chrony: improve hotplug script

- Use the chronyc onoffline command to update state of all sources
  per current routing configuration
- Don't ignore the "ifupdate" action
- Add NTP servers from DHCP for the interface that went up instead of
  the wan4+wan6 interfaces
- Save the servers to files loaded by the sourcedir directive to not
  lose them when chronyd is restarted, and remove them when the
  interface goes down

Signed-off-by: Miroslav Lichvar <mlichvar0@gmail.com>

net/chrony/files/chrony.conf

@@ -1,6 +1,9 @@
 # Load UCI configuration
 confdir /var/etc/chrony.d
 
+# Load NTP servers from DHCP if enabled in UCI
+sourcedir /var/run/chrony-dhcp
+
 # Log clock errors above 0.5 seconds
 logchange 0.5
 

net/chrony/files/chrony.hotplug

@@ -1,20 +1,18 @@
 #!/bin/sh
 # Set chronyd online/offline status, allow NTP access and add servers from DHCP
 
-[ "$ACTION" = ifup -o "$ACTION" = ifdown ] || exit 0
+SOURCEFILE="/var/run/chrony-dhcp/$INTERFACE.sources"
 
 run_command() {
 	/usr/bin/chronyc -n "$*" > /dev/null 2>&1
 }
 
-run_command tracking || exit 0
+run_command onoffline
 
-. /lib/functions/network.sh
-
-network_find_wan iface4
-network_find_wan6 iface6
-run_command $([ -n "$iface4" ] && echo online || echo offline) 0.0.0.0/0.0.0.0
-run_command $([ -n "$iface6" ] && echo online || echo offline) ::/0
+if [ "$ACTION" = ifdown ] && [ -f "$SOURCEFILE" ]; then
+	rm -f "$SOURCEFILE"
+	run_command reload sources
+fi
 
 [ "$ACTION" = ifup ] || exit 0
 
@@ -32,13 +30,16 @@ done
 
 . /usr/share/libubox/jshn.sh
 
-for iface in $iface4 $iface6; do
-	json_load "$(ifstatus $iface)"
-	json_select data
-	json_get_var dhcp_ntp_servers ntpserver
+json_load "$(ifstatus "$INTERFACE")"
+json_select data
+json_get_var dhcp_ntp_servers ntpserver
 
-	for server in $dhcp_ntp_servers; do
-		run_command add $(NTP_SOURCE_HOSTNAME=$server config_foreach \
-				handle_source dhcp_ntp_server server)
-	done
-done
+[ -z "$dhcp_ntp_servers" ] && exit 0
+
+mkdir -p "$(dirname "$SOURCEFILE")"
+
+for NTP_SOURCE_HOSTNAME in $dhcp_ntp_servers; do
+	config_foreach handle_source dhcp_ntp_server server
+done > "$SOURCEFILE"
+
+run_command reload sources