network-protocols - OpenFlow Action OUTPUT 有什么作用？

Question

当我在阅读 Beacon 的一些源代码时，我被 OPAction_OUTPUT 弄糊涂了。 .
spec1.3 说

Required Action: Output. The Output action forwards a packet to a specified OpenFlow port (see 4.1). OpenFlow switches must support forwarding to physical ports, switch-defined logical ports and the required reserved ports (see 4.5).

但它混淆了两点:

第一，The Output action forwards a *packet* ，但是这个数据包是什么意思？这是否意味着 OpenFlow packet-out包含输出 Action ？或者包含在中的数据包数据字段 OpenFlow packet-out .

其次，下一步是什么？当 OpenFlow Switch 收到包含 OUTPUT 的数据包时，它们会做什么？行动？

让我举个例子:当 OFcontroller 收到一个数据包时， Controller 会做(L2 交换机):

 if dst in self.mac_to_port[dpid]:
     out_port = self.mac_to_port[dpid][dst]
 else:
     out_port = ofproto.OFPP_FLOOD
 actions = [datapath.ofproto_parser.OFPActionOutput(out_port)]
 out = datapath.ofproto_parser.OFPPacketOut(
     datapath=datapath, buffer_id=msg.buffer_id, in_port=msg.in_port,
     actions=actions)
 datapath.send_msg(out) // send out the PacketOut containing output action

所以，问题是:

Action OUTPUT输出什么在这个包出。

当 OFSwitch 在它的端口上接收到这个数据包输出时，它会做什么？

谢谢!

Answer 1

邮件列表OpenFlow-spec回答了这个问题。为了完成问题并帮助其他人，我将其发布在这里。归功于西蒙。

来自西蒙·霍曼:

An OpenFlow Packet-Out message, which is interpreted as such, would be received over an OpenFlow channel between the switch and a controller. Traffic for the channel does not run through the OpenFlow pipeline (OF1.3.2 section 6.3.1).

Thus, it would be the packet contained in the data field of the Packet-Out message which is processed by an Output action. This field would be forwarded to the OpenFlow pipeline by the switch after it receives the Packet-Out message via a channel.

If the Packet-Out message is sent via a channel then it will be decoded by the switch and the data field will be forwarded to the OpenFlow pipleline as described above.

If the Packet-Out message is not sent via a channel but rather just happens to be a packet that contains data that looks like a Packet-Out message then it will be handled directly by the OpenFlow pipeline without any special processing.