ryu—交换机

1. 代码解析

ryu/app/example_switch_13.py:

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

class ExampleSwitch13(app_manager.RyuApp):
    OFP_VERSIONS = [ofproto_v1_3.OFP_VERSION]

    def __init__(self, *args, **kwargs):
        super(ExampleSwitch13, self).__init__(*args, **kwargs)
        # initialize mac address table.
        self.mac_to_port = {}

    @set_ev_cls(ofp_event.EventOFPSwitchFeatures, CONFIG_DISPATCHER)
    def switch_features_handler(self, ev):
        datapath = ev.msg.datapath
        ofproto = datapath.ofproto
        parser = datapath.ofproto_parser

        # install the table-miss flow entry.
        match = parser.OFPMatch()

        # OFPCML_NO_BUFFER: 不缓冲，将发送整个数据包
        actions = [parser.OFPActionOutput(ofproto.OFPP_CONTROLLER,
                                          ofproto.OFPCML_NO_BUFFER)]
        self.add_flow(datapath, 0, match, actions)

    def add_flow(self, datapath, priority, match, actions):
        ofproto = datapath.ofproto
        parser = datapath.ofproto_parser

        # construct flow_mod message and send it.
        inst = [parser.OFPInstructionActions(ofproto.OFPIT_APPLY_ACTIONS,
                                             actions)]
        mod = parser.OFPFlowMod(datapath=datapath, priority=priority,
                                match=match, instructions=inst)
        datapath.send_msg(mod)

    @set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER)
    def _packet_in_handler(self, ev):
        msg = ev.msg
        datapath = msg.datapath
        ofproto = datapath.ofproto
        parser = datapath.ofproto_parser

        # get Datapath ID to identify OpenFlow switches.
        dpid = datapath.id
        self.mac_to_port.setdefault(dpid, {})

        # analyse the received packets using the packet library.
        pkt = packet.Packet(msg.data)
        eth_pkt = pkt.get_protocol(ethernet.ethernet)
        dst = eth_pkt.dst
        src = eth_pkt.src

        # get the received port number from packet_in message.
        in_port = msg.match['in_port']

        self.logger.info("packet in %s %s %s %s", dpid, src, dst, in_port)

        # learn a mac address to avoid FLOOD next time.
        self.mac_to_port[dpid][src] = in_port

        # if the destination mac address is already learned,
        # decide which port to output the packet, otherwise FLOOD.
        if dst in self.mac_to_port[dpid]:
            out_port = self.mac_to_port[dpid][dst]
        else:
            out_port = ofproto.OFPP_FLOOD

        # construct action list.
        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)
            self.add_flow(datapath, 1, match, actions)

        # construct packet_out message and send it.
        out = parser.OFPPacketOut(datapath=datapath,
                                  buffer_id=ofproto.OFP_NO_BUFFER,
                                  in_port=in_port, actions=actions,
                                  data=msg.data)
        datapath.send_msg(out)

• Ryu 应用需要继承 ryu.base.app_manager.RyuApp；
• OFP_VERSIONS指定支持的OpenFlow版本；
• Ryu 会自己完成交换机和控制器间的握手等初始化过程；
• 每当 Ryu 接收到一个OpenFlow消息时，便会生成对应的事件；使用 ryu.controller.handler.set_ev_cls装饰器可以指定事件处理器：
• 第一个参数指定事件类型；
• 第二个参数指定交换机状态；

状态	解释
HANDSHAKE_DISPATCHER	Exchange of HELLO message
CONFIG_DISPATCHER	Waiting to receive SwitchFeatures message
MAIN_DISPATCHER	Normal status
DEAD_DISPATCHER	Disconnection of connection

• ryu.controller.controller.Datapath类表示和控制器相连的交换机；主要属性如下，

==================================== ======================================
Attribute                            Description
==================================== ======================================
id                                   64-bit OpenFlow Datapath ID.
                                     Only available for
                                     ryu.controller.handler.MAIN_DISPATCHER
                                     phase.

ofproto                              A module which exports OpenFlow
                                     definitions, mainly constants appeared
                                     in the specification, for the
                                     negotiated OpenFlow version.  For
                                     example, ryu.ofproto.ofproto_v1_0 for
                                     OpenFlow 1.0.

