source: npl/kernel/initrd_scripts/root/etc/if-assign.boot

#!/bin/bash
#Syn-3 Interface assign script.

#path to configfile
#<MAC>\t<INTERFACE>
CONFIG_FILE=/mnt/if-assign.conf;


#shut all interfaces down and move them out of the way
for NET in /sys/class/net/eth*/address; do
        INTERFACE="`echo $NET|cut -f5 -d/`";
        if [ "`cat /sys/class/net/$INTERFACE/type`" == "1" ]; then
                MAC="`cat $NET`";
                ifconfig "$INTERFACE" down
                nameif "tmp_$INTERFACE" "$MAC"
        fi
done

#first, if we have a config, rename interfaces that have an explicit mac assignment
if [ -e $CONFIG_FILE ]; then
        for NET in /sys/class/net/tmp_eth*/address; do
                INTERFACE="`echo $NET|cut -f5 -d/`";
                if [ "`cat /sys/class/net/$INTERFACE/type`" == "1" ]; then
                        MAC="`cat $NET`";
                        NEW_INTERFACE="`grep -i "^$MAC" $CONFIG_FILE |head -1|cut -f2`"  2>/dev/null
                        if [ "$NEW_INTERFACE" ]; then
                                echo "Assigning known adaptor $MAC to interface $NEW_INTERFACE."
                                nameif "$NEW_INTERFACE" "$MAC"
                        fi
                fi
        done
fi

#now rename the unknown adapters in ORDER of macadres.
#this will guarantee consistency. in some complex setups, interfaces seem to be assigned at random/detection speed.
#after booting this assignment will be stored permanently and can be changed by the user.
IF_COUNTER=0
for MAC in `cat /sys/class/net/tmp_eth*/address 2>/dev/null|sort`; do
        NET=`grep -l $MAC /sys/class/net/tmp_eth*/address 2>/dev/null`
        INTERFACE="`echo $NET|cut -f5 -d/`";

        #determine next available eth number
        while true; do
                NEW_INTERFACE=eth$IF_COUNTER
                if ! [ -e /sys/class/net/$NEW_INTERFACE ]; then
                        echo "Assigning new adaptor $MAC to interface $NEW_INTERFACE"
                        nameif "$NEW_INTERFACE" "$MAC"
                        break;
                fi
                IF_COUNTER=$(( IF_COUNTER+1 ))
        done
done