Date: Mon, 22 Jan 2007 09:15:13 +0100 From: Uwe Doering <gemini@geminix.org> To: Steve Watt <steve@Watt.COM> Cc: hackers@freebsd.org, andre@freebsd.org, julian@elischer.org Subject: Re: Interesting TCP issue Message-ID: <45B47291.1000102@geminix.org> In-Reply-To: <200701200918.l0K9Igbn002427@wattres.watt.com> References: <200701020825.l028PMBK034571@wattres.watt.com> <200701200918.l0K9Igbn002427@wattres.watt.com>
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Steve Watt wrote:
> In <459AD141.5010502@elischer.org>, Julian Elischer wrote:
>
> [ Snip discussion of symptoms of window scaling broken when
> talking to at least the skype mail servers. ]
>
>> we have seen this since 4.x
>> I think a fix may be in 7.0 but I'm not sure..
>> I thin kthere is a problem when the far end sets the window down to 1
>> but scales it by a factor of 2^{big number}.
>>
>> Andre, can you check out this problem and MFC the correct fix
>> if it is indeed the same problem in 6.2?
>
> It is the same problem; I took the (one-line) fix as indicated by
>
>> http://cvs.ironport.com/cgi-bin/viewcvs.cgi/freebsd/src/sys/netinet/tcp_syncache.c.diff?r1=1.84&r2=1.85
>
> (well, not cvs.ironport.com, which doesn't seem to exist at the moment),
> and applied the diff from 1.84 to
> 1.85 and to a 6.2-PRERELEASE box updated around 25 Dec 06.
> It works like a charm.
>
> I would vote to MFC 1.85 now that 6.2 is out.
>
> The diff, for those who are following along at home, is:
>
> ===================================================================
> RCS file: /usr/local/www/cvsroot/FreeBSD/src/sys/netinet/tcp_syncache.c,v
> retrieving revision 1.84
> retrieving revision 1.85
> diff -u -p -r1.84 -r1.85
> --- src/sys/netinet/tcp_syncache.c 2006/02/09 21:29:02 1.84
> +++ src/sys/netinet/tcp_syncache.c 2006/02/28 23:05:59 1.85
> @@ -682,7 +682,7 @@ syncache_socket(sc, lso, m)
> tp->t_flags |= TF_NOOPT;
> if (sc->sc_flags & SCF_WINSCALE) {
> tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE;
> - tp->requested_s_scale = sc->sc_requested_s_scale;
> + tp->snd_scale = sc->sc_requested_s_scale;
> tp->request_r_scale = sc->sc_request_r_scale;
> }
> if (sc->sc_flags & SCF_TIMESTAMP) {
I wonder whether it is that easy. As far as I can tell the commit to
HEAD actually comprised changes to three files:
http://www.freebsd.org/cgi/cvsweb.cgi/src/sys/netinet/tcp_input.c.diff?r1=1.290&r2=1.291
http://www.freebsd.org/cgi/cvsweb.cgi/src/sys/netinet/tcp_syncache.c.diff?r1=1.84&r2=1.85
http://www.freebsd.org/cgi/cvsweb.cgi/src/sys/netinet/tcp_var.h.diff?r1=1.127&r2=1.128
How about the modifications in 'tcp_input.c'? Are they relevant to the
problem this thread is about? If so, assessing the correctness of an
MFC might prove to be a little harder.
Uwe
--
Uwe Doering | EscapeBox - Managed On-Demand UNIX Servers
gemini@geminix.org | http://www.escapebox.net
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