ofproto_parser                       A module which exports OpenFlow wire
                                     message encoder and decoder for the
                                     negotiated OpenFlow version.
                                     For example,
                                     ryu.ofproto.ofproto_v1_0_parser
                                     for OpenFlow 1.0.

ofproto_parser.OFPxxxx(datapath,...) A callable to prepare an OpenFlow
                                     message for the given switch.  It can
                                     be sent with Datapath.send_msg later.
                                     xxxx is a name of the message.  For
                                     example OFPFlowMod for flow-mod
                                     message.  Arguemnts depend on the
                                     message.

set_xid(self, msg)                   Generate an OpenFlow XID and put it
                                     in msg.xid.

send_msg(self, msg)                  Queue an OpenFlow message to send to
                                     the corresponding switch.  If msg.xid
                                     is None, set_xid is automatically
                                     called on the message before queueing.

send_barrier                         Queue an OpenFlow barrier message to
                                     send to the switch.
==================================== ======================================

• ryu.ofproto.ofproto_v1_3_parser.OFPMatch类表示流匹配结构体；

================ =============== ==================================
Argument         Value           Description
================ =============== ==================================
in_port          Integer 32bit   Switch input port
in_phy_port      Integer 32bit   Switch physical input port
metadata         Integer 64bit   Metadata passed between tables
eth_dst          MAC address     Ethernet destination address
eth_src          MAC address     Ethernet source address
eth_type         Integer 16bit   Ethernet frame type
vlan_vid         Integer 16bit   VLAN id
vlan_pcp         Integer 8bit    VLAN priority
ip_dscp          Integer 8bit    IP DSCP (6 bits in ToS field)
ip_ecn           Integer 8bit    IP ECN (2 bits in ToS field)
ip_proto         Integer 8bit    IP protocol
ipv4_src         IPv4 address    IPv4 source address
ipv4_dst         IPv4 address    IPv4 destination address
tcp_src          Integer 16bit   TCP source port
tcp_dst          Integer 16bit   TCP destination port
udp_src          Integer 16bit   UDP source port
udp_dst          Integer 16bit   UDP destination port
sctp_src         Integer 16bit   SCTP source port
sctp_dst         Integer 16bit   SCTP destination port
icmpv4_type      Integer 8bit    ICMP type
icmpv4_code      Integer 8bit    ICMP code
arp_op           Integer 16bit   ARP opcode
arp_spa          IPv4 address    ARP source IPv4 address
arp_tpa          IPv4 address    ARP target IPv4 address
arp_sha          MAC address     ARP source hardware address
arp_tha          MAC address     ARP target hardware address
ipv6_src         IPv6 address    IPv6 source address
ipv6_dst         IPv6 address    IPv6 destination address
ipv6_flabel      Integer 32bit   IPv6 Flow Label
icmpv6_type      Integer 8bit    ICMPv6 type
icmpv6_code      Integer 8bit    ICMPv6 code
ipv6_nd_target   IPv6 address    Target address for ND
ipv6_nd_sll      MAC address     Source link-layer for ND
ipv6_nd_tll      MAC address     Target link-layer for ND
mpls_label       Integer 32bit   MPLS label
mpls_tc          Integer 8bit    MPLS TC
mpls_bos         Integer 8bit    MPLS BoS bit
pbb_isid         Integer 24bit   PBB I-SID
tunnel_id        Integer 64bit   Logical Port Metadata
ipv6_exthdr      Integer 16bit   IPv6 Extension Header pseudo-field
pbb_uca          Integer 8bit    PBB UCA header field
                                 (EXT-256 Old version of ONF Extension)
tcp_flags        Integer 16bit   TCP flags
                                 (EXT-109 ONF Extension)
actset_output    Integer 32bit   Output port from action set metadata
                                 (EXT-233 ONF Extension)
================ =============== ==================================

