In a CC13/Contrail 5.0.1 setup with Intel X710 Fortville NICs, most DPDK vrouters drop with default 1500 MTU and above. It can be seen that the interface drop counter increases on the trnasmitting side.
Possibly related to
CC13: DPDK vrouter fragments packets >= 1500 from non-DPDK workloads
https://bugs.launchpad.net/juniperopenstack/+bug/1795834
Tests:
- Test setup: 2 DPDK packet gen images on 2 different DPDK compute nodes (overcloud63m-compdpdk-22 to overcloud63m-compdpdk-25)
- DPDK packetgen traffic with packet < 1400 works in both directions without issues
- DPDK packetgen traffic with packets 1511 works only in one direction (from overcloud63m-compdpdk-22 to overcloud63m-compdpdk-25) but not the other. If overcloud63m-compdpdk-25 tries to send large packets, nothing goes out on vif 0 and I see the interface drop counter go up
- Non-DPDK traffic (exiting packetgen and using ping) for small packets works in both direction
- Non-DPDK traffic for large packets gets fragmented (despite 9000 configured on vhost0) and only works in the same direction as the DPDK traffic (from overcloud63m-compdpdk-22 to overcloud63m-compdpdk-25) --> this is covered in https://bugs.launchpad.net/juniperopenstack/+bug/1795834
- Note: kernel mode vrouters work fine with all packet sizes, also from working DPDK node 22 to kernel mode all works.
test logs attached.
Kiran is working on the fix.