munin-node passes the original interface name (as extracted from
/proc/net/dev) to if_* and if_err_*. Thus replacing dash with underscore
results in interfaces not being found anymore.
Source: patch "220-modify-ifname-parser" from OpenWrt
Author: Martin Blumenstingl
Changed type to DERIVE and added min values to 0. Added check for
ethtool to check if max value could be calculated
git-svn-id: svn://svn.code.sf.net/p/muninlite/code/muninlite@11 35caa317-6b62-4e8a-81c0-b04f0c356266
