#!/bin/sh
#
#       @(#) generate-rfc4193-addr.sh (ULA)  (c) Sep 2004 - Jun 2011    Holger Zuleger
#
#       do what the name suggest
#
#       firstpart = 64-Bit NTP time
#       secondpart = EUI-64 Identifier or 48 Bit MAC-Adress
#       sha1sum ($firstpart | $secondpart )
#       use least significant 40 Bits of sha1sum
#       build global prefix (locally assigned == FD00::/8)
#
#       (M1) 11. May 2006
#       - a check added to complain if firstpart or secondpart is empty
#       - firstpart calculation changed in such a way, that only one transmit
#         time is stored (ntpdate since version 4.2.0 use a list of ntp servers)
#
#       (M2) 27. Aug 2006
#       Fixed bug in using reference time instead of transmit timestamp.
#       Thanks to Marc A. Donges for finding this out
#
#       (M3) 4. Sep 2006
#       Use ntpq instead of ntpdate because the latter is deprecated.
#       This requires a local running and syncronized ntpd, but
#       speeds up the execution time
#
#       (M4) 29. Dec 2006
#       set LC_ALL=C at the beginning of the script, to be sure the grep command
#       used to scan the output of the ifconfig command finds the expected string
#       Thanks to Ted Percival for finding this out
#
#       (M5) 5. Jun 2011
#       tr command added to remove the trailing newline from the sha1 calculation
#       Thanks to Reinard Max for the fix
#
#       (M6) 26. Aug 2011
#       Modified to work on BSD as well as Linux, and take the interface as $1
#
PATH=/usr/local/bin:/bin:/usr/bin:/usr/sbin:/sbin

debug=0
USE_NTPQ=1
NTPSERVER=pool.ntp.org

test -z $1 && echo "Usage: $0 INTERFACE" && exit 1

#(M4)
LC_ALL=C
export LC_ALL

#(M3)
if test $USE_NTPQ -eq 1
then
        if time=`ntpq -c rv | grep clock=`
        then
                test $debug -eq 1 && echo "$time"
                firstpart=`echo $time | sed  -e "s/clock=//" -e "s/ .*//" -e "s/\.//"`
        else
                echo "no local ntpd running" 1>&2
                exit 1
        fi
else
        #(M1)
        #(M2)
        firstpart=`ntpdate -d -q $NTPSERVER 2>/dev/null | sed "/transmit timestamp/q" |
                sed  -n "/transmit time/s/^transmit timestamp: *\([^ ]*\) .*/\1/p" |
                tr -d "."`
fi

secondpart=`ifconfig $1 |
        egrep "inet6 (addr: )?fe80" |
        sed -n "s/^.*fe80::\([0-9a-f\:]*\).*/\1/p" |
        tr -d ":"`

#(M1)
if test -z "$firstpart" -o -z "$secondpart"
then
        echo "$0: installation error: check if ntpdate and ifconfig is in search path"
        exit 1
fi

test $debug -eq 1 && echo "Firstpart: $firstpart"
test $debug -eq 1 && echo "Secondpart: $secondpart"
test $debug -eq 1 && echo "123456789o123456789o123456789o123456789o123456789o123456789o"
test $debug -eq 1 && echo ${firstpart}${secondpart} | sha1sum

#(M5)
globalid=`echo ${firstpart}${secondpart} | tr -d "\012" | sha1sum | cut -c31-40`
test $debug -eq 1 && echo $globalid


echo fd${globalid} | sed "s|\(....\)\(....\)\(....\)|\1:\2:\3::/48|"