netdev - Re: virtio_net: can change MTU after installing program

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Message-ID: <20200227114513.277400fb@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Thu, 27 Feb 2020 11:45:13 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Michael Chan <michael.chan@...adcom.com>
Cc:     "Michael S. Tsirkin" <mst@...hat.com>,
        David Ahern <dahern@...italocean.com>,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Andy Gospodarek <andy@...yhouse.net>
Subject: Re: virtio_net: can change MTU after installing program

On Thu, 27 Feb 2020 11:26:58 -0800 Michael Chan wrote:
> On Wed, Feb 26, 2020 at 5:37 PM Jakub Kicinski <kuba@...nel.org> wrote:
> > I had a look at Broadcom and it seems to be missing there as well :(
> > Qlogic also. Ugh.  
> 
> The Broadcom bnxt_en driver should not allow the MTU to be changed to
> an invalid value after an XDP program is attached.  We set the
> netdev->max_mtu to a smaller value and dev_validate_mtu() should
> reject MTUs that are not supported in XDP mode.

I see, thanks!