diff --git a/src/autodetect_environment.cr b/src/autodetect_environment.cr
new file mode 100644
index 0000000..014ca85
--- /dev/null
+++ b/src/autodetect_environment.cr
@@ -0,0 +1,14 @@
+
+class Autodetect
+	class_property print_autodetect : Bool = false
+
+	def self.which(cmd : String)
+		if Process.run("which", [ cmd ]).success?
+			puts "#{cmd} installed" if print_autodetect
+			true
+		else
+			puts "#{cmd} not installed" if print_autodetect
+			false
+		end
+	end
+end
diff --git a/src/cli.cr b/src/cli.cr
new file mode 100644
index 0000000..d4d07b5
--- /dev/null
+++ b/src/cli.cr
@@ -0,0 +1,170 @@
+
+file_option : String? = nil
+
+OptionParser.parse! do |parser|
+	parser.on "-s", "--simulation", "Export the network configuration." do
+		Context.simulation = true
+	end
+
+	parser.on "-a", "--print-autodetect", "Print autodetection of the installed programs." do
+		Context.print_autodetect = true
+	end
+
+	parser.on "-w wireless-configuration-program", "--wireless wireless-configuration-program", "iw" do |prog|
+		Context.prefered_wireless_configuration_program = prog
+	end
+
+	parser.on "-n network-configuration-program", "--net-conf network-configuration-program", "ifconfig | ip" do |prog|
+		Context.prefered_network_configuration_program = prog
+	end
+
+	parser.on "-d dhcp-client-program", "--dhcp-client dhcp-client-program", "udhcpc | dhclient" do |prog|
+		Context.prefered_dhcp_client = prog
+	end
+
+	parser.on "-r root", "--root root", "Root where to search for <root>/etc/hostname.* files." do |optsn|
+		Context.root = optsn
+	end
+
+	parser.on "-f file", "--file file", "Parse a configuration file." do |optsn|
+		file_option = optsn
+	end
+
+	# 0: nothing is printed, 1: only events, 2: events and messages
+	parser.on "-v verbosity", "--verbosity verbosity", "Verbosity (0-2). Default: 1" do |optsn|
+		Context.verbosity = optsn.to_i
+	end
+
+	parser.missing_option do |opt|
+		STDERR.puts "You missed the argument for option #{opt}"
+		# TODO: explain the different arguments
+		exit 1
+	end
+
+	parser.invalid_option do |flag|
+		STDERR.puts "Error: #{flag} not a valid option"
+		exit 1
+	end
+
+	parser.unknown_args do |arg|
+		Context.command = arg.shift
+		Context.args = arg
+
+		case Context.command
+		when /^(list)/
+		when /^(up)/
+		when /^(down)/
+		when /^(scan)/
+		else
+			STDERR.puts "Command #{Context.command} not understood"
+			exit 1
+		end
+
+		# unless arg.empty?
+		# 	STDERR.puts "unknown arg: #{arg}"
+		# 	exit 1
+		# end
+	end
+
+	parser.on "-h", "--help", "Show this help" do
+		puts parser
+		exit 0
+	end
+end
+
+
+Do.simulation = Context.simulation
+Autodetect.print_autodetect = Context.print_autodetect
+
+#
+# discover available configuration commands
+#
+
+# ifconfig = *bsd and some linux
+# ip = linux
+possible_network_configuration_cmds = {
+	"ifconfig" => NetworkCommands::IfconfigCommand,
+	"ip"       => NetworkCommands::IPCommand
+}
+
+# udhcpc = busybox dhcp client
+possible_dhcp_clients = {
+	"udhcpc" => NetworkCommands::UDHCPCCommand,
+	"dhclient" => NetworkCommands::DHClientCommand
+}
+
+# iw = linux
+possible_wireless_configuration_cmds = {
+	"iw" => NetworkCommands::IWCommand,
+	"ifconfig" => NetworkCommands::IfconfigCommand
+}
+
+key = Context.prefered_network_configuration_program
+key = possible_network_configuration_cmds.keys.find { |key| Autodetect.which(key) } if key.nil?
+# should crash if there is no network command installed
+NetworkCommands.cmd_network_configuration = possible_network_configuration_cmds[key.not_nil!]
+
+key = Context.prefered_dhcp_client
+key = possible_dhcp_clients.keys.find { |key| Autodetect.which(key) } if key.nil?
+# should not crash if there is no 
+NetworkCommands.cmd_dhcp_client = possible_dhcp_clients[key] unless key.nil?
+
+key = Context.prefered_wireless_configuration_program
+key = possible_wireless_configuration_cmds.keys.find { |key| Autodetect.which(key) } if key.nil?
+# should crash if there is no wireless command installed
+NetworkCommands.cmd_wireless_configuration = possible_wireless_configuration_cmds[key.not_nil!]
+
+
+
+files = Array(String).new
+Dir.children("#{Context.root}/etc/").each do |f|
+	if /^hostname\./.match(f)
+		files << f
+	end
+end
+
+interface_files = Array(String).new
+
+if ! file_option.nil?
+	# file passed via the '-f' option
+	# TODO: why having to force "not_nil!" ? Seems like a compiler bug
+	interface_files << file_option.not_nil!
+elsif Context.args.empty?
+	# every configured interface
+	files.each do |f|
+		interface_files << "#{Context.root}/etc/#{f}"
+	end
+else
+	# only interfaces in arguments
+	Context.args.each do |interface|
+		interface_files << "#{Context.root}/etc/hostname.#{interface}"
+	end
+end
+
+
+
+begin
+	case Context.command
+	when "list"
+		interface_files.each do |f|
+			puts NetworkConfigurationParser.parse_file(f)
+		end
+	when "up"
+		interface_files.each do |f|
+			network_configuration = NetworkConfigurationParser.parse_file(f)
+			network_configuration.execute
+		end
+	when "down"
+		interface_files.each do |f|
+			network_configuration = NetworkConfigurationParser.parse_file(f)
+			network_configuration.down
+		end
+	when "scan"
+		interface_files.each do |f|
+			network_configuration = NetworkConfigurationParser.parse_file(f)
+			network_configuration.scan
+		end
+	end
+rescue e
+	STDERR.puts "#{CRED}Exception: #{CRESET}#{e}"
+end
diff --git a/src/configuration.cr b/src/configuration.cr
new file mode 100644
index 0000000..ebafe4c
--- /dev/null
+++ b/src/configuration.cr
@@ -0,0 +1,292 @@
+
+class NotSetup
+	def to_s(io : IO)
+		io << "not setup"
+	end
+end
+
+class Autoconfiguration
+	def to_s(io : IO)
+		io << "autoconfiguration"
+	end
+end
+
+class DHCP
+	def to_s(io : IO)
+		io << "dhcp"
+	end
+end
+
+
+class WirelessAPSetup
+	property ssid : String
+
+	# This is a list of parameters that should be unique to each AP
+	property up : Bool
+	property description : String?
+	property mtu : Int32?
+	property main_ip_v4 : IPAddress | DHCP | NotSetup
+	property main_ip_v6 : IPAddress | DHCP | Autoconfiguration | NotSetup
+	property aliasses_v4 : Array(IPAddress)
+	property aliasses_v6 : Array(IPAddress)
+	property dns : Array(IPAddress)
+
+	# we currently only support WPA2-PSK wireless security mechanism
+	property security : WPA
+
+	class WPA
+		property key : String
+		def initialize(@key)
+		end
+	end
+
+	def initialize(@ssid, @security)
+		@main_ip_v4 = NotSetup.new
+		@main_ip_v6 = NotSetup.new
+		@aliasses_v4 = Array(IPAddress).new
+		@aliasses_v6 = Array(IPAddress).new
+		@up = true
+		@dns = Array(IPAddress).new
+	end
+
+
+	def to_s(io : IO)
+		io << to_string
+	end
+
+	def to_string
+		String.build do |str|
+			str << "\t#{CBLUE}#{ssid}#{CRESET}\n"
+
+			str << "\t\t#description #{description.not_nil!}\n" unless description.nil?
