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From Colm MacCárthaigh <colmm...@Redbrick.DCU.IE>
Subject Re: Linux + TCP_CORK + IPv6 = Broken
Date Wed, 04 Dec 2002 09:27:34 GMT
On Tue, Dec 03, 2002 at 11:33:27PM +0100, Jeroen Massar wrote:
> Colm MacCarthaigh [mailto:colm.maccarthaigh@heanet.ie] wrote:
> 
> > On Mon, Dec 02, 2002 at 02:48:53PM -0500, Jeff Trawick wrote:
> > > Colm MacCarthaigh <colm.maccarthaigh@heanet.ie> writes:
> > > 
> > > > Linux (2.4.18 and 2.4.19, for me anyway) with apache versions
> > > > 2.0.40 to 2.0.43 (that I've tested anyways) is broken with
> > > > TCP_CORK and IPv6. Bizarrely v6 requests will work the first
> > > > few times and then start failing, typically you just wont get
> > > > a response from the server. Though strace shows that it did
> > > > try to send one.
> 
> Another 'fun' thing:
>  - Linux 2.4.18
>  - Apache 2.0.43 (preforked)
>  - Debian unstable

My tests were Linux 2.4.18, Apache 2.0.43 (worker), with Debian Stable

> http://www.sixxs.net
>  - IPv4 works
>  - IPv6 doesn't work

ouch

> https://www.sixxs.net
>  - IPv4 works
>  - IPv6 works

O.k., now that is interesting, another thing I've noticed is that when
the encoding is chunked, I can't replicate the problem. Presumably the
problem is related to how much data is trying to be sent down the
socket at once.

> So I have currently installed a default reroute on http://www.sixxs.net
> for IPv6 requests
> to redirect them to the https:// variant. Try
> http://www.ipv6.sixxs.net/news/ for example
> to not get redirected (only a IPv6 non-ssl / request redirs).
> btw www.ipv4.sixxs.net has only A, www.ipv6.sixxs.net has only AAAA.
> 
> The "IPv6 doesn't work" actually means: request comes in, answer comes
> out partially.
> A first request gets returned correctly any pipelined request coming in
> next fail.
> That's why the / works (as it's only 1 answer, not pipelined) some other
> pages without
> pictures show this too.
> 
> Odd that IPv4 and SSL'd IPv4/IPv6 do work.

makes sense if it's related the size of the writes

> Another thing is that I do got it working on other boxes with 2.4.18 :)
> Same build of apache on those, other NIC's though:
> 2.4.18 - purgatory.unfix.org (HTTP and HTTPS IPv4 and IPv6 ofcourse)
> 2.4.19-pre5-ac3 - games.concepts.nl (HTTP IPv4 and IPv6)

They're outputting chunked encoding, which is why I think they work.

> Oddness all around, but maybe that problem is related?

Definitely, one slight difference though, when I'm testing
the first time I connect I can make any number of requests
safely. Ie. the entire socket seems clean. The second
one I create just won't give me responses from the server.

-- 
colmmacc@redbrick.dcu.ie        PubKey: colmmacc+pgp@redbrick.dcu.ie  
Web:                                 http://devnull.redbrick.dcu.ie/ 

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