ns3 openflow model cannot config permanent table rules?!

[qingyuShi]

I made the test below:

node1------------switch--------------switch--------node4

                        |                       |

                        |                       |

                     node2               node3

I sent 2 same packet from node2 to node1,the LearningController attached in the both switches,like this"echoClient.SetAttribute ("MaxPackets", UintegerValue (2));"

I added some print message in the LearningController mode,like below:

if (!dst_addr.IsBroadcast ())

        {

          LearnState_t::iterator st = m_learnState.find (dst_addr);

          if (st != m_learnState.end ())

            {

              out_port = st->second.port;

              //NS_LOG_ERROR("switchindex:  "<<swtch->GetNode()->GetId()<<"  inport:  "<<in_port<<" nw_src: "<<key.flow.nw_src);

              //NS_LOG_ERROR("switchindex:  "<<swtch->GetNode()->GetId()<<"  outport:  "<<out_port<<" nw_dst: "<<key.flow.nw_dst);

              NS_LOG_ERROR("switchindex:  "<<swtch->GetNode()->GetId()<<"  inport:  "<<in_port<<" dl_src: "<<src_addr);

              NS_LOG_ERROR("switchindex:  "<<swtch->GetNode()->GetId()<<"  outport:  "<<out_port<<" dl_dst: "<<dst_addr);

              NS_LOG_ERROR("config switch "<<swtch->GetNode()->GetId()<<";buffer id "<<opi->buffer_id);

            }

I think ,when the node1 and node2 communicate,and the packet is the same ,the same table rule should be added only once.

However,the print message is below:

switchindex:  4  inport:  1 dl_src: 00:00:00:00:00:03

switchindex:  4  outport:  2 dl_dst: 00:00:00:00:00:05

config switch 4;buffer id 50397184

switchindex:  4  inport:  2 dl_src: 00:00:00:00:00:05

switchindex:  4  outport:  1 dl_dst: 00:00:00:00:00:03

config switch 4;buffer id 67174400

switchindex:  4  inport:  2 dl_src: 00:00:00:00:00:05

switchindex:  4  outport:  1 dl_dst: 00:00:00:00:00:03

config switch 4;buffer id 117506048

switchindex:  4  inport:  1 dl_src: 00:00:00:00:00:03

switchindex:  4  outport:  2 dl_dst: 00:00:00:00:00:05

config switch 4;buffer id 134283264

You can see, the communicate pattern is "node2->node1","node1->node2","node2->node1","node1->node2".The IP and Ports information are not printed,but they are the same in the two communication.

May you help me .

Sorry for my poor English:)