+			str << "\t\t#{@up? "up" : "down"}\n"
+			str << "\t\tmtu #{mtu}\n" unless mtu.nil?
+
+			# ipv4
+			unless main_ip_v4.is_a?(NotSetup)
+				str << "\t\tinet #{main_ip_v4}\n"
+
+				aliasses_v4.each do |a|
+					str << "\t\talias #{a}\n"
+				end
+			end
+
+			# ipv6
+			unless main_ip_v6.is_a?(NotSetup)
+				str << "\t\tinet6 #{main_ip_v6}\n"
+
+				@aliasses_v6.each do |a|
+					str << "\t\talias6 #{a}\n"
+				end
+			end
+
+			dns.each do |ip|
+				str << "\t\tdns: #{ip}\n"
+			end
+
+			# to improve readability
+			str << "\n"
+		end
+	end
+end
+
+
+#
+# interface configuration
+#
+
+class InterfaceConfiguration
+
+	property name : String
+	property up : Bool
+	property description : String?
+	property mtu : Int32?
+	property wireless : Bool
+	property main_ip_v4 : IPAddress | DHCP | NotSetup
+	property main_ip_v6 : IPAddress | Autoconfiguration | DHCP | NotSetup
+	property aliasses_v4 : Array(IPAddress)
+	property aliasses_v6 : Array(IPAddress)
+	property wireless_networks : Hash(String, WirelessAPSetup)
+	property dns : Array(IPAddress)
+
+	def initialize (@name, @up,
+					@description,
+					@mtu,
+					@main_ip_v4, @main_ip_v6, aliasses,
+					@wireless, @wireless_networks,
+					@dns = Array(IPAddress).new
+				   )
+
+		@aliasses_v4 = Array(IPAddress).new
+		@aliasses_v6 = Array(IPAddress).new
+
+		aliasses.each do |ip|
+			if ip.ipv4?
+				aliasses_v4 << ip
+			else
+				aliasses_v6 << ip
+			end
+		end
+	end
+
+	def to_s(io : IO)
+		io << to_string
+	end
+
+	def to_string
+		String.build do |str|
+			if NetworkCommands.interface_exists(@name)
+				str << "#{CGREEN}#{@name}#{CRESET}\n"
+			else
+				str << "#{CRED}#{@name}#{CRESET}\n"
+			end
+
+			str << "\tdescription: '#{description.not_nil!}'\n" unless description.nil?
+
+			str << "\t#{@up? "up" : "down"}\n"
+
+			unless mtu.nil?
+				str << "\tmtu #{mtu}\n"
+			end
+
+			# ipv4
+			unless main_ip_v4.is_a?(NotSetup)
+				str << "\tinet #{main_ip_v4}\n"
+
+				aliasses_v4.each do |a|
+					str << "\talias #{a}\n"
+				end
+			end
+
+			# warning: alias but no main ip address
+			if main_ip_v4.is_a?(NotSetup) && ! aliasses_v4.empty?
+				str << "\t#{CRED}alias configured but no main ipv4 configuration.#{CRESET}\n"
+				str << "\t#{CRED}Should main ipv4 be obtained from DHCP? Static configuration?#{CRESET}\n"
+			end
+
+			# ipv6
+			unless main_ip_v6.is_a?(NotSetup)
+				str << "\tinet6 #{main_ip_v6}\n"
+
+				aliasses_v6.each do |a|
+					str << "\talias6 #{a}\n"
+				end
+			end
+
+			# warning: alias but no main ip address
+			if main_ip_v6.is_a?(NotSetup) && ! aliasses_v6.empty?
+				str << "\t#{CRED}alias6 configured but no main ipv6 configuration.#{CRESET}\n"
+				str << "\t#{CRED}Should main ipv6 be obtained from autoconfiguration? DHCP? Static configuration?#{CRESET}\n"
+			end
+
+			unless dns.empty?
+				dns.each do |ip|
+					str << "\tdns: #{ip}\n"
+				end
+			end
+
+			unless wireless_networks.empty?
+				# to improve readability
+				str << "\n"
+				wireless_networks.each do |k,v|
+					str << v
+				end
+			end
+		end
+	end
+
+	# configure the interface
+	def execute
+		unless NetworkCommands.interface_exists(@name)
+			raise "The interface #{@name} doesn't exists, yet."
+		end
+
+		# TODO: treat differently wireless and non-wireless interfaces
+		if @wireless
+			puts "interface #{name} is wireless"
+			puts "TODO:"
+			puts "1. scan for SSID"
+			puts "2. select configured SSID then try to connect"
+			puts "3. connectivity check with the gateway"
+		else
+			puts "interface #{name} is not wireless"
+		end
+
+		if up
+			NetworkCommands.up name
+		else
+			puts "not marked as 'up' -- ending here"
+			return
+		end
+
+		unless mtu.nil?
+			NetworkCommands.mtu name, mtu
+		end
+
+		unless description.nil?
+			NetworkCommands.description name, description.not_nil!
+		end
+
+		# ipv4 configuration
+		main_ip_v4.tap do |ip|
+			case ip
+			when IPAddress
+				NetworkCommands.set_ip name, ip
+			when DHCP
+				NetworkCommands.dhcp name
+			when NotSetup
+				# do nothing
+			else
+				raise "ipv4 configuration: neither static nor dynamic"
+			end
+
+			# We wont setup aliasses unless there is an actual IP address
+			if ip != NotSetup
+				aliasses_v4.each do |ip_alias|
+					NetworkCommands.set_alias name, ip_alias
+				end
+			end
+		end
+
+		# ipv6 configuration
+		main_ip_v6.tap do |ip|
+			case ip
+			when IPAddress
+				NetworkCommands.set_ip name, ip
+			when Autoconfiguration
+				NetworkCommands.autoconfiguration name
+			when DHCP
+				NetworkCommands.dhcp6 name
+			when NotSetup
+				# do nothing
+			else
+				raise "ipv6 configuration: neither static nor dynamic"
+			end
+
+			# We wont setup aliasses unless there is an actual IP address
+			if ip != NotSetup
+				aliasses_v6.each do |ip_alias|
+					NetworkCommands.set_alias name, ip_alias
+				end
+			end
+		end
+	end
+
+	def down
+		unless NetworkCommands.interface_exists(@name)
+			raise "The interface #{@name} doesn't exists or is already down."
+		end
+
+		NetworkCommands.flush name
+		NetworkCommands.down name
+	end
+
+	def scan
+		unless NetworkCommands.interface_exists(@name)
+			raise "The interface #{@name} doesn't exists or is already down."
