[linux-cifs-client] Re: CIFS not mounting Windows Shares (Adnan)

[Steven French]

> Question of curosity.......
>
> Does CIFS works with NETBIOS only??

The Linux CIFS VFS client only works over TCP/IP.   None of the Linux 
clients/servers, and few of the Unix ones support Netbios.  Some detail.

CIFS is the newest of the dialects of the SMB (server message block) 
network filesystem protocol, and can be sent via different transport 
protocols.   Today it is most common for CIFS protocol frames to be sent 
via TCP especially when sent from Linux (smbfs and cifs client) or to 
Samba server (and also when sent from the other common clients JCIFS 
(Java) and Apple's MacOS client) since that is really the only choice 
(there is not a commonly available Netbios device driver for Linux).

In the past (pre-1999 especially) the Netbios Frames Protocol instead of 
TCP/IP (in particular for the IBM and Microsoft DOS clients and for OS/2 
and for Windows 9x and NT) would often be used.   There were cases in 
which earlier clients could be configured to send via IPX.

But even using TCP/IP there are two ways to locate the server, although 
subsequent SMB/CIFS traffic (after connecting to the server is the same in 
both)
1) via TCP hostname or IPv4 address (the most common today)
2) via RFC1001/1002 (often called WINS) which maps 16 byte Netbios names 
to ip addresses, and requires an RFC 1001 session request frame to precede 
the first SMB/CIFS frame

The transport choices for SMB/CIFS are:

1) CIFS over Netbios frames protocol (mostly Windows and OS/2 only)
2) CIFS over "Netbios over IPX" (not common anymore), and "Netbios over 
APPC" (never very common)
3) CIFS over TCP/IP
        a) with Netbios naming (uses RFC1001 session and name service, and 
is somewhat inaccurately called "Netbios over TCP/IP")
        b) with TCP naming (relies on a very small part of the RFC1001 
session service, the definition of the frame length)

More investigation is needed to see for 3b (CIFS over TCP) which clients 
and servers transparently could handle ipv6 addresses (the CIFS VFS for 
Linux support for this is almost complete as a client, but additional 
minor changes will be needed in the mount.cifs mount helper), not just 
ipv4 addresses.

Steve French
Senior Software Engineer
Linux Technology Center - IBM Austin
phone: 512-838-2294
email: sfrench at-sign us dot ibm dot com
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