#!/bin/bash

# Copyright (c) 2003 Ole Craig <olc@cs.umass.edu>, all rights
# reserved. This software may be freely redistributed under the terms
# of the GNU general public license. See (e.g.)
# http://www.gnu.org/licenses/gpl.txt for details. Although it is not
# required by the license terms, if you improve this script in any way
# the author would deeply appreciate seeing (and perhaps learning
# from) your changes.

# we use this script because regular nameif doesn't handle the case
# where we want to rename preexisting devices (e.g. swap eth0 <-->
# eth1) and sometimes segfaults anyway.

ME=`basename $0`
dashs=""

# we get our parameters from /etc/mactab unless otherwise specified
CONFFILE=/etc/mactab

function usage() {
    echo "usage: $ME [-c configurationfile] [-s] {ifname macaddress}"
    exit -1
}

function loggit() {
    if [ "$dashs" == "" ]; then
	echo ${ME}[$$]: $*
    else
	logger -i -t $ME $*
    fi
}

function die() {
    loggit $*
    exit -1
}
function namer() {
# this is where we do the work on a given IF
# expect 2 inputs: current name targetname
    err=`ip link set $1 name $2`
    status=$?
    if [ "$err" != "" ]; then 
	$logger $err
    fi
    return $status
}

function isup() {
    # check to see if interface is active
    ip link show $1 2>&1 | cut -f3 -d" " | grep -qw UP
    return $?
}

# main body
if [ ${#*} -gt 0 ]; then
    while [ ${#*} -gt 0 ]; do 
	case $1 in 
	    -s)
	    dashs="-s"
	    shift
	    ;;
	    -c)
		if [ "$2" == "" -o ! -r $2 ]; then
		    usage
		else
		    CONFFILE=$2
		    shift
		    shift
		fi
		;;
	    *)
# we assume anything else is an interface name
		if [ "$2" == "" -o "$3" != "" ]; then
		    usage
		else 
		    DES_IFNAME=$1
		    # attempt to sanitize input a bit
		    DES_MAC=`echo $2 | tr 'a-f-' 'A-F:'`
		    shift
		    shift
		fi


	esac
    done
    
    i=0 
    BLOCKED=0
fi
if [ "$DES_IFNAME" = "" ]; then
    if [ ! -r $CONFFILE ]; then
	die "can't read from $CONFFILE"
    fi

# if we're processing a table (/etc/mactab by default) then we iterate
# through...
    itab=0
    for q in `cat $CONFFILE | sed 's/#.*$//g'`; do 
	MACTABLE[$itab]=$q
	let itab++
    done
    
# ...and recurse
    for (( q=0 ; $q < $itab ; q++)); do
	$0 ${dashs} ${MACTABLE[((q++))]} ${MACTABLE[$q]}
# note nasty increment of counter within loop. Ugh.
    done
else # we were given an argument, use it
    
# Build table of current IFs and their associated MAC addresses. While
# we're at it, grab current values for IF name and IF/MAC of blocking
# name, if any.  If we only have one MAC address as input, then we
# scan the table of available IFs for a match. If that MAC is
# currently in use by another IF name, we swap. Otherwise, we just
# name it. (Or leave it alone, as may be the case.)
    
# DES_IFNAME is the desired name for the mac address supplied on commandline.
    
    i=0
    GETMAC=0
    for q in `ifconfig -a | grep -E ^eth\|^wlan | awk '{ print $1" "$5 }'`; do
	MACDESK[$i]=$q
	if [ "$GETMAC" != "0" ]; then
	    CUR_MAC=$q
	    GETMAC=0
	fi
	if [ "$q" == "$DES_MAC" ]; then
	    CUR_IFNAME=${MACDESK[$i-1]}
	fi
	if [ "$q" == "$DES_IFNAME" ]; then
	    BLOCKED=1
	    GETMAC=1
	fi
	let i++
    done
    
# CUR_IFNAME is the current name for the mac address supplied on commandline.
# if $CUR_IFNAME is empty at this point, then we don't have an
# interface with this MAC address

if [ "$CUR_IFNAME" == "" ]; then
    die "no interface found with requested MAC address \"$DES_MAC\""
fi

# swap "blocked" names
    isup $DES_IFNAME && die "$DES_IFNAME ($CUR_MAC) already active"
    isup $CUR_IFNAME && die "$CUR_IFNAME ($DES_MAC) already active"
    if [ "$CUR_IFNAME" == "$DES_IFNAME" ]; then
	exit 0 # everything's jake, current and desired IF names are the same
    fi
    if [ $BLOCKED == 1 ]; then
	namer $DES_IFNAME nameif_tmp$DES_IFNAME
	namer $CUR_IFNAME $DES_IFNAME
	namer nameif_tmp$DES_IFNAME $CUR_IFNAME
    else
	namer $CUR_IFNAME $DES_IFNAME
    fi
    
fi