netdev - Re: A misbehavior of handling TCP out of band data ?

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Date:	Thu, 3 Mar 2011 14:23:57 -0500
From:	John Heffner <johnwheffner@...il.com>
To:	Li Yu <raise.sail@...il.com>
Cc:	netdev <netdev@...r.kernel.org>
Subject: Re: A misbehavior of handling TCP out of band data ?

This feature is only here to support legacy applications, and really
should not be used.  See RFC 6093.  http://tools.ietf.org/html/rfc6093

  -John


On Thu, Mar 3, 2011 at 10:24 AM, Li Yu <raise.sail@...il.com> wrote:
> Hi,
>
>        In my words, if we did not turn on SO_OOBINLINE at receiver,
> any OOB bytes do not have to be read from regular TCP byte stream.
>
>        But in below extreme case: the sender process have a loop to
> send 1 OOB byte 'O' and 1 byte normal data 'D', the receiver ignore
> all OOB data, so if OOB feature works well, the receiver should
> receive 'D' only, However, in fact, the receiver still can see OOB
> bytes by recv() syscall without MSG_OOB flag.
>
>        I found that we may send "ODODODODODOD...." in a tcp segment,
> and tcp_sendmsg() has no special code to avoid this.
>
>        Well, I know that it seem that above case is too extreme to
> use in actual environment, but above is simplified from our actual
> scenario.
>
>        Anyway, I think that overwriting or skip previous OOB bytes is
> acceptable, but leave them in regular TCP byte stream likely is a bug.
> En, probably, the disabled SO_OOBINLINE just is a feature of receiver
> side, sender do not need to have to guarantee it?
>
>        Thanks.
>
> Yu
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