Date: Mon, 25 Sep 2006 08:56:58 -0700 From: John-Mark Gurney <gurney_j@resnet.uoregon.edu> To: Dan Nelson <dnelson@allantgroup.com> Cc: mohans@FreeBSD.org, Andre Oppermann <andre@FreeBSD.org>, current@FreeBSD.org, net@FreeBSD.org Subject: Re: odd TCP rtt/retransmit timeout issue... Message-ID: <20060925155658.GB80527@funkthat.com> In-Reply-To: <20060925154659.GE73717@dan.emsphone.com> References: <20060925095745.GA80527@funkthat.com> <20060925154659.GE73717@dan.emsphone.com>
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Dan Nelson wrote this message on Mon, Sep 25, 2006 at 10:46 -0500:
> In the last episode (Sep 25), John-Mark Gurney said:
> > I was brining up another interface that I just added to /etc/rc.conf
> > and ran the command /etc/rc.d/netif start to initalize it... But
> > then my connection never came back.... I found that the shell was
> > still active as I could type commands like sleep 5, and another
> > session's w would see sleep 5 run on the session... even filling up
> > the send-q w/ 32k of data didn't get the HEAD box to send any data to
> > the client...
> >
> > With the help of silby, I managed to find that the t_rxtcur value in
> > the tcpcb was getting a very large value. The session that hung had
> > a retransmit timeout of 19 days... This led us to find that the
> > TCPT_RANGESET macro was letting very large tvmin values override the
> > more sane tvmax values due to an extra else. I have added that so we
> > shouldn't see any more multi day timeouts, but we still apparently
> > have a problem where the rtt value calculated is wildly incorrect...
> >
> > It appears that each connection will get a different "random" rtt
> > values... From a few connections to my machine:
> > (kgdb) print ((struct tcpcb *)0xc3a34af8)->t_rxtcur
> > $3 = 64000
> > (kgdb) print ((struct tcpcb *)0xc3a3457c)->t_rxtcur
> > $6 = 1662654093
> > (kgdb) print ((struct tcpcb *)0xc3a343a8)->t_rxtcur
> > $12 = 1358
> > (kgdb) print ((struct tcpcb *)0xc3a9e1d4)->t_rxtcur
> > $17 = 203
> > (kgdb) print ((struct tcpcb *)0xc3a9e000)->t_rxtcur
> > $19 = 284155863
>
> Do you have net.inet.tcp.inflight.enable=1 ? You might be hitting
Yes.
> something related to kern/75122. You'll want to pull the raw gnats
> repository file to read it; the query-pr.cgi web interface doesn't
> parse the file right and it loses all the replies.
Doesn't look like it... I just disabled inflight, and my first connection
got:
(kgdb) print ((struct tcpcb *)0xc3a4857c)->t_rxtcur
$1 = 921479340
--
John-Mark Gurney Voice: +1 415 225 5579
"All that I will do, has been done, All that I have, has not."
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