Better handling of CNAME loop in IXFR-in

refs #1565

src/libknot/util/error.h

@@ -65,7 +65,8 @@ enum knot_error {
 	KNOT_EXFRREFUSED,     /*!< Zone transfer refused by the server. */
 	KNOT_ECONN,           /*!< Connection reset. */
 	KNOT_EIXFRSPACE,      /*!< IXFR reply did not fit in. */
-	KNOT_ERROR_COUNT = 31
+	KNOT_ECNAME,          /*!< CNAME loop found in zone. */
+	KNOT_ERROR_COUNT = 32
 };
 
 /*! \brief Table linking error messages to error codes. */

src/libknot/util/libknot_error.c

@@ -50,5 +50,6 @@ const error_table_t knot_error_msgs[KNOT_ERROR_COUNT] = {
 	{KNOT_TSIG_EBADTIME, "TSIG signing time out of range." },
 	{KNOT_ECONN, "Connection reset."},
 	{KNOT_EIXFRSPACE, "IXFR reply did not fit in."},
+	{KNOT_ECNAME, "CNAME loop found in zone."},
 	{KNOT_ERROR, 0}
 };

src/libknot/zone/zone-contents.c

@@ -972,7 +972,7 @@ static void knot_zone_contents_check_loops_in_tree(knot_zone_tree_node_t *tnode,
 
 	if (cname != NULL) {
 		// this means the node is in the chain already
-		args->err = /*KNOT_ENOIXFR*/KNOT_ERROR;
+		args->err = KNOT_ERROR;
 	}
 
 	cname_chain_free(chain);
@@ -2210,11 +2210,17 @@ int knot_zone_contents_adjust(knot_zone_contents_t *zone)
 	/*
 	 * In second walkthrough check CNAME loops, including wildcards.
 	 */
+	adjust_arg.err = KNOT_EOK;
 	dbg_zone("Checking CNAME and wildcard loops.\n");
 	knot_zone_tree_forward_apply_inorder(zone->nodes,
 	                                 knot_zone_contents_check_loops_in_tree,
 	                                 (void *)&adjust_arg);
 
+	if (adjust_arg.err != KNOT_EOK) {
+		dbg_zone("Found CNAME loop in data. Aborting transfer.\n");
+		return adjust_arg.err;
+	}
+
 	adjust_arg.first_node = NULL;
 	adjust_arg.previous_node = NULL;