Window scaling problem?

[Jan Engelhardt <jengelh@linux01.gwdg.de>]

Hello,


for some reason unknown to me, some TCP connections just hang or get
reset after some kilobytes have been transferred. I suppose it is a
router with broken window scaling, but I can not say for sure from
the tcpdump logs.

Action:
  scp ahn.hopto.org:8megabytefile /home/jengelh/
  also affects interactive ssh sessions.
Result:
  After a few transferred kilobytes -- I rather suspect "a few
  seconds" -- either spuriously disconnects with a "Connection reset
  by peer" or just hangs.
Expected result:
  Continue operation.
Logs:
  http://jengelh.hopto.org/tcp/atw.txt    sender side
  http://jengelh.hopto.org/tcp/ahn.txt    receiver side
  http://jengelh.hopto.org/tcp/trace.txt  glimpse of topology

(There is a TCP FIN/RST at the end of atw.txt, which is when I hit
Ctrl+C to stop the (hung) scp.)

What puzzles me is that line 230 of ahn.txt shows a RST, while
there is no TCP RST sent in atw.txt. On top of that, the "R
889945325:889945325(0)" looks quite out of order.

When setting up a VPN over UDP tunnel (using vpnc) to our exit node,
connections seem to be fine. I hence suppose 10.10.96.1 to be
the culprit.

If anyone could take a look, I'd be grateful. Kernel currently
running is 2.6.18.5, but I have seen this with 2.6.17 I was running
two months ago too, so I do not suspect a kernel bug.


	-`J'
-- 
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/