Date: Wed, 25 Mar 1998 05:10:53 +0000 From: Arman Hazairin <arman@ai3.net> To: dg@root.com, freebsd-hackers@FreeBSD.ORG Subject: Re: TCP connection hang Message-ID: <351891DD.7631D28@ai3.net> References: <199803242054.MAA25910@implode.root.com>
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David Greenman wrote: > > >The SCO box never sent any FIN packet because it never finish the > >transfer. > >That two boxes just kept silent, SCO waiting for ACK it never received > >(the last 5 packets in tcpdump output below), the FreeBSD box just kept > >silent after sending ack for seq. 4225. After all the sequence below, > >the connection is hang forever until timeout occur. > > Does either side attempt retransmission? At the very least, the SCO machine > should continue to retransmit the segments until it gets an ACK. Also, on > which side is this tcpdump taken - closest to the SCO or closest to the > FreeBSD? > > -DG > > David Greenman > Core-team/Principal Architect, The FreeBSD Project The machines are: 68.10.3.1 ---> SCO 3.2.2, acting as ftp server. 20.12.39.21 --> FreeBSD 2.2.2-RELEASE, acting as ftp client, tcpdump was taken here. If you look into full trace of ftp session below, there are no retransmission attempt from either side. -arman- -----> more info transcript of ftp session follows: ftp> dir 200 PORT command successful. 150 Opening ASCII mode data connection for /bin/ls (0 bytes). total 3054 -rw------- 1 guest group 775 Mar 20 14:39 .kshrc -r-------- 1 guest auth 0 Mar 25 01:13 .lastlogin -rw------- 1 guest group 1455 Mar 20 14:39 .profile -rw------- 1 guest group 18 Mar 24 16:41 .rhosts -rw------- 1 guest group 2876 Mar 25 01:59 .sh_history -rwxr-xr-x 1 guest group 73003 Mar 23 21:18 asem -rwxrwxrwx 1 guest other 1474560 Mar 24 10:36 kermitdsk.dd # 226 Transfer complete. ftp> get kermitdsk.dd local: kermitdsk.dd remote: kermitdsk.dd 200 PORT command successful. 150 Opening BINARY mode data connection for kermitdsk.dd (1474560 bytes). #### ftp: netin: Connection reset by peer 426 Data connection: Connection timed out. ftp> ---> start of tcpdump output for ftp-data 04:26:59.687805 20.12.39.21.2185 > 68.10.3.1.ftp: P 3297487385:3297487393(8) ack 5969855 win 16384 (DF) [tos 0x10] 04:26:59.705190 68.10.3.1.ftp > 20.12.39.21.2185: P 1:21(20) ack 8 win 4096 [tos 0x10] 04:26:59.705635 20.12.39.21.2185 > 68.10.3.1.ftp: P 8:34(26) ack 21 win 16384 (DF) [tos 0x10] 04:26:59.726661 68.10.3.1.ftp > 20.12.39.21.2185: P 21:51(30) ack 34 win 4096 [tos 0x10] 04:26:59.727118 20.12.39.21.2185 > 68.10.3.1.ftp: P 34:53(19) ack 51 win 16384 (DF) [tos 0x10] 04:26:59.755820 68.10.3.1.ftp-data > 20.12.39.21.40058: S 11537409:11537409(0) win 4096 [tos 0x8] 04:26:59.755971 20.12.39.21.40058 > 68.10.3.1.ftp-data: S 3305878336:3305878336(0) ack 11537410 win 16384 <mss 1460> (DF) 04:26:59.777546 68.10.3.1.ftp-data > 20.12.39.21.40058: . ack 1 win 4096 [tos 0x8] 04:26:59.788973 68.10.3.1.ftp > 20.12.39.21.2185: P 51:126(75) ack 53 win 4096 [tos 0x10] 04:26:59.840074 20.12.39.21.2185 > 68.10.3.1.ftp: . ack 126 win 16384 (DF) [tos 0x10] 04:26:59.856296 68.10.3.1.ftp-data > 20.12.39.21.40058: . 