Re: [libvirt] RFC: Implement virDomainGetIPAddress()

On Thu, Jul 14, 2011 at 05:14:57PM +0200, Michal Novotny wrote: > Hi guys, > some time ago I've been investigating the options to get the guest's IP > address information without having to connect to guest's VNC window or > console. It was for one project I've been working on and I found that > the solution lies in the procfs, precisely in the /proc/{PID}/net/arp... > > The format is as follows: > > $ cat /proc/{PID}/net/arp > IP address HW type Flags HW address Mask > Device > 192.168.122.36 0x1 0x2 52:54:00:35:76:e6 * > virbr0 > > where the HW address matches the MAC address associated to the guest's > NIC. Implementing such an API shouldn't be a big problem however I know > that there's some option to run libvirt on Windows machines. It should > be just the client so it shouldn't really matter however I'd like to ask > you whether it's really not an issue. > > The function should return a string of the guest's IP address as read > from the procfs or return a NULL value if there's no IP address > associated with the guest. > > If the multiple NICs are being used by the guest then the function > should return either the IP address matching the MAC address passed to > the function or the first IP address if omitted. > > The prototype should be: > > char *virDomainGetIPAddress(virDomainPtr domain, char *devmac); > > For this the internal information about PID of the process spawned > should be used (this is already being tracked and stored by libvirt > IMHO) to access the /proc/{PID}/net/arp file. > > This API function would be very useful since it would give libvirt users > option to get the information of the guest's IP address without having > to connect to guest's VNC window or console. > > For virsh this could be implemented directly into the dominfo subcommand. > > What do you think about implementing this ? I'm not entirely convinced was want to have this in our APIs, since the arp probing is not really a reliable basis for reporting guest IP details. In the near future there will be guest agents for QEMU which can report this information reliably and I think they're a better bet for any app which would want this information. Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|