#!/bin/sh
#
# @(#) generate-rfc4193-addr.sh
#
# (c) Sep 2004 - Nov 2005 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
# - check added, to complain if firstpart or secondpart is empty
# - firstpart calculation changed in such a way, that only one reference
#   time is stored (ntpdate since version 4.2.0 use a list of ntp servers)
# 
PATH=/usr/local/bin:/bin:/usr/bin:/usr/sbin:/sbin

debug=0
NTPSERVER=pool.ntp.org

#(M1)
firstpart=`ntpdate -d -q $NTPSERVER 2>/dev/null | sed "/reference/q" |
  sed  -n "/reference/s/^reference time: *\([^ ]*\) .*/\1/p" |
  tr -d "."`

secondpart=`ifconfig eth0 |
  grep "inet6 addr: fe80" |
  sed  -n "s|^.*::\([^/]*\)/.*|\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

globalid=`echo ${firstpart}${secondpart} | sha1sum | cut -c31-40`
test $debug -eq 1 && echo $globalid


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