netdev - Re: [RFC] net: remove NETIF_F_GSO_FRAGLIST from NETIF_F_GSO

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Message-ID: <2bb2f7ae-1175-4fff-ae4e-25c624295345@nbd.name>
Date: Fri, 16 Aug 2024 17:29:21 +0200
From: Felix Fietkau <nbd@....name>
To: Willem de Bruijn <willemdebruijn.kernel@...il.com>, netdev@...r.kernel.org
Subject: Re: [RFC] net: remove NETIF_F_GSO_FRAGLIST from NETIF_F_GSO_SOFTWARE

On 16.08.24 16:13, Willem de Bruijn wrote:
> Felix Fietkau wrote:
>> Several drivers set NETIF_F_GSO_SOFTWARE, but mangle fraglist GRO packets
>> in a way that they can't be properly segmented anymore.
> 
> Can you share a bit more concrete detail: which driver, for instance, and
> how does it mangle the packet?
> 
> I assume something with inserting or deleting tunnel headers. But the
> fraglist skbs should be able to reproduce the modified header in
> skb_segment_list?

I've received bug reports from a variety of people, often with very 
little context, usually crashing while segmenting fraglist skbs.

The ones that people were able to easily reproduce involved bridging 
with vxlan or virtio net devices. People using those two reported that 
my patch fixed their crashes.

I will try to gather more information about the root cause of the crashes.

- Felix