An experimental OpenFlow controller which discovers OpenFlow switch network topology. Written with the trema framework.

gistfile1.rb

require 'rubygems'
require 'bindata'

class BasicLLDPPacket < BinData::Record
    endian	:big

	uint48	:dst_mac
	uint48	:src_mac, :value => 0x0180c200000e
	uint16	:ether_type, :value => 0x88cc

	bit7	:chassis_tlv_type, :value => 1
	bit9	:chassis_tlv_length, :value => lambda { chassis_id.length + 1 }
	uint8	:chassis_id_type, :value => 7
	string	:chassis_id, :read_length => lambda { chassis_tlv_length - 1}

	bit7	:port_tlv_type, :value => 2
	bit9	:port_tlv_length, :value => lambda { port_id.length + 1 }
	uint8	:port_id_type, :value => 7
	string	:port_id, :read_length => lambda { port_tlv_length - 1}

	bit7	:ttl_tlv_type, :value => 3
	bit9	:ttl_tlv_length, :value => 2
	uint16	:ttl, :initial_value => 180

	bit7	:end_tlv_type, :value => 0
	bit9	:end_tlv_length, :value => 0
end

class TopologyFinder < Controller
	periodic_timer_event :flood_lldp_packets, 10

	def start
		@switch_ports = {}
	end

	def switch_ready datapath_id
		send_message datapath_id, FeaturesRequest.new
	end

	def features_reply datapath_id, message
		info "List of ports on switch #{datapath_id.to_hex}:"
		ports = message.ports.select {|each|
			each.up?
		}.collect {|each|
			each.number
		}
		p ports

		@switch_ports[datapath_id] = ports
	end

	def packet_in datapath_id, message
		if message.lldp?
			dst_datapath_id = datapath_id
			dst_port = message.in_port
			src_datapath_id, src_port = parse_lldp_packet message.data

			info "SW#{src_datapath_id.to_hex} -> SW#{dst_datapath_id.to_hex} [label=\"#{src_port} to #{dst_port}\"];"
		end
	end

	def flood_lldp_packets
		info "Start LLDP flooding"

		@switch_ports.each_pair {|datapath_id, ports|
			ports.each {|port|
				packet = get_lldp_packet datapath_id, port, 180

				send_packet_out(
					datapath_id,
					:data => packet,
					:actions => SendOutPort.new(port)
				)
			}
		}
	end

	private
	def parse_lldp_packet data
		packet = BasicLLDPPacket.read data
		datapath_id = packet.chassis_id.hex
		port = packet.port_id.to_i

		return datapath_id, port
	end

	def get_lldp_packet datapath_id, port, ttl
		packet = BasicLLDPPacket.new
		packet.dst_mac = 0x000e0cb84897
		packet.chassis_id = datapath_id.to_hex
		packet.port_id = port.to_s
		packet.ttl = ttl

		data = packet.to_binary_s
		if data.size < 64
			data << "\xa5" * (64 - data.size)
		end

		return data
	end
end