scannedonly vfs module ported to samba 3.5

[Olivier Sessink]

Volker Lendecke wrote:
[..]
> Ok. That's up to you. I consider TCP to be vastly easier to
> use than UDP though.
> 
> I had not noticed that you are using a DGRAM socket. In that
> light, I would really say that flush_sendbuffer() needs
> fixing. How do you want to deal with packets lost between
> smbd and the virus scanner?

it does not really matter for the design:

the next time the directory is listed it is noted again that the file
has not yet been scanned, and the virus scanner is notified again.

> The local process might have
> given you the okay, but somewhere on the way to the server
> process this might get lost. Your server process might get a
> little more complex, but I really think that's worth it.
> 
> I would not block getting your module in over this, but I
> think for more heavy workloads this needs adapting.

it has been in production on two sites with 10.000 / 90.000 users with
(on average) 1000 concurrent users per samba server (ons site has a
single samba server, the other has several). Both sites have the actual
data and the virus scanning on a NFS server, and send the filenames over
UDP from samba to the NFS server. I know one case of packet loss: NFS
throughput came to a grinding halt, but the scanning was hardly affected
(very rarely a user had to press F5 to re-list a directory and thus
re-notify the scanning daemon for a file to become available).

perhaps TCP could be added in the future, but for now UDP seems to
function very well.

regards,
	Olivier