在l3_learning.py中,类l3_switch中有一个名为_handle_PacketIn的方法.
现在,我了解到此事件是交换机在接收到与表中没有任何条目相对应的数据包时联系控制器的事件.

我不明白的是

packet = event.parsed

现在,packet.next在isinstance(packet.next,ipv4)中意味着什么？

def _handle_PacketIn (self, event):
    dpid = event.connection.dpid
    inport = event.port
    packet = event.parsed
    if not packet.parsed:
      log.warning("%i %i ignoring unparsed packet", dpid, inport)
      return

    if dpid not in self.arpTable:
      # New switch -- create an empty table
      self.arpTable[dpid] = {}
      for fake in self.fakeways:
        self.arpTable[dpid][IPAddr(fake)] = Entry(of.OFPP_NONE,
         dpid_to_mac(dpid))

    if packet.type == ethernet.LLDP_TYPE:
      # Ignore LLDP packets
      return

    if isinstance(packet.next, ipv4):
      log.debug("%i %i IP %s => %s", dpid,inport,
                packet.next.srcip,packet.next.dstip)

      # Send any waiting packets...
      self._send_lost_buffers(dpid, packet.next.srcip, packet.src, inport)

      # Learn or update port/MAC info
      if packet.next.srcip in self.arpTable[dpid]:
        if self.arpTable[dpid][packet.next.srcip] != (inport, packet.src):
          log.info("%i %i RE-learned %s", dpid,inport,packet.next.srcip)
      else:
        log.debug("%i %i learned %s", dpid,inport,str(packet.next.srcip))
      self.arpTable[dpid][packet.next.srcip] = Entry(inport, packet.src)

      # Try to forward
      dstaddr = packet.next.dstip
      if dstaddr in self.arpTable[dpid]:
        # We have info about what port to send it out on...

        prt = self.arpTable[dpid][dstaddr].port
        mac = self.arpTable[dpid][dstaddr].mac

解决方法:

我想我已经知道了.

数据包是数据链路层发送到物理层的整个数据包. packet.next删除数据链路层的封装,并显示IP数据包(由IP层发送到数据链路层的数据包).因此,要获取源MAC地址,我们使用packet.src,并获取源IP地址,我们使用packet.next.srcip