Subject: Re: [PATCH net-next v4] virtio-net: enable NETIF_F_GRO_HW only if GRO-related offloads are supported

From: Jakub Kicinski <[email-masked]>
Date: Thu, 26 Mar 2026 20:03:46 -0700

On Mon, 23 Mar 2026 12:17:30 +0800 Di Zhu wrote:
> Negotiating VIRTIO_NET_F_CTRL_GUEST_OFFLOADS indicates the device
> allows control over offload support, but the offloads that can be
> controlled may have nothing to do with GRO (e.g., if neither GUEST_TSO4
> nor GUEST_TSO6 is supported).
> 
> In such a setup, reporting NETIF_F_GRO_HW as available for the device
> is too optimistic and misleading to the user.
> 
> Improve the situation by masking off NETIF_F_GRO_HW unless the device
> possesses actual GRO-related offload capabilities. Out of an abundance
> of caution, this does not change the current behaviour for hardware with
> just v6 or just v4 GRO: current interfaces do not allow distinguishing
> between v6/v4 GRO, so we can't expose them to userspace precisely.

Michael, Jason, does this patch look good now?

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