kdig: print RCODE if failed transfer

src/utils/kdig/kdig_exec.c

@@ -868,6 +868,23 @@ static int process_xfr_packet(const knot_pkt_t      *query,
 				}
 			}
 
+			// Check for error reply.
+			uint16_t rcode = knot_pkt_get_ext_rcode(reply);
+			if (rcode != KNOT_RCODE_NOERROR) {
+				const char *rcode_str = "Unknown";
+
+				const knot_lookup_t *code =
+					knot_lookup_by_id(knot_rcode_names, rcode);
+				if (code != NULL) {
+					rcode_str = code->name;
+				}
+
+				ERR("server replied %s\n", rcode_str);
+				knot_pkt_free(&reply);
+				net_close(net);
+				return 0;
+			}
+
 			// Read first SOA serial.
 			serial = first_serial_check(reply);