+		end
+
+		ssid_list = NetworkCommands.scan name
+		pp! ssid_list
+	end
+end
diff --git a/src/context.cr b/src/context.cr
new file mode 100644
index 0000000..3dfb2de
--- /dev/null
+++ b/src/context.cr
@@ -0,0 +1,17 @@
+
+class Context
+	class_property root : String = "/"
+	
+	class_property simulation = false
+	class_property verbosity = 1
+
+	class_property prefered_network_configuration_program : String? = nil
+	class_property prefered_wireless_configuration_program : String? = nil
+	class_property prefered_dhcp_client : String? = nil
+
+	class_property root = "/"
+	class_property print_autodetect = false
+
+	class_property command = "list"
+	class_property args = Array(String).new
+end
diff --git a/src/do.cr b/src/do.cr
new file mode 100644
index 0000000..6a2ed9c
--- /dev/null
+++ b/src/do.cr
@@ -0,0 +1,22 @@
+
+class Do < Process
+	class_property simulation = false
+
+	def self.run(cmd : String, params : Array(String) = nil)
+		if @@simulation
+			puts "simulation, do: #{cmd} #{params.join(" ")}"
+			Process::Status.new 0
+		else
+			Process.run cmd, params
+		end
+	end
+
+	def self.run(cmd : String, params : Array(String) = nil, &block : Process -> _)
+		if @@simulation
+			puts "simulation, do: #{cmd} #{params.join(" ")}"
+			Process::Status.new 0
+		else
+			Process.run cmd, params, &block
+		end
+	end
+end
diff --git a/src/main.cr b/src/main.cr
index 66741cd..5ba3392 100644
--- a/src/main.cr
+++ b/src/main.cr
@@ -2,997 +2,10 @@
 require "option_parser"
 require "ipaddress"
 require "./colors"
-
-class Context
-	class_property root : String = "/"
-	
-	class_property simulation = false
-	class_property verbosity = 1
-
-	class_property prefered_network_configuration_program : String? = nil
-	class_property prefered_wireless_configuration_program : String? = nil
-	class_property prefered_dhcp_client : String? = nil
-
-	class_property root = "/"
-	class_property print_autodetect = false
-
-	class_property command = "list"
-	class_property args = Array(String).new
-end
-
-file_option : String? = nil
-
-OptionParser.parse! do |parser|
-	parser.on "-s", "--simulation", "Export the network configuration." do
-		Context.simulation = true
-	end
-
-	parser.on "-a", "--print-autodetect", "Print autodetection of the installed programs." do
-		Context.print_autodetect = true
-	end
-
-	parser.on "-w wireless-configuration-program", "--wireless wireless-configuration-program", "iw" do |prog|
-		Context.prefered_wireless_configuration_program = prog
-	end
-
-	parser.on "-n network-configuration-program", "--net-conf network-configuration-program", "ifconfig | ip" do |prog|
-		Context.prefered_network_configuration_program = prog
-	end
-
-	parser.on "-d dhcp-client-program", "--dhcp-client dhcp-client-program", "udhcpc | dhclient" do |prog|
-		Context.prefered_dhcp_client = prog
-	end
-
-	parser.on "-r root", "--root root", "Root where to search for <root>/etc/hostname.* files." do |optsn|
-		Context.root = optsn
-	end
-
-	parser.on "-f file", "--file file", "Parse a configuration file." do |optsn|
-		file_option = optsn
-	end
-
-	# 0: nothing is printed, 1: only events, 2: events and messages
-	parser.on "-v verbosity", "--verbosity verbosity", "Verbosity (0-2). Default: 1" do |optsn|
-		Context.verbosity = optsn.to_i
-	end
-
-	parser.missing_option do |opt|
-		STDERR.puts "You missed the argument for option #{opt}"
-		# TODO: explain the different arguments
-		exit 1
-	end
-
-	parser.invalid_option do |flag|
-		STDERR.puts "Error: #{flag} not a valid option"
-		exit 1
-	end
-
-	parser.unknown_args do |arg|
-		Context.command = arg.shift
-		Context.args = arg
-
-		case Context.command
-		when /^(list)/
-		when /^(up)/
-		when /^(down)/
-		when /^(scan)/
-		else
-			STDERR.puts "Command #{Context.command} not understood"
-			exit 1
-		end
-
-		# unless arg.empty?
-		# 	STDERR.puts "unknown arg: #{arg}"
-		# 	exit 1
-		# end
-	end
-
-	parser.on "-h", "--help", "Show this help" do
-		puts parser
-		exit 0
-	end
-end
-
-class Do < Process
-	class_property simulation = false
-
-	def self.run(cmd : String, params : Array(String) = nil)
-		if @@simulation
-			puts "simulation, do: #{cmd} #{params.join(" ")}"
-			Process::Status.new 0
-		else
-			Process.run cmd, params
-		end
-	end
-
-	def self.run(cmd : String, params : Array(String) = nil, &block : Process -> _)
-		if @@simulation
-			puts "simulation, do: #{cmd} #{params.join(" ")}"
-			Process::Status.new 0
-		else
-			Process.run cmd, params, &block
-		end
-	end
-end
-
-class NotSetup
-	def to_s(io : IO)
-		io << "not setup"
-	end
-end
-
-class Autoconfiguration
-	def to_s(io : IO)
-		io << "autoconfiguration"
-	end
-end
-
-class DHCP
-	def to_s(io : IO)
-		io << "dhcp"
-	end
-end
-
-
-class NetworkCommands
-	class_property cmd_network_configuration : IfconfigCommand.class | IPCommand.class = IfconfigCommand
-	class_property cmd_wireless_configuration : IfconfigCommand.class | IWCommand.class | NotSetup.class = NotSetup
-	class_property cmd_dhcp_client : UDHCPCCommand.class | DHClientCommand.class | NotSetup.class = NotSetup
-
-	class DNS
-		def initialize(@addresses : Array(String), @search : Array(String))
-		end
-
-		def execute
-			File.open("#{Context.root}/etc/resolv.conf", "w") do |file|
-				@addresses.each do |address|
-					file.puts "nameserver #{address}\n"
-				end
-
-				file.puts "search #{@search.join(" ")}"
-			end
-		end
-	end
-
-	class IWCommand
-		# get the available SSID
-		def self.scan(ifname : String) : Array(String)
-			ssids = Array(String).new
-
-			Do.run("iw", [ ifname, "scan" ]) do |p|
-				p.output.each_line do |line|
-					ssid = /SSID: (?<ssid>[a-zA-Z0-9_-]+)/.match(line).try &.["ssid"]
-
-					unless ssid.nil?
-						ssids << ssid
-					end
-				end
-			end
-
-			if ssids.empty?
-				raise "(iw) cannot get ssid list from #{ifname}"
-			end
-
-			ssids
-		end
-	end
-
-	class UDHCPCCommand
-		def self.run(ifname : String)
-			unless Do.run("udhcpc", [ ifname ]).success?
-				raise "(udhcpc) dhcp failed on #{ifname}"
-			end
-		end
-
-		def self.dhcp6(ifname : String)
-			# we suppose udhcpc6 installed along with udhcpc
-			unless Do.run("udhcpc6", [ ifname ]).success?
-				raise "(udhcpc6) dhcp failed on #{ifname}"
-			end
-		end
-	end
-
-	class DHClientCommand
-		def self.run(ifname : String)
-			unless Do.run("dhclient", [ ifname ]).success?
-				raise "(dhclient) dhcp failed on #{ifname}"
-			end
-		end
-
-		def self.dhcp6(ifname : String)
-			unless Do.run("dhclient", [ "-6", ifname ]).success?
-				raise "(dhclient) dhcp6 failed on #{ifname}"
-			end
-		end
-	end
-
-	class IfconfigCommand
-		def self.interface_exists(name : String)
-			Do.run("ifconfig", [ name ]).success?
-		end
-
-		def self.up_or_down(name : String, updown : String)
-			unless Do.run("ifconfig", [ name, updown ]).success?
-				raise "(ifconfig) Cannot set #{updown} link name #{name}"
-			end
-		end
-		def self.up(name : String)
-			self.up_or_down name, "up"
-		end
-		def self.down(name : String)
-			self.up_or_down name, "down"
-		end
-
-		def self.set_ip(name : String, ip : IPAddress)
-			unless Do.run("ifconfig", [ name, ip.to_string ]).success?
-				raise "(ifconfig) Cannot set ip address #{ip.to_string} for #{name}"
-			end
-		end
-
-		# currently, aliasses with ifconfig: ifconfig add ip/mask
-		# same command as the ip setup
-		def self.set_alias(name : String, ip : IPAddress)
-			unless Do.run("ifconfig", [ name, "add", ip.to_s ]).success?
-				raise "(ifconfig) Cannot set ip address alias #{ip.to_s} for #{name}"
-			end
-		end
-
-		def self.mtu(name : String, mtu : Int32?)
-			unless Do.run("ifconfig", [ name, "mtu", mtu.to_s ]).success?
-				raise "(ifconfig) Cannot set mtu #{mtu} for #{name}"
-			end
-		end
-
-		def self.description(name : String, description : String)
-			unless Do.run("ifconfig", [ name, "description", "\"#{description}\"" ]).success?
