Sync the clock and check connectivity faster

buildroot-external/rootfs-overlay/etc/NetworkManager/NetworkManager.conf

@@ -9,3 +9,14 @@ unmanaged-devices=type:bridge;type:tun;type:veth
 
 [logging]
 backend=journal
+
+[connection]
+connection.mdns=2
+connection.llmnr=2
+
+[connectivity]
+uri=http://nmcheck.gnome.org/check_network_status.txt
+interval=300
+
+[device]
+wifi.scan-rand-mac-address=no

buildroot-external/rootfs-overlay/etc/systemd/timesyncd.conf

@@ -1,3 +1,4 @@
 [Time]
-NTP=time.cloudflare.com
+FallbackNTP=time.cloudflare.com
-FallbackNTP=0.pool.ntp.org 1.pool.ntp.org 2.pool.ntp.org 3.pool.ntp.org
+# Speed-up boot as first attempt is done before network is up
+ConnectionRetrySec=10

buildroot-external/rootfs-overlay/usr/lib/NetworkManager/dispatcher.d/10-ntp

@@ -0,0 +1,42 @@
+#!/bin/bash
+#
+
+TIMESYNCD_CONF=/run/systemd/timesyncd.conf.d/10-ntp.conf
+
+timesyncd_dhcp_ntp_remove() {
+  if [ -e $TIMESYNCD_CONF ]; then
+    rm -f $TIMESYNCD_CONF
+    systemctl restart systemd-timesyncd.service
+  fi
+}
+
+timesyncd_dhcp_ntp_add() {
+  mkdir -p "$(dirname $TIMESYNCD_CONF)"
+
+  echo '[Time]' > ${TIMESYNCD_CONF}
+  echo "NTP=${DHCP4_NTP_SERVERS}" >> ${TIMESYNCD_CONF}
+
+  systemctl restart systemd-timesyncd.service
+}
+
+# shellcheck disable=SC2034
+INTERFACE=${1}
+ACTION=${2}
+
+case ${ACTION} in
+  up|down|dhcp4-change)
+    if [ -n "${DHCP4_NTP_SERVERS}" ]
+    then
+      timesyncd_dhcp_ntp_add
+      RETURN_CODE=$?
+    else
+      timesyncd_dhcp_ntp_remove
+      RETURN_CODE=$?
+    fi
+  ;;
+  *)
+    RETURN_CODE=0
+    ;;
+esac
+
+return $RETURN_CODE