TCP: connection reset by peer (2.1.105)

David Woodhouse (Dave@imladris.demon.co.uk)
Wed, 10 Jun 1998 00:56:34 +0100

When attempting to SSH into my machine earlier today from a dial-up connection,
I received the message "connection reset by peer". The problem was not 100%
reproducible - some attempts to connect would work, and some would not.

The client:
Fairly basic Red Hat 5.0, kernel 2.0.32 on a 486, connected to the 'net by PPP
through a 33.6Kb/s modem. Diald in operation, but the link was up already
before the ssh attempts.

The server:
Red Hat 5.1, kernel 2.1.105 on a pair of Pentiums, connected by Ethernet.

This is a tcpdump of one of the failed connections (taken from the client end):

19:08:08.853014 axiom.demon.co.uk.1022 > dwmw2.robinson.cam.ac.uk.22: S 1479778505:1479778505(0) win 512 <mss 472>
19:08:08.993014 dwmw2.robinson.cam.ac.uk.22 > axiom.demon.co.uk.1022: S 4139545601:4139545601(0) ack 1479778506 win 32568 <mss 472> (DF)
19:08:08.993014 axiom.demon.co.uk.1022 > dwmw2.robinson.cam.ac.uk.22: . ack 1 win 32568 (DF)
19:08:09.133014 dwmw2.robinson.cam.ac.uk.22 > axiom.demon.co.uk.1022: R 4139545602:4139545602(0) win 0

And the beginning of a working one:

19:14:04.564962 axiom.demon.co.uk.1020 > dwmw2.robinson.cam.ac.uk.22: S 1069421359:1069421359(0) win 512 <mss 472>
19:14:04.724962 dwmw2.robinson.cam.ac.uk.22 > axiom.demon.co.uk.1020: S 240687823:240687823(0) ack 1069421360 win 32568 <mss 472> (DF)
19:14:04.724962 axiom.demon.co.uk.1020 > dwmw2.robinson.cam.ac.uk.22: . ack 1 win 32568 (DF)
19:14:04.904962 dwmw2.robinson.cam.ac.uk.22 > axiom.demon.co.uk.1020: P 1:16(15) ack 1 win 32568 (DF) [tos 0x10]
19:14:04.924962 axiom.demon.co.uk.1020 > dwmw2.robinson.cam.ac.uk.22: . ack 16 win 32568 (DF) [tos 0x10]
19:14:04.974962 axiom.demon.co.uk.1020 > dwmw2.robinson.cam.ac.uk.22: P 1:16(15) ack 16 win 32568 (DF) [tos 0x10]
19:14:05.214932 dwmw2.robinson.cam.ac.uk.22 > axiom.demon.co.uk.1020: P 16:292(276) ack 16 win 32568 (DF) [tos 0x10]

I forgot to take dumps from the server end. Next time it happens I'll remedy
that.

---- ---- ----
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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