#!/bin/sh


cd /var/log/ntpstats || exit 1

LOCKF=reset_ntp.lock

ntpdrift_good=`sed 's/\.//' </var/lib/ntp/ntp.drift.good`
ntpdrift_agood=$ntpdrift_good
[[ $ntpdrift_agood -lt 0 ]] && ntpdrift_agood=$((-ntpdrift_agood))

force=0
min_ddiff=""
verbose=0
while [[ $# -gt 0 ]]
do
    if [[ "$1" == "-f" ]]
    then
	force=1
	shift
    elif [[ "$1" == "-m" && $# -gt 1 ]]
    then
	min_ddiff=$2
	min_plloff=$((min_ddiff / 25))
	[[ $verbose -gt 0 ]] && echo "min_ddiff: $min_ddiff  min_plloff: $min_plloff ($min_ddiff / 25)"
	shift 2
    elif [[ "$1" == "-v" ]]
    then
	verbose=$((verbose + 1))
	[[ $verbose -gt 1 ]] && set -x
	shift
    else
	echo "Usage: `basename $0` [-v] [-f] [-m <min_ddiff>]" 1>&2
	exit 1
    fi
done

if [[ "$min_ddiff" == "" ]]
then
    min_ddiff=$((ntpdrift_agood / 400 + 500 ))
    min_plloff=25
    [[ $verbose -gt 0 ]] && echo "min_ddiff: $min_ddiff  ($ntpdrift_agood / 400 + 500)  min_plloff: $min_plloff"
fi


# find the ntp hosts that we can get time from
. /etc/default/ntpdate
if [[ -z "$NTPSERVERS" ]]
then
    exit 0
elif [[ $verbose -gt 0 ]]
then
    echo "ntp servers: $NTPSERVERS"
fi



# if we are not connected to the net, we can't check the time
LOC=`/usr/local/sbin/laptop_state`

if [[ "$LOC" == "ROAM" ]]
then
    [[ $verbose -gt 0 ]] && echo "Not connected to the net (ROAM)"
    exit
fi


# not exactly the most secure locking system, but...
find . -name "$LOCKF" -mmin +30 -exec rm '{}' \;

if [[ -f $LOCKF ]]
then
    echo "`basename $0` is already running." 1>&2
    exit 1
fi
touch $LOCKF
trap "rm -f $LOCKF" 0 1 2 3 15
#trap "echo \`date +'%D %T'\` \$SECONDS >>reset_times.log; rm -f $LOCKF" 0



# sometimes when you reset the clock, ntp gets off to a bad start with 
# a very large difference in the drift.  We may have to reset it several times.
num_check=0
while [[ $num_check -lt 4 ]]
do
    num_check=$((num_check + 1))

    if [[ $num_check -gt 1 ]]
    then
	# wait for the ntp daemon to get some useful data
	sleep 64 &
	spid=$!
	if [[ $verbose -gt 0 ]]
	then
	    ntp-wait -v
	else
	    ntp-wait
	fi
	wait $spid
    fi

    # figure out how far the current drift is from the known good value
    ntpdrift=`ntpq -c rv 2>/dev/null | sed -n '/frequency/ { s/.*frequency=\(-*[0-9]*\)\.\([0-9]*\),* *.*/\1\2/; p }'`

    ntpdrift_diff=$((ntpdrift - ntpdrift_good))
    [[ $ntpdrift_diff -lt 0 ]] && ntpdrift_diff=$(( -ntpdrift_diff ))

    ntperr=`ntpdc -c kerninfo | grep "^estimated error" | sed -e "s/^.*  *\([0-9]*\)\.\([0-9][0-9][0-9]\)[0-9]* s$/\1\2/" -e "s/^\(-*\)0*\([0-9]\)/\1\2/" -e "s/^.*  *[.0-9]*e-[0-9][0-9] s$/0/"`

