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

[Osier Yang]

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.

>
> And/or this
>
>     virNetworkGetDHCPLeaseForMAC(virNetworkPtr network,
>                                  unsigned char *macaddr,
>                                  virNetworkDHCPLeasePtr lease);
>
> and a corresponding  'virsh net-dhcp-leases <netname>' command
>
> Daniel