Re: [libvirt] Looking for good example API function(s)
On 03/11/2009 09:55 AM, Daniel P. Berrange wrote:
- Application connects to libvirt (virConnectOpen()
- in src/libvirt.c we activate a hypervisor driver based on the
URI given. If successful, we then try to activate a number of
secondary drivers (eg virtual network, storage, node device)
- in src/libvirt.c, virConenctPtr is populted with callbacks for
each of the activated drivers
Now....
- Application calls virNetworkCreateXML()
- in src/libvirt.c, this runs virNetworkCreateXML code
- this uses the networkDriver callback sets, invoking
the networkCreateXML() callback, eg
conn->networkDriver->networkCreateXML()
For something like the network driver, in the application process
the driver that's activated will be the generic remote driver.
- So, networkCreateXML() is pointing to remoteNetworkCreateXML()
in src/remote_driver.c
- remoteNetworkCreateXML() now serializes the parameters into
XDR format, and makes an RPC call REMOTE_PROC_NETWORK_CREATE_XML
I had figured out everything up to here with no problems...
The RPC calls are handling by the libvirtd daemon.
- libvirtd gets REMOTE_PROC_NETWORK_CREATE_XML and dispatches
it to remoteDispatchNetworkCreateXML() in qemud/remote.c
This is where I got stuck. As DV says, the dispatch table is generated,
and doesn't reference the enum value directly (it's just implied via the
index into the table). Also, the name of the remoteDispatchxxx function
is generated, and the way that it's generated causes "XML" to be
"Xml".
Anyway, thanks to both of you for filling in the missing links. I think
I understand how it works now!
- libvirtd itself uses libvirt.so, so it once against calls
into the public API virNetworkCreateXML() as the application
did much earlier.
- in src/libvirt.c, this runs virNetworkCreateXML code
- this uses the networkDriver callback sets, invoking
the networkCreateXML() callback, eg
conn->networkDriver->networkCreateXML()
When run inside libvirtd though, libvirt.so does not activate
the 'remote' driver. Instead it activates the real driver,
in this case provided by src/network_driver.c
- So, networkCreateXML() is pointing to networkCreate()
in src/network_driver.c
- networkCreate() finally does whatever interesting stuff
needs to be done to complete the operation.
Summarizing
app -> libvirt.so -> remote driver -> XDR ->...
... TCP socket ...
... XDR -> libvirtd -> libvirt.so -> network driver
Daniel