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

[Osier Yang]

On 25/07/13 18:53, Daniel P. Berrange wrote:
> 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.
>
the api to get the ip addresses is more complicate than this, and we
finally chose the struct is because of the multiple level information
is hard to constuct with typed parameter, but for this api, it's different,
as it just needs to return the file paths.

osier