Date: Fri, 18 Oct 2002 10:10:55 -0700 From: "Crist J. Clark" <crist.clark@attbi.com> To: net@freebsd.org Subject: Strange FTP TCP Window Problem Message-ID: <20021018171055.GA45449@blossom.cjclark.org>
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This has got me stumped. I must be missing something obvious. I am
trying to download some files via FTP. There are four files. Three
download just fine, one just won't go. Since the three work fine, I
assume it's not PORT vs. PASV, NAT, or other firewall issues, that is,
the usual suspects have been eliminated. But what is really strange is
that it looks like _my client_ is the one causing the headaches.
Here is a tcpdump(8) of the data connection. Keep an eye on the window
values my client is sending back,
09:15:11.097800 a.b.c.136.29826 > d.e.f.17.18747: S [tcp sum ok] 2410623756:2410623756(0) win 16384 <mss 1460,nop,nop,sackOK,nop,wscale 0,nop,nop,timestamp 6027020 0> (ttl 64, id 50031, len 64)
09:15:11.118335 d.e.f.17.18747 > a.b.c.136.29826: S [tcp sum ok] 2932757104:2932757104(0) ack 2410623757 win 16384 <mss 512,nop,wscale 0,nop,nop,timestamp 1679619 6027020> (ttl 56, id 24108, len 60)
09:15:11.118443 a.b.c.136.29826 > d.e.f.17.18747: . [tcp sum ok] 1:1(0) ack 1 win 16500 <nop,nop,timestamp 6027020 1679619> (ttl 64, id 43640, len 52)
09:15:11.156424 d.e.f.17.18747 > a.b.c.136.29826: . 1:501(500) ack 1 win 16384 <nop,nop,timestamp 1679619 6027020> [tos 0x8] (ttl 56, id 24111, len 552)
09:15:11.159468 d.e.f.17.18747 > a.b.c.136.29826: . 501:1001(500) ack 1 win 16384 <nop,nop,timestamp 1679619 6027020> [tos 0x8] (ttl 56, id 24112, len 552)
09:15:11.227371 a.b.c.136.29826 > d.e.f.17.18747: . [tcp sum ok] 1:1(0) ack 1001 win 15500 <nop,nop,timestamp 6027020 1679619> [tos 0x8] (ttl 64, id 61006, len 52)
09:15:11.258205 d.e.f.17.18747 > a.b.c.136.29826: . 1001:1501(500) ack 1 win 16384 <nop,nop,timestamp 1679620 6027020> [tos 0x8] (ttl 56, id 24113, len 552)
09:15:11.261225 d.e.f.17.18747 > a.b.c.136.29826: . 1501:2001(500) ack 1 win 16384 <nop,nop,timestamp 1679620 6027020> [tos 0x8] (ttl 56, id 24114, len 552)
09:15:11.279923 d.e.f.17.18747 > a.b.c.136.29826: . 2001:2501(500) ack 1 win 16384 <nop,nop,timestamp 1679620 6027020> [tos 0x8] (ttl 56, id 24115, len 552)
09:15:11.427395 a.b.c.136.29826 > d.e.f.17.18747: . [tcp sum ok] 1:1(0) ack 2501 win 14000 <nop,nop,timestamp 6027021 1679620> [tos 0x8] (ttl 64, id 40196, len 52)
09:15:11.457865 d.e.f.17.18747 > a.b.c.136.29826: . 2501:3001(500) ack 1 win 16384 <nop,nop,timestamp 1679620 6027020> [tos 0x8] (ttl 56, id 24116, len 552)
09:15:11.461105 d.e.f.17.18747 > a.b.c.136.29826: . 3001:3501(500) ack 1 win 16384 <nop,nop,timestamp 1679620 6027020> [tos 0x8] (ttl 56, id 24117, len 552)
