2011/7/15 Michal Novotny <minovotn@redhat.com>:
On 07/14/2011 05:42 PM, Matthias Bolte 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. 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
2011/7/14 Michal Novotny <minovotn@redhat.com>: 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.
Considering the fact this will be working just for IPv4 there should be some prototype like:
char *virDomainGetIPAddress(virDomainPtr domain, char *devmac, unsigned int flags);
Even if you're going to restrict it to IPv4 for now this signature won't do, as you can have multiple IPv4 addresses assigned to the same MAC address. How do you want to return multiple IP addresses? As a comma separated list as string and the caller has to parse it? -- Matthias Bolte http://photron.blogspot.com