From: Philipp Reisner <philipp.reisner@cubit.at>
To: linux-kernel@vger.kernel.org
Subject: tcp connection hangs on connect
Date: Fri, 3 Aug 2001 09:00:26 +0200 [thread overview]
Message-ID: <20010803090026.C31230@cubit.at> (raw)
Hi,
I have discovered here something that causes TCP connections to
hang if one of the initial packets is lost.
We have a script which runs scp every 10 seconds, and the script
simply hangs after some minutes to an hour. The script runs on
a Linux-2.2.19 Box (we have also tested Linux-2.4.2) and the ssh server
is running on some Windows box.
Here is the good case:
15:26:11.100413 192.168.53.4.4819 > 212.31.78.62.22: S 2626815412:2626815412(0) +win 16060 <mss 1460,sackOK,timestamp 809461847[|tcp]> (DF)
15:26:11.119964 212.31.78.62.22 > 192.168.53.4.4819: S 3560917622:3560917622(0) +ack 2626815413 win 17520 <mss 1460,nop,wscale 0,nop,nop,timestamp[|tcp]> (DF)
15:26:11.120011 192.168.53.4.4819 > 212.31.78.62.22: . ack 1 win 16060 +<nop,nop,timestamp 809461848 0> (DF)
15:26:11.228046 212.31.78.62.22 > 192.168.53.4.4819: P 1:24(23) ack 1 win 17520 +<nop,nop,timestamp 6062108 809461848> (DF)
Here is the hang:
12:01:24.753703 192.168.53.4.4442 > 212.31.78.62.22: S 2538486974:2538486974(0) +win 16060 <mss 1460,sackOK,timestamp 808233194[|tcp]> (DF)
12:01:24.798610 212.31.78.62.22 > 192.168.53.4.4442: S 3871618076:3871618076(0) +ack 2538486975 win 17520 <mss 1460,nop,wscale 0,nop,nop,timestamp[|tcp]> (DF)
12:01:24.798729 192.168.53.4.4442 > 212.31.78.62.22: . ack 1 win 16060 +<nop,nop,timestamp 808233198 0> (DF)
12:01:28.048197 212.31.78.62.22 > 192.168.53.4.4442: S 3871618076:3871618076(0) +ack 2538486975 win 17520 <mss 1460,nop,wscale 0,nop,nop,timestamp[|tcp]> (DF)
12:01:34.611132 212.31.78.62.22 > 192.168.53.4.4442: S 3871618076:3871618076(0) +ack 2538486975 win 17520 <mss 1460,nop,wscale 0,nop,nop,timestamp[|tcp]> (DF)
192.168.53.4: Is the Linux box.
212.31.78.62: Is the Windows box.
It looks like that the packet at 12:01:24.798729 never reaches the Windows
box. Ok -- That is probabely why the Windows box resends it's syn packet
(at 12:01:28.048197 and 12:01:34.611132).
BTW, the Linux box is convinced that the connection is established
(confirmed with lsof), while the Windows box probabely does not think
that there is a connection.
The question is, why is Linux not responding to the resent syn packets ?
PS: the process (scp/ssh) on the Linux side of the connection wants
to read from the socket (confirmed with strace).
-Philipp
next reply other threads:[~2001-08-03 7:00 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-08-03 7:00 Philipp Reisner [this message]
2001-08-05 2:04 ` tcp connection hangs on connect Alexey Kuznetsov
[not found] <20010828171705.F890@boardwalk>
[not found] ` <20010829082405.A5966@cubit.at>
2001-08-30 0:20 ` Val Henson
2001-08-30 0:55 ` David S. Miller
2001-08-30 1:53 ` Val Henson
2001-08-30 16:21 ` kuznet
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