以下是10个OpenFlow的代码案例示例：

1. 控制器端创建一个流表规则：

def add_flow(datapath, priority, match, actions):
    ofproto = datapath.ofproto
    parser = datapath.ofproto_parser
    inst = [parser.OFPInstructionActions(ofproto.OFPIT_APPLY_ACTIONS,
                                         actions)]
    mod = parser.OFPFlowMod(datapath=datapath, priority=priority,
                            match=match, instructions=inst)
    datapath.send_msg(mod)

1. 控制器接收来自交换机的Packet-In消息并发送Packet-Out消息：

@set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER)
def _packet_in_handler(self, ev):
    msg = ev.msg
    dp = msg.datapath
    pkt = packet.Packet(msg.data)
    
    # 处理包并根据需要生成动作
    
    actions = [dp.ofproto_parser.OFPActionOutput(
        dp.ofproto.OFPPort.FLOOD)]
        
    out = dp.ofproto_parser.OFPPacketOut(
        datapath=dp, buffer_id=msg.buffer_id,
        in_port=msg.match['in_port'], actions=actions)
        
    dp.send_msg(out)

1. 控制器安装默认流表规则以将未匹配到的流量洪泛至所有端口：

def send_flood_rule(dp):
    ofproto = dp.ofproto
    parser = dp.ofproto_parser
    
    # 创建匹配所有流量的流表规则，输出至所有端口进行洪泛
    match = parser.OFPMatch()
    
    actions = [parser.OFPActionOutput(ofproto.OFPP_FLOOD)]
    
    # 优先级设置为0，以防止被其他规则覆盖
    add_flow(dp, 0, match, actions)

1. 控制器接收端口状态变化消息：

@set_ev_cls(ofp_event.EventOFPPortStatus, MAIN_DISPATCHER)
def _port_status_handler(self, ev):
    msg = ev.msg
    dp = msg.datapath
    
    if msg.reason == dp.ofproto.OFPPR_ADD:
        print("Port added:", msg.desc.port_no)
    elif msg.reason == dp.ofproto.OFPPR_DELETE:
        print("Port deleted:", msg.desc.port_no)
    elif msg.reason == dp.ofproto.OFPPR_MODIFY:
        print("Port modified:", msg.desc.port_no)

1. 控制器发送流量统计请求消息并处理回复：

def request_flow_stats(dp):
    ofproto = dp.ofproto
    parser = dp.ofproto_parser
    
    # 创建一个流量统计请求消息，请求所有流表的统计信息
    req = parser.OFPFlowStatsRequest(datapath=dp)
    
    # 发送请求消息至交换机，并注册回调函数处理回复
    dp.send_msg(req)

@set_ev_cls(ofp_event.EventOFPFlowStatsReply, MAIN_DISPATCHER)
def _flow_stats_reply_handler(self, ev):
    flows = []
    
    for stat in ev.msg.body:
        flow = {
            'priority': stat.priority,
            'match': stat.match,
            'actions': stat.instructions[0].actions,
            'packet_count': stat.packet_count,
            'byte_count': stat.byte_count
        }
        
        flows.append(flow)

    # 处理流量统计信息

1. 控制器接收流表规则删除消息并处理：

@set_ev_cls(ofp_event.EventOFPFlowRemoved, MAIN_DISPATCHER)
def _flow_removed_handler(self, ev):
    msg = ev.msg
    
    # 处理被删除的流表规则信息

1. 控制器发送组统计请求消息并处理回复：

def request_group_stats(dp):
    ofproto = dp.ofproto
    parser = dp.ofproto_parser
    
    # 创建一个组统计请求消息，请求所有组的统计信息
    req = parser.OFPGroupStatsRequest(datapath=dp)
    
    # 发送请求消息至交换机，并注册回调函数处理回复
    dp.send_msg(req)

@set_ev_cls(ofp_event.EventOFPGroupStatsReply, MAIN_DISPATCHER)
def _group_stats_reply_handler(self, ev):
    groups = []
    
    for stat in ev.msg.body:
        group = {
            'group_id': stat.group_id,
            'ref_count': stat.ref_count,
            'packet_count': stat.packet_count,
            'byte_count': stat.byte_count,
            'bucket_stats': stat.bucket_stats
        }
        
        groups.append(group)

    # 处理组统计信息

1. 控制器接收错误消息并处理：

@set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER)
def _error_handler(self, ev):
    msg = ev.msg
    
    if msg.reason == self.dp.ofproto.OFPR_NO_MATCH:
        print("Packet-In received due to no match")
    
    elif msg.reason == self.dp.ofproto.OFPR_ACTION:
        print("Packet-In received due to action error")
    
    elif msg.reason == self.dp.ofproto.OFPR_INVALID_TTL:
        print("Packet-In received due to invalid TTL")

    # 处理其他错误类型

1. 控制器发送端口状态查询请求消息并处理回复：

def request_port_status(dp):
    ofproto = dp.ofproto
    parser = dp.ofproto_parser
    
    req = parser.OFPPortDescStatsRequest(datapath=dp)
    
    dp.send_msg(req)

@set_ev_cls(ofp_event.EventOFPPortDescStatsReply, MAIN_DISPATCHER)
def _port_desc_stats_reply_handler(self, ev):
    ports = []
    
    for stat in ev.msg.body:
        port = {
            'port_no': stat.port_no,
            'name': stat.name,
            'mac_address': stat.hw_addr,
            'config': stat.config,
            'state': stat.state
        }
        
        ports.append(port)

    # 处理端口状态信息

1. 控制器接收交换机连接和断开事件：

@set_ev_cls(ofp_event.EventOFPStateChange, [HANDSHAKE_DISPATCHER, CONFIG_DISPATCHER, MAIN_DISPATCHER])
def _state_change_handler(self, ev):
    datapath = ev.datapath
    
    if ev.state == MAIN_DISPATCHER:
        print("Switch connected:", datapath.id)
        
    elif ev.state == DEAD_DISPATCHER:
        print("Switch disconnected:", datapath.id)

以上是一些OpenFlow的代码案例示例，可以根据具体需求进行修改和扩展。


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