Directory Leasing feature in Samba smbd

Jeremy Allison jra at
Wed Sep 2 19:20:54 UTC 2020

On Wed, Sep 02, 2020 at 05:18:05PM +0000, Krishna Harathi wrote:
> Jeremy,
> Thanks for the insightful response on how to start on directory leasing feature.
> After reading more into Microsoft SMB2/3 directory leasing, in our customer case, looks like the windows client is taking advantage of the granted directory lease and maintaining a directory cache.
> I am attempting to setup the following even before writing test cases.
>   1. Using directory lease capable Windows Server 2012R2 (or later), setup a shared folder/directory with a set of files/folders in it.
>   2. On a Windows client capable of using directory lease , map the shared folder to a local drive letter. 
>   3.  Start capturing tcpip packets on either client or server.
>   4. Browse the shared folder on the client multiple times. 
>   5. The tcpip dump should show only a single directory scan set (SMB2_FIND_BOTH_DIRECTORY_INFO requests/responses)
> Is my assumption and approach correct? Is there a better/direct way to monitor the directory lease and cache in the client? 
> Only information I found on Windows is the global configuration values of "DirectoryCacheEntriesMax" and "DirectoryCacheEntrySizeMax" shown with powershell "get-smbclientconfiguration". Are there any stats to monitor to determine that the directory cache is active with entries from the mapped drive that has the directory leased?
> Once this setup is done and confirmed working, I will have a better understanding on what to expect and I will start adding test cases to smb torture.

Hi Krishna,

That would seem to be a good way to explore
how the Windows client behaves. I don't have
good insights into how the Windows client
manages its cache I'm afraid.

One thing I'd also try is to get wireshark
logs whilst browsing the cached directory
and then using the local Windows command
line on the server, create a file in the
cached directory - that way you should
be able to see lease revokation going on.

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