SDN功能实现（五）---修改Ryu源码实现自定义openflow基本字段（延迟更新）

回顾：struct 类型表

Format	C Type	Python type	Standard size	Notes
x	pad byte	no value
c	char	string of length 1	1
b	signed char	integer	1	(3)
B	unsigned char	integer	1	(3)
?	_Bool	bool	1	(1)
h	short	integer	2	(3)
H	unsigned short	integer	2	(3)
i	int	integer	4	(3)
I	unsigned int	integer	4	(3)
l	long	integer	4	(3)
L	unsigned long	integer	4	(3)
q	long long	integer	8	(2), (3)
Q	unsigned long long	integer	8	(2), (3)
f	float	float	4	(4)
d	double	float	8	(4)
s	char[]	string	1
p	char[]	string
P	void *	integer		(5), (3)

一：修改ofproto_v1_3.py中的_OFP_FLOW_MOD_PACK_STR0格式

_OFP_FLOW_MOD_PACK_STR0 = 'QQBBHHHIIIH2xQQ' #8 8 1 1 2 2 2 4 4 4 2 2 8 8= 40 + 8 + 8 = 56
OFP_FLOW_MOD_PACK_STR = '!' + _OFP_FLOW_MOD_PACK_STR0 + _OFP_MATCH_PACK_STR #_OFP_MATCH_PACK_STR = 'HHBBBB' 2 2 1 1 1 1 = 8
OFP_FLOW_MOD_PACK_STR0 = '!' + _OFP_FLOW_MOD_PACK_STR0
OFP_FLOW_MOD_SIZE = 72
assert (calcsize(OFP_FLOW_MOD_PACK_STR) + OFP_HEADER_SIZE ==
        OFP_FLOW_MOD_SIZE) #OFP_HEADER_SIZE = 8

“QQ”表示新自定义的两个字段effect_sec和effect_usec，各自占64位！！

72表示OFP_FLOW_MOD_SIZE，为OFP_HEADER_SIZE=8 + _OFP_FLOW_MOD_PACK_STR0=56 + _OFP_MATCH_PACK_STR=8 === 72

二：修改ofproto_v1_3_parser.py文件

@_register_parser
@_set_msg_type(ofproto.OFPT_FLOW_MOD)
class OFPFlowMod(MsgBase):
    """
    Modify Flow entry message

    The controller sends this message to modify the flow table.

    ================ ======================================================
    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
    ================ ======================================================

    Example::

        def send_flow_mod(self, datapath):
            ofp = datapath.ofproto
            ofp_parser = datapath.ofproto_parser

            cookie = cookie_mask = 0
            table_id = 0
            idle_timeout = hard_timeout = 0
            priority = 32768
            buffer_id = ofp.OFP_NO_BUFFER
            match = ofp_parser.OFPMatch(in_port=1, eth_dst='ff:ff:ff:ff:ff:ff')
            actions = [ofp_parser.OFPActionOutput(ofp.OFPP_NORMAL, 0)]
            inst = [ofp_parser.OFPInstructionActions(ofp.OFPIT_APPLY_ACTIONS,
                                                     actions)]
            req = ofp_parser.OFPFlowMod(datapath, cookie, cookie_mask,
                                        table_id, ofp.OFPFC_ADD,
                                        idle_timeout, hard_timeout,
                                        priority, buffer_id,
                                        ofp.OFPP_ANY, ofp.OFPG_ANY,
                                        ofp.OFPFF_SEND_FLOW_REM,
                                        match, inst)
            datapath.send_msg(req)
    """

    def __init__(self, datapath, cookie=0, cookie_mask=0, table_id=0,
                 command=ofproto.OFPFC_ADD,
                 idle_timeout=0, hard_timeout=0,
                 priority=ofproto.OFP_DEFAULT_PRIORITY,
                 buffer_id=ofproto.OFP_NO_BUFFER,
                 out_port=0, out_group=0, flags=0,
                 effect_sec=0, effect_usec=0,
                 match=None,
                 instructions=None):
        instructions = instructions if instructions else []
        super(OFPFlowMod, self).__init__(datapath)
        self.cookie = cookie
        self.cookie_mask = cookie_mask
        self.table_id = table_id
        self.command = command
        self.idle_timeout = idle_timeout
        self.hard_timeout = hard_timeout
        self.priority = priority
        self.buffer_id = buffer_id
        self.out_port = out_port
        self.out_group = out_group
        self.flags = flags
        self.effect_sec = effect_sec
        self.effect_usec = effect_usec
        if match is None:
            match = OFPMatch()
        assert isinstance(match, OFPMatch)
        self.match = match
        for i in instructions:
            assert isinstance(i, OFPInstruction)
        self.instructions = instructions