09:15:11.480485 d.e.f.17.18747 > a.b.c.136.29826: . 3501:4001(500) ack 1 win 16384 <nop,nop,timestamp 1679620 6027020> [tos 0x8] (ttl 56, id 24118, len 552)
09:15:11.483702 d.e.f.17.18747 > a.b.c.136.29826: . 4001:4501(500) ack 1 win 16384 <nop,nop,timestamp 1679620 6027020> [tos 0x8] (ttl 56, id 24119, len 552)
09:15:11.627707 a.b.c.136.29826 > d.e.f.17.18747: . [tcp sum ok] 1:1(0) ack 4501 win 12000 <nop,nop,timestamp 6027021 1679620> [tos 0x8] (ttl 64, id 44302, len 52)
09:15:11.648692 d.e.f.17.18747 > a.b.c.136.29826: . 4501:5001(500) ack 1 win 16384 <nop,nop,timestamp 1679620 6027020> [tos 0x8] (ttl 56, id 24120, len 552)
09:15:11.659731 d.e.f.17.18747 > a.b.c.136.29826: . 5001:5501(500) ack 1 win 16384 <nop,nop,timestamp 1679620 6027020> [tos 0x8] (ttl 56, id 24121, len 552)
09:15:11.670448 d.e.f.17.18747 > a.b.c.136.29826: . 5501:6001(500) ack 1 win 16384 <nop,nop,timestamp 1679620 6027020> [tos 0x8] (ttl 56, id 24122, len 552)
09:15:11.673581 d.e.f.17.18747 > a.b.c.136.29826: . 6001:6501(500) ack 1 win 16384 <nop,nop,timestamp 1679620 6027020> [tos 0x8] (ttl 56, id 24123, len 552)
09:15:11.692780 d.e.f.17.18747 > a.b.c.136.29826: . 6501:7001(500) ack 1 win 16384 <nop,nop,timestamp 1679620 6027020> [tos 0x8] (ttl 56, id 24124, len 552)
09:15:11.827393 a.b.c.136.29826 > d.e.f.17.18747: . [tcp sum ok] 1:1(0) ack 7001 win 9500 <nop,nop,timestamp 6027021 1679620> [tos 0x8] (ttl 64, id 38068, len 52)
09:15:11.855900 d.e.f.17.18747 > a.b.c.136.29826: . 7001:7501(500) ack 1 win 16384 <nop,nop,timestamp 1679621 6027020> [tos 0x8] (ttl 56, id 24125, len 552)
09:15:11.860077 d.e.f.17.18747 > a.b.c.136.29826: . 7501:8001(500) ack 1 win 16384 <nop,nop,timestamp 1679621 6027020> [tos 0x8] (ttl 56, id 24126, len 552)
09:15:11.878834 d.e.f.17.18747 > a.b.c.136.29826: . 8001:8501(500) ack 1 win 16384 <nop,nop,timestamp 1679621 6027020> [tos 0x8] (ttl 56, id 24127, len 552)
09:15:11.881856 d.e.f.17.18747 > a.b.c.136.29826: . 8501:9001(500) ack 1 win 16384 <nop,nop,timestamp 1679621 6027020> [tos 0x8] (ttl 56, id 24128, len 552)
09:15:11.892382 d.e.f.17.18747 > a.b.c.136.29826: . 9001:9501(500) ack 1 win 16384 <nop,nop,timestamp 1679621 6027020> [tos 0x8] (ttl 56, id 24129, len 552)
09:15:11.903415 d.e.f.17.18747 > a.b.c.136.29826: . 9501:10001(500) ack 1 win 16384 <nop,nop,timestamp 1679621 6027020> [tos 0x8] (ttl 56, id 24130, len 552)
09:15:12.027385 a.b.c.136.29826 > d.e.f.17.18747: . [tcp sum ok] 1:1(0) ack 10001 win 6500 <nop,nop,timestamp 6027022 1679621> [tos 0x8] (ttl 64, id 60342, len 52)