• ryu.ofproto.ofproto_v1_3_parser.OFPFlowMod类表示Flow Mod消息，即修改流项；支持以下参数：

================ ======================================================
Attribute        Description
================ ======================================================
cookie           Opaque controller-issued identifier
cookie_mask      Mask used to restrict the cookie bits that must match
                 when the command is OPFFC_MODIFY* or
                 OFPFC_DELETE*

table_id         ID of the table to put the flow in

command          One of the following values.
                 | OFPFC_ADD
                 | OFPFC_MODIFY
                 | OFPFC_MODIFY_STRICT
                 | OFPFC_DELETE
                 | OFPFC_DELETE_STRICT

idle_timeout     Idle time before discarding (seconds)
hard_timeout     Max time before discarding (seconds)

priority         Priority level of flow entry

buffer_id        Buffered packet to apply to (or OFP_NO_BUFFER)

out_port         For OFPFC_DELETE* commands, require matching
                 entries to include this as an output port

out_group        For OFPFC_DELETE* commands, require matching
                 entries to include this as an output group

flags            Bitmap of the following flags.
                 | OFPFF_SEND_FLOW_REM
                 | OFPFF_CHECK_OVERLAP
                 | OFPFF_RESET_COUNTS
                 | OFPFF_NO_PKT_COUNTS
                 | OFPFF_NO_BYT_COUNTS

match            Instance of OFPMatch
instructions     list of OFPInstruction* instance
================ ======================================================

• ryu.ofproto.ofproto_v1_3_parser.OFPPacketIn类表示Packet-In消息，即交换机发向控制器；包含以下属性：

============= =========================================================
Attribute     Description
============= =========================================================
buffer_id     ID assigned by datapath
total_len     Full length of frame
reason        Reason packet is being sent.
              | OFPR_NO_MATCH
              | OFPR_ACTION
              | OFPR_INVALID_TTL

table_id      ID of the table that was looked up
cookie        Cookie of the flow entry that was looked up
match         Instance of OFPMatch
data          Ethernet frame
============= =========================================================

• ryu.ofproto.ofproto_v1_3_parser.OFPPacketOut类表示Packet-Out消息，即控制器发向交换机；包含以下属性：

================ ======================================================
Attribute        Description
================ ======================================================
buffer_id        ID assigned by datapath (OFP_NO_BUFFER if none)
in_port          Packet's input port or OFPP_CONTROLLER
actions          list of OpenFlow action class
data             Packet data of a binary type value or
                 an instances of packet.Packet.
================ ======================================================

• ryu.ofproto.ofproto_v1_3_parser.OFPActionOutput类表示输出动作；支持以下参数：

================ ======================================================
Attribute        Description
================ ======================================================
port             Output port
max_len          Max length to send to controller
================ ======================================================

• ryu.ofproto.ofproto_v1_3_parser.OFPInstructionActions 表示写/应用/清空 actions 的指令：

================ ======================================================
Attribute        Description
================ ======================================================
type             One of following values.
                 | OFPIT_WRITE_ACTIONS
                 | OFPIT_APPLY_ACTIONS
                 | OFPIT_CLEAR_ACTIONS

actions          list of OpenFlow action class
================ ======================================================

• 支持的指令如下：

OFPIT_GOTO_TABLE = 1            # Setup the next table in the lookup pipeline.
OFPIT_WRITE_METADATA = 2        # Setup the metadata field for use later in
                                # pipeline.
OFPIT_WRITE_ACTIONS = 3         # Write the action(s) onto the datapath
                                # action set
OFPIT_APPLY_ACTIONS = 4         # Applies the action(s) immediately
OFPIT_CLEAR_ACTIONS = 5         # Clears all actions from the datapath action
                                # set
OFPIT_METER = 6                 # Apply meter (rate limiter)
OFPIT_EXPERIMENTER = 0xFFFF     # Experimenter instruction

2. 运行

# --topo sigle,3: 单个交换机，3个主机
# --mac: 自动设置主机的MAC地址
# --switch ovsk: 使用 ovs
# --controller remote: 使用外部OpenFlow控制器
# -x: 启动xterm
$ sudo mn --topo single,3 --mac --switch ovsk --controller remote -x

此时会启动5个xterm：h1~h3, switch, controller.

设置OpenFlow版本：switch: s1

# ovs-vsctl set Bridge s1 protocols=OpenFlow13

启动控制器：controller: c0

# ryu-manager --verbose ryu/app/example_switch_13.py

查看Table-miss流项：switch: s1

# ovs-ofctl -O OpenFlow13 dump-flows s1

ping:

mininet> h1 ping -c1 h2

再次查看流项：switch: s1

# ovs-ofctl -O OpenFlow13 dump-flows s1

参考资料

https://osrg.github.io/ryu-book/en/Ryubook.pdf