参考：Ryu拓扑发现原理分析（ryu/topology/switches.py)，通过对该文件的分析，可以更好的了解数据平面中设备信息
一：拓扑成员类分析
（一）Port类
class Port(object): # This is data class passed by EventPortXXX def __init__(self, dpid, ofproto, ofpport): super(Port, self).__init__() self.dpid = dpid self._ofproto = ofproto self._config = ofpport.config self._state = ofpport.state self.port_no = ofpport.port_no self.hw_addr = ofpport.hw_addr self.name = ofpport.name def is_reserved(self): return self.port_no > self._ofproto.OFPP_MAX def is_down(self): return (self._state & self._ofproto.OFPPS_LINK_DOWN) > 0 or (self._config & self._ofproto.OFPPC_PORT_DOWN) > 0 def is_live(self): # NOTE: OF1.2 has OFPPS_LIVE state # return (self._state & self._ofproto.OFPPS_LIVE) > 0 return not self.is_down() def to_dict(self): return {'dpid': dpid_to_str(self.dpid), 'port_no': port_no_to_str(self.port_no), 'hw_addr': self.hw_addr, 'name': self.name.decode('utf-8')} # for Switch.del_port() def __eq__(self, other): return self.dpid == other.dpid and self.port_no == other.port_no def __ne__(self, other): return not self.__eq__(other) def __hash__(self): return hash((self.dpid, self.port_no)) def __str__(self): LIVE_MSG = {False: 'DOWN', True: 'LIVE'} return 'Port<dpid=%s, port_no=%s, %s>' % (self.dpid, self.port_no, LIVE_MSG[self.is_live()])
存储端口相关信息，数据成员有：
self.dpid = dpid self._ofproto = ofproto self._config = ofpport.config self._state = ofpport.state self.port_no = ofpport.port_no self.hw_addr = ofpport.hw_addr self.name = ofpport.name
其中要特别注意的是dpid和port_no，即交换机ID和端口号，这两个信息在下发流表项时很重要。
（二）Switch类
class Switch(object): # This is data class passed by EventSwitchXXX def __init__(self, dp): super(Switch, self).__init__() self.dp = dp self.ports = [] def add_port(self, ofpport): port = Port(self.dp.id, self.dp.ofproto, ofpport) if not port.is_reserved(): self.ports.append(port) def del_port(self, ofpport): self.ports.remove(Port(ofpport)) def to_dict(self): d = {'dpid': dpid_to_str(self.dp.id), 'ports': [port.to_dict() for port in self.ports]} return d def __str__(self): msg = 'Switch<dpid=%s, ' % self.dp.id for port in self.ports: msg += str(port) + ' ' msg += '>' return msg
存储交换机相关信息，数据成员有：
self.dp = dp self.ports = []
其中dp是Datapath类的实例，该类定义在在ryu/controller/controller.py，主要属性有：
self.socket = socket self.address = address self.is_active = True self.id = None # datapath_id is unknown yet self.ports = None
ports是一个由Port类实例组成的列表，存储该交换机的端口。
（三）Link类:
class Link(object): # This is data class passed by EventLinkXXX def __init__(self, src, dst): super(Link, self).__init__() self.src = src self.dst = dst def to_dict(self): d = {'src': self.src.to_dict(), 'dst': self.dst.to_dict()} return d # this type is used for key value of LinkState def __eq__(self, other): return self.src == other.src and self.dst == other.dst def __ne__(self, other): return not self.__eq__(other) def __hash__(self): return hash((self.src, self.dst)) def __str__(self): return 'Link: %s to %s' % (self.src, self.dst)
保存的是源端口和目的端口（都是Port类实例），数据成员有：
self.src = src
self.dst = dst
（四）PortState类
