[libvirt] RFC: Introduce API to return configuration/state paths of the network driver

[Daniel P. Berrange]

On Thu, Jul 25, 2013 at 02:02:36PM +0530, Nehal J. Wani wrote:
> Currently, there is no API which returns configuration/state paths of the
> network driver.
> Although it is a private implementation of the network driver, I don't see
> any harm in
> making the locations public because although the locations might change,
> there will always
> be a location for these files. There is a need for this API to implement
> method 2 of the
> "API to query ip addresses of a given domain", refer:
> http://www.mail-archive.com/libvir-list@redhat.com/msg79793.html . It is
> required to parse
> the leases file generated by dnsmasq. So, this API will be used by the qemu
> driver, but it
> can also be made public, so that, if a user wants to know get some
> information from a
> configuration file, he can get the location from libvirt and analyze it on
> his own. Right now,
> there is an alternate way to get the info: by using
> networkDnsmasqLeaseFileNameDefault,
> defined in /src/network/bridge_driver.c Since this function is static, it
> is part of the private
> implementation and not visible outside. To make it public, the following
> hack is possible:

NACK,

As I explained on IRC, the hypervisor drivers have no business accessing
the dnsmasq lease files from the bridge driver. This is considered to be
a private implementation detail.

At a conceptual level, what you're after here is a list of all the IP,
mac address mappings of the virtual network. This information is useful
even outside the context of the hypervisor driver method you're working
on. So we should create formal APIs for exposing this, something like:

   virNetworkGetDHCPLeases(virNetworkPtr network,
                           virNetworkDHCPLeasePtr *leases,
                           unsigned int nleases);

And/or this

   virNetworkGetDHCPLeaseForMAC(virNetworkPtr network,
                                unsigned char *macaddr,
                                virNetworkDHCPLeasePtr lease);

and a corresponding  'virsh net-dhcp-leases <netname>' command

Daniel
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