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List:       dpdk-users
Subject:    Re: [dpdk-users] UDP packet transmission issue - DPDK 18.08
From:       "Wiles, Keith" <keith.wiles () intel ! com>
Date:       2019-05-08 15:03:25
Message-ID: F46A4E2E-B0B9-4886-944F-4F55800A31F4 () intel ! com
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Hi Hirok,

> On May 8, 2019, at 9:28 AM, hirok borah <hirok.gen@gmail.com> wrote:
> 
> Thanks Keith for sharing the info.
> 
> But as also stated by Anupama, the problem here is with KNI. 
> 
> When UDP packet of certain length, say 730, is written to kni, it is getting \
> dropped. 
> Whereas UDP of length say 60, does not have any issues, it goes to kernel.
> 
> And this issue was not seen with previous versions, only seen when we upgraded to \
> v18.08

I have not used KNI per say, but it also does not seem to understand UDP or TCP or \
any another protocol sent only mbufs. Unless I am wrong that means the application \
must construct the UDP frame to be sent to the kernel and setup the mbuf headers \
correctly, right? Even the KNI test code does not seem to understand UDP frames, just \
looking at the code anyway.

Using testpmd or traffic generators to send a UDP frame to KNI interface and see if \
the problem still exists does seem like a reasonable direction to eliminate possible \
problems.

Beyond that I can not help, take my suggestions as you see fit.
Thanks
> 
> Regards
> -Hirok
> 
> 
> On Wed, May 8, 2019, 7:28 PM Wiles, Keith <keith.wiles@intel.com> wrote:
> 
> 
> > On May 8, 2019, at 1:41 AM, hirok borah <hirok.gen@gmail.com> wrote:
> > 
> > Hi All,
> > 
> > Do we have any resolution for this issue yet ?
> > This looks like a defect in DPDK 18.08.
> 
> DPDK does not understand UDP/TCP or any L4 Packet per say, it only sends the \
> packets constructed in the application. It will send the packets as defined and the \
> only place DPDK tries to determine the packet type is when it receives the packet \
> which in this case is the kernel. 
> I do not use testpmd much, but use pktgen-dpdk for my work. Please try with testpmd \
> or pktgen or TRex or moongen and see if the problem still exists.
> > 
> > Plz share if anyone have any inputs on this issue.
> > 
> > Regards
> > Hirok
> > 
> > On Sat, Apr 20, 2019 at 9:41 AM Anupama Laxmi <anupamalaxmi4@gmail.com>
> > wrote:
> > 
> > > We have recently upgraded to DPDK 18.08 version. After upgrading to the
> > > latest version observing issue with UDP packets transmission errors for few
> > > packets ( UDP size 736 bytes) .With older version of DPDK  we never faced
> > > this issue.
> > > 
> > > Attaching the filtered tcpdump which shows "Bad UDP length > IP payload
> > > length" for one such packet.
> > > 
> > > No issue observed while transferring UDP packets with size 28 bytes and 48
> > > bytes. I tried to print the packet length calculation in my program just
> > > before sending it out to the Kernel using rte_kni_tx_burst. The packet
> > > length calculation seems correct to me.
> > > 
> > > 1.)
> > > size_udp:48
> > > sizeof(struct udp_hdr):8
> > > size_ApplMsg:40
> > > udphdr->dgram_len:12288
> > > m->data_len:82
> > > size_ip:68
> > > l2_data_shift:14
> > > 
> > > 2.)
> > > size_udp:28
> > > sizeof(struct udp_hdr):8
> > > size_ApplMsg:20
> > > udphdr->dgram_len:7168
> > > m->data_len:62
> > > ip->total_length:12288
> > > size_ip:48
> > > l2_data_shift:14
> > > 
> > > *** Packets with UDP size 736 are not getting transmitted to the
> > > receiving end and getting dropped.
> > > 
> > > 3.)
> > > size_udp:736
> > > sizeof(struct udp_hdr):8
> > > size_ApplMsg:728
> > > udphdr->dgram_len:57346
> > > m->data_len:770
> > > size_ip:756
> > > l2_data_shift:14
> > > 
> > > Also MTU is set to 1500 in my program. So it shouldn't be an issue to
> > > transfer 736 bytes UDP data which is less than 1500 bytes MTU.
> > > 
> > > Looks like the kernel is dropping this packet.
> > > 
> > > So I tried to increase the kernel buffer size but that didn't help.
> > > 
> > > netstat -su -> output shows 0 send/receive buffer errors.
> > > 
> > > 
> > > What has changed in DPDK 18.08 with respect to UDP packets? Please suggest
> > > if I need to consider tuning udp ( using new API ) , offloading udp
> > > traffic(new offload flags)  to resolve this issue.
> > > 
> > > Thanks,
> > > -------------- next part --------------
> > > A non-text attachment was scrubbed...
> > > Name: bad_udp_length.png
> > > Type: image/png
> > > Size: 56015 bytes
> > > Desc: not available
> > > URL: <
> > > http://mails.dpdk.org/archives/users/attachments/20190420/f5dd6779/attachment.png
> > > 
> > > > 
> > > 
> > 
> > 
> > -- 
> > Regards,
> > -Hirok
> 
> Regards,
> Keith
> 

Regards,
Keith


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