class PortState(dict): # dict: int port_no -> OFPPort port # OFPPort is defined in ryu.ofproto.ofproto_v1_X_parser def __init__(self): super(PortState, self).__init__() def add(self, port_no, port): self[port_no] = port def remove(self, port_no): del self[port_no] def modify(self, port_no, port): self[port_no] = port
该类继承自dict，保存了从port_no（int型）到port（OFPPort类实例）的映射。
该类主要用作self.port_state字典的值（键是dpid），用于存储dpid对应的交换机的所有端口情况。
OFPPort类定义在ryu/ofproto目录下对应的ofproto_v1_X_parser.py中（X代表版本号），继承自一个namedtuple，保存有port_no等信息。
（五）PortData类
class PortData(object): def __init__(self, is_down, lldp_data): super(PortData, self).__init__() self.is_down = is_down self.lldp_data = lldp_data self.timestamp = None self.sent = 0 def lldp_sent(self): self.timestamp = time.time() self.sent += 1 def lldp_received(self): self.sent = 0 def lldp_dropped(self): return self.sent def clear_timestamp(self): self.timestamp = None def set_down(self, is_down): self.is_down = is_down def __str__(self): return 'PortData<live=%s, timestamp=%s, sent=%d>' % (not self.is_down, self.timestamp, self.sent)
保存每个端口与对应的LLDP报文数据，数据成员有：
self.is_down = is_down self.lldp_data = lldp_data（这是LLDP报文的数据） self.timestamp = None self.sent = 0
每调用一次lldp_sent函数，便会把self.timestamp置为当前的时间（time.time()），并将self.sent加1；每调用一次lldp_received函数，便会把self.sent置为0。
（六）PortDataState类
class PortDataState(dict): # dict: Port class -> PortData class # slimed down version of OrderedDict as python 2.6 doesn't support it. _PREV = 0 _NEXT = 1 _KEY = 2 def __init__(self): super(PortDataState, self).__init__() self._root = root = [] # sentinel node root[:] = [root, root, None] # [_PREV, _NEXT, _KEY] doubly linked list self._map = {} def _remove_key(self, key): link_prev, link_next, key = self._map.pop(key) link_prev[self._NEXT] = link_next link_next[self._PREV] = link_prev def _append_key(self, key): root = self._root last = root[self._PREV] last[self._NEXT] = root[self._PREV] = self._map[key] = [last, root, key] def _prepend_key(self, key): root = self._root first = root[self._NEXT] first[self._PREV] = root[self._NEXT] = self._map[key] = [root, first, key] def _move_last_key(self, key): self._remove_key(key) self._append_key(key) def _move_front_key(self, key): self._remove_key(key) self._prepend_key(key) def add_port(self, port, lldp_data): if port not in self: self._prepend_key(port) self[port] = PortData(port.is_down(), lldp_data) #为端口添加LLDP报文 else: self[port].is_down = port.is_down() def lldp_sent(self, port): port_data = self[port] #获取了PortData类实例 port_data.lldp_sent() #设置了timestamp和sent标识+1 self._move_last_key(port) #循环列表，前面移动到后面 return port_data #返回PortData类实例 def lldp_received(self, port): self[port].lldp_received() def move_front(self, port): port_data = self.get(port, None) if port_data is not None: port_data.clear_timestamp() self._move_front_key(port) def set_down(self, port): is_down = port.is_down() port_data = self[port] port_data.set_down(is_down) port_data.clear_timestamp() if not is_down: self._move_front_key(port) return is_down def get_port(self, port): return self[port] def del_port(self, port): del self[port] self._remove_key(port) def __iter__(self): root = self._root curr = root[self._NEXT] while curr is not root: yield curr[self._KEY] curr = curr[self._NEXT] def clear(self): for node in self._map.values(): del node[:] root = self._root root[:] = [root, root, None] self._map.clear() dict.clear(self) def items(self): 'od.items() -> list of (key, value) pairs in od' return [(key, self[key]) for key in self] def iteritems(self): 'od.iteritems -> an iterator over the (key, value) pairs in od' for k in self: yield (k, self[k])
