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

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Message-Id: <20200311.231327.132987828940639157.davem@davemloft.net>
Date:   Wed, 11 Mar 2020 23:13:27 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     willemdebruijn.kernel@...il.com
Cc:     netdev@...r.kernel.org, mst@...hat.com, willemb@...gle.com
Subject: Re: [PATCH net] net/packet: tpacket_rcv: do not increment ring
 index on drop

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.