SDN之openflow简明教程
软件准备
使用虚拟机进行仿真很容易，这里不再介绍。
下面在ubuntu 13.10上安装mininet仿真环境。
Mininet 2.1.0 on Ubuntu 13.10: sudo apt-get install mininet
Mininet 2.0.0 on Ubuntu 13.04: sudo apt-get install mininet
Mininet 2.0.0 on Ubuntu 12.10: sudo apt-get install mininet/quantal-backports
Mininet 2.0.0 on Ubuntu 12.04: sudo apt-get install mininet/precise-backports
apt-get install openvswitch-datapath-dkms
/etc/init.d/openvswitch-switch start
至此，mininet已经安装完成。
运行mn --test pingall测试安装是否正常。。
/*-----------------可选-----------------
如需要OpenFlow reference switch, reference controller and Wireshark dissector组件，请运行下面命令，这里我们跳过。
git clone git://github.com/mininet/mininet
mininet/util/install.sh -fw
当然也可以直接用源码包安装，如下：
git clone git://github.com/mininet/mininet
To install everything (using your home directory): install.sh -a
mininet/util/install.sh -h可以查看帮助选项。
------------------可选----------------*/
使用命令mn --topo single,3 --mac --switch ovsk --controller remote创建一个3台主机，一台(openvSwitch-based)交换机的虚拟网络。
mininet简明介绍
查看节点：mininet> nodes
在特定主机上运行命令，在命令前面上加上主机名即可：mininet> h1 ifconfig
退出mininet后，可使用mn -c清除之前构建的虚拟网络。
dpclt简介
显示交换机端口状态：dpctl show tcp:127.0.0.1:6634
显示交换机流表状态：dpctl dump-flows tcp:127.0.0.1:6634
在交换机中增加一条流表：dpctl add-flow tcp:127.0.0.1:6634 in_port=1,actions=output:2
控制器与交换机间的交互过程
| Message | Type | Description |
| Hello | Controller->Switch | following the TCP handshake, the controller sends its version number to the switch. |
| Hello | Switch->Controller | the switch replies with its supported version number. |
| Features Request | Controller->Switch | the controller asks to see which ports are available. |
| Set Config | Controller->Switch | in this case, the controller asks the switch to send flow expirations. |
| Features Reply | Switch->Controller | the switch replies with a list of ports, port speeds, and supported tables and actions. |
| Port Status | Switch->Controller | enables the switch to inform that controller of changes to port speeds or connectivity. Ignore this one, it appears to be a bug. |
报文通过SDN网络的过程
| Message | Type | Description |
| Packet-In | Switch->Controller | a packet was received and it didn't match any entry in the switch's flow table, causing the packet to be sent to the controller. |
| Packet-Out | Controller->Switch | controller send a packet out one or more switch ports. |
| Flow-Mod | Controller->Switch | instructs a switch to add a particular flow to its flow table. |
| Flow-Expired | Switch->Controller | a flow timed out after a period of inactivity. |
性能测试
mininet> iperf
选择控制器开发框架
Python:POX,Ryu
Ruby:Trema
Haskell:Nettle(还不完善)
Java:Floodlight
详细的控制器列表参见http://yuba.stanford.edu/~casado/of-sw.html
下面我们用POX来尝试开发控制器。
git clone http://github.com/noxrepo/pox
cd pox
./pox.py log.level --DEBUG misc.of_tutorial
现在我们使用了位于pox/misc下的of_tutorial.py作为控制器。
使用mininet> pingall测试连通性。
使用mininet> iperf测试性能。
好，现在我们来看一下of_tutorial.py的源码。
# Copyright 2012 James McCauley # # Licensed under the Apache License, Version 2.0 (the "License"); # you may not use this file except in compliance with the License. # You may obtain a copy of the License at: # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. # See the License for the specific language governing permissions and # limitations under the License. """ This component is for use with the OpenFlow tutorial. It acts as a simple hub, but can be modified to act like an L2 learning switch. It's roughly similar to the one Brandon Heller did for NOX. """ from pox.core import core import pox.openflow.libopenflow_01 as of log = core.getLogger() class Tutorial (object): """ A Tutorial object is created for each switch that connects. A Connection object for that switch is passed to the __init__ function. """ def __init__ (self, connection): # Keep track of the connection to the switch so that we can # send it messages! self.connection = connection # This binds our PacketIn event listener connection.addListeners(self) # Use this table to keep track of which ethernet address is on # which switch port (keys are MACs, values are ports). self.mac_to_port = {} def resend_packet (self, packet_in, out_port): """ Instructs the switch to resend a packet that it had sent to us. "packet_in" is the ofp_packet_in object the switch had sent to the controller due to a table-miss. """ msg = of.ofp_packet_out() msg.data = packet_in # Add an action to send to the specified port action = of.ofp_action_output(port = out_port) msg.actions.append(action) # Send message to switch self.connection.send(msg) def act_like_hub (self, packet, packet_in): """ Implement hub-like behavior -- send all packets to all ports besides the input port. """ # We want to output to all ports -- we do that using the special # OFPP_ALL port as the output port. (We could have also used # OFPP_FLOOD.) self.resend_packet(packet_in, of.OFPP_ALL) # Note that if we didn't get a valid buffer_id, a slightly better # implementation would check that we got the full data before # sending it (len(packet_in.data) should be == packet_in.total_len)). def act_like_switch (self, packet, packet_in): """ Implement switch-like behavior. """ """ # DELETE THIS LINE TO START WORKING ON THIS (AND THE ONE