[et-mgmt-tools] [PATCH] Strengthen port number validation

[Daniel P. Berrange]

On Wed, Nov 07, 2007 at 04:44:29PM -0500, Cole Robinson wrote:
> Masayuki Sunou wrote:
> > Hi
> > 
> > Installation fails when port number used by other processes is set 
> > to --vncport of virt-install, because graphical console is not displayed.
> > The same problem occurs when port number exceeds upper bound. 
> > 
> > One of patches fixes to request re-input when port number used is set.
> >  --> check_vncport_used.patch
> > Other fixes to output error message when port number exceeds upper bound. 
> >  --> check_vncport_upperbound.patch
> > 
> > Signed-off-by: Masayuki Sunou <fj1826dm at aa.jp.fujitsu.com>
> > 
> > Thanks,
> > Masayuki Sunou.
> 
> 
> Hi,
> 
> The upperbound check looks good, I just applied it.
> 
> The vncport collision detection though I'm a bit worried about. Parsing
> 'netstat' doesn't seem like a nice solution: its a lot of output to parse
> for little gain and requires an external utility to do it.
> 
> I think the nice way to check the port would be to have a function that
> actually attempts to bind the port, to test that it is empty. You would
> understandably have to release it if you succeeded so the install can use
> it in the future. I'm not sure if this would carry any residual effects,
> maybe someone else has a better idea?

This kind of check does not belong in virt-install.  It is not merely a
problem when installing the guest. If you allocate a fixed port to a guest
it can clash any time you start the guest. The *ONLY* viable place to 
check & report errors for this is the code which actually opens the port
ie QEMU itself.  QEMU can propagate errors back to XenD / libvirt and in
turn back to the user.


Dan.
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