1:513(512) ack 1 win 4096 [tos 0x8] 04:27:00.040076 20.12.39.21.40058 > 68.10.3.1.ftp-data: . ack 513 win 16384 (DF) [tos 0x8] 04:27:00.123678 68.10.3.1.ftp-data > 20.12.39.21.40058: . 513:1025(512) ack 1 win 4096 [tos 0x8] 04:27:00.189797 68.10.3.1.ftp-data > 20.12.39.21.40058: . 1025:1537(512) ack 1 win 4096 [tos 0x8] 04:27:00.189934 20.12.39.21.40058 > 68.10.3.1.ftp-data: . ack 1537 win 16384 (DF) [tos 0x8] 04:27:00.271174 68.10.3.1.ftp-data > 20.12.39.21.40058: . 1537:2049(512) ack 1 win 4096 [tos 0x8] 04:27:00.338440 68.10.3.1.ftp-data > 20.12.39.21.40058: . 2049:2561(512) ack 1 win 4096 [tos 0x8] 04:27:00.338574 20.12.39.21.40058 > 68.10.3.1.ftp-data: . ack 2561 win 16384 (DF) [tos 0x8] 04:27:00.404674 68.10.3.1.ftp-data > 20.12.39.21.40058: . 2561:3073(512) ack 1 win 4096 [tos 0x8] 04:27:00.440069 20.12.39.21.40058 > 68.10.3.1.ftp-data: . ack 3073 win 16384 (DF) [tos 0x8] 04:27:00.471644 68.10.3.1.ftp-data > 20.12.39.21.40058: . 3073:3585(512) ack 1 win 4096 [tos 0x8] 04:27:00.537701 68.10.3.1.ftp-data > 20.12.39.21.40058: . 3585:4097(512) ack 1 win 4096 [tos 0x8] 04:27:00.537835 20.12.39.21.40058 > 68.10.3.1.ftp-data: . ack 4097 win 16384 (DF) [tos 0x8] 04:27:00.603982 68.10.3.1.ftp-data > 20.12.39.21.40058: . 4097:4609(512) ack 1 win 4096 [tos 0x8] 04:27:00.640063 20.12.39.21.40058 > 68.10.3.1.ftp-data: . ack 4609 win 16384 (DF) [tos 0x8] 04:27:00.801730 68.10.3.1.ftp-data > 20.12.39.21.40058: . 4609:5121(512) ack 1 win 4096 [tos 0x8] 04:27:00.868930 68.10.3.1.ftp-data > 20.12.39.21.40058: . 5121:5633(512) ack 1 win 4096 [tos 0x8] 04:27:00.936216 68.10.3.1.ftp-data > 20.12.39.21.40058: . 5633:6145(512) ack 1 win 4096 [tos 0x8] 04:27:01.002594 68.10.3.1.ftp-data > 20.12.39.21.40058: . 6145:6657(512) ack 1 win 4096 [tos 0x8] 04:27:01.069431 68.10.3.1.ftp-data > 20.12.39.21.40058: . 6657:7169(512) ack 1 win 4096 [tos 0x8] ---> connection start hanging here 04:36:02.647386 68.10.3.1.ftp-data > 20.12.39.21.40058: R 5121:5121(0) ack 1 win 4096 [tos 0x8] 04:36:02.655971 68.10.3.1.ftp > 20.12.39.21.2185: P 126:170(44) ack 53 win 4096 [tos 0x10] 04:36:02.840061 20.12.39.21.2185 > 68.10.3.1.ftp: . ack 170 win 16384 (DF) [tos 0x10] ---> connection reset by remote peer (ftp-data) 04:38:27.652472 20.12.39.21.2185 > 68.10.3.1.ftp: P 53:59(6) ack 170 win 16384 (DF) [tos 0x10] 04:38:27.669028 68.10.3.1.ftp > 20.12.39.21.2185: P 170:184(14) ack 59 win 4096 [tos 0x10] 04:38:27.669497 20.12.39.21.2185 > 68.10.3.1.ftp: F 59:59(0) ack 184 win 16384 (DF) [tos 0x10] 04:38:27.676225 68.10.3.1.ftp > 20.12.39.21.2185: F 184:184(0) ack 59 win 4096 [tos 0x10] 04:38:27.676353 20.12.39.21.2185 > 68.10.3.1.ftp: F 59:59(0) ack 185 win 16384 (DF) [tos 0x10] 04:38:27.688231 68.10.3.1.ftp > 20.12.39.21.2185: F 184:184(0) ack 60 win 4096 [tos 0x10] 04:38:27.688324 20.12.39.21.2185 > 68.10.3.1.ftp: . ack 185 win 16384 (DF) [tos 0x10] 04:38:27.692666 68.10.3.1.ftp > 20.12.39.21.2185: . ack 60 win 4096 [tos 0x10] ---> ftp connection closed To Unsubscribe: send mail to 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