isc-dhcp: fix startup issues with RFC-1918 PTR RRs

If isc-dhcp gets restarted, it might have to deal with RFC-1918 zones
being previously populated by an earlier instance.  In that case, we
need to know if we're modified versus initially adding the zones.

The special handling of RFC-1918 zones in Bind is quirky, and there
should be a patch soon to make it more friendly, but in the meantime
you might have to use:

disable-empty-zone 168.192.in-addr.arpa;

Or similar depending on which address block you poach.

Signed-off-by: Philip Prindeville <philipp@redfish-solutions.com>

net/isc-dhcp/Makefile

@@ -11,7 +11,7 @@ PKG_NAME:=isc-dhcp
 UPSTREAM_NAME:=dhcp
 PKG_REALVERSION:=4.4.3-P1
 PKG_VERSION:=4.4.3_p1
-PKG_RELEASE:=13
+PKG_RELEASE:=14
 
 PKG_LICENSE:=BSD-3-Clause
 PKG_LICENSE_FILES:=LICENSE

net/isc-dhcp/files/dhcpd.init

@@ -154,7 +154,7 @@ EOF
 }
 
 create_empty_zone() {
-	local zone error zpath
+	local zone error zpath command
 	zone="$1"
 	zpath="$dyndir/db.$zone"
 
@@ -167,7 +167,15 @@ create_empty_zone() {
 	chown bind:bind "$zpath" || return 1
 	chmod 0664 "$zpath" || return 1
 
-	if ! error=$(rndc modzone $zone "{
+	# if the zone doesn't exist, we need to add it, otherwise we need to
+	# create it.
+	if ! rndc zonestatus $zone >/dev/null 2>&1; then
+		command="addzone"
+	else
+		command="modzone"
+	fi
+
+	if ! error=$(rndc $command $zone "{
 		type primary;
 		file \"$zpath\";
 		update-policy {