[4006] in linux-net channel archive
Strange Problem with Linux 2.0 TCP
daemon@ATHENA.MIT.EDU (Andi Kleen)
Mon Aug 12 17:40:36 1996
To: linux-net@vger.rutgers.edu
Date: Sun, 11 Aug 1996 12:51:43 +0200
From: Andi Kleen <andi@mlm.extern.lrz-muenchen.de>
Hi,
I just discovered that telnet to our main linux server (RH 3.0.3/2.0.8)
doesn't work anymore. I tried to track the problem down and it looks
like a TCP bug:
Trying 141.84.33.1...
Connected to maja.mlm.extern.lrz-muenchen.de.
Escape character is '^]'.
maja (MLM)
and then nothing. ps shows that it hangs in the login process. strace
on the login process shows that it hangs in the write to stdout, strace
on the telnetd process shows this:
select(16, [0 3], [], [0], NULL
tcp 0 117 maja:telnet bse:1720 ESTABLISHED root
This is the tcpdump:
12:35:58.454772 frob.1375 > maja.telnet: S 2728469057:2728469057(0) win 512 <mss 1460>
12:35:58.454772 maja.telnet > frob.1375: S 3955995639:3955995639(0) ack 2728469058 win 31744 <mss 1460>
12:35:58.454772 frob.1375 > maja.telnet: . ack 1 win 2048 (DF)
12:35:58.464772 frob.1375 > maja.telnet: . 1:25(24) ack 1 win 4096 (DF)
12:35:58.594772 maja.telnet > frob.1375: P 1:4(3) ack 25 win 31744 (DF)
12:35:58.594772 frob.1375 > maja.telnet: . 25:28(3) ack 4 win 4096 (DF)
12:35:58.594772 maja.telnet > frob.1375: P 4:28(24) ack 25 win 31744 (DF)
12:35:58.784772 maja.telnet > frob.1375: P 4:28(24) ack 28 win 31744 (DF)
12:35:58.784772 frob.1375 > maja.telnet: . ack 28 win 4096 (DF)
12:35:58.784772 maja.telnet > frob.1375: P 28:31(3) ack 28 win 31744 (DF)
12:35:58.784772 frob.1375 > maja.telnet: . 28:37(9) ack 31 win 4096 (DF)
12:35:59.124772 maja.telnet > frob.1375: . ack 37 win 31744
12:35:59.124772 frob.1375 > maja.telnet: . 37:40(3) ack 31 win 4096 (DF)
12:35:59.124772 maja.telnet > frob.1375: P 31:49(18) ack 40 win 31744 (DF)
12:35:59.144772 frob.1375 > maja.telnet: . ack 49 win 4096 (DF)
12:35:59.144772 frob.1375 > maja.telnet: . 40:74(34) ack 49 win 4096 (DF)
12:35:59.154772 maja.telnet > frob.1375: P 49:52(3) ack 74 win 31744 (DF)
12:35:59.154772 frob.1375 > maja.telnet: . 74:77(3) ack 52 win 4096 (DF)
12:35:59.164772 maja.telnet > frob.1375: P 52:69(17) ack 77 win 31744 (DF)
12:35:59.164772 frob.1375 > maja.telnet: . 77:80(3) ack 69 win 4096 (DF)
12:35:59.194772 maja.telnet > frob.1375: . ack 80 win 31744
12:36:08.274772 frob.1375 > maja.telnet: F 80:80(0) ack 69 win 4096 (DF)
12:36:08.274772 maja.telnet > frob.1375: . ack 81 win 31744
12:36:08.284772 maja.telnet > frob.1375: F 69:69(0) ack 81 win 31744
12:36:08.284772 frob.1375 > maja.telnet: . ack 70 win 4096 (DF)
and then it stops and and the connection hangs. Other servers
(sendmail, ftp, finger, squid, cern httpd) work. sshd and rlogind
hang too. I tried telnetting from a Linux 2.0.10 box, a box with
2.0.10+pedro's netpatch and from FreeBSD 2.2. The strange thing
is that it worked from the BSD box 2-3x when it didn't from one
of the Linux boxes, but after 3 telnets or so it stopped working
too.
-Andi
--
|andi@mlm.extern.lrz-muenchen.de Nonsense is better than no sense at all.
| -NoMeansNo,0-1=2
