[dpdk-stable] l2fwd application are not sending continuous packets .

[dpdk-stable] l2fwd application are not sending continuous packets .

[satyavalli rama]

Hello Dpdk Team,

I'm facing issue while forwarding packets in DPDK's l2fwd application.
While sending 1 Lac packets from Scapy, I could see sometimes packets are
sending from one VM to another VM.
Before explaining issue let me explain topology.



*Topology :-=======*1) I am having 4 VMs(Virtual Machines) in same host.
All these VM are running on Ubuntu 16.04.1.
2) VM-1 is used as Scapy to forward packets (Scapy version 2.4.3) . While
creating packets I am giving destination mac(d-mac) address of VM-1.
3) In VM-2 am running L2 forwarding application.
    In this l2fwd application, I am doing simple packet forwarding by
statically keeping mac address of VM-3.
Code :-
     l2fwd_mac_updating () {
   ...
   ......
   .......
      *((uint64_t *)tmp) = 0xddccbbaa/*VM-3 mac address*/ +
((uint64_t)dest_portid << 40);
     }
4) Also in VM-3, I am doing same like VM-2, but I kept mac address of VM-4
5) In VM-4, I am using wireshark to see packets coming from VM-3.
6) In VM-2 and VM-3, I kept promiscuous mode off by commenting out
rte_eth_promiscuous_enable().

   ---------------                                   ---------------------
                         ------------------
------------------------
   |    VM-1  |      ---------->                |       VM-2     |
---------------->   |     VM-3    |       ------------------> |        VM-4
     |
   ---------------                                   ---------------------
                         ------------------
------------------------
        Scapy                              Simple L2 forwarding
      Simple L2 forwarding                        Wireshark
used for sending packets            Sending all packets to
 Sending all packets to
                                                            VM-3
                        VM-4
                                                          (DPDK)
                     (DPDK)


*Problem :- ======*==
From scapy VM, I am sending 1 lac packets with rate of 100 packets per
second. *During problematic condition I could see packets are not getting
forward from VM-3.**Problematic state is happening anytime after sending 1k
packets.*
This issue is not consistence but I could see this issue 8 out of 10 times.


* Debugging and Observations :-=========================*
When I tried to debug this issue , I could see that
1) In problematic state, rx queue of VM-3 is not getting packets, but VM-2
is sending packets properly. I checked this by using pdump of rx queue.
2) Just before problematic state in VM-3, I could see that  previous
packet(only one packet) instead of going to VM-4, it is coming back to
again in rx queue of VM-3 and after wards I did not get any packets in rx
queue.
3) I have changed rate of packet forward 10packets per second. but still
see the issue.


*Can anyone please help to solve this problem ? I need it urgently .*
Thanks,
Satya