Re: Sockets stuck in SYN_RCVD (re(4), RELENG_7, i386)

Pyun YongHyeon wrote:
On Tue, Nov 20, 2007 at 04:19:18PM +0100, Oliver Fromme wrote:
Some additional information.

Today I have run the re(4) interface at 100 Mbps for a few
hours. The count did still increase, so it's not a GigE-
only problem.

The I disabled RXCSUM,TXCSUM on the interface. Again, the
counter still increased. So hardware checksumming isn't
the cause of the problem either.

Anything else I could try?

re(4) is not smart enough to analyze packet payload. The hardware
also doesn't have a feature like TCP header split so I think re(4)
wouldn't have influence with TCP traffics by itself.

I see. So it does not seem to be a bug in re(4).

My first suspect were the IPFW rules. But they're quite
simple (only 20 rules) and I'm sure they're correct.
Apart from that, if it was a faulty rule that blocks
SYN+ACK packets or similar, then no TCP connections would
work at all. And even in that case, the default timeout
for SYN_RCVD is very short (45 seconds I think), but not
several days.

So my current suspect is a bug in the syncache code.
That bug is probably triggered by something exceptional,
because I don't see the problem on any other machine,
not even on the one which is almost identical in hardware
and OS.

I would like to ask everybody to have a look at the
output from "sysctl net.inet.tcp.syncache.count".
Does anybody else have a non-zero value that slowly
increases? If so, it would be interesting to find out
if there are any similarities with my machine.

Your dmesg indicates that you're using slightly old rgephy(4) on 7.0.
I touched rgephy(4) to support a newer PHY and fixed several bugs. If
speed/duplex mismatch was the cause of the issue you can see lots
of input errors from the output of "netstat -ndi" output. If so, try
latest rgephy(4).

I don't think that's the cause. I tried with and without
auto-select, forcing the interface to 100 and GigE, and
all of that did not affect the behaviour at all. The
error counters are all zero:

Name Mtu Network Address Ipkts Ierrs Opkts Oerrs Coll Drop
re0 1500 <Link#1> [...] 28363007 0 25430349 0 0 0

net.inet.tcp.syncache.count: 702

It's now at 731.

And now at 832. So it grows by more than 100 entries per
day.

Best regards
Oliver

--
Oliver Fromme, secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing b. M.
Handelsregister: Registergericht Muenchen, HRA 74606, Geschäftsfuehrung:
secnetix Verwaltungsgesellsch. mbH, Handelsregister: Registergericht Mün-
chen, HRB 125758, Geschäftsführer: Maik Bachmann, Olaf Erb, Ralf Gebhart

FreeBSD-Dienstleistungen, -Produkte und mehr: http://www.secnetix.de/bsd

Can the denizens of this group enlighten me about what the
advantages of Python are, versus Perl ?
"python" is more likely to pass unharmed through your spelling
checker than "perl".
-- An unknown poster and Fredrik Lundh
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