Connectx-6 LX support for S-tagged VLAN traffic?

Infrastructure & Networking Adapters and Cables Ethernet Adapter Cards
1

Hello all!

I’m reaching out as I can’t find a definitive answer for whether ConnectX-6 LX Mellanox cards (specifically MCX631102AN-ADAT) can support S-VLAN tagged traffic. I have seen the following dmesg logged on one of our servers:
mlx5e_fs_set_rx_mode_work:852:(pid ): S-tagged traffic will be dropped while C-tag vlan stripping is enabled

And when looking at the output of ethtool -k mellanox_interface I see the following setting
rx-vlan-stag-filter: on [fixed]

This to me seems to indicate the card is Filtering out S-tagged traffic as a feature, but none of the documentation I’ve read seems to reference S-tag or C-tag VLAN support one way or another. Would I be able to get any confirmation regarding this capability of the cards? If this is something that can be changed, can I be pointed to documentation on how to change this setting?

EDIT: Adding on that when we have VLAN tagged traffic coming from upstream we see that a good % of the traffic is marked as dropped by the kernel. However, once we stripped the VLANs, we no longer see these issues, leading us to believe that some of the S-VLAN tags are being dropped.

2

Hi Collin,

This warning means that S-VLAN tagged packets will be dropped if C-VLAN stripping is enabled.

If your environment does not require S-VLAN, you can ignore this warning.
If you need to pass S-VLAN traffic, you can disable VLAN stripping using ethtool:

ethtool -K ens11f1np1 rx-vlan-offload off

Regards,
Chen

3

Hi Chen,

Thank you for the explanation. In our environment we have that setting disabled already, so that’s at least a good relief to hear.

Would you know if this would have any relationship to the kernel incrementing on RX-DRP? We noticed when we removed VLANs from our feeds, the servers would stop reporting drops on the RX-DRP counter. We don’t know of the exact cause for the increment, but it definitely is somehow tied to VLAN tagging. We thought it could have been that S-tagged traffic was getting dropped as a result, but our applications were able to parse S-tagged traffic, even with the report of drops. So, we’re left scratching our heads on the cause