[dpdk-users] UDP packet transmission issue - DPDK 18.08

hirok borah hirok.gen at gmail.com
Wed May 8 08:41:49 CEST 2019


Hi All,

Do we have any resolution for this issue yet ?
This looks like a defect in DPDK 18.08.

Plz share if anyone have any inputs on this issue.

Regards
Hirok

On Sat, Apr 20, 2019 at 9:41 AM Anupama Laxmi <anupamalaxmi4 at 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,
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-- 
Regards,
-Hirok


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