netdev - Re: TCP: orphans broken by RFC 2525 #2.17

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Message-ID: <20100926232530.GK12373@1wt.eu>
Date:	Mon, 27 Sep 2010 01:25:30 +0200
From:	Willy Tarreau <w@....eu>
To:	David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org
Subject: Re: TCP: orphans broken by RFC 2525 #2.17

On Sun, Sep 26, 2010 at 04:08:38PM -0700, David Miller wrote:
> From: Willy Tarreau <w@....eu>
> Date: Mon, 27 Sep 2010 00:54:40 +0200
> 
> > On Sun, Sep 26, 2010 at 03:38:32PM -0700, David Miller wrote:
> >> From: Willy Tarreau <w@....eu>
> >> Date: Mon, 27 Sep 2010 00:34:48 +0200
> >> 
> >> > I don't see what is being violated nor what reliability has been
> >> > compromised.
> >> 
> >> The TCP protcol's obligation to reliably deliver data between
> >> two applications, that is what has been violated.
> > 
> > Once again, I don't see why, due to the orphans mechanism. Please
> > consider for a minute that the application-level close() is distinct
> > from the protocol-level close. The application-level close() just
> > instructs the lower layer to turn the connection into an orphan.
> 
> A close() is equivalent to a shutdown() with both the send and
> receive masks set.
> 
> You are telling TCP that you expect no more data to be received.

Agreed. But that's not a reason for killing outgoing data that is
being sent when there are some data left in the rcv buffer.

Honnestly David, after some thinking, could you still find a valid use
of the orphans as they are now ? I personally fail to do so. And what
drove me to the kernel on this issue is that I found the behaviour
inconsistent with the principle of the orphan itself.

Willy

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