[Samba] CIFS VFS: in dmesg when Linux accesses eComStation's (OS/2) FAT filesystem shares

[Jeremy Allison]

On Fri, Apr 24, 2020 at 04:31:53AM -0400, Felix Miata via samba wrote:
> Jeremy Allison via samba composed on 2020-04-23 09:24 (UTC-0700):
> >> CIFS: Attempting to mount //hostname/E
> >> Use of the less secure dialect vers=1.0 is not recommended unless required for
> >> access to very old servers
> >> CIFS VFS: Send error in QFSAttributeInfo = -95
> 
> >> /etc/fstab entry for //hostname/E:
> >> //hostname/E /smbmnt/hostname/E cifs
> >> ro,credentials=/etc/samba/hostname.cred,sec=lanman,vers=1.0,servern=HOSTNAME,domain=MYHOST,port=139,dir_mode=0555,file_mode=0664,noserverino,noauto
> >> 0 0
> 
> >> Kernel, Samba and CIFS client versions:
> >> Linux 00srv 4.12.14-lp151.28.44-default #1 SMP Fri Mar 20 18:20:20 UTC 2020
> >> (dbf1aea) x86_64 x86_64 x86_64 GNU/Linux
> >> cifs-utils-6.9-lp151.4.3.1.x86_64
> >> samba-4.9.5+git.296.3dd62eee45e-lp151.2.21.1.x86_64
> >> samba-client-4.9.5+git.296.3dd62eee45e-lp151.2.21.1.x86_64
> 
> >> What needs to be done to quiet dmesg when these file access occur? These didn't
> >> occur until some not all that recent updates to Samba/CIFS versions, maybe a year
> >> or more, I'm not sure, but ISTR once upon a time complete silence from such touches.
> 
> > Can you send in a wireshark trace of the client talking to
> > the OS/2 server ?
> 
> Haven't used Wireshark in over a decade. I hope this is what you want.
> http://fm.no-ip.com/Tmp/Linux/Samba/jra-samba04.trace.pcapng

Looking at that trace the client is doing a QPATHINFO request
(SMBtrans2 request) with level 263 - Query File All Info.

The OS/2 server doesn't support that, so the client then
drops back and does a SMB1 Query Information Request (SMB1
request 0x8, what Samba calls SMBgetattr).

This doesn't have the links or expanded time information
(it only returns one date) so the client isn't then able
to synthesize this information.

Also the client isn't caching the fact that the server
doesn't understand SMBtran2:QPATHINFO:263 and so it
keeps issuing these and doing the fallback on every
query. This will significantly damage performance.