#!/bin/bash

###############################################################################
#
# This script provides a version of the `ifconfig` command that expects to
# see the ethernet address associated with a particular port, and performs
# the stated actions on whichever ethernet interface has the specified
# ethernet address. All actions associated with the `ifconfig` command are
# supported, and the only change in syntax is that the port name of "eth?"
# is replaced by the associated ethernet address.
#
# If no ethernet interface is found with the specified ethernet address, 
# this script uses a return value of 1, otherwise it uses a return value
# of 0.
#
###############################################################################

function assign() {
    local HW="$1" OK=Y
    declare -i N=0

    shift 1
    while [ $OK = Y ]; do
	if ! port eth$N ; then
	    if ifconfig eth$N up 2> /dev/null ; then
		if [ "`hwaddr eth$N`" != "${HW}" ]; then
		    ifconfig eth$N down
		else
		    ifconfig eth$N "$@"
		    OK=$?
		fi
	    else
		OK=0
	    fi
	fi
	N=$N+1
    done
    return $OK
}

function hwaddr() {
    ifconfig "$1" | grep "^$1" | tr ' ' '\n' | grep '[0-9A-F]:[0-9A-F]'
}

function port() {
    ifconfig | grep ^eth | fgrep "$1" > /dev/null
}

if [ $# -gt 0 ]; then
    if assign "$@" ; then
	echo No ethernet interface with address "$1" found. >&2
	exit 1
    else
	exit 0
    fi
else
    ifconfig
    exit 0
fi