Libvirt APIs for creating virtual networks

[Santhosh Kumar Gunturu]

Does the libvirt has any capabilities to get the statistics of DHCP server
? How many packets received/sent ?
Is there a way to get those statistics if the APIs are not available ?

Thanks & Regards
Santhosh Kumar Gunturu


On Thu, Apr 30, 2020 at 1:45 PM Laine Stump <laine at redhat.com> wrote:

> On 4/28/20 12:01 PM, Daniel P. Berrangé wrote:
> > On Tue, Apr 28, 2020 at 08:51:45AM -0700, Santhosh Kumar Gunturu wrote:
> >> Okay. Thanks.
> >>
> >> Do we have any facility APIs to set the DHCP Options via XML ?
> >> Default gateway ?
>
> libvirt has no supported method of specifying a default gateway other
> than the IP of the bridge device on the virtualization host it self, and
> DHCP clients on these networks will always end up getting their default
> gateway set to the IP address of that bridge. Fortunately (for you :-)
> that's not because libvirt is explicitly setting that address in the
> dnsmasq config file, but just because that's what dnsmasq does when no
> gateway address is specified in the config file.
>
> You would set this in the dnsmasq.conf file with dhcp-option, e.g.:
>
>    dhcp-option=option-router,192.168.122.5
>
> and recent libvirt (5.6.0 and newer) allows adding arbitrary lines to
> the dnsmasq.conf files it creates for its networks, using the
> <dnsmasq:options> element in the network XML. For details on how to do
> this, look at:
>
>    https://libvirt.org/formatnetwork.html#elementsNamespaces
>
>
>
> >> Dns-server ?
>
> Not exact, but
>
> <forwarder addr='8.8.8.8'/>
>
> is *kind of* what you're looking for. It doesn't set the IP address sent
> back in the dhcp reply, but sets up the dnsmasq instance listening for
> the network to forward all requests on to 8.8.8.8 (you can also refine
> this to forward the requests for only certain domains, by adding
> "domain='example.com'" to the <forwarder> element).
>
> (If you *really* need to have the guest send DNS requests directly to
> the upstream DNS server rather than via dnsmasq, then you would need to
> use <dnsmasq:options> to set something like
> "dhcp-option=option-dns-server,8/8/8/8")
>
> >> domain-name ?
>
> domain can be set with "<domain name='example.com'/>".
>
>
> >
> > Everything is controlled through the XML document described here:
> >
> >     https://libvirt.org/formatnetwork.html
> >
> > We don't have separate APIs for each piece of info - just the one
> > virNetworkDefineXML API that takes the XML document.
> >
> > Regards,
> > Daniel
> >
>
>
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