Re: [libvirt] RFC: Implement virDomainGetIPAddress()

On 07/14/2011 05:42 PM, Matthias Bolte wrote: > 2011/7/14 Michal Novotny <minovotn(a)redhat.com&gt;: >> 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. > Windows or not is irrelevant here as the IP address lookup cannot be > implemented in a general way/place, but will have to be implemented by > the hypervisor/network drivers. > >> 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); > First of all you're missing the unsigned int flags parameter. > > Also did you consider that the MAC to IP(v4|v6) mapping isn't > necessarily a 1:1 mapping, but the signature of your function requires > this? Well, for this I considered the IPv4 address only. > I took a look at this and wonder what's the difference between > /proc/{PID}/net/arp and /proc/net/arp. Also as it's ARP it'll only > work for IPv4. Honestly I was unable to see it in /proc/net/arp. I saw just some ARP records but not related to the qemu-kvm process I tried on my Fedora-14 box but I was able to see those records in /proc/{PID}/net/arp and therefore I was looking to the /proc/{PID}/net/arp and why I mentioned this instead.