netdev - Re: [PATCH net] datagram: When peeking datagrams with offset

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Message-ID: <2828157.5Eig1SAfYW@tjmaciei-mobl1>
Date:   Mon, 14 Aug 2017 09:06:35 -0700
From:   Thiago Macieira <thiago.macieira@...el.com>
To:     Willem de Bruijn <willemdebruijn.kernel@...il.com>
CC:     Matthew Dawson <matthew@...systems.ca>,
        Paolo Abeni <pabeni@...hat.com>,
        Network Development <netdev@...r.kernel.org>
Subject: Re: [PATCH net] datagram: When peeking datagrams with offset < 0 don't skip empty skbs

On Monday, 14 August 2017 08:03:50 PDT Willem de Bruijn wrote:
> > I'm actually surprised that only unix sockets can have negative values. 
> > Is
> > there a reason for that?  I had assumed that sk_set_peek_off would allow
> > negative values as the code already has to support negative values due to
> > what the initial value is.
> 
> A negative initial value indicates that PEEK_OFF is disabled. It only
> makes sense to peek from a positive offset from the start of the data.

But here's a question: if the peek offset is equal to the length, should the 
reading return an empty datagram? This would indicate to the caller that there 
was a datagram there, which was skipped over.

That's how we deal with empty datagrams anyway.

-- 
Thiago Macieira - thiago.macieira (AT) intel.com
  Software Architect - Intel Open Source Technology Center