linux-kernel - Re: [PATCH net v3] vmxnet3: correctly report gso type for UDP tunnels

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Message-ID: <9faa4d04-e370-42f9-81e1-0759ca236000@redhat.com>
Date: Fri, 30 May 2025 08:48:47 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Ronak Doshi <ronak.doshi@...adcom.com>, netdev@...r.kernel.org
Cc: Guolin Yang <guolin.yang@...adcom.com>,
 Broadcom internal kernel review list
 <bcm-kernel-feedback-list@...adcom.com>, Andrew Lunn
 <andrew+netdev@...n.ch>, "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net v3] vmxnet3: correctly report gso type for UDP tunnels

On 5/30/25 2:46 AM, Ronak Doshi wrote:
> Commit 3d010c8031e3 ("udp: do not accept non-tunnel GSO skbs landing
> in a tunnel") added checks in linux stack to not accept non-tunnel
> GRO packets landing in a tunnel. This exposed an issue in vmxnet3
> which was not correctly reporting GRO packets for tunnel packets.
> 
> This patch fixes this issue by setting correct GSO type for the
> tunnel packets.
> 
> Currently, vmxnet3 does not support reporting inner fields for LRO
> tunnel packets. This is fine for now as workaround is to enable
> tnl-segmentation offload on the relevant interfaces. This problem
> pre-exists this patch fix and can be addressed as a separate future
> patch.

I think it would be better if you rephrase the above paragraph, as is a
bit misleading. The workaround is available only in some scenarios: when
the egress device supports tunnel TSO and only if the relevant egress
driver does not use the skb inner fields (many NICs actually use/need them).

Note that there is no guarantee that the egress device will be vmxnet, too.

/P