bugfix: when rrset TTL changed by RR addition, put this change to journal

src/knot/updates/apply.c

@@ -252,16 +252,7 @@ int apply_add_rr(apply_ctx_t *ctx, const knot_rrset_t *rr)
 	// Insert new RR to RRSet, data will be copied.
 	ret = node_add_rrset(node, rr, NULL);
 	if (ret == KNOT_ETTL) {
-		char buff[KNOT_DNAME_TXT_MAXLEN + 1];
-		char *owner = knot_dname_to_str(buff, rr->owner, sizeof(buff));
-		if (owner == NULL) {
-			owner = "";
-		}
-		char type[16] = { '\0' };
-		knot_rrtype_to_string(rr->type, type, sizeof(type));
-		log_zone_notice(contents->apex->owner,
-		                "TTL mismatch, owner %s, type %s, "
-		                "TTL set to %u", owner, type, rr->ttl);
+		// this shall not happen except applying journal created before this bugfix
 		return KNOT_EOK;
 	}
 	return ret;

src/knot/updates/zone-update.c

@@ -387,14 +387,51 @@ void zone_update_clear(zone_update_t *update)
 	memset(update, 0, sizeof(*update));
 }
 
+static int solve_add_different_ttl(zone_update_t *update, const knot_rrset_t *add)
+{
+	const zone_node_t *exist_node = zone_contents_find_node(update->new_cont, add->owner);
+	const knot_rrset_t exist_rr = node_rrset(exist_node, add->type);
+	if (knot_rrset_empty(&exist_rr) || exist_rr.ttl == add->ttl) {
+		return KNOT_EOK;
+	}
+
+	char buff[KNOT_DNAME_TXT_MAXLEN + 1];
+	char *owner = knot_dname_to_str(buff, add->owner, sizeof(buff));
+	if (owner == NULL) {
+		owner = "";
+	}
+	char type[16] = { '\0' };
+	knot_rrtype_to_string(add->type, type, sizeof(type));
+	log_zone_notice(update->zone->name, "TTL mismatch, owner %s, type %s, "
+	                "TTL set to %u", owner, type, add->ttl);
+
+	knot_rrset_t *exist_copy = knot_rrset_copy(&exist_rr, NULL);
+	if (exist_copy == NULL) {
+		return KNOT_ENOMEM;
+	}
+	int ret = zone_update_remove(update, exist_copy);
+	if (ret == KNOT_EOK) {
+		exist_copy->ttl = add->ttl;
+		ret = zone_update_add(update, exist_copy);
+	}
+	knot_rrset_free(exist_copy, NULL);
+	return ret;
+}
+
 int zone_update_add(zone_update_t *update, const knot_rrset_t *rrset)
 {
 	if (update == NULL || rrset == NULL) {
 		return KNOT_EINVAL;
 	}
+	if (knot_rrset_empty(rrset)) {
+		return KNOT_EOK;
+	}
 
 	if (update->flags & (UPDATE_INCREMENTAL | UPDATE_HYBRID)) {
-		int ret = changeset_add_addition(&update->change, rrset, CHANGESET_CHECK);
+		int ret = solve_add_different_ttl(update, rrset);
+		if (ret == KNOT_EOK) {
+			ret = changeset_add_addition(&update->change, rrset, CHANGESET_CHECK);
+		}
 		if (ret == KNOT_EOK && (update->flags & UPDATE_EXTRA_CHSET)) {
 			ret = changeset_add_addition(&update->extra_ch, rrset, CHANGESET_CHECK);
 		}

tests-extra/tests/ixfr/knot_bind_ttl/test.py

+#!/usr/bin/env python3
+
+'''Test for IXFR from Knot to Bind with TTL changed by RR addition'''
+
+from dnstest.test import Test
+
+t = Test()
+
+master = t.server("knot")
+slave = t.server("bind")
+zones = t.zone("example.com.")
+
+t.link(zones, master, slave, ixfr=True)
+
+t.start()
+serials_init = slave.zones_wait(zones)
+
+up = master.update(zones)
+up.add("example.com.", 500, "MX", "20 dns1")
+up.send("NOERROR")
+
+slave.zones_wait(zones, serials_init)
+
+t.xfr_diff(master, slave, zones, serials_init)
+
+t.end()