09:15:12.052757 d.e.f.17.18747 > a.b.c.136.29826: . 10001:10501(500) ack 1 win 16384 <nop,nop,timestamp 1679621 6027020> [tos 0x8] (ttl 56, id 24131, len 552)
09:15:12.063589 d.e.f.17.18747 > a.b.c.136.29826: . 10501:11001(500) ack 1 win 16384 <nop,nop,timestamp 1679621 6027020> [tos 0x8] (ttl 56, id 24132, len 552)
09:15:12.074515 d.e.f.17.18747 > a.b.c.136.29826: . 11001:11501(500) ack 1 win 16384 <nop,nop,timestamp 1679621 6027020> [tos 0x8] (ttl 56, id 24133, len 552)
09:15:12.078151 d.e.f.17.18747 > a.b.c.136.29826: . 11501:12001(500) ack 1 win 16384 <nop,nop,timestamp 1679621 6027020> [tos 0x8] (ttl 56, id 24134, len 552)
09:15:12.096930 d.e.f.17.18747 > a.b.c.136.29826: . 12001:12501(500) ack 1 win 16384 <nop,nop,timestamp 1679621 6027020> [tos 0x8] (ttl 56, id 24135, len 552)
09:15:12.099980 d.e.f.17.18747 > a.b.c.136.29826: . 12501:13001(500) ack 1 win 16384 <nop,nop,timestamp 1679621 6027020> [tos 0x8] (ttl 56, id 24136, len 552)
09:15:12.110647 d.e.f.17.18747 > a.b.c.136.29826: . 13001:13501(500) ack 1 win 16384 <nop,nop,timestamp 1679621 6027020> [tos 0x8] (ttl 56, id 24137, len 552)
09:15:12.227383 a.b.c.136.29826 > d.e.f.17.18747: . [tcp sum ok] 1:1(0) ack 13501 win 3000 <nop,nop,timestamp 6027022 1679621> [tos 0x8] (ttl 64, id 51576, len 52)
09:15:12.264837 d.e.f.17.18747 > a.b.c.136.29826: . 13501:14001(500) ack 1 win 16384 <nop,nop,timestamp 1679622 6027020> [tos 0x8] (ttl 56, id 24138, len 552)
09:15:12.268095 d.e.f.17.18747 > a.b.c.136.29826: . 14001:14501(500) ack 1 win 16384 <nop,nop,timestamp 1679622 6027020> [tos 0x8] (ttl 56, id 24139, len 552)
09:15:12.278653 d.e.f.17.18747 > a.b.c.136.29826: . 14501:15001(500) ack 1 win 16384 <nop,nop,timestamp 1679622 6027020> [tos 0x8] (ttl 56, id 24140, len 552)
09:15:12.289849 d.e.f.17.18747 > a.b.c.136.29826: . 15001:15501(500) ack 1 win 16384 <nop,nop,timestamp 1679622 6027020> [tos 0x8] (ttl 56, id 24141, len 552)
09:15:12.293592 d.e.f.17.18747 > a.b.c.136.29826: . 15501:16001(500) ack 1 win 16384 <nop,nop,timestamp 1679622 6027020> [tos 0x8] (ttl 56, id 24142, len 552)
09:15:12.427402 a.b.c.136.29826 > d.e.f.17.18747: . [tcp sum ok] 1:1(0) ack 16001 win 500 <nop,nop,timestamp 6027023 1679622> [tos 0x8] (ttl 64, id 41001, len 52)
09:15:17.202100 d.e.f.17.18747 > a.b.c.136.29826: . 16001:16501(500) ack 1 win 16384 <nop,nop,timestamp 1679631 6027020> [tos 0x8] (ttl 56, id 24157, len 552)
09:15:17.227476 a.b.c.136.29826 > d.e.f.17.18747: . [tcp sum ok] 1:1(0) ack 16501 win 0 <nop,nop,timestamp 6027032 1679631> [tos 0x8] (ttl 64, id 59052, len 52)
09:15:22.186435 d.e.f.17.18747 > a.b.c.136.29826: . [tcp sum ok] 16501:16502(1) ack 1 win 16384 <nop,nop,timestamp 1679641 6027020> [tos 0x8] (ttl 56, id 24183, len 53)
