[BUG] libxenstore and xentop confused by renamed VIF interfaces

[Jacek Konieczny <jajcus@jajcus.net>]

Hi,

I have noticed a strange behaviour on 'xl top' – it would show no
network statistics for some of my domU. It turned out that 'xl top'
shows no network ('NETS', 'NETTX(k)', 'NETRX(k)' all '0') when the
domU VIF has been renamed by using the 'vifname' option in its xl.cfg
file.

The 'vifname' option is very useful to have predictable interface names
for firewall configuration or network monitoring. The problem is
libxenstore under Linux parses /proc/net/dev to extract 'vif.${domid}.*'
interfaces, which won't be there, when the interfaces have been renamed.

I think the solution would be to look-up the actual interface name or
index in sysfs, e.g. under /sys/devices/vif-${domind}-*.

Greets,
	Jacek