unbound: improve robustness with dhcp scripts

When for example 'package/net/adblock' and DNSSEC vs NTP robustness
is enabled, significant restart thrashing can occur at boot up. DHCP
lease triggers may be occuring at the same time. Unbounds DNS-DHCP
may be incomplete until new DHCP solicit events. Solve this by
leaving a passive but complete host conf file during lease trigger.

Signed-off-by: Eric Luehrsen <ericluehrsen@hotmail.com>

net/unbound/files/unbound.sh

@@ -64,6 +64,7 @@ UNBOUND_PIDFILE=/var/run/unbound.pid
 
 UNBOUND_SRV_CONF=$UNBOUND_VARDIR/unbound_srv.conf
 UNBOUND_EXT_CONF=$UNBOUND_VARDIR/unbound_ext.conf
+UNBOUND_DHCP_CONF=$UNBOUND_VARDIR/unbound_dhcp.conf
 UNBOUND_CONFFILE=$UNBOUND_VARDIR/unbound.conf
 
 UNBOUND_KEYFILE=$UNBOUND_VARDIR/root.key
@@ -709,6 +710,16 @@ unbound_hostname() {
       config_load dhcp
       config_foreach create_interface_dns dhcp
     fi
+
+
+    if [ -f "$UNBOUND_DHCP_CONF" ] ; then
+      {
+        # Seed DHCP records because dhcp scripts trigger externally
+        # Incremental Unbound restarts may drop unbound-control add records
+        echo "  include: $UNBOUND_DHCP_CONF"
+        echo
+      } >> $UNBOUND_CONFFILE
+    fi
   fi
 }