继承自dict类，保存从Port类到PortData类的映射。该类维护了一个类似双向循环链表的数据结构，并重写了__iter__()，使得遍历该类的实例（self.ports）时，会按照该双向循环链表从哨兵节点（self._root）后一个节点开始遍历。
包含一个add_port函数，传入port和lldp_data，port作键，构建的PortData类实例作为值。
包含一个lldp_sent(self,port)函数，根据传入的port（Port类实例）获得对应的PortData类实例port_data，然后调用port_data.lldp_sent()（该函数会设置时间戳），再调用self._move_last_key(port)，把该port移到类似双向循环链表的数据结构中哨兵节点的前面（相当于下次遍历的末尾）；最后返回port_data。
（七）LinkState类
class LinkState(dict): # dict: Link class -> timestamp def __init__(self): super(LinkState, self).__init__() self._map = {} def get_peer(self, src): return self._map.get(src, None) def update_link(self, src, dst): link = Link(src, dst) self[link] = time.time() self._map[src] = dst # return if the reverse link is also up or not rev_link = Link(dst, src) return rev_link in self def link_down(self, link): del self[link] del self._map[link.src] def rev_link_set_timestamp(self, rev_link, timestamp): # rev_link may or may not in LinkSet if rev_link in self: self[rev_link] = timestamp def port_deleted(self, src): dst = self.get_peer(src) if dst is None: raise KeyError() link = Link(src, dst) rev_link = Link(dst, src) del self[link] del self._map[src] # reverse link might not exist self.pop(rev_link, None) rev_link_dst = self._map.pop(dst, None) return dst, rev_link_dst
继承自dict，保存从Link类到时间戳的映射。数据成员self._map字典用于存储Link两端互相映射的关系。
（八）LLDPPacket类
class LLDPPacket(object): # make a LLDP packet for link discovery. CHASSIS_ID_PREFIX = 'dpid:' CHASSIS_ID_PREFIX_LEN = len(CHASSIS_ID_PREFIX) CHASSIS_ID_FMT = CHASSIS_ID_PREFIX + '%s' PORT_ID_STR = '!I' # uint32_t PORT_ID_SIZE = 4 class LLDPUnknownFormat(RyuException): message = '%(msg)s' @staticmethod def lldp_packet(dpid, port_no, dl_addr, ttl): pkt = packet.Packet() #生成数据包 dst = lldp.LLDP_MAC_NEAREST_BRIDGE src = dl_addr ethertype = ETH_TYPE_LLDP eth_pkt = ethernet.ethernet(dst, src, ethertype) pkt.add_protocol(eth_pkt) #构造数据 tlv_chassis_id = lldp.ChassisID( subtype=lldp.ChassisID.SUB_LOCALLY_ASSIGNED, chassis_id=(LLDPPacket.CHASSIS_ID_FMT % dpid_to_str(dpid)).encode('ascii')) tlv_port_id = lldp.PortID(subtype=lldp.PortID.SUB_PORT_COMPONENT, port_id=struct.pack( LLDPPacket.PORT_ID_STR, port_no)) tlv_ttl = lldp.TTL(ttl=ttl) tlv_end = lldp.End() tlvs = (tlv_chassis_id, tlv_port_id, tlv_ttl, tlv_end) lldp_pkt = lldp.lldp(tlvs) pkt.add_protocol(lldp_pkt) pkt.serialize() return pkt.data @staticmethod def lldp_parse(data): pkt = packet.Packet(data) i = iter(pkt) eth_pkt = six.next(i) assert type(eth_pkt) == ethernet.ethernet lldp_pkt = six.next(i) if type(lldp_pkt) != lldp.lldp: raise LLDPPacket.LLDPUnknownFormat() tlv_chassis_id = lldp_pkt.tlvs[0] if tlv_chassis_id.subtype != lldp.ChassisID.SUB_LOCALLY_ASSIGNED: raise LLDPPacket.LLDPUnknownFormat( msg='unknown chassis id subtype %d' % tlv_chassis_id.subtype) chassis_id = tlv_chassis_id.chassis_id.decode('utf-8') if not