New Proxy Unix CAP

Sam Liddicott sam at
Sat Apr 19 02:44:36 GMT 2008

* Steve French wrote, On 18/04/08 23:26:
> Sam Liddicott who I think is the guy who gave the WAFS talk at SambaXP
> could give more details.

Hi James,

The historic thread is here:

- where we discussed the need to provide a means whereby two Samba
proxies could support additional operations in support of
caching/proxying/read-ahead and other beneficial WAN-optimising operations.

The conclusion was that ntioctl was the cleanest way to provide that
channel (allowing windows server based implementations through pluggable
ioctl handlers), and all that remained was to find a way to advertise
the capability.

A conversation at SambaXP with Metze, Steve, Tridge concluded that the
new "who am I" and the "extattr" operations set a good precedent for
using the unix capabilities bit and a new info level in the unix
capabilities to advertise the proxy capabilities (I think I got that
mostly right). (And a different advertisment method would be needed for
a windows implementation but Tridge knew what that was, I forget).

The actual operations and their definitions are quite fluid at the
moment but the current definitions can be had at:;f=source/librpc/idl/proxy.idl;h=f54c5ac8ecd24d01c01de64db6e5502218b0598c;hb=v4-0-vfs-proxy

You will see that currently there is defined is an extended read and
extended write operation that make use of cache and compression between
proxies to avoid sending the full read response where possible.

There are no stricter definitions or specifications and that interface
will change in the near future to include different cache-based
compression techniques; but a review of the irc comments by samjam and
the mailing list posts of Amin Azez will reveal a lot more on the
subject. The SambaXP slides ought to be up text week sometime I suppose.

It might not be something that cifs.ko will be able to benefit from in
the immediate future but Steve French pointed out that the cifs.ko
sources are a more canonical reference for many developers and the
reservation needed making across all the current samba versions anyway...

hope this helps.

> On Fri, Apr 18, 2008 at 2:53 PM, James Peach <jpeach at> wrote:
>> On Apr 18, 2008, at 9:42 AM, Steve French wrote:
>>> New cap to detect whether WAFS proxy which supports new IOCTL is the
>> server
>>  Steve,
>>  Can you please explain exactly what the extension being proposed is? From
>> the patch it seems like you want to add some ioctl level. What is the
>> protocol extension that this new capability indicates? Where is it
>> defined/documented?

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