[Bug 14521] New: CIFS mount shows only "vers=default" instead of specific SMB version

[samba-bugs@samba.org]

https://bugzilla.samba.org/show_bug.cgi?id=14521

            Bug ID: 14521
           Summary: CIFS mount shows only "vers=default" instead of
                    specific SMB version
           Product: CifsVFS
           Version: 4.x
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P5
         Component: kernel fs
          Assignee: sfrench@samba.org
          Reporter: kolAflash@kolahilft.de
        QA Contact: cifs-qa@samba.org
  Target Milestone: ---

/proc/mounts and the mount command don't show the auto negotiated version after
mounting with vers=default (or without specifying vers=).
Instead /proc/mounts just says vers=default.
Client OS: openSUSE-LEAP-15.2 with Linux-5.3

This non-public bug seems to be similar.
(I don't habe a RedHat license, so I can't see the details)
https://access.redhat.com/solutions/4592681

I was only able to reproduce with Windows Server 2012.
A Windows Server 2008 and Samba-4.6 (openSUSE-LEAP-42.3) work fine.
(e.g. /proc/mounts shows vers=3.11)


Workaround with some help from:
https://wiki.samba.org/index.php/LinuxCIFS_troubleshooting

echo 'module cifs +p' > /sys/kernel/debug/dynamic_debug/control
echo 'file fs/cifs/* +p' > /sys/kernel/debug/dynamic_debug/control
echo 7 > /proc/fs/cifs/cifsFYI
mount -t cifs ...
dmesg | grep -E 'cifs.*[123]\.[0-9]'
# -> negotiated smb3.02 dialect

So for me it's actually 3.02 what's been negotiated with Windows Server 2012.


P.S.
"man mount.cifs" may seem a little ambiguous about the vers=default behavior.
Quote:
==========
SMB protocol version. Allowed values are:
[...]
  - default - Tries to negotiate the highest SMB2+ version supported by both
the client and server.
[...]
  The default since v4.13.5 is for the client and server to negotiate
  the highest possible version greater than or equal to ``2.1``. In
  kernels prior to v4.13, the default was ``1.0``. For kernels
  between v4.13 and v4.13.5 the default is ``3.0``.
==========
The first one sound more like 2.0 <= vers < 3.0.
While the second sounds more like 2.1 <= version (without upper limit).
To me it looks like the second (2.1 <= version) is what's actually implemented
(at least with Linux-5.3 on openSUSE-LEAP-15.2).

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