chassis_id.startswith(LLDPPacket.CHASSIS_ID_PREFIX): raise LLDPPacket.LLDPUnknownFormat( msg='unknown chassis id format %s' % chassis_id) src_dpid = str_to_dpid(chassis_id[LLDPPacket.CHASSIS_ID_PREFIX_LEN:]) tlv_port_id = lldp_pkt.tlvs[1] if tlv_port_id.subtype != lldp.PortID.SUB_PORT_COMPONENT: raise LLDPPacket.LLDPUnknownFormat( msg='unknown port id subtype %d' % tlv_port_id.subtype) port_id = tlv_port_id.port_id if len(port_id) != LLDPPacket.PORT_ID_SIZE: raise LLDPPacket.LLDPUnknownFormat( msg='unknown port id %d' % port_id) (src_port_no, ) = struct.unpack(LLDPPacket.PORT_ID_STR, port_id) return src_dpid, src_port_no
静态方法lldp_packet(dpid,port_no,dl_addr,ttl)用于构造LLDP报文，静态方法lldp_parse(data)用于解析LLDP包，并返回源DPID和源端口号。
二：分析Switches类拓扑发现
（一）类成员分析
该类是Ryu拓扑发现的核心所在。Switches类是app_manager.RyuApp类的子类，当运行switches应用时会被实例化，其__init__函数主要包括：
class Switches(app_manager.RyuApp): OFP_VERSIONS = [ofproto_v1_0.OFP_VERSION, ofproto_v1_2.OFP_VERSION, ofproto_v1_3.OFP_VERSION, ofproto_v1_4.OFP_VERSION] _EVENTS = [event.EventSwitchEnter, event.EventSwitchLeave, event.EventSwitchReconnected, event.EventPortAdd, event.EventPortDelete, event.EventPortModify, event.EventLinkAdd, event.EventLinkDelete, event.EventHostAdd] DEFAULT_TTL = 120 # unused. ignored. LLDP_PACKET_LEN = len(LLDPPacket.lldp_packet(0, 0, DONTCARE_STR, 0)) LLDP_SEND_GUARD = .05 LLDP_SEND_PERIOD_PER_PORT = .9 TIMEOUT_CHECK_PERIOD = 5. LINK_TIMEOUT = TIMEOUT_CHECK_PERIOD * 2 LINK_LLDP_DROP = 5 def __init__(self, *args, **kwargs): super(Switches, self).__init__(*args, **kwargs) self.name = 'switches' self.dps = {} #self.dps字典用于保存dpid到Datapath类实例的映射，会在_register函数中添加新成员，_unregister函数中删除成员。遍历该字典可以得到连接的所有交换机。 self.port_state = {} #字典中键为dpid，值为PortState类型。遍历该字典可以得到所有交换机对应的端口情况。当交换机连接时，会检查交换机的id是否在self.port_state中，不在则创建PortState类实例，把交换机的所有端口号和端口存储到该实例中；交换机断开时，会从self.port_state中删除。 self.ports = PortDataState() #self.ports是PortDataState类的实例，保存每个端口（Port类型）对应的LLDP报文数据（保存在PortData类实例中），遍历self.ports用于发送LLDP报文。 self.links = LinkState() #self.links是LinkState类的实例，保存所有连接（Link类型）到时间戳的映射。遍历self.links的键即可得到所有交换机之间的连接情况。 self.hosts = HostState() # mac address -> Host class list self.is_active = True self.link_discovery = self.CONF.observe_links if self.link_discovery: #如果ryu-manager启动时加了--observe-links参数，则下面的self.link_discovery将为真，从而执行if下面的语句： self.install_flow = self.CONF.install_lldp_flow self.explicit_drop = self.CONF.explicit_drop self.lldp_event = hub.Event() self.link_event = hub.Event() self.threads.append(hub.spawn(self.lldp_loop)) self.threads.append(hub.spawn(self.link_loop))
综上所述，该初始化函数__init__()主要是创建用于存储相关信息的数据结构，创建两个事件，然后调用hub.spawn创建两个新线程执行self.lldp_loop和self.link_loop两个函数。
（二）其他成员方法
def close(self): self.is_active = False if self.link_discovery: self.lldp_event.set() self.link_event.set() hub.joinall(self.threads) def _register(self, dp): assert dp.id is not None self.dps[dp.id] = dp if dp.id not in self.port_state: self.port_state[dp.id] = PortState() for port in dp.ports.values(): self.port_state[dp.id].add(port.port_no, port) #遍历dp.ports.values，将所有port（OFPPort类型）添加到该PortState实例中。 