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

[Daniel P. Berrange]

On Thu, Jul 25, 2013 at 06:43:00PM +0800, Osier Yang wrote:
> On 25/07/13 17:35, Daniel P. Berrange wrote:
> >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);
> 
> i'm wondering if it should be more than just the lease file path, e.g.
> also the $net.conf, $net-radvd.conf, etc, though they are useless
> now, but may be useful in future, i.e. to have a more general api
> than this one.  and in that case, it should return an array of typed
> parameter instead.

We've already discussed this in the context of the virDomain API for
getting IP addresses & decided that virTypedParameter was not appropriate
there & we'd use a struct. The same arguments apply here IMHO.

Daniel
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