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

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.