def _unregister(self, dp): if dp.id in self.dps: if (self.dps[dp.id] == dp): del self.dps[dp.id] del self.port_state[dp.id] def _get_switch(self, dpid): if dpid in self.dps: switch = Switch(self.dps[dpid]) for ofpport in self.port_state[dpid].values(): switch.add_port(ofpport) return switch def _get_port(self, dpid, port_no): switch = self._get_switch(dpid) if switch: for p in switch.ports: if p.port_no == port_no: return p def _port_added(self, port): lldp_data = LLDPPacket.lldp_packet( #调用静态方法，构建LLDP数据报文 port.dpid, port.port_no, port.hw_addr, self.DEFAULT_TTL) self.ports.add_port(port, lldp_data) #将数据添加到端口中 # LOG.debug('_port_added dpid=%s, port_no=%s, live=%s', # port.dpid, port.port_no, port.is_live()) def _link_down(self, port): try: dst, rev_link_dst = self.links.port_deleted(port) except KeyError: # LOG.debug('key error. src=%s, dst=%s', # port, self.links.get_peer(port)) return link = Link(port, dst) self.send_event_to_observers(event.EventLinkDelete(link)) if rev_link_dst: rev_link = Link(dst, rev_link_dst) self.send_event_to_observers(event.EventLinkDelete(rev_link)) self.ports.move_front(dst) def _is_edge_port(self, port): for link in self.links: if port == link.src or port == link.dst: return False return True
（三）交换机之间链路连接信息探测：发送（1）lldp_loop方法---由初始化函数中线程方法进行管理调用
def lldp_loop(self): while self.is_active: self.lldp_event.clear() now = time.time() #当前时刻 timeout = None ports_now = [] ports = [] for (key, data) in self.ports.items(): #遍历self.ports(PortDataState类的实例)，获得key（Port类实例）和data（PortData类实例） if data.timestamp is None: #如果data.timestamp为None（该端口还没发送过LLDP报文） ports_now.append(key) #则将key（端口）加入ports_now列表； continue #------------ expire = data.timestamp + self.LLDP_SEND_PERIOD_PER_PORT #否则，计算下次应该发送LLDP报文的时间expire if expire <= now: #如果已经超时，则放到ports列表-----表示本来就应该发送下一次LLDP了 ports.append(key) continue #------------ timeout = expire - now #获取timeout时间,表示还差多久到达期望的时间expire，进行LLDP数据包发送 break #否则就是还没到发送时间，停止遍历 #（发送LLDP报文时是按序发的，找到第一个未超时的端口，后面的端口肯定更没有超时， #因为后面端口上次发送LLDP是在前一端口之后，前一个都没超时后面的自然也没超时） #注意：列表中都是按序的，先发ports_now中还没有发送过LLDP数据的Port实例（data.timestamp为None), #然后查看已经发送过,但是已经超时（及本来应该进行下一次发送的）ports中的Port实例for port in ports_now: #遍历ports_now列表，对每个端口调用self.send_lldp_packet(port)，发送LLDP报文 self.send_lldp_packet(port) #--------发送LLDP报文 for port in ports: #遍历ports列表，对每个端口调用self.send_lldp_packet(port)，发送LLDP报文 self.send_lldp_packet(port) #--------发送LLDP报文 hub.sleep(self.LLDP_SEND_GUARD) # don't burst 设置睡眠时间，防止回送数据太多，导致出现等待时延 if timeout is not None and ports: #timeout!=None表示：还有端口Port实例没有到达下一次发送LLDP报文的时机 Ports表示:本来应该发生LLDP报文的Port实例（超过本来周期）--上面发送过 timeout = 0 # We have already slept ---- ？？设置为0---主要为了避免None在下面wait中出错 # LOG.debug('lldp sleep %s', timeout) self.lldp_event.wait(timeout=timeout) #事件等待timeout时刻
（四）交换机之间链路连接信息探测：发送（2）send_lldp_packet方法---由lldp_loop函数调用