-				raise "(ifconfig) Cannot set description #{description} for #{name}"
-			end
-		end
-
-		def self.flush(name : String)
-			unless Do.run("ifconfig", [ name, "0.0.0.0" ]).success?
-				raise "(ifconfig) Cannot flush #{name} ip addresses"
-			end
-		end
-
-		def self.down(name : String)
-			unless Do.run("ifconfig", [ name, "down" ]).success?
-				raise "(ifconfig) Cannot set down #{name}"
-			end
-		end
-
-		# ifconfig also performs wireless configuration on some OSs
-		def self.scan(name : String)
-			puts "TODO: (ifconfig) ifconfig ifname scan | grep SSID"
-		end
-	end
-
-	class IPCommand
-		def self.interface_exists(name : String)
-			Do.run("ip", [ "link", "show", "dev", name ]).success?
-		end
-
-		def self.up_or_down(name : String, updown : String)
-			unless Do.run("ip", [ "link", "set", updown, "dev", name ]).success?
-				raise "(ip) Cannot set #{updown} link name #{name}"
-			end
-		end
-		def self.up(name : String)
-			self.up_or_down name, "up"
-		end
-		def self.down(name : String)
-			self.up_or_down name, "down"
-		end
-
-		def self.set_ip(name : String, ip : IPAddress)
-			unless Do.run("ip", [ "address", "add", ip.to_string, "dev", name ]).success?
-				raise "(ip) Cannot add ip address #{ip.to_string} to #{name}"
-			end
-		end
-
-		def self.set_alias(name : String, ip : IPAddress)
-			unless Do.run("ip", [ "address", "add", ip.to_string, "dev", name ]).success?
-				raise "(ip) Cannot add ip address alias #{ip.to_string} to #{name}"
-			end
-		end
-
-		def self.mtu(name : String, mtu : Int32?)
-			unless Do.run("ip", [ "link", "set", "mtu", mtu.to_s, "dev", name ]).success?
-				raise "(ip) Cannot set mtu #{mtu} to #{name}"
-			end
-		end
-
-		def self.flush(name : String)
-			unless Do.run("ip", [ "address", "flush", "dev", name ]).success?
-				raise "(ip) Cannot flush #{name} ip addresses"
-			end
-		end
-
-		def self.down(name : String)
-			unless Do.run("ip", [ "link", "set", "down", "dev", name ]).success?
-				raise "(ip) Cannot set down #{name}"
-			end
-		end
-
-		def self.description(name : String, description : String)
-			puts "TODO: (ip) setup description '#{description}' to interface #{name}"
-			# unless Do.run("ip", [ "link", "set", "description", description, "dev", name ]).success?
-			# 	raise "(ip) Cannot set description #{description} to #{name}"
-			# end
-		end
-	end
-
-	def self.interface_exists(name : String)
-		@@cmd_network_configuration.interface_exists(name)
-	end
-
-	def self.up(ifname : String)
-		@@cmd_network_configuration.up(ifname)
-	end
-
-	def self.down(ifname : String)
-		@@cmd_network_configuration.up(ifname)
-	end
-
-	def self.set_ip(name : String, ip : IPAddress)
-		@@cmd_network_configuration.set_ip name, ip
-	end
-
-	def self.dhcp(name : String)
-		cmd = @@cmd_dhcp_client
-		case cmd
-		when NotSetup.class
-			puts "no dhcp client: cannot perform dhcp on #{name}"
-		else
-			cmd.run name
-		end
-	end
-
-	def self.set_alias(name : String, ip : IPAddress)
-		@@cmd_network_configuration.set_alias name, ip
-	end
-
-	def self.mtu(name : String, mtu : Int32?)
-		@@cmd_network_configuration.mtu name, mtu
-	end
-
-	def self.description(name : String, description : String)
-		@@cmd_network_configuration.description name, description
-	end
-
-	def self.flush(name : String)
-		@@cmd_network_configuration.flush name
-	end
-
-	def self.down(name : String)
-		@@cmd_network_configuration.down name
-	end
-
-	def self.scan(ifname : String)
-		cmd = @@cmd_wireless_configuration
-		case cmd
-		when NotSetup.class
-			puts "no wireless configuration program: cannot list ssid"
-		else
-			cmd.scan ifname
-		end
-	end
-
-	def self.autoconfiguration(ifname : String)
-		puts "TODO: IPv6 autoconfiguration setup"
-		puts "sysctl -w net.ipv6.conf.#{ifname}.autoconf=1"
-		puts "sysctl -w net.ipv6.conf.#{ifname}.accept_ra=1"
-	end
-
-	def self.dhcp6(ifname : String)
-		puts "TODO: dhcpv6"
-		@@cmd_dhcp_client.dhcp6 ifname
-	end
-
-	def self.wireless_connect_wpa_psk(ifname : String, ssid : String, passwd : String)
-		cmd = @@cmd_wireless_configuration
-		case cmd
-		when NotSetup.class
-			puts "no wireless configuration program: cannot connect to ssid #{ssid}"
-		else
-			cmd.list_ssid ifname
-		end
-	end
-end
-
-
-class WirelessAPSetup
-	property ssid : String
-
-	# This is a list of parameters that should be unique to each AP
-	property up : Bool
-	property description : String?
-	property mtu : Int32?
-	property main_ip_v4 : IPAddress | DHCP | NotSetup
-	property main_ip_v6 : IPAddress | DHCP | Autoconfiguration | NotSetup
-	property aliasses_v4 : Array(IPAddress)
-	property aliasses_v6 : Array(IPAddress)
-	property dns : Array(IPAddress)
-
-	# we currently only support WPA2-PSK wireless security mechanism
-	property security : WPA
-
-	class WPA
-		property key : String
-		def initialize(@key)
-		end
-	end
-
-	def initialize(@ssid, @security)
-		@main_ip_v4 = NotSetup.new
-		@main_ip_v6 = NotSetup.new
-		@aliasses_v4 = Array(IPAddress).new
-		@aliasses_v6 = Array(IPAddress).new
-		@up = true
-		@dns = Array(IPAddress).new
-	end
-
-
-	def to_s(io : IO)
-		io << to_string
-	end
-
-	def to_string
-		String.build do |str|
-			str << "\t#{CBLUE}#{ssid}#{CRESET}\n"
-
-			str << "\t\t#description #{description.not_nil!}\n" unless description.nil?
-			str << "\t\t#{@up? "up" : "down"}\n"
-			str << "\t\tmtu #{mtu}\n" unless mtu.nil?
-
-			# ipv4
-			unless main_ip_v4.is_a?(NotSetup)
-				str << "\t\tinet #{main_ip_v4}\n"
-
-				aliasses_v4.each do |a|
-					str << "\t\talias #{a}\n"
-				end
-			end
-
-			# ipv6
-			unless main_ip_v6.is_a?(NotSetup)
-				str << "\t\tinet6 #{main_ip_v6}\n"
-
-				@aliasses_v6.each do |a|
-					str << "\t\talias6 #{a}\n"
-				end
-			end
-
-			dns.each do |ip|
-				str << "\t\tdns: #{ip}\n"
-			end
-
-			# to improve readability
-			str << "\n"
-		end
-	end
-end
-
-
-#
-# interface configuration
-#
-
-class InterfaceConfiguration
-
-	property name : String
-	property up : Bool
-	property description : String?
-	property mtu : Int32?
-	property wireless : Bool
-	property main_ip_v4 : IPAddress | DHCP | NotSetup
-	property main_ip_v6 : IPAddress | Autoconfiguration | DHCP | NotSetup
-	property aliasses_v4 : Array(IPAddress)
-	property aliasses_v6 : Array(IPAddress)
-	property wireless_networks : Hash(String, WirelessAPSetup)
-	property dns : Array(IPAddress)
-
-	def initialize (@name, @up,
-					@description,
-					@mtu,
-					@main_ip_v4, @main_ip_v6, aliasses,
-					@wireless, @wireless_networks,
-					@dns = Array(IPAddress).new
-				   )
-
-		@aliasses_v4 = Array(IPAddress).new
-		@aliasses_v6 = Array(IPAddress).new
-
-		aliasses.each do |ip|
-			if ip.ipv4?
