg = msg .. "Static Hosts: Invalid mac on line " .. line .. "!\n"
					end
				end
			end
			line = line + 1
		else
			done = true
		end
	end

	return msg
end

update_settings = function ( settings )

	msg, fields = validate_settings ( settings )
	if #msg > 0 then
		return cfe({ msg = msg, fields = fields }), settings
	end
	local filename = cfgdir .. "globalsettings.conf"
	local file = io.open( filename, "w+" )
	file:write( "def-lease-time: " .. settings.defleasetime.value .. "\n" )
	file:write( "max-lease-time: " .. settings.maxleasetime.value .. "\n" )
	file:write( "domain-name: " .. settings.domainname.value .. "\n" )
	return cfe({ msg = "", fields = {}}), settings
end


subnet_create = function( net )
	if file_exists( cfgdir .. net.name.value .. ".subnet" ) then
		return cfe({ msg = "This subnet already exists!", fields = {}}), net
	end
	retcode, net = subnet_write( net )	
	return retcode, net
end

_tonumber = function( value )
	ret = tonumber( value )
	if (ret == nil) then
		ret = 0
	end
	return ret
end

validate_network = function( net )
	fields = {}
	msg = ""
	if #net.name.value < 3 then
		table.insert(fields, "name")
		msg = msg .. "Minimum network name length is 3 characters!\n"
	end
	if not is_valid_netname( net.name.value ) then
		table.insert( fields, "name" )
		msg = msg .. "Invalid network name: allowed characters are: 'a..z', '0..9', '-'\n"
	end
	if net.name.value == "<new>" then
		table.insert(fields, "name")
		msg = msg .. "&lt;new&gt; is not a valid network name!\n"
	end
	if #net.defleasetime.value > 0 then
		if not validator.is_integer_in_range(_tonumber(net.defleasetime.value), 1800, 86400) then
			table.insert(fields, "defleasetime")
			msg = msg .. "Default-Lease-Time must be: 1800 < x < 86400\n"
		end
	end
	if #net.maxleasetime.value > 0 then
		if not validator.is_integer_in_range(_tonumber(net.maxleasetime.value), 1800, 86400) then
			table.insert(fields, "maxleasetime")
			msg = msg .. "Maximum-Lease-Time must be: 1800 < x < 86400\n"
		end
	end
	if not validator.is_ipv4(net.gateway.value) then
		table.insert(fields, "gateway")
		msg = msg .. "Gateway: invalid IPv4 address!\n"
	end
	if #net.dnssrv1.value > 0 then
		if not validator.is_ipv4(net.dnssrv1.value) then
			table.insert(fields, "dnssrv1")
			msg = msg .. "DNS Server 1: invalid IPv4 address!\n"
		end
	end
	if not validator.is_ipv4(net.dnssrv2.value) then
		if #net.dnssrv2.value > 0 then
			table.insert(fields, "dnssrv2")
			msg = msg .. "DNS Server 2: invalid IPv4 address!\n"
		end
	end
	if not validator.is_ipv4(net.subnet.value) then
		table.insert(fields, "subnet")
		msg = msg .. "Subnet: invalid IPv4 address!\n"
	end
	if not validator.is_ipv4(net.netmask.value) then
		table.insert(fields, "netmask")
		msg = msg .. "Netmask: invalid IPv4 address!\n"
	end
	if #net.leaserangestart.value > 0 then
		if not validator.is_ipv4(net.leaserangestart.value) then
			table.insert(fields, "leaserangestart")
			msg = msg .. "Lease-Range-Start: invalid IPv4 address!\n"
		end
	end
	if #net.leaserangeend.value > 0 then
		if not validator.is_ipv4(net.leaserangeend.value) then
			table.insert(fields, "leaserangeend")
			msg = msg .. "Lease-Range-End: invalid IPv4 address!\n"
		end
	end

	return msg, fields
end

file_exists = function( filename )
	retval = false
	lpos = require "posix"
	ptr, msg, code = lpos.access( filename )
	if ptr ~= nil then
		retval = true
	end
	return retval
end

read_file = function ( filename )
	local contents = ""
        local line = ""
	local file = io.open( filename, "r" )
	if file ~= nil then
	        line = file:read( "*l" )
	        while line ~= nil do
			contents = contents .. "\n" .. line
			line = file:read( "*l" )
		end
		file:close()
	else
		contents = "\n   Error: File not found!\n\n"
	end

	return contents
end

is_running = function( process )
	local retval = false
	local file = io.popen("pidof " .. process)
	if file ~= nil then
		local line = file:read( "*l" )
		file:close()
		if #line > 0 then
			retval = true
		end
	end
	
	return retval
end

get_dhcpd_version = function()
	local retval = "dhcpd"
	local file = io.popen("/usr/sbin/dhcpd --version 2>&1")
	if file ~= nil then
		local line = file:read( "*a" )
		if #line > 0 then
			retval = line
		end
		file:close()
	end