09:15:22.186625 a.b.c.136.29826 > d.e.f.17.18747: . [tcp sum ok] 1:1(0) ack 16501 win 0 <nop,nop,timestamp 6027042 1679641> [tos 0x8] (ttl 64, id 55942, len 52)
09:15:30.194393 d.e.f.17.18747 > a.b.c.136.29826: . [tcp sum ok] 16501:16502(1) ack 1 win 16384 <nop,nop,timestamp 1679657 6027020> [tos 0x8] (ttl 56, id 24221, len 53)
09:15:30.195913 a.b.c.136.29826 > d.e.f.17.18747: . [tcp sum ok] 1:1(0) ack 16501 win 0 <nop,nop,timestamp 6027058 1679657> [tos 0x8] (ttl 64, id 14020, len 52)
09:15:46.198335 d.e.f.17.18747 > a.b.c.136.29826: . [tcp sum ok] 16501:16502(1) ack 1 win 16384 <nop,nop,timestamp 1679689 6027020> [tos 0x8] (ttl 56, id 24333, len 53)
09:15:46.198583 a.b.c.136.29826 > d.e.f.17.18747: . [tcp sum ok] 1:1(0) ack 16501 win 0 <nop,nop,timestamp 6027090 1679689> [tos 0x8] (ttl 64, id 16087, len 52)
09:16:18.201164 d.e.f.17.18747 > a.b.c.136.29826: . [tcp sum ok] 16501:16502(1) ack 1 win 16384 <nop,nop,timestamp 1679753 6027020> [tos 0x8] (ttl 56, id 24500, len 53)
09:16:18.201409 a.b.c.136.29826 > d.e.f.17.18747: . [tcp sum ok] 1:1(0) ack 16501 win 0 <nop,nop,timestamp 6027154 1679753> [tos 0x8] (ttl 64, id 30338, len 52)
09:17:18.194176 d.e.f.17.18747 > a.b.c.136.29826: . [tcp sum ok] 16501:16502(1) ack 1 win 16384 <nop,nop,timestamp 1679873 6027020> [tos 0x8] (ttl 56, id 25061, len 53)
09:17:18.194430 a.b.c.136.29826 > d.e.f.17.18747: . [tcp sum ok] 1:1(0) ack 16501 win 0 <nop,nop,timestamp 6027274 1679873> [tos 0x8] (ttl 64, id 20615, len 52)
09:18:18.193763 d.e.f.17.18747 > a.b.c.136.29826: . [tcp sum ok] 16501:16502(1) ack 1 win 16384 <nop,nop,timestamp 1679993 6027020> [tos 0x8] (ttl 56, id 25447, len 53)
09:18:18.194005 a.b.c.136.29826 > d.e.f.17.18747: . [tcp sum ok] 1:1(0) ack 16501 win 0 <nop,nop,timestamp 6027394 1679993> [tos 0x8] (ttl 64, id 12107, len 52)
09:19:18.186418 d.e.f.17.18747 > a.b.c.136.29826: . [tcp sum ok] 16501:16502(1) ack 1 win 16384 <nop,nop,timestamp 1680113 6027020> [tos 0x8] (ttl 56, id 25862, len 53)
09:19:18.187970 a.b.c.136.29826 > d.e.f.17.18747: . [tcp sum ok] 1:1(0) ack 16501 win 0 <nop,nop,timestamp 6027514 1680113> [tos 0x8] (ttl 64, id 51084, len 52)
And this just hangs here forever.
I can't see why the client is refusing to accept more data. Like I
said, I'll bet I'm not seeing something obvious, but all of the SEQ
and ACK numbers look good to me. I should note that this isn't just an
issue with the FreeBSD ftp client. I get the same result with Windows,
Solaris, Cygwin, and OpenBSD too.
Why is it happening and how do I get around this?
--
Crist J. Clark | cjclark@alum.mit.edu
| cjclark@jhu.edu
http://people.freebsd.org/~cjc/ | cjc@freebsd.org
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