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

[Osier Yang]

On 25/07/13 19:13, Daniel P. Berrange wrote:
> On Thu, Jul 25, 2013 at 07:01:05PM +0800, Osier Yang wrote:
>> 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.
> No, file paths will absolutely never be exposed outside of the bridge
> driver. The API I suggest above are about exposing the IP address + MAC
> address of current leases. ie the actual data the user needs, *not* the
> file path containing the data which is a private impl detail.
>
oh, i see, agreed with the idea then.

osier