From: Gilad Ben-Yossef <gilad@codefidence.com>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: "Ilpo Järvinen" <ilpo.jarvinen@helsinki.fi>,
Netdev <netdev@vger.kernel.org>,
"Ori Finkalman" <ori@comsleep.com>
Subject: Re: [PATCH] [RFC] IPv4 TCP fails to send window scale option when window scale is zero
Date: Thu, 01 Oct 2009 11:39:43 +0200 [thread overview]
Message-ID: <4AC478DF.2060401@codefidence.com> (raw)
In-Reply-To: <4AC357D3.7080606@gmail.com>
Eric Dumazet wrote:
>
>>>
>>> Your version slows down the tcp_options_write() function, once per tx packet.
>>>
>> Are you serious that anding would cost that much? :-/
>>
>
> Not really :)
>
LOL I was trying very hard to understand why you thought this was such
an issue. My head was flying into all sorts of weird directions like
cache effects and the like... ;-)
<snip>
> Yes, wscale 0 is RFC valid, but are we sure some equipment wont play funny games
> with such value ? At least sending "wscale 1-14" must be working...
>
Well, there at least used to be routers that would actually zeroed the
WS value in transit while leaving the option set, but this is another
issue of course.
Anyway, I know Vista at least does set the window scale TCP option by
default. One assumes they occasionally send a zero value scale. Not that
Vista is such a good benchmark to compare Linux to but at least I tend
to believe the issue would have popped up if it is common enough.
I can craft a patch to introduce a route table option to set TCP window
scale minimum and maximum sizes, similar to window size route option, if
you there is a need for that. Personally, I think it is just overkill.
>
> My quick&dirty patch was only for discussion, I have no strong opinion on it,
> only that was on one place to patch instead of two/three/four I dont know yet.
>
> So please Gilad & Ori send us a new patch :)
>
>
Revised patch follows in next email.
Gilad
--
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prev parent reply other threads:[~2009-10-01 9:39 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-09-29 15:05 [PATCH] [RFC] IPv4 TCP fails to send window scale option when window scale is zero Gilad Ben-Yossef
2009-09-29 17:19 ` Eric Dumazet
2009-09-30 6:28 ` Gilad Ben-Yossef
2009-09-30 7:16 ` Eric Dumazet
2009-09-30 11:42 ` Ilpo Järvinen
2009-09-30 13:06 ` Eric Dumazet
2009-10-01 9:39 ` Gilad Ben-Yossef [this message]
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