[Remops] Corrupted packets from pyradic
mas at pyradic.dyndns.org
mas at pyradic.dyndns.org
Tue Apr 25 23:04:22 BST 2006
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Dear all,
The machine that was swapped in for a failing pyradic last weekend is
sending a low but significant amount of corrupted packets. I am
guessing this is a driver problem with the Intel IXP400 on-board
network card, but it might just as well be flakey hardware (it's a
Cisco device, but apparently that is not a guarantee for quality).
This inevitably leads to lost messages.
I have added the testing flag to the capstring to prevent automatic
routing from being affected by the problem. If I don't find out how
to circumvent the problem by tomorrow afternoon, I will be taking
pyradic down temporarily until a reliable replacement can be found.
Thanks to Trasher and Twisty admins for helping me debug things.
Regards,
Marc
[[ This is what happens: A typical strange packet would be "LIAMORF
a<:M>dcb" instead of "MAIL FROM:<abcd>". In other words, every 32-
bit word in the packet is reversed. The TCP header is usually not
affected, only the payload. It's occuring roughly once in 10.000 to
100.000 packets. Traffic shaping, queue length restriction, MTU
reduction, and load averaging have not helped at all; neither have
exchanging the cabling and moving the device right next to the
router, which admittedly are desperate measures to be undertaken at
midnight only. ;) Has anybody seen this before? Any hints? I'm
pretty certain it's not an application level problem; the MTA thinks
data goes out all right. The fact that (for most packets) only
payload is affected makes me believe it's probably a driver problem,
but then you'd think other people would have seen it too... Thing
is, if it's a problem with the driver, returning the device to the
vendor and getting another one of the same kind won't help me. ]]
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