lib/utils: packet recycling (keeps header, doesn’t free memory)

daemon/bindings/kres.c

@@ -150,14 +150,9 @@ static int pkt_question(lua_State *L)
 	uint8_t dname[KNOT_DNAME_MAXLEN];
 	knot_dname_from_str(dname, lua_tostring(L, 2), sizeof(dname));
 	if (!knot_dname_is_equal(knot_pkt_qname(pkt), dname)) {
-		uint8_t header[KNOT_WIRE_HEADER_SIZE];
-		memcpy(header, pkt->wire, sizeof(header));
-		knot_pkt_clear(pkt);
-		memcpy(pkt->wire, header, sizeof(header));
-		size_t max_size = pkt->max_size;
+		KR_PKT_RECYCLE(pkt);
 		knot_pkt_put_question(pkt, dname, lua_tointeger(L, 3), lua_tointeger(L, 4));
 		pkt->parsed = pkt->size;
-		pkt->max_size = max_size;
 	}
 	return 0;
 }

lib/layer/rrcache.c

@@ -46,10 +46,7 @@ static int loot_rr(struct kr_cache_txn *txn, knot_pkt_t *pkt, const knot_dname_t
 
 	/* Update packet question */
 	if (!knot_dname_is_equal(knot_pkt_qname(pkt), name)) {
-		uint8_t header[KNOT_WIRE_HEADER_SIZE];
-		memcpy(header, pkt->wire, sizeof(header));
-		knot_pkt_clear(pkt);
-		memcpy(pkt->wire, header, sizeof(header));
+		KR_PKT_RECYCLE(pkt);
 		knot_pkt_put_question(pkt, qry->sname, qry->sclass, qry->stype);
 	}
 

lib/utils.h

@@ -34,6 +34,12 @@ extern void _cleanup_fclose(FILE **p);
  * Defines.
  */
 
+/** @internal Fast packet reset. */
+#define KR_PKT_RECYCLE(pkt) do { \
+	(pkt)->parsed = (pkt)->size = KNOT_WIRE_HEADER_SIZE; \
+	knot_pkt_parse_question((pkt)); \
+} while (0)
+
 /** Concatenate N strings. */
 char* kr_strcatdup(unsigned n, ...);