BELOW!) # # Here's some psuedocode to start you off implementing a learning # switch. You'll need to rewrite it as real Python code. # Learn the port for the source MAC self.mac_to_port ... <add or update entry> if the port associated with the destination MAC of the packet is known: # Send packet out the associated port self.resend_packet(packet_in, ...) # Once you have the above working, try pushing a flow entry # instead of resending the packet (comment out the above and # uncomment and complete the below.) log.debug("Installing flow...") # Maybe the log statement should have source/destination/port? #msg = of.ofp_flow_mod() # ## Set fields to match received packet #msg.match = of.ofp_match.from_packet(packet) # #< Set other fields of flow_mod (timeouts? buffer_id?) > # #< Add an output action, and send -- similar to resend_packet() > else: # Flood the packet out everything but the input port # This part looks familiar, right? self.resend_packet(packet_in, of.OFPP_ALL) """ # DELETE THIS LINE TO START WORKING ON THIS # def _handle_PacketIn (self, event): """ Handles packet in messages from the switch. """ packet = event.parsed # This is the parsed packet data. if not packet.parsed: log.warning("Ignoring incomplete packet") return packet_in = event.ofp # The actual ofp_packet_in message. # Comment out the following line and uncomment the one after # when starting the exercise. self.act_like_hub(packet, packet_in) #self.act_like_switch(packet, packet_in) def launch (): """ Starts the component """ def start_switch (event): log.debug("Controlling %s" % (event.connection,)) Tutorial(event.connection) core.openflow.addListenerByName("ConnectionUp", start_switch)
POX使用简介
Sending OpenFlow messages with POX
connection.send( ... ) # send an OpenFlow message to a switch
When a connection to a switch starts, a ConnectionUp event is fired. The example code creates a new Tutorial object that holds a reference to the associated Connection object. This can later be used to send commands (OpenFlow messages) to the switch.
ofp_action_output class
This is an action for use with ofp_packet_out and ofp_flow_mod. It specifies a switch port that you wish to send the packet out of. It can also take various "special" port numbers. An example of this would be OFPP_FLOOD which sends the packet out all ports except the one the packet originally arrived on.
Example. Create an output action that would send packets to all ports:
out_action = of.ofp_action_output(port = of.OFPP_FLOOD)
ofp_match class
Objects of this class describe packet header fields and an input port to match on. All fields are optional -- items that are not specified are "wildcards" and will match on anything.
Some notable fields of ofp_match objects are:
- dl_src - The data link layer (MAC) source address
- dl_dst - The data link layer (MAC) destination address
- in_port - The packet input switch port
Example. Create a match that matches packets arriving on port 3:
match = of.ofp_match()
match.in_port = 3
ofp_packet_out OpenFlow message
The ofp_packet_out message instructs a switch to send a packet. The packet might be one constructed at the controller, or it might be one that the switch received, buffered, and forwarded to the controller (and is now referenced by a buffer_id).
Notable fields are:
- buffer_id - The buffer_id of a buffer you wish to send. Do not set if you are sending a constructed packet.
- data - Raw bytes you wish the switch to send. Do not set if you are sending a buffered packet.
- actions - A list of actions to apply (for this tutorial, this is just a single ofp_action_output action).
- in_port - The port number this packet initially arrived on if you are sending by buffer_id, otherwise OFPP_NONE.
ofp_flow_mod OpenFlow message
This instructs a switch to install a flow table entry. Flow table entries match some fields of incoming packets, and executes some list of actions on matching packets. The actions are the same as for ofp_packet_out, mentioned above (and, again, for the tutorial all you need is the simple ofp_action_output action). The match is described by an ofp_match object.
Notable fields are:
- idle_timeout - Number of idle seconds before the flow entry is removed. Defaults to no idle timeout.
- hard_timeout - Number of seconds before the flow entry is removed. Defaults to no timeout.
- actions - A list of actions to perform on matching packets (e.g., ofp_action_output)
- priority - When using non-exact (wildcarded) matches, this specifies the priority for overlapping matches. Higher values are higher priority. Not important for exact or non-overlapping entries.
- buffer_id - The buffer_id of a buffer to apply the actions to immediately. Leave unspecified for none.
- in_port - If using a buffer_id, this is the associated input port.
- match - An ofp_match object. By default, this matches everything, so you should probably set some of its fields!
Example. Create a flow_mod that sends packets from port 3 out of port 4.
fm = of.ofp_flow_mod() fm.match.in_port = 3 fm.actions.append(of.ofp_action_output(port = 4))
更详细的POX介绍，请参见https://openflow.stanford.edu/display/ONL/POX+Wiki
关于多交换机的控制器的编写请关注后续的文章。