[Spice-devel] Spice agent for XSpice

[Alon Levy]

> Hi,
> 
> On 03/09/2012 11:57 AM, Alon Levy wrote:
> > On Fri, Mar 09, 2012 at 10:46:50AM +0100, Hans de Goede wrote:
> >> Hi Eike, Alon,
> >>
> >> On 03/08/2012 08:33 PM, Eike Hein wrote:
> >>>
> >>> Hi,
> >>>
> >>> I recently sent a mail to Marc-André Lureau, inquiring about
> >>> clipboard sharing support in his virt-viewer builds for Win-
> >>> dows. It turned out that the reason clipboard sharing doesn't
> >>> work is because Xspice does not yet spawn an agent.
> >>>
> >>> Marc-André subsequently got Alon Levy into the discussion,
> >>> who had this to say on how this might be pulled off:
> >>>
> >>> "I'm really glad to hear someone is actually using this. To implement
> >>> clipboard sharing is indeed just an Xspice issue. You'll need to have an
> >>> agent talking to spice server not via a virtio device and qemu. Looking
> >>> at vdagent-linux I guess there are a few questions:
> >>> * do we run vdagentd and vdagent as subprocesses of Xspice
> >>> (actually Xorg)
> >>> * is there a way to emulate uinput (not related to clipboard)
> >>> * more a statement - I think the clipboard part is relatively easy,
> >>> you can replace the hardcoded /dev path for the virtio-serial port
> >>> with a pipe.
> >>>
> >>> I guess I would try to split vdagent to a library and app, and then link
> >>> the library into spiceqxl_drv.so (i.e. xf86-video-qxl)."
> >>>
> >>> I'm still pretty keen on getting this to work in my Xspice-
> >>> based setup, and since I was encouraged to bring this topic
> >>> to the list here goes. Please chime in :).
> >>
> >> Eike, in case you don't know, I'm the main author of the Linux
> >> spice-vdagent. I've been thinking a bit about re-using that
> >> for Xspice (after Alon asked me this a couple of days ago) and
> >> here is my 2 cents:
> >>
> >> The linux agent consists of 2 parts, a system level daemon and
> >> a per user (X) session agent process.
> >>
> >> The system level daemon (spice-vdagentd):
> >> -talks to the agent virtio serial port
> >> -handles client mouse mode through uinput
> >> -dispatches other messages to session process for the
> >>   currently active session (it uses consolekit to find out
> >>   which is the currently active session, think fast
> >>   user switching and having multiple X-session open
> >>   on different VTs)
> >>
> >> The user session process (spice-vdagent):
> >> -sends the resolution X is currently running at to
> >>   spice-vdagentd, which needs this info to interpret
> >>   the mouse events it gets from the client and feeds to
> >>   the uinput device
> >> -receives the desired (client native) resolution from the
> >>   client, and uses Xrandr to switch to this
> >> -handles copy and paste
> >>
> >> If we want to re-use this all for X-spice, then the choosen
> >> split actually comes in quite handy, with X-spice we don't
> >> have a agent virtio serial port, and we don't need to send
> >> mouse event through a uinput device either. So I suggest that
> >> for X-spice we simply re-use the user session agent process
> >> as is (making it connect to the running X-spice server), and
> >> "throw away" the system level daemon, replacing it with some
> >> functionality inside X-spice.
> >>
> >> The user session agent process talks to the (to be removed
> >> in the X-spice scenario) system level agent daemon through
> >> the following unix domain socket:
> >> /var/run/spice-vdagentd/spice-vdagent-sock
> >>
> >> So I think that if we modify X-spice to register a chardev
> >> with spice-server for the agent channel, and create a
> >> /var/run/spice-vdagentd/spice-vdagent-sock unix socket and
> >> forward all client agent messages between the 2 we are almost
> >> done. All that then needs to be done is filter out mouse
> >> event messages and inject those directly into the X-server.
> >>
> >> Note that the protocol on the unix socket != the protocol
> >> on the virtio serial port, so you will need to lift some code
> >> from spice-vdagentd which does the parsing of the one and
> >> wrapping of the other.
> >>
> >> Later on we should make the path of the unix domain socket
> >> a cmdline option for both X-spice and spice-vdagent so
> >> that we can run multiple X-spice sessions on the same machine,
> >> with each using there own socket.
> >>
> >> Something else to worry about later is sharing the necessary
> >> code from spice-vdagent with X-spice, for now I simply suggest
> >> copying over the necessary files.
> >>
> >
> > Sounds like a plan. My only comment was the hardcoded /var/run.. and
> > multiple servers, but you forsaw that :)
> >
> > I could start from the end part - spliting the system level daemon to a
> > library and daemon, and reusing the library for Xspice (is X-spice
> > really more readable?)
> 
> I don't think there is much in there to split into a library. The only
> re-usable part is udscs.c / udscs.h which stands for unix domain socket
> client server. Which does the low-level uds handling. Everything else
> is not really suitable for re-use (ie assumes a virtio serial port,
> rather then spice-servers chardev interface).
> 
> I think the only thing which you should copy 1 on 1 is vdagentd-proto*.h
> which defines the protocol over the unix domainsocket.h and maybe udscs.?

Hi,

 I've finally sat down to do this. It turns out in practice that incorporating udscs is not such a good idea:
1. udscs code is GPL, driver is BSD (solvable, but see the rest)
2. you get a lot of duplication with vdagentd - parsing chunks and messages, basically reading all messages, passing through some, some with changes (clipboard). (~700 lines just for monitors config + mouse + untested xfer, lacking clipboard)

 I have a working implementation but Uri suggested a simpler idea and I wanted your opinion:
1. use a named pipe provided by Xspice to vdagentd instead of virtio serial com.redhat.spice.0
2. use a named pipe / unix domain socket to implement a pseudo uinput device. pseudo since I can't implement any of the ioctls, so this will require a small change to vdagentd-uinput.c and a command line argument.

Overall the changes to vdagentd/vdagent will be small:
1. vdagent option to pick a different path to udscs UDS.
2. same for vdagentd
3. vdagentd pseudio-uinput support (same packets, no ioctls - presumed device layout, i.e. 2 axis 5 buttons 2 of which are a wheel).

Any comments?

Alon

> 
> Regards,
> 
> Hans
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