Date: Sat, 19 Apr 2008 19:56:43 +0200 From: Oliver Lehmann <oliver@FreeBSD.org> To: net@freebsd.org Subject: problems interacting on TCP level with K5JB Message-ID: <20080419195643.a5187267.oliver@FreeBSD.org>
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Hi,
I've an old UNIX SYSIII system where I want to get IP running with K5JB.
I've modified the code (and even my C-Compiler...) as far as I could to
get it working.
Right now, FreeBSD and K5JB are able to communicate via ICMP. Ping(8)
for example works fine. They are connected together via SLIP.
The next step was getting them to communcate via TCP/IP.
And here is the problem.
I've started the echo service in K5JB and tried to get an answer while
pinging it with comms/echoping on my FreeBSD system. K5JB responses the
SYN with another SYN packet. But FreeBSD then sends a RST packet back
to K5JB and the whole thing starts again - SYN-SYN-RST and so on until
timeout.
I'm guessing something of the 2nd SYN packet (the one K5JB returns to
FreeBSD) is wrong and thats why FreeBSD is responding with an RST.
I've tcpdumped the session and here is one round (SYN-SYN-RST).
10.1.1.1 is the FreeBSD-box, 10.1.1.2 is the old UNIX-box running K5JB:
19:22:31.003359 IP (tos 0x10, ttl 64, id 730, offset 0, flags [DF], proto TCP (6), length 60) 10.1.1.1.54398 > 10.1.1.2.telnet: S, cksum 0xceef (correct), 1217851052:1217851052(0) win 65535 <mss 512,nop,wscale 3,sackOK,timestamp 34167010 0>
0x0000: 0145 1000 3c02 da40 0040 0621 ce0a 0101 .E..<..@.@.!....
0x0010: 4510 003c 02da 4000 4006 21ce 0a01 0101 E..<..@.@.!.....
0x0020: 0a01 0102 d47e 0017 4896 eeac 0000 0000 .....~..H.......
0x0030: a002 ffff ceef 0000 0204 0200 0103 0303 ................
0x0040: 0402 080a 0209 58e2 0000 0000 ......X.....
19:22:31.301210 IP (tos 0x0, ttl 254, id 25, offset 0, flags [none], proto TCP (6), length 44) 10.1.1.2.telnet > 10.1.1.1.54398: S, cksum 0xe752 (correct), 2405380816:2405380816(0) ack 4294967213 win 2048 <mss 512>
0x0000: 0045 0000 2c00 1900 00fe 06a6 ae0a 0101 .E..,...........
0x0010: 4500 002c 0019 0000 fe06 a6ae 0a01 0102 E..,............
0x0020: 0a01 0101 0017 d47e 8f5f 32d0 ffff ffad .......~._2.....
0x0030: 6012 0800 e752 0000 0204 0200 `....R......
19:22:31.301234 IP (tos 0x0, ttl 64, id 747, offset 0, flags [DF], proto TCP (6), length 40) 10.1.1.1.54398 > 10.1.1.2.telnet: R, cksum 0xc598 (correct), 4294967213:4294967213(0) win 0
0x0000: 0145 0000 2802 eb40 0040 0621 e10a 0101 .E..(..@.@.!....
0x0010: 4500 0028 02eb 4000 4006 21e1 0a01 0101 E..(..@.@.!.....
0x0020: 0a01 0102 d47e 0017 ffff ffad 0000 0000 .....~..........
0x0030: 5004 0000 c598 0000 P.......
I also tried echoping between two FreeBSD systems connected via SLIP.
To get the scenario as same as possible they also have the same IP.
As you might see, the 2nd SYN the other FreeBSD system returns con-
tains more data.
17:46:20.681912 IP (tos 0x0, ttl 64, id 38344, offset 0, flags [DF], proto TCP (6), length 60) 10.1.1.1.57847 > 10.1.1.2.echo: S, cksum 0xc9c2 (correct), 1669585125:1669585125(0) win 65535 <mss 512,nop,wscale 3,sackOK,timestamp 28396504 0>
0x0000: 0145 0000 3c95 c840 0040 068e ef0a 0101 .E..<..@.@......
0x0010: 4500 003c 95c8 4000 4006 8eef 0a01 0101 E..<..@.@.......
0x0020: 0a01 0102 e1f7 0007 6383 d8e5 0000 0000 ........c.......
0x0030: a002 ffff c9c2 0000 0204 0200 0103 0303 ................
0x0040: 0402 080a 01b1 4bd8 0000 0000 ......K.....
17:46:20.837546 IP (tos 0x0, ttl 64, id 38, offset 0, flags [DF], proto TCP (6), length 64) 10.1.1.2.echo > 10.1.1.1.57847: S, cksum 0x1851 (correct), 3664889775:3664889775(0) ack 1669585126 win 65535 <mss 512,nop,wscale 3,nop,nop,timestamp 1676122706 28396504,sackOK,eol>
0x0000: 0045 0000 4000 2640 0040 0624 8e0a 0101 .E..@.&@.@.$....
0x0010: 4500 0040 0026 4000 4006 248e 0a01 0102 E..@.&@.@.$.....
0x0020: 0a01 0101 0007 e1f7 da71 c7af 6383 d8e6 .........q..c...
0x0030: b012 ffff 1851 0000 0204 0200 0103 0303 .....Q..........
0x0040: 0101 080a 63e7 9a52 01b1 4bd8 0402 0000 ....c..R..K.....
17:46:20.837581 IP (tos 0x0, ttl 64, id 38345, offset 0, flags [DF], proto TCP (6), length 52) 10.1.1.1.57847 > 10.1.1.2.echo: ., cksum 0x3394 (correct), 1:1(0) ack 1 win 8250 <nop,nop,timestamp 28396660 1676122706>
0x0000: 0145 0000 3495 c940 0040 068e f60a 0101 .E..4..@.@......
0x0010: 4500 0034 95c9 4000 4006 8ef6 0a01 0101 E..4..@.@.......
0x0020: 0a01 0102 e1f7 0007 6383 d8e6 da71 c7b0 ........c....q..
0x0030: 8010 203a 3394 0000 0101 080a 01b1 4c74 ...:3.........Lt
0x0040: 63e7 9a52 c..R
Can one of you net-gurus tell me what FreeBSD expects from K5JB to
send to process it's SYN so the communication can move on?
please keep me CCed - I'm not subscribed to the list.
--
Oliver Lehmann
http://www.pofo.de/
http://wishlist.ans-netz.de/
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