-				aliasses_v4 << ip
-			else
-				aliasses_v6 << ip
-			end
-		end
-	end
-
-	def to_s(io : IO)
-		io << to_string
-	end
-
-	def to_string
-		String.build do |str|
-			if NetworkCommands.interface_exists(@name)
-				str << "#{CGREEN}#{@name}#{CRESET}\n"
-			else
-				str << "#{CRED}#{@name}#{CRESET}\n"
-			end
-
-			str << "\tdescription: '#{description.not_nil!}'\n" unless description.nil?
-
-			str << "\t#{@up? "up" : "down"}\n"
-
-			unless mtu.nil?
-				str << "\tmtu #{mtu}\n"
-			end
-
-			# ipv4
-			unless main_ip_v4.is_a?(NotSetup)
-				str << "\tinet #{main_ip_v4}\n"
-
-				aliasses_v4.each do |a|
-					str << "\talias #{a}\n"
-				end
-			end
-
-			# warning: alias but no main ip address
-			if main_ip_v4.is_a?(NotSetup) && ! aliasses_v4.empty?
-				str << "\t#{CRED}alias configured but no main ipv4 configuration.#{CRESET}\n"
-				str << "\t#{CRED}Should main ipv4 be obtained from DHCP? Static configuration?#{CRESET}\n"
-			end
-
-			# ipv6
-			unless main_ip_v6.is_a?(NotSetup)
-				str << "\tinet6 #{main_ip_v6}\n"
-
-				aliasses_v6.each do |a|
-					str << "\talias6 #{a}\n"
-				end
-			end
-
-			# warning: alias but no main ip address
-			if main_ip_v6.is_a?(NotSetup) && ! aliasses_v6.empty?
-				str << "\t#{CRED}alias6 configured but no main ipv6 configuration.#{CRESET}\n"
-				str << "\t#{CRED}Should main ipv6 be obtained from autoconfiguration? DHCP? Static configuration?#{CRESET}\n"
-			end
-
-			unless dns.empty?
-				dns.each do |ip|
-					str << "\tdns: #{ip}\n"
-				end
-			end
-
-			unless wireless_networks.empty?
-				# to improve readability
-				str << "\n"
-				wireless_networks.each do |k,v|
-					str << v
-				end
-			end
-		end
-	end
-
-	# configure the interface
-	def execute
-		unless NetworkCommands.interface_exists(@name)
-			raise "The interface #{@name} doesn't exists, yet."
-		end
-
-		# TODO: treat differently wireless and non-wireless interfaces
-		if @wireless
-			puts "interface #{name} is wireless"
-			puts "TODO:"
-			puts "1. scan for SSID"
-			puts "2. select configured SSID then try to connect"
-			puts "3. connectivity check with the gateway"
-		else
-			puts "interface #{name} is not wireless"
-		end
-
-		if up
-			NetworkCommands.up name
-		else
-			puts "not marked as 'up' -- ending here"
-			return
-		end
-
-		unless mtu.nil?
-			NetworkCommands.mtu name, mtu
-		end
-
-		unless description.nil?
-			NetworkCommands.description name, description.not_nil!
-		end
-
-		# ipv4 configuration
-		main_ip_v4.tap do |ip|
-			case ip
-			when IPAddress
-				NetworkCommands.set_ip name, ip
-			when DHCP
-				NetworkCommands.dhcp name
-			when NotSetup
-				# do nothing
-			else
-				raise "ipv4 configuration: neither static nor dynamic"
-			end
-
-			# We wont setup aliasses unless there is an actual IP address
-			if ip != NotSetup
-				aliasses_v4.each do |ip_alias|
-					NetworkCommands.set_alias name, ip_alias
-				end
-			end
-		end
-
-		# ipv6 configuration
-		main_ip_v6.tap do |ip|
-			case ip
-			when IPAddress
-				NetworkCommands.set_ip name, ip
-			when Autoconfiguration
-				NetworkCommands.autoconfiguration name
-			when DHCP
-				NetworkCommands.dhcp6 name
-			when NotSetup
-				# do nothing
-			else
-				raise "ipv6 configuration: neither static nor dynamic"
-			end
-
-			# We wont setup aliasses unless there is an actual IP address
-			if ip != NotSetup
-				aliasses_v6.each do |ip_alias|
-					NetworkCommands.set_alias name, ip_alias
-				end
-			end
-		end
-	end
-
-	def down
-		unless NetworkCommands.interface_exists(@name)
-			raise "The interface #{@name} doesn't exists or is already down."
-		end
-
-		NetworkCommands.flush name
-		NetworkCommands.down name
-	end
-
-	def scan
-		unless NetworkCommands.interface_exists(@name)
-			raise "The interface #{@name} doesn't exists or is already down."
-		end
-
-		ssid_list = NetworkCommands.scan name
-		pp! ssid_list
-	end
-end
-
-class NetworkConfigurationParser
-	def self.parse_file(file_name : String) : InterfaceConfiguration
-		content = File.read(file_name)
-		content = content.rchop
-		ifname = /.([a-zA-Z0-9]+)$/.match(file_name).try &.[1]
-		if ifname.nil?
-			raise "The interface name is not known from the filename: '#{file_name}'"
-		end
-
-		wireless = false
-		wireless = true unless /^wl[0-9]+$/.match(ifname)
-		self.parse(ifname.not_nil!, content, wireless)
-	end
-
-	def self.parse (ifname : String, data : String, wireless = false) : InterfaceConfiguration
-		up = false
-		description = nil
-		mtu = nil
-		main_ip_v4 = NotSetup.new
-		main_ip_v6 = NotSetup.new
-
-		dns = Array(IPAddress).new
-
-		aliasses = [] of IPAddress
-
-		wireless_networks = {} of String => WirelessAPSetup
-
-		data.split("\n").each do |line|
-			case line
-			when /^up/
-				up = true
-			when /^description/
-				description = /^description (.+)/.match(line).try &.[1]
-			when /^inet6? alias .*/
-				ipstr = /^inet6? alias ([a-f0-9:.\/]+)/.match(line).try &.[1]
-				if ipstr.nil?
-					puts "wrong IP address alias, line #{line}"
-					next
-				end
-				aliasses.push IPAddress.parse(ipstr)
-			when /^inet6? dhcp/
-				# IP address is DHCP
-				if /^inet /.match(line)
-					main_ip_v4 = DHCP.new
-				else
-					main_ip_v6 = DHCP.new
-				end
-			when /^inet6 autoconf/
-				# IP address is autoconfigured
-				main_ip_v6 = Autoconfiguration.new
-
-			when /^inet6? .*/
-				ipstr = /^inet6? ([a-f0-9:.\/]+)/.match(line).try &.[1]
-				if ipstr.nil?
-					puts "wrong IP address, line #{line}"
-					next
-				end
-				if /^inet /.match(line)
-					main_ip_v4 = IPAddress.parse ipstr
-				else
-					main_ip_v6 = IPAddress.parse ipstr
-				end
-			when /^join [^ \t]+ wpakey .*/
-				# WPA2-PSK, other security mechanisms are not supported, yet
-				ssid = /^join ([^ \t]+)/.match(line).try &.[1]
-				wpakeystr = /^join [^ \t]+ wpakey ([^ \t]+)/.match(line).try &.[1]
-
-				if ssid.nil?
-					puts "wrong SSID in line: #{line}"
-					next
-				end
-
-				if wpakeystr.nil?
-					puts "wrong wpa key in line: #{line}"
-					next
-				end
-
-				# TODO
-				new_ap = WirelessAPSetup.new ssid, WirelessAPSetup::WPA.new(wpakeystr)
-				wireless_networks[ssid] = new_ap
-
-
-			when /^network [^ \t]+ inet6 autoconf/
-				puts "TODO: network SSID inet6 autoconf"
-
-				ssid = /^network ([^ \t]+)/.match(line).try &.[1]
-				ipstr = /^network [^ \t]+ inet6? ([^ \t]+)/.match(line).try &.[1]
-
-				if ssid.nil?
