Re: Interesting TCP issue
- From: Uwe Doering <gemini@xxxxxxxxxxx>
- Date: Mon, 22 Jan 2007 09:15:13 +0100
Steve Watt wrote:
In <459AD141.5010502@xxxxxxxxxxxx>, 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@xxxxxxxxxxx | http://www.escapebox.net
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