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List:       ms-cifs
Subject:    smb_vc_num
From:       Steven French <Steven_French () AUSSMTP ! AUSTIN ! IBM ! COM>
Date:       1996-11-01 0:14:01
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>>It looks like using the smb_vc_num parameter in the sesssetupandX smb allows
>>for multple sessions for the same user over the same netbios session. Is
>>this the intended function of this parameter ?

No. The reverse was the intent for vc_num.   Multiple netbios sessions
associated with one UID (SMB Session)
were envisioned as a performance enhancement.    This would have allowed "raw"
SMB
(SMBReadRaw & SMBWriteRaw) operations
on the second distinct netbios session and all other SMBs on the first netbios
session.  This would
avoid having to "lock" the netbios sessions used for standard SMBreadX and all
other SMBs such as
SMBOpenX, SMBTransact etc. just because a high performance operation like
SMBReadRaw was in
progress.    smb_vc_num in the SMBSessSetupX request has an interesting and
very important sideeffect though -
when smb_vc_num is 0, many servers assume that a second request from a client
(same workstation name) that already has a netbios (or netbios-over-tcp)
session with this SMB server is an error condition that requires closing the
first netbios session (which presumably was accidently left active due to a
bug).   Unfortunately in the new
world of CIFS this is probably a bad assumption.

"Multiuser" is already used by some current redirectors for some special
cases.    For example, for OS/2 remote boot (RIPL) you will see exactly two
UIDs (one for the "machine" and one for the "user") on the same netbios
or Netbios-Over-TCP session.     A quite different case, AS/400, implements an
SMB multiuser redirector.   I
do not believe that all AS/400 users share the same netbios session to the same
server though.



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