ryu控制器源码分析-simple_switch_13.py

源码： （附注释）

# Copyright (C) 2011 Nippon Telegraph and Telephone Corporation.
#
# 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.

from ryu.base import app_manager
from ryu.controller import ofp_event
from ryu.controller.handler import CONFIG_DISPATCHER, MAIN_DISPATCHER
from ryu.controller.handler import set_ev_cls
from ryu.ofproto import ofproto_v1_3
from ryu.lib.packet import packet
from ryu.lib.packet import ethernet
from ryu.lib.packet import ether_types


class SimpleSwitch13(app_manager.RyuApp):  # 继承
    OFP_VERSIONS = [ofproto_v1_3.OFP_VERSION]

    def __init__(self, *args, **kwargs):
        super(SimpleSwitch13, self).__init__(*args, **kwargs)  # py2.7版本的书写方式
        self.mac_to_port = {}  # 用字典存储MAC地址表
 
    # 监听事件，参数是事件名和状态
    @set_ev_cls(ofp_event.EventOFPSwitchFeatures, CONFIG_DISPATCHER) 
    # switch_features_handler函数是新增缺失流表项到流表中，当封包没有匹配到流表时，就触发packet_in
    def switch_features_handler(self, ev):
        datapath = ev.msg.datapath  # datapath可认为是交换机n上发生的事
        ofproto = datapath.ofproto  # openflow协议的版本
        parser = datapath.ofproto_parser   # openflow协议的解析器

        # install table-miss flow entry
        #
        # We specify NO BUFFER to max_len of the output action due to
        # OVS bug. At this moment, if we specify a lesser number, e.g.,
        # 128, OVS will send Packet-In with invalid buffer_id and
        # truncated packet data. In that case, we cannot output packets
        # correctly.  The bug has been fixed in OVS v2.1.0.
        match = parser.OFPMatch()   # 空的，为了匹配所有的封包
        # actions是为了转送到控制器端口，参数里是发往控制器端口，不进行缓存
        actions = [parser.OFPActionOutput(ofproto.OFPP_CONTROLLER,
                                          ofproto.OFPCML_NO_BUFFER)]
        self.add_flow(datapath, 0, match, actions)  # 添加流表

    def add_flow(self, datapath, priority, match, actions, buffer_id=None):
        ofproto = datapath.ofproto
        parser = datapath.ofproto_parser
        # inst是instruction的缩写，第一个参数是马上执行动作，第二个参数是执行动作的对象
        inst = [parser.OFPInstructionActions(ofproto.OFPIT_APPLY_ACTIONS,
                                             actions)]
        mod是控制器下发的增删改查动作
        if buffer_id:
            mod = parser.OFPFlowMod(datapath=datapath, buffer_id=buffer_id,
                                    priority=priority, match=match,
                                    instructions=inst)
        else:
            mod = parser.OFPFlowMod(datapath=datapath, priority=priority,
                                    match=match, instructions=inst)
        datapath.send_msg(mod)  # 发送操作指令给交换机

    # 监听packet_in消息是否被触发，用来处理未知目的地的封包
    @set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER)
    # packet_in_handler函数是对packet_in提供信息的处理
    def _packet_in_handler(self, ev):
        # If you hit this you might want to increase
        # the "miss_send_length" of your switch
        if ev.msg.msg_len < ev.msg.total_len:
            self.logger.debug("packet truncated: only %s of %s bytes",
                              ev.msg.msg_len, ev.msg.total_len)
        msg = ev.msg
        datapath = msg.datapath
        ofproto = datapath.ofproto
        parser = datapath.ofproto_parser
        in_port = msg.match['in_port']

        pkt = packet.Packet(msg.data)
        eth = pkt.get_protocols(ethernet.ethernet)[0]

        if eth.ethertype == ether_types.ETH_TYPE_LLDP:
            # ignore lldp packet
            return
        dst = eth.dst
        src = eth.src

        dpid = datapath.id  # MAC地址表和每个交换机之间的识别，用dpid确认
        self.mac_to_port.setdefault(dpid, {})

        # 打印日志信息
        self.logger.info("packet in %s %s %s %s", dpid, src, dst, in_port)

        # 学习MAC地址，避免下次泛洪
        self.mac_to_port[dpid][src] = in_port

        if dst in self.mac_to_port[dpid]:
            out_port = self.mac_to_port[dpid][dst]
        else:
            out_port = ofproto.OFPP_FLOOD

        actions = [parser.OFPActionOutput(out_port)]

        # install a flow to avoid packet_in next time
        if out_port != ofproto.OFPP_FLOOD:
            match = parser.OFPMatch(in_port=in_port, eth_dst=dst, eth_src=src)
            # verify if we have a valid buffer_id, if yes avoid to send both
            # flow_mod & packet_out
            if msg.buffer_id != ofproto.OFP_NO_BUFFER:
                self.add_flow(datapath, 1, match, actions, msg.buffer_id)
                return
            else:
                self.add_flow(datapath, 1, match, actions)
        data = None
        if msg.buffer_id == ofproto.OFP_NO_BUFFER:
            data = msg.data

        out = parser.OFPPacketOut(datapath=datapath, buffer_id=msg.buffer_id,
                                  in_port=in_port, actions=actions, data=data)
        datapath.send_msg(out)

源码包含三块内容：继承、监听封包到来的事件、监听packet_in事件。定义了3个方法,switch_features_handler、add_flow、_packet_in_handler。

执行：

执行mininet：sudo mn --topo single,3 --mac --controller remote

# --mac作用是按MAC地址排序。

执行控制器：ryu-manager --verbose simple_switch_13.py

# --verbose作用是能看到监听的信息