在POX SDN控制器上解决循环问题的方法之一是使用拓扑检测算法,如Floyd-Warshall算法或Bellman-Ford算法。以下是一个使用Floyd-Warshall算法的代码示例:
from pox.core import core
from pox.lib.util import dpid_to_str, str_to_dpid
import pox.openflow.libopenflow_01 as of
log = core.getLogger()
# 记录网络拓扑的邻接矩阵
topology = {}
# 控制器启动时,设置网络拓扑
def _handle_ConnectionUp(event):
dpid = dpid_to_str(event.dpid)
log.debug("Switch %s has come up.", dpid)
topology[dpid] = {}
# 将所有交换机之间的距离初始化为无穷大(inf)
for switch in topology:
topology[switch][switch] = 0
for other_switch in topology:
if switch != other_switch:
topology[switch][other_switch] = float('inf')
# 获取网络中的所有连接,并设置邻接矩阵中的对应距离
for link in core.links:
switch1_dpid = dpid_to_str(link.dpid1)
switch2_dpid = dpid_to_str(link.dpid2)
topology[switch1_dpid][switch2_dpid] = 1
topology[switch2_dpid][switch1_dpid] = 1
# 使用Floyd-Warshall算法计算最短路径
for k in topology:
for i in topology:
for j in topology:
topology[i][j] = min(topology[i][j], topology[i][k] + topology[k][j])
# 控制器接收到Packet-In事件时,检测是否有循环路径
def _handle_PacketIn(event):
packet = event.parsed
if packet.type == packet.LLDP_TYPE:
dpid = dpid_to_str(event.dpid)
src_dpid = packet.src.dpid
dst_dpid = packet.dst.dpid
# 如果源交换机和目标交换机之间的最短路径大于1,则存在循环
if topology[dpid_to_str(src_dpid)][dpid_to_str(dst_dpid)] > 1:
log.warning("Loop detected! Dropping packet from %s to %s", src_dpid, dst_dpid)
return
# 转发Packet-In事件到所有其他交换机
for connection in core.openflow.connections:
if connection.dpid != event.dpid:
connection.send(event.ofp)
def launch():
core.openflow.addListenerByName("ConnectionUp", _handle_ConnectionUp)
core.openflow.addListenerByName("PacketIn", _handle_PacketIn)
上述代码中,_handle_ConnectionUp
函数在控制器启动时被调用,它初始化了邻接矩阵,并计算了最短路径。_handle_PacketIn
函数用于检测Packet-In事件中是否存在循环路径,并丢弃该数据包。在launch
函数中,我们将_handle_ConnectionUp
和_handle_PacketIn
函数与POX事件关联起来。
请注意,这只是解决POX SDN控制器上循环问题的一种方法,你也可以尝试其他算法或方法来解决循环问题。