Additonal data for MX queries handling.

Added zdb_adjust_mx() for searching and saving A/AAAA RRSets
  corresponding to MX records in a node.
Added ns_put_additional() for adding additional RRSets into the
  response. Currently supports only MX.
Bugfix in skip_first() - was returning head instead of the first
  real item.

src/other/skip-list.c

@@ -321,7 +321,7 @@ int skip_empty( const skip_list *list )
 
 const skip_node *skip_first( const skip_list *list )
 {
-	return list->head;
+	return list->head->forward[0];
 }
 
 /*----------------------------------------------------------------------------*/

src/server/name-server.c

@@ -180,6 +180,39 @@ static inline void ns_put_answer( const zn_node *node, ldns_rr_type type,
 
 /*----------------------------------------------------------------------------*/
 
+void ns_put_additional( const zn_node *node, ldns_rr_type type,
+						ldns_pkt *response )
+{
+	debug_ns("ADDITIONAL SECTION PROCESSING\n");
+	switch (type) {
+	case LDNS_RR_TYPE_MX: {
+		skip_list *mx_refs = zn_get_ref_mx(node);
+		if (mx_refs != NULL) {
+			debug_ns("Adding RRSets for MX\n");
+			// simply add all RRSets to the additional section
+			const skip_node *mx = skip_first(mx_refs);
+			while (mx != NULL) {
+				zn_ar_rrsets *rrsets = (zn_ar_rrsets *)mx->value;
+				if (rrsets != NULL) {
+					ldns_pkt_push_rr_list(response, LDNS_SECTION_ADDITIONAL,
+										  rrsets->a);
+					ldns_pkt_push_rr_list(response, LDNS_SECTION_ADDITIONAL,
+										  rrsets->aaaa);
+				}
+				mx = skip_next(mx);
+			}
+		}
+		break; }
+	case LDNS_RR_TYPE_NS:
+		log_error("Putting additional records for NS not implemented yet!\n");
+		break;
+	default:
+		return;
+	}
+}
+
+/*----------------------------------------------------------------------------*/
+
 static inline void ns_put_authority_ns( const zdb_zone *zone, ldns_pkt *resp )
 {
 	ns_put_rrset(zone->apex, LDNS_RR_TYPE_NS, LDNS_SECTION_AUTHORITY, resp);
@@ -257,6 +290,7 @@ void ns_answer( zdb_database *zdb, const ldns_rr *question, ldns_pkt *response )
 		//assert(ldns_dname_compare(node->owner, qname) == 0);
 		ns_put_answer(node, ldns_rr_get_type(question), response);
 		ns_put_authority_ns(zone, response);
+		ns_put_additional(node, ldns_rr_get_type(question), response);
 	} else {	// only part of QNAME found
 		// if we ended in the zone apex, the name is not in the zone
 		if (zone->apex == node) {

src/zone/zone-database.c

@@ -209,6 +209,50 @@ void zdb_adjust_cname( zdb_zone *zone, zn_node *node )
 	}
 }
 
+/*----------------------------------------------------------------------------*/
+
+void zdb_adjust_mx( zdb_zone *zone, zn_node *node )
+{
+	ldns_rr_list *mx_rrset = zn_find_rrset(node, LDNS_RR_TYPE_MX);
+	if (mx_rrset != NULL) {
+		// for each MX RR find the appropriate node in the zone (if any)
+		// and save a reference to it in the zone node
+		debug_zdb("Found MX, searching for corresponding A/AAAA records...\n");
+		int count = ldns_rr_list_rr_count(mx_rrset);
+		for (int i = 0; i < count; ++i) {
+			ldns_rdf *mx = ldns_rr_mx_exchange(ldns_rr_list_rr(mx_rrset, i));
+			assert(mx != NULL);
+			debug_zdb("Searching for A/AAAA record for MX name %s.\n",
+					  ldns_rdf2str(mx));
+			zn_node *mx_node = zdb_find_name_in_list(zone, mx);
+			if (mx_node != NULL) {
+				debug_zdb("Found node: %p\n", mx_node);
+				ldns_rr_list *rrset = zn_find_rrset(mx_node, LDNS_RR_TYPE_A);
+				if (rrset != NULL) {
+					debug_zdb("Found A RRSet within the node, saving.\n");
+					if (zn_add_ref_mx(node, rrset) != 0) {
+						log_error("Error occured while saving A RRSet for MX"
+								  "record in node %s\n",
+								  ldns_rdf2str(node->owner));
+						return;
+					}
+				}
+				rrset = zn_find_rrset(mx_node, LDNS_RR_TYPE_AAAA);
+				if (rrset != NULL) {
+					debug_zdb("Found AAAA RRSet within the node, saving.\n");
+					if (zn_add_ref_mx(node, rrset) != 0) {
+						log_error("Error occured while saving AAAA RRSet for MX"
+								  "record in node %s\n",
+								  ldns_rdf2str(node->owner));
+						return;
+					}
+				}
+				debug_zdb("Done.\n\n");
+			}
+		}
+	}
+}
+
 /*----------------------------------------------------------------------------*/
 /*!
  * @retval 0 if found, -1 or 1 if not found.
@@ -503,10 +547,13 @@ int zdb_adjust_zone( zdb_zone *zone )
 			  ldns_rdf2str(zone->zone_name));
 	// walk through the nodes in the list and check for delegations and CNAMEs
 	zn_node *node = zone->apex;
+	zdb_adjust_mx(zone, node);
+
 	while (node->next != zone->apex) {
 		node = node->next;
 		zdb_adjust_cname(zone, node);
 		zdb_adjust_delegation_point(&node);
+		zdb_adjust_mx(zone, node);
 	}
 
 	debug_zdb("\nDone.\n");

src/zone/zone-node.c

@@ -384,20 +384,29 @@ int zn_add_ref_mx( zn_node *node, ldns_rr_list *ref_rrset )
 
 	if (node->ref.mx == NULL) {
 		node->ref.mx = skip_create_list(zn_compare_ar_keys);
+		if (node->ref.mx == NULL) {
+			return -2;
+		}
 		zn_flags_set(&node->flags, FLAGS_HAS_MX);
 	}
 
 	zn_ar_rrsets *ar = zn_create_ar_rrsets_for_ref(ref_rrset);
 	if (ar == NULL) {
-		return -2;
+		return -3;
 	}
 
 	int res = 0;
 	res = skip_insert(node->ref.mx, ldns_rr_list_owner(ref_rrset), ar,
 					  zn_merge_ar_values);
+
+	debug_zn("zn_add_ref_mx(%p, %p)\n", node, ref_rrset);
+	debug_zn("First item in the skip list: key: %s, value: %p\n",
+		   ldns_rdf2str((ldns_rdf *)skip_first(node->ref.mx)->key),
+		   skip_first(node->ref.mx)->value);
+
 	if (res < 0) {
 		free(ar);
-		return -3;
+		return -4;
 	}
 
 	return 0;