> Date: Wed, 10 Jun 1998 00:56:34 +0100
> From: David Woodhouse <Dave@imladris.demon.co.uk>
>
> I forgot to take dumps from the server end. Next time it happens
> I'll remedy that.
>
> If you can catch it at the server, please do. It still looks
> mysterious, but I'm thinking about it.
>
>From the server end it looks much the same. Here's a dump from the client,
and from the server.
Client:
Linux sys5.axiom.internal 2.0.32 #1 Wed Nov 19 00:46:45 EST 1997 i486
unknown
13:21:08.022522 axiom.demon.co.uk.1021 > dwmw2.robinson.cam.ac.uk.22: S
1753780744:1753780744(0) win 512 <mss 472>
4500 002c a5f8 0000 4006 c900 9e98 1032
836f d999 03fd 0016 6888 9208 0000 0000
6002 0200 8f8b 0000 0204 01d8
13:21:08.192522 dwmw2.robinson.cam.ac.uk.22 > axiom.demon.co.uk.1021: S
1407640592:1407640592(0) ack 1753780745 win 32568 <mss 472> (DF)
4500 002c c6ba 4000 3506 733e 836f d999
9e98 1032 0016 03fd 53e6 e410 6888 9209
6012 7f38 da4a 0000 0204 01d8
13:21:08.192522 axiom.demon.co.uk.1021 > dwmw2.robinson.cam.ac.uk.22: .
ack 1 win 32568 (DF)
4500 0028 a5f9 4000 4006 8903 9e98 1032
836f d999 03fd 0016 6888 9209 53e6 e411
5010 7f38 ee2b 0000
13:21:08.352522 dwmw2.robinson.cam.ac.uk.22 > axiom.demon.co.uk.1021: R
1407640593:1407640593(0) win 0
4500 0028 c6bb 0000 f406 f440 836f d999
9e98 1032 0016 03fd 53e6 e411 0000 0000
5004 0000 6802 0000
Server:
Linux dwmw2.robinson.cam.ac.uk 2.1.105 #2 SMP Mon Jun 8 01:09:23 BST 1998
i586 unknown
13:20:33.157491 axiom.demon.co.uk.1021 > dwmw2.robinson.cam.ac.uk.22: S
1753780744:1753780744(0) win 512 <mss 472>
4500 002c a5f8 0000 3706 d200 9e98 1032
836f d999 03fd 0016 6888 9208 0000 0000
6002 0200 8f8b 0000 0204 01d8 0000
13:20:33.157629 dwmw2.robinson.cam.ac.uk.22 > axiom.demon.co.uk.1021: S
1407640592:1407640592(0) ack 1753780745 win 32568 <mss 472> (DF)
4500 002c c6ba 4000 4006 683e 836f d999
9e98 1032 0016 03fd 53e6 e410 6888 9209
6012 7f38 da4a 0000 0204 01d8
13:20:33.327161 axiom.demon.co.uk.1021 > dwmw2.robinson.cam.ac.uk.22: .
ack 1 win 32568 (DF)
4500 0028 a5f9 4000 3706 9203 9e98 1032
836f d999 03fd 0016 6888 9209 53e6 e411
5010 7f38 ee2b 0000 0b1a 8b50 48f1
13:20:33.327288 dwmw2.robinson.cam.ac.uk.22 > axiom.demon.co.uk.1021: R
1407640593:1407640593(0) win 0
4500 0028 c6bb 0000 ff06 e940 836f d999
9e98 1032 0016 03fd 53e6 e411 0000 0000
5004 0000 6802 0000
I now have an idea what might be causing it.
I'm using diald at the client end to bring up the PPP link. On occasion
(and quite possibly on the occasions this has happened) I attempt to SSH
into my own machine, and then get bored and press ^C before the PPP link
has finished coming up.
However, the outgoing SYN packet is already in the outgoing queue for
diald, and gets sent as soon as the link comes up. So my home machine will
respond to it, and then get told "WTF are you talking about" by the client
machine. Is it possible that my home machine then starts sulking for ten
minutes or so, thinking that it's being SYN flooded? During that time, it
just refuses to talk to this client, but if I SSH into another one
upstairs, and then in from there, it works fine.
---- ---- ----
David Woodhouse, Robinson College, CB3 9AN, England. (+44) 0976 658355
Dave@imladris.demon.co.uk http://www.imladris.demon.co.uk
finger pgp@dwmw2.robinson.cam.ac.uk for PGP key.
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