    ntpplloff=`ntpdc -c kerninfo | grep "^pll offset:" | sed -e "s/^.*  *\(-*[0-9]*\)\.\([0-9][0-9][0-9]\)[0-9]* s$/\1\2/" -e "s/^.*  *0 s$/0/" -e "s/^\(-*\)0*\([0-9]\)/\1\2/" -e "s/^.*  *-*[.0-9]*e-[0-9][0-9] s$/0/"`
    ntpplloffa=$ntpplloff
    [[ $ntpplloffa -lt 0 ]] && ntpplloffa=$(( -ntpplloffa ))

    ntpoffset=`ntpq -c rv 2>/dev/null | sed -n -e '/offset/ { s/.*offset=\(-*[0-9]*\)\.\([0-9]*\),* .*/\1\2/; p }' | sed -e "s/^\(-*\)0*\([0-9]\)/\1\2/"`


    # see how far we have drifted since the last time we did an ntpdate
    if [[ -r last_ntpdate ]]
    then
	read <last_ntpdate prev_epoch prev_plloff prev_ddrift
	epoch=`date +%s`
        ntpdate_delta=$(( (epoch - prev_epoch) / 2 + (ntpplloff - prev_plloff)**2 * 100 + (ntpdrift_diff - prev_ddrift)**2 / 1000 ))
        [[ $verbose -gt 0 ]] && echo "($epoch - $prev_epoch) / 2 + ($ntpplloff - $prev_plloff)**2 * 100 + ($ntpdrift_diff - $prev_ddrift)**2 / 1000 = $(((epoch - prev_epoch) / 2)) + $(((ntpplloff - prev_plloff)**2 * 100)) + $(((ntpdrift_diff - prev_ddrift)**2 / 1000)) = $ntpdate_delta"
#        echo "`date +'%D %T'` $epoch - $prev_epoch: $(((epoch - prev_epoch) / 2))   $ntpplloff - $prev_plloff: $(((ntpplloff - prev_plloff)**2 * 100))   $ntpdrift_diff - $prev_ddrift: $(((ntpdrift_diff - prev_ddrift)**2 / 1000))  = $ntpdate_delta" >>ntpdate_delta.log
    else
        ntpdate_delta=999999999
    fi


    # if the current drift is close enough, then don't bother check further
    [[ $verbose -gt 0 ]] && echo "$num_check -eq 1  &&  $force -eq 0  &&  ( $ntpdate_delta -le 10000  ||  (( $ntpdrift_diff -le $min_ddiff  ||  $ntpplloffa -le $min_plloff )  &&  $ntpdrift_diff -le $((min_ddiff * 3)) ))"
    if [[ $num_check -eq 1  &&  $force -eq 0  &&  ( $ntpdate_delta -le 10000  ||  (( $ntpdrift_diff -le $min_ddiff  ||  $ntpplloffa -le $min_plloff )  &&  $ntpdrift_diff -le $((min_ddiff * 3)) ))  ]]
    then
	[[ $verbose -gt 0 ]] && echo "Quick check exit:  ntpdrift_diff: $ntpdrift_diff  est error: $ntperr  pll offset: $ntpplloff  rv offset: $ntpoffset  ntpdate_delta: $ntpdate_delta"
#	echo "checking ntpd:  `date +'%D %T'`  drift: $ntpdrift_diff  (quick exit)  pll offset: $ntpplloff  delta: $ntpdate_delta" >>est_error.log
	exit 0
    fi


    # get the current time and see how far off we are.
    ntpout=`ntpdate -q $NTPSERVERS`
    offset=`echo "$ntpout" | grep "\(step\|adjust\) time server" | sed -e "s/.* offset \([0-9.-]*\) sec.*/\1/" | awk '{if ( $0 < 0 ) { print int( $0 * 1000 - .5 ) } else {print int( $0 * 1000 + .5)}}'`
    if [[ "x$offset" == "x" ]]
    then
	[[ $verbose -gt 0 ]] && echo "Could not get offset:  $ntpout"
	exit 0
    fi

