netdev - Re: [PATCH v7 net-next 01/16] gso: Remove arbitrary checks for unsupported GSO

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Message-ID: <20160522074407.GA12660@redhat.com>
Date:	Sun, 22 May 2016 10:44:07 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Hannes Frederic Sowa <hannes@...essinduktion.org>
Cc:	Tom Herbert <tom@...bertland.com>, davem@...emloft.net,
	netdev@...r.kernel.org, kernel-team@...com
Subject: Re: [PATCH v7 net-next 01/16] gso: Remove arbitrary checks for
 unsupported GSO

On Sat, May 21, 2016 at 03:02:30AM +0200, Hannes Frederic Sowa wrote:
> Hello,
> 
> On 18.05.2016 18:06, Tom Herbert wrote:
> > In several gso_segment functions there are checks of gso_type against
> > a seemingly arbitrary list of SKB_GSO_* flags. This seems like an
> > attempt to identify unsupported GSO types, but since the stack is
> > the one that set these GSO types in the first place this seems
> > unnecessary to do. If a combination isn't valid in the first
> > place that stack should not allow setting it.
> > 
> > This is a code simplication especially for add new GSO types.
> 
> I couldn't still wrap my head around this.
> 
> I wonder if this is safe in case of if the packet is generated from an
> untrusted virtual machine over virtio_net?
> 
> Bye,
> Hannes

I'm not sure how you use virtio_net, but neither it nor tun or macvtap
commonly used as backends for it pass gso flags through
from untrusted entities.

-- 
MST