netdev - Re: sendfile()? Re: SO_LINGER dead: I get an immediate RST on 2.6.24?

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Message-Id: <20090113015614.3b815ad7.billfink@mindspring.com>
Date:	Tue, 13 Jan 2009 01:56:14 -0500
From:	Bill Fink <billfink@...dspring.com>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	ilpo.jarvinen@...sinki.fi, zbr@...emap.net,
	bert.hubert@...herlabs.nl, h.willstrand@...il.com,
	netdev@...r.kernel.org
Subject: Re: sendfile()? Re: SO_LINGER dead: I get an immediate RST on
 2.6.24?

On Tue, 13 Jan 2009, Herbert Xu wrote:

> Bill Fink <billfink@...dspring.com> wrote:
> >
> > If I understand you correctly, to hit this corner case, just after
> > the final TCP write, there would have to be no packets in flight
> > together with a zero TCP window.  To make it more bullet-proof, I
> > guess after seeing a zero tcpi_unacked, an additional small delay
> > should be performed, and then rechecking for a zero tcpi_unacked.
> > I don't see anything else obvious (to me anyway) in the tcp_info
> > that would be particularly helpful in handling this.
> 
> What's wrong with idiag_wqueue? Isn't that a much more direct
> way to get this?

I'm not familiar with idiag_wqueue, but it sounds like it has something
to do with INET_DIAG/INET_TCP_DIAG.  It was a long time ago, but I seem
to recall that using INET_DIAG had a negative impact on performance,
and since the main point of nuttcp is to measure TCP/UDP performance,
that would be contrary to its primary purpose.  Also, I don't want to
rely on something that's not guaranteed to be part of the running kernel.

						-Bill
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