iavf pmd vlan Issue: dpdk-22.11.0

[Amiya Ranjan Mohakud <amiya-ranjan.mohakud@broadcom.com>]

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Hi All,

I'm encountering an issue with XL710 SR-IOV on KVM for VLAN packets
with DPDK-22.11.0 version.

*Issue Description:* I have disabled RTE_ETH_RX_OFFLOAD_VLAN_STRIP in
rte_eth_conf and calling rte_eth_dev_configure and expecting my dpdk
application to receive the packets with vlan tags. Later I added some
vlans using rte_eth_dev_vlan_filter() and I see that the vlan is
getting stripped off  for the incoming packets.

*Setup Details:(KVM SR-IOV)*

KVM Host: Ubuntu 20.04.6 LTS: kernel version: 5.4.0-216-generic #236-Ubuntu
NIC: XL710
3b:00.0 Ethernet controller: Intel Corporation Ethernet Controller
XL710 for 40GbE QSFP+ (rev 02)
3b:00.1 Ethernet controller: Intel Corporation Ethernet Controller
XL710 for 40GbE QSFP+ (rev 02)
i40e PF Driver: Out of tree 2.20.12
Firmware: 9.00/9.40
DPDK Version: 22.11.0


*Observation/Analysis:*

I could see that even after disabling RTE_ETH_RX_OFFLOAD_VLAN_STRIP
offload flag, when I receive the packets, the mbuf offload flags
(RTE_MBUF_F_RX_VLAN | RTE_MBUF_F_RX_VLAN_STRIPPED) are set inside the
mbuf. This confirms that the driver is stripping off the vlans.


I tried with recommended PF driver version for DPDK-22.11.0 as per
https://mails.dpdk.org/archives/dev/2023-November/281700.html and
DPDK-22.11 release note
https://doc.dpdk.org/guides/rel_notes/release_22_11.html. Still it did
not help.


       Intel® Ethernet Converged Network Adapter XL710-QDA2 (2X40G)
    Firmware version(PF): 9.00 0x8000ce86 1.3179.0
    Device id (pf/vf): 8086:1583 / 8086:154c
    Driver version(out-tree): 2.20.12 (i40e)
    Driver version(in-tree): 5.15.0-46-generic (i40e)


Upon debugging further, I came across a DPDK commit:
https://github.com/DPDK/dpdk/commit/e25c7ed114b296ddaa583427824acc30bcf9c85d
which says it sets the vlan_strip on in PF when we set vlan filter on
VF.

I picked the fix, but still it did not help.

Later when I debugged further, I found that the vf_cap_flags is set to
VIRTCHNL_VF_OFFLOAD_VLAN_V2 for the above PF driver and still it sets
the vlan_strip on. I extended the dpdk commit for the
VIRTCHNL_VF_OFFLOAD_VLAN_V2 case which fixed the issue.


I just want to know if it's a known issue for the
VIRTCHNL_VF_OFFLOAD_VLAN_V2 case. I understand it's a known issue for
VIRTCHNL_VF_OFFLOAD_VLAN_V1 and dpdk has a fix for it.
Do we need to add the fix for VIRTCHNL_VF_OFFLOAD_VLAN_V2 as well. Can
we mainstream it? If yes, please let me know so that I can raise a
pull request for it, if required.

Regards
*Amiya*

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