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Re: [Qemu-devel] Feature request: integrated smb server?

From: David E . Still
Subject: Re: [Qemu-devel] Feature request: integrated smb server?
Date: Thu, 2 Sep 2004 18:20:47 -0700

On Thu, 2004-09-02 at 16:21, David E.Still wrote:
what would it take to integrate a small smb server intoqemu's
networking code?

A lot. Having implemented a NetBT stack and read a lot about SMB in a
past life, there's no such thing as a small SMB server; it's a complex
layered set of protocols. You would have to integrate Samba if you
really wanted to do this feasibly.

I kind of figured this might be the case, but I thought it wouldn't hurt to ask. :)

Curious, what is your need? As you say, most OS's can mount and expose
SMB shares. That means that the guest can already do what you want. Why
not just expose an SMB share in the guest and mount it over the network?
VmWare's integrated SMB server is one of the bits of evil in it; I've
had issues with VmWare's various services that it installs interfering
with the real thing...

My "need" is for the guest OS to be able to read/write files in a folder on the host OS. FTP can do it, but smb would be "easier" in the sense that the guest would see it as just another mounted disk.

The argument you could make for such a feature is zero setup to do. Just
start the guest, and QEMU exposes the file transfer service. The guest
doesn't know anything about it. The user doesn't have to set anything

Yes, it's largely an ease-of-use issue. I run QEMU on Mac OS X and Mandrake 10.0 (x86), but I have yet to be able to successfully configure a tun/tap network connection, which would probably allow me to use a smb share between the host and guest. I've tried on and off ever since I discovered bochs a couple of years ago, but I could never quite get it to work. User networking in QEMU is just so much easier. I'm spoiled! :)

beable to write and *install* to the host system.  I'm not suggesting

What do you mean by install? Don't installers usually have to access the

As I said, I run Mandrake 10.0 on my home computer. I haven't had any Windows partitions for years, but I still like to fire up an occassional game using using WINE (either plain or Transgaming's Cedega/WineX). I've discovered that some games will run fine, but have great difficulty with the installation process. If I can install the the SMB share by running Win98 in QEMU, then I can attempt to run the binary installation using WINE. FTP over QEMU's networking tends to be rather slow (I've done it using non-host computer on the LAN). I completely understand that software installed on a virtual machine won't completely install on the host (i.e., with registry settings, etc.).

There was a thread a little while back that discusses your suggestion.
Fabrice decided that FTP was the way to go over HTTP or SMB, since it is
simple and clients are readily available. One thing to understand is
that the last mile to the guest's disk is a tricky thing. Operating
systems tend to make the assumption that they have exclusive access to
filesystems they have mounted. So read-only access is probably the best
you can hope for without living very dangerously.

On Windows, if you really want to be able to write to the host file
system, you should probably go through SMB to do it. Then all the
authentication, arbitration, perimissions, decryption, etc. is done by
the host OS. And if you believe that, then you have to set up an SMB
client to talk to Window's SMB server anyway. So embedding an SMB server
wouldn't save any work.

Embedding an SMB server would save the need for a tun/tap connection, which, historically, has been the bane of my virtual networking existence. :P User networking in QEMU has always "just worked." (Yeah, I'm getting spoiled by my Mac. ;) )

Of course there could be simplifying assumptions I'm missing that could
take SMB out of the equation. I'm interested to hear those from

-- John.

If the cost (in this case development time) greatly outweighs the benefits (easy file sharing between guest and host), then I can certainly accept that.

- Stealth Dave

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