    echo >last_ntpdate `date +%s` $ntpplloff $ntpdrift_diff

    # make sure that abnormal delays don't fool us
    time_check=0
    while [[ $time_check -lt 4 ]]
    do
	sleep $(( time_check * 3 + 2 ))
	ntpout=`ntpdate -q $NTPSERVERS`
	offset2=`echo "$ntpout" | grep "\(step\|adjust\) time server" | sed -e "s/.* offset \([0-9.-]*\) sec.*/\1/" | awk '{if ( $0 < 0 ) { print int( $0 * 1000 - .5 ) } else {print int( $0 * 1000 + .5)}}'`
	if [[ "x$offset2" == "x" ]]
	then
	    [[ $verbose -gt 0 ]] && echo "Could not get offset:  $ntpout"
	    sleep 30
	    offset2=$(( offset + 999 ))
	fi

	delta=$(( offset - offset2 ))
	if [[ $delta -lt 16 && $delta -gt -16 ]]
	then
	    break
	fi

	[[ $verbose -gt 0 ]] && echo "unstable time returned from ntpdate.  offsets: ( $offset - $offset2 ) = $delta"
	offset=$offset2
	time_check=$((time_check + 1))
    done

    if [[ $time_check -ge 4 ]]
    then
	echo "Error:  Could not get ntpdate to return a stable time." 1>&2
	exit 1
    fi

    # calculate the maximum allowable offset
    ntppoll=`ntpq -c rv 2>/dev/null | sed -n '/poll/ { s/.*poll=\([0-9]*\),.*/\1/; p }'`
    max_ddiff=$(((ntppoll * ntpdrift_agood) / 150 + 1500 ))
    [[ $verbose -gt 0 ]] && echo "max_ddiff: $max_ddiff  ($ntppoll * $ntpdrift_agood / 150 + 1500)"


    echo "checking ntpd:  `date +'%D %T'`  drift: $ntpdrift_diff  offset: $offset  pll offset: $ntpplloff  delta: $ntpdate_delta" >>est_error.log
    [[ $verbose -gt 0 ]] && echo "checking ntpd:  `date +'%D %T'`  drift: $ntpdrift_diff  offset: $offset  pll offset: $ntpplloff  delta: $ntpdate_delta"

    # restart the ntp server, if needed
    if [[ $time_check -lt 4 && ( $offset -ge 75  ||  $offset -le -75  ||  $ntpdrift_diff -gt $max_ddiff  ||  $force -eq 1 ) ]]
    then

	echo "Resetting time:  $offset ms ($time_check)  `date +'%D %T'`  $((`TZ=GMT date '+((%H * 60) + %M) * 60 + %S' | sed 's/0\([1-9]\)/\1/g'`))"
	echo "drift good: $ntpdrift_good  current: $ntpdrift  diff:  $ntpdrift_diff"


	/etc/init.d/ntp-server stop | grep -v "Stopping NTP server: ntpd."
	bad_ntp=`ps auwx | grep ntpd | grep -v grep`
	if [[ "$bad_ntp" != "" ]]
	then
	    echo "kill the outstanding ntp process"
	    echo "$bad_ntp"
	fi

	touch $LOCKF

	if ! cmp --quiet /var/lib/ntp/ntp.drift.good /var/lib/ntp/ntp.drift
	then
	    echo "replacing ntp drift info `cat /var/lib/ntp/ntp.drift` with `cat /var/lib/ntp/ntp.drift.good`"
	    cp -a /var/lib/ntp/ntp.drift.good /var/lib/ntp/ntp.drift
	fi

	/etc/init.d/ntp-server start | grep -v "Starting NTP server: ntpd."
	sleep 2

	echo

    else
	if [[ $verbose -gt 0 ]]
	then
	    echo "*NOT* Resetting time:  $offset ms ($time_check)  `date +'%D %T'`  $((`TZ=GMT date '+((%H * 60) + %M) * 60 + %S' | sed 's/0\([1-9]\)/\1/g'`))"
	    echo "drift good: $ntpdrift_good  current: $ntpdrift  diff:  $ntpdrift_diff"
	fi

	if [[ $num_check -eq 1 ]]
	then
	    exit 0
	fi

	touch $LOCKF
    fi
    force=0
done