-					puts "wrong SSID in line: #{line}"
-					next
-				end
-
-				if ipstr.nil?
-					puts "wrong ip address in line: #{line}"
-					next
-				end
-
-				access_point = wireless_networks[ssid].not_nil!
-				access_point.main_ip_v6 = Autoconfiguration.new
-				puts "for SSID: #{ssid} ipv6 configuration = autoconf"
-
-			when /^network [^ \t]+ inet6? .*/
-				ssid = nil
-				ipstr = nil
-
-				/^network (?<ssid>[^ \t]+) inet6? (?<ip>[^ \t]+)/.match(line).try do |m|
-					ssid = m["ssid"]
-					ipstr = m["ip"]
-				end
-
-				if ssid.nil?
-					puts "wrong SSID in line: #{line}"
-					next
-				end
-
-				if ipstr.nil?
-					puts "wrong ip address in line: #{line}"
-					next
-				end
-
-				ipaddr = IPAddress.parse ipstr
-				access_point = wireless_networks[ssid].not_nil!
-
-				if ipaddr.ipv4?
-					access_point.main_ip_v4 = ipaddr
-				elsif ipaddr.ipv6?
-					access_point.main_ip_v6 = ipaddr
-				else
-					puts "wrong ip address in line: #{line} (neither ipv4 or ipv6)"
-				end
-
-			when /^network [^ ]+ dhcp6?/
-				ssid = /^network (?<ssid>[^ \t]+)/.match(line).try &.["ssid"]
-
-				if ssid.nil?
-					puts "wrong SSID in line: #{line}"
-					next
-				end
-
-				access_point = wireless_networks[ssid].not_nil!
-
-				if /dhcp6/.match(line)
-					access_point.main_ip_v6 = DHCP.new
-				elsif /dhcp/.match(line)
-					access_point.main_ip_v4 = DHCP.new
-				else
-					puts "wrong dhcp instruction in line: #{line}"
-				end
-
-			when /^network [^ ]+ dns .*/
-				ssid = nil
-				ipstr = nil
-
-				/^network (?<ssid>[^ \t]+) dns (?<ip>[^ \t]+)/.match(line).try do |m|
-					ssid = m["ssid"]
-					ipstr = m["ip"]
-				end
-
-				if ssid.nil?
-					puts "wrong SSID in line: #{line}"
-					next
-				end
-
-				if ipstr.nil?
-					puts "wrong ip address in line: #{line}"
-					next
-				end
-
-				access_point = wireless_networks[ssid].not_nil!
-				ipaddr = IPAddress.parse ipstr
-				access_point.dns << ipaddr
-
-			when /^mtu [0-9]+/
-				mtu = /^mtu ([0-9]+)/.match(line).try &.[1].to_i
-
-			when /^dns [^ \t]+/
-				ipstr = nil
-
-				/^dns (?<ip>[^ \t]+)/.match(line).try do |m|
-					ipstr = m["ip"]
-				end
-
-				if ipstr.nil?
-					puts "wrong ip address in line: #{line}"
-					next
-				end
-
-				ipaddr = IPAddress.parse ipstr
-				dns << ipaddr
-
-			when /^#.*$/
-				# simple comment
-			when /^[ \t]*$/
-				# empty line
-			else
-				raise "Cannot parse: #{line}"
-			end
-		end
-
-		InterfaceConfiguration.new(ifname, up,
-								   description,
-								   mtu,
-								   main_ip_v4, main_ip_v6,
-								   aliasses,
-								   wireless, wireless_networks,
-								   dns)
-	end
-end
-
-
-
-class Autodetect
-	class_property print_autodetect : Bool = false
-
-	def self.which(cmd : String)
-		if Process.run("which", [ cmd ]).success?
-			puts "#{cmd} installed" if print_autodetect
-			true
-		else
-			puts "#{cmd} not installed" if print_autodetect
-			false
-		end
-	end
-end
-
-
-Do.simulation = Context.simulation
-Autodetect.print_autodetect = Context.print_autodetect
-
-#
-# discover available configuration commands
-#
-
-# ifconfig = *bsd and some linux
-# ip = linux
-possible_network_configuration_cmds = {
-	"ifconfig" => NetworkCommands::IfconfigCommand,
-	"ip"       => NetworkCommands::IPCommand
-}
-
-# udhcpc = busybox dhcp client
-possible_dhcp_clients = {
-	"udhcpc" => NetworkCommands::UDHCPCCommand,
-	"dhclient" => NetworkCommands::DHClientCommand
-}
-
-# iw = linux
-possible_wireless_configuration_cmds = {
-	"iw" => NetworkCommands::IWCommand,
-	"ifconfig" => NetworkCommands::IfconfigCommand
-}
-
-key = Context.prefered_network_configuration_program
-key = possible_network_configuration_cmds.keys.find { |key| Autodetect.which(key) } if key.nil?
-# should crash if there is no network command installed
-NetworkCommands.cmd_network_configuration = possible_network_configuration_cmds[key.not_nil!]
-
-key = Context.prefered_dhcp_client
-key = possible_dhcp_clients.keys.find { |key| Autodetect.which(key) } if key.nil?
-# should not crash if there is no 
-NetworkCommands.cmd_dhcp_client = possible_dhcp_clients[key] unless key.nil?
-
-key = Context.prefered_wireless_configuration_program
-key = possible_wireless_configuration_cmds.keys.find { |key| Autodetect.which(key) } if key.nil?
-# should crash if there is no wireless command installed
-NetworkCommands.cmd_wireless_configuration = possible_wireless_configuration_cmds[key.not_nil!]
-
-
-
-files = Array(String).new
-Dir.children("#{Context.root}/etc/").each do |f|
-	if /^hostname\./.match(f)
-		files << f
-	end
-end
-
-interface_files = Array(String).new
-
-if ! file_option.nil?
-	# file passed via the '-f' option
-	# TODO: why having to force "not_nil!" ? Seems like a compiler bug
-	interface_files << file_option.not_nil!
-elsif Context.args.empty?
-	# every configured interface
-	files.each do |f|
-		interface_files << "#{Context.root}/etc/#{f}"
-	end
-else
-	# only interfaces in arguments
-	Context.args.each do |interface|
-		interface_files << "#{Context.root}/etc/hostname.#{interface}"
-	end
-end
-
-
-
-begin
-	case Context.command
-	when "list"
-		interface_files.each do |f|
-			puts NetworkConfigurationParser.parse_file(f)
-		end
-	when "up"
-		interface_files.each do |f|
-			network_configuration = NetworkConfigurationParser.parse_file(f)
-			network_configuration.execute
-		end
-	when "down"
-		interface_files.each do |f|
-			network_configuration = NetworkConfigurationParser.parse_file(f)
-			network_configuration.down
-		end
-	when "scan"
-		interface_files.each do |f|
-			network_configuration = NetworkConfigurationParser.parse_file(f)
-			network_configuration.scan
-		end
-	end
-rescue e
-	STDERR.puts "#{CRED}Exception: #{CRESET}#{e}"
-end
+require "./context"
+require "./network_commands"
+require "./network_configuration_parser"
+require "./do"
+require "./configuration"
+require "./autodetect_environment"
+require "./cli"
diff --git a/src/network_commands.cr b/src/network_commands.cr
new file mode 100644
index 0000000..1365282
--- /dev/null
+++ b/src/network_commands.cr
@@ -0,0 +1,280 @@
+
+# TODO: OpenBSD: no '-w' parameter for sysctl
+# TODO: OpenBSD: ifconfig scan
+# TODO: Linux: description with ip-* command family
+
+class NetworkCommands
+	class_property cmd_network_configuration : IfconfigCommand.class | IPCommand.class = IfconfigCommand
+	class_property cmd_wireless_configuration : IfconfigCommand.class | IWCommand.class | NotSetup.class = NotSetup
+	class_property cmd_dhcp_client : UDHCPCCommand.class | DHClientCommand.class | NotSetup.class = NotSetup
+
+	class DNS
+		def initialize(@addresses : Array(String), @search : Array(String))
+		end
+
+		def execute
+			File.open("#{Context.root}/etc/resolv.conf", "w") do |file|
+				@addresses.each do |address|
+					file.puts "nameserver #{address}\n"
+				end
+
+				file.puts "search #{@search.join(" ")}"
+			end
+		end
+	end
+
+	class IWCommand
+		# get the available SSID
+		def self.scan(ifname : String) : Array(String)
+			ssids = Array(String).new
+
+			Do.run("iw", [ ifname, "scan" ]) do |p|
+				p.output.each_line do |line|
+					ssid = /SSID: (?<ssid>[a-zA-Z0-9_-]+)/.match(line).try &.["ssid"]
+
+					unless ssid.nil?
