busybox: sysntpd: option to bind server to iface

NTPD in busybox has option -I to bind server to IFACE.
However, capabilities of the busybox are limited, the -I option cannot be
repeated and only one interface can be effectively specified in it.
This option is currently not configurable via UCI.
The patch adds an interface option to the system config, ntp section.
Also sort options for uci_load_validate alphabetically.

Signed-off-by: Alexey Dobrovolsky <[email protected]>

package/utils/busybox/files/sysntpd

@@ -30,7 +30,12 @@ get_dhcp_ntp_servers() {
 
 validate_ntp_section() {
 	uci_load_validate system timeserver "$1" "$2" \
-		'server:list(host)' 'enabled:bool:1' 'enable_server:bool:0' 'use_dhcp:bool:1' 'dhcp_interface:list(string)'
+		'dhcp_interface:list(string)' \
+		'enable_server:bool:0' \
+		'enabled:bool:1' \
+		'interface:string' \
+		'server:list(host)' \
+		'use_dhcp:bool:1'
 }
 
 start_ntpd_instance() {
@@ -49,7 +54,10 @@ start_ntpd_instance() {
 
 	procd_open_instance
 	procd_set_param command "$PROG" -n -N
-	[ "$enable_server" = "1" ] && procd_append_param command -l
+	if [ "$enable_server" = "1" ]; then
+		procd_append_param command -l
+		[ -n "$interface" ] && procd_append_param command -I $interface
+	fi
 	[ -x "$HOTPLUG_SCRIPT" ] && procd_append_param command -S "$HOTPLUG_SCRIPT"
 	for peer in $server; do
 		procd_append_param command -p $peer