[cifs-protocol] SMB3 LockSequence

Stefan Metzmacher metze at samba.org
Wed Oct 2 14:18:31 UTC 2019

Hi Edgar,

we discussed the topic in Redmond...

Even Windows Server 2019 only implements lock sequence checking only
for resilient and persistent handles as a server.
While its client side uses lock sequence checking if it negotiated
multichannel with the server.

 [MS-SMB2] Receiving an SMB2 LOCK Request


 If the LockSequence value in the SMB2 LOCK Request (section 2.2.26) is
 not zero, and either one of the following conditions is TRUE, the
 server SHOULD verify whether the lock/unlock request with that
 LockSequence value has been successfully processed before:
 * Connection.Dialect is "2.1" and Open.IsResilient is TRUE.
 * Connection.Dialect belongs to the SMB 3.x dialect family.<318>


 <318> Section Windows 8, Windows Server 2012, Windows 8.1,
       and Windows Server 2012 R2 do not verify the LockSequence value
       in the SMB2 LOCK Request (section 2.2.26) when both
       Open.IsResilient and Open.IsPersistent are FALSE.

Note <318> also applies to Windows Server 2016 and 2019 (any current

It would be great if the documentation can be adjusted.

But the more important question would be that the Windows Server
behavior will be changed to just use the SMB 3.x dialect to turn
the LockSequence checking on.
Would it be possible to get a commitment from Microsoft that
this will be fixed in future releases?
Backports would also be nice.


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