Discussion:
Bad NetBios name query bringing down network
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Henry Markov
2010-06-09 15:57:18 UTC
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One XP/SP2 machine in our private network of about 85 identical machines
occasionally is the source of a NetBios name query message that has a bad
TCP checksum as indicated by a WireShark trace. In the case we most closely
investigated the high order octet of the source IP address got a bit flipped
so that 192 became 196. This produced a TCP checksum error but not a UDP
checksum error. Immediately upon broadcast of this errored packet all
networking to all machines on the network except for the source machine was
permanently disabled however switches and a non-MS system on the network
remained intact. Networking could only be restored by rebooting all
machines.

I used Wireshark to capture a good name query message and then I corrupted
it in the same way that it had been corrupted in production. I used the
ColaSoft Packet Player to play this message back into a switch and all MS XP
hosts had their networking disabled exactly as in the production scenario.

The machines use XP-Embedded and are headless, etc. so visibility into these
machines is limited and we need to enhance that. Note that XP-Embedded uses
the same OS code as desktop XP so I assume we are dealing with a generic XP
issue. Pending more investigation on our part I am very interested in
knowing whether any aspects of this problem are known or have been seen
before. Also, any insight or suggestions are welcome.

HM
Henry Markov
2010-06-09 18:00:10 UTC
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Raw Message
Two references to "TCP" in my description should have been "IP." I
corrected that error below.
Post by Henry Markov
One XP/SP2 machine in our private network of about 85 identical machines
occasionally is the source of a NetBios name query message that has a bad
IP checksum as indicated by a WireShark trace. In the case we most
closely investigated the high order octet of the source IP address got a
bit flipped so that 192 became 196. This produced an IP checksum error
but not a UDP checksum error. Immediately upon broadcast of this errored
packet all networking to all machines on the network except for the source
machine was permanently disabled however switches and a non-MS system on
the network remained intact. Networking could only be restored by
rebooting all machines.
I used Wireshark to capture a good name query message and then I corrupted
it in the same way that it had been corrupted in production. I used the
ColaSoft Packet Player to play this message back into a switch and all MS
XP hosts had their networking disabled exactly as in the production
scenario.
The machines use XP-Embedded and are headless, etc. so visibility into
these machines is limited and we need to enhance that. Note that
XP-Embedded uses the same OS code as desktop XP so I assume we are dealing
with a generic XP issue. Pending more investigation on our part I am very
interested in knowing whether any aspects of this problem are known or
have been seen before. Also, any insight or suggestions are welcome.
HM
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