Detect duplicate ports

bind8/lang/en

@@ -557,6 +557,7 @@ net_topol=Nameserver choice topology
 net_recur=Allow recursive queries from
 net_err=Failed to save address and topology options
 net_eport='$1' is not a valid port number
+net_eusedport=Only one line of addresses is allowed for port $1
 net_etopology=No topology addresses entered
 net_erecur=No addresses to allow recursion from entered
 

bind8/save_net.cgi

@@ -20,6 +20,8 @@ if (!$in{'listen_def'}) {
 				&error(&text('net_eport', $in{"port_$i"}));
 			$l->{'values'} = [ 'port', $in{"port_$i"} ];
 			}
+		$port = $in{"pdef_$i"} ? 53 : $in{"port_$i"};
+		$used{$port}++ && &error(&text('net_eusedport', $port));
 		$l->{'members'} =
 			[ map { { 'name' => $_ } } split(/\s+/, $addr) ];
 		push(@listen, $l);