    def _serialize_body(self):
        print("------_serialize_body------start-----------");
        print('======%d====%d=====',
              self.effect_sec,self.effect_usec)
        print("------_serialize_body------end-----------");
        msg_pack_into(ofproto.OFP_FLOW_MOD_PACK_STR0, self.buf,
                      ofproto.OFP_HEADER_SIZE,
                      self.cookie, self.cookie_mask, self.table_id,
                      self.command, self.idle_timeout, self.hard_timeout,
                      self.priority, self.buffer_id, self.out_port,
                      self.out_group, self.flags, 
                      self.effect_sec,self.effect_usec)

        offset = (ofproto.OFP_FLOW_MOD_SIZE -
                  ofproto.OFP_MATCH_SIZE)

        match_len = self.match.serialize(self.buf, offset)
        offset += match_len

        for inst in self.instructions:
            inst.serialize(self.buf, offset)
            offset += inst.len

    @classmethod
    def parser(cls, datapath, version, msg_type, msg_len, xid, buf):
        msg = super(OFPFlowMod, cls).parser(
            datapath, version, msg_type, msg_len, xid, buf)

        (msg.cookie, msg.cookie_mask, msg.table_id,
         msg.command, msg.idle_timeout, msg.hard_timeout,
         msg.priority, msg.buffer_id, msg.out_port,
         msg.out_group, msg.flags, 
         msg.effect_sec, msg.effect_usec) = struct.unpack_from(
            ofproto.OFP_FLOW_MOD_PACK_STR0, msg.buf,
            ofproto.OFP_HEADER_SIZE)

        print("------parser------start-----------");
        print('======%d====%d=====',
              msg.effect_sec, msg.effect_usec)
        print("------parser------end-----------");
        
        offset = ofproto.OFP_FLOW_MOD_SIZE - ofproto.OFP_HEADER_SIZE

        try:
            msg.match = OFPMatch.parser(buf, offset)
        except exception.OFPTruncatedMessage as e:
            msg.match = e.ofpmsg
            e.ofpmsg = msg
            raise e

        offset += utils.round_up(msg.match.length, 8)

        instructions = []
        try:
            while offset < msg_len:
                i = OFPInstruction.parser(buf, offset)
                instructions.append(i)
                offset += i.len
        except exception.OFPTruncatedMessage as e:
            instructions.append(e.ofpmsg)
            msg.instructions = instructions
            e.ofpmsg = msg
            raise e
        except struct.error as e:
            msg.instructions = instructions
            raise exception.OFPTruncatedMessage(ofpmsg=msg,
                                                residue=buf[offset:],
                                                original_exception=e)
        msg.instructions = instructions

        return msg

三：结合OVS+RYU实现openflow流表项的延迟更新

（一）修改simple_switch_13.py代码，添加effect_sec字段

# 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):
    OFP_VERSIONS = [ofproto_v1_3.OFP_VERSION]

    def __init__(self, *args, **kwargs):
        super(SimpleSwitch13, self).__init__(*args, **kwargs)
        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 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()
        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, buffer_id=None):
        ofproto = datapath.ofproto
        parser = datapath.ofproto_parser

        inst = [parser.OFPInstructionActions(ofproto.OFPIT_APPLY_ACTIONS,
                                             actions)]
        if buffer_id:
            mod = parser.OFPFlowMod(datapath=datapath, buffer_id=buffer_id,
                                    priority=priority, effect_sec=1625217050,
                                    match=match,
                                    instructions=inst)
        else:
            mod = parser.OFPFlowMod(datapath=datapath, priority=priority,effect_sec=1625217050,
                                    match=match, instructions=inst)
        datapath.send_msg(mod)

    @set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER)
    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 = format(datapath.id, "d").zfill(16)
        self.mac_to_port.setdefault(dpid, {})

        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 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)

（二）开启拓扑

sudo mn --topo=linear,4 --controller=remote

（三）查看控制器下发的延迟流表

（四）查看OVS延迟更新的现象

 

在流表为生效时，流表为空，当到达时间后，流表项插入，可以正常进行通信！！！