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#!/bin/bash
# This script configures running chronyd to use NTP servers obtained from
# DHCP and _ntp._udp DNS SRV records. Files with servers from DHCP are managed
# externally (e.g. by a dhclient script). Files with servers from DNS SRV
# records are updated here using the dig utility. The script can also list
# and set static sources in the chronyd configuration file.
chronyc=/usr/bin/chronyc
chrony_conf=/etc/chrony.conf
chrony_service=chronyd.service
helper_dir=/var/run/chrony-helper
added_servers_file=$helper_dir/added_servers
network_sysconfig_file=/etc/sysconfig/network
dhclient_servers_files=/var/lib/dhclient/chrony.servers.*
dnssrv_servers_files=$helper_dir/dnssrv@*
dnssrv_timer_prefix=chrony-dnssrv@
chrony_command() {
$chronyc -a -n -m "$1"
}
is_running() {
chrony_command "tracking" &> /dev/null
}
is_update_needed() {
for file in $dhclient_servers_files $dnssrv_servers_files \
$added_servers_file; do
[ -e "$file" ] && return 0
done
return 1
}
update_daemon() {
local all_servers_with_args all_servers added_servers
if ! is_running; then
rm -f $added_servers_file
return 0
fi
all_servers_with_args=$(
cat $dhclient_servers_files $dnssrv_servers_files 2> /dev/null)
all_servers=$(
echo "$all_servers_with_args" |
while read server serverargs; do
echo "$server"
done | sort -u)
added_servers=$( (
cat $added_servers_file 2> /dev/null
echo "$all_servers_with_args" |
while read server serverargs; do
[ -z "$server" ] && continue
chrony_command "add server $server $serverargs" &> /dev/null &&
echo "$server"
done) | sort -u)
comm -23 <(echo -n "$added_servers") <(echo -n "$all_servers") |
while read server; do
chrony_command "delete $server" &> /dev/null
done
added_servers=$(comm -12 <(echo -n "$added_servers") <(echo -n "$all_servers"))
[ -n "$added_servers" ] && echo "$added_servers" > $added_servers_file ||
rm -f $added_servers_file
}
get_dnssrv_servers() {
local name=$1
if ! command -v dig &> /dev/null; then
echo "Missing dig (DNS lookup utility)" >&2
return 1
fi
(
. $network_sysconfig_file &> /dev/null
output=$(dig "$name" srv +short +ndots=2 +search 2> /dev/null)
[ $? -ne 0 ] && return 0
echo "$output" | while read prio weight port target; do
server=${target%.}
[ -z "$server" ] && continue
echo "$server port $port ${NTPSERVERARGS:-iburst}"
done
)
}
check_dnssrv_name() {
local name=$1
if [ -z "$name" ]; then
echo "No DNS SRV name specified" >&2
return 1
fi
if [ "${name:0:9}" != _ntp._udp ]; then
echo "DNS SRV name $name doesn't start with _ntp._udp" >&2
return 1
fi
}
update_dnssrv_servers() {
local name=$1
local srv_file=$helper_dir/dnssrv@$name servers
check_dnssrv_name "$name" || return 1
servers=$(get_dnssrv_servers "$name")
[ -n "$servers" ] && echo "$servers" > "$srv_file" || rm -f "$srv_file"
}
set_dnssrv_timer() {
local state=$1 name=$2
local srv_file=$helper_dir/dnssrv@$name servers
local timer=$dnssrv_timer_prefix$(systemd-escape "$name").timer
check_dnssrv_name "$name" || return 1
if [ "$state" = enable ]; then
systemctl enable "$timer"
systemctl start "$timer"
elif [ "$state" = disable ]; then
systemctl stop "$timer"
systemctl disable "$timer"
rm -f "$srv_file"
fi
}
list_dnssrv_timers() {
systemctl --all --full -t timer list-units | grep "^$dnssrv_timer_prefix" | \
sed "s|^$dnssrv_timer_prefix\(.*\)\.timer.*|\1|" |
while read -r name; do
systemd-escape --unescape "$name"
done
}
prepare_helper_dir() {
mkdir -p $helper_dir
exec 100> $helper_dir/lock
if ! flock -w 20 100; then
echo "Failed to lock $helper_dir" >&2
return 1
fi
}
is_source_line() {
local pattern="^[ \t]*(server|pool|peer|refclock)[ \t]+[^ \t]+"
[[ "$1" =~ $pattern ]]
}
list_static_sources() {
while read line; do
is_source_line "$line" && echo "$line" || :
done < $chrony_conf
}
set_static_sources() {
local new_config tmp_conf
new_config=$(
sources=$(
while read line; do
is_source_line "$line" && echo "$line"
done)
while read line; do
if ! is_source_line "$line"; then
echo "$line"
continue
fi
tmp_sources=$(
local removed=0
echo "$sources" | while read line2; do
[ "$removed" -ne 0 -o "$line" != "$line2" ] && \
echo "$line2" || removed=1
done)
[ "$sources" == "$tmp_sources" ] && continue
sources=$tmp_sources
echo "$line"
done < $chrony_conf
echo "$sources"
)
tmp_conf=${chrony_conf}.tmp
cp -a $chrony_conf $tmp_conf &&
echo "$new_config" > $tmp_conf &&
mv $tmp_conf $chrony_conf || return 1
systemctl try-restart $chrony_service
}
print_help() {
echo "Usage: $0 COMMAND"
echo
echo "Commands:"
echo " update-daemon"
echo " update-dnssrv-servers NAME"
echo " enable-dnssrv NAME"
echo " disable-dnssrv NAME"
echo " list-dnssrv"
echo " list-static-sources"
echo " set-static-sources < sources.list"
echo " is-running"
echo " command CHRONYC-COMMAND"
}
case "$1" in
update-daemon|add-dhclient-servers|remove-dhclient-servers)
is_update_needed || exit 0
prepare_helper_dir && update_daemon
;;
update-dnssrv-servers)
prepare_helper_dir && update_dnssrv_servers "$2" && update_daemon
;;
enable-dnssrv)
set_dnssrv_timer enable "$2"
;;
disable-dnssrv)
set_dnssrv_timer disable "$2" && prepare_helper_dir && update_daemon
;;
list-dnssrv)
list_dnssrv_timers
;;
list-static-sources)
list_static_sources
;;
set-static-sources)
set_static_sources
;;
is-running)
is_running
;;
command|forced-command)
chrony_command "$2"
;;
*)
print_help
exit 2
esac
exit $?
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