[libvirt] [PATCH] Expose SLIRP attributes

[Richard W.M. Jones]

On Fri, Mar 28, 2014 at 12:16:43PM +0200, Laine Stump wrote:
> On 03/28/2014 10:47 AM, Richard W.M. Jones wrote:
> > On Fri, Mar 28, 2014 at 10:33:39AM +0200, Laine Stump wrote:
> >> Beyond that, a question not with your patch, but with qemu's
> >> implemenation - does it always assume that the gateway address is
> >> $network.1 ?
> > Actually network.2.  The default addresses are:
> >
> >                            network: 10.0.2.0/24 (ie. mask 255.255.255.0)
> >                    default gateway: 10.0.2.2
> >                         dns server: 10.0.2.3
> >  dhcp start / normal guest address: 10.0.2.15
> >
> > It _is_ possible to change the gateway address, by specifying the
> > (confusingly named) 'host=' parameter.  As you suggested I think this
> > could be mapped to a gateway XML attribute, although libguestfs would
> > not need to use it.
> 
> Ah, good. I didn't see that in the parameters that I found (why is my
> first reaction now to do a google search instead of looking at the man
> page? What is wrong with me?? :-P).
> 
> In that case, I think that the XML should be
> 
>   <ip address='guest's IP address' prefix='prefix for network'
>       gateway='host IP address according to guest'
>       dns='DNS server IP given in DHCP response (and answering requests)'/>
> 
> I think that
> 
> * address should be mandatory

I don't understand why this should be mandatory.  Actually I don't
think any of them should be mandatory (the same as qemu), but the only
one which libguestfs would specify is the network.  The guest can
choose any IP address on the network >= .5 and things will work.  The
libguestfs appliance arbitrarily uses .10 since DHCP would be too
slow.

> * prefix should default to the natural prefix for that particular
> address (we have a function somewhere in the network conf or driver code
> that already does this)

Right, qemu does this if you don't specify it on the command line.

> * gateway should default to
> 
>       address & ~(0xffffffff<<(32-prefix)) + 1

qemu will choose .2 unless specified.

[...]

For libguestfs we only care about setting the network address + prefix,
and to fix this bug I'm quite happy for the patch to only do that, and
we can worry about the other things another time.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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