[Ovirt-devel] Re: [PATCH server] allow admin to setup iptables port forwarding on server for a vm's vnc port

[Daniel P. Berrange]

On Mon, Feb 02, 2009 at 11:00:30PM +0000, David Lutterkort wrote:
> On Mon, 2009-02-02 at 17:48 -0500, Mohammed Morsi wrote:
> > David Lutterkort wrote:
> > > On Wed, 2009-01-28 at 20:16 -0500, Mohammed Morsi wrote:
> > >
> > > To address the race condition, the simplest solution is to take an
> > > exclusive table lock on the vms table (before listing the assigned vnc
> > > ports !) and hold that until the vm is saved in the DB, i.e. the end of
> > > the current transaction.
> > >
> > >   
> > This is not done as I'm a little concerned about locking the table (what
> > if the user doesn't submit the form and walks away, will it stay
> > locked?).
> 
> I must have misunderstood the logic: I thought the port-assignment logic
> was happening as part of saving the VM, not when the form is presented
> to the user.

I rather think both options are wrong. Automatic port assignment should
be just done when starting a VM, so you don't have to reserve a tonne
of ports for inactive VMs.

> >  I changed the additions to the server such that the
> > autogenerated port isn't displayed in the form, eg the user is prompted
> > to set the port or leave it at '0' after which the server will
> > autogenerate it immediately before saving.
> 
> Yes, that's the flow that makes sense.

Does the user really need the ability to choose a specific port ? If there
is a non-trivial number of VMs, any port they might wish to reserve for
their own VM is probably already taken by another. With the ovirt-viewer
client app, they should never need to know what port is used for a VM,
since ovirt-viewer will automatically lookup the port for them.

Daniel
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