netdev - Re: [PATCH] TCP_FAILFAST: a new socket option to timeout/abort a connection quicker

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Date:	Thu, 26 Aug 2010 09:42:36 +0200
From:	Hagen Paul Pfeifer <hagen@...u.net>
To:	Arnd Hannemann <hannemann@...s.rwth-aachen.de>
Cc:	Lars Eggert <lars.eggert@...ia.com>, Jerry Chu <hkchu@...gle.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	<ilpo.jarvinen@...sinki.fi>, <davem@...emloft.net>,
	<netdev@...r.kernel.org>
Subject: Re: [PATCH] TCP_FAILFAST: a new socket option to timeout/abort a connection quicker


On Thu, 26 Aug 2010 09:12:24 +0200, Arnd Hannemann wrote:

>> USER_TIMEOUT is what is locally used for a connection (i.e., takes into
>> account what the remote peer advertised and what we'd like to use),
while
>> ADV_UTO is (only) what we'd like to use and are advertising.
>>
>> (Yes, we initially thought we could make the mechanism simpler, but
then
>> we started to think through all the corner cases...)
>>   
> 
> But from the application point of view it is enough to request a
> specific UTO
> as a socket option, (which will then get announced via ADV_UTO), right?
> Is there any reason, (besides local policy) to not abort the connection
> locally
> after the time the application specified via the above mentioned socket
> option?

The original USER_TIMEOUT (RFC 793) functionality boils down to Jerry's
TCP_FAILFAST patch. This _per see_ has no correlation with the ADV_UTO.
Likely that the ADV_UTO will update the USER_TIMEOUT too. I change my
position from day to day: artificially limit the mechanism and provide a
per see "clever" mechanism and keep both values coherent or provide all
freedom to the user.

Hagen
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