Add vmlist element to nodes, when they are being used to host XEN

VMs. These are not internal nodes (vhosts) but actual nodes in the
topology to which VMs have been assigned (instantiate_on).

protogeni/lib/GeniSliver.pm.in

@@ -951,6 +951,31 @@ sub AnnotateManifest($)
     $node->NodeAttribute( "sim_imsi", \$sim_imsi );
     GeniXML::SetText( "sim_imsi", $rspec, $sim_imsi )
 	if( defined( $sim_imsi ) );
+
+    #
+    # Add Emulab extension that says which virtnodes are instantiated
+    # on this physical host.
+    #
+    if (!$node->isvirtnode() && $node->HasVirtualNodes()) {
+	my @vnodes = ();
+	if ($node->VirtualNodes(\@vnodes)) {
+	    print STDERR "Could not get virtnode list for $node\n";
+	    return undef;
+	}
+	my $vmlistref = GeniXML::FindNodesNS("n:vmlist", $rspec,
+					     $GeniXML::EMULAB_NS)->pop();
+	if (defined($vmlistref)) {
+	    $rspec->removeChild($vmlistref);
+	}
+	$vmlistref = GeniXML::AddElement("vmlist", $rspec,
+					 $GeniXML::EMULAB_NS);
+	foreach my $child (@vnodes) {
+	    my $vmref = GeniXML::AddElement("vm", $vmlistref,
+					    $GeniXML::EMULAB_NS);
+	    GeniXML::SetText("client_id", $vmref, $child->vname());
+	    GeniXML::SetText("vnode", $vmref, $child->node_id());
+	}
+    }
     
     if ($self->UpdateRspec($rspec)) {
 	print STDERR "Could not insert annotated manifest for node $self ".