[cifs-protocol] [REG: 110120160951867] Requesting clarification of CIFS client timeout behavior

Christopher R. Hertel crh at samba.org
Wed Dec 1 13:44:44 MST 2010

Jeff Layton wrote:
> Yes, this is probably stretching the definition of protocol
> clarification, but I figured it wouldn't hurt to ask... :)

Not at all.

Keep in mind that I worked with Microsoft to get these docs out, so I know
how important such details are to them, as well as third party implementers.

The interesting thing about your questions is that they touch on very
obscure boundaries between old LANMAN behavior, NT behavior, Windows
behavior, and actual protocol.  Perfect storm.  I love this stuff.

The more I think about it, the more I believe that the Echo is sent to
determine whether the physical connection is still up.  If it's not, then
there is no sense in sending an SMB_COM_NT_CANCEL anyway, since the other
end would likely never receive it.

As I mentioned, NT and OS/2 were able to support a single logical SMB
Session over multiple connections (think of a client with three dial-up
modems connection to a server with three or more modems).  I think that the
idea was to use the Echo to test a specific link, and shut down the
connection bound to that link if it was down.

The client closes the entire session only if the server is non-responsive.

...but that's guess-work based upon my memory.  The real answer is in the
Windows source and I don't have access to that any more (thank goodness!).

Chris -)-----

"Implementing CIFS - the Common Internet FileSystem" ISBN: 013047116X
Samba Team -- http://www.samba.org/     -)-----   Christopher R. Hertel
jCIFS Team -- http://jcifs.samba.org/   -)-----   ubiqx development, uninq.
ubiqx Team -- http://www.ubiqx.org/     -)-----   crh at ubiqx.mn.org
OnLineBook -- http://ubiqx.org/cifs/    -)-----   crh at ubiqx.org

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