[LEDE-DEV] [PATCH] busybox: sysntpd - Support for NTP servers received via DHCP(v6)

[Hans Dedecker]

The busybox ntpd utility currently uses ntp servers specified in uci.
This patch allows the ntpd utility to use NTP servers received via DHCP(v6)
Following uci parameters have been added:
    use_dhcp : enables NTP server config via DHCP(v6)
    dhcp_interface : use NTP servers received only on the specified DHCP(v6) interfaces; if empty all interfaces are considered

Signed-off-by: Hans Dedecker <dedeckeh at gmail.com>
---

The patch is based on a previous discussion held on the OpenWRT-devel mailing list
(https://lists.openwrt.org/pipermail/openwrt-devel/2016-January/039081.html) as per Felix's
comments this solution is based on procd interface service triggers

 package/utils/busybox/Makefile      |  2 +-
 package/utils/busybox/files/sysntpd | 43 ++++++++++++++++++++++++++++++++-----
 2 files changed, 39 insertions(+), 6 deletions(-)

diff --git a/package/utils/busybox/Makefile b/package/utils/busybox/Makefile
index 24c064c..24e0e11 100644
--- a/package/utils/busybox/Makefile
+++ b/package/utils/busybox/Makefile
@@ -42,7 +42,7 @@ define Package/busybox
   MAINTAINER:=Felix Fietkau <nbd at openwrt.org>
   TITLE:=Core utilities for embedded Linux
   URL:=http://busybox.net/
-  DEPENDS:=+BUSYBOX_USE_LIBRPC:librpc +BUSYBOX_CONFIG_PAM:libpam
+  DEPENDS:=+BUSYBOX_USE_LIBRPC:librpc +BUSYBOX_CONFIG_PAM:libpam +jsonfilter
   MENU:=1
 endef
 
diff --git a/package/utils/busybox/files/sysntpd b/package/utils/busybox/files/sysntpd
index f73bb83..5c663d7 100755
--- a/package/utils/busybox/files/sysntpd
+++ b/package/utils/busybox/files/sysntpd
@@ -7,13 +7,35 @@ USE_PROCD=1
 PROG=/usr/sbin/ntpd
 HOTPLUG_SCRIPT=/usr/sbin/ntpd-hotplug
 
+get_dhcp_ntp_servers() {
+	local interfaces="$1"
+	local filter="*"
+	local network_dump interface ntpservers ntpserver
+
+	network_dump=$(ubus call network.interface dump)
+	for interface in $interfaces; do
+		[ "$filter" = "*" ] && filter="@.interface='$interface'" || filter="$filter, at .interface='$interface'"
+	done
+
+	ntpservers=$(jsonfilter -s "$network_dump" -e "@.interface[$filter]['data']['ntpserver']")
+
+	for ntpserver in $ntpservers; do
+		local duplicate=0
+		local entry
+		for entry in $server; do
+			[ "$ntpserver" = "$entry" ] && duplicate=1
+		done
+		[ "$duplicate" = 0 ] && server="$server $ntpserver"
+	done
+}
+
 validate_ntp_section() {
 	uci_validate_section system timeserver "${1}" \
-		'server:list(host)' 'enabled:bool:1' 'enable_server:bool:0'
+		'server:list(host)' 'enabled:bool:1' 'enable_server:bool:0' 'use_dhcp:bool:0' 'dhcp_interface:list(string)'
 }
 
 start_service() {
-	local server enabled enable_server peer
+	local server enabled enable_server use_dhcp dhcp_interface peer
 
 	validate_ntp_section ntp || {
 		echo "validation failed"
@@ -22,6 +44,8 @@ start_service() {
 
 	[ $enabled = 0 ] && return
 
+	[ $use_dhcp = 1 ] && get_dhcp_ntp_servers "$dhcp_interface"
+
 	[ -z "$server" ] && return
 
 	procd_open_instance
@@ -35,8 +59,17 @@ start_service() {
 	procd_close_instance
 }
 
-service_triggers()
-{
-	procd_add_reload_trigger "system"
+service_triggers() {
+	local script name
+
+	script=$(readlink -f "$initscript")
+	name=$(basename ${script:-$initscript})
+
+	procd_open_trigger
+	procd_add_config_trigger "config.change" "system" /etc/init.d/$name reload
+
+	procd_add_raw_trigger "interface.*" 2000 /etc/init.d/$name reload
+	procd_close_trigger
+
 	procd_add_validation validate_ntp_section
 }
-- 
1.9.1