Date: Tue, 17 Dec 96 10:02:45 CDT From: newton@communica.com.au (Mark Newton) To: freebsd-hackers@freebsd.org Subject: Problems with TCP? Message-ID: <9612162332.AA20060@communica.com.au>
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I experienced a problem on one of my machines this morning.
The machine has had bpf in its kernel for quite some time now; I
removed the packet filter over the weekend, thinking it wouldn't cause
any problems since the need for me to have it installed has passed
(I used to boot a Sun diskless, but now it has a disk).
So -- I removed the "pseudo-device bpfilter" line from the kernel
config file, config, make depend, make, make install and reboot.
When the system came up, it was unable to carry out TCP conversations
with a number of systems it must regularly talk to; I didn't find
this out 'til later in the weekend when I started getting bouncemail
messages caused by the fact that sendmail was unable to flush its
queue at those machines.
The bounce messages complained of a timeout exceeded while waiting
for a 250 response to the EHLO command. Thinking it might be the
fault of the machine at the other end, I attempted to manually duplicate
the problem:
newton@atdot> telnet ns.satech.net.au. smtp
Trying 203.1.91.3...
Connected to ns.satech.net.au.
Escape character is '^]'.
220 box.satech.net.au ESMTP Sendmail Tue, 17 Dec 1996 09:45:54 +1030
HELO atdot.dotat.org
250 box.satech.net.au Hello dotat-gw.apana.org.au [203.14.159.1], pleased to mee
... and there it sat, half way through the response to the "HELO" command,
with the cursor at the end of the line presumably waiting for the next
few bytes to say "t you\n"
Looking at my logs, it seemed apparent that this problem started when I
booted my new kernel, so I pulled it out and rebooted with my old kernel.
Hey presto, problem went away.
Just to make sure, I rebuilt a new kernel after adding the bpfilter line
back to the config file (just in case I had made some other change I had
forgotten about prior to making the bpfilter change). Result: Can't
talk TCP to satech anymore (not just the SMTP service either, although
I'd hope that that would be an intuitive assumption for readers here :-)
My problem: Without bpf in the kernel I can't get packet dumps to
diagnose the problem that seems to occur without bpf in the kernel <grin>.
As a result, it's difficult to provide more information than version
numbers with my setup :-/
FYI - ns.satech.net.au is a <shock, horror> Linux 2.0.23 system.
Another system which presented exactly the same problem to me was
bunux.senet.com.au, which (I think) also runs Linux, but I'm sending
out some email to verify that.
Do we have a basic incompatibility between FreeBSD and Linux TCP which
asserts itself when the packet filter is enabled? Could TTCP modifications
have caused bogosity like this?
- mark
---
Mark Newton Email: newton@communica.com.au
Systems Engineer Phone: +61-8-8373-2523
Communica Systems WWW: http://www.communica.com.au
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