From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooper Subject: Re: Best way to get IP addresses from VMs without logging in to them? Date: Wed, 11 Jun 2014 17:49:37 +0100 Message-ID: <539888A1.6020004@citrix.com> References: <1402504732.16332.51.camel@kazak.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1402504732.16332.51.camel@kazak.uk.xensource.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Ian Campbell Cc: Russ Pavlicek , xen-devel@lists.xen.org List-Id: xen-devel@lists.xenproject.org On 11/06/14 17:38, Ian Campbell wrote: > On Wed, 2014-06-11 at 12:32 -0400, Russ Pavlicek wrote: >> I have been working on an "on-ramp" application to introduce new >> people to Xen Project (more on that later), when I ran into a simple >> scenario which seems to lack a simple solution: >> >> When I start up a new VM which employs DHCP, how can I >> programmatically determine what IP address it obtained? >> >> When I look at the Wiki, I find the following reference: >> >> http://wiki.xenproject.org/wiki/Xen_FAQ_Networking#IP_Determination >> >> Which suggests using tcpdump for sniffing out packets relating to a >> known MAC address. But that depends on traffic flow from VM, which >> could be time consuming if the machine happens to be idle. > If the machine is using DHCP then you should be able to observe the DHCP > requests and responses, which contain the IP address. I think Xenrt does > something around parsing the tcpdump output of that happening, but I'm > not sure of the details. > > Ian. I believe XenRT snoops ARP and DHCP packets from dom0 using tcpdump, but also controls the DHCP server itself. XenServer also has the guest tools package. This is a small daemon running in the guest which, amongst other things, writes /local/domain/$DOMID/attr/eth$N/ip/$DETAILS which is then consumed by monitoring tools in dom0. ~Andrew