+						ssids << ssid
+					end
+				end
+			end
+
+			if ssids.empty?
+				raise "(iw) cannot get ssid list from #{ifname}"
+			end
+
+			ssids
+		end
+	end
+
+	class UDHCPCCommand
+		def self.run(ifname : String)
+			unless Do.run("udhcpc", [ ifname ]).success?
+				raise "(udhcpc) dhcp failed on #{ifname}"
+			end
+		end
+
+		def self.dhcp6(ifname : String)
+			# we suppose udhcpc6 installed along with udhcpc
+			unless Do.run("udhcpc6", [ ifname ]).success?
+				raise "(udhcpc6) dhcp failed on #{ifname}"
+			end
+		end
+	end
+
+	class DHClientCommand
+		def self.run(ifname : String)
+			unless Do.run("dhclient", [ ifname ]).success?
+				raise "(dhclient) dhcp failed on #{ifname}"
+			end
+		end
+
+		def self.dhcp6(ifname : String)
+			unless Do.run("dhclient", [ "-6", ifname ]).success?
+				raise "(dhclient) dhcp6 failed on #{ifname}"
+			end
+		end
+	end
+
+	class IfconfigCommand
+		def self.interface_exists(name : String)
+			Do.run("ifconfig", [ name ]).success?
+		end
+
+		def self.up_or_down(name : String, updown : String)
+			unless Do.run("ifconfig", [ name, updown ]).success?
+				raise "(ifconfig) Cannot set #{updown} link name #{name}"
+			end
+		end
+		def self.up(name : String)
+			self.up_or_down name, "up"
+		end
+		def self.down(name : String)
+			self.up_or_down name, "down"
+		end
+
+		def self.set_ip(name : String, ip : IPAddress)
+			unless Do.run("ifconfig", [ name, ip.to_string ]).success?
+				raise "(ifconfig) Cannot set ip address #{ip.to_string} for #{name}"
+			end
+		end
+
+		# currently, aliasses with ifconfig: ifconfig add ip/mask
+		# same command as the ip setup
+		def self.set_alias(name : String, ip : IPAddress)
+			unless Do.run("ifconfig", [ name, "add", ip.to_s ]).success?
+				raise "(ifconfig) Cannot set ip address alias #{ip.to_s} for #{name}"
+			end
+		end
+
+		def self.mtu(name : String, mtu : Int32?)
+			unless Do.run("ifconfig", [ name, "mtu", mtu.to_s ]).success?
+				raise "(ifconfig) Cannot set mtu #{mtu} for #{name}"
+			end
+		end
+
+		def self.description(name : String, description : String)
+			unless Do.run("ifconfig", [ name, "description", "\"#{description}\"" ]).success?
+				raise "(ifconfig) Cannot set description #{description} for #{name}"
+			end
+		end
+
+		def self.flush(name : String)
+			unless Do.run("ifconfig", [ name, "0.0.0.0" ]).success?
+				raise "(ifconfig) Cannot flush #{name} ip addresses"
+			end
+		end
+
+		def self.down(name : String)
+			unless Do.run("ifconfig", [ name, "down" ]).success?
+				raise "(ifconfig) Cannot set down #{name}"
+			end
+		end
+
+		# ifconfig also performs wireless configuration on some OSs
+		def self.scan(name : String)
+			puts "TODO: (ifconfig) ifconfig ifname scan | grep SSID"
+		end
+	end
+
+	class IPCommand
+		def self.interface_exists(name : String)
+			Do.run("ip", [ "link", "show", "dev", name ]).success?
+		end
+
+		def self.up_or_down(name : String, updown : String)
+			unless Do.run("ip", [ "link", "set", updown, "dev", name ]).success?
+				raise "(ip) Cannot set #{updown} link name #{name}"
+			end
+		end
+		def self.up(name : String)
+			self.up_or_down name, "up"
+		end
+		def self.down(name : String)
+			self.up_or_down name, "down"
+		end
+
+		def self.set_ip(name : String, ip : IPAddress)
+			unless Do.run("ip", [ "address", "add", ip.to_string, "dev", name ]).success?
+				raise "(ip) Cannot add ip address #{ip.to_string} to #{name}"
+			end
+		end
+
+		def self.set_alias(name : String, ip : IPAddress)
+			unless Do.run("ip", [ "address", "add", ip.to_string, "dev", name ]).success?
+				raise "(ip) Cannot add ip address alias #{ip.to_string} to #{name}"
+			end
+		end
+
+		def self.mtu(name : String, mtu : Int32?)
+			unless Do.run("ip", [ "link", "set", "mtu", mtu.to_s, "dev", name ]).success?
+				raise "(ip) Cannot set mtu #{mtu} to #{name}"
+			end
+		end
+
+		def self.flush(name : String)
+			unless Do.run("ip", [ "address", "flush", "dev", name ]).success?
+				raise "(ip) Cannot flush #{name} ip addresses"
+			end
+		end
+
+		def self.down(name : String)
+			unless Do.run("ip", [ "link", "set", "down", "dev", name ]).success?
+				raise "(ip) Cannot set down #{name}"
+			end
+		end
+
+		def self.description(name : String, description : String)
+			puts "TODO: (ip) setup description '#{description}' to interface #{name}"
+			# unless Do.run("ip", [ "link", "set", "description", description, "dev", name ]).success?
+			# 	raise "(ip) Cannot set description #{description} to #{name}"
+			# end
+		end
+	end
+
+	def self.interface_exists(name : String)
+		@@cmd_network_configuration.interface_exists(name)
+	end
+
+	def self.up(ifname : String)
+		@@cmd_network_configuration.up(ifname)
+	end
+
+	def self.down(ifname : String)
+		@@cmd_network_configuration.up(ifname)
+	end
+
+	def self.set_ip(name : String, ip : IPAddress)
+		@@cmd_network_configuration.set_ip name, ip
+	end
+
+	def self.dhcp(name : String)
+		cmd = @@cmd_dhcp_client
+		case cmd
+		when NotSetup.class
+			raise "no dhcp client: cannot perform dhcp on #{name}"
+		else
+			cmd.run name
+		end
+	end
+
+	def self.set_alias(name : String, ip : IPAddress)
+		@@cmd_network_configuration.set_alias name, ip
+	end
+
+	def self.mtu(name : String, mtu : Int32?)
+		@@cmd_network_configuration.mtu name, mtu
+	end
+
+	def self.description(name : String, description : String)
+		@@cmd_network_configuration.description name, description
+	end
+
+	def self.flush(name : String)
+		@@cmd_network_configuration.flush name
+	end
+
+	def self.down(name : String)
+		@@cmd_network_configuration.down name
+	end
+
+	def self.scan(ifname : String)
+		cmd = @@cmd_wireless_configuration
+		case cmd
+		when NotSetup.class
+			raise "no wireless configuration program: cannot list ssid"
+		else
+			cmd.scan ifname
+		end
+	end
+
+	def self.autoconfiguration(ifname : String)
+		# TODO: no '-w' option on openbsd
+		unless Do.run("sysctl", [ "-w", "net.ipv6.conf.#{ifname}.autoconf=1" ]).success?
