about "ea support" parameter

[Ralph Boehme]

Am 11/26/20 um 10:57 AM schrieb Leo Fan via samba-technical:
> Hi samba experts,
> 
> I need your help to understand the smb.conf parameter ‘ea support’. 
> We are developing a customized samba service to serve Windows 10
> clients and MAC OS clients. And, we would like to set ‘EA support =
> no’ to gain more performance of ‘dir’ command especially on the large
> directory, but as smb.conf doc says, EA support disablement will
> impact Windows file service compatibility.
> 
> The default has changed to yes in Samba release 4.9.0 and above to
> allow better Windows fileserver compatibility in a default install.

To give you some background: that change untangled the previous mixture
of configuring both SMB level behaviour *and* backend storage behaviour.
Nowadays this parameter only configures the SMB level behaviour, ie if
we support EAs in the protocol. There are various ways a client get
list, get and set EAs over SMB, by setting "ea support = no" all of
those will fail with an error, probably NT_STATUS_NOT_SUPPORTED.

However, if when setting "ea support = no" Samba will still use xattrs
in the backend as storage for various bits and pieces like DOS
attributes, creation date, ACLs and so on.

> I am not quite clear about compatibility problem with EA support
> disablement, and have some questions:
> 
> 
> 1.  In which scenarios will there be windows file service
> compatibility?

As explained above, you disable something which a Windows server
supports. Hell may brake loose or you may never notice a difference in
client behaviour, you never know.

> 2.  How do we create and use EA?

There are various SMB info level to get and set them, cf MS-FSA/MS-FSCC.

> 3.  Does any well-known Windows/MAC application use EA?

I'm not aware of any. Both make heave use of streams, but not EAs. The
macOS client maps local xattrs to SMB streams and you typically enable
on of the streams modules on the server to support streams. With
streams_xattrs the streams then again end up being stored in xattrs on
the server.

-slow

-- 
Ralph Boehme, Samba Team                https://samba.org/
Samba Developer, SerNet GmbH   https://sernet.de/en/samba/
GPG-Fingerprint   FAE2C6088A24252051C559E4AA1E9B7126399E46
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