Re: [dpdk-dev] l2fwd application are not sending continuous packets .

[Stephen Hemminger <stephen@networkplumber.org>]

On Thu, 9 Jan 2020 07:25:45 +0530
satyavalli rama <satyavalli.rama@gmail.com> wrote:

> Can anyone please help us with this?
> 
> 
> On Mon, Jan 6, 2020, 11:25 satyavalli rama <satyavalli.rama@gmail.com>
> wrote:
> 
> >
> >
> >
> > 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
> >  

Sorry, you need to dig inside the forwarding application and instrument
what is coming in and how packets are being processed. You usually can't
treat DPDK as a black box.