netdev - Re: [Xen-devel] xennet_start

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Message-ID: <20170119111426.GA22018@oracle.com>
Date:   Thu, 19 Jan 2017 06:14:26 -0500
From:   Sowmini Varadhan <sowmini.varadhan@...cle.com>
To:     Paul Durrant <Paul.Durrant@...rix.com>
Cc:     Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Wei Liu <wei.liu2@...rix.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>
Subject: Re: [Xen-devel] xennet_start_xmit assumptions

On (01/19/17 09:36), Paul Durrant wrote:
> 
> Hi Sowmini,
> 
>   Sounds like a straightforward bug to me... netfront should be able
> to handle an empty skb and clearly, if it's relying on skb_headlen()
> being non-zero, that's not the case.
> 
>   Paul

I see. Seems like there are 2 things broken here: recovering
from skb->len = 0, and recovering from  the more complex
case of (skb->len > 0 && skb_headlen(skb) == 0)

Do you folks want to take a shot at fixing this,
since you know the code better? If you are interested,
I can share my test program to help you reproduce the 
simpler skb->len == 0 case, but it's the fully non-linear
skbs that may be more interesting to reproduce/fix. 

I'll probably work on fixing packet_snd to return -EINVAL 
or similar when the len is zero this week.

--Sowmini