The updated version of snmpd in Debian Etch doesn't seem to like our customised vif interfaces names that we're using for Xen hosting. I'm seeing the error "ioctl 35123 returned -1" in syslog every 5 minutes. Reverting to the standard "vifx.y" format fixes the problem.
I started using xen guest names for vif interfaces to allow our graphing system (Cacti) to keep track of which interface matched a particular guest. For example a guest called acme would have an interface called acme.eth0 in the xen host instead of a dynamically generated name like vif14.0. This seemed to be working fine with Sarge, but alas not with Etch. I tried some variations like acme-eth0 and acme.0, but nothing seems to get rid of the error except vifx.y.