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
