netdev - Re: [PATCH net] net/packet: tpacket_rcv: do not increment ring index on drop

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Message-ID: <20200312022748-mutt-send-email-mst@kernel.org>
Date:   Thu, 12 Mar 2020 02:27:58 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     David Miller <davem@...emloft.net>
Cc:     willemdebruijn.kernel@...il.com, netdev@...r.kernel.org,
        willemb@...gle.com
Subject: Re: [PATCH net] net/packet: tpacket_rcv: do not increment ring index
 on drop

On Wed, Mar 11, 2020 at 11:13:27PM -0700, David Miller wrote:
> From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
> Date: Mon,  9 Mar 2020 11:34:35 -0400
> 
> > From: Willem de Bruijn <willemb@...gle.com>
> > 
> > In one error case, tpacket_rcv drops packets after incrementing the
> > ring producer index.
> > 
> > If this happens, it does not update tp_status to TP_STATUS_USER and
> > thus the reader is stalled for an iteration of the ring, causing out
> > of order arrival.
> > 
> > The only such error path is when virtio_net_hdr_from_skb fails due
> > to encountering an unknown GSO type.
> > 
> > Signed-off-by: Willem de Bruijn <willemb@...gle.com>
> 
> I'm applying this, as it fixes the ring state management in this case.
> 
> The question of what we should actually be doing for unknown GSO types
> is a separate discussion.
> 
> Thanks Willem.

Absolutely, I agree

Acked-by: Michael S. Tsirkin <mst@...hat.com>