[dpdk-dev] MTU in i40e driver

[Nitin Katiyar]

Hi,

We are using OVS-DPDK (2.6 version) with Fortville NIC (configured in 25G mode) being used as dpdk port. The setup involves 2 VMs running on 2 different computes (destination VM in compute with 10G NIC while originating VM is in compute with Fortville NIC). All the interfaces in the path are configured with MTU of 2140. The VHU port is configured with tag so traffic going out of VM is having vlan id.



While pinging with size of 2112 (IP packet of 2140 bytes) we found that ping response does not reach originating VM (i.e on compute with Fortville NIC). DPDK interface does not show any drop but we don't see any ping response received at DPDK port (verified using port-mirroring). We also don't see any rule in ovs dpctl for ping response. The TX works with this MTU on Fortville but RX is not going through.  If we increase the MTU of DPDK interface by 4 bytes  or reduce the ping size by 4 bytes then it works.



The same configuration works between 10G NICs on both sides.



Is it a known issue with i40 dpdk driver?



Regards,

Nitin