+			raise "(sysctl) cannot set 'net.ipv6.conf.#{ifname}.autoconf=1'"
+		end
+
+		unless Do.run("sysctl", [ "-w", "net.ipv6.conf.#{ifname}.accept_ra=1" ]).success?
+			raise "(sysctl) cannot set 'net.ipv6.conf.#{ifname}.accept_ra=1'"
+		end
+	end
+
+	def self.dhcp6(ifname : String)
+		cmd = @@cmd_dhcp_client
+		case cmd
+		when NotSetup.class
+			raise "no dhcpv6 program"
+		else
+			cmd.dhcp6 ifname
+		end
+	end
+
+	def self.wireless_connect_wpa_psk(ifname : String, ssid : String, passwd : String)
+		cmd = @@cmd_wireless_configuration
+		case cmd
+		when NotSetup.class
+			puts "no wireless configuration program: cannot connect to ssid #{ssid}"
+		else
+			cmd.list_ssid ifname
+		end
+	end
+end
diff --git a/src/network_configuration_parser.cr b/src/network_configuration_parser.cr
new file mode 100644
index 0000000..4c3f33b
--- /dev/null
+++ b/src/network_configuration_parser.cr
@@ -0,0 +1,210 @@
+
+class NetworkConfigurationParser
+	def self.parse_file(file_name : String) : InterfaceConfiguration
+		content = File.read(file_name)
+		content = content.rchop
+		ifname = /.([a-zA-Z0-9]+)$/.match(file_name).try &.[1]
+		if ifname.nil?
+			raise "The interface name is not known from the filename: '#{file_name}'"
+		end
+
+		wireless = false
+		wireless = true unless /^wl[0-9]+$/.match(ifname)
+		self.parse(ifname.not_nil!, content, wireless)
+	end
+
+	def self.parse (ifname : String, data : String, wireless = false) : InterfaceConfiguration
+		up = false
+		description = nil
+		mtu = nil
+		main_ip_v4 = NotSetup.new
+		main_ip_v6 = NotSetup.new
+
+		dns = Array(IPAddress).new
+
+		aliasses = [] of IPAddress
+
+		wireless_networks = {} of String => WirelessAPSetup
+
+		data.split("\n").each do |line|
+			case line
+			when /^up/
+				up = true
+			when /^description/
+				description = /^description (.+)/.match(line).try &.[1]
+			when /^inet6? alias .*/
+				ipstr = /^inet6? alias ([a-f0-9:.\/]+)/.match(line).try &.[1]
+				if ipstr.nil?
+					puts "wrong IP address alias, line #{line}"
+					next
+				end
+				aliasses.push IPAddress.parse(ipstr)
+			when /^inet6? dhcp/
+				# IP address is DHCP
+				if /^inet /.match(line)
+					main_ip_v4 = DHCP.new
+				else
+					main_ip_v6 = DHCP.new
+				end
+			when /^inet6 autoconf/
+				# IP address is autoconfigured
+				main_ip_v6 = Autoconfiguration.new
+
+			when /^inet6? .*/
+				ipstr = /^inet6? ([a-f0-9:.\/]+)/.match(line).try &.[1]
+				if ipstr.nil?
+					puts "wrong IP address, line #{line}"
+					next
+				end
+				if /^inet /.match(line)
+					main_ip_v4 = IPAddress.parse ipstr
+				else
+					main_ip_v6 = IPAddress.parse ipstr
+				end
+			when /^join [^ \t]+ wpakey .*/
+				# WPA2-PSK, other security mechanisms are not supported, yet
+				ssid = /^join ([^ \t]+)/.match(line).try &.[1]
+				wpakeystr = /^join [^ \t]+ wpakey ([^ \t]+)/.match(line).try &.[1]
+
+				if ssid.nil?
+					puts "wrong SSID in line: #{line}"
+					next
+				end
+
+				if wpakeystr.nil?
+					puts "wrong wpa key in line: #{line}"
+					next
+				end
+
+				# TODO
+				new_ap = WirelessAPSetup.new ssid, WirelessAPSetup::WPA.new(wpakeystr)
+				wireless_networks[ssid] = new_ap
+
+
+			when /^network [^ \t]+ inet6 autoconf/
+				puts "TODO: network SSID inet6 autoconf"
+
+				ssid = /^network ([^ \t]+)/.match(line).try &.[1]
+				ipstr = /^network [^ \t]+ inet6? ([^ \t]+)/.match(line).try &.[1]
+
+				if ssid.nil?
+					puts "wrong SSID in line: #{line}"
+					next
+				end
+
+				if ipstr.nil?
+					puts "wrong ip address in line: #{line}"
+					next
+				end
+
+				access_point = wireless_networks[ssid].not_nil!
+				access_point.main_ip_v6 = Autoconfiguration.new
+				puts "for SSID: #{ssid} ipv6 configuration = autoconf"
+
+			when /^network [^ \t]+ inet6? .*/
+				ssid = nil
+				ipstr = nil
+
+				/^network (?<ssid>[^ \t]+) inet6? (?<ip>[^ \t]+)/.match(line).try do |m|
+					ssid = m["ssid"]
+					ipstr = m["ip"]
+				end
+
+				if ssid.nil?
+					puts "wrong SSID in line: #{line}"
+					next
+				end
+
+				if ipstr.nil?
+					puts "wrong ip address in line: #{line}"
+					next
+				end
+
+				ipaddr = IPAddress.parse ipstr
+				access_point = wireless_networks[ssid].not_nil!
+
+				if ipaddr.ipv4?
+					access_point.main_ip_v4 = ipaddr
+				elsif ipaddr.ipv6?
+					access_point.main_ip_v6 = ipaddr
+				else
+					puts "wrong ip address in line: #{line} (neither ipv4 or ipv6)"
+				end
+
+			when /^network [^ ]+ dhcp6?/
+				ssid = /^network (?<ssid>[^ \t]+)/.match(line).try &.["ssid"]
+
+				if ssid.nil?
+					puts "wrong SSID in line: #{line}"
+					next
+				end
+
+				access_point = wireless_networks[ssid].not_nil!
+
+				if /dhcp6/.match(line)
+					access_point.main_ip_v6 = DHCP.new
+				elsif /dhcp/.match(line)
+					access_point.main_ip_v4 = DHCP.new
+				else
+					puts "wrong dhcp instruction in line: #{line}"
+				end
+
+			when /^network [^ ]+ dns .*/
+				ssid = nil
+				ipstr = nil
+
+				/^network (?<ssid>[^ \t]+) dns (?<ip>[^ \t]+)/.match(line).try do |m|
+					ssid = m["ssid"]
+					ipstr = m["ip"]
+				end
+
+				if ssid.nil?
+					puts "wrong SSID in line: #{line}"
+					next
+				end
+
+				if ipstr.nil?
+					puts "wrong ip address in line: #{line}"
+					next
+				end
+
+				access_point = wireless_networks[ssid].not_nil!
+				ipaddr = IPAddress.parse ipstr
+				access_point.dns << ipaddr
+
+			when /^mtu [0-9]+/
+				mtu = /^mtu ([0-9]+)/.match(line).try &.[1].to_i
+
+			when /^dns [^ \t]+/
+				ipstr = nil
+
+				/^dns (?<ip>[^ \t]+)/.match(line).try do |m|
+					ipstr = m["ip"]
+				end
+
+				if ipstr.nil?
+					puts "wrong ip address in line: #{line}"
+					next
+				end
+
+				ipaddr = IPAddress.parse ipstr
+				dns << ipaddr
+
+			when /^#.*$/
+				# simple comment
+			when /^[ \t]*$/
+				# empty line
+			else
+				raise "Cannot parse: #{line}"
+			end
+		end
+
+		InterfaceConfiguration.new(ifname, up,
+								   description,
+								   mtu,
+								   main_ip_v4, main_ip_v6,
+								   aliasses,
+								   wireless, wireless_networks,
+								   dns)
+	end
+end