	return retval
end

service_control = function ( command ) 

	local retval = ""
	local line = ""
	local file = io.popen( "/etc/init.d/dhcpd " .. command .. " 2>&1" )
	if file ~= nil then
		line = file:read( "*l" )
		while line ~= nil do
			retval = retval .. "\n" .. line
			line = file:read( "*l" )
		end
		file:close()
	end

	return retval
end

function nonil( value )
	local retval = ""
	if value ~= nil then
		retval = value
	end
                                        
	return retval
end

get_subnets = function ()
	
	local retval = {}

	lpos = require "posix"
	files = lpos.dir( "/etc/dhcp" )
	for k,v in ipairs(files) do
		if string.sub(v, -7) == ".subnet" then
			table.insert(retval, string.sub(v, 1, -8))
		end
	end
	
	return retval
end

create_new_net = function( name, defleasetime, maxleasetime, gateway, domainname, dnssrv1, dnssrv2, subnet, netmask, leaserangestart, leaserangeend, wpad, statichosts, unknownclients, dynamichosts, advanced, useadvanced )
	net = { name         = { label="Name", value=nonil(name), type="message" },
	        defleasetime = { label="Default Lease Time", value=nonil(defleasetime), type="text" },
	        maxleasetime = { label="Maximum Lease Time", value=nonil(maxleasetime), type="text" },
	        gateway      = { label="Gateway", value=nonil(gateway), type="text" },
	        domainname   = { label="Domainname", value=nonil(domainname), type="text" },
	        dnssrv1      = { label="DNS Server 1", value=nonil(dnssrv1), type="text" },
	        dnssrv2      = { label="DNS Server 2", value=nonil(dnssrv2), type="text" },
	        subnet       = { label="Subnet", value=nonil(subnet), type="text" },
	        netmask      = { label="Netmask", value=nonil(netmask), type="text" },
	        leaserangestart = { label="Lease Range Start", value=nonil(leaserangestart), type="text" },
	        leaserangeend   = { label="Lease Range End", value=nonil(leaserangeend), type="text" },
	        wpad         = { label="Web Proxy Auto Discovery", value=nonil(wpad), type="text" },
	        statichosts    = { label="Static Hosts", value=nonil(statichosts), type="text" },
	        dynamichosts   = { label="Dynamic Hosts", value=nonil(dynamichosts), type="text" },
	        unknownclients = { label="Unknown Clients", value=nonil(unknownclients), type="text" },
	        advanced       = { label="Advanced", value=nonil(advanced), type="text" },
	        useadvanced    = { label="Use Advanced", value=nonil(useadvanced), type="text" }
	      }
	if net.unknownclients.value ~= "permit" then
		net.unknownclients.value = "deny"
	end
	      
	return net
end

create_new_settings = function( defleasetime, maxleasetime, domainname )
	settings = { domainname    = { label="Domainname", type="text", value=nonil(domainname) },
	             defleasetime  = { label="Default Lease Time", type="text", value=nonil(defleasetime) },
	             maxleasetime  = { label="Maximum Lease Time", type="text", value=nonil(maxleasetime) }
	           }
	return settings
end

validate_settings = function ( settings )

	msg = ""
	fields = {}
	
	if not validator.is_integer_in_range(_tonumber(settings.defleasetime.value), 1800, 86400) then
		msg = msg .. "Default Lease Time: Out of range 1800 < x < 86400 or not integer\n"
		table.insert( fields, "defleasetime" )
	end
	if not validator.is_integer_in_range(_tonumber(settings.maxleasetime.value), 1800, 86400) then
		msg = msg .. "Maximum Lease Time: Out of range 1800 < x < 86400 or not integer\n"
		table.insert( fields, "maxleasetime" )
	end
	if not is_valid_hostname( settings.domainname.value ) then
		if #settings.domainname.value > 0 then
			msg = msg .. "Invalid domainname: valid chars are 'a..z', '0..9', '.', '-'\n"
			table.insert( fields, "domainname" )
		end
	end
	
	return msg, fields
end

is_valid_hostname = function ( hostname )

	local retval = true

	name = string.lower( hostname )
	lap = 1
	while lap <= #name do
		chr = string.sub(name, lap, lap)
		if (chr >= "a" and chr <= "z") or
		   (chr >= "0" and chr <= "9") or
		   (chr == ".") or (chr == "-") then
		   
		else
			retval = false
		end
		lap = lap + 1
	end
	
	return retval
end

is_valid_netname = function ( netname )

	local retval = true
	
	name = string.lower( netname )
	lap = 1
	while lap <= #name do
		chr = string.sub( name, lap, lap )
		if (chr >= "a" and chr <= "z") or
		   (chr >= "0" and chr <= "9") or
		   (chr == "-") then
		   
		else
			retval = false
		end
		lap = lap + 1
	end
	
	return retval
end