Silly reads from WinXP/OfficeXP against Samba 3.0

Christopher R. Hertel crh at
Tue Jul 15 16:55:56 GMT 2003

Does the same happen against an NT or W2K server?

We've seen similar (not the same) behavior in other cases.  There's
"rabbit-pellet" mode, in which Windows Explorer on a W/98 or ME client
will do short writes (512 bytes), each followed by a flush operation.  It
is still not clear what triggers this.

I can send you a capture if you'd like to see it.

The problem with rabbit-pellet mode is that no one has ever seen Windows 
systems do this to one another.  It only happens against a third-party 
server (Samba, generally, but it may happen against others...dunno).
It *seems* as though rabbit-pellet mode is triggered by pass-through 
authentication on the server, but it is not consistent.  There may also be 
timing issues involved.

So, the thing to figure out first is whether or not XP does the same thing 
against other servers.  If so, we may be able to get Microsoft to fix the 
bug that causes it.  If it only happens against Samba, then we need to 
figure out what we are doing that is "different".

As with much of Microsoft's code, it is likely that we're just causing 
Windows to wander down some untested code path.  These are probably bugs 
that have never been tested because none of Microsoft's products exercise 
them.  I doubt that this behavior is intentional.

Chris -)-----

On Tue, Jul 15, 2003 at 04:27:48PM +0200, Volker Lendecke wrote:
> Hi!
> Here I have a repeatable case: Office XP SP2 on WinXP reads a file, and
> during the first requests everything looks fine. Then after some time
> the machine starts to read *HUGE* amounts of 512 byte-fragments from the
> .doc-file. This results in ~140000 packets whereas the same operations
> only use ~4000 packets when the file is on 2k.
> I already tried 'max xmit = 4356' to match 2k buffer size negotiation,
> but that did not help. One thing that I also found is that the client
> seems to actively use the multi-request feature of 2k.
> I can provide sniffs and tests with a patched Samba, but I'm currently a
> bit lost. Staring at a dump of 140000 packets is not exactly easy :-(
> Any idea anybody?
> Volker

"Implementing CIFS - the Common Internet FileSystem" ISBN: 013047116X
Samba Team --     -)-----   Christopher R. Hertel
jCIFS Team --   -)-----   ubiqx development, uninq.
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