def send_lldp_packet(self, port): try: #！！！--------！！！重点：在发送时我们会将当前时刻保存在self.timestamp = time.time()中，后面我们接收到LLDP数据包时， #！！！--------！！！重点：到对应端口中获取timestamp,然后现在时刻-timestamp获得LLDP测量的C-S-S-C时间！！！ port_data = self.ports.lldp_sent(port) #调用PortDataState类的lldp_sent函数，该函数会设置时间戳， #移动相应端口在双向循环链表中的位置，最后返回PortData类实例port_data。 except KeyError: # ports can be modified during our sleep in self.lldp_loop() # LOG.debug('send_lld error', exc_info=True) return if port_data.is_down: #如果该端口已经down掉，直接返回，否则执行下一步 return dp = self.dps.get(port.dpid, None) #获取了datapath实例 if dp is None: #根据port.dpid得到对应的Datapath类实例dp，如果不存在，则直接返回，否则执行下一步 # datapath was already deleted return # LOG.debug('lldp sent dpid=%s, port_no=%d', dp.id, port.port_no) # TODO:XXX #发送LLDP报文。具体地： #(1)生成actions：从port.port_no端口发出消息； #(2)生成PacketOut消息：datapath指定为上一步得到的dp，actions为前面的，data为步骤a中返回的port_data的lldp_data if dp.ofproto.OFP_VERSION == ofproto_v1_0.OFP_VERSION: actions = [dp.ofproto_parser.OFPActionOutput(port.port_no)] dp.send_packet_out(actions=actions, data=port_data.lldp_data) elif dp.ofproto.OFP_VERSION >= ofproto_v1_2.OFP_VERSION: actions = [dp.ofproto_parser.OFPActionOutput(port.port_no)] #设置actions out = dp.ofproto_parser.OFPPacketOut( #下发LLDP数据 datapath=dp, in_port=dp.ofproto.OFPP_CONTROLLER, buffer_id=dp.ofproto.OFP_NO_BUFFER, actions=actions, data=port_data.lldp_data) #PortData类实例的lldp_data数据 dp.send_msg(out) else: LOG.error('cannot send lldp packet. unsupported version. %x', dp.ofproto.OFP_VERSION)
（五）交换机之间链路连接信息探测：接收（1）state_change_handler方法---由事件触发函数调用（下发流表!!!）
@set_ev_cls(ofp_event.EventOFPStateChange, [MAIN_DISPATCHER, DEAD_DISPATCHER]) #该函数用于处理EventOFPStateChange事件，当交换机连接或者断开时会触发该事件。 def state_change_handler(self, ev): dp = ev.datapath assert dp is not None LOG.debug(dp) if ev.state == MAIN_DISPATCHER: #如果状态是MAIN_DISPATCHER： dp_multiple_conns = False if dp.id in self.dps: #(1)从ev.datapath获得Datapath类实例dp，如果该dp的dpid已经在self.dps里有，则报出重复链接的警告。 LOG.warning('Multiple connections from %s', dpid_to_str(dp.id)) dp_multiple_conns = True (self.dps[dp.id]).close() #(2)调用_register()，将dp.id和dp添加到self.dps中； #如果该dp.id不在self.port_state中，则创建该dp.id对应的PortState实例， #并遍历dp.ports.values，将所有port（OFPPort类型）添加到该PortState实例中。 self._register(dp) #(3)调用_get_switch()，如果dp.id在self.dps中，则创建一个Switch类实例， #并把self.port_state中对应的端口都添加到该实例中，最终返回该实例。 switch = self._get_switch(dp.id) LOG.debug('register %s', switch) if not dp_multiple_conns: #(4)如果交换机没有重复连接，触发EventSwitchEnter事件。 self.send_event_to_observers(event.EventSwitchEnter(switch)) else: evt = event.EventSwitchReconnected(switch) self.send_event_to_observers(evt) if not self.link_discovery: #(5)如果没设置self.link_discovery，返回；否则执行下一步。 return #(6)如果设置了self.install_flow，则根据OpenFlow版本生成相应流表项， #使得收到的LLDP报文（根据目的MAC地址匹配）上报给控制器。 if self.install_flow: ofproto = dp.ofproto ofproto_parser = dp.ofproto_parser # TODO:XXX need other versions if ofproto.OFP_VERSION == ofproto_v1_0.OFP_VERSION: rule = nx_match.ClsRule() rule.set_dl_dst(addrconv.mac.text_to_bin( lldp.LLDP_MAC_NEAREST_BRIDGE)) rule.set_dl_type(ETH_TYPE_LLDP) actions = [ofproto_parser.OFPActionOutput( ofproto.OFPP_CONTROLLER, self.LLDP_PACKET_LEN)] dp.send_flow_mod( rule=rule, cookie=0, command=ofproto.OFPFC_ADD, idle_timeout=0, hard_timeout=0, actions=actions, priority=0xFFFF) elif ofproto.OFP_VERSION >= ofproto_v1_2.OFP_VERSION: match = ofproto_parser.OFPMatch( eth_type=ETH_TYPE_LLDP, eth_dst=lldp.LLDP_MAC_NEAREST_BRIDGE) #重点：设置match---交换机获取得到以太网LLDP数据包（由另一个交换机转发而来）！！！！！ # OFPCML_NO_BUFFER is set so that the LLDP is not # buffered on switch parser = ofproto_parser actions = [parser.OFPActionOutput(ofproto.OFPP_CONTROLLER, ofproto.OFPCML_NO_BUFFER )] #设置actions,当第二个交换机获取到LLDP数据后，不需要缓存LLDP数据，全部上交给控制器 inst = [parser.OFPInstructionActions( ofproto.OFPIT_APPLY_ACTIONS, actions)] mod = parser.OFPFlowMod(datapath=dp, match=match, idle_timeout=0, hard_timeout=0, instructions=inst, priority=0xFFFF) # 标识流表的优先级，范围为0-65535，值越大，优先级越高 dp.send_msg(mod) #发送给datapath else: LOG.error('cannot install flow. unsupported version. %x', dp.ofproto.OFP_VERSION) # Do not add ports while dp has multiple connections to controller. if not dp_multiple_conns: for port in switch.ports: if not port.is_reserved(): self._port_added(port) self.lldp_event.set() elif ev.state == DEAD_DISPATCHER: # dp.id is None when datapath dies before handshake if dp.id is None: return switch = self._get_switch(dp.id) if switch: if switch.dp is dp: self._unregister(dp) LOG.debug('unregister %s', switch) evt = event.EventSwitchLeave(switch) self.send_event_to_observers(evt) if not self.link_discovery: return for port in switch.ports: if not port.is_reserved(): self.ports.del_port(port) self._link_down(port) self.lldp_event.set()
（六）交换机之间链路连接信息探测：接收（2）lldp_packet_in_handler方法---由事件触发函数调用
@set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER) def lldp_packet_in_handler(self, ev): if not self.link_discovery: return msg = ev.msg try: src_dpid, src_port_no = LLDPPacket.lldp_parse(msg.data) #解析lldp数据包，获取src_dpid和src_port_no except LLDPPacket.LLDPUnknownFormat: # This handler can receive all the packets which can be # not-LLDP packet. Ignore it silently return dst_dpid = msg.datapath.id #获取目的datapath的dst_dpid if msg.datapath.ofproto.OFP_VERSION == ofproto_v1_0.OFP_VERSION: dst_port_no = msg.in_port #获取目的datapath的dst_port_no elif msg.datapath.ofproto.OFP_VERSION >= ofproto_v1_2.OFP_VERSION: dst_port_no = msg.match['in_port'] else: LOG.error('cannot accept LLDP. unsupported version. %x', msg.datapath.ofproto.OFP_VERSION) src = self._get_port(src_dpid, src_port_no) if not src or src.dpid == dst_dpid: return try: self.ports.lldp_received(src) except KeyError: # There are races between EventOFPPacketIn and # EventDPPortAdd. So packet-in event can happend before # port add event. In that case key error can happend. # LOG.debug('lldp_received error', exc_info=True) pass dst = self._get_port(dst_dpid, dst_port_no) if not dst: return old_peer = self.links.get_peer(src) # LOG.debug("Packet-In") # LOG.debug(" src=%s", src) # LOG.debug(" dst=%s", dst) # LOG.debug(" old_peer=%s", old_peer) if old_peer and old_peer != dst: old_link = Link(src, old_peer) del self.links[old_link] self.send_event_to_observers(event.EventLinkDelete(old_link)) link = Link(src, dst) if link not in self.links: self.send_event_to_observers(event.EventLinkAdd(link)) # remove hosts if it's not attached to edge port host_to_del = [] for host in self.hosts.values(): if not self._is_edge_port(host.port): host_to_del.append(host.mac) for host_mac in host_to_del: del self.hosts[host_mac] if not self.links.update_link(src, dst): # reverse link is not detected yet. # So schedule the check early because it's very likely it's up self.ports.move_front(dst) self.lldp_event.set() if self.explicit_drop: self._drop_packet(msg)