Re: [PATCH net-next] net/mlx5: Add MLX5_VXLAN config option

[Gal Pressman]

Hi Marc,

On 05/05/2026 4:10, Jakub Kicinski wrote:
> On Mon, 4 May 2026 15:44:26 -0700 Marc Harvey wrote:
>>> Are you aware of NETIF_F_RX_UDP_TUNNEL_PORT ?
>>> I haven't checked it does exactly what we need, but I recall there was
>>> a ethtool feature for this..  
>>
>> Thanks, I didn't know about that feature and mlx5 uses it. However,
>> mlx5 unconditionally sets the `UDP_TUNNEL_NIC_INFO_STATIC_IANA_VXLAN`
>> flag, which excludes port 4789 from the entire UDP tunnel core offload
>> management (see `__udp_tunnel_nic_add_port()`).
>>
>> So using ethtool to disable `NETIF_F_RX_UDP_TUNNEL_PORT` will not
>> disable vxlan offload for port 4789.
>>
>> I think a better approach would be to just remove this static
>> automatic offloading for port 4789, mlx5 is the only driver using
>> `UDP_TUNNEL_NIC_INFO_STATIC_IANA_VXLAN` anyway. However, there might
>> be a reason for this, such as some supported hardware offloading vxlan
>> on port 4789 by default even without commands from the driver.
>>
>> If mlx5 continues to use the `UDP_TUNNEL_NIC_INFO_STATIC_IANA_VXLAN`
>> flag, then some change is required to fully disable vxlan offloading.
> 
> Sorry, I don't know mlx5 very well. Sounds like you have to talk 
> to nVidia or/and run some experiments. The current patch is a no-go.
> 

The hardware offloads 4789 by default, hence the
UDP_TUNNEL_NIC_INFO_STATIC_IANA_VXLAN, you cannot simply remove it.

Have you tried disabling tx-udp_tnl-segmentation through ethtool?